The artificial hip fiasco

http://en.wikipedia.org/wiki/Hip_replacement
image via wikipedia.org

Designing medical devices is hard work. Designing artificial joints is even harder. The ongoing artificial hip fiasco in the medical device industry is proof.

Artificial joints such as hips and knees are incredible technologies. They can take people out of wheelchairs and turn them into active adults. The crippling pain and infirmity of arthritis and other degenerative diseases are banished, at least for a while.

The requirements for these high tech medical devices are challenging. They are implants, subjected to full immersion in bodily fluids and subject to all of the stresses and biochemical processes of the human body. Ideally, the implant should last the rest of the patient’s life although that seems to be one of the most challenging requirements.

Implants¬†such as artificial joints¬†that must move may be the most difficult of all to design and to last in the body. Materials selection is particularly challenging. Metal implants must be sufficiently hard and tough to take the loading and repetitive motion of a patient’s joint for years and years. Ceramic implants must be fracture-resistant to impact loads and shocks, say from a jump or a fall. Polymer implants must be low friction but must not break up under mechanical stress or chemical attack. And coatings must not migrate to other parts of the body. Of course, none of the materials in the implants can be toxic.

Unfortunately, there does not appear to be an ideal combination of materials for hip implants. Interestingly as well (and I’m sure of substantial frustration to device engineers), there does not appear to be a reliable in vitro or in vivo model with which to perform wear and life testing. If there were a robust model, none of these implants would have made it to market without major revisions in materials and/or design.

Implant designs have failed mechanically through fracture and friction and more insidiously, have raised the potential for cancer and autoimmune disorders through migration of metals, coatings, and polymers to other areas of the body. In many cases, patients have undergone additional implant surgeries as a result of the failures. And these are not trivial operations.

A report today in Fierce Medical Devices indicated that Johnson & Johnson has settled 7,500 lawsuits for its metal-on-metal hip implants for a whopping $4 billion. That’s an average of $300,000 per implant and is in addition to other lawsuits settled in October. Other lawsuits against J&J are still pending as well as legal exposure outside the U.S. J&J announced recently that it will exit the metal-on-metal and ceramic-on-metal implant markets in 2014. I’m guessing that the legal settlements wiped out any profits made over the years and is probably going to cost untold numbers of jobs.

J&J’s competitors have problems too. According the the Fierce Medical article, Biomet, Stryker, and others are facing similar liability situations with respect to metal-on-metal implants.

The market for these devices is large and increasing. Hip implants are one of the most frequent orthopedic surgeries. As the population of seniors in the U.S. and other developed countries continues to grow while the baby boom generation ages, demand for procedures that maintain active lifestyles will continue to increase.

Takeaways: The onus is on medical device engineers to create valid in vitro and in vivo preclinical models and to test exhaustively before releasing to manufacturing. Engineers and researchers must also identify biomaterials and designs that are truly biocompatible and able to meet the demanding requirements that these implants must satisfy.

Give the track record of implants, engineers and medical device executives can expect increased scrutiny and skepticism from regulatory agencies, investors, physicians, and patients and their families.

Of course, it also means that there is an incredible opportunity awaiting the company or engineer that can solve this intractable issue.

Read more:

Report: J&J settles most metal hip lawsuits in $4B-plus accord – FierceMedicalDevices.

More Artificial Hip Concerns – NYTimes.com.