[A study on the stress analysis of the pelvis by means of the three-dimensional photoelastic experiments (author's transl)].
The processes are as follows: 1) Life-sized photoelastic models molded from a cadaver pelvis are made of Epoxy resin. 2) In order to practice the stress freezing process, the models are set to our original loading apparatus in the electric heater. The forces exerted on the hip models are both body weight and four kinds of muscular forces, those of the abductor, adductor, rectus femoris and gluteus maximus. 3) After the stresses are frozen in the models, they are cut off into slices to observe isochromatic and isoclinic lines. 4) In the stress analysis both the shear difference method and the double slice method are utilized to obtain more accurate stress distributions. And the results have been summarized as follows: 1) In the ring-shaped slices large stresses are observed especially at four areas; namely the central area of the iliac bone, the acetabulum proximal to the ilium, the pubic ramus and the area adjacent to the sacroiliac joint. The specific areas where hydrostatic pressure works are seen at two points in the deep acetabular cavity. 2) The principal stress lines of almost all slices tend to flow smoothly and monotonously along the ilium, the sacrum and the pubic bone, but as they approach the acetabulum they run in complex patterns and make some singular points. 3) Around the acetabulum the principal stress lines of one group run in concentric circles and those of the other group radiate in all directions from the center of the acetabulum at the upper half of the dome which supports the load. The stress here was 5 to 6 times greater than in the lower half of the dome. 4) The acetabulum is stretched vertically and deformed into an oval shape. The horse shoe-shaped articular facet is deformed as both beaks approach each other. 5) As for the slices of the pelvic ring the normal acetabulum tends to be obviously deformed as it holds or embraces the femoral head. As a result of this deformity the stability between the acetabulum and the head increases. On the other hand the dysplastic acetabulum shows none of those phenomena. 6) The iliac bone of the pelvic ring is deformed into the "S" shape and the pubic ramus the "C" shape, the "S" shape, or the "Z" shape depending on the limb position. The pelvic ring tends to be deformed into a heart shape during abduction.
D000077:Acetabulum / Q000502:physiology; D006801:Humans; D008953:Models, Anatomic; D010388:Pelvis / Q000502:physiology*; D013314:Stress, Mechanical