Coronal Plane Balancing / Varus Valgus
Whiteside's Manual
| Medial Structures | Lateral Structures | |
| Tight in Extension |
Posterior MCL Semimembranosus Posterior capsule Pes Anserinus |
ITB Posterior capsule Lateral Head GN
|
| Tight in Flexion |
Anterior MCL PCL |
PCL Popliteus PL corner LCL |
Principle
Release on the concave side of the deformity and fill up on the convex side until the ligament is taut
Varus deformity / Medial Release
In a severe varus deformity, may be best to PS
1. Removal of osteophytes / meniscus and release deep MCL
- curved osteotome
2. Release posteromedial corner and attachment of semimembranosus
- denude tibia subperiosteally around to back
3. Release pes anserinus tendons
4. Subperiosteal elevation of superficial MCL at pes anserine region
- cannot release in full
- usually elevate all the tissues as a sleeve
- doesn't require reattachment
- over release: require a constrained knee device / repair and splint in young patient
Valgus deformity / Lateral Releases
May be best to always PS in valgus knee
Order debatable
1. Removal of osteophytes / meniscus and lateral capsule
2A. Tight in extension
- release ITB off Gerdy's tubercle
2B. Tight in flexion
- release popliteus from femur & allow to slide
3. Posterolateral capsule
4. Lateral head of gastrocnemius off posterior femur
5. LCL from femur & allowed to slide
2. Sagittal Plane / Balance Flexion Extension Gap
Goal
- obtain a gap in extension equal to the gap in flexion
- will make the tibial insert stable throughout the arc of motion
Principle
- more sophisticated and difficult
- the knee has two radii of curvature, one for the PFJ and the other for the weight bearing area of the knee
General rule
1. Gap problem is symmetric
- adjust the tibia
2. Gap problem is asymmetric
- adjust the femur
6 Scenarios
1. Tight in extension and flexion
Problem
- symmetric gap
- did not cut enough tibia
Solution
- cut more proximal tibia
2. Loose in extension and flexion
Problem
- symmetric gap
- cut too much tibia
Solution
1. Thicker poly insert
2. Metallic tibial augment
2. Tight in flexion
Common in CR / PCL tightness
- limited flexion
- anterior lift off of tibial tray
- tight in flexion
Problem
- insufficient posterior femoral cut
- PCL scarred and too tight
- no posterior slope in tibial cut
Solution
1. Clear posterior horns mensicus and posterior osteophytes
2. Recess / excise PCL
3. Recut anterior slope of tibia
- maximum 7o posterior slope
4. Down size femoral component and recut
- increases posterior femoral condyle resection
- avoid notching
4. Loose in flexion
Problem
- asymmetric gap
- cut too much posterior femur
Solution
1. Upsize femoral component & use posterior femoral augments (cement/metal)
- difficult as not available in primary TKR equipment
2. Increase poly, convert to tight in extension, recut distal femur
5. Tight in extension
Problem
- insufficient distal femoral cut
- tight posterior capsule
Solution
1. Release posterior capsule / osteophytes
2. Recut distal femur (1-2 mm at a time)
6. Loose in extension
Problem
- asymmetric gap
- cut too much distal femur or
- AP size too big
Solutions
1. Distal femoral augments
2. Increase poly size, convert to tight flexion & downsize femur, convert to symmetric gap problem