Metal-on-Metal Hips: Material Solution at a Crossroads

Joshua J. Jacobs, M.D., cannot fully explain his aversion to metal-on-metal hip implants. More than a dozen ago, well before problems with these devices began to surface, Jacobs favored artificial joints made of metal and highly crosslinked polyethylene.

“At the time, the highly crosslinked polyethylene is where I thought the industry was going. It’s where my instincts led me,” Jacobs said during an expert roundtable discussion with journalists during the first full day of the 2012 American Academy of Orthopaedic Surgeons Annual Meeting in San Francisco, Calif. “I had no idea back then that I would someday be sitting in a room talking about what was going on with these implants. I had no idea that would happen.”

Neither did the creators of metal-on-metal hip replacements, which have become the proverbial black sheep of implant choices as controversy grows over their potential health hazards. The failure rates of metal-on-metal hips and concerns about the gradual buildup of wear particles in the body have prompted many patients to rethink their decision to undergo joint replacement surgery with all-metal implants. Such hesitancy has led to a sharp decline in the number of metal-on-metal joints used in replacement surgeries; before they fell out of favor, all-metal implants accounted for nearly one-third of the estimated 250,000 hip replacements performed annually in the United States. About half a million patients have received metal-on-metal replacement hips, according to one estimate, though more precise figures are difficult to ascertain due to the lack of a national implant tracking system.

Though he prefers implants made from metal and highly crosslinked polyethylene, Jacobs was fair in his assessment of all-metal hip replacements, noting that most patients with the devices are satisfied with their choice. He also warned against classifying all metal-on-metal hip implants as “one group,” telling reporters that the joint replacements vary by size, design and specific features.

“It’s very perilous to talk about metal-on-metal implants as one group,” Jacobs told a dozen journalists at his roundtable discussion. “It’s a very heterogeneous group. If you bunch them all together, you miss the nuances…metal-on-metal [hip implants] can have large heads, they can have small heads, they can be designed for a hip resurfacing or they can be designed as a total replacement. And every design from orthopedic device companies has its own unique features, which can impact the way the product performs.”

“In general, there are some devices that have performed very poorly and have been removed from the market. Others have done very well. Even with the worst designs, the majority of patients still have good results from their surgeries,” said Jacobs, incoming first vice president of the American Academy of Orthopaedic Surgeons and an adult reconstructive surgeon at Rush University Medical Center in Chicago, Ill. “The majority of patients with these [metal] implants are doing quite well, but the failure rates are very disappointing and as orthopedic surgeons we are not happy about those rates. When there is a failure from an implant, we feel it, the patient feels it and the system feels it.”
The system is about to feel it in a big way, too. All-metal hips have been failing at surprisingly high rates in recent years, giving out within one or two years of the original procedure. Hip implants are designed to last 15 to 20 years but the wear of metal parts sometimes can generate debris that damages soft tissue and bone, crippling patients and forcing them to replace (or in certain cases, revise) the implants.

Implant durability can vary depending on the materials used. For example, highly crosslinked polyethylene is used less frequently for joint replacements but has been shown in a laboratory setting to decrease wear by about 94 percent, including a substantial reduction in pitting and delamination. Ceramic-on-ceramic hip replacements produce fewer wear particles, but can produce an irritating squeaky noise during use. A fairly recent study (released last year) concluded that artificial hips and knees developed within the last five years are not significantly better than older devices; 30 percent, in fact, were considered worse than their earlier counterparts.

It is one of the older models that has become a source of controversy for the industry, though. Eighteen months ago, Johnson & Johnson’s DePuy Orthopaedics unit recalled its ASR XL Acetabular System, a hip socket used in traditional replacement surgery, and the ASR Hip Resurfacing System, a partial hip replacement that involves placing a metal cap on the ball of the femur in order to preserve more bone. The company reportedly recalled both products due to the number of patients who needed a second hip replacement.

Many of those patients are now suing DePuy (some industry observers have estimated that as many as 3,500 patients have filed suit against the company). The lawsuits, in turn, have ignited a financial scramble as patients attempt to recover lost wages and pay off astronomical medical bills, insurers try to regain their expenses from settlements and Medicare fights for its fair share. Medical and legal experts estimate the hip failures may cost taxpayers, insurers, companies such as DePuy and others billions of dollars in coming years, contributing to the skyrocketing cost of healthcare. The financial fallout is expected to be unusually large and complex because the controversy over metal-on-metal hips involves a class of products rather than a single device or just one company.

DePuy would not comment on how much it had paid in recall-related costs. But spokeswoman Mindy Tinsley told The New York Times that the company is working with patients and insurers.

Along with ASR-related cases, DePuy also faces more than 560 lawsuits over the all-metal version of another hip model—called the Pinnacle. Since the model is performing well, company executives have said that costs for its replacement are being borne by Medicare, insurers or patients themselves.

To recoup their expenses, insurers typically notify patients through lawyers that they expect to be reimbursed from any settlement money patients receive, rather than pursue their own lawsuits with the device makers. Also, Medicare is expected to enforce new laws sometime this year that will make it easier for the agency to recover taxpayer dollars spent treating patients injured by problem drugs and medical devices, legal experts said.