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Minimally invasive spine surgeries (MISS)

Minimally invasive spine surgeries (MISS)

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Minimally invasive spine surgeries (MISS) since its inception around 15 years ago has undergone rigorous changes with ever evolving technologies. Minimally invasive spine surgeries with “percutaneous” and “tubular” approaches is based on novel concept of minimizing collateral soft tissue damage, while achieving surgical goal in various spinal pathologies. MISS has been applied to simple spinal procedures of discectomy, decompression and fusion to even complex surgeries like deformity correction. MISS vis a vis “conventional open techniques” has benefits in terms of postoperative pain, concurrent tissue damage, disruption of spinal stabilizing structures, estimated blood loss, need of blood transfusion, length of hospital stay, surgical site infections, time to ambulation and functional recovery.

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Page 1: Minimally invasive spine surgeries (MISS)

Minimally invasive spine surgeries (MISS)

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Minimally invasive spine surgeries (MISS)

Ashish Jaiswal*

ABSTRACT

Minimally invasive spine surgeries (MISS) since its inception around 15 years ago has undergone rigorous changeswith ever evolving technologies. Minimally invasive spine surgeries with “percutaneous” and “tubular” approaches isbased on novel concept of minimizing collateral soft tissue damage, while achieving surgical goal in various spinalpathologies. MISS has been applied to simple spinal procedures of discectomy, decompression and fusion to evencomplex surgeries like deformity correction. MISS vis a vis “conventional open techniques” has benefits in terms ofpostoperative pain, concurrent tissue damage, disruption of spinal stabilizing structures, estimated blood loss, needof blood transfusion, length of hospital stay, surgical site infections, time to ambulation and functional recovery.However MISS is associated with steeper learning curve, poorer surgical orientation, higher peroperative ionizingradiation to patient and surgical team, higher incidence of incidental durotomies, dependency on technology, andhigher upfront cost of treatment.

Copyright © 2012, Indraprastha Medical Corporation Ltd. All rights reserved.

Keywords: Minimally invasive, Spine surgeries, Tubular, Percutaneous

INTRODUCTION

Minimally invasive spine surgeries (MISS) are based onconcept of decreased concurrent tissue damage while per-forming index procedures in spine for treating variousspinal pathologies. The purported advantages of minimallyinvasive spine surgery are less blood loss, lesser surgicalmorbidity, need of blood transfusion, lesser postoperativeanalgesic requirement, less hospital stay and early rehabili-tation with functional resumption.1e6 Minimally invasivespine surgery has come a long way since its inception.There has been constant endeavor to minimize the collateralsurgical damage while achieving the surgical goal. Therehave been many revolutions in this field including introduc-tion of microscopes, endoscopes, specialized tubular andexpandable retractors. Availability of better instrumentationhas facilitated the minimization of surgical approach. MISSis commonly applied in various common spinal procedureslike discectomies, decompression and fusion. With time the

applications of MISS is expanding to include even complexsurgeries like spinal deformity correction.

MUSCLE PRESERVATION e THE KEYCONCEPT IN MISS

It is known that traditional open approaches to spinesurgery lead to increased paraspinal muscle injuryfollowing denervation, ischemia secondary to prolongedretraction and detachment of musculotendinous junction.Denervation and ischemia can result from direct injury todorsal roots and vasculature in extensive surgical exposure,and also occurs due to increased intramuscular edema andresultant focal compartment syndrome secondary to pro-longed strong retraction. This has a clinical implication inthe form of increased postoperative backache. The majoradvantage of MISS is preservation of paraspinal muscula-ture especially multifidous insertion in spinous process.7

Senior Consultant, Department of Orthopaedics and Spine Surgery, Apollo Hospitals, Seepat Road, Bilaspur, Chhattisgarh 645009, India.*Corresponding author. Tel.: þ91 9630005676, email: [email protected]

Received: 3.9.2012; Accepted: 24.9.2012; Available online 4.10.2012Copyright � 2012, Indraprastha Medical Corporation Ltd. All rights reserved.http://dx.doi.org/10.1016/j.apme.2012.09.003

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Disruption of the midline supraspinous and interspinousligament complex in conventional open approaches canlead to loss of tension band and thus can result in late post-operative instability. MISS avoids the loss of integrity ofthis midline supraspinous/interspinous complex which inaddition to providing structural stability to spine, also actsas a tie beam for effective functioning of paraspinalmuscles.2 Moreover, less muscle disruption in MISS alsoleads to decreased blood loss and lesser surgical stressresponse.

MINIMALLY INVASIVE LUMBARDISCECTOMIES

Lumbar discectomy has undergone a radical change inapproach since its first description by Mixter and Barr usinglaminectomy in 1934. Progressively, it was noted that thegoal of discectomy and decompression is achievable withlesser invasive approaches. Introduction of use of microscopefor discectomy by Yasargil and Caspar revolutionized thisprocedure and still microdiscectomy is considered asa “gold standard”. MISS was described by Foley and Smithin 1997 for discectomy using tubular retractors. This relieson dilating theway throughmusclefibers rather than strippingit from lamina and spinous process. Endoscope ormicroscopecan be used as an adjunct for visualization. Many spinesurgeons prefer using microscope owing to 3-Dimensionalvisualization and also, as most of them are already acquaintedwith use of microscope, while with endoscope, it has limita-tion of 2-Dimensional vision and one needs an additional skillto master due to unfamiliarity. However superiority of MISSover microdiscectomy is debated by some as, in microdiscec-tomy, already there is a minimal surgical exposure and longterm results of both the approaches have been found to besimilar.6Adequate decompression, regardless of the operativeapproach used, may be the primary determinant of radicularpain relief. Adversely, it has been noted that there is a higherof incidental durotomy in minimally invasive discectomy8

with possible explanation being limited visualization, poordepth perception and steep learning curve. Some argue thatmicrodiscectomy can itself be considered as aminimally inva-sive procedure for discectomy and controversy persistswhether to stick to age old microdiscectomy or to adopttubular discectomy where again, even an experienced spinesurgeon needs to tide over a steep learning curve. However,MISS seems to be more beneficial for spinal procedureswith extensive surgical exposure and soft tissue disruptionlike spinal instrumentation and fusion.4,5,9,10 It can be arguedthat discectomy is the most common surgery in spine, henceone should master MISS for discectomy before graduatingtomore extensive procedures withMISS.Minimally invasive

discectomy has an advantage in morbidly obese patientswhere surgical exposure through tubular retractor is betterattained than with conventional retractors used in microdiscectomy.6

Percutaneous transforaminal endoscopic discectomyunder local anesthesia is another way of doing MISS fordiscectomy. Yeung and Hoogland are credited for thedevelopment of the Yeung Endoscopic Spine System(YESS) in 199711 and the Thomas Hoogland EndoscopicSpine System (THESSYS) in 1994, respectively.12 Thepurported advantages are avoidance of general anesthesia,smaller skin incision, conduction as a day care surgeryand intraoperative active feedback of patient about allevia-tion of radicular symptoms. However, it is not without limi-tations, being applicable for specific types of discherniations and necessitates even steeper learning curves.Superiority of percutaneous techniques over conventionalmicrodiscectomy still remains unclear as similar outcomeshas been demonstrated with both methods.

MINIMALLY INVASIVE TRANSFORAMINALLUMBAR INTERBODY FUSION

Lumbar fusion is commonly done for spinal instability ordeformity resulting from spondylolisthesis or scoliosis aswell as low back pain from degenerative disc disease refrac-tory to conservative treatment. Interbody fusion is the mostpreferred approach for lumbar fusion as it facilitates largersurface of fusion bed, opening up of neural foramen through“jack up effect” and additional anterior stability when a cageis placed. Currently, transforaminal lumbar interbody fusion(TLIF) is most commonly performed for lumbar arthrodesis,as TLIF provides exposure of the disc space while requiringless dural and nerve root retraction. However in traditionalopen approach TLIF requires extensive surgical exposure.The iatrogenic injury of muscle and soft tissue is an impor-tant cause of postoperative low back pain which might evencounteract the effects of surgery and sometimes labeled as“fusion disease.” MISS transforaminal lumbar interbodyfusion using nonexpendable or expandable tubular retractorand bilateral percutaneous screw placement reduces suchcollateral soft tissue damage and has shown to producefavorable outcomes in respect to postoperative back pain,total blood loss, need for transfusion, length of hospitalstay, time to ambulation and functional recovery.4,5 Iliaccrest autograft remains the gold standard, with the osteo-genic, osteoinductive, and osteoconductive componentsrequired to achieve fusion, but it comes with associateddonor site morbidity. Majority of spine surgeons use locallyharvested bone from bony decompression as a graft to avoiddonor site morbidity. However in MISS transforaminal

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interbody fusion when the amount of local graft is inade-quate or even otherwise allograft or bioactive agent likerecombinant human bone morphogenetic protein (rhBMP-2) can be added to facilitate fusion.

MINIMALLY INVASIVE DECOMPRESSIONS INLUMBAR CANAL STENOSIS

Lumbar canal stenosis (LCS) is a common degenerativeprocess among the elderly leads to progressive neurogenicclaudication and often needs surgical decompression toalleviate the associated symptoms and disability. Indeed,LCS is the most common indication for surgery of the spinein patients over the age of 65 years. Conventionally lumbarlaminectomy was indicated surgical procedure for LCS.However with advances in noninvasive imaging especiallyMRI, it was noted that most of these pathologic compres-sive changes typically occur at the level of the interlaminarwindow, hence it seems more prudent to do focal decom-pression at level of compression rather than wide laminec-tomy. The ultimate goal, regardless of the technique used, isto perform an effective decompression of the affected thecalsac and nerve root. Current MISS techniques for decom-pression avoids collateral damage and have successfullyshown to shorten hospital recovery times, reduce intraoper-ative complications, and minimize soft tissue trauma withresultant decrease in surgical stress response which isa crucial factor in consideration in elderly patients.1e3

There has been constant endeavor to adopt a minimallydestructive method to attain aimed surgical neural decom-pression in lumbar canal stenosis. Various methods ofless invasive approaches namely spinous process splittingapproach, bilateral laminotomies, bilateral decompressionvia unilateral laminotomy etc has been described. MISSfor lumbar canal stenosis using tubular retractors aided byendoscope or microscope has been employed successfullyto treat LCS.1e3 However, limitation of MISS in LCSdecompression is that it may fail to provide an adequatedecompression in patients with bony foraminal stenosis.In patients with lumbar stenosis in the setting of spondylo-listhesis, scoliosis, or severe degenerative disc disease, theinherent destabilizing nature of posterior decompression,even using MISS, may warrant a fusion operation in addi-tion to decompression.3

MINIMALLY INVASIVE FIXATIONS IN THOR-ACOLUMBAR TRAUMA

Conventional spine exposures add to pre-existing paraspi-nal soft tissue injury secondary to trauma in spinal injuries.

MISS has a potential to reduce the approach-relatedmorbidity associated with conventional techniques whichis even more crucial in setting of pre-existing injury.However MISS has limited indications in thoracolumbarinjuries. Pure osseous injuries like bony chance fracturesare ideally suited for MISS fixations where one can doaway without bone grafting and decompression.9 Fixationin such a pure osseous injury has further advantage ofpossibility of implant removal with restoration of spinalmobility.9 Spinal fractures needing decompression may befixed with percutaneous instrumentation and decompressioncan be achieved with expandable tubular retractors or ante-rior laproscope/thoracoscopic decompressions.10 Howeverone has to conversant with all the procedures and carefullyselect fractures types amenable for such MISS interven-tions. Specific clinical indications for MISS interventionsin spinal fractures are still evolving.

Percutaneous vertebroplasty and kyphoplasty are mini-mally invasive procedures when performed in symptomaticosteoporotic vertebral fractures provides dramatic painrelief to patients who are not responding to conservativecare.13 Vertebroplasty entails the percutaneous injectionof bone cement into the fractured vertebra, while kypho-plasty addresses pain and kyphotic deformity by the percu-taneous expansion of an inflatable bone tamp to effectfracture reduction before cement deposition in a fracturedvertebra.

SUMMARY

Although the authoritative definition of minimally invasivespine surgery remains elusive, the one proposed insummary statement published by McAfee et al14 looksmost apt. “An MISS is one that by virtue of the extentand means of surgical technique results in less collateraltissue damage, resulting in measurable decrease inmorbidity and more rapid functional recovery than tradi-tional exposures, without differentiation in the intendedsurgical goal.” Growing experience with MISS techniquesby operating surgeons and development of newer instru-mentation by manufactures are now enabling an increas-ingly large portion of spine surgical procedures to beperformed via minimally invasive techniques.

Extensive tissue trauma in traditional surgical exposurescause exaggerated surgical stress response and leads tovariety of complications like deep venous thrombosis,pulmonary embolism, pulmonary atelectasis, pneumonia,urinary tract infections, ileus, narcotic dependency etc.Indeed, the greater the trauma, the greater the response.MISS plays an important role in reduction of this surgicalstress response and associated complications.7

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Short term benefit like lower intraoperative blood loss,fewer infections, less intensive care utilization, less postoper-ative analgesia, and shorter hospitalization with MISS visa vis traditional open surgeries are more as compared to longterm benefits. MISS techniques may reduce postoperativewound infections as much as 10-fold compared with otherlarge series of open spinal surgery published in the literature.15

The steep learning curve of MISS has been one of thegreatest barriers to the widespread adoption of minimallyinvasive spine surgery. The surgeon practicing this needsa specialized training and experience. He should be expertin doing open surgeries too, as at times he may need toconvert to open procedure, if it is not feasible to carry onwith MISS. MISS has a disadvantage of being an instru-mentation dependent procedure. MISS techniques requirean extensive knowledge of the focal structural/radiologicalanatomy and safe surgical corridors of spinal region ofinterest.16 Additionally, one should be aware of possibleanatomical variations and analyze them carefully in preop-erative imaging to avoid operative complications. MISSrequires significant practice and didactic training to acquirethe skills necessary to perform it safely.

MISS entails higher cost of treatment especially ininstrumented cases where the cost of dedicated implantsand instruments is more than once used in traditionalsurgeries. However this increase in cost can be offset byadvantages of MISS like lesser hospital stay, lesser compli-cations, lesser blood loss and earlier return to functionalstatus which allows lesser postoperative expenditure andearlier resumption of productivity of patient.17

High radiation exposure to patient and operative team inMISS is a cause of concern being 10e20 times greatercompared to traditional open methods.18 Instrumentationin MISS is blindfolded and entails frequent use of fluoros-copy at multiple stages. The steep learning course in MISSfurther makes the operating surgeon to use fluoroscopefrequently to assure proper placement of implants.16 Intraditional open procedures, many experienced spinesurgeons place pedicle screws with freehand techniquebased on anatomical landmarks and hardly use intraopera-tive imaging to guide the open placement of pedicle screws,so a requirement for numerous intraoperative radiographs inMISS can be a considerable deterrent to the adoption ofminimally invasive techniques. Although, it has beenshown that with growing experience the amount of radia-tion tends to decrease but it still remains higher than tradi-tional open approaches. Introduction of computernavigation and continuous electromyography (EMG) moni-toring as an adjunct in MISS19 has potential to reduce theamount of radiation, but again the navigation systems arenot widely available owing to high establishment cost andneed of additional dedicated technical expertise.

MISS is an exciting development in field of spine surgeryand to some extent has stood its promise and scientificallyratified. However there is a need of high quality multicentrerandomized control studies with large study population toclearly elucidate the advantages and disadvantages ofMISS before it is accepted as a “Gold standard” in spinalsurgeries. Moreover clinicians and researchers need toconstantly endeavor to find out ways to simplify the proce-dure, reduce the financial implications, reduce the steeplearning curve, improve clinical accuracy, reduce peropera-tive radiation and broaden the clinical applications of MISS.

CONFLICTS OF INTEREST

The author has none to declare.

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