World Journal ofOrthopedics

World J Orthop 2020 March 18; 11(3): 145-205

ISSN 2218-5836 (online)

Published by Baishideng Publishing Group Inc

W J O World Journal ofOrthopedics

Contents Monthly Volume 11 Number 3 March 18, 2020

REVIEW145 Distraction arthroplasty in osteoarthritis of the foot and ankle

Dabash S, Buksbaum JR, Fragomen A, Rozbruch SR

ORIGINAL ARTICLE

Observational Study

158 Lumbar interspinous pressure pain threshold values for healthy young men and women and the effect of

prolonged fully flexed lumbar sitting posture: An observational studyPetersson M, Abbott A

167 Observational study of a new modular femoral revision systemDyreborg K, Petersen MM, Balle SS, Kjersgaard AG, Solgaard S

177 Analysis of electrocautery smoke released from the tissues frequently cut in orthopedic surgeriesYeganeh A, Hajializade M, Sabagh AP, Athari B, Jamshidi M, Moghtadaei M

SYSTEMATIC REVIEWS184 Systematic review of the etiology behind patellar clunk syndrome

Sequeira SB, Scott J, Novicoff W, Cui Q

CASE REPORT197 Atraumatic groin pain secondary to an aneurysmal bone cyst: A case report and literature review

Downey C, Daly A, Molloy AP, O’Daly BJ

WJO https://www.wjgnet.com March 18, 2020 Volume 11 Issue 3I

ContentsWorld Journal of Orthopedics

Volume 11 Number 3 March 18, 2020

ABOUT COVER Editorial Board Member of World Journal of Orthopedics, Parisa Azimi, MD,PhD, Assistant Professor, Surgeon, Department of Neurosurgery, ImamHossein Educational Hospital, University of Shahid Beheshti MedicalSciences, Tehran 19839-63113, Iran

AIMS AND SCOPE The primary aim of World Journal of Orthopedics (WJO, World J Orthop) is toprovide scholars and readers from various fields of orthopedics with aplatform to publish high-quality basic and clinical research articles andcommunicate their research findings online. WJO mainly publishes articles reporting research results and findingsobtained in the field of orthopedics and covering a wide range of topicsincluding arthroscopy, bone trauma, bone tumors, hand and foot surgery,joint surgery, orthopedic trauma, osteoarthropathy, osteoporosis, pediatricorthopedics, spinal diseases, spine surgery, and sports medicine.

INDEXING/ABSTRACTING The WJO is now abstracted and indexed in PubMed, PubMed Central, Emerging

Sources Citation Index (Web of Science), Scopus, China National Knowledge

Infrastructure (CNKI), China Science and Technology Journal Database (CSTJ), and

Superstar Journals Database.

RESPONSIBLE EDITORS FORTHIS ISSUE

Responsible Electronic Editor: Yan-Xia Xing

Proofing Production Department Director: Xiang Li

NAME OF JOURNALWorld Journal of Orthopedics

ISSNISSN 2218-5836 (online)

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W J O World Journal ofOrthopedics

Submit a Manuscript: https://www.f6publishing.com World J Orthop 2020 March 18; 11(3): 145-157

DOI: 10.5312/wjo.v11.i3.145 ISSN 2218-5836 (online)

REVIEW

Distraction arthroplasty in osteoarthritis of the foot and ankle

Sherif Dabash, Joshua R Buksbaum, Austin Fragomen, S Robert Rozbruch

ORCID number: Sherif Dabash(0000-0001-8817-6390); Joshua RBuksbaum (0000-0002-7070-9133);Austin Fragomen(0000-0002-9031-9079); S RobertRozbruch (0000-0003-1632-4600).

Author contributions: Dabash Sdesigned the research, performedthe research, wrote the paper;Buksbaum JR performed theresearch and helped in writing thepaper; Fragomen A and RozbruchSR helped in designing theresearch.

Conflict-of-interest statement: Theauthors have no conflict of interestto report.

Open-Access: This article is anopen-access article that wasselected by an in-house editor andfully peer-reviewed by externalreviewers. It is distributed inaccordance with the CreativeCommons AttributionNonCommercial (CC BY-NC 4.0)license, which permits others todistribute, remix, adapt, buildupon this work non-commercially,and license their derivative workson different terms, provided theoriginal work is properly cited andthe use is non-commercial. See:http://creativecommons.org/licenses/by-nc/4.0/

Manuscript source: Invitedmanuscript

Received: October 24, 2019Peer-review started: October 24,2019First decision: December 17, 2019Revised: December 22, 2019Accepted: March 1, 2020Article in press: March 1, 2020Published online: March 18, 2020

Sherif Dabash, Austin Fragomen, S Robert Rozbruch, Limb Lengthening and ComplexReconstruction Service, Weill Cornell Medical College Department of Orthopaedic Surgery,Hospital for Special Surgery New York, NY 10021, United States

Joshua R Buksbaum, SUNY Downstate Health Sciences University, College of Medicine,Brooklyn, New York, NY 11226, United States

Corresponding author: Sherif Dabash, MD, Limb Lengthening and Complex Deformitycorrection Clinical Fellow, Hospital for Special Surgery, 535 East 70th Street, New York, NY10021, United States. dabashs@hss.edu

AbstractPost-traumatic osteoarthritis (PTOA) is a complex and painful problem in thefoot and ankle. Ninety percent of osteoarthritis cases in the foot and ankle can beclassified as post-traumatic. PTOA can affect any of the 33 joints in the foot andthe ankle. Distraction arthroplasty is a method for treatment of early arthriticjoints without fusing or replacing them and its effectiveness has been welldocumented. The purpose of this case series is to present our successfulexperiences and positive results using distraction arthroplasty to treat PTOA inthe ankle, subtalar, first metatarsophalangeal, and second tarsometatarsal joints,and to present distraction arthroplasty as a viable alternative to invasive jointsacrificing procedures such as arthrodesis or arthroplasty. DistractionArthroplasty effectively and safely treats PTOA and improves the stability ofjoints in the Foot and Ankle. Additionally, the use of bone marrow aspirateconcentrate as an adjuvant can improve the long-term functional and structuraloutcomes of the joint, and can prolong the need for further, more aggressivesurgical interventions such as fusion or arthroplasty.

Key words: Distraction arthroplasty; First metatarso-phalangeal joint arthritis; Secondtarsometarsal joint arthritis; Ankle arthritis; Subtalar arthritis; Post-traumatic osteoarthritis

©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.

Core tip: Osteoarthritis is a degenerative condition affecting articular joints causing lossof mobility and independence due to pain and swelling in the affected joint. Ninetypercent of osteoarthritis cases in the foot and ankle can be classified as post-traumaticand can affect any of the 33 joints in the foot and ankle. Distraction arthroplasty is aviable and effective treatment for Post-traumatic osteoarthritis in the foot and anklejoints, which can prolong the integrity of the joints and prevent a joint sacrificingprocedure such as arthrodesis or arthroplasty.

WJO https://www.wjgnet.com March 18, 2020 Volume 11 Issue 3145

P-Reviewer: Cure E, Lee SHS-Editor: Wang JL-Editor: AE-Editor: Liu MY

Citation: Dabash S, Buksbaum JR, Fragomen A, Rozbruch SR. Distraction arthroplasty inosteoarthritis of the foot and ankle. World J Orthop 2020; 11(3): 145-157URL: https://www.wjgnet.com/2218-5836/full/v11/i3/145.htmDOI: https://dx.doi.org/10.5312/wjo.v11.i3.145

INTRODUCTIONOsteoarthritis is a degenerative condition affecting articular joints causing loss ofmobility and independence due to pain and swelling in the affected joint. There are amultitude of causes for the onset of osteoarthritis and treatments for its progressionand symptoms. Post-traumatic osteoarthritis (PTOA) comprises a large portion ofosteoarthritis cases affecting the ankle and foot[1]. The treatment of osteoarthritis in theankle, subtalar, 1st metatarsophalangeal (MTP) joint, or 2nd tarsometatarsal joints(TMT) joint with fusion or arthroplasty have been well documented[1-6]. DistractionArthroplasty was first described as a conservative treatment for arthritis of the hip inyoung patients[7]. Since then, there has been a growth in interest related to this newersurgical technique, and numerous studies have described its application as atreatment for PTOA in the ankle and foot. Distraction arthroplasty can be used to treatPTOA of these joints as a viable joint preservation alternative, especially in youngerpatients who are not candidates for either fusion or arthroplasty[6,8-12].

Unlike the knee, most cases of ankle arthritis are classified as post-traumatic. Anklesprains are one of the most common athletic injuries and can lead to PTOA of theankle, and there are few treatments to delay or reverse the progression of post-traumatic ankle arthritis[13]. In the ankle, or the Tibio-talar joint, fusion andarthroplasty are well documented treatments for PTOA[1,6,14]. In addition to the ankle,PTOA is prevalent in the subtalar joint. Hindfoot fractures of the talus and calcaneuscan lead to persistent pain and the progression of PTOA. In the subtalar, or Talo-calcaneal joint, fusion and arthroplasty are well documented treatments forPTOA[1,12,15]. Osteoarthritis of the 1st MTP joint can often be debilitating, as it bearsapproximately 50% of the body’s weight during ambulation. Osteoarthritis of the 1st

MTP joint can be caused by Hallux Rigidus or Hallux Valgus deformities, in additionto trauma. Fusion and arthroplasty are well documented treatments for PTOA in thefirst MTP joint[2,3,16-19]. The effectiveness of distraction arthroplasty in treating PTOA ofthe 1st MTP has been documented[8]. Osteoarthritis can affect the TMT joints due toseveral causes, including trauma, deformity, and prior foot surgery[4,5,20,21]. PTOA ofthe second TMT joint is often painful and difficult to treat. In the second TMT joint,fusion and arthroplasty are well documented treatments for PTOA[4,5]. Currently, thereare no studies investigating the use of distraction arthroplasty to treat PTOA in thesecond TMT. Distraction Arthroplasty is a viable joint preserving surgery alternativeto fusion and arthroplasty to treat post-traumatic osteoarthritis and is especiallysuitable for younger and active patients[6,8-10,22-26].

CLINICAL PRESENTATION

Patient A: Ankle distraction for posttraumatic arthritisPatient A is a 52-year-old female who presented with left ankle PTOA. Shecomplained of gradual pain developing in her ankle after multiple sprains and wearand tear from an active lifestyle. This pain was treated with a Watson Jones procedure29 years prior, and an ankle distraction with external fixation performed one yearprior, in addition to tarsal tunnel release and arthroscopic cheilectomy. The patientdeveloped an equinus contracture due to her time spent with her ankle immobilizedduring distraction. She was diagnosed with advanced PTOA of the left ankle, inaddition to an equinus contracture. Our decision was to take on a joint-preservationcourse of action, to help the patient continue to enjoy her active lifestyle. Our planincluded arthrotomy and cheilectomy, microfracture, ankle distraction, and bonemarrow aspirate concentrate (BMAC) injection to treat the ankle PTOA, in addition torelease of the gastrocnemius and soleus to correct the equinus contracture.

On physical exam, pre-operative range of motion (ROM) in the left ankle was -10degrees of dorsiflexion (DF) to 40 degrees of plantarflexion (PF). Pre-operative ROMin the left subtalar joint was from 5 degrees of inversion to 5 degrees of eversion. Post-operative ROM n in the left ankle was 5 degrees of DF to 40 degrees of PF, and ROMin the subtalar joint was 10 degrees of inversion to 5 degrees of eversion. After

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surgery, patient continued extremely active lifestyle and did report taking some painmedication to treat pain after activity, however she stated that her pain levels hadbeen significantly reduced through her surgical treatment. Patient is now nine yearsfrom date of distraction arthroplasty frame removal and is doing well with no pain(Figures 1-4).

Patient B: Ankle distraction + correction of flat foot deformity56-year-old female who presented with right ankle PTOA. She complained of pain inher ankle at 5/10 after an inversion injury to her ankle sustained 16 years prior whilerunning. She was diagnosed with an Osteochondritis Dissecans lesion on the medialaspect her talar dome. She also had a flat foot deformity. She was recommended anklefusion by another surgeon, however our decision was to undertake distractionarthroplasty to offload the ankle joint and the Osteochondritis Dissecans lesion, whilesimultaneously placing an arthroeresis screw to treat her flat foot deformity.

On physical exam, pre-operative ROM in the ankle was 0 degrees of DF to 50degrees of (PF). Pre-operative ROM in the subtalar joint was 40 degrees of inversionto 10 degrees of eversion. Pre-operative self-reported pain level was 5/10, and thepatient was taking Tylenol 1000 mg BID and 5 mg of Oxycodone daily for pain.

On physical exam post-operatively, ROM was recorded as 20 degrees of DF to 40degrees of PF in the ankle and subtalar ROM was 20 degrees of inversion to 20degrees of eversion. The patient reported no pain after surgery and did not take anypain medications. Patient is now two years from frame removal and is doing well(Figures 5 and 6).

Patient C: Sub-talar distractionPatient C is a 45-year-old female who presented with PTOA of the right sub-talar jointafter sustaining a fracture and dislocation of the talus. Upon examination, shepresented with pain worsening with increasing activity on the lateral side of the footand a limp due to pain. On physical examination, ROM in the right ankle was 0 DF to70 degrees PF, and ROM in the right sub-talar joint was 20 degrees of inversion and 0degrees eversion. Patient did not see improvement in pain after conservativetreatment with PRP injections. Patient was offered sub-talar fusion or distraction.Because of her age, she elected to proceed with distraction. After surgery, ROM in thesub-talar joint improved to 15 degrees of inversion and 10 degrees of eversion.Additionally, patient reported no pain after surgery and has returned to her normallevel of activity. Patient is now three years post removal of frame and is doing wellwith no pain (Figures 7-11).

Patient D: 1st MTP distractionPatient D is a 48-year-old male who presented to the office with hallux rigidusdeformity of the right first MTP joint. The patient reported pain and difficultywearing normal shoes. Patient did not see improvement with conservative treatmentsof orthotics and injections of the first MTP joint. The patient was presented withmultiple treatment options; fusion, cheilectomy, cartiva, and distraction of the firstMTP joint to treat pain and hallux rigidus. After discussion with the patient, thepatient elected to proceed with cheilectomy and distraction arthroplasty of the firstMTP joint with external fixation. After surgery, the patient reported improvement ofpain and ROM. Patient is now six months post removal of the distraction arthroplastyframe and is doing well with no pain (Figures 12-14).

Patient E: 2nd TMT distractionPatient E is a 66-year-old male who presented with flat foot and dorsal pain in his leftfoot caused by PTOA and synovial cysts in his second (TMT) joint. Patient reportedhis pain levels as ranging from four to six out of ten and taking ibuprofen for pain.Patient was recommended midfoot fusion at the second TMT, but after his satisfactionwith ankle and sub-talar distraction performed by our physicians on the contralaterallimb, he elected to proceed with distraction arthroplasty of the second TMT. Plannedtreatment included distraction of the second TMT, debridement, and BMAC injectionin the second TMT, in addition to insertion of arthroeresis screw and gastrocnemiuslengthening to treat flat foot deformity. After surgery, patient reported no pain anddid not take any medication for pain. Patient is now two years post removal of theframe and is doing well with no pain (Figures 15-18).

SURGICAL TECHNIQUE

Ankle distractionThe ankle distraction frame is simply composed of two rings connected together with

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Figure 1

Figure 1 Pre-operative standing X-rays demonstrating post-traumatic osteoarthritis of the ankle joint. A:Anterior-Posterior view; B: Mortise view; C: Lateral view.

two threaded rods and a locking rod that connects the footplate to the proximaladjustable ring which allows gradual DF. A tibial ring is chosen that gives twofingerbreadths of space circumferentially between the skin and the ring. The proximalring is secured with two 6-mm hydroxyapatite-coated pins. A 4.8-mm drill bit is usedto fix the first pin approximately 6 cm proximal to the medial malleolus directlyanterior in the tibial crest and perpendicular to the shaft of the tibia. Surgeon has toavoid unicortical pins that miss the medullary canal and put the bone at risk offracture. It is then secured to the ring with a three-hole cube. Intraoperativefluoroscopy is used to confirm that the ring is perpendicular to the axis of the tibialshaft. Universal hinges are then applied in line with a K-wire which approximates theInman axis from the tip of the lateral malleolus to the tip of the medial malleolus, in aposterolateral-to-anteromedial direction.

A footplate is secured by olive wires one inch proximal and parallel to the plantaraspect of the foot. A locking rod connects the footplate to the proximal adjustable ring,which allows for gradual DF to correct equinus contractures. Threaded rods connectthe two rings where the square nuts are placed on the proximal part of the rod.Measurement of the length of the threaded rod above the square nut is important toensure that the foot/ankle is back into neutral position after ROM exercises. Acutedistraction of 3 mm is done intraoperatively by turning the square nuts on theproximal ring. Acute distraction beyond that is not recommended to avoid neurologictraction injury; acute correction of equinus contracture is avoided for the same reason.

Another 2 mm of distraction is done on postoperative day one when normalpostoperative plantar sensation is confirmed. Another one mm on postoperative daytwo will be done. During the 2 wk visit, another 1 to 2 mm of distraction is done ifneeded. The total distraction in the frame is about 6-8 mm. The ROM exercises (15repetitions/session) should be done by unlocking the ring four times daily.

In addition to distraction, the senior authors injects BMAC into the ankle joint androutinely do microfracture of the joint. Clinical data regarding the mechanism ofaction of hyaline cartilage regeneration are lacking, however, senior authors feel thatthese adjunctive procedures optimize healing and gives better results[9]. Futureresearch should be directed towards comparing the benefit of adding biologics in theform of BMAC or not.

Sub-talar distractionSub-talar distraction begins with a 4 cm anterior skin incision is made over the lateralhindfoot. Dissection is carried down anterior to the peroneal tendons. The posteriorfacet and sinus tarsi of the joint are visualized. Osteophyte along the lateral talus andcalcaneus are excised. The joint is inspected, and a 1.8 mm wire is used to makemultiple drill holes for microfracture while cooled with saline in the talus and in thetibia. The holes are spaced by 5 mm. Furthermore, a 4 mm micro burr is used toremove a thin layer of hard subchondral bone. The subtalar joint is mobilized from 20degrees of inversion to 15 degrees of eversion. A 3 cm × 3 cm collagen sponge issoaked in BMAC and is inserted into the distracted sub-talar joint.

The ankle distraction frame is then applied. A 155 mm frame and ring are appliedto the distal third of the tibia, orthogonal to the tibial axis, and stabilized with twoanteromedial half pins. The half pins are 6 mm hydroxy appetite coated pins placedafter drilling with a 4.8 mm drill. The two feet rings are attached for fixation to thetalus and calcaneus. Opposing olive wires are placed in the talus and in the calcaneus-4 in total- and are attached to the frame and tensioned. Acute distraction of the sub-

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Figure 2

Figure 2 Post-operative standing X-rays demonstrating distracted ankle joint and distraction frame. A:Anterior-Posterior view; B: Lateral view.

talar joint is then carried out, with 4 mm applied acutely by distracting between thetwo feet rings. The ankle and foot are both assessed for neutral position, anddistraction of the sub-talar joint is confirmed with intra-operative fluoroscopy.

1st MTP distractionFirst MTP joint distraction begins with a 3 cm dorsal skin incision made over the talusneck. Dissection is then carried down to a palpable prominence, and the extensorretinaculum is incised. The superficial peroneal nerve is protected, the tendons areretracted, and the distal surface of the talus is assessed for osteophytes, which are thenexcised. Intra-operative fluoroscopy allows for confirmation of complete removal ofthe osteophyte.

Next, a 4 cm medial skin incision is made across the metatarsophalangeal joint, anddissection is carried down to the medial capsule, which was longitudinally incised.The capsule is peeled off the medial side of the metatarsal head and reflected dorsally.The dorsal surface of the metatarsal head and the proximal phalanx are assessed forosteophytes, which are then excised. Medial eminence is also excised using amicrosagittal saw. The MTP joint is then, subluxated, allowing for inspection of thearticular cartilage. Inspection of the joint showed a 1 cm × 5 mm area of grade 4 fullthickness loss of cartilage on the metatarsal head and an area of 5 mm × 5 mm of fullthickness cartilage loss on the proximal phalanx. A 1.6 mm wire is used to performmicrofracture while cooled with saline.

Fixator is then used to span the first MTP joint from a dorsal approach. A 3 mmself-drilling pin is placed dorsal to plantar in the proximal phalanx. Next, with thehelp of the frame for guidance, a second pin is placed parallel in the axial plane, butperpendicular to the metatarsal. This is also a 3 mm self-drilling pin. These are themost proximal and distal pin and are defined by the orientation of the fixator. The pinclamps are then used to add additional pins in the metatarsal and also in the proximalphalanx. Placement and stability of the pins are confirmed. The fixator is then appliedand fastened. The fixator is placed in line with the axis of the joint in the coronal andsagittal planes. Three point five mm of distraction is then applied across the joint. Theangle between the metatarsal and phalanx is assessed, and was reported to be withinnormal range at 15 degrees of DF. Lastly, intra-operative fluoroscopy is used to guidea spinal needle into the joint and to inject 3 mL of BMAC into the joint.

2nd TMT distractionSecond TMT distraction begins with a two and half cm skin incision over the dorsumof the joint and dissection is carried down to the joint. The joint is exposed,capsulotomy is performed, and the joint is visualized and assessed. Advancedarthrosis was noted of the joint. Using a 1.6 mm wire, microfracture is performed ofthe middle cuneiform and of the second metatarsal part of the joint while cooled withsaline.

A mini rail fixator is then applied with pins coming in at a different plane from theoriginal incision. Using 2.0 mm threaded pins, one pin is inserted into the middlecuneiform; this is the reference pin. This pin is placed orthogonal to the joint in asagittal plane and is well positioned within the middle cuneiform. The mini railexternal fixator is then applied and guides the insertion of a second metatarsal pin,also 2.0 mm. The placement and alignment of the two pins with the foot and fixatorare assessed, and both were determined to be satisfactory. Additional pins are placedin the proximal and distal pin clamps, allowing for excellent purchase. Lastly, the

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Figure 3

Figure 3 One-year post-operative standing X-rays demonstrating improved ankle joint space and articularsurface after distraction. A: Anterior-Posterior view; B: Mortise view; C: Lateral view.

external fixator is then applied to allow for intra-operative distraction. Three mm ofdistraction is placed across the joint and assessed by direct vision.

POST OPERATIVE PERIOD AFTER ANKLE DISTRACTIONThe patient is allowed full weight bear as tolerated with crutches in the postoperativeperiod. The neutral position is marked on the hinge, and the patient is taught how tounlock the hinge and do active assisted ROM exercises with the aid of foot strap. Lateron, the patients are encouraged to ambulate with the frame’s hinge unlocked. Acutedistraction more than 3 mm is not recommended. We usually distract 3 mm in theoperating room, and any residual distraction (2-4 mm) is done by the physician whilethe patient is still in the hospital, or at the first clinic visit 2 wk postoperative. Frame iskept in distraction for 12 wk as there is no added benefit to keep it for longer time.

LIMITATIONSDistraction arthroplasty results in good functional outcomes at medium to long termfollow up. The addition of microfracture seems to create functional outcomedeterioration, whereas the addition of a biologic agent either BMAC or PRP appearsto benefit earlier return to function. Randomized clinical trials with long term followup are needed to compare if microfracture accompanied with the distraction isbeneficial or not.

This case series represents our center experience with this technique. Largermulticenter studies are needed to show the effectiveness of our technique withcomparison to others, and also comparing each surgeon’s preference of addingbiologics in form of BMAC or not and reporting the statistical differences betweendifferent techniques.

CONCLUSIONOur case series aimed to describe the surgical technique of distraction arthroplasty ofdifferent joints in the foot and ankle, and their ability to improve patient outcomes. Itis an alternative procedure to preserve the native joints instead of fusing or replacingthe arthritic joint. Based on our experiences, distraction arthroplasty is a viable andeffective treatment for PTOA in the ankle, subtalar, 1st MTP, and 2nd TMT joint.Distraction arthroplasty can prolong the integrity of the joints of the foot and ankle,and in our experiences, if combined with injection of BMAC can improve theoutcomes of distraction arthroplasty procedure and prolong the time until the patientneeds further surgical intervention, in the form of fusion or arthroplasty.

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Figure 4

Figure 4 Comparison of pre and one-year post-operative standing X-rays demonstrating improved ankle joint space and articular surface after distraction.A: Lateral view, pre-operative; B: Lateral view, one-year post-operation.

Figure 5

Figure 5 pre-operative standing X-rays and magnetic reconnaissance imaging, in addition to intra-operative fluoroscopy of the right ankle after anteriorcheilectomy and distraction. A: Anterior-Posterior (AP) X-rays demonstrates post-traumatic ankle osteoarthritis, joint space narrowing, anterior osteophyte, and flatfoot deformity; B: Mortise view showing the same; C: Lateral view; D: Coronal view of the magnetic reconnaissance imaging shows medial osteochondritis dissecanslesion on the medial talar dome, as indicated by arrow; E: Sagittal view of the magnetic reconnaissance imaging showing medial osteochondritis dissecans lesion onthe medial talar dome, as indicated by arrow; F: Anterior-Posterior intra-operative fluoroscopy of the right ankle after anterior cheilectomy, application of frame anddistraction; G: Ankle in plantarflexion; H: Ankle in dorsiflexion with adjunctive injection of bone marrow aspirate concentrate into the ankle joint.

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Figure 6

Figure 6 One-year post-operative standing X-rays of the right ankle, demonstrating improved ankle joint space, articular cartilage, and joint alignment oneyear after removal of frame. A: Anterior-Posterior view; B: Mortise view; C: Lateral view.

Figure 7

Figure 7 Pre-operative standing X-rays of the right subtalar joint demonstrating sub-talar joint space narrowing and post-traumatic osteoarthritis. A:Anterior-Posterior view; B: Mortise view; C: Lateral view.

Figure 8

Figure 8 Pre-operative computed tomography scans of the right subtalar joint demonstrating sub-talar arthritis and sclerosis of the articular surface. A:Sagittal view; B: Coronal view.

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Figure 9

Figure 9 Intra-operative fluoroscopy of the right sub-talar joint before and after application of intraoperative distraction. A: Lateral view before the distraction;B: Lateral view after 3 mm distraction.

Figure 10

Figure 10 One-month post-operative standing X-rays of the right sub-talar joint distraction, demonstrating widening of sub-talar joint space. A: Anterior-Posterior view; B: Lateral view.

Figure 11

Figure 11 Comparison of pre and one-year post-operative standing X-rays of the right sub-talar joint. A: Lateral view pre-operative standing X-ray; B: Lateralview post-operative standing X-ray one year after frame removal.

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Figure 12

Figure 12 Pre-operative X-rays of the first metatarsophalangeal joint demonstrating hallux rigidus of the first metatarsophalangeal. A: Anterior-Posteriorview; B: Oblique view; C: Lateral view.

Figure 13

Figure 13 Intra-operative fluoroscopy of the right first metatarsophalangeal joint before and after application of external fixator. A: Intra-operativefluoroscopy of the right first metatarsophalangeal (MTP) joint in the anterior-posterior view; B: Intra-operative fluoroscopy of the right first MTP joint in the view afterinsertion of pins; C: Intra-operative fluoroscopy of the right first MTP joint in the AP view after application of monolateral external fixator and injection of bone marrowaspirate concentrate; D: Intra-operative fluoroscopy of the right first MTP joint in lateral view after application of monolateral external fixator and injection of bonemarrow aspirate concentrate. MTP: Metatarsophalangeal.

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Figure 14

Figure 14 Three-month post-operative X-rays of the first metatarsophalangeal joint demonstrating improved metatarsophalangeal joint space. A: Anterior-posterior view; B: Lateral view.

Figure 15

Figure 15 Pre-operative standing X-rays of the left second tarsometatarsal joint, demonstrating joint space narrowing and post-traumatic osteoarthritis inaddition to flat foot deformity. A: Anterior-posterior view; B: Oblique view; C: Lateral view.

Figure 16

Figure 16 Intra-operative fluoroscopy of the left second tarsometatarsal joints demonstrating insertion of arthroeresis screw into the sub-talar joint totreat flat-foot deformity, in addition to application of external fixator. A: Insertion of pins; B: Application of monolateral external fixator.

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Figure 17

Figure 17 Intra-operative fluoroscopy of the left second tarsometatarsal joints joint demonstrating injection of bone marrow aspirate concentrate andapplication of external fixator. A: Lateral view after application of frame; B: Bone marrow aspirate concentrate.

Figure 18

Figure 18 Three-months post-operative X-rays of the left second tarsometatarsal joint, demonstrating improved tarsometatarsal joint space and articularcartilage. A: Anterior-posterior view; B: Oblique view; C: Lateral view.

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Outcomes of Polyvinyl Alcohol Hydrogel Hemiarthroplasty of the First Metatarsophalangeal Joint inAdvanced Hallux Rigidus. Foot Ankle Int 2017; 38: 243-247 [PMID: 27909032 DOI:10.1177/1071100716679979]

3 DeSandis B, Pino A, Levine DS, Roberts M, Deland J, O'Malley M, Elliott A. Functional OutcomesFollowing First Metatarsophalangeal Arthrodesis. Foot Ankle Int 2016; 37: 715-721 [PMID: 27060128DOI: 10.1177/1071100716642286]

4 Jung HG, Myerson MS, Schon LC. Spectrum of operative treatments and clinical outcomes for atraumaticosteoarthritis of the tarsometatarsal joints. Foot Ankle Int 2007; 28: 482-489 [PMID: 17475144 DOI:10.3113/FAI.2007.0482]

5 Raikin SM, Schon LC. Arthrodesis of the fourth and fifth tarsometatarsal joints of the midfoot. Foot AnkleInt 2003; 24: 584-590 [PMID: 12956562 DOI: 10.1177/107110070302400803]

6 Tellisi N, Fragomen AT, Kleinman D, O'Malley MJ, Rozbruch SR. Joint preservation of the osteoarthriticankle using distraction arthroplasty. Foot Ankle Int 2009; 30: 318-325 [PMID: 19356356 DOI:10.3113/FAI.2009.0318]

7 Aldegheri R, Trivella G, Saleh M. Articulated distraction of the hip. Conservative surgery for arthritis inyoung patients. Clin Orthop Relat Res 1994; 301: 94-101 [PMID: 8156703]

8 Abraham JS, Hassani H, Lamm BM. Hinged external fixation distraction for treatment of firstmetatarsophalangeal joint arthritis. J Foot Ankle Surg 2012; 51: 604-612 [PMID: 22749986 DOI:10.1053/j.jfas.2012.04.022]

9 Bernstein M, Reidler J, Fragomen A, Rozbruch SR. Ankle Distraction Arthroplasty: Indications,Technique, and Outcomes. J Am Acad Orthop Surg 2017; 25: 89-99 [PMID: 28030511 DOI:10.5435/JAAOS-D-14-0007]

10 Rivera JC, Beachler JA. Distraction arthroplasty compared to other cartilage preservation procedures inpatients with post-traumatic arthritis: a systematic review. Strategies Trauma Limb Reconstr 2018; 13: 61-67 [PMID: 29363012 DOI: 10.1007/s11751-018-0305-2]

11 Xu Y, Zhu Y, Xu XY. Ankle joint distraction arthroplasty for severe ankle arthritis. BMC MusculoskeletDisord 2017; 18: 96 [PMID: 28245830 DOI: 10.1186/s12891-017-1457-9]

12 Zak L, Wozasek GE. Tibio-talo-calcaneal fusion after limb salvage procedures-A retrospective study.Injury 2017; 48: 1684-1688 [PMID: 28442207 DOI: 10.1016/j.injury.2017.03.045]Delco ML, Kennedy JG, Bonassar LJ, Fortier LA. Post-traumatic osteoarthritis of the ankle: A distinct

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13 clinical entity requiring new research approaches. J Orthop Res 2017; 35: 440-453 [PMID: 27764893DOI: 10.1002/jor.23462]

14 Zhang K, Jiang Y, Du J, Tao T, Li W, Li Y, Gui J. Comparison of distraction arthroplasty alone versuscombined with arthroscopic microfracture in treatment of post-traumatic ankle arthritis. J Orthop Surg Res2017; 12: 45 [PMID: 28302130 DOI: 10.1186/s13018-017-0546-7]

15 Rammelt S, Zwipp H. Corrective arthrodeses and osteotomies for post-traumatic hindfoot malalignment:indications, techniques, results. Int Orthop 2013; 37: 1707-1717 [PMID: 23912266 DOI:10.1007/s00264-013-2021-2023]

16 McAlister JE, Hyer CF, Black TE. Distraction First Metatarsophalangeal Arthrodesis With TricorticalCalcaneus Autograft: Technique Tips. Foot Ankle Spec 2016; 9: 522-526 [PMID: 27613811 DOI:10.1177/1938640016668029]

17 Stevens J, Meijer K, Bijnens W, Fuchs MC, van Rhijn LW, Hermus JP, van Hoeve S, Poeze M, WitloxAM. Gait Analysis of Foot Compensation After Arthrodesis of the First Metatarsophalangeal Joint. FootAnkle Int 2017; 38: 181-191 [PMID: 27770063 DOI: 10.1177/1071100716674310]

18 Thompson IM, Bohay DR, Anderson JG. Fusion rate of first tarsometatarsal arthrodesis in the modifiedLapidus procedure and flatfoot reconstruction. Foot Ankle Int 2005; 26: 698-703 [PMID: 16174499 DOI:10.1177/107110070502600906]

19 Vulcano E, Chang AL, Solomon D, Myerson M. Long-Term Follow-up of Capsular InterpositionArthroplasty for Hallux Rigidus. Foot Ankle Int 2018; 39: 1-5 [PMID: 28975843 DOI:10.1177/1071100717732124]

20 Buda M, Kink S, Stavenuiter R, Hagemeijer CN, Chien B, Hosseini A, Johnson AH, Guss D, DiGiovanniCW. Reoperation Rate Differences Between Open Reduction Internal Fixation and Primary Arthrodesis ofLisfranc Injuries. Foot Ankle Int 2018; 39: 1089-1096 [PMID: 29812959 DOI:10.1177/1071100718774005]

21 Wapner KL. Triple arthrodesis in adults. J Am Acad Orthop Surg 1998; 6: 188-196 [PMID: 9682081]22 Shorter E, Sannicandro AJ, Poulet B, Goljanek-Whysall K. Skeletal Muscle Wasting and Its Relationship

With Osteoarthritis: a Mini-Review of Mechanisms and Current Interventions. Curr Rheumatol Rep 2019;21: 40 [PMID: 31203463 DOI: 10.1007/s11926-019-0839-4]

23 Smith NC, Beaman D, Rozbruch SR, Glazebrook MA. Evidence-based indications for distraction anklearthroplasty. Foot Ankle Int 2012; 33: 632-636 [PMID: 22995229 DOI: 10.3113/FAI.2012.0632]

24 van der Vliet QMJ, Hietbrink F, Casari F, Leenen LPH, Heng M. Factors Influencing FunctionalOutcomes of Subtalar Fusion for Posttraumatic Arthritis After Calcaneal Fracture. Foot Ankle Int 2018; 39:1062-1069 [PMID: 29862841 DOI: 10.1177/1071100718777492]

25 Weatherall JM, Mroczek K, McLaurin T, Ding B, Tejwani N. Post-traumatic ankle arthritis. Bull Hosp JtDis (2013) 2013; 71: 104-112 [PMID: 24032590]

26 Gianakos A, Kennedy J. Microfracture of subchondral bone leads to persistent subchondral sclerosis andpoorer functional outcomes following distraction arthroplasty of the ankle joint while biologic augmentmay improve recovery times. Foot Ankle Orthopaedics 2018 [DOI: 10.1177/2473011418S00056]

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W J O World Journal ofOrthopedics

Submit a Manuscript: https://www.f6publishing.com World J Orthop 2020 March 18; 11(3): 158-166

DOI: 10.5312/wjo.v11.i3.158 ISSN 2218-5836 (online)

ORIGINAL ARTICLE

Observational Study

Lumbar interspinous pressure pain threshold values for healthyyoung men and women and the effect of prolonged fully flexedlumbar sitting posture: An observational study

Martin Petersson, Allan Abbott

ORCID number: Martin Petersson(0000-0002-7370-686X); Allan Abbott(0000-0002-4318-9216).

Author contributions: Petersson Mand Abbott A contributed to thestudy conception, design and dataacquisition, data analysis,interpretation of data, drafting,critical revision and final approvalof the manuscript.

Institutional review boardstatement: The study wasreviewed and approved by theethics board of second cycleeducation at Linkoping University,Sweden.

Informed consent statement: Allstudy participants, providedinformed written consent prior tostudy enrolment.

Conflict-of-interest statement: Theauthors have no conflict ofinterests. The authors have nofinancial interests.

Data sharing statement: Technicalappendix, statistical code, anddataset available from thecorresponding author atallan.abbott@liu.se. Participantsgave informed consent for datasharing of anonymized data.

STROBE statement: Thismanuscript complies with theSTROBE statement for reporting ofobservational studies.

Open-Access: This article is anopen-access article that wasselected by an in-house editor and

Martin Petersson, Department of Physiotherapy Gripen, Värmland Country Council, KarlstadSE-65224, Sweden

Martin Petersson, Allan Abbott, Department of Medical and Health Sciences, Division ofPhysiotherapy, Faculty of Health Sciences, Linköping University, Linköping SE-58183,Sweden

Corresponding author: Allan Abbott, BSc, MHSc, PhD, Associate Professor, Physiotherapist,Department of Medical and Health Sciences, Division of Physiotherapy, Faculty of HealthSciences, Linköping University, Sandbäcksgatan 7, Linköping SE-58183, Sweden.allan.abbott@liu.se

AbstractBACKGROUNDLow back pain (LBP) is a common condition with large burden worldwide.Exposure to prolonged sitting with a flexed lumbar posture has been suggestedin the literature to be a potential risk factor for self-reported LBP. No study haspreviously investigated whether exposure to prolonged flexed sitting postureprovokes discomfort/pain and decreased interspinous pressure pain thresholdsfor healthy young men and women without back pain, despite this being asuggested risk factor for LBP.

AIMTo investigate whether sitting in a prolonged flexed lumbar posture provokesdiscomfort and lowers interspinous pressure pain thresholds in the lumbar spinefor healthy young men and women without previous LBP.

METHODSThis is a an observational before and after study of 26 participants (13 men, 13women) between 20-35 years old. Algometry was used to examine the painthreshold for pressure applied between spinous processes of the lumbar spine L1-L5. Pressure algometer measures were performed in prone before and afterparticipants were instructed to sit in a fully flexed posture for a maximum of 15min or until discomfort was experienced in the low back (Borg CR10 = 7/10).Wilcoxon signed-rank test was used for analyze values from the before and aftertest conditions. Mann-Whitney U test was used to investigate potential genderdifference.

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fully peer-reviewed by externalreviewers. It is distributed inaccordance with the CreativeCommons AttributionNonCommercial (CC BY-NC 4.0)license, which permits others todistribute, remix, adapt, buildupon this work non-commercially,and license their derivative workson different terms, provided theoriginal work is properly cited andthe use is non-commercial. See:http://creativecommons.org/licenses/by-nc/4.0/

Manuscript source: Invitedmanuscript

Received: November 8, 2019Peer-review started: November 8,2019First decision: December 4, 2019Revised: February 26, 2020Accepted: March 5, 2020Article in press: March 5, 2020Published online: March 18, 2020

P-Reviewer: Elfering A, MousaHALS-Editor: Wang YQL-Editor: AE-Editor: Liu MY

RESULTSFully flexed lumbar spine sitting posture up to 15 min provoked temporarydiscomfort but the proportion of participants experiencing discomfort 7/10 in thelow back was 62%. For all pain pressure threshold locations tested, there was asignificant difference for the study population with moderate-large decreased (r =-0.56) pressure pain threshold after exposure to prolonged flexed sitting posture(P < 0.01). Comparisons between gender did not show any significant difference.

CONCLUSIONThe result showed that exposure to fully flexed lumbar sitting posture for up to15 min produced temporary discomfort in the low back in young healthy adultswith no previous history of LBP and significantly reduced lumbar interspinouspressure pain thresholds. No gender-based differences were observed.

Key words: Low back pain; Pain pressure threshold; Algometer; Posture; Spine; Painmechanism

©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.

Core tip: Fully flexed lumbar sitting posture for a maximum of 15 min causes discomfortand significantly reduced lumbar interspinous pain pressure thresholds.

Citation: Petersson M, Abbott A. Lumbar interspinous pressure pain threshold values forhealthy young men and women and the effect of prolonged fully flexed lumbar sittingposture: An observational study. World J Orthop 2020; 11(3): 158-166URL: https://www.wjgnet.com/2218-5836/full/v11/i3/158.htmDOI: https://dx.doi.org/10.5312/wjo.v11.i3.158

INTRODUCTIONLow back pain (LBP) is a common condition with large burden worldwide[1].Exposure to prolonged sitting with a flexed lumbar posture has been suggested in theliterature to be a potential risk factor for self-reported LBP but strong evidence islacking regarding if occupational sitting is an independent causal factor[2-5] . Severalstudies have investigated possible mechanisms of how prolonged flexed posturesmay influence the onset of LBP and discomfort. Flexed lumbar posture tensionsposterior segmental structures such as the interspinous ligaments of the lumbar spine,which contribute to the prevention of lumbar hyperflexion[6]. Prolonged tensioning ofposterior segmental structures causes viscoelastic deformation of trunk soft tissues,reductions in intrinsic trunk stiffness and alters the active neuromuscular behavior[7-11].This may in theory produce nociception and peripheral sensitization of thesestructures leading to reduced thresholds for nociception[12,13]. Furthermore, in theevent of prolonged nociception or maladaptive psychosocial factors negativelyaffecting the pain experience, a decreased functioning of descending nociceptioninhibiting pathways may contribute to a central nervous system sensitization[13]. Thismay further reduce nociceptive pain thresholds or lead to the persistence of painwithout nociceptive stimulus[14].

Biochemical processes may even be influenced by prolonged tissue loadingproviding a pathway for tissue sensitivity and inflammation[15]. Staud et al[16] displayedthat healthy individuals who have been repeatedly provoked by tissue stress canexperience increased sensitivity and the persistence of the pain[16].

Research has shown that individuals with lumbar pain have lower pain thresholdsthan healthy individuals[17-20]. In these studies, pain thresholds in the lumbar spine arecommonly measured using a pressure gauge indicating kilopascals per second(kPa/s) of increasing pressure application until pain is perceived by the subject[17-22].

Only one study, Imamura et al[19], has investigated the interspinous pressure painthresholds between the L1-L5 lumbar spinous processes. Gender differences havebeen observed in pressure pain thresholds[23,24], but no study has investigated possiblegender difference regarding interspinous pressure pain thresholds. No study haspreviously investigated whether exposure to prolonged flexed sitting posture affectsinterspinous pressure pain thresholds for healthy young men and women without

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back pain, despite this being a suggested risk factor for LBP[2-4]. The purpose in thisstudy is to investigate whether exposure to prolonged fully flexed lumbar sittingposture provokes discomfort and lowers interspinous pressure pain thresholds in thelumbar spine for healthy young men and women without previous lumbar pain. Thehypothesis is that there is a significant decrease in interspinous pressure painthresholds after exposure to prolonged fully flexed lumbar sitting posture provokingdiscomfort and that there is a significant difference between men and women.

MATERIALS AND METHODS

Research designThis is an observational study of pressure pain thresholds before and after exposureto discomfort from prolonged fully flexed lumbar sitting in health men and women.Therefore, cases are their own controls in a before and after exposure design.According to Swedish law (2003: 460) on the ethics of human research, it is describedthat all research performed and dealing with sensitive personal data should beethically tested. Section 2 of this law states that regional ethical committee assessmentis required for “Scientific experimental or theoretical work to acquire new knowledgeor scientific quality improvement work, but not such work done in the framework offirst or second cycle education[25]. Therefore, because this study was conducted as apart of a master's thesis, ethical approval was provided after assessment performedaccording to the Helsinki declaration by the ethics board of second cycle education atLinkoping University.

ParticipantsThe recruitment of potential participants occurred between the dates of January 2017to Mars 2017 through informing a convenience sample of students at LinkopingUniversity, Sweden, about the study. Inclusion criteria for participation were healthyindividuals without current or previous lumbar pain, aged between 20 to 35 years.Exclusion criteria included diagnosed medical conditions, current or previous lumbarpain, pregnancy, tolerance of ≥ 1000 kPA algometer lumbar interspinous pressurewithout provoking pain during the initial measurements. A a-priori sample sizecalculation was performed using GPower 3.1. This was based on the probability ofdetecting a significant difference (P = 0.05) between the pre and post pain pressurethreshold measurement with 80% statistical power and a hypothesised effect size of r= 0.5. The result of the calculation indicated that 26 participants were required. Inorder for the sample to be as representative as possible, 13 men and 13 women wererecruited.

MeasurementsThe algometer used for the measurements was of the SOMEDIC Electronics brand(Solna, Sweden) (Figure 1).

In a study by Waller et al[26], intra- and inter-examiner reliability was examinedregarding algometry on healthy young people, including the testing of locations suchas the lumbar spine. The measurement method was found to have both good intra-examiner reliability (ICC = 0.94-0.99) and inter-examiner reliability (ICC = 0.90-0.98)[26]. Other studies also show good reliability[27,28].

Before each measurement, a quality control of the instrument was performedthrough calibration, to ensure it was functioning. This study used a 1 cm² roundrubber sheet ending on the algometer applying a pressure velocity of 50 kPA / s, likeother studies such as Waller et al[26]. Measurement of pain thresholds was performedbetween the spinous processes from L1 to L5 (L1-L2, L2-L3, L3-L4 and L4-L5). Thesewere identified through valid palpation methods using multiple bony landmarks[29,30].The measurement was thus performed on four points with three measurements ateach point to calculate an average, resulting in 12 pressure final measures. Betweeneach measurement time, a 10 s pause in testing occurred consistent with test protocolsfrom previous studies[18,24,26,31]. The participants were tested in a prone position on aplinth where the interspinous areas between spinal processes from L1 to L5 weremarked with a felt pen to ensure that the repeated application of the pressure was atthe correct point. During the measurement, participants communicated verbally, bythe word "stop", when the first sense of pain was detected. The pressure was thenstopped. After the baseline algometry measures, the participants changed directly to aseated position, without rest, on a chair in a full flexed lumbar position (Figure 2).

Specific instructions guidance to the participants: Sit with 90 degrees flexion of theknee joint and ankle joint, while maintaining the lumbar spine in full flexion withposterior pelvic tilt[32-35]. Participants were also instructed to rest their upper body

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Figure 1

Figure 1 Algometer.

weight on the forearms in the slumped position to emphasis a passive fully flexedlumbar positioning rather than erector spinae activity. The author ensured the testposition was consistent for all participants.

Participants were asked not to change position during the test. The participantseither sat for a maximum of 15 min or until they experienced a 7/10 rating ofdiscomfort (0 = no pain/discomfort – 10 = maximum pain/discomfort) in the lumbarspine according to Borg CR10[36]. The scale can be used for measuring differentsensory sensations and experiences including pain and discomfort with good validityand reliability[36]. The time of 15 min for the test was determined on the basis ofSolomonow et al[7], which found that 15 min in maximum flexed lumbar posturecauses high strain on the supraspinal ligaments. Immediately after the test, a similarmeasurement procedure was performed as during the first measurement to determinewhether there were differences between pressure pain thresholds before and after theprolonged lumbar flexion experiment.

Data analysisThe collected data was manually entered into IBM SPSS version 23 program, where allanalytical calculation was performed. Non-parametric statistics have been usedbecause none of the measurement variable data distributions fulfilled the assumptionsof normality. Descriptive statistics are reported as median and interquartile range(IQR). To compare the measurements between pre-test and post-test differenceswithin the group, a Wilcoxon signed ranks test has been performed. The test has beenconducted to see if there was any significant difference between the pain thresholdbefore and after prolonged fully flexed lumbar sitting posture in healthy individuals.To detect a possible difference between the sexes, a Mann-Whitney U test was used.Statistical significance was set at the P < 0.05 level. Rosenthal[37], proposes analternative effect size measure when the general assumptions of Cohen's d formula areviolated. In this case, effect size r is proposed for pre-test to post-test change inpressure pain thresholds, calculated by dividing the Z-standardised test statistic bythe square root of the number of observations over the 2 time points (2 × 26observations). Effect size r = 0.10 is considered a small effect, r = 0.30 is a mediumeffect and r > 0.50 is a large effect size[37].

RESULTSAll 26 participants (13 men and 13 women) completed the study. The median age forthe entire study population was 24.0 years (IQR = 3). By comparison, median age forwomen was 23 (IQR = 8) years and 24 (IQR = 3) years for men. There was a significantdifference (P = 0.01) of age between the sexes. As a result of the fully flexed lumbarspine sitting posture, all participants experienced temporary discomfort in the lowerback but the proportion with discomfort of 7/10 was 62%. Of those completing thefull 15 min exposure (38%) without reaching up to 7/10 discomfort in the lower back,there was an even gender distribution. The median time for the seated flexion test was12 min (IQR = 3). The median time for women was 11.5 min (IQR = 3s) and 12.5 min(IQR = 3) for men showing no statistically significant difference (P > 0.05).

The statistical analysis displayed that for all points tested, there was a significantdifference between pre-test and post-test, with lower pressure pain thresholds post-test. The result demonstrated that exposure to prolonged static sitting in a fully flexedlumbar posture decreases pressure pain threshold of interspinous lumbar spine

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Figure 2

Figure 2 Seated position during the test.

structures. Measurement points in the lumbar spine together had a pre-test painthreshold value of 359 kPa and post-test value of 312 kPa. Regarding pre-test andpost-test effect size difference in pressure pain threshold, the result showed a large r =-0.56 total change for all points in the lumbar spine. (Table 1).

The calculation of pre-test and post-test measurements for women also showed asignificant difference with moderate effect size lowering of post-test pressure painthresholds for all points. The pre-test pressure pain thresholds together for all pointswere 331 kPa and post-test 269 kPa in the lumbar spine (Table 2). The analysisperformed for men also showed a significant difference with moderate effect sizelowering of post-test pressure pain thresholds for all points except for L4-L5 (P =0.069). The pre-test pressure pain thresholds together for all points in the lumbarspine showed a measure of 366 kPa and post-test 322 kPa (Table 3).

There were no statistically significant differences between men and women forpressure pain thresholds measured at pre-test or post-test and with regards to changefrom pre-test to post-test (Table 4).

DISCUSSIONThe results of the study show that interspinous pressure pain thresholds afterexposure to prolonged fully flexed lumbar sitting posture (maximum of 15 min) weresignificantly lowered with moderate – large effect sizes in young men and womenwhich supports our first hypothesis. These results add new objective knowledgeregarding gender-based reference values for interspinous pressure pain threshold forhealthy subjects and new knowledge that prolonged flexed lumbar posture increasesinterspinous tissue pain sensitivity. This could be a potential mechanism among otherfactors reported in previous literature suggesting that flexed lumbar posture mayincrease the risk of self-reported lumbar pain[2-4]. However, according to O'Neill et al[20]

it is likely that lowered pressure pain threshold is associated with but does notconstitute an independent risk factor for the development of persistent lumbar pain.

Previous research has shown that a tissue load applied for a longer period of timemay trigger cytokines associated with nociceptor activation[13,38]. That can beconsidered as a potential physiological mechanism leading to lumbar painexperienced after prolonged fully flexed lumbar sitting posture. Previous researchsuggests a relationship between longer time periods of static sitting and pain in thelumbar spine[2,40]. Bakker et al[3], suggests that intensive use of the lumbar spine inflexion has a strong connection to the development of lumbar pain. Therefore, inrelation to the results of our current study, it is possible that both longer periods ofstatic sitting as well as flexed lumbar posture are possible mechanisms of sensitizationof lumbar spine structures. To compare importance of these potential mechanisms,future experimental trials should investigate variation of flexion in various degreesduring long periods static sitting.

In previous studies, the pressure pain threshold for paraspinal and erector spinaemuscles 2 cm lateral from spinous processes for young people without low back painranges between 536-910 kPa[18,23,24,26]. Furthermore, the normal values reported forspinous processes range between 316-450 kPa[23,26] and for interspinous areas 759kPa[19]. Our findings however show lower interspinous pressure pain thresholds thanGiesbrecht et al[18] in young people without low back pain and are more similar withprevious reported thresholds for spinous processes[23,26]. The measurement process inour study was performed on four points in the lumbar spine and the choice of usingthe mean of 3 tests is based on previous reliability studies showing intra-rater

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Table 1 The median value and quartiles, Wilcoxon signed rank test and effect size r for the whole study population regardinginterspinous pressure pain thresholds before (pre-test) and after (post-test) exposure to prolonged flexed lumbar sitting posture

Variables Pre-test median(quartiles)

Post-test median(quartiles)

Z-standardised teststatistic P value Effect size r

L1-L2 397 (349, 448) 315 (256, 369) -4.382 < 0.001 -0.60

L2-L3 361 (300, 441) 310 (251, 366) -3.798 < 0.001 -0.52

L3-L4 339 (285, 398) 305 (244, 357) -3.480 < 0.001 -0.47

L4-L5 316 (293, 397) 294 (230, 381) -3.277 0.001 -0.45

All variables (L1-L2, L2-L3, L3-L4 and L4-L5)

359 (298, 400) 312 (252, 350) -4.229 < 0.001 -0.56

reliability[27]. One may consider a potential limitation of repeated pain pressurethreshold testing being that it may cause tissue sensitization, which may in turndecrease pain pressure thresholds. However, previous studies using up to 3measurements at the same point to determine pain pressure threshold on lumbarspine structures as well as similar spatial distances between adjacent points and thetime between repeated measurement (at least 10 min) have been shown to preventedspatial and temporal summation[20,41].

The result of the average duration to provoke discomfort in the low back of 7/10was 12 min for exposure to the fully flexed lumbar spine sitting posture. It shows thatthe maximum 15 min may be considered an adequate limit of fully flexed lumbarsitting posture for the majority of health young adults. However, a potentiallimitation in our study is that 38 percent of the participants did reach 15 min in a fullyflexed lumbar sitting posture without experiencing discomfort in the low back up to7/10. Despite this, significant decreases in lumbar pain pressure thresholds wereobserved. If the maximum test time would have been set to 20 min, the average timeto low back discomfort of 7/10 would however probably increase but probably not toa large extent.

The analysis of gender difference in pain pressure thresholds before and afterprolonged fully flexed lumbar sitting posture showed that there were no significantdifferences. Hence, our secondary hypothesis that there is a significant differencebetween women and men regarding thresholds in the lumbar spine cannot beverified. These results are consistent with Farasyn and Lassat[24], who also concludedthat there were no gender differences regarding pressure pain thresholds for lumbarspine erector spinae muscles. On the contrary, in a study by Binderup et al[23], asignificant difference was found regarding the gender difference in pain pressurethresholds for erector spinae muscles and spinous processes in the lumbar spine.Their results showed that men had higher thresholds (506 kPa) than women (428 kPa),whereas our study on a similar sample showed a smaller gender difference (men =366 kPa, women = 331 kPa) without statistical significance. A limitation with ourstudy was however that sample size was not specifically powered to minimizepotential false negative results for gender subgrouping, but a trend was seen thathealthy young adult men have higher lumbar thresholds than women. To investigatefurther, more studies with larger study populations are needed, which with goodpower can demonstrate and clarify whether there is really a gender difference or not.

There are several clinical implications of our research findings. For example, theCoin test is a pain provocation test for the interspinal ligaments[39]. The test has notbeen investigated in studies but nevertheless, the test is used in both teaching andclinical practice. As an algometer was applied in the lumbar interspinous areas in ourstudy, the pain thresholds that were recorded can serve as a reference frame forphysiotherapists who practice coin test in the lumbar spine examination of youngadults. If the pressure activates early-stage pain indicating a low threshold, it may,along with other factors be a potential risk factor for a patient to have developedchronic lumbar pain[20]. The study´s results also support the inclusion of subjectiveassessment of postural sitting behaviors such as prolonged fully flexed lumbar sittingposture and the possible clinical utility as a physical test while conducting a patientinterview. Future research could adapt the sustained lumbar flexion method as anovel experimental pain protocol for pain research.

In conclusion, the result showed that a fully flexed lumbar sitting posture for up to15 min can provoke discomfort in the lower back in young health adults andsignificantly reduce lumbar interspinous pain pressure thresholds. The analysis doesnot show a significant gender difference for the pain thresholds before and after thetest.

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Table 2 The median value and quartiles, Wilcoxon signed rank test and effect size r for women regarding interspinous pressure painthresholds before (pre-test) and after (post-test) exposure to prolonged flexed lumbar sitting posture

Variables Pre-test median(quartiles)

Post-test median(quartiles)

Z-standardised teststatistic P value Effect size r

L1-L2 353 (314, 434) 295 (236, 346) -3.180 0.002 -0.43

L2-L3 319 (271, 416) 286 (219, 347) -2.830 0.005 -0.39

L3-L4 299 (281, 400) 261 (229, 338) -2.551 0.011 -0.35

L4-L5 306 (265, 395) 233 (214, 351) -2.691 0.007 -0.37

All variables (L1-L2, L2-L3, L3-L4 and L4-L5)

331 (288, 403) 269 (227, 344) -2.970 0.003 -0.40

Table 3 The median value and quartiles, Wilcoxon signed rank test and effect size r for men regarding interspinous pressure painthresholds before (pre-test) and after (post-test) exposure to prolonged flexed lumbar sitting posture

Variables Pre-test median(quartiles)

Post-test median(quartiles)

Z-standardised teststatistic P value Effect size r

L1-L2 405 (356, 518) 340 (284, 441) -3.110 0.001 -0.42

L2-L3 379 (337, 421) 322 (288, 470) -2.621 0.009 -0.36

L3-L4 370 (320, 453) 331 (264, 453) -2.378 0.017 -0.32

L4-L5 321 (299, 474) 302 (275, 479) -1.819 0.069 -0.25

All variables (L1-L2, L2-L3, L3-L4 and L4-L5)

366 (288, 403) 322 (227, 344) -3.040 0.002 -0.41

Table 4 The median value, quartiles and Mann-Whitney U test comparing men and women for pressure pain threshold measurement preand post prolonged flexed lumbar sitting posture

Variables

Pre-test Post-test Genderdifference inchange in PPTbetween preand post (Pvalue)

Women median(quartiles)

Men median(quartiles) P value Women median

(quartiles)Men median(quartiles) P value

L1-L2 353 (314, 434) 405 (358, 518) 0.14 295 (236, 346) 340 (284, 441) 0.09 0.96

L2-L3 319 (271, 416) 379 (337, 521) 0.09 286 (219, 347) 322 (288, 470) 0.08 0.92

L3-L4 299 (281, 400) 370 (320, 453) 0.16 261 (229, 338) 331 (264, 453) 0.09 0.88

L4-L5 306 (265, 395) 321 (299, 474) 0.25 233 (214, 351) 302 (275, 479) 0.12 0.13

All variables(L1-L2, L2-L3,L3-L4 and L4-L5)

331 (288, 403) 366 (298, 400) 0.10 269 (227, 344) 322 (285, 455) 0.10 0.55

ARTICLE HIGHLIGHTSResearch backgroundExposure to prolonged sitting with a flexed lumbar posture has been suggested in previousliterature to be a potential risk factor for self-reported Low back pain (LBP).

Research motivationNo study has previously investigated whether exposure to prolonged flexed sitting postureprovokes discomfort in the low back and lowers interspinous pressure pain thresholds forhealthy young men and women without previous back pain, despite this being a suggested riskfactor for LBP.

Research objectivesTo investigate whether sitting in a prolonged flexed lumbar posture provokes discomfort in thelow back and lowers the interspinous pressure pain threshold in the lumbar spine for healthyyoung men and women without previous LBP.

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Research methodsAn observational study of lumbar interspinous algometry was conducted before and after 15min of exposure to prolonged flexed sitting posture in 26 healthy participants (13 men, 13women) between ages 20-35 years who have had no previous low back pain episodes.

Research resultsProlonged flexed sitting posture for up to 15 min provokes temporary discomfort in the lowerback. There was a moderate-large decrease in lumbar interspinous pressure pain threshold afterexposure for both men and women.

Research conclusionsFully flexed lumbar sitting posture for up to 15 min provokes temporary discomfort in the lowerback in most young health adults and significantly reduced lumbar interspinous pain pressurethresholds

Research perspectivesThe study supports prolonged flexed lumbar posture as a potential mechanism provokingdiscomfort in the low back and lowering pain thresholds which may influence risk of future LBPepisodes.

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W J O World Journal ofOrthopedics

Submit a Manuscript: https://www.f6publishing.com World J Orthop 2020 March 18; 11(3): 167-176

DOI: 10.5312/wjo.v11.i3.167 ISSN 2218-5836 (online)

ORIGINAL ARTICLE

Observational Study

Observational study of a new modular femoral revision system

Karen Dyreborg, Michael Mørk Petersen, Sidse Schwartz Balle, Anne Grete Kjersgaard, Søren Solgaard

ORCID number: Karen Dyreborg(0000-0002-9171-875X); MichaelMørk Petersen(0000-0002-2324-6420); SidseSchwartz Balle(0000-0001-5917-1865); Anne GreteKjersgaard (0000-0003-3872-1850);Søren Solgaard(0000-0002-8717-7620).

Author contributions: Dyreborg K,Petersen MM, Kjersgaard AG,Solgaard S designed the research;Dyreborg K, Balle SS, KjersgaardAG, Solgaard S performed theresearch; Dyreborg K, PetersenMM, Solgaard S analyzed the data;Dyreborg K, Petersen MM, BalleSS, Kjersgaard AG, Solgaard Swrote the paper.

Supported by the Zimmer Biomet,No. C004287.

Institutional review boardstatement: This study wasreviewed and approwed by theNational Patient Safety Authorityof Denmark (Case number 3-3013-1695/1/) and by the DataProtection Agency of the Capitalregion in Denmark (number HGH-2016-021, I-Suite number.: 04437).

Informed consent statement: Allstudy participants or their legalguardian provided informedwritten consent about personal andmedical data collection prior tostudy enrolment.

Conflict-of-interest statement: Dr.Petersen reports grants fromZimmer Biomet during the conductof the study. All other authorshave no conflict of interests relatedto the manuscript.

Data sharing statement: Noadditional data are available since

Karen Dyreborg, Anne Grete Kjersgaard, Søren Solgaard, Department of Orthopaedic Surgery,Herlev-Gentofte Hospital, 2900 Hellerup, Denmark

Michael Mørk Petersen, Department of Orthopaedic Surgery, Rigshospitalet, 2100 København,Denmark

Sidse Schwartz Balle, Department of Diagnostic Radiology, Herlev-Gentofte Hospital, 2900Hellerup, Denmark

Corresponding author: Karen Dyreborg, MD, Research Scientist, Surgeon, Department ofOrthopedic Surgery, Herlev-Gentofte Hospital, Kildegårdsvej 28, 2900 Hellerup, Denmark.karendyreborg@hotmail.com

AbstractBACKGROUNDThe uncemented ArcosTM Modular Femoral Revision System (ARCOS) is a newcomprehensive, press-fit revision design. The modular design offers a wide rangeof possible combinations to accommodate different variations of anatomy andbone stock. The ARCOS is made by a proximal body and a distal stem. Asprobably the only ones worldwide we predominantly use a combination of bodyand stem which supports proximal fixation and load, since this mimics theconcept of the primary total hip arthroplasty with proximal weight-bearing,leading to bone stock preservation and no stress shielding or thigh pain.

AIMTo evaluate the early results after femoral revision in a consecutive series ofpatients undergoing surgery over 3 years.

METHODSWe included 116 patients in the study. They were operated in the period August2011 to December 2014 and we got a clinical mean observation time of 4 (0.5-6)years. Clinical and radiographical follow-up included present function of the hipassessed by Harris Hip Score, Oxford Hip Score, and EQ5D (measure of healthoutcome). Of the 116 patients, 17 died in the interim and were consequentlyincluded only in the implant survivorship analysis; 46 patients attended thefollow-up control.

RESULTSIn total 6 (5%) hips were re-revised due to infection (n = 3), fracture (n = 2) orsubsidence (n = 1). No patient was re-revised due to aseptic loosening. The 1-, 2-and 5-year probability of implant survival (95%CI) were 97% (93%-100%), 97%(93%-100%) and 96% (92%-99%), respectively. In this cohort 95 patients received acombination of a proximal broach and a distal curved and slotted stem (BS),

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the research data is confidentialaccording to Danish law when noconsent for data sharing has beenobtained.

STROBE statement: The authorshave read the STROBE Statement-checklist, and the manuscript wasprepared and revised accordingly.

Open-Access: This article is anopen-access article that wasselected by an in-house editor andfully peer-reviewed by externalreviewers. It is distributed inaccordance with the CreativeCommons AttributionNonCommercial (CC BY-NC 4.0)license, which permits others todistribute, remix, adapt, buildupon this work non-commercially,and license their derivative workson different terms, provided theoriginal work is properly cited andthe use is non-commercial. See:http://creativecommons.org/licenses/by-nc/4.0/

Manuscript source: Unsolicitedmanuscript

Received: November 11, 2019Peer-review started: November 11,2019First decision: November 22, 2019Revised: December 2, 2019Accepted: March 1, 2020Article in press: March 1, 2020Published online: March 18, 2020

P-Reviewer: Castagnini F,Papachristou GS-Editor: Wang JL-Editor: AE-Editor: Xing YX

aiming for proximal fixation and load bearing; 21 patients received a differentcombination. When comparing these two groups the BS-group had a 5-yearimplant survival probability (95%CI) of 97% (93%-100%) compared with thegroup of other combinations with a 5-year implant survival probability (95%CI)of 90% (78%-100%) (P = 0.3). Our regression analysis showed that periprostheticfracture as an indication for the ARCOS operation was the only significantnegative outcome predictor. The mean Harris Hip Score result (100 points beingbest) was 83 (range 5-98). The mean Oxford Hip Score result (48 points beingbest) was 40 (range 19-48).

CONCLUSIONThe early results of the ARCOS are promising compared with similar studies. Weencourage the use of the BS combination whenever the bone stock proximally isadequate.

Key words: Hip prosthesis; Arthroplasty; Implantation; Replacement arthroplasty; Totalhip replacements; Modular femoral stem

©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.

Core tip: The ArcosTM Modular Femoral Revision System is a new comprehensive, press-fit revision design. We have evaluated the early results after femoral revision in aconsecutive series of 116 patients in a period of three years. This is a fairly large cohortwhen dealing with arthroplasty reoperations and the special feature of our cohort is thatwe use a combination of implant-modules which strives for proximal load bearing andfixation, mimicking the concept of the primary hip replacements.

Citation: Dyreborg K, Petersen MM, Balle SS, Kjersgaard AG, Solgaard S. Observationalstudy of a new modular femoral revision system. World J Orthop 2020; 11(3): 167-176URL: https://www.wjgnet.com/2218-5836/full/v11/i3/167.htmDOI: https://dx.doi.org/10.5312/wjo.v11.i3.167

INTRODUCTIONIn 2011 we began using the new Arcos Modular Femoral Revision System (ARCOS)for hip revision surgery (Zimmer Biomet Inc., Warsaw, Indiana, USA). This was partof a development over some years, going from using monoblock prostheses to usingmodular prostheses. The uncemented modular prosthesis is now worldwide the mostcommon choice in hip revision surgery[1,2].

The idea behind the modular implants compared to the one-piece implants, is toprovide flexibility to adjust leg length and apply the optimal rotation to addressstability during surgery. In addition, both metaphyseal and diaphyseal defects may beaddressed independently[3,4]. It is essential to evaluate the efficacy of new technologyor new designs[5] . With this study we aimed to evaluate the early results after surgerywith ARCOS, focusing on early reoperation rate and clinical results.

MATERIALS AND METHODSIn this retrospective observational study with clinical and radiographical follow-up,we included 116 consecutive patients who were operated on any indication with theARCOS at Herlev-Gentofte Hospital, Denmark, department of Orthopaedic Surgeryby two chief surgeons per operation. The first patient was operated on August 30,2011 and the last on December 17, 2014. All study participants or their legal guardianprovided informed written consent about personal and medical data collection priorto study enrolment. The Danish Patient Safety Authority granted access to patientfiles for those patients whom we were unable to contact (case number 3-3013-1695/1/).

The acetabular cup was replaced only if it was loose, or in cases of polywear. Therevision implant was an uncemented cup with a surface of trabecular metal with apoly liner. Accordingly, all patients had a metal-on-poly bearing. The ARCOS is a

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wide-ranging, press-fit revision stem design providing the surgeon with multiplestyles of modular proximal and distal bodies for reconstruction of various defectscommonly seen in femoral revision surgery. That being the case, the ARCOS isformed by a proximal body and a distal stem (Figure 1). The proximal bodies arebroach, calcar-replacing or cone-style implants. All proximal bodies are made from Ti-6Al-4V (ASTM F-136 or F-620). The proximal implants are offered in a range of sizeswith standard and high offset neck geometries.

The distal stems consist of slotted, bullet-tip and splined tapered stem (STS) versionsmade to address differing quality of diaphyseal bone, desired fixation and surgicaltechnique. The distal stems are also made from Ti-6Al-4V (ASTM F-136) in a range ofdiameters and lengths. All proximal bodies and distal stems are available withoutBonemaster hydroxyapatite coating for use in the United States and with Bonemasterhydroxyapatite coating for use in Europe. The ARCOS with Bonemaster coating wasused in this study.

In theory, more than 200 combinations of proximal body and distal stem exist. Inreality two combinations or concepts apply for the majority of revision cases. Theseare: (1) A broach proximal body + a distal slotted and curved stem (BS) and (2) A coneproximal body + a distal STS (CS).

The BS combination strives for instant load and fixation proximally. A good fit canbe achieved and in time ingrowth distally around the cylindrical and anatomicallycurved stem will occur. The modules are assembled on the operating table.

On the other hand, the CS combination aims for immediate distal fixation aroundthe conical stem with the possibility of adjustment after stem placement since the conebody comes in three different lengths and is fitted in situ after placement of the distalstem. No proximal fixation or weight bearing is accomplished.

The choice of implant combination was solely decided by the surgeon. Bothcombinations include the possibility of restoring off-set and leg length. However, inthe opinion of the authors the BS combination has the resemblance of a primaryimplant, thus favouring its use.

Preoperatively templating on calibrated X-rays was made on the entire cohort,optimizing the end result of the operation, regarding the biomechanical parameterssuch as leg length and offset (Figure 2). This is especially important when aiming forpreservation of bone stock with the BS combination, since it is assembled prior toinsertion.

Six experienced hip-surgeons in the department performed 123 consecutive totalhip arthroplasty revisions with the ARCOS in the period August 2011 to December2014; 6 patients were operated twice on the same side (they appear in the study justonce with their first ARCOS-operation). Hence, 116 individuals were suitable forenrolment. These patients were invited to participate in the study according to theinclusion criteria (Figure 3). The mean observation time was 4 (0.5-6) years. The onlyreason for follow up shorter than 2 years was death.

The follow-up took place at Herlev-Gentofte Hospital and included evaluation byHarris Hip Score (HHS) (objective), Oxford Hip Score (OHS) and EQ-5D (the twolatter are Patient Reported Outcome Measures)[6,7]. The HHS has a maximum score of100 points (as the best possible outcome) covering pain (1 item, 0–44 points), function(7 items, 0–47 points), absence of deformity (1 item, 4 points), and range of motion (2items, 5 points). The OHS is an outcome measure to assess pain, functional ability anddaily activities. It produces overall scores running from 0 to 48, with 48 being the bestoutcome possible[6,8]. The EQ-5D consists of 2 parts, the first called Dimensions,covering Mobil i ty , Sel f -care , Usual act ivi t ies , Pain/discomfort , andAnxiety/depression. The second part is the EQ-5D VAS-score, an overall self-assessment of wellbeing scoring from 0 to 100 (100 being the best possible). Only theVAS-score is reported in this article. All the radiographic X-rays were jointlyevaluated by the same orthopedic surgeon and radiologist. Compared to the post-surgery X-rays in two planes, the most recent anterior-posterior X-ray was classifiedas: Stationary conditions, subsidence, fracture, re-revision or clearing in the Gruen Zones.

Data sourcesThe following factors were recorded from the electronic journal system: Age, gender,alive/dead, American Society of Anaesthesiologists’ score (ASA), year of primarytotal hip arthroplasty, revision number, cause for revision, cemented/uncementedstatus to be revised, stem to be revised, date of ARCOS surgery, operation-code,proximal body (ARCOS), distal stem (ARCOS), complications during surgery,complications during admission, reoperation of ARCOS (only femur stem, not thecup), date of ARCOS-reoperation.

From the Danish Hip Arthroplasty Registry: Information on bone stockclassification [ 9 - 1 1 ] during surgery, revision number, cause for revision,cemented/uncemented status to be revised, stem to be revised, date of ARCOS

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Figure 1

Figure 1 The ArcosTM modular femoral revision system.

surgery and operation-code were obtained. The Impax Client (Agfa) was used for:Date of X-ray post-surgery, date of the most recent X-ray, analysis of both the post-surgery and the most recent X-ray.

All patients who underwent surgery in the given period were asked to participatein the follow-up study; 40 patients declined participation in clinical andradiographical follow-up due to e.g., old age, poor function or simply “no time” or“not interested” (see flow chart Figure 3). Of course this meant some level of selectionbias, but only with regards to clinical follow-up, not the survival analysis.

Statistical analysisNon-parametric statistics were used for risk factors between the re-revision-groupand the no-re-revision-group. Competing risk and Kaplan Meier survival analysiswere used for the ARCOS stem combination(s). For preoperative factors amultivariate cox method was used to estimate stem failure (cause for revision + ASA+ gender + age + revision number + bone stock classification + ARCOS combination).A statistical review of the study was performed by a professor with extensiveexperience in statistics.

RESULTSThe baseline demographics and the clinical findings are shown in Table 1. Patientswere equally distributed between genders, and a normal distribution was seen in age,ASA and bone stock classification. All patients in this study were in ASA group 1-3.The cause for revision was aseptic loosening for the majority of cases. Of the 14patients with infection, 4 received a two-stage operation.

The stems being removed were largely BiMetric, Spotorno and Lubinus, anexpression of which stems had been used most in the previous years. Perioperativelythe bone stock was classified according to Saleh et al[9,10] and we found 48% with typeII, 34% with type I, 14% with type III and 2% with type IV and V respectively. Ourregression analysis (Table 2) showed that periprosthetic fracture as an indication forthe ARCOS operation was the only significant negative outcome predictor.

The overall 1-, 2- and 5-year probability of implant survival estimated using KaplanMeier and competing risk analysis (with 95%CI) were 97% (93%-100%), 97% (93%-100%) and 96% (92%-99%), respectively (Figure 4). The BS combination was used in 95patients. When we compared the re-revision risk for this group to the 21 patients withother combinations, we got a 1-, 2- and 5-year probability as seen in Figure 3. The“other combinations” were CS = 9, Calcar + Slotted = 11 and Cone + ETO = 1.

The index operation for BS was in 61 cases due to aseptic loosening, in 16 cases dueto periprosthetic fracture, in 14 due to infection, in 1 due to subsidence and in 2because of a broken stem. For the CS combination 8 patients had aseptic loosening, 1had a periprosthetic fracture and finally, there was a single case of a broken stem ascause for index operation (and one missing value). The Calcar+Slotted combinationwas used in 10 cases operated due to aseptic loosening and in 1 case because of abroken stem. The Cone + ETO combination was used just once on the indication ofaseptic loosening.

At the clinical evaluation at follow up (n = 46) we found that the mean EQ-5D VASresult (100 being best) was 72 (range 20-100). The mean HHS result (100 being best)was 83 (range 5-98). The mean OHS result (48 being best) was 40 (range 19-48). At theradiographical evaluation we found 84 hips with stationary conditions, 6 were re-

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Figure 2

Figure 2 The templated X-ray three days before surgery (left); two days after surgery the X-ray is seen withthe new prosthesis (middle); finally, the X-ray after two years (right).

revised, 2 had a cup-revision, 16 had some subclinical subsidence or clearing, 2 had ahealed fracture and 6 patients had no X-rays for comparison (5 because of residence inGreenland, 1 due to unknown causes).

DISCUSSIONOur study describes short-term results and the primary outcome parameter beingevaluated is the failure rate. We find a survival of 96% in total after 5 years verysatisfying. In other early to midterm studies of cementless modular femoral revisionsystems, survival of the prosthesis is reported to be 76%-97% (observation time 4-7years)[12-16], leaving the ARCOS in the upper end of this interval. The importantpreliminary message is clear; the stem is functioning well and has the character of aso-called "safe procedure". The strengths of this study are that it is the firstconsecutive record of this widely used prosthesis and provides early results of a newproduct, which is very important to obtain for research and development purposes.With the present study we have included a large cohort of the BS combination and wefind the concept is performing well. This is interesting since the tendency worldwideis to use the concept of distal fixation (i.e., the CS combination). The BS concept relieson both proximal and distal fixation, using a curved design for better fit, avoidingstress shielding and thigh pain[17,18]. According to Wolff’s law, bone responds to anychanges in mechanical conditions by remodelling and thus changing density andstructure[19-21], through what is known as adaptive remodelling. If no mechanical loadis present, bone will become weaker and the risk of fracture will increase. With theuse of the broach body design, we attempt to create a situation with a proximal loadlike the concept of the primary implants. Furthermore, we find that the versatility ofthe ARCOS implants also makes it possible to address a situation with extremeproximal bone loss by using the CS combination to obtain rigid distal fixation.

The limitations of the present investigation are the retrospective design, the shortfollow-up and that no randomization has been done. On the other hand, the fact thatthe surgeons – two at a time – had the sole right to decide what they found to be thebest solution for the individual patient, may not have been disadvantageous.Unfortunately, we did not have preoperative HHS, OHS and EQ-5D scores and 40patients declined participation in the clinical and X-ray follow-up. However, only sixpatients had no X-rays to compare with at all. Looking at the clinical follow-up wefind these results generally satisfying although the many who did not attend must beconsidered. There were three patients we considered as outliers with very low scoresin all three categories. They all had their revision with ARCOS done due to infectionand had complications with chronic pain or poor function in the subsequent time.Two of these patients were more than 85 years of age and suffered from competingdisorders.

When it comes to the risk factors and evaluation of factors influencing stem failureit is extremely difficult to compare different revision concepts. Many factors affect theoutcome, resulting in very small patient groups. Periprosthetic fracture is associatedwith complications and was the only significant negative prognostic factor in ourstudy. We did not find infection to be a significant risk factor, even though the threeworst clinical outcome scores came from patients with an infection. This has also beenreported in earlier studies[22,23]. Another important variable is bone loss[24]. In thepresent study we could not prove a correlation between bone loss and risk of re-

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Figure 3

Figure 3 Flow diagram.

revision. The degree and location of the bone loss is important for the choice ofrevision concept. We have attempted to use the BS concept in patients with bone lossbelow the metaphysis, and our analysis showed that this has been a satisfyingstrategy. Although not statistically significant, there was a tendency towards bettersurvival rates when using the BS concept.

Most orthopedic surgeons advocate using the STS concept, often in combinationwith extended trochanteric osteotomy (ETO). ETO was seldom used in this study;removal of cement was performed from “the top” to avoid damaging the integrity ofthe femoral canal. We therefore recommend a differentiated use of the variousconcepts depending on the individual bone quality and bone stock.

The generalisability of this study is considered low-to-medium since it is anobservational study with e.g., no randomization or blinding, including only a selectedpopulation with a specific need for surgery for various reasons. Nonetheless this willmost often be the premise for studies concerning revision implants.

In conclusion: The early results show satisfying durability for the ArcosTM ModularFemoral Revision System in its entirety. We encourage surgeons to consider using theBS combination for proximal load and fixation for better preservation of bone stock,less stress shielding and less thigh pain in order to obtain a situation as close to acementless primary total hip as possible.

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Table 1 Baseline data

Count (valid percent) Mean (range)

Sex

Male 57 (49)

Female 59 (51)

Age at operation (yr) 73 (39-95)

ASA

1 21 (20)

2 54 (51)

3 31 (30)

4 and 5 0

Missing data 10

Cause for revision

Aseptic loosening 80 (69)

Periprosthetic fracture 17 (15)

Infection 14 (12)

Other 5 (4)

Missing data 2

Revised stem

BiMetric 38 (32)

Spotorno 20 (17)

Lubinus 22 (19)

Spectron 7 (6)

Corail 6 (5)

Taperloc 2 (2)

Scanhip 2 (2)

Müller 4 (3)

Girdlestone 4 (3)

Osteostynthesis 3 (3)

Other 7 (6)

Missing data 1

Cemented 72 (62)

Not cemented 44 (38)

ASA: American Society of Anaesthesiologists physical status classification; (1) Patient is a completely healthy fit patient. (2) Patient has mild systemicdisease. (3) Patient has severe systemic disease that is not incapacitating. (4) Patient has incapacitating disease that is a constant threat to life. And (5) Amoribund patient who is not expected to live 24 hours with or without surgery.

Table 2 The risk factors for re-revision

Hazard Ratio 95%CI P value

Cause for revision Aseptic loosening (n = 80) 1.00 (1.00, 1.00) 1.000

Infection (n = 14) 3.02 (0.01, 1108.00) 0.713

Fracture (n = 17) 14.22 (1.07, 189.61) 0.045

ASA 1-2 (n = 75) 1.00 (1.00, 1.00) 1.000

3 (n = 31) 1.33 (0.08, 23.26) 0.846

Gender Male (n = 55) 1.00 (1.00, 1.00) 1.000

Female (n = 61) 2.64 (0.26, 26.48) 0.410

Age group < 73 (n = 64) 1.00 (1.00, 1.00) 1.000

≥ 73 (n = 52) 0.44 (0.04, 4.50) 0.485

Revision No revisions (n = 2) 1.00 (1.00,1.00) 1.000

First revision (n = 86) 11.00 (0.04, 2902.06) 0.399

Bone stock quality 1 + 2 (n = 95) 1.00 (1.00, 1.00) 1.000

3-5 (n = 20) 2.23 (0.25, 19.51) 0.470

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Arcos stem Other combinations (n = 21) 1.00 (1.00, 1.00) 1.000

Broach + Slotted (n = 95) 0.11 (0.01, 1.42) 0.091

ASA: American Society of Anaesthesiologists physical status classification.

Figure 4

Figure 4 The X-axes represents years from operation. A: Competing risk analysis, all; B: Competing risk analysis (red: Broach + slotted; black: Othercombinations); C: Kaplan Meier, all; D: Kaplan Meier (red: Broach + slotted; black: Other combinations).

ARTICLE HIGHLIGHTSResearch backgroundThe uncemented ArcosTM Modular Femoral Revision System (ARCOS) is a new comprehensive,press-fit revision design. The modular design offers a wide range of possible combinations toaccommodate different variations of anatomy and bone stock. The ARCOS is made by aproximal body and a distal stem. As probably the only ones worldwide we predominantly use acombination of body and stem which supports proximal fixation and load, since this mimics theconcept of the primary total hip arthroplasty with proximal weight-bearing, leading to bonestock preservation and no stress shielding or thigh pain.

Research motivationWith this study we wanted to evaluate the early results after femoral revision with the newARCOS in a consecutive series of patients who underwent surgery over a period of 3 years. Wealso found it very interesting to find out whether a specific ARCOS combination is performingsuperiorly compared to the most widely used to date.

Research objectivesIn the 1990’s Denmark, we had a scare scenario with bone cement not tested on humans beforeclinical implementation. It became an arthroplasty-scandal and led to financial compensation tothousands of patients. We became fearfully aware how essential it is to evaluate the efficacy ofnew technology or new design. With this study we aimed to evaluate the early results aftersurgery with ARCOS, focusing on reoperation rate and clinical results.

Research methodsIn this retrospective observational study with clinical and radiographical follow-up, we included116 patients. They were operated in the period August 2011 to December 2014 and we got aclinical mean observation time of 4 (0.5-6) years. The only reason for follow up shorter than 2years was death.

Clinical and radiographical follow-up included present function of the hip assessed by HarrisHip Score, Oxford Hip Score, and EQ5D (measure of health outcome). Compared to the post-surgery X-rays in two planes, the most recent anterior-posterior X-ray was classified as:Stationary conditions, subsidence, fracture, re-revision or clearing in the Gruen Zones.

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Of the 116 patients, 17 died in the interim and were consequently included only in the implantsurvivorship analysis; 46 patients attended the follow-up control. Statistics: Non-parametricstatistics was used for risk factors between the re-revision-group and the no-re-revision-group.Competing risk and Kaplan Meier survival analysis were used for the ARCOS stemcombination(s). For preoperative factors multivariate cox method was used to estimate stemfailure.

Research resultsIn total 6 (5%) hips were re-revised due to infection (n = 3), fracture (n = 2) or subsidence (n = 1).No patient was re-revised due to aseptic loosening. The 1-, 2- and 5-year probability of implantsurvival (95%CI) was 97% (93%-100%), 97% (93%-100%) and 96% (92%-99%) respectively. I thiscohort 95 patients received a combination of a proximal broach and a distal curved and slottedstem (BS), aiming for proximal fixation and load bearing; 21 patients received a differentcombination. When comparing these two groups the BS-group had a 5-year implant survivalprobability (95%CI) of 97% (93%-100%) compared with the group of other combinations with a5-year implant survival probability (95%CI) of 90% (78%-100%) (P = 0.3).

Our regression analysis showed that periprosthetic fracture as an indication for the ARCOSoperation was the only significant negative outcome predictor. The mean Harris Hip Score result(100 being best) was 83 (range 5-98). The mean Oxford Hip Score result (48 being best) was 40(range 19-48).

Perioperatively the bone stock was classified according to Saleh et al and we found 48% withtype II, 34% with type I, 14% with type III and 2% with type IV and V respectively. At theradiographical evaluation we found 84 hips with stationary conditions, 6 were re-revised, 2 hada cup-revision, 16 had some subclinical subsidence or clearing, 2 had a healed fracture and 6patients had no X-rays for comparison.

Our study describes short-term results and the primary outcome parameter being evaluated isthe failure rate. Our findings support the hypothesis that an ARCOS combination with proximalload-bearing and fixation reduces the reoperation rate. Of course it is interesting to furtherinvestigate how the long-term outcome with these prostheses is, especially since the tendencyworldwide is to use the concept of distal fixation.

Research conclusionsWe find survival of the ARCOS prosthesis of 96% in total after 5 years very satisfying. Weencourage surgeons to consider using the combination for proximal load and fixation for betterpreservation of bone stock, less stress shielding and less thigh pain in order to obtain a situationas close to a primary total hip as possible. It is essential to evaluate the efficacy of newtechnology or new designs. The ARCOS stem is functioning well and has the character of a so-called “safe procedure”. Proximal fixation and load-bearing is desirable in both primary total hiparthroplasty and in revision total hip arthroplasty to reduce the incidence of stress shielding andthigh pain, and preserve bone stock.

The ARCOS is an uncemented stem design for revision hip arthroplasty. It is combined by aproximal body and a distal stem and in theory more than 200 combinations of proximal bodyand distal stem exist. In reality two combinations or concepts apply for the majority of revisioncases. These are: (1) A broach proximal body + a distal slotted and curved stem (proximal loadand fixation) and (2) A cone proximal body + a distal STS (distal load and fixation). The ARCOSis performing above acceptable. We recommend a differentiated use of the various conceptsdepending on the individual bone quality and bone stock.

Research perspectivesWe ask surgeons to consider using the ARCOS combination for proximal load and fixation thatmimics the primary total hip arthroplasty whenever bone stock is adequate. We are currentlyinvestigating how other ARCOS-populations in other hospitals are doing and whatcombinations of proximal body and distal stem they have received. A randomized controlledtrial would be lovely, and it might be possible with a multicenter study setup.

ACKNOWLEDGEMENTSThe authors would like to send special thanks to consultant in orthopedic surgery JensB Retpen and to MD Elisabeth Waagensen for their indispensable contributions to thiswork.

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2003; 315-4715 Nelissen RG, Pijls BG, Kärrholm J, Malchau H, Nieuwenhuijse MJ, Valstar ER. RSA and registries: the

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6 Paulsen A, Odgaard A, Overgaard S. Translation, cross-cultural adaptation and validation of the Danishversion of the Oxford hip score: Assessed against generic and disease-specific questionnaires. Bone JointRes 2012; 1: 225-233 [PMID: 23610695 DOI: 10.1302/2046-3758.19.2000076]

7 Sørensen J, Davidsen M, Gudex C, Pedersen KM, Brønnum-Hansen H. Danish EQ-5D population norms.Scand J Public Health 2009; 37: 467-474 [PMID: 19535407 DOI: 10.1177/1403494809105286]

8 Beard DJ, Harris K, Dawson J, Doll H, Murray DW, Carr AJ, Price AJ. Meaningful changes for theOxford hip and knee scores after joint replacement surgery. J Clin Epidemiol 2015; 68: 73-79 [PMID:25441700 DOI: 10.1016/j.jclinepi.2014.08.009]

9 Gozzard C, Blom AW, Taylor A. A comparison of the reliability and validity of bone stock lossclassification systems used for revision hip surgery. J Arthroplasty 2003; 18: 638–642 [DOI:10.1016/S0883-5403(03)00107-4]

10 Saleh KJ, Holtzman J, Gafni A, Saleh L, Davis A, Resig S, Gross AE. Reliability and intraoperativevalidity of preoperative assessment of standardized plain radiographs in predicting bone loss at revisionhip surgery. J Bone Joint Surg Am 2001; 83: 1040-1046 [PMID: 11451973 DOI:10.2106/00004623-200107000-00009]

11 Parry MC, Whitehouse MR, Mehendale SA, Smith LK, Webb JC, Spencer RF, Blom AW. A comparisonof the validity and reliability of established bone stock loss classification systems and the proposal of anovel classification system. Hip Int 2010; 20: 50-55 [PMID: 20235067 DOI:10.1177/112070001002000108]

12 Pelt CE, Madsen W, Erickson JA, Gililland JM, Anderson MB, Peters CL. Revision total hip arthroplastywith a modular cementless femoral stem. J Arthroplasty 2014; 29: 1803-1807 [PMID: 24929283 DOI:10.1016/j.arth.2014.04.042]

13 Amanatullah DF, Howard JL, Siman H, Trousdale RT, Mabry TM, Berry DJ. Revision total hiparthroplasty in patients with extensive proximal femoral bone loss using a fluted tapered modular femoralcomponent. Bone Joint J 2015; 97-B: 312-317 [PMID: 25737513 DOI: 10.1302/0301-620X.97B3.34684]

14 Palumbo BT, Morrison KL, Baumgarten AS, Stein MI, Haidukewych GJ, Bernasek TL. Results ofrevision total hip arthroplasty with modular, titanium-tapered femoral stems in severe proximalmetaphyseal and diaphyseal bone loss. J Arthroplasty 2013; 28: 690-694 [PMID: 23273565 DOI:10.1016/j.arth.2012.08.019]

15 Schuh A, Werber S, Holzwarth U, Zeiler G. Cementless modular hip revision arthroplasty using the MRPTitan Revision Stem: outcome of 79 hips after an average of 4 years' follow-up. Arch Orthop Trauma Surg2004; 124: 306-309 [PMID: 15064958 DOI: 10.1007/s00402-004-0656-7]

16 McInnis DP, Horne G, Devane PA. Femoral revision with a fluted, tapered, modular stem seventy patientsfollowed for a mean of 3.9 years. J Arthroplasty 2006; 21: 372-380 [PMID: 16627145 DOI:10.1016/j.arth.2005.08.022]

17 Huang Y, Zhou Y, Shao H, Gu J, Tang H, Tang Q. What Is the Difference Between Modular andNonmodular Tapered Fluted Titanium Stems in Revision Total Hip Arthroplasty. J Arthroplasty 2017; 32:3108-3113 [PMID: 28602532 DOI: 10.1016/j.arth.2017.05.021]

18 Inaba Y, Kobayashi N, Oba M, Ike H, Kubota S, Saito T. Difference in Postoperative Periprosthetic BoneMineral Density Changes Between 3 Major Designs of Uncemented Stems: A 3-Year Follow-Up Study. JArthroplasty 2016; 31: 1836-1841 [PMID: 26952205 DOI: 10.1016/j.arth.2016.02.009]

19 Petersen MM. Bone mineral measurements at the knee using dual photon and dual energy X-rayabsorptiometry. Methodological evaluation and clinical studies focusing on adaptive bone remodelingfollowing lower extremity fracture, total knee arthroplasty, and partial versus total meniscectomy. ActaOrthop Scand Suppl 2000; 293: 1-37 [PMID: 10951716]

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21 Nickelsen TN, Erenbjerg M, Retpen JB, Solgaard S. Femoral revision with impaction allografting and anuncemented femoral component. Hip Int 2008; 18: 278-285 [PMID: 19097005 DOI:10.5301/HIP.2008.809]

22 Gundtoft PH, Overgaard S, Schønheyder HC, Møller JK, Kjærsgaard-Andersen P, Pedersen AB. The"true" incidence of surgically treated deep prosthetic joint infection after 32,896 primary total hiparthroplasties: a prospective cohort study. Acta Orthop 2015; 86: 326-334 [PMID: 25637247 DOI:10.3109/17453674.2015.1011983]

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24 Hashem A, Al-Azzawi A, Riyadh H, Mukka S, Sayed-Noor A. Cementless, modular, distally fixed stemin hip revision arthroplasty: a single-center study of 132 consecutive hips. Eur J Orthop Surg Traumatol2018; 28: 45-50 [PMID: 28702784 DOI: 10.1007/s00590-017-2013-x]

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W J O World Journal ofOrthopedics

Submit a Manuscript: https://www.f6publishing.com World J Orthop 2020 March 18; 11(3): 177-183

DOI: 10.5312/wjo.v11.i3.177 ISSN 2218-5836 (online)

ORIGINAL ARTICLE

Observational Study

Analysis of electrocautery smoke released from the tissuesfrequently cut in orthopedic surgeries

Ali Yeganeh, Mikaiel Hajializade, Alireza Pahlevan Sabagh, Babak Athari, Mahbobeh Jamshidi,Mehdi Moghtadaei

ORCID number: Ali Yeganeh(0000-0003-4455-8041); MikaielHajializade (0000-0002-8999-7016);Alireza Pahlevan Sabagh(0000-0003-1661-1810); Babak Athari(0000-0002-7968-5828); MahbobehJamshidi (0000-0002-1104-8793);Mehdi Moghtadaei(0000-0003-3202-0850).

Author contributions: Yeganeh Adesigned research; Moghtadaei Mand Pahlevan sabagh A performedresearch; Athari B contributed newreagents or analytic tools; JamshidiM analyzed data; Hajializade Mwrote the paper.

Institutional review boardstatement: This study wasreviewed and approved by theEthics Committee of IranUniversity of Medical Sciences.

Informed consent statement: Thepatients provided written consentbefore participation in the study.

Conflict-of-interest statement: Theauthors declare that they have noconflict of interest.

Data sharing statement: All datarequests should be submitted tothe corresponding author forconsideration. Access toanonymized data may be grantedfollowing review.

STROBE statement: The authorshave read the STROBE Statement-checklist of items, and themanuscript was preparedaccording to the STROBEStatement-checklist of items.

Ali Yeganeh, Mikaiel Hajializade, Alireza Pahlevan Sabagh, Department of Orthopaedics Surgery,Rasoul Akram Hospital, Iran University of Medical Sciences, Tehran 1445613131, Iran

Babak Athari, Department of Orthopaedics Surgery, Shahid Mohammadi Hospital, HormozganUniversity of Medical Sciences, Hormozgan, Bandarabbas 1445613131, Iran

Mahbobeh Jamshidi, Department of Chemistry, Payam-e-Nour University, Ghazvin1445613131, Iran

Mehdi Moghtadaei, Department of Orthopaedics Surgery, Rasoul Akram Hospital, IranUniversity of Medical Tehran âProvince, Tehran, Satarkhan 1445613131, Iran

Corresponding author: Mehdi Moghtadaei, MD, Associate Professor, Department ofOrthopaedics Surgery, Rasoul Akram Hospital, Iran University of Medical Tehran Province,Tehran, Satarkhan St. 1445613131, Iran. medicine.ortho@yahoo.com

AbstractBACKGROUNDElectrosurgical smoke could be different by the device of cutting or the type oftissue that is being cut.

AIMTo analyze the electrocautery smoke released from the tissues that are frequentlycut in orthopedic surgeries.

METHODSThe released smoke from electrocautery of five different tissue types (meniscus,ligament, adipose, muscle, and synovium) of five patients who underwent totalknee arthroplasty were collected and analyzed for volatile organic compounds(VOCs) and 27 candidate polycyclic aromatic hydrocarbons (n = 25). Surgicalsmoke was produced with an electrocautery device for 4 min.

RESULTSNone of the 27 evaluated polycyclic aromatic hydrocarbons compounds weredetectable in electrocautery smoke collected from the surgical cutting of thedifferent tissues. The number and identity of detected VOCs were similarbetween the patients but not between tissue types. The number of detected VOCswas the highest in synovial tissue (n = 21) and the lowest in the meniscus andadipose tissue (n = 12). The number of toxic and/or carcinogenic VOCs were themost in the muscle and meniscus tissues (Toluene, Ethylbenzene, and Styrene).

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Open-Access: This article is anopen-access article that wasselected by an in-house editor andfully peer-reviewed by externalreviewers. It is distributed inaccordance with the CreativeCommons AttributionNonCommercial (CC BY-NC 4.0)license, which permits others todistribute, remix, adapt, buildupon this work non-commercially,and license their derivative workson different terms, provided theoriginal work is properly cited andthe use is non-commercial. See:http://creativecommons.org/licenses/by-nc/4.0/

Manuscript source: UnsolicitedManuscript

Received: September 19, 2019Peer-review started: September 19,2019First decision: October 13, 2019Revised: November 13, 2019Accepted: January 8, 2020Article in press: January 8, 2020Published online: March 18, 2020

P-Reviewer: Gato WES-Editor: Ma YJL-Editor: AE-Editor: Liu MY

No toxic and/or carcinogenic VOCs were identified in the ligament and adiposetissue.

CONCLUSIONMeniscus and muscle tissue are associated with the highest number of toxicand/or carcinogenic VOCs. Therefore, we recommend that surgeons avoiding theelectrocautery of these tissues.

Key words: Electrocautery smoke; Volatile organic compounds; Polycyclic aromatichydrocarbons; Surgeon caution

©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.

Core tip: No toxic and carcinogenic volatile organic compounds was detected inelectrocautery smoke released from ligament and adipose tissue, while electrocauterysmoke released from meniscus and muscle tissue contains significant toxicity andcarcinogenicity. Therefore, we recommend that surgeons to use other electrosurgicaltechniques for cutting these tissues.

Citation: Yeganeh A, Hajializade M, Sabagh AP, Athari B, Jamshidi M, Moghtadaei M.Analysis of electrocautery smoke released from the tissues frequently cut in orthopedicsurgeries. World J Orthop 2020; 11(3): 177-183URL: https://www.wjgnet.com/2218-5836/full/v11/i3/177.htmDOI: https://dx.doi.org/10.5312/wjo.v11.i3.177

INTRODUCTIONElectrosurgery is a necessary technique that is being used in almost every surgicalprocedure to cut tissues and to control bleeding at the same time. Severalelectrosurgery techniques, including electrocautery, laser ablation, and ultrasonicscalpel dissection, are widely being used for tissue cutting and to decrease bleedingduring surgery through coagulating small blood vessels[1].

The breakdown of cellular membranes and other tissue structures during theelectrosurgical cutting produces many biological by-products that are released in theform of smoke in the operating room environment. The presence of chemicalpollutants (volatile organic compounds or VOCs) and biological hazards in surgicalsmoke have been reported in several investigations[2-5]. Surgical smoke has also beenrevealed to contain several carcinogenic components, mainly polycyclic aromatichydrocarbons (PAH)[6,7]. Therefore, full identification of the toxicological effects ofsurgical smoke is important to prevent an occupational hazard to operating room staffby providing proper protection procedures and devices in surgical rooms.

Recent investigation of Fitzgerald et al[8] suggests that different electrosurgical toolsmay produce smokes containing different concentrations of carcinogenic compoundsand irritant hydrocarbons. Furthermore, dissections from different tissues have beenreported to produce different quantities and types of smoke[9]. Based on this evidence,the optimal pair matching of the electrosurgical tool and the tissue type could be avaluable approach to minimize the potential harm of the released smoke.

In this study, we aimed to compare the VOCs as well as PAH in electrocauterysmoke released from five different human tissue types mainly cut in orthopedicsurgeries. We hypothesized if the number of these hazardous components is more in aspecific tissue, other electrosurgical tools could be suggested for surgical cutting ofthat tissue type. Further exposure preventing strategies could be suggested for thatparticular tissue as well.

MATERIALS AND METHODSThis cross-sectional study was approved by the review board of Iran University ofMedical Sciences under the code of IR.IUMS.REC.1393.25468. The smoke releasedduring the electrocautery of five different tissue types (meniscus, ligament, adipose,muscle, and synovium) of five patients who underwent total knee arthroplasty were

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collected and analyzed. In total, 25 samples were evaluated, consisting of five samplesfor each tissue.

Surgical smoke collection and VOCs evaluationFive tissue samples, including meniscus, ligament, adipose, muscle, and synoviumwith a size of 2 cm × 2 cm, were taken from five patients during total kneearthroplasty surgery. Surgical smoke was produced with an electrocautery device(MEG2, Kavandish System, Tehran, Iran); the power of cut: (70) for 4 min. Smokeswere collected using evacuated canisters. A grab sampling approach was used to fillthe canisters to collect the smoke within 5 cm from the electrocautery interaction site.The collected smokes were analyzed in two modes: The gas model and the solublemodel. For the evaluation of VOCs in the gas model, after using a pre-concentrator,the concentrated samples were analyzed using a gas chromatography-massspectrometry (GC/MS) system (GC-MS Agilent Technologies 6890/5973, NY, UnitedStates) in accordance with the methodology presented in an earlier investigation[10].The GC oven was programmed into four steps including a primary temperature of130 °C and hold time of 3 min, continued by a temperature jump of 50 °C/min to 180°C, followed by another temperature jump of 2 °C/min to 270 °C. Final temperaturejump was 20 °C/min to 300°C with as hold time of 5 min. For the evaluation of VOCsin the liquid model, the concentrated gas was dissolved in 1 ml of methanol and thenintroduced to the GC/MS device(GC-MS Agilent Technologies 6890/5973, NY,United States)[11].

PAH assessmentThe PAH was assessed using the same GC-MS device and according to the previouslydescribed protocol. Briefly, the procedure included sonication extraction, solventexchange, cleanup, nitrogen blowdown, and the final GC/MS analysis[12]. The PAHsanalyzed in this study included Naphthalene, 2-Methylnaphthalene, Acenaphthylene,Acenaphthene, Fluorene, Phenanthrene, Anthracene, Fluoranthene, Pyrene, Benzo(c)fluorene, Cyclopenta(c,d)pyrene, Benz(a)anthracene, Chrysene, 5-Methylchrysene,Benzo{b}fluoranthene, Benzo{k}fluoranthene, Benzo{j}fluoranthene, Benzo{e}pyrene,Benzo{a}pyrene, Perylene, Indeno{1,2,3,-c,d}pyrene, Dibenz{a,h}anthracene,Benzo{g,h,i}perylene, Dibenzo{a,l}pyrene,, Dibenzo{a,e}pyrene, Dibenzo{a,i}pyrene,Dibenzo{a,h}pyrene.

Statistical anylsisStatistical significance is expressed as aP < 0.05, bP < 0.01 (P > 0.05 usually does notneed to be denoted). If there are other series of P values, cP < 0.05 and dP < 0.01 areused, and a third series of P values is expressed as eP < 0.05 and fP < 0.01.

RESULTS

Direct smoke analysisThe results of VOCs released from electrocautery smoke of different tissue types havebeen demonstrated in Table 1. In this respect, a complete agreement was seenbetween VOCs of the same tissues obtained from different cadavers. However, theVOCs of various tissues were considerably different. In this respect, the number ofdetected VOCs was the highest in the synovium (n = 21) and the lowest in themeniscus and adipose tissue (n = 12 for both tissues).

Analysis of liquid modelWhen the collected gas was dissolved in the methanol, the VOCs number reduced tofour compounds, including hexadecanoic acid, methyl ester, 9,12-Octadecadienoicacid (Z, Z), methyl ester, 9-octadecenoic acid, methyl ester, (E), and heptadecanoicacid, 9-methyl, methyl ester. These VOCs were only detectable in adipose tissue andnot in other tissue smokes, including meniscus, synovium, ligament, and muscle. Thedetected VOCs were similar between different cadavers.

PAH analysisNone of the 27 evaluated PAH compounds were detectable in any electrocauterysmoke collected from the surgical cutting of the different tissues, including meniscus,synovium, ligament, muscle, and adipose tissue.

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Table 1 Volatile organic compounds detected in electrocautery smoke released from different tissue types (gas model)

Synovium Muscle tissue Ligament tissue Adipose tissue Meniscus tissue

Toluene 2-Nonynoic acid (replib)1,23,4-butanetetrol Nonanal Pyrrole

1,3,5,-cycloheptatriene Toluene (mainlib) Propanal, 2,3-dihydroxy

Propane Toluene

1-Octene 1,3,5-Cycloheptatriene (replib)2(R),3(S)-1,2,3,4-butanetetrol)

Acetaldehyde 1H-Pyrrole , 2-methyl

1,6-heptadiene Ethylbenzene 2S,3S)-(-)-3-Propyloxiranemethanol

1-hexanol,5-methyl Ethylbenzene

L-Homoserine DL-3-Aminoisobutyric acid Glicerin Histamine Phenylethyne

2-Decene,(z) Styrene N-(tert-Butoxycarbonyl)glycine

Maleic acid Styrene

2,5,7 –Cyclooctatetraene 1,3,5,7-cyclooctatetraene 7-methylgunosine 5-Methyl-1-heptanol Bicyclo[4.2.0] octa-1,3,5 –triene

1, Bicyclo[4.2.0]octa- 1,3,5-triene

1-Hexanol, 4-methyl Vinyl Ether 2-Octenal Tetrahydro 1H-pyrrolo[1,2-c]imidazole-1,3(2H)-dione,

Cyclohexene Butanal Caprolactam l-prolinamide l-proline

Phenylacetic acid Acetamide 2,3,dihydrofuran Methylphosphonic acid l-prolinamide

1-Hexene,3,5-dimethyl 2,5-Pyrrolidinedione 2-Butenal Pyrrolo[1,2-a]pyrazine-1,4-dione, hexahydro

Pyrolo(1,2-a) pyrazine-1,4-dione,hexahydro

Propane Maleic acid Pyrrolo[1,2-a]pyrazine-1,4-dione, hexahydro

Nonanal 2-Pyrrolidinemethanamine,N-methyl

l-prolinamide

2,5-Pyrrolidinedione Isoxazole

5-dodecene 5-Methyl-2-pyrrolidinone

1H-Pyrroolo[1,2,-c]imidazone-1,3(2H)-dione,tetrahydro

Pyrrolo[1,2-a]pyrazine-1,4-dione, hexahydro

L-proline, 1-acetyl-, methylester

(mainlib) Sydnone, 3-methyl

L-Glutamic acid

2-acetyl-cycloctanone

Pyrrolo[1,2-a]pyrazine- 1,4-dione, hexahydro

1,2,3-Trimethyl-5-(2-thia-n-hexyl)piperid-4-one

DISCUSSIONOperating room staff are exposed to surgical smoke as the by-product of surgicalcutting using the different electrosurgical tools. This surgical smoke is a mixture ofbiological and chemical pollutants that could be infectious, toxigenic, andcarcinogenic[13]. Therefore, the development of protection strategies to facilitate lessexposure of operating room personnel to surgical smoke is of critical value. Oneeffective strategy could be the identification of the tissues and devices with the mosthazardous smokes.

In this study, we aimed to identify the VOAs and PAH released from electrocauterycutting of five different tissues taken from five different cadavers. The tissue selectionwas based on the most frequently cut in orthopedic workouts. Based on the results ofthe present study, several hazardous VOCs were detected in the electrocautery smokeof different tissues. The highest number of VOCs were detected in the synovium (n =21), and the lowest number of VOCs were detected in adipose and meniscus tissues (n= 12). While the number of detected VOCs was different between the tissues, acomplete agreement was seen between the numbers of VOCs in the same tissues ofdifferent cadavers. In the solubilized model, only four VOCs were detectable inadipose tissue, while no VOCs were detected in the solubilized model of the othertissues. None of the 27 PAH compounds were detected in any of the evaluated tissuesmokes.

Karjalainen et al[9] estimated the composition of particulate matter from surgicalsmoke of different tissue types obtained from Finnish landrace porcine, includinglung, skeletal muscle, renal pelvis, liver, subcutaneous fat, renal cortex, bronchus,

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cerebral gray and white matter, and skin. They found a significant difference in theidentity and concentration of the surgical smoke particles depending on theelectrocauterized tissue. In this respect, the liver tissue produced the highest numberof particles. They suggested that the tissues can be divided into three distinctcategories including (1) high-PM tissue such as liver; (2) medium-PM tissues such asskeletal muscle; and (3) low-PM tissues such as skin. Similar to the study ofKarjalainen et al[9], the results of the present study revealed the different surgicalsmoke particles in different tissue types.

Sisler et al[14] aimed to determine the airborne particle number concentration anddistribution in electrocautery smoke of human breast tissue. All targeted VOCs (n =17) were detected in most of the sampling sessions. Furthermore, electrocauterysmoke generated from human breast tissue induced cytotoxicity in cell culture. FewerVOCs were detected by headspace analysis (solubilized gas model) compared todirect gas analysis due to different solubility and volatility of the VOCs. Similar to thestudy of Sisler et al[14], fewer VOCs were detected in the dissolved gas model of thepresent study.

The VOCs content of electrocautery smoke released from different human tissueshas also been evaluated in many other investigations, and their hazardouscharacteristics have been revealed[6,15]. To the best of our knowledge, analysis ofelectrocautery smoke released from synovium has not been performed in earliersurveys. Since the highest number of VOCs was detected in the synovial tissue inpresent comparative study, more preventive strategies should be implemented insurgeries that involve synovium cutting, such as total arthroplasty, to protect thesafety of operating room personnel.

Tseng et al[12] aimed to investigate the potential hazards and cancer risk ofelectrocautery smoke in ten mastectomies. The particle concentration andgaseous/particle PAHs were measured using a particle counter and filter/adsorbentsamplers. High PAH concentrations were detected in electrocautery smoke duringregular surgical mastectomies. Most particles were in the size range potentiallypenetrable through the medical masks. The average concentration of particle/gaseousat the surgeon's breathing height was 20 to 30 times higher than those in regularoutdoor environments. The estimated cancer risk was 117 × 10-6 for the surgeons and270 × 10-6 for the anesthetic technologists. They strongly suggested using an effectivesmoke evacuator or smoke removal apparatus to diminish the hazards ofelectrocautery smoke to surgical staff[12]. By contrast to the study of Tseng et al[12], wedid not detect any PAH compounds in any tissues of our series. This could simply beattributed to the different tissue properties or other technical differences such as thepower level of electrocautery device, ventilation rate of the operation room, utilizingthe LEV system, etc. In many cases, future investigations are needed to resolve thisinconsistency.

Although the number of VOCs could be considered as an indirect representation ofthe potential hazard of electrosurgical smoke, targeted identification of toxic andcarcinogenic substances could be a more strong approach to estimate the biohazardsof the electrosurgical smoke. Kocher et al[16]. identified nine main toxic and/orcarcinogenic substances from the smoke released from the electrocautery of the freshporcine tissue, including acetylene, hydrogen cyanide, 1,3-butadiene, benzene,toluene, furfural, styrene, ethylbenzene, and 1-decene. While the highest number ofVOCs was detected in the synovium tissue of the present study, the highestpercentage of toxic and/or carcinogenic substances was detected in the meniscustissue with the lowest number of VOCs. In this regard, three out of 11 VOCs (27.3%)detected in meniscus were toxic and/or carcinogenic (Toluene, Ethylbenzene, andStyrene). The same toxic and/or carcinogenic VOCs were also detected in the muscletissue (3/17: 17.6%). Toluene was the only toxic and/or carcinogenic substancedetected in the synovium (1/21: 4.8%). No toxic and/or carcinogenic substance wasdetected in the electrocautery smoke released from ligament and adipose tissue. Theseresults reveal that the potential hazard of electrocautery smoke could be more intissues with less released VOCs, as more toxic and/or carcinogenic substances couldbe detected in one tissue type regardless of the number of VOCs.

This study had some limitations that should be pointed out. As the main limitationof this study, we did not evaluate the size and concentration of particles, which aredetermining factors when assessing the potential hazards of chemical pollutants.Therefore, further studies are recommended with a focus on the size andconcentration of VOCs and PAHs in tissues that were assessed in this study.

In conclusion, although no PAH component was detected in any of the evaluatedtissues, the electrocautery smoke of the tissues that are frequently cut in orthopedicsurgeries was different in terms of hazardous particle content. In this respect, synovialtissue was associated with the highest number of VOCs, and meniscus tissue wasassociated with the lowest number of VOCs. The number of toxic and/or carcinogenic

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substances was the most in the meniscus and muscle tissue.Therefore, further preventive strategies are required to be provided for the safety of

operating room personnel who are exposed to electrocautery smoke released fromthese tissues. In this regard, we recommend using a knife for cutting meniscus andmuscle tissue instead of electrocautery.

ARTICLE HIGHLIGHTSResearch backgroundElectrosurgical methods, including electrocautery, laser ablation, and ultrasonic scalpeldissection, are widely being used in routine surgeries to cut tissues and to control bleeding at thesame time. The smoke released from electrosurgical cutting may contain biological by-productswhich are toxic and carcinogenic. No study has been performed to compare the hazardouscompounds released from the electrocautery of tissues frequently cut in orthopedics, which isthe main purpose of this study.

Research motivationThe operating room staff is frequently exposed to the electrocautery smoke released fromdifferent tissue types. Analysis of the toxicity and carcinogenicity of this smoke is necessary toavoid this health-endangering condition. For tissues releasing a high number of toxic andcarcinogenic compounds, other electrosurgical devices could be suggested.

Research objectivesIn this study, we compared the toxic and carcinogenic compounds released in the electrocauterysmoke of five different tissues frequently cut in orthopedics, including meniscus, ligament,adipose, muscle, and synovium, to find which tissues produce the most hazardous smoke.

Research methodsThe smoke released during the electrocautery of five different tissue types (meniscus, ligament,adipose, muscle, and synovium) of five patients who underwent total knee arthroplasty werecollected and analyzed for volatile organic compounds (VOCs) and 27 candidate polycyclicaromatic hydrocarbons using gas chromatography-mass spectrometry.

Research resultsNone of the 27 evaluated polycyclic aromatic hydrocarbons compounds were detectable inelectrocautery smoke collected from the surgical cutting of the different tissues. The number andidentity of detected VOCs were similar between the patients but not between tissue types. Thenumber of detected VOCs was the highest in synovial tissue (n = 21) and the lowest in themeniscus and adipose tissue (n = 12). However, the highest percentage of toxic and/orcarcinogenic substances was detected in the meniscus tissue with the lowest number of VOCs. Inthis regard, three out of 11 VOCs (27.3%) detected in meniscus were toxic and/or carcinogenic(Toluene, Ethylbenzene, and Styrene). The same toxic and/or carcinogenic VOCs were alsodetected in the muscle tissue (3/17: 17.6%). Toluene was the only toxic and/or carcinogenicsubstance detected in the synovium (1/21: 4.8%). No toxic and/or carcinogenic substance wasdetected in the electrocautery smoke released from ligament and adipose tissue.

Research conclusionsThe quality of released compounds in the electrocautery smoke is more important than thequantity of them so that the potential hazard of electrocautery smoke could be more in tissueswith less released VOCs. In the present study, the highest number of toxic and/or carcinogenicsubstances was detected in meniscus and muscle tissue with the lowest number of VOCs.

Research perspectivesFurther preventive strategies are required to be provided for the safety of operating roompersonnel who are exposed to electrocautery smoke released from these tissues. In this regard,we recommend using a knife for cutting meniscus and muscle tissue instead of electrocautery.

REFERENCES1 Munro MG, Feldman L, Fuchshuber P, Jones D. Fundamentals of Electrosurgery Part I: Principles of

Radiofrequency Energy for Surgery. The SAGES Manual on the Fundamental Use of Surgical Energy(FUSE). Feldman L, Fuchshuber P, Jones D. New York: Springer 2012; 15-59 [DOI:10.1007/978-1-4614-2074-3_2]

2 Barrett WL, Garber SM. Surgical smoke: a review of the literature. Is this just a lot of hot air? SurgEndosc 2003; 17: 979-987 [PMID: 12640543 DOI: 10.1007/s00464-002-8584-5]

3 Al Sahaf OS, Vega-Carrascal I, Cunningham FO, McGrath JP, Bloomfield FJ. Chemical composition ofsmoke produced by high-frequency electrosurgery. Ir J Med Sci 2007; 176: 229-232 [PMID: 17653513DOI: 10.1007/s11845-007-0068-0]

4 Hensman C, Baty D, Willis RG, Cuschieri A. Chemical composition of smoke produced by high-frequency electrosurgery in a closed gaseous environment. An in vitro study. Surg Endosc 1998; 12: 1017-1019 [PMID: 9685533 DOI: 10.1007/s004649900771]Hill DS, O'Neill JK, Powell RJ, Oliver DW. Surgical smoke - a health hazard in the operating theatre: a

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5 study to quantify exposure and a survey of the use of smoke extractor systems in UK plastic surgery units.J Plast Reconstr Aesthet Surg 2012; 65: 911-916 [PMID: 22445358 DOI: 10.1016/j.bjps.2012.02.012]

6 Gatti JE, Bryant CJ, Noone RB, Murphy JB. The mutagenicity of electrocautery smoke. Plast ReconstrSurg 1992; 89: 781-4; discussion 785-6 [PMID: 1561248 DOI: 10.1097/00006534-199205000-00002]

7 Näslund Andréasson S, Mahteme H, Sahlberg B, Anundi H. Polycyclic aromatic hydrocarbons inelectrocautery smoke during peritonectomy procedures. J Environ Public Health 2012; 2012: 929053[PMID: 22685482 DOI: 10.1155/2012/929053]

8 Fitzgerald JE, Malik M, Ahmed I. A single-blind controlled study of electrocautery and ultrasonic scalpelsmoke plumes in laparoscopic surgery. Surg Endosc 2012; 26: 337-342 [PMID: 21898022 DOI:10.1007/s00464-011-1872-1]

9 Karjalainen M, Kontunen A, Saari S, Rönkkö T, Lekkala J, Roine A, Oksala N. The characterization ofsurgical smoke from various tissues and its implications for occupational safety. PLoS One 2018; 13:e0195274 [PMID: 29649244 DOI: 10.1371/journal.pone.0195274]

10 LeBouf RF, Stefaniak AB, Virji MA. Validation of evacuated canisters for sampling volatile organiccompounds in healthcare settings. J Environ Monit 2012; 14: 977-983 [PMID: 22322315 DOI:10.1039/c2em10896h]

11 Yousefinejad S, Eftekhari R, Honarasa F, Zamanian Z, Sedaghati F. Comparison between the gas-liquidsolubility of methanol and ethanol in different organic phases using structural properties of solvents. J MolLiq 2017; 241: 861-869 [DOI: 10.1016/j.molliq.2017.06.081]

12 Tseng HS, Liu SP, Uang SN, Yang LR, Lee SC, Liu YJ, Chen DR. Cancer risk of incremental exposure topolycyclic aromatic hydrocarbons in electrocautery smoke for mastectomy personnel. World J Surg Oncol2014; 12: 31 [PMID: 24499532 DOI: 10.1186/1477-7819-12-31]

13 Choi SH, Choi DH, Kang DH, Ha YS, Lee JN, Kim BS, Kim HT, Yoo ES, Kwon TG, Chung SK, KimTH. Activated carbon fiber filters could reduce the risk of surgical smoke exposure during laparoscopicsurgery: application of volatile organic compounds. Surg Endosc 2018; 32: 4290-4298 [PMID: 29770884DOI: 10.1007/s00464-018-6222-0]

14 Sisler JD, Shaffer J, Soo JC, LeBouf RF, Harper M, Qian Y, Lee T. In vitro toxicological evaluation ofsurgical smoke from human tissue. J Occup Med Toxicol 2018; 13: 12 [PMID: 29619075 DOI:10.1186/s12995-018-0193-x]

15 Sagar PM, Meagher A, Sobczak S, Wolff BG. Chemical composition and potential hazards ofelectrocautery smoke. Br J Surg 1996; 83: 1792 [PMID: 9038572 DOI: 10.1002/bjs.1800831241]

16 Kocher GJ, Sesia SB, Lopez-Hilfiker F, Schmid RA. Surgical smoke: still an underestimated healthhazard in the operating theatre. Eur J Cardiothorac Surg 2019; 55: 626-631 [PMID: 30388210 DOI:10.1093/ejcts/ezy356]

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W J O World Journal ofOrthopedics

Submit a Manuscript: https://www.f6publishing.com World J Orthop 2020 March 18; 11(3): 184-196

DOI: 10.5312/wjo.v11.i3.184 ISSN 2218-5836 (online)

SYSTEMATIC REVIEWS

Systematic review of the etiology behind patellar clunk syndrome

Sean Bertram Sequeira, James Scott, Wendy Novicoff, Quanjun Cui

ORCID number: Sean BertramSequeira (0000-0003-2564-8703);James Scott (0000-0001-6704-046X);Wendy Novicoff(0000-0002-5146-7706); Quanjun Cui(0000-0003-4285-4488).

Author contributions: Cui Qconceived the study idea anddesigned the research with Scott J;Sequeira SB wrote the manuscriptand analyzed the data; Sequeira SBcollected the data; Sequeira SB, CuiQ, Novicoff W, and Scott J editedand revised the manuscript.

Conflict-of-interest statement: Nopotential conflicts of interestrelevant to this article werereported.

PRISMA 2009 Checklist statement:The authors have read the PRISMA2009 Checklist, and the manuscriptwas prepared and revisedaccording to the PRISMA 2009Checklist.

Open-Access: This article is anopen-access article that wasselected by an in-house editor andfully peer-reviewed by externalreviewers. It is distributed inaccordance with the CreativeCommons AttributionNonCommercial (CC BY-NC 4.0)license, which permits others todistribute, remix, adapt, buildupon this work non-commercially,and license their derivative workson different terms, provided theoriginal work is properly cited andthe use is non-commercial. See:http://creativecommons.org/licenses/by-nc/4.0/

Manuscript source: Unsolicitedmanuscript

Received: September 28, 2019

Sean Bertram Sequeira, James Scott, Wendy Novicoff, Quanjun Cui, Department of OrthopedicSurgery, University of Virginia School of Medicine, Charlottesville, VA 22908, United States

Corresponding author: Quanjun Cui, MD, G.J. Wang Professor of Orthopedic Surgery, ViceChair for Research, Department of Orthopedic Surgery, University of Virginia School ofMedicine, 400 Ray C Hunt Dr, Charlottesville, VA 22908, United States.qc4q@hscmail.mcc.virginia.edu

AbstractBACKGROUNDTotal knee arthroplasty is one of the most successful operations performedworldwide today. Patellar clunk syndrome (PCS) is a postoperative complicationthat arises due to the development of a fibrous nodule along the undersurface ofthe quadriceps tendon. The current literature on PCS has not yet come to aconsensus regarding its etiology. To date, this is the first study that analyzes theexisting literature on PCS in order to generate a conclusion regarding its etiology.It is hypothesized that prosthesis design is the main component behind thedevelopment of PCS.

AIMTo determine the etiology of PCS and its association with pre and post-operativecharacteristics of the prosthesis and native knee.

METHODSWe conducted a systematic review according to the PRISMA guidelines bysearching through PubMed, Cochrane, and Google Scholar from May-July 2018for cases of PCS using search MeSH terms “patella OR patellar” AND “clunk”OR “catch” OR “crepitus”. The search included case series and clinical trials andexcluded review articles, yielding 30 articles from the original search and 3additional articles from reference lists. We extracted data upon the outcomes inpatients afflicted with PCS to determine the etiology of PCS. We performedadditional bias assessments to validate our search algorithm and results.

RESULTSProsthesis design was the metric most frequently implicated in the incidence ofPCS, though several other metrics were contributory toward its pathogenesis.Later prosthetic designs incorporate a reduced intercondylar box ratio and boxwidth to reduce contact between the proximal patellar pole and the intercondylarbox, thereby reducing incidence of PCS.

CONCLUSIONThe etiology of PCS is multifactorial, owing to the growing metrics that haveassociations with its incidence. This conclusion is validated by the significance of

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Peer-review started: September 28,2019First decision: December 24, 2019Revised: December 24, 2019Accepted: January 19, 2020Article in press: January 19, 2020Published online: March 18, 2020

P-Reviewer: Emara KM,Tangtrakulwanich BS-Editor: Ma YJL-Editor: AE-Editor: Liu MY

prosthesis design as the most likely parameter involved in developing PCS sincedifferent prosthesis designs are often the result of different parameters. Futurestudies should be directed at isolating individual prosthetic parameters ofprosthesis designs in order to determine what permutation of parameters is mostclosely associated with the development of PCS.

Key words: Patella clunk; Crepitation; Total knee arthroplasty; Patella catch; Prosthesisdesign; Insall-Salvati ratio

©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.

Core tip: Patellar clunk syndrome is the development of a fibrous nodule along theundersurface of the quadriceps tendon and proximal to the superior pole of the patellaafter a posterior-stabilized total knee arthroplasty. It can be diagnosed clinically by itsnamesake pathognomonic clunk when moving the knee from full flexion to extensionwith anterior knee pain or by radiograph, ultrasound, or magnetic resonance imaging.Ultimately, the etiology of patellar clunk syndrome is most dependent upon prosthesisdesign, which is largely dependent upon incorporate a reduced intercondylar box ratioand box width to reduce contact between the proximal patellar pole and the intercondylarbox.

Citation: Sequeira SB, Scott J, Novicoff W, Cui Q. Systematic review of the etiology behindpatellar clunk syndrome. World J Orthop 2020; 11(3): 184-196URL: https://www.wjgnet.com/2218-5836/full/v11/i3/184.htmDOI: https://dx.doi.org/10.5312/wjo.v11.i3.184

INTRODUCTIONTotal knee arthroplasty (TKA) is one of the most successful orthopedic proceduresperformed today[1-3]. Posterior stabilized TKA has long term survivorship thatsurpasses 90% at a 10 year minimum follow-up in several studies, but is occasionallycomplicated by a post-operative pathology called patellar clunk syndrome (PCS)[1].PCS is an uncommon complication following TKA that was first described by someresearcher and is associated almost exclusively associated with posterior stabilizeddesigns[2,3]. It has an estimated incidence of 0% to 20% in all primary total kneereplacements, depending on design[4-7]. The symptoms of patellar clunk can rangefrom painless catching of the knee to painful locking, leading to dissatisfaction of theknee replacement[2,3]. With appropriate identification of the problem, this conditioncan be relatively easy to treat with high levels of satisfaction[8].

PCS typically presents within, on average, the first 7.4 postoperative months[8].Symptomatic patella clunk is characterized by anterior knee pain secondary to painfullocking of the knee when going from full flexion to extension, followed by a painfulclunk as the knee fully straightens[3]. The pathoanatomy of patella clunk involves anaccumulation of scar tissue along the undersurface of the quadriceps tendon,proximal to the superior pole of the patella and patellar button[2]. As the knee flexes,the patella engages the trochlea of the implant. As the knee then extends, the knot ofscar tissue can become trapped in the femoral box, leading to locking of the knee mid-flexion. Additionally, the scar tissue nodule can impinge upon the intercondylarnotch, producing pain on extension. Forceful extension of the knee leads to the scartissue painfully disengaging from the box followed by an audible “clunk” or painfulsnap, typically visualized at 30-45 degrees from full extension[9].

The diagnosis is one that is made clinically and occasionally via imaging. Thepatella can be seen catching and releasing as the patient is asked to extend the kneefrom flexion (video sees https://vimeo.com/148540681). In addition to physical examand plain radiographs, magnetic resonance imaging and ultrasound can aid in thediagnosis and help guide treatment. magnetic resonance imaging has been used todemonstrate a fibrous soft tissue nodule proximal to the patella in 75% (9/12) ofpatients with suspected patellar clunk[10]. Plain radiographs can also help with theidentification of any loose bodies causing crepitus, and evaluate the position of thepatellar component. Ultrasound imaging has also been used in the evaluation anddiagnosis of PCS[11].

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Under the PICOS algorithm, we conducted a systematic review and meta-analysisof articles published on PCS after TKA to (1) characterize the etiology of PCS; (2)understand the outcomes and prevention of PCS; (3) clarify strengths and weaknessesof the current evidence; and (4) outline guidelines for future research.

MATERIALS AND METHODS

Eligibility criteriaFor the systematic review, we used the following inclusion criteria: (1) All patientswere above 18 years of age; (2) TKA as a primary procedure; and (3) PCS incidencewas evaluated as an outcome. These studies were restricted according to the followingstudy characteristics: (1) English language only; and (2) Original research. Exclusioncriteria were review articles, studies less than 5 participants, double publication ofdata. We did not include a date limitation as we wanted to survey the comprehensivebreadth of existing PCS literature rather than confine our search to modern,contemporary PCS literature.

Search strategy and information sourcesOur literature search strategy included PubMed (MEDLINE), Google Scholar, andCochrane for peer-reviewed full-length articles on PCS. The last search wasperformed in July, 2018. On-line literature search was conducted using MeSHkeyword search on PubMed (MEDLINE), Google Scholar, and Cochrane “(patella ORpatellar) AND (clunk OR catch OR crepitation)”. We also used the “relevant articles”feature to locate any potentially relevant studies. Using this search technique resultedin 505 non-duplicated articles (Figure 1).

Study selectionFollowing the research, two reviewers (SBS and QC) independently reviewed allarticles to evaluate their contribution to this study using the aforementioned eligibilitycriteria. We then excluded any articles not relevant to the characterization of PCSbased upon their content. Using eligibility criteria, we obtained 30 articles (Table 1, 1-30). Two articles were excluded because they were not in English. If necessaryinformation was not specified in the abstract, an additional screen was executed afterdata collection to evaluate the study’s contribution to this investigation. We obtainedthe full text if at least one of the reviewers judged a study to be eligible. We reviewedreference lists of included studies to identify additional studies. Reference listsyielded 3 additional studies (Table 1, 31-33). Definitions of pertinent metrics werecompiled in Table 2. Disagreements on inclusion were resolved by consensus. Neitherreviewer was blinded to any study characteristics including journal, contributingauthors, or affiliated institution (Figure 2).

Data items and extractionOnce studies were chosen, one reviewer (SBS) went through each articleindependently and consolidated the data in Table 1. Study quality was evaluatedusing sample size, study design, follow-up consistency, and analysis methods. Threeother reviewers (QC, WN, JS) verified the data collection and consolidationindependently. Data was collected on May 18th, 2018.

Risk of biasThe risk of bias in the selection of individual studies for inclusion in this investigationwas assessed by qualitative review initially based upon study quality and availabilityof existing studies pertaining to PCS from Table 1. After data consolidation,individual studies were evaluated through ROBIS, the risk of bias assessment tool forsystematic reviews. Results indicate that this systematic review has a low risk of bias(Table 3)[12].

RESULTSThe search for studies on factors that influence incidence of PCS post-TKA yielded 861citations; after screening for duplicates, 505 citations were included. After inclusionand exclusion criteria were applied to abstracts, 397 articles were excluded from thereview. 108 full-length manuscripts were obtained, at which point inclusion andexclusion criteria were applied, yielding 30 total articles for the review. Each referencelist of the final 30 articles were reviewed for robust inclusion of pertinent literaturewhich yielded an additional three articles. The pertinent findings, as they apply to this

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Figure 1

Figure 1 PRISMA flowchart of the systematic review.

systematic review, of these 33 manuscripts are found in Table 1. Risk of bias wasperformed using the ROBIS tool and the results indicated that the techniques andresults of the literature search qualified for a low risk of bias (Table 3).

EtiologiesThe abundance of scar tissue that forms on the undersurface of the quadriceps tendonleading to PCS is due to several factors (Table 1). Originally, theories suggested it wasdue to inadequate resection of synovium at the time of total knee arthroplasty[2,3].However, there is no data to support this as a leading cause. Other etiologies includecomponents of the native knee and prosthesis like femoral component design, jointline level and postoperative patellar positioning, but generally most researchers haveconcluded that the pathogenesis of PCS is multifactorial[5,6,8]. Dennis et al[5] notes thatrisk factors for PCS include shortened patellar length, smaller patellar components,decreased patellar composite thickness, increased patellar offset, smaller and flexedfemoral components, and thicker tibial polyethylene inserts. In fact, Hoops et al[6]

employed a control-matched computational model to evaluate tendo-femoral contactin patients with posterior-stabilized TKA. Using this model, the authors confirmedclinical findings that an increased patellar ligament length, flexed femoral component,lowered joint line, and larger patellar component all reduced the problematic contactnear the intercondylar notch. The most significant contributing factor to tendo-femoral contact was found to be patellar ligament length. Decreasing patellarligament length by two standard deviations (13 mm) away from the normal resultedin a large increase in contact area with intercondylar notch. Preexisting patella baja, asconfirmed by preoperative radiographs, may also increase the risk of postoperativePCS[9].

Surgeons can correct for this by reducing distal femoral resection, which willdecrease the tibial bearing thickness required to adequately tension the extension gapand effectively lower the joint line and decrease patella baja. Figgie et al[9] reportedthat a joint line level of 8 mm or less, a patellar height of 10 to 30 mm, and aneutral/posterior placement of the tibial prosthesis oriented to the center line of thetibia should result in improved outcome and reduced PCS incidence[9,13]. However,these three aforementioned conditions are only sufficient to reduce PCS, not eliminateit[10]. Similar to patellar height, a reduced patellar tendon length also predisposes anindividual to PCS, most likely since the reduction in either metric will increase thecontact between the quadriceps tendon and the superior intercondylar notch[4]. Assuch, most studies that concluded patellar height is correlated with PCS would alsoconcomitantly conclude patellar tendon length has the same relationship with PCS.Measurements such as the Insall-Salvati ratio and the location of the tibial tray mayinduce or prevent the incidence of PCS post-TKA. The Insall-Salvati ratio is defined asthe ratio of the patella tendon length to the length of the actual patella. As such, anInsall-Salvati ratio below 0.8 is considered “patellar baja”, whereas above 1.2 isconsidered patellar alta. Studies have demonstrated that low Insall-Salvati ratios arecontributory towards post-operative PCS (Table 1). Similarly, if the tibial tray is

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Table 1 Etiologies associated with development of patellar clunk syndrome: Comparison of published studiesa

Ref.

Postope-rativeKneeFlexion(degrees)

Prothes-esDesign

JointLineLevel

PatellarHeight

Insall-SalvatiRatio

Positionof TibialTray

Patellarthickne-ss

Patellartendonlength

Femoralcondyleoffset

Patellartilt

Posteriortibialslope

Resurfac-ing

Beight etal[40]

Notsignificant

N/A Significant Significant N/A N/A N/A N/A N/A N/A N/A N/A

Andersonet al[22]

N/A Significant N/A N/A N/A N/A N/A N/A N/A Significant N/A N/A

Pollock etal[20]

N/A Significant Notsignificant

Notsignificant

N/A N/A N/A N/A N/A N/A N/A N/A

Maloneyet al[27]

N/A Significant N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Yau etal[15]

N/A N/A Notsignificant

Significant Significant Significant N/A N/A N/A Significant N/A N/A

Ip et al[23] N/A Significant N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Schroer etal[28]

Significant Significant N/A Notsignificant

Notsignificant

N/A N/A N/A N/A Notsignificant

Notsignificant

N/A

Fukunagaet al[14]

Significant Significant N/A Notsignificant

Notsignificant

Notsignificant

N/A N/A N/A Significant N/A N/A

Dennis etal[5]

Notsignificant

N/A Notsignificant

Significant Significant Significant N/A Significant Significant Notsignificant

Notsignificant

N/A

Frye etal[4]

Significant Significant Notsignificant

Notsignificant

Notsignificant

N/A N/A N/A N/A Significant N/A N/A

Choi etal[8]

Notsignificant

Significant Notsignificant

N/A Notsignificant

N/A Notsignificant

N/A Notsignificant

Notsignificant

Notsignificant

Significant

Costanzoet al[1]

N/A N/A N/A Notsignificant

N/A N/A Significant N/A Significant N/A N/A N/A

Gholson etal[32]

Notsignificant

N/A Notsignificant

Notsignificant

Notsignificant

Notsignificant

Notsignificant

Notsignificant

Notsignificant

Notsignificant

Significant N/A

Peralta-Molero etal[29]

Significant N/A Notsignificant

Notsignificant

Notsignificant

Notsignificant

Notsignificant

N/A N/A Notsignificant

Notsignificant

N/A

Bae et al[41] N/A Significant Notsignificant

N/A Notsignificant

N/A N/A N/A N/A Significant N/A N/A

Toomey etal[42]

N/A Significant N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Martin etal[19]

Significant Significant N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Snir etal[43]

N/A Significant N/A N/A N/a N/A N/A N/A N/A N/A N/A N/A

Tang etal[21]

N/A Significant N/A N/A N/A N/A N/A N/A N/a N/A N/A N/A

Rajshekha-r et al[44]

N/A Significant N/A N/A N/A N/A N/A N/A N/A N/a N/A N/A

Figgie etal[9]

N/A N/A Significant Significant N/A Significant N/A N/A N/A N/A N/A N/A

Ip et al[45] N/A Significant N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Lonner etal[17]

N/A Significant Notsignificant

N/A Notsignificant

N/A N/A N/A N/A N/A N/A N/A

Shoji etal[25]

N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A Notsignificant

Ogawa etal[34]

N/A N/A N/A N/A N/A N/A N/A N/A N/A Significant N/A Significant

Hamiltonet al[31]

N/A N/A N/A N/A N/A N/A Significant N/A N/A N/A N/A N/A

Martin etal[19]

Significant Significant N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Agarwalaet al[2]

N/A Significant N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Shilling-ton et al[33]

N/A Significant N/A N/A N/A N/A N/A N/A N/A N/A N/A Significant

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McNabbet al[46]

N/A Significant N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Clarke etal[18]

N/A Significant N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Ranawatet al[26]

N/A Significant N/A Notsignificant

Notsignificant

N/A Notsignificant

N/A N/A N/A N/A N/A

Aglietti etal[16]

Notsignificant

Significant N/A Notsignificant

N/A N/A N/A N/A N/A Notsignificant

N/A Significant

aP = 0.05 for significance. N/A: Not available.

placed too anteriorly with respect to the tibia’s center line, PCS is more likely tooccur[13,14]. Yau et al[15] determined that PCS inflicted knees had a relative position of7.74 mm with respect to the patellar tendon as compared to 9.23 mm non-PCSinflicted knees, indicating that a neutral or posterior positioning of the tibial tray mayaid in the reduction of PCS.

Certain total knee designs appear more susceptible than others to PCS, most likelydue to their underlying differences in metrics (Table 2). First generation Insall-Burnstein prostheses have been adapted to decrease the incidence of PCS byresurfacing the patella and smoothened anterior edge to the trochlea[16]. Even so, theInsall-Burnstein II generated PCS in 4% of treated knees as compared to 0% by thefixed NexGen Legacy Posterior-Stabilized flex design[17]. The NextGen Legacy movedthe cam and post mechanism such that the trochlea would have more mobility andoriented the patellar groove obliquely, resulting in minimal to no PCS[18]. Othersfound the incidence of PCS to be higher (P < 0.001) in patients with the mobile Press-Fit Condylar Sigma Rotating Platform/RotatingPlatform-Flex Knee System (11 of 113knees, 9.7%), compared to fixed NexGen Legacy Posterior Stabilized-Flex design (6 of424 knees, 1.4%)[8]. The mobile Press-Fit Condylar has a larger intercondylar box ratiowhich is more likely to induce the fibrous nodule near the patella, resulting in PCS.The Attune prosthesis also demonstrated low incidence of PCS and is therefore aviable alternative to earlier generations since its smaller anterior flange andconcomitant intercondylar box ratio cause less clunk[19].

Furthermore, Pollock et al[20] and Agarwala et al[2] concluded that a significantlyhigher (P < 0.001) proportion of high-flex mobile bearing joints (15%) compared tofixed bearing joints (0%) develop PCS. Additionally, the incidence of PCS in AnatomicModular Knee Congruency implant, Anatomic Modular Knee-Posterior Stabilizedimplants and Press Fit Condylar Sigma-Posterior Stabilized implant was 13.5%, 3.8%,and 0%, respectively, indicating that a proximally positioned or wider femoral box ismore likely to induce PCS[20]. Yau et al[15] 2003 determined a significant incidence ofPCS (18.3%) when using the AMK posterior stabilized knee potentially due to ashallow femoral trochlea and more proximal and narrower intercondylar notch. Dueto the lack of a femoral box needed to accommodate the cam and post mechanism fora posterior stabilized design, cruciate retaining designs are typically not affected bythis condition with the exception of a few reports[18,21-23]. Posterior femoral condyleoffset may also be partially responsible for an increased incidence of PCS. Gopinathansuggests that such increasing condyle offset may cause an anterior shift of theintercondylar box and cause the intercondylar box to come into contact with thequadriceps tendon[13].

DISCUSSIONIn recent years, the dimensions of the intercondylar box has been implicated in a hostof PCS studies as contributory towards the development of PCS. For example, firstgeneration PS designs’ high transition zone from trochlear groove to intercondylarbox induced an apposition of the quadriceps tendon to the intercondylar box[9]. Assuch, post-operative complications such as synovial hyperplasia and patellar clunkand crepitus (PCC) would arise. Second and third generation PS designs attempted tocorrected for the large intercondylar box. Frye et al[4] demonstrated that PCS orpatella- femoral crepitation was evident in 12% of their 108 patients with aconventional, first- generation design, compared to no complication in the second-generation design with a deeper trochlear groove and smooth transition of theintercondylar box (0/136, P < 0.0001). Fukunaga et al[14] described this difference as theintercondylar box ratio, which is the intercondylar box height versus the anterior-posterior height of the femoral component. Studies suggest that an intercondylar boxratio less than 0.7 has, so far, shown elimination of PCS[24]. Anatomically, the smaller

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Table 2 Table 1 metrics defined

Postoperative knee flexion After surgery, the degree to which the knee can flex

Prosthesis design Several prosthesis designs can be implanted in a TKA

Joint line height Shortest distance between the fibular head and lateral femoral condyle on AP radiograph

Patellar height Measured as the perpendicular distance from the inferior pole of the patellar implant to the joint line of the prosthesis

Insall-Salvati ratio Ratio of the length of the patellar tendon to the length of the patella

Position of tibial tray Measured as the perpendicular distance of the tibial tray from the patellar tendon

Patella thickness The width of the patella (medial to lateral)

Patellar tendon length Length of the patellar tendon superior to inferior

Posterior tibial slope The degree to which the tibia is lateral to the perpendicular line drawn from the prosthesis

Patellar tilt Angle subtended by the equatorial line of the patella and the line connecting the anterior limits of the femoral condyles

Femoral condyle offset Distance between the lateral condyle and the vertical line parallel to the lateral edge of the femur

intercondylar box ratio decreases the likelihood the proximal pole of the patella willcome into contact with the anterior edge of the intercondylar box during flexion[25]. Inaddition to the intercondylar box ratio, the medial-lateral geometry of theintercondylar box itself has also been implicated in PCS. Pollock et al[20] determinedthat the PFC Sigma PS prostheses was more efficient than the AMK Congruency andAMK PS in reducing the width of the intercondylar box and therefore PCS. Similarly,Ranawat et al[26] concluded that by smoothening the sharp ridge of the intercondylargroove while maintaining a 0.85-0.87 intercondylar box ratio, PCS incidence could bereduced to 2%.

Another important component associated with PCS incidence is the degree of thepatient’s knee flexion. Some studies on PCS have also evaluated the extent of kneeflexion and concluded that each additional degree of knee flexion increased thechance of PCS by 4.2%[26]. Maloney et al[27] capitalized on this association between kneeflexion and PCS, stating that this ‘hyperflexion’ leads to the quadriceps tendon beingperturbed as it inserts on the patella and the development of the pathognomonicfibrous nodule near the patellar button.

In a study conducted by Schroer et al[28] with 747 TKA, the degree of postoperativeknee flexion was significantly associated with the development of patella clunk. Theutilization of a Vanguard PS femoral component (which is narrower and has arounded intercondylar notch transition than the Ascent), eliminated PCS even whenusing the MIS technique, as compared to the Ascent femoral component and the MIStechnique. Mean knee flexion at six weeks postoperatively in patients who developedpatella clunk was 124 degrees versus 117 for the knees that did not develop PCS (P =0.016). They hypothesized that the increased postoperative knee flexion furthered thedistance between the patella and femoral component, causing the soft tissueentrapment near the intercondylar notch. More recently, Peralta-Molero et al[29]

reviewed 570 primary TKAs using the Genesis II SPC TKA system with 6% of kneesdeveloping PCS. The authors found that the likelihood of developing PCS increasedby 4.2% with each degree of increased flexion. Other literature that studied Attuneposterior-stabilized prosthesis demonstrated a lower incidence of PCS and lowerpostoperative knee flexion as compared to PFC sigma prosthesis[19]. However, otherstudies have shown postoperative knee flexion to be an insignificant risk factor in thedevelopment of PCS (Table 1)[5,8].

Patellar thickness has also been implicated in the development of PCS. Thinnercomponents have been shown to increase the incidence of PCS by reducing the offsetof the quadriceps tendon from the superior portion of the trochlear groove[30].Additionally, Costanzo et al[1]. determined that patella thickness, preoperatively, doesrelate to increased incidence of PCS and suggested that it may lead to greaterbone/soft tissue resectioning, though this risk factor can be mitigated by improvedsurgical technique[1]. Hamilton et al[31] demonstrated this significant association bydemonstrating an increase in PCS with thinner patellas in 3655 TKAs. In fact,decreasing the thickness by more than 2 mm would increase the risk of developingPCS by 2.5, owing to a smaller distance between the extensor mechanism and femoralcomponent box. The importance of patella thickness is not well understood, however,as several other studies have concluded that patella thickness has minimal associationwith the incidence of PCS (Table 1)[8,26,29,32].

Increased posterior tibial slope has also been thought to contribute to thedevelopment of PCS, most notably since an increase in the flexion gap would increasethe level of tension placed on upon the quad mechanism. However, aside fromGholson et al[32], no other study has found a significant correlation between this metric

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Figure 2

Figure 2 Graphical representation of Patellar clunk syndrome etiology summarized from Table 1. PCS:Patellar clunk syndrome.

and PCS incidence.Patellar tilt, defined as the angle subtended by the equatorial line of the patella and

the line connecting the anterior limits of the femoral condyles, has also beenimplicated in the development of PCS[14,15]. Fukunaga et al[14], using logistic regressionanalysis, determined that incidence of PCS would increase 1.27 for every degreeincrease in patellar tilt. The prosthesis design is also thought to impact the stability ofpatellar tracking and therefore can influence PCS development[15].

The relationship between patellar resurfacing and incidence of PCS has not beendefinitely confirmed in the literature. For example, Shoji et al[25] concluded that in aseries of 647 TKAs, there was no difference in incidence of PCS between the patellarresurfaced group and native patella group. Still, some orthopedists recommendpatellar resurfacing to reduce PCS due to its ability to create more space between thepatella and the femoral box[33]. Ogawa et al[34] studied 84 knees from 69 patients andconcluded that PCS was significantly higher in native patellas, owing to the increasedpatellar tilt and medial positioning of the patella to the femur in resurfaced patellas.While patellar resurfacing/retention was found to significantly increase the incidenceof PCS (4/14 vs 56/752 in non-PCS group, P = 0.003), this study only included 14knees that were resurfaced as compared to 752 that were not resurfaced[8].

TreatmentOnce a diagnosis of patella clunk is established, it can be effectively treated. Sincemechanical catching of scar tissue causes pain, non-surgical means are not the mostsuccessful at treating the condition. That being said, before surgical intervention,conventional non-surgical intervention is limited to lower extremity quadriceps andhamstring strengthening[1-4].

In surgery, typically the lesion is debrided arthroscopically without needing toopen the knee joint. The patient is set up as usual for knee arthroscopy. The patient isplaced supine on the operating table without breaking the foot of the bed. A side postor leg holder is not necessary, and a tourniquet may be used at the discretion of thesurgeon. The knee is approached with a superolateral inflow/viewing portal, wherethe undersurface of the quad tendon can be inspected, as well as the patella directlyviewed engaging the trochlea. The offending lesion is typically identified as a mass ofscar tissue proximal to the superior pole of the patella, near the patellar button. Asuperomedial working portal is then made under direct visualization via outside-intechnique. The synovium and scar can then be debrided with a motorized shaver,taking care to not damage the prosthetic surfaces or underlying quadriceps tendon.Once a thorough debridement has been completed, the knee is then drained of fluidand taken through a range of motion to ensure there are no further mechanical blocksto extension. The knee is wrapped in an ace bandage and allowed to engage in fullactivity post-op (video sees https://vimeo.com/148540681).

Messieh[35] described surgical treatment of PCS using a limited open arthrotomyunder local anesthesia in two patients. The benefits included subjective improvedpatient satisfaction with patient’s ability to actively move the knee duringdebridement to ensure adequate resection of the nodule and minimal knee swellingassociated with arthroscopic distension leading to faster recovery. This, however, isnot the standard of care treatment in PCS, and most patients would prefer to be undergeneral or spinal anesthesia. It is however an option for patients with

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Table 3 ROBIS Tool for assessing risk of bias in systematic review

Study eligibilitycriteria

Identification andselection of studies

Data collection andstudy appraisal Synthesis findings Risk of bias in the

review

PCS etiology Yes Yes Yes Yes A. Yes

Systematic review B. Yes

C. No

Overall: Low

PCS: Patellar clunk syndrome.

contraindications to general anesthesia.Sekiya et al[36] described a more recent surgical intervention for PCS using the

conventional arthroscopic debridement procedure to excise the offending fibrousnodule. In 46 separate generally anesthetized patients, anterolateral, anteromedial,and proximal superomedial portals were set up, with the first used as the viewingportal. After the working probe was inserted into the anteromedial compartment, anelectric shaver was used to remove any scar tissue on the medial or lateraltibiofemoral joint, patellofemoral joint, intercondylar notch, or posterior aspect of theinfrapatellar fat pad. One day post-operation, the patient was allowed to bear fullweight.

OutcomesArthroscopic treatment of PCS generally has high patient satisfaction rates andimprovement of pain and function following surgery for patella clunk. Dajani et al[3]

reported on 15 patients with symptomatic patellar clunk treated with arthroscopicdebridement. Of this series, there was a significant reduction of pain from 6 to 1 in theimmediate post-operative period. At an average of 41 months follow-up (range, 24-75mo), average Knee Society Score (KSS) increased from 76 to 92, and KSS functionincreased from 71 to 79. Koh et al[37], also reported a positive response to arthroscopicdebridement. Twelve knees were reported with minimum one year follow-up.Average KSS increased from 63.8 to 90.9, with KSS function increasing from 65.4 to90.4. Of note, there was no significant improvement in rising from a chair or stairclimbing in patients with patellar clunk treated with arthroscopic synovectomy.Gholson et al[32] performed a similar study in which they scrutinized the work of onesurgeon and concluded that KSS improved to 92.4 and WOMAC to 82.9. All patientsin the study were at least moderately satisfied; however, 17% required a repeatarthroscopic debridement, after which, there were no further complications of PCS.Occasionally, arthroscopic debridement to eliminate PCS may not return the patientto normal range of motion. A recent study suggested that even post-PCS, patients canstill suffer from PCS; for example, a case of prosthetic loosening of the femoralcomponent, caused noticeable gait disturbance post-PCS[36]. Such a post-operativecomplication necessitated additional prosthesis revision surgery, after which nocomplications or symptoms manifested two years thereafter.

PreventionMain prevention methods include utilization of femoral components with reducedintercondylar box ratio (such that the trochlear groove is more distal and posterior),avoidance of patella baja, proper surgical technique during TKA with prevention ofpatella over-resection, and debridement of fibrosynovial tissue at time of TKA[29].

Additionally, by initiating the entry site for the intramedullary distal femoralcutting guide jig more anteriorly, a surgeon can prevent femoral component flexionwhich may ultimately lead to the fibrous nodule ‘catching’ on extension from a flexedposition. Yau et al[15] additionally mentions that excessive surgical trauma and failureto debride the suprapatellar synovium may be an important, but not underlyingetiology of the fibrosis in PCS. Therefore, careful surgical technique to avoid excessivetrauma and synovial disruption can reduce the possibility of PCS. Fukunaga et al[14]

concluded that a femoral component design that includes a raised lateral flange,deepened trochlear groove, and side-specific femoral components can help reduce,but not eliminate, PCS. While posterior-stabilized TKA has been associated with ahigher incidence of PCS, both cruciate retaining and substituting TKA should notnecessarily be deemed preventative of PCS.

According to Yau et al[15], the neutral or posterior arrangement of the tibial tray mayreduce the incidence of PCS as well. Perhaps most logically, the attempted reductionin etiology of PCS should reduce the incidence of the post-operative complication.

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Conrad et al[38] advised surgeons to avoid overresection of the patella which was thencorroborated by Meftah et al[30] who found a reduction of PCS incidence from 40% to21% by avoiding over-resection and reducing the quantity of components in thepatellofemoral joint. Conrad et al[38] also reports that the excision of the fibrosynovialtissue at the superior pole of the patella may also reduce the chance that the sametissue catches when moving from knee flexion to extension – however, as previouslynoted, this is controversial.

Finally, some evidence suggests that resurfacing of the patella can decrease andprevent the development of PCS. Through resurfacing, the patella will be less likely tocome into contact with the proximal edge of the femoral box[33].

Limitations/guides for future researchThis study comprehensively reviews the existing literature on the etiology of PCS. Toour knowledge, there are no systematic reviews under PRISMA guidelines that seekto determine the etiology of PCS making this study unique in its approach andconclusions. However, this study does have its limitations. This systematic reviewused three large databases to extract literature from, though some suggest the use ofEMBASE and Web of Science in addition to Google Scholar, MEDLINE, and Cochranefor comprehensive, yet efficient review of the literature[39]. Furthermore, while theROBIS risk bias assessment tool yielded a low risk of bias, the use of statisticalsignificance in the results of the included literature presents some degree of biaswithin the conclusions of this systematic review (Table 3).

The literature on the development of PCS presents limitations in terms of pureanalysis of etiology and general heterogeneity. Many studies were constructed toevaluate prosthesis design on complication rate and prognosis post-TKA, though onlyincluded PCS as a small subset of a series of post-TKA complications. As a result, it isunclear the degree to which these studies emphasized and scrutinized the incidenceof PCS as compared to overall outcome following TKA. Additionally, studies on theetiology of PCS are heavily biased towards the study of prosthesis design. Whileprosthesis design is the product of the more fundamental parameters of Table 1, thesestudies did not examine the effect of those fundamental parameters on the incidenceof PCS. Without isolating each individual parameter, reviews of the current evidencewill be limited as it will be difficult to determine if multiple, one or none of theparameters are responsible for the development of PCS.

Patella clunk is an uncommon complication following total knee arthroplasty witha posterior stabilized design. Herein, we have determined that the formation ofpatellar clunk has a multifactorial etiology, including postoperative knee flexion, jointline level, prosthesis design, patella thickness, tibial tray positioning, patellar tilt,Insall-Salvati ratio, femoral condyle offset, and posterior tibial slope. In spite of amultifactorial etiology, the treatment is relatively straightforward and can provide thepatient a high satisfaction rate postoperatively. While diagnosed clinically, anypainful total knee replacement should be thoroughly worked up for other causes ofpain, including infection, trauma, loosening and instability. Further studies shouldaim at examining isolated parameters that characterize prosthesis design to morespecifically understand what parameters of prosthesis design contribute todevelopment of PCS.

ARTICLE HIGHLIGHTSResearch backgroundPatellar clunk syndrome (PCS) is a postoperative complication following total knee arthroplastythat clinically presents as anterior knee pain that is particularly painful when going from fullflexion to extension. The pathoanatomy of PCS involves the accumulation of scar tissue along theundersurface of the quadriceps tendon, proximal to the superior pole of the patella. Thediagnosis of PCS can often be made clinically, but radiographic adjuncts such as ultrasound andmagnetic resonance imaging have been used with success. Unfortunately, there is no currentliterature that evaluates multiple metrics of the native knee and prosthesis to determine whatmetric is most responsible for the development of PCS.

Research motivationThe main topics of the current study are (1) characterizing and analyzing metrics implicated inthe pathogenesis of PCS; and (2) defining contemporary management, treatment, andpreventative algorithms for PCS. The current study aims to elucidate how various prosthesis andgeometries of native knee can cause PCS or prevent it from occurring, which are poorlysummarized and defined in the literature currently.

Research objectivesThe main objective of the current study is to evaluate current evidence and characterize a

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reasonable etiology for the development of PCS. A secondary objective of the current study is tobetter understand the various treatment and preventative heuristics implemented to managePCS.

Research methodsA systematic review of clinical research studies from PubMed, Google Scholar, and Cochranewas conducted, as these databases were felt to be representative of peer-reviewed scholarly workand well encompassed literature surrounding PCS. Each study was analyzed and results werecompiled in designated tables with a predetermined list of metrics and its correspondingincidence of PCS. Details regarding prevention, treatment, and management were also extractedat this time.

Research resultsA total of 30 articles were identified through the primary search, with an additional 3 includedfrom reference lists of the primary search. Results indicate that prosthesis design was the mostfrequently cited metric as contributory towards PCS. The prosthesis design is often acombination of multiple metrics and, therefore, we conclude that the etiology of PCS ismultifactorial. A reduced intercondylar box ratio and box width has been consistently shown toreduce PCS.

Research conclusionsProsthesis design is the main metric associated with the etiology of PCS, though because theprosthesis design incorporates several other metrics included in our analysis, the etiology of PCSis multifactorial. Later prosthesis designs that incorporate a reduced intercondylar box ratio andbox width can reduce development of PCS. Preventative strategies involve using latergenerations of prosthesis especially those that incorporate a reduced intercondylar box ratio.

Research perspectivesOverall, this study was able to confirm the etiology of PCS as well as provide insight intotreatment methods to prevent this postoperative complication. Nevertheless, future studiesshould aim to isolate individual metrics of prosthesis design to more specifically determinewhich metric is most responsible for the development of PCS. Higher level randomized controltrials should also be conducted to generate additional evidence to improve knee maneuverabilityand function post-total knee arthroplasty.

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24 Niikura T, Tsumura N, Tsujimoto K, Yoshiya S, Kurosaka M, Shiba R. Patellar clunk syndrome afterTKA with cruciate retaining design: a report of two cases. Orthopedics 2008; 31: 90 [PMID: 19292148DOI: 10.1016/j.asmart.2017.12.001]

25 Shoji H, Shimozaki E. Patellar clunk syndrome in total knee arthroplasty without patellar resurfacing. JArthroplasty 1996; 11: 198-201 [PMID: 8648316 DOI: 10.1016/s0883-5403(05)80017-8]

26 Ranawat AS, Ranawat CS, Slamin JE, Dennis DA. Patellar crepitation in the P.F.C. sigma total kneesystem. Orthopedics 2006; 29: S68-S70 [PMID: 17002154 DOI: 10.1097/00006416-200609000-00002]

27 Maloney WJ, Schmidt R, Sculco TP. Femoral component design and patellar clunk syndrome. ClinOrthop Relat Res 2003; (410): 199-202 [PMID: 12771831 DOI: 10.1097/01.blo.0000063606.67412.96]

28 Schroer WC, Diesfeld PJ, Reedy ME, LeMarr A. Association of increased knee flexion and patella clunksyndrome after mini-subvastus total knee arthroplasty. J Arthroplasty 2009; 24: 281-287 [PMID:18534476 DOI: 10.1016/j.arth.2007.10.005]

29 Peralta-Molero JV, Gladnick BP, Lee Y, Ferrer AV, Lyman S, González Della Valle A. PatellofemoralCrepitation and Clunk Following Modern, Fixed-Bearing Total Knee Arthroplasty. J Arthroplasty 2014;29: 535-540 [PMID: 242238824 DOI: 10.1016/j.arth.2013.08.008]

30 Meftah M, Ranawat AS, Ranawat CS. The natural history of anterior knee pain in 2 posterior-stabilized,modular total knee arthroplasty designs. J Arthroplasty 2011; 26: 1145-1148 [PMID: 21277160 DOI:10.1016/j.arth.2010.12.013]

31 Hamilton WG, Ammeen DJ, Parks NL, Goyal N, Engh GA, Engh CA. Patellar Cut and CompositeThickness: The Influence on Postoperative Motion and Complications in Total Knee Arthroplasty. JArthroplasty 2017; 32: 1803-1807 [PMID: 28108171 DOI: 10.1016/j.arth.2016.12.033]

32 Gholson JJ, Goetz DD, Westermann RW, Hart J, Callaghan JJ. Management of Painful Patellar Clunk andCrepitance: Results at a Mean Follow-Up of Five Years. Iowa Orthop J 2017; 37: 171-175 [PMID:28852353]

33 Shillington M, Farmer G. Patellofemoral crepitus following lcs rps total knee arthroplasty without patellaresurfacing. Orthop Proceedings 2012; 94-B: 19-19

34 Ogawa H, Matsumoto K, Akiyama H. Effect of Patellar Resurfacing on Patellofemoral Crepitus inPosterior-Stabilized Total Knee Arthroplasty. J Arthroplasty 2016; 31: 1792-1796 [PMID: 26948175 DOI:10.1016/j.arth.2016.01.023]

35 Messieh M. Management of patellar clunk under local anesthesia. J Arthroplasty 1996; 11: 202-203[PMID: 8648317 DOI: 10.1016/S0883-5403(05)80018-X]

36 Sekiya H, Takatoku K, Takada H, Kanaya Y, Sasanuma H. Painful knee after total knee arthroplasty is nota frequent complication and could be treated by arthroscopic debridement. Orthop Proceedings 2016; 98-B: 152-152

37 Koh YG, Kim SJ, Chun YM, Kim YC, Park YS. Arthroscopic treatment of patellofemoral soft tissueimpingement after posterior stabilized total knee arthroplasty. Knee 2008; 15: 36-39 [PMID: 17897831DOI: 10.1016/j.knee.2007.08.009]

38 Conrad DN, Dennis DA. Patellofemoral crepitus after total knee arthroplasty: etiology and preventivemeasures. Clin Orthop Surg 2014; 6: 9-19 [PMID: 24605184 DOI: 10.4055/cios.2014.6.1.9]

39 Bramer WM, Rethlefsen ML, Kleijnen J, Franco OH. Optimal database combinations for literaturesearches in systematic reviews: a prospective exploratory study. Syst Rev 2017; 6: 245 [PMID: 29208034DOI: 10.1186/s13643-017-0644-y]

40 Beight JL, Yao B, Hozack WJ, Hearn SL, Booth RE. The patellar "clunk" syndrome after posteriorstabilized total knee arthroplasty. Clin Orthop Relat Res 1994; (299): 139-142 [PMID: 8119008 DOI:https://doi.org/10.1097/00003086-199402000-00018]

41 Bae DK, Baek JH, Yoon KT, Son HS, Song SJ. Comparison of patellofemoral outcomes after TKA usingtwo prostheses with different patellofemoral design features. Knee Surg Sports Traumatol Arthrosc 2017;25: 3747-3754 [PMID: 27511217 DOI: 10.1007/s00167-016-4264-1]

42 Toomey SD, Daccach JA, Shah JC, Himden SE, Lesko JP, Hamilton WG. Comparative Incidence ofPatellofemoral Complications Between 2 Total Knee Arthroplasty Systems in a Multicenter, ProspectiveClinical Study. J Arthroplasty 2017; 32: S187-S192 [PMID: 28600108 DOI: 10.1016/j.arth.2017.04.014]

43 Snir N, Schwarzkopf R, Diskin B, Takemoto R, Hamula M, Meere PA. Incidence of patellar clunksyndrome in fixed versus high-flex mobile bearing posterior-stabilized total knee arthroplasty. JArthroplasty 2014; 29: 2021-2024 [PMID: 24961894 DOI: 10.1016/j.arth.2014.05.011]

44 Rajshekhar KT, Kumar MN, Venugopal P, Chandy T. Patellar clunk in total knee arthroplasty using

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modified Sigma posterior stabilized femoral component. J Clin Orthop Trauma 2014; 5: 211-214 [PMID:25983500 DOI: 10.1016/j.jcot.2014.07.013]

45 Ip D, Wu WC, Tsang WL. Comparison of two total knee prostheses on the incidence of patella clunksyndrome. Int Orthop 2002; 26: 48-51 [PMID: 11954850 DOI: 10.1007/s00264-001-0316-2]

46 McNabb DC, Dennis DA, Jennings JM, Daines B, Laz P, Kim RH. Implant Design and Effects onPatellofemoral Crepitus. J Knee Surg 2017; 30: 863-871 [PMID: 28114703 DOI:10.1055/s-0036-1597976]

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W J O World Journal ofOrthopedics

Submit a Manuscript: https://www.f6publishing.com World J Orthop 2020 March 18; 11(3): 197-205

DOI: 10.5312/wjo.v11.i3.197 ISSN 2218-5836 (online)

CASE REPORT

Atraumatic groin pain secondary to an aneurysmal bone cyst: Acase report and literature review

Colum Downey, Aisling Daly, Alan P Molloy, Brendan J O’Daly

ORCID number: Colum Downey(0000-0001-6594-5732); Aisling Daly(0000-0002-7768-1487); Alan Molloy(0000-0001-5614-2241); BrendanO'Daly (0000-0003-4211-202X).

Author contributions: Downey Cand Daly A performed researchand wrote the case report. MolloyAP and O’Daly BJ researched thetopic and provided direction andcritical analysis of the case report.

Informed consent statement:Informed written consent wasobtained from the patient forpublication of this report and anyaccompanying images.

Conflict-of-interest statement: Theauthors declare that they have noconflict of interest.

CARE Checklist (2016) statement:The authors have read the CAREChecklist (2016), and themanuscript was prepared andrevised according to the CAREChecklist (2016).

Open-Access: This article is anopen-access article that wasselected by an in-house editor andfully peer-reviewed by externalreviewers. It is distributed inaccordance with the CreativeCommons AttributionNonCommercial (CC BY-NC 4.0)license, which permits others todistribute, remix, adapt, buildupon this work non-commercially,and license their derivative workson different terms, provided theoriginal work is properly cited andthe use is non-commercial. See:http://creativecommons.org/licenses/by-nc/4.0/

Colum Downey, Brendan J O’Daly, Department of Trauma and Orthopaedics, TallaghtUniversity Hospital, Dublin 9, Ireland

Aisling Daly, Department of Medicine, Trinity College Dublin, Dublin 2, Ireland

Alan P Molloy, Department of Trauma and Orthopaedics, St. Vincent’s University Hospital,Dublin 4, Ireland

Corresponding author: Colum Downey, MBBS, MCh, BSc, MSc, MRCS, Doctor, Departmentof Trauma and Orthopaedics, Tallaght University Hospital, Dublin 9, Ireland.columdowney@gmail.com

AbstractBACKGROUNDBone lesions can present the multi-displinary team with a challenge by way ofdiagnosis as some lesions share many radiological and histologicalcharacteristics. Giant cell tumours of the bone (GCTB) are relatively common,benign bone tumours. Aneurysmal bone cysts (ABC) are less common benignosteolytic lesions that are histologically similar to GCTBs but produce blood filledcavities. Both GCTBs and ABCs are locally aggressive and are typically found onmeta-epiphyseal regions of long bones with pelvic tumours being less common.

CASE SUMMARYA 17-year old female presented with atraumatic right groin pain and was initiallydiagnosed with a GCTB on the right superior pubic ramus of the pelvis. Thepatient was treated successfully with a wide excision, curettage and bone graftand underwent open reduction and internal fixation of the right hemi-pelvis.Following further intra-operative histological investigations, the lesion wasdiagnosed as an ABC.

CONCLUSIONThis patient has had an uncomplicated post-operative course, has returned tocomfortable weight bearing and will be reviewed for minimum 5 yr in the out-patient setting to monitor for reoccurrence.

Key words: Pelvic; Tumour; Aneurysmal bone cyst; Giant cell tumour; Open reductioninternal fixation of pelvis; Case report

©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.

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Manuscript source: Unsolicitedmanuscript

Received: September 16, 2019Peer-review started: September 16,2019First decision: October 13, 2019Revised: November 3, 2019Accepted: January 13, 2020Article in press: January 13, 2020Published online: March 18, 2020

P-Reviewer: Matcuk GR, Leung PCS-Editor: Wang LYL-Editor: AE-Editor: Liu MY

Core tip: We hereby present the successful management of a young female whopresented with atraumatic groin pain. This patient was ultimately diagnosed with ananeurysmal bone cyst of the superior pubic ramus and underwent wide-excision,curettage, bone grafting and open reduction internal fixation of her right hemi-pelvis.This patient is currently mobilising comfortably and is being monitored in the out-patientsetting for recurrence.

Citation: Downey C, Daly A, Molloy AP, O’Daly BJ. Atraumatic groin pain secondary to ananeurysmal bone cyst: A case report and literature review. World J Orthop 2020; 11(3): 197-205URL: https://www.wjgnet.com/2218-5836/full/v11/i3/197.htmDOI: https://dx.doi.org/10.5312/wjo.v11.i3.197

INTRODUCTIONGiant cell tumours of the bone (GCTB) are histologically benign neoplasms thataccount for approximately 20% of all benign bone tumours[1]. Aneurysmal bone cyst(ABC) are less common, expansile, osteolytic lesions that can produce blood filledcavities[2]. These entities can be difficult to diagnose and require radiological andhistological investigations to differentiate one from the other. Although both benign,GCTBs and ABCs can be locally aggressive. They can both affect the entire skeleton,but they are more likely to occur in the metaphysis of long bones[1,2] . ABCs may beprimary neoplasms or they may occur secondary to neoplasms such as giant celltumours, osteosarcomas and chondroblastomas[3]. Management of GCTBs and ABCsare typically surgical with a combination of either intra-lesional curettage, wideresection and bone grafting employed depending on the location and extent of theneoplasm. We report the case of a 17-year old female with, what was primarilydiagnosed as a giant cell tumour of the pelvis. The patient was treated surgically withwide excision, curettage and bone graft as well as open reduction and internal fixationof the right hemi-pelvis. Following analysis of intra-operative tissue specimens, thepatient was diagnosed with an ABC following specialist histopathological input.

CASE PRESENTATION

Chief complaintA 17-year old female presented to her general practitioner with a 4-mo history of painin the right groin.

History of presenting illnessThis symptom was initially described by the patient as similar to a groin strainpreviously experienced playing sports and the patient had discomfort on ambulation.There was no history of preceding trauma or sports injury. This pain progressed inseverity and began to wake the patient at night. The patient had no associated historyof fevers, rigors, shortness of breath, fatigue or weight loss.

History of past illnessThe patient had no significant history of past illness.

Personal and family historyThis young female had a normal developmental history, had received all routinevaccinations and had a typical history of childhood infections. There was nosignificant family history of any medical conditions/illnesses.

Physical examinationOn examination, the patient had non-irritable, normal range of motion of both hipjoints. She mobilised with an antalgic gait and the pain increased on single leg stanceusing the right lower limb.

Laboratory examinationsThis patient had routine bloods including complete blood count, basic metabolicpanel, c-reactive protein and erythrocyte sedimentation rate. These results did not

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reveal any abnormalities.

Imaging examinationsThe patient had X-ray imaging of her pelvis (Figure 1, anterior osterior pelvis andFigure 2, frog-leg lateral right hip) which showed an aggressive osseous lesion in theright superior pubic ramus. The patient was referred for specialist orthopaedicopinion and a computed tomography-guided biopsy was undertaken (Figure 3). Thepatient subsequently had magnetic resonance imaging (Figures 4 and 5) whichshowed an expansile mass arising from the right parasymphyseal bone into the rightsuperior pubic ramus. There was significant effacement and thinning of the adjacentcortex without bony destruction. Following interpretation of the above imaging andinitial biopsy, the patient was preliminarily diagnosed with giant cell tumour of theright superior pubic ramus and following a multi-disciplinary team approach, thepatient was scheduled for excision, curettage and grafting of the right superior pubicramus and open reduction and internal fixation of the right hemi-pelvis.

TREATMENT

SurgeryThe patient was positioned supine and an approximately 10 cm Pfannenstiel incisionwas performed. The Anterior Intra-Pelvic approach was utilised to expose the rightsuperior pubic ramus. The corona mortis vessel (anastomosis between the obturatorand the external iliac or inferior epigastric arteries or veins) were visualised andligated to optimise prophylactic management of haemostasis. This step assisted thesurgical team in minimising intra-operative blood loss and following measurement ofsuction and swab weights, the estimated blood loss was < 300 ccs. The lesion wasadequately exposed (Figure 6) and a window (approximately 1 cm × 5 cm) wasexcised to permit curettage of the right superior pubic ramus using a long curette(Figure 7). The lesion was gelatinous in texture and the periosteum surrounding thelesion was left intact. A commercially available bone graft (30 cc, Vitoss Scaffold,Stryker, USA) was packed within the periosteal sleeve (Figure 8). A 10-hole curvedpelvic plate (Radius 88°, Stryker, USA) was utilised to stabilise the pelvis postexcision, curettage and grafting of the patient’s lesion (Figure 9).

FINAL DIAGNOSISLocal histological examination of the excised tissue failed to confirm a tissue diagnosisand a differential diagnosis of (1) GCTB; (2) ABC; (3) giant cell rich osteosarcoma; (4)“brown” tumour; and (5) non-ossifying fibroma was reported. The tissue material wasforwarded to the United Kingdom’s National Sarcoma Specialist Centre (RoyalNational Orthopaedic Hospital, Stanmore, UK) for a second opinion. The sectionsshowed (1) fragments of cystic osteoclast-rich tumour composed of blandmononuclear stromal cells; (2) coiled fragments of cystic wall containing fibrino-osteoid seam; (3) patches of basophilic calcified tissue; (4) numerous fragments ofnormal articular cartilage admixed with the tumour; and (5) the tissues were negativefor K36M and G34W tumour markers. This specialist histopathology unit diagnosedthe lesion as an ABC with no evidence of malignancy.

OUTCOME AND FOLLOW-UPThe patient was mobilised using crutches on post-operative day 1 with partial weight-bearing of her right lower limb. Following satisfactory mobilisation withphysiotherapy and optimal pain control, the patient was safely discharged home onpost-operative day 4. Partial weight-bearing was undertaken for 6 wk withprogression to full weight-bearing following this. The patient has been followed upfor 6 mo post-operatively, has progressed to full weight-bearing and is symptom free.X-rays of this patient’s pelvis (Figure 10) confirm satisfactory maturation of the bonegrafted site and satisfactory position of internal fixation. The patient will be followedin the out-patient setting for next 5 yr minimum.

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Figure 1

Figure 1 Pre-operative anteroposterior pelvis.

DISCUSSIONWe presented a case of a young female patient who presented with a 4-mo history ofatraumatic right groin pain and underwent a series of radiological and histologicalinvestigations. This patient was preliminarily diagnosed with a GCTB but wasultimately diagnosed as having an ABC within her right superior pubic ramus. Thedifficulty in achieving the final diagnoses was secondary to the fact that both GCTBand ABC share a number of overlapping features.

GCTBs are histologically benign but locally aggressive neoplasms[1] and account forapproximately 20% of benign bone tumors and approximately 5% of all bone tumors(malignant and benign)[4]. GCTBs have a large biological spectrum ranging from latentbenign to highly recurrent[1]. In rare cases (1%-6%), pulmonary metastasis is seen[5,6].GCTBs have a peak onset at ages 21-40, while females have a greater incidence(male:female, 1:1.4)[7]. Pelvic GCTBs exhibit a marginally more pronounced male tofemale incidence ratio of 1:1.7[8]. GCTBs occur predominantly at the meta-epiphysealarea of long bones (75%-90%), with the distal femur being the most common site,followed by the proximal tibia, distal radius, sacrum and proximal humerus[1].Atypical sites of GCTBs include the vertebral bodies, the hands, patella and talus[1].GCTBs of the pelvis account for just 1.6%-6.1% of all GCTBs[8] and when they dooccur, are most likely in the acetabular area followed by the iliac and the ischiopubicareas[8,9].

Historically, ABCs were considered to be a variant of giant cell tumours and wereinitially described in 1941 by Jaffe et al[10]. The microscopic appearances of the twolesions are sometimes dramatically similar, and they are occasionallyindistinguishable, explaining the preliminary diagnosis of a GCTB[11]. ABCs are lesscommon, highly vascularised, osteolytic lesions. They are largely seen in childhoodand young adulthood, with 90% occurring in patients under 30[12]. ABCs, similarly toGCTBs, are typically located on the metaphysis of long bones, while pelvic ABCsconstitute half of flat bone ABCs. ABCs may arise as a primary neoplasm (66%) orsecondary to neoplasms (33%) such as GCTBs, os teosarcomas andchondroblastomas[3]. GCTBs are the preceding lesion of secondary ABCs in 19%-39%of cases[11]. Pathogenesis of primary ABCs is unclear although historically it wasthought to result from a local circulatory disturbance leading to markedly increasedvenous pressure and the development of a dilated and enlarged vascular bed withinthe affected bone area[13]. However, more recent studies have proposed a hereditaryfactor[14].

Radiologically, GCTBs are characterised by (1) erratic and lytic lesionsdemonstrating a “soap bubble” appearance; (2) a lack of internal calcification; and (3)cortical thinning. Other features such as (4) cortical penetration; (5) periostealreaction; and (6) pathological fractures can also be shown. ABCs can share a numberof these features, therefore magnetic resonance imaging (MRI) is vital to aid diagnosis.In GCTBs, MRI typically demonstrates low to intermediate signal using T1 sequenceand high signal using T2 signal intensity. Using MRI, ABCs typically demonstrate (1)an expansile appearance with multi-septated cysts; (2) fluid-fluid levels/solidcomponents; and (3) thin-walled margins[15]. The presence of fluid-fluid levels mayalso be seen in giant cell tumors of the bone (GCTs), amongst other lesions[15]

(chondroblastoma, simple bone cysts and telangiectatic osteosarcoma), thereforehistological examination is vital.

Histologically, GCTs are determined using the following features forcharacterisation: (1) Numerous osteoclast-like giant cells uniformly distributed; (2)

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Figure 2

Figure 2 Frog-leg lateral view right hip.

Presence of spindle and round/oval mononuclear cells; (3) Highly vascular stroma;(4) Necrosis; and (5) Vascular invasion may be present[16]. Separately, ABCs arecharacterised by (1) large cystic spaces filled with blood separated by fibrous septa; (2)cysts and septa bordered by histiocytes, myofibroblasts and fibroblasts; (3) variablemitotic figures/haemosiderin; (4) absent atypia; and (5) clusters of osteoclast-likemultinucleated giant cells[17]. Other options are available to aid diagnosis includingnext generation sequencing, fluorescence in situ hybridisation analysis and othercytogenetic examinations[18].

Intralesional curettage accompanied by reconstruction of the residual defect bybone graft or cementing is an appropriate surgical procedure for ABCs. A high-powerburr has been recommended to optimise the curettage and reduce the risk ofrecurrence[19]. This method strikes the greatest balance between tumour removal andmaintenance of functionality. Recurrence rates for this method are approximately16%-45%[20]. The use of adjuvants such as phenol, local toxins or filling withpolymethylmethacrylate have been shown to reduce recurrence rates postcurettage[21]. Due to their infrequent occurrence, there is no management guideline onthe optimal surgical protocol for the treatment of pelvic ABCs. The tumour site has acritical influence on treatment. Complications, particularly with wide resection, arecommon (20%), but studies show a low overall mortality rate (3.2%)[8]. Although localrecurrence of pelvic ABCs are expectedly more common in patients who undergointralesional curettage alone[8], wide resection is primarily done where there isextensive bone destruction, joint preservation is impossible, recurrent disease orbiologically more aggressive tumours[20,22]. In this case, wide resection was deemednecessary due to the extent of the bone destruction.

Due to their high level of vascularization, surgical adjuncts such as selective arterialembolism may be employed as a primary treatment of ABCs that are difficult toaccess such as those of the pelvis[2]. Successful embolization of an ABC has beenshown to result in progressive ossification within 2-4 mo of initial embolization[11]. Inone study, 61% of patients were found to require just one embolization, while 25%required two and 14% required three, making embolization an attractive treatmentoption for ABCs[23]. Sclerotherapy using polidocanol has also been shown to have highefficacy in the treatment of ABCs[2].

The management of this case was further complicated by the neoplasm beinglocated on the superior pubic ramus. Surgery relating to the superior pubic ramusrequires critical planning due to its proximity to corona mortis, a variant anastomosisbetween the external iliac artery or inferior epigastric artery and the obturator artery.This anastomosis runs along the posterior aspect of the superior pubic ramus.Significant, brisk haemorrhage may occur if it is accidentally breached andsubsequent haemostasis is difficult to obtain, although this occurrence is rare[24].Medical treatment adjuncts specific to ABCs were discussed at multi-disciplinaryteam meeting but were not deemed appropriate (e.g., denosumab) to optimise themanagement of this patient’s ABC.

Following review of the above literature and discussion at multi-disciplinarymeeting, this patient successfully underwent wide excision, curettage and bone graftas well as open reduction and internal fixation of the right hemi-pelvis.

CONCLUSIONWe have presented a less common case of ABC of the right superior pubic ramus in a

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Figure 3

Figure 3 Axial computed tomography pelvis.

young female and our management of this diagnosis. This case was initiallydiagnosed as a giant cell tumour, however, following specialist histopathologicalopinion of the intra-operative specimen, ABC was diagnosed. We hereby report thesuccessful treatment of this patient with wide excision, curettage and bone graft andunderwent open reduction and internal fixation of the right hemi-pelvis. This patienthas had an uncomplicated post-operative course, has returned to comfortable weightbearing and will be reviewed for minimum 5 yr in the out-patient setting to monitorfor reoccurrence.

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Figure 4

Figure 4 Coronal short tau inversion recovery magnetic resonance imaging.

Figure 5

Figure 5 Axial short tau inversion recovery magnetic resonance imaging.

Figure 6

Figure 6 Intra-operative view of lesion.

Figure 7

Figure 7 Intra-operative screening demonstrating curettage.

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Figure 8

Figure 8 Intra-operative screening with bone graft substitute.

Figure 9

Figure 9 Intra-operative screening with open reduction internal fixation.

Figure 10

Figure 10 Post-operative X-ray anteroposterior pelvis with open reduction internal fixation and bone graft substitute.

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