Introduction Definition both medial and lateral ligaments may be stretched or contracted with time it is essential to balance these ligament in both the coronal and sagital plane to obtain an optimum outcome Pathophysiology concave side tight ligaments that need release convex side stretched ligaments that need tightening must test balancing in both flexion and extension Kinematic alignment principle of placing implants in more varus or valgus based on patient anatomy constitutionally varus = varus tibial implant constitutionally valgus = valgus tibial implant outcomes are roughly equivalent with neutrally aligned knees Varus Deformity Anatomy medial side is tight (concave), lateral side stretched (convex) Goals create precise bone cuts release the tight medial ligaments tighten the lax lateral ligaments balance flexion and extension gaps by adjustment of polyethylene bearing thicknesss Steps of medial release Step 1 Deep MCL Release To Mid-Coronal Plane Of Tibia Step 2 Medial Osteophyte Removal Step 3 Release Posteromedial Corner (Posterior Oblique Ligament) Step 4 Medial Tibial Reduction Ostectomy Step 5: Consider PCL Release/Substitution If Imbalance Persists At This Point (If Substitution Not Initially Chosen) Step 6 Release Semimembranosis (Especially If There Is An Associated Flexion Contracture) Step 7 Pie Crust Superficial MCL (Favor Use Of 18 Gauge Needle) Step 8 Complete Superficial MCL Release / Pes Anserinus Rarely Required Even In Severe Cases Destabilizes Medial Flexion Gap / Consider A Constrained Prosthesis Differential release: performed with two components of superficial MCL posterior oblique portion is tight in extension (release if tight in extension) anterior portion is tight in flexion (release if tight in flexion) Lateral tightening use a prosthesis that is sized to "fill up" the gap and make the stretched lateral ligaments taut if a polyethylene bearing thickness of >15mm is required to gain appropriate lateral ligamentous tension, consider use of a constrained prosthesis to avoid excessive joint line elevation Valgus Deformity (lateral side is concave/tight) Anatomy lateral side is tight (concave), medial side stretched (convex) Goals create precise bone cuts release the tight lateral ligaments tighten the lax medial ligaments balance flexion and extension gaps by adjustment of polyethylene bearing thicknesss Lateral release in order Step 1 osteophytes Step 2 posterolateral capsule Step 3 iliotibial band if tight in extension with pie crust or release off Gerdy's tubercle Step 4 popliteus if tight in flexion (release if tight in flexion) release the anterior part of its insertion for severe deformities release both the iliotibial band and the popliteus Step 5 LCL some authors prefer to release this structure first if tight in both flexion and extension other authors prefer to release the LCL last if LCL & Popliteus require release, flexion gap stability is lost so consider constrained prosthesis differential release: performed by differentially release the IT band and popliteus Medial tightening fill up medial side until medial ligament complex is taut In severe cases, if a polyethylene bearing thickness >15mm is required to obtain appropriate medial tension, consider a constained prosthesis to avoid excessive joint line elevation Avoid internal rotation of the femoral component internal rotation is common due to hypoplasia of the lateral femoral condyle internal rotation of the femoral component may lead to patellofemoral maltracking and a coronally asymmetric flexion gap if posterior referencing is used, verify femoral component rotation against the epicondylar and anteroposterior axes Flexion / Contracture Deformity Anatomy concave side is posterior- needs to be released Posterior release order 1) posterior femoral & posterior tibial osteophytes 2) posterior capsule 3) additional resection of distal femur 4) gastronemius muscles (medial and lateral) All releases are performed with knee at 90 degrees of flexion allows the popliteal artery to fall posteriorly to decrease risk of injury You do not want to address a contracture by removing more tibia will change the joint line and lead to patella alta Complications Peroneal nerve palsy correction of valgus and flexion contracture deformity has highest risk of peroneal nerve palsy if patient presents with a peroneal palsy in recovery room then then take off dressing and flex the knee watch for three months to see if function returns if function does not return, consider nerve conduction studies or operative exploration to access for damage Coronal plane deformities >20 degrees cannot be corrected by intra-articular bone cuts and soft-tissue balancing alone and require an extra-articular osteotomy