Growing Demand for Joint Replacements

Advancements in hip replacement surgery and recovery have more baby boomers turning to joint replacement earlier in life to stay active and better their quality of life. Per Andrew Urquhart, MD, chief, Joint Reconstruction Service in the Department of Orthopaedic Surgery at the University of Michigan Health System, “Hip joint replacement was once reserved for the elderly, so younger adults with hips damaged by arthritis or a past injury were told to wait to undergo hip replacement surgery and recovery until they were very old. However, baby boomers of today have higher expectations and don’t want to let a damaged joint slow them down. They want to get back on the ski slopes, back on the jogging track—and back to an active life.

Joint replacement surgery and recovery has helped thousands of people return to living productive and enjoyable lives. With hundreds of thousands done annually in the U.S., joint replacement represents one of the largest uses of high technology and engineering in medicine today. And it’s likely to become even more common in the next two decades as 65 years and older constitute the fastest growing age bracket in the U.S. In fact, hip replacement is expected to increase 174% in the next 20 years, and knee replacements will rise even more--673%, according to a study presented at the American Academy of Orthopaedic Surgeons' 2006 annual meeting.

What's behind the growing demand for new joint replacements?

Blame it on the lifestyle of the baby boom generation, says Mathias Bostrom, MD, an orthopedic surgeon at New York's Hospital for Special Surgery, where total knee replacements were pioneered.

"They're not willing to be sedentary or change their lifestyle," Bostrom tells WebMD. "Their joints are beat up and they're living longer, and they want joints that let them do the things they're used to doing." This also means that younger people, in their 50s and even 40s, are demanding joint replacement, which is increasing the market for the surgery in both the U.S. and in Europe.

When joint replacement surgery and recovery occurs, the artificial surfaces of the joint replacement are shaped to allow joint movement similar to that of a healthy natural joint. A person who has injured or damaged their joint may experience extremely severe pain at the site of the joint. Some avoid using the joint, weakening the muscles around the joint and making it even more difficult to move the joint—which increases the need for a joint replacement.

Ivory was First Joint Replacement Material Used

The first serious attempt at hip joint replacement occurred in 1890 when a physician, Dr. Gluck, replaced the head of a patient's femur with an ivory ball. He attached it to the patient's femur with screws and a form of bone glue he had concocted himself. Medical practices at the time, however, made all forms of surgery inherently dangerous. Risk of death due to infection and blood poisoning far outweighed any benefits afforded patients by this type of experimental surgical procedure.

The next materials tried—Bakelite, Pyrex, and Lucite—had only marginally better results. Upon removal, they all showed excessive wear, fragmentation, or adverse tissue reactions. Making the cups out of vitallium, a cobalt-chrome alloy, yielded improved results. However, even these were successful in only about half the cases.

Postwar Joint Replacement Breakthrough

In 1950, Austin Moore made one of the most important advances in hip joint replacement. He correctly reasoned that an artificial femoral head with a slightly curved stem could be anchored in the intramedulary section, or marrow, of the femur to give more mechanical support to the head. Modifications to his original design are still in use today.

After the initial success of the Austin Moore design, many similar joint replacement models were tried. During the 1950s and 1960s, joint replacement was made out of stainless steel. But steel does not have sufficient strength and many broke after implantation. As a result, engineers worked on better methods of casting and forging sturdier cobalt-chrome alloys. Today, cobalt-chrome alloys are the most popular metal alloys used to make hip joint replacements.

Titanium alloys have also been used in hip joint replacement. Some engineers believe titanium is superior to cobalt-chromium alloys because its stiffness, or modulus of elasticity, is closer to that of bone. Titanium is also prescribed for patients hypersensitive to chromium.

Another advance, made in the late 1950s, was the first use of polymethyl methacrylate (PMMA) as a fixating agent in hip joint replacement. PMMA was approved for general use in 1971 and has since become the most popular method for attaching joint replacement components.

In 1961, high-density polyethylene was tried. It allowed proper lubrication in acetabular joint replacement and was biocompatible. Friction was minimized by decreasing the size of the femoral head. As a result, polyethylene remains the material of choice in modern hip replacements.

Recent Joint Replacement Developments

Modularity and sizing of artificial hip components are hallmarks of the 1980s. Proper sizing ensures the best fixation regardless of whether surgeons use cemented or press-fit methods for joint replacement. Sizing is also critical in maintaining proper joint replacement geometry, or anatomic positioning, of the joint. Without proper geometry, the patient might not regain the full use of the hip once it has healed.

The components that make up a total hip replacement implant usually consist of stems, necks, femoral heads, acetabular cups, and distal tips.

How to get Joint Replacement Products to Market

The product cycle for a hip joint replacement is not very different from that of other engineered products. Once a company's researchers determine they have a new feature or material that will give its product an advantage in the marketplace, a prototype is built and tested. If the joint replacement device is an implant, it is fatigue tested for 10 million cycles at 4-5 times the expected load.

Testing must also meet American Society for Testing and Materials (ASTM) standards for total joint replacement design. In tandem, the company must also win the approval of the Federal Drug Administration (FDA), which regulates the manufacture of joint replacement products. It protects the public safety by making sure new designs have been tested to Federal standards and live up to manufacturer promises. There are different approval processes depending on the classification of the innovation.

If you think you have had joint replacement using DePuy’s ASR acetabular cups, contact Seeger Weiss today. Our experienced defective hip replacement attorneys can immediately assist you and discuss your legal options.