Development of SH type total hip prosthesis

We compared the conventional hip prosthesis with a newly developed SH-type hip prosthesis by examining the degree of true roundness, sphericality, and surface roughness of the joint, as well as evaluating the metal stem properties. The roundness, sphericality and surface roughness were evaluated using Ogawa's criteria. Ogawa classified these values into 3 cate-gories, A (5 points), B (3 points), and C (1 point), and the overall scores into 4 categories, A (21 points or more), B (20-18 points), C (17-15 points), and D (14 points or less). In class A, roundness was less than 0.1μm and for the femoral head and less than 20μm for the acetabular cup, sphericality was less than 5μm and less than 50μm, and surface roughness less than 0.1μm and less than 0.5μm (maximal roughness of the cup was 5μm), respectively. Applying these criteria, the total score for the SH-type hip prosthesis placed it in class A. The strength and micro-cleanliness of the stem itself were sufficiently satisfactory.

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