Abstract
Introduction
Stiffness post Total Knee Replacement (TKR) is a common, complex and multifactorial problem. Many reports claim that component mal-rotation plays an important role in this problem. Internal mal-rotation of the tibial component is underestimated among surgeons when compared to femoral internal mal-rotation. We believe the internal mal-rotation of the tibial component can negatively affect the full extension of Knee. We performed an in-vivo study of the impact of tibial internal mal-rotation on knee extension in 31 cases.
Method
During TKR, once all bony cuts were completed and flexion/extension gaps balanced, we assessed the degree of knee extension using the trial component in the setting of normal tibial rotation and with varying degrees of internal rotation (13–33°, mean 21.2±4.6°). Intra-operative lateral knee X-ray was done to measure the degree of flexion contracture in both groups. We also compared the degree of flexion contracture between CR and PS spacers.
Results
The average degree of knee flexion contracture with normal rotation of the tibial component was 0.7±4.1° (range: −9 to 10), whereas after tibial internal rotation was 7.3±4.6° (range: −1 to 23) (P – value:0.001). The increase in the flexion contracture deformity was higher with PS spacer (7.18±2.61) than with CR spacers (5.22±2.05)
Conclusion
The internal mal-rotation of the tibial component limits the ability of the tibia to externally rotate on the femur, thereby limiting full knee extension and leading to flexion contracture.
