METAL-ON-METAL HIP RESURFACING FOR OSTEONECROSIS

Abstract

Introduction: The results of total hip arthroplasty and prior hip resurfacing designs with polyethylene in osteonecrosis (ON) have been less satisfactory than for patients with other etiologies. Metal-on-metal resurfacing is bone preserving and permits a wide selection of revision options for young patients.

Methods: From a cohort of 1000 hips of all etiologies, 84 hips (70 patients, average age 40 years), with ON Ficat Stage III (19 hips) and IV (65 hips) were treated with hybrid metal-on-metal resurfacing. There were 81% men and 19% women. One-third of the patients had previous surgeries including core decompression (17 hips), hemi-resurfacing arthroplasty (3 hips), pinning (5 hips), free vascularized fibula graft (2 hips) and Judet graft (1 hip). Seventy-one hips (85%) presented with femoral head defects larger than 1 centimeter.

Results: The average follow-up was 6 years (1-1). The average femoral component size was 46 millimeters. The clinical scores were comparable to that of the rest of the cohort except for the activity score which was lower in average (7.0 vs. 7.5, p=0.0015). Three hips were revised: 2 for femoral loosening at 22 and 61 months, and one for a fracture of the acetabular wall (over reaming in osteopenic bone) with protrusio of the cup one day post surgery. There were no other complications. Radiographic analysis revealed 3 cases of neck narrowing (1 bilateral) and 2 cases of femoral radiolucencies in 3 zones around the metaphyseal stem. The Kaplan-Meier 5-year survival estimate was 97.1% (95% Confidence Interval 88.7 to 99.2). There have been no femoral component loosenings for patients implanted after August of 1997.

Discussion: Our results highlight that the etiology of osteonecrosis itself does not constitute a contraindication for resurfacing despite large defects. Technique is critical in achieving initial femoral fixation and promoting long-term durability.