HEALTH
& Sports Medicine for relief from their knee pain and a
replacement is recommended, the patients are referred to an
imaging center for CT scan that is then sent to ConforMIS in
Boston. After proprietary algorithms convert the scan into a
3-D model by mapping the surface of the joint, the measurements
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are sent to a laboratory. Using 3-D printing, a toolkit is
created with all the parts made specifically for a patient.
“You are bringing the patient back to what a normal,
anatomic knee should look like,” he said. “You are matching
j-curves, you are matching patient slope. None of the other
implants are doing that.”
Rossario further explained that with a stock knee, a
surgeon lops off the end of the femur in a flat cut, but the
femoral condyles are not flat, they are offset. With the stock
knee, you are cutting off more than you need to. There is no
adaptation for the j-curves of the knee. ConforMIS is the only
replacement he has found that affords the patient full arc of
motion from full extension to full flexion.
Rossario also thinks that some of the knee replacement
failures might be an undiagnosed allergy to nickel.
“A few patients are allergic to nickel,” he said. “They can’t
have any knee replacement except a totally titanium product.
The allergy is rare, but if someone mentions it, they are
immediately sent to be tested. The number is small; it’s only
about 1 percent of the candidates for replacement.”
TITANIUM AND CHROME
ConforMIS parts are titanium on the tibia and highly
polished cobalt chrome on the femur with polyethelene
in between. The first-generation knees were too tight with
not enough bone cut, said Rossario, who is now using the >>
Rossario shows the
titanium and polyethylene
pieces of
the ConforMIS knee
replacement. The total
replacement is shown
in the photo above.
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