ROTATIONAL LANDMARKS AND SIZING OF THE DISTAL FEMUR IN TOTAL KNEE ARTHROPLASTY

In 100 knees undergoing a total replacement, the angles between the ta ngent line of the posterior condylar surfaces, the anteroposterior axi s as described by Whiteside, the transepicondylar line, and the trochl ear line were measured. Also measured were the sulcus angle, the trans epicondylar width, the height of the condyles, and the thickness of th e various cuts. Radiologic measurements made were: the mechanical angl e, the hip center-femoral shaft angle, the transcondylar angle, and th e tibial plateau-tibial shaft angle. The mean values of these measurem ents were calculated, and comparisons were made according to gender an d the mechanical axis using the Student's t test. Correlations between the various measurements were calculated. The transepicondylar axis w as found to be a reliable landmark to properly rotate the femoral comp onent, and was easier to locate at surgery than the anteroposterior ax is. In trochlear dysplasia and in some valgus knees, relying on the an teroposterior axis can induce an excessive external rotation of the fe moral component, and the opposite can happen in some varus knees. The anterior extent of the condyles is highly variable in arthritic knees, and cannot be used to orient the prosthesis. The ratio between the tr ansepicondylar width and the height of the condyles is constant, but s ome narrow femora could require narrower implants to avoid medial-late ral overhang of the femoral component.