Three-dimensional evaluation of acetabular coverage of the femoral head in normal hip joints and hip joints with acetabular dysplasia.

Compared with the assessment by data processing-coupled CT scanning, three dimensional evaluations of the acetabular coverage of the femoral head from a plain X-ray picture of the hip joint is found to be a simpler and easier procedure. In addition, the calculated values agree well with those obtained by CT in reconstruction. Consequently, this method is of great value in evaluating the severity of diseases of the hip joint. The acetabular coverage of the anterior portion of the hip joint is decreased in the elderly even if the hip joint is normal. Because this decrease may result in primary arthrosis deformans, it should be studied further. Rotational acetabular osteotomy (RAO) is a far better method than Salter's for the early stage of coxarthritis. The present study concludes that it is vitally important to maintain the normal ratio of the anterior and posterior coverage and the shape of the acetabular coverage in the treatment of coxarthritis.