with putting in implants every single time, outcomes should be influ-
enced in a positive way," says Dr. Suk. "That's a logical step."
• Ligament balancing. The ligaments in a replaced knee need to
provide equivalent balance with the knee at full extension and at 90
degrees of flection. "The problem," points out Dr. Fillingham, "is that
no one knows what the perfect balance is."
Dissatisfied knee replacement patients often complain that their
joints feel "too loose" or "too tight," says Dr. Fillingham, adding that
most surgeons err on the side of making knees tight to prevent the
joint from feeling unstable. He believes robotics will improve out-
comes by quantifying the perfect ligament balance.
"Instead of telling surgeons what ligament balancing should be, the
technology currently tells surgeons what it is," says Dr. Fillingham.
"Over time, that information will serve as a data point. When the tech-
nology is more widely adopted, we'll have the potential to determine
the ideal ligament balance based on specific patient factors. Robotic
assistance already helps us achieve more consistent outcomes, and
could eventually identify exactly how surgeons should balance
knees."
The knee is not a dumb hinge — there are plenty of subtle move-
ments surgeons have not been able to recreate with a total knee
replacement. "Partial knee replacements result in less impact to those
subtle movements," says Dr. Fillingham. "A partially replaced knee
will feel more like a native knee because the ligaments are kept intact,
and the natural anatomy remains largely unchanged."
But many surgeons don't attempt the procedure because it's so tech-
nically difficult to perform. Close to 30% of patients who undergo total
knee replacements are candidates for partial knees, according to Dr.
Fillingham, meaning many patients are missing out on a clinically ben-
eficial technique.
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