Changes in the pelvis after the Chiari and Salter osteotomies.

Pelvic osteotomies were simulated on a macerated female pelvis using the techniques of Chiari and Salter. The effect of varying amounts of medial or angular displacement upon the actual and radiological displacement of the acetabulum were then measured and compared. With the Chiari osteotomy, increasing medial displacement in the range 0.5-2.5 cm appeared to give a wider acetabular roof but at the expense of rotating the true acetabulum to face more laterally, thereby reducing the width of articular cartilage in the weight-bearing area from that present originally. However no disturbance of the symphysis was detected. In the Salter osteotomy it was found that the radiologically determined angle was up to 50% greater than the true angle. With an increasing true osteotomy angle up to 30 degrees steady improvement in the CE angle developed, but beyond 30% significant lateral displacement of the acetabulum, lengthening of the leg and disturbance of the symphysis pubis occurred. It is concluded that the osteotomy opening should not exceed 30 degrees in the Salter procedure.