TKA Coronal Plane Balancing - Recon

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

Action	Numeric Key	Letter Key	Function Key
Show Bullets		S	Enter (frontside only)
20%	1	N
40%	2	H
60%	3	F	Enter (backside only)
80%	4	E
100%	5	M
Toss	0	T