Low-friction arthroplasty in severe acetabular dysplasia.

Eighty consecutive low-friction arthroplasties in 64 patients with secondary arthritis due to severe acetabular dysplasia (Crowe grades III and IV) are analyzed. Two groups of patients were considered. In group 1 over 20% of the cup was not covered by the acetabulum and was reconstructed with a femoral head graft (32 cases; in group 2) a femoral head graft was not used because the cup was adequately covered (48 cases). The mean follow-up period was 9.4 years (range, 3-17 years) for group 1 and 8.8 years (range, 3-18 years) for group 2. Early complications were frequent (19%). To study long-term results only 78 hips were assessed since two patients were excluded due to deep infection. In these 78 hips, group 1 patients showed "better" results after 16 years (69.6% good results) than group 2 (nongraft procedures) (52.2%), but these differences were not significant (P > or = .05). Early cup loosening was more frequent in group 2 than in group 1, and good coverage was obtained in 91% of the group 1 cups and in 71% of the group 2 cups (P > or = .05). Acetabular cup loosening was not correlated with acetabular cup position. Bone-grafts appeared consolidated in all cases, but resorption areas were frequently observed. Radiographic stem aseptic loosening appeared in 10 cases, cortical hypertrophy in 7 cases, and endosteal osteolysis in 3 cases. Although limb discrepancy was frequent in both groups (75%), the average discrepancy was 1.7 cm.