Summary TKA Instability is a common cause of early failure following total knee arthroplasty. Diagnosis can be made clinically with presence of a varus/valgus thrust during ambulation, positive posterior sag with the knee flexed to 90 degrees and overall laxity of the knee on exam. Treatment depends on severity of symptoms, direction of instability and the type of TKA prosthesis present in the knee. Epidemiology incidence common cause of early failure following total knee arthroplasty accounts for 10-20% of revisions Etiology Types extension (varus-valgus) instability flexion (anteroposterior) instability mid-flexion instability genu recurvatum global, multiply-operated instability Presentation History previous operations indication for initial replacement original implant information comorbidities including connective tissue disease inflammatory diseases diabetes, Charcot arthropathy history of trauma Symptoms pain, instability or both timeline as to start of symptoms, what worsens/improves Physical Examination overall gait, observe for valgus/varus thrust ligamentous examination throughout range of motion, attempt to reproduce symptoms flexion instability test positive posterior sag with the knee flexed to 90 degrees overall strength extensor mechanism competency patellar tracking Imaging Radiographs recommended views weightbearing AP used to assess joint line symmetry full-length AP used to assess overall mechanical alignment lateral used to assess tibial slope, tibial subluxation, recurvatum findings extension instability excessive distal femoral resection oversized femoral component flexion instability overresection of posterior femoral condyles undersized femoral component increased tibial slope mid-flexion instability anterior or proximal placement of femoral component genu recurvatum Computed tomography can offer information regarding component rotation Studies Serum labs CBC, ESR, CRP, must rule out infection as potential cause Knee aspiration to rule out infection via cell count and culture Extension (varus-valgus) Instability Definition varus/valgus instability types symmetrical caused by excessive distal femoral resection, causing flexion/extension gap mismatch asymmetrical more common ligamentous asymmetry caused by failure to correct deformity in the coronal plane Treatment symmetrical instability distal femoral augments to tighten extension gap upsizing poly will fail as it affects both flexion and extension gaps asymmetrical instability balance ligaments accordingly controlled release of soft tissue on contracted side if ligamentously insufficient, varus/valgus constrained device needed if caused by, intraoperative MCL transection/deficiency suture repair or suture anchor reattachment, use of either CR or PS implant, hinged knee brace for 6 weeks postoperatively use of unlinked constrained prosthesis Flexion (anteroposterior) instability Definition occurs when the flexion gap exceeds the extension gap knee dislocation posterior stabilized knees can "jump the post" resulting in dislocation Treatment over resection of posterior femoral condyles treat with posterior augments undersizing femoral component upsize femoral component excessive tibial slope decrease slope and consider posterior-stabilized prosthesis excessive posterior femoral condyle cuts augment posterior condyles of distal femur posterior cruciate ligament insufficiency following a cruciate-retaining arthroplasty convert to posterior-stabilized prosthesis Mid-flexion instability Causes controversial topic, poorly understood associated with modification of the joint line involves malrotation when the knee is flexed between 45 and 90 degrees potential contributing factors femoral component design in sagittal plane attenuation of anterior MCL overall geometry of the tibiofemoral joint Treatment typically, full revision is required goals restoration of joint line equalize flexion and extension gaps Genu recurvatum Definition fixed valgus deformity and iliotibial band contracture Causes associated with poliomyelitis, rheumatoid arthritis, or Charcot arthropathy poliomyelitis patient walks with knee locked in hyperextension, ankle in equinus due to quadriceps weakness Treatment typically long-stemmed posterior stabilized, or varus/valgus constrained implant rotating-hinge reserved for salvage as residual hyperextension may occur, leading to early failure Global, multiply-operated instability Definition laxity of both flexion and extension gaps, as well as varus/valgus instability can be associated with severe bone loss Presentation multidirectional ligamentous instability with recurvatum gait Treatment varus/valgus constrained prosthesis at minimum typically, hinged prosthesis with or without augments, sleeves, cones severe bone loss situations may require endoprosthetic replacements
Technique Guide Technique guides are not considered high yield topics for orthopaedic standardized exams including ABOS, EBOT and RC. TKA Revision Orthobullets Team Recon - High Tibial Osteotomy Technique Guide Technique guides are not considered high yield topics for orthopaedic standardized exams including ABOS, EBOT and RC. TKA - Parapatellar Approach Derek T. Bernstein Stephen Incavo Recon - High Tibial Osteotomy Technique Guide Technique guides are not considered high yield topics for orthopaedic standardized exams including ABOS, EBOT and RC. TKA - Varus Knee with Anterior Referencing and Gap Balancing Technique Derek T. Bernstein Stephen Incavo Recon - TKA Axial Alignment
QUESTIONS 1 of 8 1 2 3 4 5 6 7 8 Previous Next Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ09.230) A 66-year-old female presents with knee instability going down stairs 18 months after a posterior cruciate retaining total knee arthroplasty. She reports having recurrent effusions. Radiographs are shown in Figure A. What is the most likely cause for her instability? QID: 3043 FIGURES: A Type & Select Correct Answer 1 Intraoperative rupture of the patellar tendon 2% (66/3368) 2 Alteration of the joint line 2% (81/3368) 3 Posterior cruciate insuffiency 93% (3149/3368) 4 Anterior cruciate insufficiency 1% (24/3368) 5 Catastrophic component loosening 1% (25/3368) L 1 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (SBQ07HK.2.1) A 66-year-old male is undergoing a total knee arthroplasty using a fixed bearing posterior stabilized component. During the intraoperative trialing of the components, it is noted that the flexion gap is loose, and the extension gap is appropriate. Compared to a patient with appropriate flexion and extension gaps, this patient would be at an increased risk for which of the following? QID: 214242 Type & Select Correct Answer 1 Manipulation under anesthesia 1% (22/1705) 2 Knee hyperextension 2% (30/1705) 3 Posterior knee dislocation 60% (1015/1705) 4 Anterior knee dislocation 35% (597/1705) 5 Patella fracture 2% (33/1705) L 2 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic This is an AAOS Self Assessment Exam (SAE) question. Orthobullets was not involved in the editorial process and does not have the ability to alter the question. If you prefer to hide SAE questions, simply turn them off in your Learning Goals. (SAE07HK.7) Figure 3 shows the AP radiograph of a patient with diabetes mellitus who has knee pain. A semiconstrained knee prosthesis was used in this patient to prevent which of the following complications? QID: 5967 FIGURES: A Type & Select Correct Answer 1 Infection 1% (5/951) 2 Instability 96% (913/951) 3 Stiffness 1% (7/951) 4 Bone loss 1% (6/951) 5 Malalignment 1% (14/951) L 1 Question Complexity E Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK
All Videos (20) Podcasts (1) Login to View Community Videos Login to View Community Videos Orthopaedic Summit Evolving Techniques 2021 61-Year-Old Construction Worker, BMI 30, Trips On A Lead Pipe 5 Years After Total Knee Replacement Now With An Unstable Knee & Diagnosed With An MCL Rupture: How I Approach This - Henry D. Clarke, MD Recon - TKA Instability 1 week ago 17 views 5.0 (1) Login to View Community Videos Login to View Community Videos ICJR 9th Annual Revision Hip & Knee Course Patellar Instability in Total Knee Arthroplasty: Evaluation & Management - Nicholas A. Bedard, MD Nic Bedard Recon - TKA Instability 8/24/2022 21 views 0.0 (0) Login to View Community Videos Login to View Community Videos ICJR 9th Annual Revision Hip & Knee Course Evaluation and Surgical Management of Flexion Instability - Jeremy Gililland, MD Jeremy Gililland Recon - TKA Instability 8/24/2022 36 views 5.0 (1) Recon⎪TKA Instability Orthobullets Team Recon - TKA Instability Listen Now 16:21 min 6/4/2020 282 plays 5.0 (1) See More See Less
2022 Global Medial Pivot Symposium Painful Right Knee and Symptomatic Left TKA in 72F (C102078) Alexander Sah Recon - TKA Instability A 8/26/2022 6406 35 30 Windswept Knees in 69F (C101409) Shaun Patel Recon - TKA Instability B 3/26/2020 125 2 6 Severe Valgus Knee in 58F (C101405) Shaun Patel Recon - TKA Instability B 3/22/2020 150 11 2