Introduction. Dysplasia of the hip is the commonest cause of secondary osteoarthritis. One treatment is periacetabular osteotomy such as rotational acetabular osteotomy(RAO). These procedures have generally produced satisfactory mid- and long-term results, but unfavorable results have been reported in a few cases. We evaluated the 10-year results to determine the factors of prognostic importance.

Methods. We studied 91 patients (100 hips) at prearthritis or early stage. The mean age at surgery was 36 years (13 – 58) and mean follow-up period was 11 years (8–16). 81 were women (89 hips) and 10 were men (11 hips). Clinical follow-up was done using the system of Merle d’Aubigne. Radiologically, CE angle, AC angle and head lateralization index (HLI) were measured prior to surgery, 3 months postoperatively and at follow-up. Postoperative joint congruencies were classified into four grades.

Results. The mean clinical score significantly increased from 14 to 17 and only in 4 cases the mean score decreased. CE angle, AC angle, and HLI significantly improved after surgery. Progression of osteoarthritis was radiologically observed at follow-up in 7 hips. Kaplan-Meier survivorship analysis predicted the rate of prevention of osteoarthritic progression at 10 years as 93%. Parametric survivorship analysis using the Cox hazards model indicated that postoperative joint congruency is a risk factor for progression of osteoarthritis.

Discussion/Conclusion. Our findings have suggested that RAO is valuable in preventing osteoarthritic progression for at least 10 years. If risk factors can be reduced, a longer operative effect may be expected.

We have studied whether the state of the articular cartilage at the time of rotational acetabular osteotomy for dysplasia of the hip affects the outcome 2 to 5.5 years after surgery. Arthroscopy in 57 patients (59 joints) at the time of the operation showed grade-0 changes in seven, grade-1 in nine, grade-2 in 17, grade-3 in 14 and grade-4 in 12 joints, according to the classification of Outerbridge. There was radiological evidence of the progression of arthritis in four joints which were classified at arthroscopy as grade 4.

Stepwise regression analysis showed that damage to acetabular or femoral articular cartilage significantly affected the progression of arthritis. We conclude that the short-term results of successful rotational acetabular osteotomy for dysplasia are affected by the state of the articular cartilage.

We studied nine patients who had had a transtrochanteric anterior rotational osteotomy, as developed by Sugioka, for osteonecrosis of the femoral head. At a mean of 2.5 years after the initial operation we carried out a histological study of the previously necrotic femoral head which had not shown collapse of the new primary weight-bearing site. In seven joints, there was proliferation of fibrous tissue in the dead trabeculae with vascular ingrowth. New bone covering dead trabeculae created the characteristic appearance of ‘creeping substitution’. However, these changes were limited and did not extend over the entire necrotic area. Dead bone remained in all the cases. In the other two heads we did not observe proliferation of fibrous tissue or vascular ingrowth, only dead trabeculae and dead bone marrow.