To evaluate the midterm result of patients who underwent rotational acetabular osteotomy for the treatment of acetabular dysplasia.

The clinical and radiographic outcomes of 36 patients, who underwent rotational acetabular osteotomy between January 1987 and September 1998, were evaluated after a minimum followup of five years. The mean follow-up period was 8.6 years. The clinical evaluation included recording the level of pain, the ambulation status and range of motion according to the d'Aubigne and Postel system. Radiographic analysis included the C-E angle of Wiberg, the acetabular roof obliquity, and arthritis grade of Tonnis.

The average Postel score increased from 12.5 points preoperatively to 15.7 points at the final follow up. All the radiologic indices improved after surgery. In five hips (13.1%), there was a progression of arthritis prior to surgery.

Rotational acetabular osteotomy is a valuable procedure for preventing the progression of early osteoarthritis in patients with a dysplastic hip. However the results were unsatisfactory for hips with more advanced osteoarthritis.