Dr.Sandeep AgrawalConsultant Orthopedic SurgeonMS,DNBAgrasen HospitalGondiaMaharashtraIndiawww.agrasenortho.comdrsandeep123@gmail.com09960122234

Knee Osteoarthritis:Basics to Reconstruction

to Replacement

Clinical evaluationPain, functional decline : walking, climbing stairs, arising from low chair.DeformityDetailed historyMajor source of failure : inability to live up to unreasonable patient expectation, documentation.General health assessment questionnaires

Radiographic evaluationAP, 45 weight-bearing, lateral, Merchant viewsThree joints standing film (split scanogram): define the mechanical and anatomical axis.Common mistake : supine image of knee, MRI (not specific for articular cartilage abnormality).MRI for cartilage : T1-weight, fat suppressed three-dimensional, spoiled gradient echo technique, T2-weighted fast spin-echo technique

Knee : supine AP view

Knee : lateral view

Knee : tunnel view

Nonsurgical careCane : resting and unloading the joint.Brace : Medication Rehab : muscle power

training

Joint-Preserving surgical Procedures

ArthroscopyOsteotomy : for younger and more active patient, disease affects predominantly one compartment

– Valgus-producing tibial osteotomy– Varus producing femoral osteotomy

Arthroscopy

Role of arthroscopic surgery in the treatment of OA knee : controversySuccess in the treatment of OA knee : proportional to the degree of mechanical symptoms (loose bodies, meniscal tears, unstable cartilage flaps), inversely proportional to the severity of the underlying arthritis (malalignment)

Valgus-Producing Tibia OsteotomyIdeal patient : age younger than 50 and active, with high functional demands, involvement mainly on medial side.Contraindications : inflammatory arthritis, poor flexion(<90o), flexion contracture, ligament instability, tricompartmental arthritisLess successful in smokers, patients age more than 60 y/o, degree of deformity beyond 10o

Valgus-Producing Tibia OsteotomyMedial lengthening but not lateral shortening (open wedge).Advantage : more anatomic restoration with resultant ligament stability, ability to more fine tuning the correction.Disadvantage : risk of nonunion and loss of correction.

Varus-Producing Femoral Osteotomy

For younger, active patients with involvement isolated in lateral compartment.Deformity should be less than 15o, without flexion contracture or inflammatory disease.Correction to physiologic valgus (4o to 6o)

Total Knee ArthroplastyAdvanced disease resulting in failure of the joint to functional satisfactorilyKey elements

– Debilitating symptoms– Failure of such symptoms to respond to

less invasive treatment– Medical suitability of the patient to

respond to surgery

Factors Affecting OutcomeTKA : survivorship exceeding 90% at 10 years, 80% at 15 years, 75% at 20 years.Age, gender, primary diagnosis, prosthetic design.Positive factors : age of 70 or older, RA, cemented fixation.Adverse factors : younger than 55 y/o, male, OA.

Factors Affecting OutcomeObesity :

– Difficulties of exposure– Well-aligned, well-fixed implants fare as

well in the heavy patients as in the general population

– Wound complications are more common

Factors Affecting OutcomeJuvenile Rheumatoid Arthritis

– Severe joint destruction and need for reconstructive surgery at a very young age.

– High rate of infection– Post-operative stiffness

Factors Affecting OutcomeHemophilic Arthropathy

– Repeat hemarthrosis secondary to coagulopathy

– Most commonly affects the knee– Young and immunodeficiency, high rate

of infection– At least 10% failing within 5 years

Factors Affecting OutcomeOsteonecrosis

– Secondary to steroid or alcohol usage in younger patients, spontaneous occurrence in older patients

– Preoperative MRI can assist in determining the amount of periarticular bone involvement

Factors Affecting OutcomePatellofemoral Arthritis

– Isolated PF OA that is calcitrant to treatment can be successfully managed with TKA in older patients

– Functional results of TKA are superior to patellectomy or patellofemoral arhtroplasty and are equal to TKA for 3 compartmental arthritis

Impact of Prior Surgery on Subsequent TKA

Higher complication and higher revision rates and less satisfactory outcomes than primary TKAPrevious scar should be incorporated whenever possible or standard incision with optimal skin bridgeIf hardware is extensive : consider staged procedure.

Impact of Prior Surgery on Subsequent TKA

Patella baja is common following tibial osteotomy, lead to increased tension on the tendon insertion during exposureTKA after femoral osteotomy : relative post-opertive varus of the femoral component, can be reduced with the use of EM alignment guideConversion of fused knee to TKA : hinged or constrained prosthesis are recommended

Surgical TechniqueOptimal success of TKA

– Accurate restoration of the mechanical axis : intra and extra medullary guide.

– Good fit and fixation of the implant to host bone

– Careful attention to soft-tissue balance : equal tibiofemoral space in both flexion and extension, proper femoral rotation.

Too tight : flexion contractureExcessive release : instability.

Design issues Fixation Posterior Cruciate LigamentModularity Mobile bearing

Design issues Fixation

– Methacrylate cement fixationEarly loosening is more common with cementless fixationCementing only the metaphyseal surface of the tibial component and press fitting the stem or keel has higher early loosening rate than full cementing the tibial component

– Biologic fixation

Design issues Posterior Curciate Ligament– Retention :

Advantage :more physiologic femoral roll back, accurate joint line restoration, bone preservation, proprioceptive role of the ligament.PCL too tight : posterior femoral subluxation, asymmetric posterior polyethylene wear, osteolysis, release too much may lead to late failure

– Sacrifice – Substitution : cam and post mechanism,

increasing the anterior lip of a conforming tibial polyethylene, risk of dislocation, polyethylene wear debris from cam and post.

Design IssuesModularity

– Standard design feature of metal-backed tibial component.

– Advantage : greater intraoperative flexibility and the potential for simple revision of a worn PE

– Disadvantage : motion between the tibial plate and PE back-side wear

Design Issues Mobile Bearing Design

– Allow mobile bearing to rotate, increased articular conformity, advantage has yet to be demonstrated, durable well into 2nd decade.

– Wear and osteolysis– Unique problems : baring fracture and

dislocation.

Patellar ResurfacingControversialPatellar complications remain one of the most common sources of problems after TKARevision rates are either equivalent or higher following knees without patellar resurfacingConsensus : knees without patellar resurfacing are at a somewhat increased risk for anterior knee pain, but are at a decreased risk for serious patellar complications

Unicompartmental ArthroplastyAlternative to TKA or osteotomy for one compartment disease.Survivorship of greater than 90% at 10 years has been documented.Patient selection and surgical technique are the key elements.Contraindications : – Inflammatory arthritis– Severe fixed deformity– Previous opposite compartment menisectomy– Tricompartmental arthritis

Unicompartmental ArthroplastyRecommended correction: 1o to 5o of postoperative valgus.Advantage : quicker recovery, fewer short-term complications, better functional outcome.Causes of failure : implant wear, loosening or subsidence, progression of symptomatic arthritis in the lateral or patellar compartments.Revision of uni-knee is less complex than revision TKR.

Incision size should not be the dominant outcome measure of this technique.

Unicompartment Arthroplsty

Complications InfectionThromboembolic diseaseMedial collateral ligament injuryExtensor mechanism failureArthrofibrosisPeriprosthetic fracture

Infection Attention to careful surgical technique and soft tissue handling.Laminar air flow and prophylactic antibiotics : reduce infection.Risk factors : immunosuppression, diabetes, smoking, prior surgery, obesity.Antibiotic-cementing : lower incidence of infection, may considered for high risk patients.

Infection :staged surgery

Thromboembolic diseaseAbsence of effective prevention : historical data, 50%Controversy remains regarding the optimal prophylaxis regimen.Physical modality : useful adjunct– compression stocking, pneumatic compression

devices, continuous passive motion machines, early mobilization.

Two agents commonly used – Low molecular weight heparin

Lower rate of DVT but higher bleeding rate– Coumadin

Medial collateral ligament injuryConversion to a prosthesis that provides varus/valgus restraintRepair of reattachment : equally viable alternative, wear braces for 6 weeks but are allowed full ROMKnee scores and ROM at F/U are equivalent to knees without this complication

Extensor mechanism failureRupture of patellar tendon : compromise in functional outcomes.– Achilles tendon allograft, technique demanding,

needs good fixation methods.

Fracture of the patella : compromised circulation, overaggressive resection, maltracking, overt trauma.– Incidence less than 1%– Surgical treatment : marked extensor

mechanism disruption, gross patellar loosening.

Arthrofibrosis Stiff total knee : common source of failure and remains unsolved.Best predictor of post-op ROM : pre-op ROM.Early suspect : manipulation under epidural anesthesia and aggressive physical therapy.Late treatment : unreliable and high rate of failure.

Periprosthetic fracturePrevalence : less than 2%Risk factors : – Osteoporosis, Stress shielding, Femoral notching,

Osteonecrosis, Wear-related osteolysis

Treatment : maintaining alignment and fracture stability with early ROMKey factors of surgical decision making : fracture displacement, stability of the prosthesis, quality of bone.

Periprosthetic fractureImplant loosening : revision, allograft for bone defect, implant is cemented to the allograft with long stems, preserve collateral ligament but usually needs articular constraint.Displaced fracture : – Intercondylar open : retrograde nail through

transarticular approach– Fixed angle device and locked screws : evolving– Flexible IM rod : less rigid

Revision Total Knee ArthroplastyEvaluation of painPreoperative planningSelective component retentionPatellar failure management of bone loss

Evaluation of painSuccessful revision of a painful, failed TKA is dependent on accurate evaluation of the cause of failure.Intrinsic (knee related) and extrinsic cause Pain from hip or spine ?Aspiration : negative culture does not exclude infection, white blood cell count higher than 2500 hint chronic low-grade infection, repeat aspiration can increase accuracy.

Preoperative planningChallenge of successful outcome :

– Lower level of general patient health– Decreased soft tissue integrity– Bone loss Complication rate : almost 25%Factors compromise outcome: infection, extensor mechanism dysfunction, instability, fixation failure, periprosthetic fracture

Preoperative planningIndications for revision TKR : gross loosening, fracture, instability, infection, malalignment, wear, osteolysis or extensor mechanism disruption.Midline incision is preferred, lateral most incision for multiple old incisionsCollateral ligament integrity, gap balancing, joint line restoration(1.5 cm proximal to the tip of fibula)

Preoperative planningFactors impacting the flexion gap :– Tibial resection level– Polyethylene thickness– Tibial slope– AP dimension of the femoral component– AP placement of the femoral componentFactors impacting the extension gap:– Tibial resection level– Polyethylene thickness– Distal femoral resection– Posterior capsule

Selective component retentionSignificant PE wear with osteolysis : may consider change PE only but the failure rate is 30%-40%.Consider any occult reasons that lead to excessive wear of PE

– Malalignment– Inadequate soft-tissue balance

Patellar failureOne of the most common indication for revision TKR.Revision TKR due to isolated patellar fracture : high rate of failure due to unrecognized malalignment, evolving patellar osteonecrosis, inability to restore bone stock.Patellar bone loss (inadequate bone stock): patellectomy or debridement, extensor lag and weakness due to loss of patellar height.

Management of bone lossInfection and osteolysis can result in significant bone loss, often under-estimated.Metal augment or substitute or bone grafting.Contained defect : morcellized bone with long stem prosthesis.Uncontained defect : structural allograftMetallic mesh : converting uncontained defect into contained, Circumferential defects : allograft prosthesis composite

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