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.