Hip, knee replacement surgery rates skyrocket over 7 years

Implanting artificial joints, once the stuff of science fiction, has become so common -- and is expected to become even more so -- that it may overwhelm the health care system, according to a paper in the April 15 Arthritis Care & Research.

"The demand is exploding," said Sunny Kim, PhD, the paper's author and assistant professor of biostatistics at Florida International University in Miami. "Are we ready as a nation? I don't think so."

Analyzing data from the Nationwide Inpatient Sample, Dr. Kim found that primary hip replacements increased by 48%, from 153,080 procedures in 1997 to 225,900 in 2004. First-time knee replacements grew by 63% from 264,331 in 1997 to 431,485 in 2004. If these trends continue, an estimated 600,000 hip replacements and 1.4 million knee replacements will be carried out in 2015.

The fact that the number of these procedures is increasing and most likely will continue to grow is supported by other studies. For instance, one in the April 2007 Journal of Bone & Joint Surgery predicted that demand for primary hip replacement would grow 174% by 2030 and for an initial knee replacement by 673%.

Several theories are offered for this phenomenon. One is that the population is aging, although Dr. Kim's paper suggested that the rate of increase far outpaced the change in this demographic factor. Another, though, is that the population is heavier, and many experts consider this explanation to be the best reason why so many joints are wearing out.

"A lot of ideas get thrown around, but I would say that probably the No. 1 factor is obesity," said Trish Palmer, MD, a family physician and assistant professor of primary care sports medicine with Midwest Orthopedics at Rush in Chicago.

The rate of obesity and overweight has grown significantly and is recognized by many public health agencies and medical societies, including the American Medical Association, as a major public health problem.

But while obesity is considered to be a central problem, many experts point to other issues as also playing a role. Improvements in technology, both in joint construction as well as computer-assisted surgery to improve the precision of how it is aligned, lead physicians to be more at ease with making this recommendation.

On the patient side, controversies over the safety of pain relief medications such as the Cox-2 inhibitors are leading some to prefer non-pharmacologic options for long-term pain relief. "People don't want to take medications," said Paul Lachiewicz, MD, professor of orthopedics at the University of North Carolina at Chapel Hill. "They want it fixed."

Also, manufacturers of artificial joints have been promoting these devices in direct-to-consumer advertising, and patients are more aware of them than ever.

These dynamics may be driving down the age at which this operation is performed, as reflected in the increased number of people ages 45 to 64 who have knees or hips replaced. According to Dr. Kim's paper, in 1997 this age group comprised 27% of all first-time hip replacements and 26% of initial knee replacements. Both of these numbers increased to 36% in 2004.

"Orthopedic surgeons performing these procedures are much more likely to recommend the procedure be performed at an earlier stage, because we're more confident that the product will last longer and allow patients to enjoy a more active, pain-free, productive future," said Stephen Hurst, MD, an orthopedic surgeon in San Mateo, Calif.

Cost, access become issues

Still, even though experts say this technology has proven to be cost-effective for most patients, it is not without financial bite. That reality is the point from where most of the concern about the increase results. According to Dr. Kim's paper, joint replacements cost hospitals $9.1 billion in 2004, about half of that paid for by Medicare.

"People are not arguing that it's not a worthwhile intervention, but we are anxious about who's going to pay for it," said William Maloney, MD, chair of orthopedic surgery at Stanford University in California. "Hip and knee replacement could break the bank."

Other concerns stem from what could become an access issue -- will there be an adequate supply of surgeons to meet the demand?

"The number of orthopedic surgeons is not increasing at the rate that the need for joints is increasing," Dr. Hurst said. "It's going to be difficult to keep up. Most orthopedic surgeons are reasonably busy, and many are busier than they want to be."

Also, the growing number of people getting this procedure done at younger ages increases the likelihood that they may outlive their artificial joint and will need to have it replaced with another one. Those surgeries are costlier and riskier, and the rate of these types of procedures has started to inch upward as well.

"There's no doubt that for all the same reasons, revisions are going to increase, and revision is a much more expensive and much more difficult [procedure] for the patient and for the doctor," said Anthony DiGioia, MD, director of the bone and joint health program at Magee-Womens Hospital at the University of Pittsburgh Medical Center. "It raises the stakes."

To cut the risk of revision and other complications, the American Academy of Orthopaedic Surgeons is working to establish a registry to identify implants that last longer and strategies that can lengthen their life even further. A request for information from vendors who may become a part of the project was issued in March. Numerous other countries, including Canada, Sweden and Great Britain, already have such registries.