Balancing

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