Introduction: Hip instability is a complex and challenging problem. In experienced units, up to 4% of patients undergoing total hip arthroplasty will require revision surgery to treat hip instability, with only 60% of these treatments being successful. Many authors reporting results with various constrained systems available have described dislocation rates post implantation of the constrained component of 4% to 29%.

Method: The thirteen patients who underwent placement of a constrained component as a revision procedure in our unit from 1989 to 2000 were reviewed.

Results: The indications for revision surgery included recurrent dislocation in eight and intraoperative instability in five revision hip arthroplasties. No patients were lost to follow up. The average follow-up was 43 months(range 14 to 121). The average age at time of surgery was 73 years(range: 52 to 84 years). No component has been revised. The average hip score after revision surgery was 72(range: 52 to 89). There have been no episodes of dislocation of the constrained arthroplasty. In seven cases the constrained arthroplasty was implanted into a previously placed well fixed shell.

Conclusion: Constrained acetabular components were a highly effective tool in the treatment of hip instability.