Zimmer Knee Replacement Procedure Provides "Custom Fit" Option
Zimmer Knee Replacement Procedure Provides "Custom Fit" Option

Dr. Harold E. Cates, Tennessee Orthopaedic Clinics
Innovations in the design and fitting of replacement knees have allowed area orthopedic surgeons the ability to "custom fit" knee replacement apparatus to each patient. Zimmer® knee replacement surgery, a new technique which takes gender differences into account, is delivering great results as orthopedic surgeons continue to hone their art.

Dr. Harold E. Cates is a pioneer of the Zimmer method at the Tennessee Orthopaedic Clinics located in and around Knoxville. Cates, one of the few select U.S. surgeons to use the newly FDA-approved Gender Solutions™ replacement knees, reports that the new technology yields excellent results in terms of fit, comfort, and overall use.

"We've been doing the Zimmer knee replacement for about two months," says the enthusiastic Dr. Cates. "It's an upgrade from a previous procedure. Total knee replacement has been a successful operation for the last 30 years; it just keeps getting better. It brings a phenomenal change in people's lives. These procedures can actually help people live longer, and it really improves the total quality of life."

Dr. Cates explains how knee replacement surgery has continued to evolve in the last 40 years. "When the procedure started there were just two or three knee sizes, it didn't even come in a right or a left. We just had three sizes to choose from so it might be too small or too large. The results were good but not fabulous.

"The Zimmer knee replacement is basically an upgrade based on anatomy," Dr. Cates continues. "For whatever size, it fits the particular patient's need better than before. With a better design and a better fit, you have a better result with motion and activity."

So why is knee surgery so important to female patients? Dr. Cates says that several elements come into play; women live longer, they are more susceptible to rheumatoid arthritis, and they are more likely to get lupus, a disease which affects the joints. Living longer ushers in a host of other diseases and complications as well, some of which indirectly affect the joints, thus requiring surgery.

Cates explains how increases in demand for knee surgery from female patients have propelled innovation in the design of replacement knees. "In the past, we pretty much designed the replacement knee for the average patient, both male and female," explains Cates. "Because of the sizes, the old knees tended to fit the males a little bit better. For women, the old replacement knees tended to hang over the kneecap, which created problems of tenderness in the tendons. Now we're seeing these subtle differences, and being aware of these differences results in better application. Female patients do better with replacement knees that are designed with them in mind."

The primary difference in male and female knees is the shape. The front of a woman's knee is thinner, resulting in kneecap tracking, which occurs from a different angle. Also, the actual knee is narrower and more conical, where a male knee is more nearly trapezoidal or square.

"The real focus of the gender knee is the design, the knee, and how it fits on a woman," says Dr. Cates. In the past, it was thought that the woman's knee was just a smaller version of the male knee. And it's not. If you look at the data you can see that women's knees are different. A lady's knee actually has an entirely different shape.

Replacement knees are made of a cobalt chrome alloy with ultra high molecular weight polyethylene. There are special finishes on the knees to minimize wear. In the surgical process, replacement knees are cemented in place. Knee replacement patients usually recuperate in the hospital for a couple of days, which is followed by a four to six week regimen of outpatient physical therapy.

Dr. Cates explains that the key to the success of the Gender Solutions knees is the availability of a wider palate of sizes, widths, and variations. "There are seven or eight sizes for the thigh bone and seven or eight for the tibia. We've gotten more incremental choices. And now we have doubled the sizes on the femur because we have right and left, and an average male and female size. So that gives us 14 size options for the femur. Just a year ago, we only had eight. Common sense tells you that the more options you have, the better the fit and the better the result.

"With the new knees, the design is much better in terms of how it wears. And with the gender improvements, there are even more variations. With the new knee designs, we have better motion, better step, and better patient satisfaction."