Smart Enough to Know What We Don’t

How many people do you know who have benefitted from a medical device? More than you realize, I’d bet. From instruments to implants, medical devices are saving and improving people’s lives every minute of every day, and that’s not hyperbole. Most often, the positive impact of this technology is out of our control. We, aspatients, take a lot on faith. If our doctor says a device—an implant or device-enabled procedure—is safe and effective, ultimately there’s a narrow window through which we can affect outcomes. We have to follow our physician’s orders for recovery or for adapting to life with an implant if we are to give ourselves the best chance for a successful outcome. The rest, for the most part, is out of our control.

Consider large-joint replacement surgery. Many of us know someone with a new knee or hip. Maybe you’re the one who hasreturned to previous levels of activity thanks to an artificial joint. It’s mainstream. It’s a success story of modern medicine. Many aging sports stars and public figures are very open about their new hips and knees.

John Kerry, the senior U.S. senator from Massachusetts, is a huge hockey fan and doesn’t miss an opportunity to hit the ice. At 68, you’d think the one-time Democratic presidential nominee might consider giving up the game to pursue less-intense pastimes. But not quite. He recently led a team of lawmakers against a group of lobbyists in a matchup for charity. His team, including some much younger guys, skated to victory. “I’m not ready to hang it up,” he told The Washington Post. “I love it. It’s a great game, and I’m able to still skate. I’ve got two artificial hips, and I’m still out there.”

Recently, however, researchers are starting to ask if enough is known about patient outcomes or the effectiveness of various implants. And, according to a study recently published March 6 in The Lancet medical journal, consensus is lacking about the precise indications for knee replacements.

The authors, based in the United Kingdom, Sweden and Australia, claim that surgeons need improved decision making as anincreasing number of candidates for new knees are younger than 55 years, which is a group with a higher rate of revision or follow-up surgery. The study also noted that some patients undergo revision despite having good functional ability and only mild pain. Thearticle, based on data going back to 1970, is the second in less than a week raising doubts about joint implant safety and effectiveness. On Feb. 28, the British Medical Journal charged that hundreds of thousands of patients with metal-on-metal hip replacements were at risk of exposure to toxic, Cancer-causing substances.

According to the Lancetstudy, the number of total kneereplacements in the United States increased from 31.2 per 100,000 person-years from 1971 to 1976 to 220.9 per 100,000 person-years in 2008, for a total that year of more than 650,000 procedures. Theauthors predict that the demand for knee replacement will continue to grow in developed countries in light of aging populations andrising obesity rates, which both lead to higher rates of osteoarthritis, the main clinical indication for joint replacement.

“No clear consensus exists within the surgical community about exact indications, particularly severity of preoperative symptoms, obesity and age,” the study’s authors wrote. The key outcome studied was the rate of revision surgery to deal with complications. Aseptic loosening, usually caused by implant wear, is the most common reason for revision surgery, and mostly is a concern for younger, active patients. The second most common reason is infection. Other major causes are post-operative pain, instability and stiffness.

An implant’s design makes a significant difference in minimizing or maximizing the risk for adverse events that require revision surgery, the authors said, emphasizing the importance of monitoring implants through national registries. However, revision surgery also can be blamed on a host of other factors, including surgical skill, patient factors, operating room conditions and post-operative care.

Study data compared total knee replacements to partial-knee procedures. Surgeons and patients sometimes choose a partial implant for a more “normal-feeling” knee, less-extensive surgery and a lower risk for infection. Partial replacement, however, has a higher risk for revision surgery than total replacement, and a conversion to a total knee is likely to require more follow-up than doing a total knee in the first place, according to the study.

The continued development of national registries to monitor long-term outcomes is essential, the authors said, as well as using electronic health records to aid in the process. The authors also urge new strategies to treat early stage osteoarthritis in younger patients to avoid the need for major surgery. But there is a silver lining.

“Joint-replacement surgery is one of the most successful examples of innovative surgery and has resulted in substantial quality-of-life gains,” the authors wrote.

Clearly, this kind of research indicates a procedural shift—which already has begun in part—for which companies and care givers put systems in place to actively and continually gather as much data as possible over the long-term, post-clearance. This kind of information will have a significant impact on the design and manufacture of next-generation medical technology.

Christopher Delporte

Editorial Director, Medical Devices