Follow-up study of rotational acetabular osteotomy for the osteoarthritis of the hip joint with special attention to the remodeling of the grafted bone

Rotational acetabular osteotomy originally reported by Tagawa and Ninomiya has become a common procedure in Japan for dysplastic osteoarthritis of the hip joint. It enables us to reconstruct the joint with increased covering of the acetabulum over the femoral head and, at the same time, medialization of the laterally displaced femoral head. This study evaluated the clinical results of surgery and clarified the process of acetabular remodeling on roentgenography. Materials: Of 220 patients who underwent the osteotomy between 1986 and September 1996, 53 patients (60 joints) with more than 5 year follow-up data were selected for the study. There were 4 male (4 joints) and 49 female (56 joints) patients. Preoperatively, osteoarthritis was classified into 3 stages: pre- osteoarthritis (31 joints), early osteoarthritis (20 joints) and progressive (9 joints) stages. Methods: The patients were examined and the clinical results were assessed by the Japanese Orthopedic Association Hip-Rating System (JOA score). On roentgenography, the time course of changes in the osteotomized and bone-grafted acetabulum was divided into 1) the period when the grafted bone appeared to be 'accepted', 2) that when the margin of the graft became smooth, 3) that when the graft appeared to be homogeneous, and 4) that when the graft appeared solidly united to the host bone. Patient age at surgery, the stage of osteoarthritis, the CE angle (angle indicating lateralization of the femoral head) and radiological changes were correlated. For statistical analysis, t- test was used. Results: The average total JOA score (max. 100) improved from 72.6 (range 42-90) to 94.5 (range 76-100). The improvement in pain score (max. 40) was most remarkable : from 20.7 (range 0.30) to 36.9 (range 30-40). Greater clinical improvement was obtained in the pre- and early osteoarthritis groups than in patients with progressive osteoarthritis. The average preoperative CE angle of 1.8 degrees (range-35-18) increased to 37.3 (-5-50) at follow-up. However, in 2 patients, progression of osteoarthritis was noted on radiography. On average, remodeling of the acetabulum took 39.1 months to complete, but more time was needed when the patient was older and the CE angle smaller. Conclusions: Clinical improvement after rotational acetabular osteotomy was satisfactory in the majority of patients. Improvement was more prominent when the stage of the osteoarthritis was earlier and the CE angle was smaller. Remodeling of the treated acetabulum was completed within 3 years and 3 months, but the process was slower when the patient was older and the CE angle was smaller. Therefore, the timing of initiating postoperative weight-bearing should be individualized according to the severity of the disease and the age of the patient.