Prophylaxis of secondary osteoarthrosis with spherical osteotomy in residual acetabular dysplasia. Analysis of predictive factors of success.

The aim of this study was to evaluate whether or not spherical acetabular osteotomy prevents progression of osteoarthrosis in hip joints with residual dysplasia and which radiological parameters can be used postoperatively as predictive factors concerning the outcome. Sixty-eight out of 78 joints were re-investigated with a mean follow-up of 11.2 years after the index operation. Twenty-three Wagner type 1 and 45 type II osteotomies were performed. At surgery, the mean age of the patients was 26 years; 90% of joints showed no or mild degenerative changes, 26% presented with a good or excellent Harris hip score. At follow-up, 28% of patients had improved in function, mean Harris hip score rated 75 points. The mean center-edge (CE) angle improved from -4 degrees to 18 degrees, and the anterior center-edge (ACE) angle from -4 degrees to 26 degrees. The weight-bearing zone of the acetabulum showed an acetabular index (AC) angle of 27 degrees preoperatively and 14 degrees postoperatively. Statistical analysis proved a significant correlation between the normal postoperative values of the acetabulum/femoral-head index of Heyman and Herndon and the absence of degenerative joint changes at follow-up. 73.5% of the hips had not markedly progressed to secondary osteoarthrosis, but 26.5% of joints had deteriorated: 7.4% of them due to perioperative complications and early postoperative trauma. In 8.8% (severe dysplasia) only partial reorientation was possible, which explains the progression of arthrosis, but 10.2% progressed despite sufficient correction.