Failure mechanisms of total hip resurfacing: implications for the present.

In the past decade, there has been a renewed interest in hip resurfacing due to recent design improvements. It is unclear whether the recent improvements have accounted for all of the previous failure mechanisms. We determined the long-term performance of hip resurfacing, while paying special attention to the mechanisms of failure. We retrospectively reviewed 62 patients (65 hips) who had Indiana conservative hip prostheses implanted between 1977 and 1981. Forty-one of 62 joints had failed, representing a failure rate of 66%. The time to failure averaged 9.7 years with a range of 6 months to 21.5 years. There were 23 femoral failures (37%). Eleven were caused by femoral fracture, and 12 were caused by femoral loosening. All late femoral failures (greater than 10 years postoperatively) showed narrowing of the femoral neck secondary to stress shielding. There were 18 acetabular failures (29%) with 10 failing secondary to polyethylene wear and eight failing secondary to acetabular loosening. Failure of the Indiana conservative hip prosthesis continues over time related to femoral and acetabular failure mechanisms. These data should be considered in the context of growing enthusiasm for resurfacing with new bearing surfaces and cementless fixation.