The Searching Method for Appropriate Position of Socket in Total Hip Replacement

Mechanical performance of artificial hip joints has been improved by basic researches on various fields, but there are some cases where a reoperation is required within a few years. The inappropriate position of the installed socket is considered as a cause of reoperation. Appropriate installing of socket makes enough amount of contact area between the socket and the pelvis, so that the hip joint stays stably. Actually, the socket position is decided by means of a careful examination on medical scene. But there are hardly mechanical and numerical examinations, the surgeon's experience weighs heavily in the decision of socket position. We propose SSM (Swelling Sphere Method) to search an appropriate socket position based on the area. In order to evaluate effectiveness of SSM, first, we compared it with a general optimization method. Next, the SSM was applied to obtain the appropriate socket position for a geometric model of pelvis constructed from a series of CT photographs of a patient. Further, by using a finite element analysis, we found that the socket position has an equal aptitude to surgeon's decision from the mechanical point of view.