Several studies have described the relationship between the joint line and bony landmarks around the knee. However, high inter-patient variation makes these absolute values difficult in use. This study was set up to validate the previously described distances and ratios on calibrated full limb standing X-rays and to investigate the accuracy and reliability of these ratios as a tool for joint line reconstruction One hundred calibrated full-leg standing radiographs obtained from healthy volunteers were reviewed (fig 1). Distances from the medial epicondyle, the lateral epicondyle, the adductor tubercle, the fibular head and the proximal center of the knee (CJD) to the virtual prosthetic joint line were determined (fig 3). This prosthetic joint line was created by introducing a virtual distal femoral cutting block with a valgus angle of 6° on the full-leg radiographs. The adductor ratio was defined as the distance from adductor tubercle to the joint line divided by the femoral width. The correlation with the femoral width, the CJD and the limb alignment was analysed using linear regression analysis. The accuracy and reliability of the use of the ratio of the distance of the adductor tubercle, the medial epicondyle and the CJD relative to the femoral width to reconstruct the joint line was calculated.Introduction
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