[A study of the stress distribution of the stem of the total hip prosthesis (author's transl)].
By attaching the strain gauges on the inner and outer sides of the stem of the total hip prosthesis composed of Müller, Charnley and domestic SOM type, the stress distribution was measured. At first, the center of the head of the prosthesis and the apex of the stem were adjusted to be on the vertical line, and a vertical load was placed on the uppermost end of the head, then the stress was measured. Next, the stem was fixed in the hole of a wood-block containing acrylic resin, and the load was placed on the head in neutral, 10 degrees valgus and 10 degrees varus position and in the direction same as the stem before fixation, then the stress was measured of respective position. In comparing the difference in stress distribution between the fixed and the non-fixed stem, the stress in the case of the fixed stem proved to be 17--32% that of the non-fixed one. The site where the maximum stress appeared was at the middle third of the stem in the case of the non-fixed stem, while it was at the neck and at the one fifth of the upper portion of the fixed one. In comparing the stress at the neutral, the valgus and the varus position, the stress at the valgus position was found to be minimum, and taking the stress at the neutral position as 100, it was 60--82, and at the varus position the maximum of 105--131 appeared.
D001696:Biomechanical Phenomena; D006621:Hip Joint; D006801:Humans; D007595:Joint Prosthesis; D008961:Models, Structural; D013314:Stress, Mechanical