New Generation Knee Replacements Don’t Always Deliver

Knee replacement patients are younger than ever before. To help these younger patients remain as active as possible, knee replacement manufacturers are developing devices that they promise will last longer and provide for greater range of motion than older devices. Unfortunately, according to a report in The Wall Street Journal, many innovations in knee replacement surgery don’t always deliver as advertised.

Some new, much-hyped knee devices haven’t always delivered on their promise. Take for example <"">high-flexion (hi-flex) knee implants, which promise a higher range of motion than traditional devices, and are generally used in younger, more active patients. Hi-flex knee replacement surgery requires that more bone at the back of the knee be removed so that the patient may bend the joint further farther. However, the high-flexion coveted by many patients will not be achieved in those whose mobility was very severely restricted before the surgery. Recently, one study that compared high-flex prosthetics with normal prosthetics revealed that for the average patient without any special demands, the additional knee flexion provided by the high-flex design made no significant difference in range of motion.

One such component, the <"">Zimmer NexGen CR-Flex NexGen CR-Flex Porous Femoral Component , is allegedly failing in patients much sooner than it should. Last year, we reported that data presented at an American Academy of Orthopaedic Surgeons conference indicated that 36 percent of the Zimmer NexGen CR-Flex Porous Femoral Component patients examined after two years showed signs of the replacement knee loosening. The same study, which involved 108 patients, also found that nearly 9 percent of the Zimmer NexGen CR-Flex Porous Femoral Component patients examined after two years required revision knee surgery due to loosening and pain.

“There is, to be honest, some irrational exuberance out there,” Daniel Berry, chief of orthopedic surgery at the Mayo Clinic in Rochester, Minn., and president of the American Academy of Orthopedic Surgeons, told The Wall Street Journal. “People may be overly optimistic about what joint replacement can do for them.”

Even when the most advanced knee replacement devices and minimally invasive surgical techniques are used, patients face a long period of rehabilitation after surgery and may not be able to resume high-impact activities, the Journal said.

One big concern about knee replacements is how long they will last. With younger patients receiving the implants, device makers are striving to design components that will last beyond the 10 to 15 years normally expected from traditional implants. According to the Journal, one manufacturer, Smith & Nephew, recently won clearance from the Food and Drug Administration to market its latest technology as a “30-year knee” based on tests mimicking 30 years of wear. But there is no data available to indicate how long such devices will last in actual patients.

To get that kind of longevity, knee replacement patients will have to give up high impact sports, something they might not expect. According to the Journal, walking, swimming and cycling are in, but jogging, running, jumping and singles tennis are out if a patient wants to get the longest wear out of their new knee.

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