what size implant to use. There are no surprises during surgery."
Dr. Schaap says entering the OR with a digital map of surgery and
an idea of how the procedure will progress results in less bone resec-
tion, which is especially important when using newer implant sys-
tems. "The robot lets us make very small bone cuts and correct signif-
icant deformities because we understand the three-dimensional anato-
my of the joint," says Dr. Schaap.
• Implant alignment. Yale Fillingham, MD, a joint replacement spe-
cialist at Dartmouth-Hitchcock Medical Center in Lebanon, N.H., says
implants placed outside of a certain range of alignment have
increased risk of failing, because of the constant change in stress that
works across the bone-cement interface whenever the patient moves.
Being even just a few millimeters off in alignment can make a differ-
ence in implant lifespan.
Surgeons can use a robot's software platform to identify anatomic
reference points and anomalies, and preview the overall morphology
or the shape of the joint's bony anatomy. They then preoperatively
plan to place the tibial and femoral cuts exactly where they want
them. "One theory in support of robotics is that the technology
increases implant survivorship by letting surgeons place implants in
the correct alignment," says Dr. Fillingham.
Dr. Schaap says robotic assistance helps her establish proper
rotational alignment of the tibia and femur, especially in badly
deformed valgus externally rotated knees. Patellofemoral align-
ment is also improved, which strengthens the joint for going up
and down stairs and getting in and out of chairs. Ultimately, she
says, precise implant placement leads to improved joint mechan-
ics, which allow for better power and better feel in the joint,
important factors that impact patient satisfaction.
"If advanced imaging and pre-op planning lets you be more precise
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