Hip resurfacing versus metal-on-metal total hip arthroplasty - are metal ion levels different?

A systematic review and meta-analysis of trials comparing hip resurfacing to metal-on-metal total hip arthroplasty was conducted to determine if there is a difference in serum metal ion levels in patients receiving these implants. EMBASE and MEDLINE databases were searched from inception to December 2010 for all trials involving the use of these devices. Eligibility for inclusion in the review were studies with 1. comparative trials that were both retrospective and prospective; 2. inclusion of a treatment arm receiving hip resurfacing; 3. inclusion of a treatment arm receiving metal-on-metal total hip arthroplasty; and 4. analysis of chromium and cobalt ions, or either, in patient serum or whole blood at a minimum of 1 year after implantation. The literature search identified 87 potential studies, of which 10 met the inclusion criteria. Pooled mean differences were calculated for serum cobalt and chromium ion levels. Mean differences for serum cobalt and chromium metal ions were not significantly different between hip resurfacing and metal-on-metal total hip arthroplasty patients, although there was a tendency for lower serum cobalt ion levels in patients receiving hip resurfacing. Larger prospective randomized trials are required to better substantiate a difference in metal ion levels occurring between these implants.