Science

New Knees Offer New Life

Gone are the days when getting older meant slowing down and losing your desire to stay active. In the minds of baby boomers, the last of whom are now reaching their early fifties, there’s still so much more to life that shouldn’t be hindered by an aging body.

Aging and Overweight Population

And as the overall population of the U.S. continues to age through 2050, the prevalence of osteoarthritis will continue to increase. Combine that with the increasing prevalence of overweight and obese Americans among all age groups, and it’s no surprise why orthopedic surgeons like Carlos Alvarado, M.D., from Miami Orthopedics & Sports Medicine Institute, are being kept busy operating on damaged knees.

“The knee sees an incredible amount of stress daily,” Dr. Alvarado said. “Between 2.5 and 7 times our body weight is absorbed through the knee joint with each step. That means even small changes in body weight can have a drastic effect on knee function.”

In fact, a recent study published in the Journal of Bone and Joint Surgery suggested that the overweight and obesity epidemic was driving the need for total knee replacements at a rate that outpaced the need for hip replacements. Alexander van der Ven, M.D., also an orthopedic surgeon from Miami Orthopedics & Sports Medicine Institute, agrees with the study’s findings. He has seen the uptick in the need for knee replacement surgeries in people with a Body Mass Index, or BMI, of 25 or greater. But he also attributes the higher volume of knee replacement surgery to better technology and a better understanding by surgeons of how knee replacements benefit younger patients.

“Younger patients have greater satisfaction with knee replacements than do older patients, because they have so much more of their active years to lose at a younger age,” he said. “Where we previously operated on people in their 80s and 90s, we’ve learned that intervening earlier – when patients are in their 50s and 60s – nets better outcomes and improves their overall quality of life into their 80s and 90s.”

Custom Knee Replacements

In 2010, just as orthopedic surgeons were beginning to use traditional knee replacement surgeries – which had been around for 30 years – on younger patients, new three-dimensional printing technology made creating custom knee implants a reality.

To produce a custom knee prosthesis, a CT scan of the patient’s knee anatomy is sent to the manufacturer, where a 3D printer creates a metal implant of the knee designed with the patient’s exact measurements and shape.

Instead of using knee implants “off the shelf” and chipping away at them to make them fit into patients, surgeons receive custom knee implants from the manufacturer ready to fit into their specific patient.

“With custom knee replacement, we shape the knee to fit you, rather than shaping you to fit the prosthesis,” Dr. van der Ven said. He describes the difference as similar to having a custom suit or dress made for you, versus having one tailored to fit you. “If we can make the knee fit better, it’ll function better and feel more like your natural knee.” Plus, Dr. van der Ven says the better fit leads to a quicker surgery, less bleeding and fewer adjustments to surrounding muscles and tendons, leading to a faster recovery.

Dr. van der Ven says that recovering from custom knee replacement surgery still requires intense physical therapy for about six weeks, and patients must be active partners in their rehabilitation following surgery. But, he says once patients recover, they report their knees feel like new.

Age as a Factor in Recovery

He dispels common myths that custom knees will wear out after 10 to 15 years, so patients shouldn’t get them in their 50s or 60s. “That’s not based on hard evidence,” he said. “Unlike with a tire that wears out after 20,000 miles, there’s really no reason that 90 percent of these knee implants shouldn’t last up to 30 years.”

That’s why Dr. van der Ven recommends speaking to an orthopedic surgeon about knee surgery sooner than later. “If you have knee pain and put off medical attention until the damage is too bad, your recovery will be less than optimal,” he said.

Dr. Alvarado, who, like Dr. van der Ven, also performs traditional and custom knee replacement surgery, says that instead of age, a patient’s overall health is a better measure of whether they are a candidate for knee replacement.

Both doctors agree the most successful knee replacement surgeries happen when patients are eager to regain their lifestyle and are willing to work hard during recovery and rehabilitation – no matter what their age.

“Attitude is key,” Dr. Alvarado said. “If patients approach post-operative physical therapy with a positive attitude and vigor, it is really amazing to watch them improve.”

Healthcare that Cares

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