Metal-on-metal hip implants have lost key support within the medical community after the California Technology Assessment Forum reversed the position it had adopted a year earlier supporting the hip resurfacing technique, a hip replacement option that uses metal-on-metal hip devices. The CTAF report was based on data from joint registries in England and Australia that found extremely high premature failure rates for some hip implant devices, such as DePuy’s all-metal ASR Hip Resurfacing System and ASR XL Acetabular system.
The hip resurfacing technique is offered as an alternative to traditional total hip replacement. The procedure consists of fitting the head of the femur with an all-metal cobalt-chrome cap while a matching metal cup is placed in the pelvis socket. The hip resurfacing procedure’s biggest benefits are that it spares most of the patient’s thigh bone, leaving the area intact for future surgeries, if necessary; increased mobility; and lesser chance of dislocating.
However, the inherent problem with hip resurfacing devices and other all-metal hip implants is that the cobalt-chromium parts rub together, releasing metal particles into the body, which when processed by scavenger cells, become corrosive metallic ions capable of destroying bone, muscle, and tissue. Many patients with all-metal replacement hips experience extreme pain, fracturing, dislocation, and a range of adverse symptoms related to metal poisoning.
Dr. Judith Walsh, the author of the CTAF report, said that the group’s previous support of the hip resurfacing devices took into consideration the lack of clinical trials comparing the performance of hip resurfacing devices with standard hip replacements in real patients. The CTAF’s reversal, she notes, is based on data from the foreign joint registries that revealed abnormally high failure rates for some resurfacing implants. Dr. Walsh notes in the report that little is known about the long-term health effects of the metallic ions the devices create within the body.
Believe it or not, some all-metal implants were not clinically tested before they gained U.S. Food and Drug Administration approval, including DePuy’s now-recalled ASR XL Acetabular System. DePuy’s ASR Hip Resurfacing System, already in use in Europe, was undergoing clinical trials in the U.S. when it was pulled from the market.
Dr. Walsh concluded “it is incumbent upon the hip resurfacing community to prove the efficacy and safety” of hip resurfacing procedures through proper clinical trials and not by subjecting patients to the potentially devastating effects that untested devices pose.