Determination of the weight bearing portion of the acetabulum using simulated transverse acetabular fractures

Knowledge of the location of the weight bearing portion of the acetabulum would assist orthopaedic surgeons in their decision of how to manage a given acetabular fracture. Using simulated transverse acetabular fracture, the location of the weight bearing region of the acetabulum was investigated. Twelve fresh frozen hip specimens from six cadavers were tested. For each specimen, both the femur and acetabulum were potted and mounted in aluminum fixtures and the acetabulum was positioned in 25/spl deg/ of flexion and 20/spl deg/ of abduction. Each specimen was tested intact and then with successive transverse acetabular fractures having roof-arc angles of 60/spl deg/, 50/spl deg/, 40/spl deg/, 30/spl deg/, and 20/spl deg/. For the intact specimens and then after each fracture, compressive loading to 800 N, 1200 N, and 1600 N was completed (four cycles each). A specimen was considered to be stable if the four loading cycles were completed without gross dislocation. For each trial, translation of the femur was measured and the stability or dislocation of the specimen was noted. The number of stable specimens decreased both with increasing applied load and more superior fractures. Additionally, translation of the femur within the acetabulum increased with increasing applied load, as well as with more superior fractures. The roof-arc angle of the fracture, as well as the magnitude and direction of the applied loading, significantly affect hip stability.