Cementless Total Hip Arthroplasty in Crowe III and IV Dysplasia: High Hip Center and Modular Necks.

Background: Total hip arthroplasty (THA) in severe developmental dysplasia of the hip (DDH) is a challenging procedure. The most used techniques involve anatomic cup positioning, augmentation femoral osteotomy. However, anatomic cup positioning is not always feasible in severe DDH and osteotomy nonunion may ensue. The purpose of the study was to assess the survivorship, the hip score results, the radiological parameters (fixation, loosening, component position) of a large cohort of patients with Crowe III and IV DDH, treated with high hip center and modular necks THAs.

Methods: Eighty-four THAs in Crowe III and IV DDH were evaluated, achieving a final follow-up of 15.1 years. All the patients were treated with the same cementless implant (modular necks and ceramic-on-ceramic coupling) and the same approach (high cup placement with slight medialization). The patients were clinically evaluated (Harris Hip score and Merle d'Aubigne and Postel score). A radiographic evaluation was performed, analyzing the orientation of the cup.

Results: Eighty patients were available at the last follow-up. The clinical scores were good at the final follow-up. Two sciatic lesions occurred: one patient fully recovered. The overall survivorship was 90.5% at 15 years: only 2 cases of aseptic loosening were reported. The mean center of rotation height was 33 ± 8 mm and the medialization was 30 ± 5 mm.

Conclusion: A high cup placement with slight medialization is a valid technique in DDH patients. A good restoration of the offset, ceramic-on-ceramic coupling and a porous socket may provide durable results, overcoming the effects of increasing joint reaction forces related to high cup placement.