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Updated: Jan 1 2023

TKA Coronal Plane Balancing

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https://upload.orthobullets.com/topic/5015/images/coronal balancing.jpg
  • 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
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