like robotic-assisted surgery, patient-specific cutting guides, customized joints, and 3-D-printed implants wouldn’t be much of a
stretch in a world that spawned hoverboard technology, skyways,
rejuvenation clinics, and controlled weather.
Custom joints and patient-specific guides/instrumentation
have gained traction in the last decade as clinicians sought ways
to improve both implant alignment and surgical efficiency. Most
of the major orthopedic device makers offer these products,
though Smith & Nephew plc was the first to market with the
2008 launch of its Visionaire cutting guides and disposable size-specific tools.
The iTotal knee replacement system from Bedford, Mass.-based ConforMIS reportedly removes less bone than traditional
off-the-shelf implants, an asset that could help dissipate the
forces across the bone-implant junction more naturally. The
i Total also elevates the lateral joint line more than the medial
joint line according to patient anatomy. This dual suspension
allows the i Total to keep the joint line at the natural 3 degrees of
varus rather than directly perpendicular to the mechanical axis.
Surgeons also can choose to replace only one or two of the knee
joint’s three compartments.
The majority of custom implants and patient-specific guides
are created from preoperative 3-D computed tomography (CT)
or magnetic resonance imaging scans, typically taken four to
six weeks before the procedure. From those images, a sterile
revers mold of the patient’s knee is made, fitting snuggly onto
the ends of the bones that comprise the knee joint. The molds
guide the location of the bony cuts, helping to ensure a more
“Instead of putting rods inside a patient’s body to line things
up we are now taking a custom-ma- de plastic jig that fits right
onto a patient’s bone and that is what guides the surgeon, help-
ing him make the cuts in precisely the right places,” Burnell said.
“I think this is the major advancement in instrumentation that
we’ve seen over the last several years. The marriage of 3-D print-
ing and imaging is allowing us to use a patient’s own imaging—
their own anatomy—to design a jig that will fit directly onto that
patient’s bone and have the implant fit properly. One couldn’t ex-
ist without the other; it’s really both of those innovations together
that have really allowed this advancement to occur.”
One-half of that couple, though, is thriving quite well on its
own. Three-dimensional printing has proven itself a robust and
versatile technology in recent years, responsible for such novel-
ties as a bone fracture healing cast, ceramic/polymer bone scaf-
fold, prosthetic limbs, synthetic tissues, and anatomical practice
models (for surgery).
However, the technology still is relatively new and has yet to
attain a true foothold in the medtech arena. Consequently, much
of its use has been relegated to the academic and experimental realm (with the exception of hearing aids and dental braces):
Doctors like Nicola Bizzotto, M.D., an orthopedic and trauma
surgeon at the University of Verona Hospital (Italy), and Jason L.
Koh, M.D., chairman of orthopedic surgery at NorthShore University HealthSystem in Evanston, Ill., have taken advantage of