CLINICAL AND RADIOLOGICAL FACTORS AFFECTING EARLY OUTCOME OF METAL ON METAL SURFACE ARTHROPLASTY OF THE HIP.

Abstract

Ninety-four hips with a mean patient age 34.2 (range 15– 40) with a metal/metal surface arthroplasty (SA) were reviewed with 71% men and 14% with previous surgery. The Chandler risk index was calculated as well as the SA risk index (SARI). At a mean follow-up three years, three hips were converted at a mean of twenty-seven months (two to fifty), and ten patients had significant radiological changes. Mean SARI for the thirteen problematic hips versus remaining hips was significantly higher, 4.7 and 2.6, respectively (p=0.00). If SARI > 3 the relative risk of early problems is twelve times greater than if SARI ≤3.

The purpose of this study was to evaluate the early outcome of a hybrid metal on metal surface arthroplasty of the hip in patients forty years and younger and identify potential risk factors.

Surface Arthroplasty Risk Index can help identify patients who may be at increased risk of early failure following metal on metal surface arthroplasty.

Proper patient selection and careful surgical technique may minimize early failures with the re-introduction of surface arthroplasty of the hip.

Ninety-four hips mean age 34.2 (range 15– 40) with metal/metal surface arthroplasty (SA) were reviewed with 71% men and 14% with previous surgery. The Chandler risk index was calculated and SA risk index (SARI). Mean follow-up three years (range 2–5), three hips were converted at a mean of twenty-seven months (2–50), and ten patients had significant radiological changes. Mean SARI for these thirteen problematic hips versus remaining hips was significantly higher, 4.7 and 2.6, respectively (p=0.00). The mean angle between the prosthesis stem and femoral shaft in the problematic group was significantly smaller than the remaining hips (p=0.03): 133° and 139°, respectively. If SARI > 3 the relative risk of early problems is twelve times greater than if SARI ≤3.