Metal-on-metal: articulations for the new millennium.
Implants with metal-on-metal articulations (Metasul, Sulzer Medica, Winterthur, Switzerland [now Zimmer, Warsaw, IN]) have been used in nearly 300,000 total hip replacements. In three different clinical studies, clinical success has been demonstrated using this implant as measured by Harris hip scores, patient self-assessment, and assessment of mechanical complications. Of a study group of 924 patients who received this implant, the only reported complications were mechanical, incldding two cup loosenings (0.2%) and 36 dislocations (4.0%). In a randomized study, clinical resultsfor the group that received implants with metal-on-metal articulation were comparable to those of the ceramic-on-polyethylene (control) group. Reports assessing retrieved implants with metal-on-metal articulation demonstrate low annual linear wear rates and no consequences of elevated cobalt ion levels at follow-up from 4 years to 26 years. In light of these data, the continued ise of metal-on-metal articulations is recommended for any patient who does not have compromised renal function.