METAL-ON-METAL HIP RESURFACING FOR OBESE PATIENTS

Abstract

Introduction: The purpose of the present study was to assess the clinical results of metal-on-metal hip resurfacing for the treatment of hip arthrosis in patients with a BMI of 30 or more.

Materials and Methods: From a consecutive series of over 1000 Conserve® Plus metal-on metal hybrid resurfacings, 148 hips were resurfaced in 138 patients with a BMI of 30 or more at the time of surgery. Average age was 49.4 years (range, 18 to 72) with 88% male. The average weight was 104.6 kg (range 74 to 164) and average BMI 33.4 (30.0 to 46.4). “Idiopathic” OA was the dominant etiology with 80.0%. The femoral metaphyseal stem was cemented in 43 hips and press-fit in the remaining 105. All acetabular components were press-fit.

Results: Average follow-up was 6.2 years (range, 2.0 to 10.2). UCLA hip scores improved significantly (pain: 3.5 to 9.4; walking: 5.9 to 9.5; function: 5.4 to 9.2; activity: 4.3 to 7.1). There were no cases of acetabular or femoral component loosening. 2 hips (1.4%) were revised, 1 for femoral neck fracture and one for acetabular cup protrusio the day after surgery in a bilateral patient with poor bone quality. 3 hips (2.0%) have radiolucencies about the femoral stem. All are asymptomatic and none have progressed for an average of 5.2 years (range 4.5 to 6.8). There were no revisions for any reason and no radiolucencies observed in patients with a BMI of 35 or more (n=27).

Conclusions: Metal-on-metal resurfacing arthroplasty of the hip is performing extremely well in patients with high BMI, in contrast with the results of conventional THR. These results are in agreement with our previous finding that weight is protective of prosthesis durability with resurfacing. This could be explained by a greater fixation area on the femoral side, a greater bone mineral density, and a slightly reduced (but still high) activity level in this patient population compared to patients with a BMI less than 30 (7.1 vs 7.6, p=0.002).