Ganz reinforcement ring for reconstruction of acetabular defects in revision total hip arthroplasty.

BACKGROUND: In revision total hip arthroplasty, bone loss due to loosening and migration of the acetabular component makes fixation of a new implant difficult. The purpose of this study was to evaluate the clinical and radiographic outcomes of the use of the Ganz reinforcement ring with nonstructural allograft in the reconstruction of acetabular defects.

METHODS: Sixty-one acetabular revisions performed with use of the Ganz reinforcement ring and nonstructural allograft, between 1989 and 1992, in fifty-seven patients with aseptic loosening met our selection criteria. Eleven hips in eleven patients were lost to follow-up, leaving fifty hips available for evaluation five years or more following surgery. According to the American Academy of Orthopaedic Surgeons classification, twenty-four acetabular defects were Type II, twenty-four were Type III, and two were Type IV. Clinical and radiographic evaluations were carried out at a mean of six and nine years after surgery. Twelve more patients were lost to follow-up before the most recent evaluation.

RESULTS: The mean Merle d'Aubigné composite score increased significantly compared with the preoperative score (p < 0.001). There were seven failures: six cases of aseptic loosening and one case of septic arthritis. Graft incorporation and bone remodeling occurred in all hips but three in which the ring fixation had been inadequate at the time of surgery. The Kaplan-Meier survivorship rate, with use of revision or loosening of the component as the criterion of failure, was 81% at ten years. Inadequate fixation of the implant at the time of surgery was the only multivariate predictor of failure (p = 0.003).

CONCLUSIONS: Patients treated with acetabular revision with a Ganz reinforcement ring had reconstitution of periacetabular bone stock as well as good clinical and radiographic results, provided that the ring had been fixed adequately at the time of surgery. This procedure may not be the preferred approach for reconstructing segmental defects of the medial wall or pelvic discontinuity.