Mid-term results of a polyethylene-free metal on metal articulation

Polyethylene wear debris, increasing longevity and the utilization of implants in young patients have renewed interest in alternative long-term joint replacement solutions. A polyethylene-free metal-onmetal acetabular system was designed with the intent of improving the longevity of total hip arthroplasty. A multicenter investigational device exemption study began in December 1995, and 193 with 195 involved hips were enrolled into this prospective, randomized, controlled study. Ninety-eight patients with 99 involved hips have a minimum five-year follow-up. Eleven patients (12 hips) are deceased. For those having five-year follow-up, 46 hips were performed with polyethylene (UHMWPE) liners and 53 hips were performed with metal (cobalt-chromium) liners. The average follow-up, average Harris Hip Score improvement, and radiographic analysis were not statistically different between the two groups. The mean follow-up was 5.7 years for both groups. Mean postoperative Harris hip score was 94.3 in the polyethylene group and 93.1 in the metal group. Roentgenographic analysis revealed no femoral stress shielding or osteolysis in either group. Three patients in the polyethylene group and none in the metal group had evidence of acetabular radiolucencies of less than 1 mm in one or more zones. No difference in acetabular stress shielding was noted. No acetabular revisions have been performed and none are pending in either group. There have been no device-related complications in either group. Based on these mid-term results the authors conclude that a metal-on-metal articulation may represent a viable alternative for total hip arthroplasty in the young, high demand, active patient.