Abstract
We report the radiographic evaluations of 70 hips followed up among 140 hips during a 10-year period after rotational acetabular osteotomy (RAO) in our department. Sharp angle, center-edge (CE) angle, stage of hip arthrosis at surgery, and shape of the femoral head (acetabular head index/deformity index of the femoral head) were used as factors for evaluation. The stage was based on quantification of remaining joint space under load on the x-ray image of bilateral hips (front view). Cases were classified into five stages (early-, initial-, early advanced-, late advanced-, or end-stage); the advanced-stage, according to the stage classification of the Japanese Orthopaedic Association, had been divided into two stages according to Okano et al. Hips having advanced disease or an implanted prosthetic joint were classified as the deterioration group, those unchanged as the no change group, and those having improved disease as the improvement group. We investigated the relationship between each factor and change at the postoperative stage. The mean postoperative period was 16 years and 11 months in 70 hips studied at the last examination. The radiographic findings revealed deterioration in 24 hips, of which 5 had been implanted with a prosthetic joint. No change and improvement were observed in 41 and 5 hips, respectively. Many results showed that the more advanced the progressive stage before surgery, the greater the deterioration after surgery. Between preoperation and the last examination, sharp angles decreased by 23.0° on average, and the CE angles increased by 36.0° on average, respectively. There were no significant differences in the rate of change of sharp angles and CE angles among the deterioration, unchanged, and improvement groups. Acetabular head and deformity indices changed from 56.4 and 1.42 on average preoperatively to 55.9 and 1.68 on average at the last examination, respectively. There was a significant difference in the rate of change of the mean deformity index of the femoral head only from preoperation to the last examination in the no change group when these indices were assessed by group. These results suggest that the preoperative stage, but not the sharp angle or the CE angle, has an effect on post-surgery stage changes. We cannot deny the possibility that the shape of the femoral head also has some effects. Compatibility of the acetabular roof and the femoral head may be important for the progression of disease stage.
