In total knee arthroplasty, a posterior condylar line and so-called anterior-posterior axis are available to decide the rotational alignment of the femoral component. In this study, the reliability of these two axes was evaluated.We evaluated 84 knees (42 osteoarthritic knees in 40 patients and 40 normal knees in 40 volunteers). A computed tomography (CT) scan was taken at the level of the femoral epicondyle. On the CT image, the two axes and the epicondylar line were constructed on each image, and the relationship of the three axes was evaluated.The angle between the epicondylar and posterior axes was 5.8°±2.7° in the normal knees and 6.3°±2.1° in the osteoarthritic knees. The angle between the epicondylar axis and the perpendicular to the anteroposterior axis was 2.3°±3.1° in the normal knees and 0.6°±3.3° in the osteoarthritic knees.The posterior condylar axis was more reliable compared to the anteroposterior axis in the osteoarthritic knees.
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