Mend and Bend

Partial knee replacement with a robot can lead to better results

If it ain’t broke, don’t fix it.’ That’s part of the idea behind a new robot-assisted technique for knee replacement that makes it easier to replace only the bad part or parts of a patient’s knee.

The technique, MAKOplasty® partial knee resurfacing, uses a robot and offers a more precise operation than performing the same procedure without the robot arm, doctors say. The new technique also opens the operating room door for more patients to get partial knee replacements instead of total knee replacements.

If a patient has a partial knee replacement and the rest of his or her knee has problems, a surgeon can then do a total knee replacement later.

More than 600,000 total knee replacements are performed each year in the United States, according to the Agency for Healthcare Research and Quality. As Baby Boomers age, the demand for total knee replacements could reach 3.5 million a year by 2030, according to a study reported in the Journal of the American Medical Association.

Patients who suffer severe arthritis in one or two of the knee’s three components are candidates for partial knee replacements, says Dr. Boyd W. Haynes III of the Orthopaedic and Spine Center in Newport News.

With a partial knee replacement, patients recover and progress through rehab faster. They also have more natural movement afterward because a partial knee replacement preserves more of the body’s natural ligaments, especially the ACL, Haynes says.

“When you do a total knee replacement, you take out and replace the ligament structure in the knee,” Haynes says. “Total knee replacements try to mimic natural movement, and they do a good job but the knee never moves exactly the way it did before. The biggest advantage of doing a partial robotic knee replacement is converting someone who would have been a full knee replacement to a partial knee replacement with a better functioning, more natural knee.”

Earlier this spring, Haynes used the robot arm to replace the kneecap of a lady who had trouble getting out of her chair. One week later, she had the full range of motion in her knee, he says. “Before the robot, I would have had to take out the good parts of her knee as well as the bad parts,” he says.

But partial knee replacement surgeries can be more difficult because precise positioning is required to line up the new knee components with components of the body’s natural knee, says Dr. Anthony Carter of Hampton Roads Orthopaedics and Sports Medicine in Newport News.


If the components of a partial knee are badly positioned, the new knee “will fail miserably,” Carter says. Surgeons who aren’t experienced in partial knee replacements may opt to do a full knee replacement even in a patient with arthritis in only one or two components of the knee—to eliminate the risk of failure, Carter says.

The MAKOplasty procedure offers the needed precision whether or not a surgeon is experienced performing partial knee replacements, Carter notes.

“I did partial knee replacements before using the robot,” says Carter, who says he was skeptical at first about the robot. “But with the robot, the precision is unbelievable.”

With MAKOplasty, the surgeon first gets a CT scan of the patient’s knee and then a 3D computer model, Carter says. During the operation, the surgeon manipulates a robotic arm that uses a burr similar to a dentist drill to sculpt the knee, Carter says.

“Instead of cutting the bone with a saw blade, you’re actually sculpting it with a burr,” he says. “You’re not cutting any of the ligaments or tendons. So the knee feels more natural.”

During the operation, the robot maps the knee again and overlays that design with the 3D model, Carter says. As the operation continues, if the surgeon starts to stray more than half a millimeter from the plan, the robot stops, he says.

“I’m still doing the operation,” he says.

“I’m moving the burr with my hand. But once you make the plan, if you start to go outside the line, the robot won’t let you.” Before the surgery is complete, the robot takes multiple points and tests for balance to ensure the new knee components are balanced across an entire range of motion, Carter says.

Once the operation is complete, patients getting total knee replacements will spend one to three days in the hospital, compared to going home the same or next day with a partial knee replacement, Haynes says.

Patients with total knee replacements have to work hard during rehab, Haynes says. Some even drop out of physical therapy and then their knee stiffens up, he says.

“I don’t see that in partial knee replacements,” he says. “They have less bleeding, less swelling, less pain and recover motion easier. If you can make it easier for the patient to rehab, the patient will be more successful.”

Patients with a MAKOplasty partial knee replacement don’t have to work as hard in physical therapy, get a better range of motion and a more natural knee, Haynes says.

“It’s a very nice option, he says.

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