Abstract
Fixed flexion contracture is often present in association with osteoarthritis of the knee and correction is one of the key surgical goals in total knee replacement. Surgical strategies to correct flexion contracture include removal of posterior osteophytes, posterior capsular release and additional distal femoral bone resection.
Traditional teaching indicates 2 mm of additional distal femoral bone resection will correct 10 degrees of flexion deformity. However some studies have questioned this figure and removing excessive distal femoral bone results in elevation of the joint line, potentially causing patella baja, alteration in collateral ligament tension through the flexion arc and mid-flexion instability.
The aim of our study is to determine the relationship between distal bone resection of the femur and passive knee extension in total knee arthroplasty.
A cohort of 50 patients, undergoing total knee arthroplasty, was recruited. Following complete femoral and tibial bone preparation, to simulate the effect of distal femoral bone resection, augments of 2 mm increments (2 mm, 4 mm, 6 mm, 8 mm) were placed onto the trial femoral component. The degree of flexion contracture with each augment was measured using computer navigation.
The results showed a 2 mm augment produced an average of 3.37 degrees of flexion deformity. A 4 mm augment led to an average of 6.68 degrees fixed flexion, whilst a 6 mm augment produced 11.38 degrees. To correct 10 degrees flexion deformity, an additional 6 mm distal femoral bone resection is required.
In conclusion, additional distal femoral bone resection may not be as an effective strategy as previously believed to correct fixed flexion deformity in total knee arthroplasty.
