Today's News

Friday, February 25, 2005

Panel discusses balancing TKR patient needs and techniques

As the demographics and demands of today's total knee replacement (TKR) patients change, orthopaedic surgeons are transforming the procedures and technology they use to ensure patient safety and improved outcomes. At a media briefing Thursday, a panel of experts discussed how to balance knee replacement patients' changing needs with state-of-the-art techniques available in surgery today.

The average knee replacement patient today is no longer a 60 - to 70-year-old sedentary individual, but a much younger, active adult in their 50s. These younger patients come to surgeons' offices with dramatically higher expectations than previous generations did -particularly regarding the function of the new knee.

"Because of direct-to-patient marketing by the orthopaedic industry, patients are coming in with information from the Internet or some advertisement and are asking for specific techniques or implants," said William J. Maloney, MD, professor and chairman of the department of orthopaedic surgery at Stanford University School of Medicine, Stanford, Calif. "This raises some controversial issues, especially when patients request specific surgical techniques, such as minimally invasive surgery, and rehabilitation methods." Only a surgeon should recommend which procedure is best, based on his or her experience and each patient's individual circumstances.

Minimally invasive surgery (MIS) for total knee replacements refers to performing the operation with a smaller incision. More importantly, it means not traumatizing the muscles around the knee. This less invasive procedure is performed by only a small percentage of orthopaedic surgeons, however. If surgeons succumb to patient demand and perform the MIS procedure without proper training, it can cause serious patient complications.

Michael A. Mont, MD, director of the Center for Joint Preservation and Reconstruction, Sinai Hospital, Baltimore, discussed a new minimally invasive lateral approach to the knee that does not require any splitting of the muscles. Its best outcomes allowed patients to run two weeks later and exhibit normal walking patterns, but despite this early success, he offered strong words of caution.

"Although we have seen some of the best results in the world with this technique as well as with other minimally invasive techniques, we have also encountered problems," Dr. Mont explained. "Patients need to realize that these techniques are still in development and require further analysis to assess their true role. These newer procedures are not for everyone."

Orthopaedic surgeon Douglas A. Dennis, MD, medical director, Rocky Mountain Musculoskeletal Research Laboratory, Denver, is particularly alarmed by some catastrophic complications he has observed from minimally invasive procedures he did not perform. These include a lacerated popliteal artery, cut ligaments leading to knee dislocation, and even skin necrosis from excessive pulling on sensitive skin around the knee so the surgeon can see with limited exposure. More commonly, a knee joint may be malaligned, because it is inherently more difficult to align a knee with less exposure.

To study whether or not performing MIS on the knee puts patients at any greater risk, a team of orthopaedic surgeons including Peter M. Bonutti, MD, Bonutti Clinic, St. Anthony's Memorial Hospital, Effingham, Ill., initiated a prospective randomized multi-center study of 80 patients with six surgeons at a half dozen medical centers. The study included 40 patients with a standard total knee replacement and 40 patients with a MIS total knee replacement. At 12-week follow-up, the team found that there were no differences in the two groups based on traditional measurement criteria for the knee.

"This is an important study because our first responsibility is to prove the safety and efficacy of an MIS approach," said Dr. Bonutti. "We can now focus on studies that measure patient satisfaction improvements as we continue to evolve the technique."

Another issue is materials, because traditional implants used over the past three decades have limitations. Dr. Maloney explained that while the traditional implants have been great, they are not going to withstand the high impact forces to which today's active patients may subject them. New materials that wear better may be needed, such as a highly cross-linked polyethelene insert in the bearing part of the knee implant.

While traditional polyethelene wears over time and may lead to implant failure, especially in highly active patients, this newer, extra dense material with additional bonds at the molecular level has the capacity to wear for a longer time. The tradeoff is that it comes with an increased risk of implant breakage-hence the concern and the controversy.

"We are probably going to need further generations of these materials to actually accomplish the goal of providing some of our younger patients with the wide range of flexibility, movement and durability they expect from their new knees," said Dr. Maloney.

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