[Design of cementless femoral prostheses adaptive to secondary osteoarthritis of the hip joint].

In order to design cementless femoral prostheses for the femoral canal of Japanese patients with secondary osteoarthritis of the hip joint, we analyzed the anatomical features of the hip joint in 85 hips of 55 patients with osteoarthritic hip and 90 hips of 60 subjects with normal hip in three-dimensional CT images. We found that 9 different stem designs varying in width and proximal radius were required to accommodate the hips with secondary osteoarthritis. In normal hips, the anatomical features of the proximal femoral canal to the femoral length was directly proportional. Thus, the values for the proximal radius, the position of the isthmus, off-set value and width of the stem for femoral neck fracture and aseptic necrosis of the femoral head should increase with the stem size, but the ratios of the increase were found different. The mean taper angle from the lower end to the lesser trochanter to the upper end of the isthmus was 3.8 degrees regardless of femoral length.