[Natural course of coxarthrosis in dysplastic hips].

We tried to determine the natural history of the hip and select the optimal treatment in 64 patients (94 hips with subluxation or dysplastic hips followed for more than ten years). Patients were classified into advanced and non-advanced groups according to radiographic analysis of the stage of the disease. Fourteen out of 43 hips (33%) developed early osteoarthritis (early OA) from pre-osteoarthritis (pre-OA) within an average of 9.4 years, while 34 out of 50 hips (68%) developed advanced-stage OA from early OA within an average of 7.7 years. In pre-OA, the CE angle, slope of the acetabular roof, acetabular head index, acetabular depth ratio and Japanese Orthopaedic Association (JOA) hip score were significant predictors, while in early OA, a broken Shenton's line, cranial joint space and JOA score were significant.