3D-Printed Skull Implants Enter the OR
When we wrote about Jiahone Guo, who suffered a blow to the head during a soccer match and needed a custom cranial implant to save his life, CNC was the manufacturing process of choice. But that may be changing.
By converting CT scans into a 3D model, a CAD program helped biomedical professionals to sculpt a patch that would be a precise fit to Guo’s skull. The implant was then created with a CNC machine, which cuts away at a block of material through a subtractive process--much like how a sculptor would chip away at marble, but much more quickly and accurately.
At the time, CNC was the process of choice largely because it was the only choice (at least in the U.S.). The polymer in question, PEEK (polyether ether ketone), had not yet been approved by the FDA if it were made with a 3D printer.
The problem is that additive manufacturing processes can fundamentally change the physical properties of the metal or plastic substrates that it uses, thus making them a tricky choice for implants. Furthermore, in order to be printed, most polymers must melt easily, which is a feature the FDA wouldn’t want coming with a prosthesis.
The FDA would have to ensure that a 3D-printed polymer would hold up just as well as a seemingly identical implant made with a CNC machine. So instead of using a filament that could be easily melted through fused deposition modeling, OPM opted for selective laser sintering. Here, implant-grade PEKK is deposited in powder form and is then melted into a specific shape with a laser.
Now, Oxford Performance Materials (OPM) has been awarded such a 3D printing patent for its PEKK (polyether ketone ketone) polymer. PEKK is similar to PEEK, but it trades an ether for a ketone within its chemical composition to create a polymer that offers the same similarities to bone as PEEK, but with twice the compressive strength.
Not even a month after its approval, OPM’s OsteoFab Patient Specific Cranial Device was successfully used in skull surgery for a patient in Long Island, N.Y. And for this surgery, lasers weren’t limited to the 3D-printing process.
OPM uses a light metrology tool developed at the Connecticut Center for Advanced Technology that uses light to perform a three-dimensional scan of printed implants that can then be compared to original digital model.
While this new process is clearly cutting-edge, OPM CEO Scott DeFelice says that compared to traditional implants, OsteoFab is actually a money saver. Because a 3D printer is able to replicate the digital model so accurately, you save time, money and cut down on risk to the patient because you no longer have to further sculpt the implant (or the patient’s skull) during surgery.