Metal-on-Metal Total Hip Arthroplasty: The Concerns

Abstract

The metal-on-metal bearing couple in having a resurgence in clinical applications seen in both total hip resurfacing technologies. The most noteworthy advantage of a metal-on-metal implant is the improved wear characteristics seen both in vitro on wear simulators and in vivo with retrieved implants. All bearings have disadvantages, and a metal-on-metal bearing is no exception. Concerns exist regarding the generation of metal ions seens in both the blood and urine of patients with metal-on-metal implants. These elevated metal ions have theoritical, although not proven, risks related to carcinogenic and biologic concerns. Additionally, concerns exist regarding hypersensitivity, increased incidence of instability and increased costs. Specific patient selection issues arise with metal-on-metal implants. The current generation of implants has only early and mid-term results available, with no long-term series yet published Therefore, although a metal-on-metal bearing may be considered a viable alternative to either polyethylene or ceramic implants, outstanding and unresolved issues continue to exist with this bearing, as they do with the alternatives.