A CT-based analysis of the variation in the rotational reference axes of the distal femur and inter-epicondylar distance as a predictor of joint line position - A new algorithm for computer navigation and conventional TKR techniques

摘要

Introduction: The landmarks commonly used to achieve correct rotation of the femoral component are the posterior condylar axis, the surgical and clinical epicondylar axes and the anteroposterior axis (Whiteside's line) of the distal femur. The design features of most commonly used conventional jig based total knee replacement instrumentation assume a constant relationship of 3?external rotation between the posterior condylar axis and the epicondylar axis. We hypothesize that there is no consistent relationship between these rotational reference axes. The position of the joint line is a key factor in the stability and optimal functioning of the knee in both primary and revision knee replacement. Accurate restoration of the prosthetic joint line to the level of the natural joint line is technically difficult to achieve and there is no reliable method to achieve this objective. We hypothesise that there is a constant ratio between the inter-epicondylar distance and the perpendicular distance from this inter-epicondylar line to the joint line.