Jinko Zoki

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To investigate the ideal design of cementless total hip systems, especially on the stem side, experimental and clinical studies were performed. First, a cementless total hip system for canines was used to observe the effect of rigid stem fixaition. Effect was judged by roentgenogram and contact microradiogram (CMR). CMR revealed a large amouns of new bone formation around the stem in cases that showed no clear zone in X-ray findings. In contrast, there was less bone formation in cases showing a wide clear zone with a stem smaller than the diameter of the intramedully canal. Next, in follow up studies of 26 clinical cases in which Y type cementless total hip systems were used, it was found that better results could be expected using a stem of a size suitable for press fit contact. Finally, computer calculation using a rigid body spring model was carried out to find the ideal stem design and to determine optimal operative procedure. The ideal osteotomy angle from the femoral neck to the horizontal line was 35 degrees. In addition, the stem should be 20mm longer than the original Y type.

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