Long-term results of a modified Spitzy shelf operation for developmental dysplasia of the hip in adults and adolescents

The purpose of the current study was to retrospectively evaluate the long-term outcome of our shelf operation for acetabular dysplasia in adults and adolescents. We evaluated the outcome of shelf operation performed in 35 hips of 32 patients with acetabular dysplasia between 1978 and 1996. The mean age at the time of surgery was 30.6 years, and the mean follow-up period was 25.9 years. The pre-operative stage of osteoarthritis was Tönnis grade 0 in 12 hips and grade 1 in 23 hips. Clinical evaluation using the JOA hip score showed more than 85 of 100 points over 25 years. Radiologically, acetabular index was significantly improved after operation. Osteoarthritis deteriorated to grade 3 in 8 of 35 hips (23%) at an average 17.1 years, and accordingly 3 of those 8 hips were converted to THA. The shelf height was significantly higher in those which advanced to grade 3 than in those which did not. There were no significant differences in mean sharp angle, CE angle, AHI, and roundness index. Mean survival was 74% with grade 3 as the endpoint and 72% with THA conversion as the endpoint. Shelf operation provides satisfactory long-term outcome in adults and adolescents with acetabular dysplasia. Higher location of the shelf is a risk factor for advancement of osteoarthritis, whereas sphericity of the femoral head does not affect the long-term results. Further studies are needed to clarify the risk factors about OA progression among the patients with acetabular dysplasia, like as the assessment of three-dimensional morphology of hip joints.