Hip Checked

Author: 
Shana Leonard

It appears as though metal-on-metal (MoM) hip implants have officially worn out their welcome. On the heels of a deluge of negative publicity stemming from the DePuy ASR system recall last year and mounting evidence of the production of hazardous metallic-wear particles, all-metal hip implants are currently being tried in the court of public opinion. And they may just be going away for life.

Although they do boast some clinical advantages, metal-on-metal hip implants have come under fire in recent years as adverse reactions continue to come to light. While most bearing-material combinations generate minor wear debris, MoM implants have received flack for increased particulate production and the potential danger associated with metal ions found in the blood stream. Furthermore, metal wear particles have been found to damage the tissue and bone surrounding the implant. As a result, patients with MoM implants may experience pain or implant loosening, and, ultimately, may require revision surgery. In fact, MoM implants are twice as likely as metal-on-polyethylene designs to require early revision surgery, according to Australia’s orthopedic registry.

The emergence—and proliferation—of such data has cast a shadow on MoM implants that has grown substantially darker with the 2010 DePuy ASR system recall, which resulted in lawsuits, a mainstream media blitz, and a lot of headaches for DePuy. But perhaps the final nail in the coffin of MoM implants comes from FDA. In May, the agency issued 145 orders to 21 manufacturers of MoM implants for postmarket surveillance studies in what has been deemed an uncharacteristic move. It claims that this information will contribute to a better understanding of MoM implants and their safety profiles.

With FDA scrutinizing MoM implants, doctors shying away from their use, and patients rallying against them, the future is looking somewhat bleak for all-metal hip implants. So, what now? It’s likely that physicians will increasingly pass over metal-on-metal designs in favor of more-traditional bearing surface combinations, such as tried-and-true metal-on-polyethylene designs, for example. Ceramic-on-ceramic implants are also gaining traction for certain demographics, despite a well-publicized squeaky setback several years ago. Seeing potential in this area, Zimmer, for example, recently introduced the ceramic-on-ceramic Maxera implant optimized for younger and more active patients; however, this device is not yet available for commercial distribution in the United States.

Also eyeing the advantage of low-wear ceramic, DePuy is trying to regain its competitive advantage—and public trust—with the launch of the Pinnacle CoMplete acetabular hip system in June. The CoMplete is the first ceramic-on-metal hip implant approved for use in the United States.

Regardless of the next big bearing material combination, however, implant OEMs can be sure of one thing: The industry is changing. Thanks to the MoM brouhaha, future implant designs will likely have to undergo more-extensive premarket testing and evaluation. And hip implant OEMs will just have to grin and bear it.