2005 OITE Question 223

Question

During revision TKA, the soft tissue are correctly balanced in extension. Failure to restore the distal femoral joint line will most likely lead to:

1 – recurvatum

2 – decreased flexion

3 – flexion contractures

4 – flexion instability

5 – patellar instability

Figures

Answer (click for answer)

Answer: 2

This is a concept that you just have to know…balancing! In terms of this question, the key principle is realizing that elevating the joint line (as is often done in revision surgery) will cause an enormous amount of tension on the collateral ligaments and the knee will be tight with attempted flexion.

There are some general rules that may be considered when balancing the flexion and extension gaps: (1) changes in the thickness of the tibial insert or augmentation will affect both the flexion gap and the extension gap equally; (2) problems with the extension gap can be corrected distally on the femur with augmentation of the femoral component (for a loose extension gap) or with further resection of the distal part of the femur (for a tight extension gap), assuming that a proper posterior capsular release has already been performed; and (3) solitary flexion-gap problems are handled on the femoral side with anterior or posterior shifting of the femoral component or with appropriate sizing changes of the anteroposterior dimension of the femoral component (that is, by using a larger component for a loose flexion gap or a smaller component for a tight flexion gap). Posterior metal augmentation can be used as needed.

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