Though 3D printing is only slowly being adopted as a means of creating custom-tailored implants, the technology has been used for such purposes even before 3D printing was “cool”. About three years ago, one doctor at Newcastle-upon-Tyne Hospitals NHS Trust found that, for a patient with bone cancer, only 3D printing could help.
Chondrosarcoma had spread to the majority of one man’s pelvis leaving doctors with one possible option. Dr. Craig Gerrand, a consultant orthopaedic surgeon explains, “Since this cancer does not respond to drugs or radiotherapy, the only option was to remove half of the pelvis.” Though there’s always the risk that an implant might not fit a patient properly, in the case of Dr. Gerrand’s patient, there would be nothing left, after the surgery, for an implant to fit to. The doctor explained that removing the pelvis would leave the patient’s legs “hanging” and that they’d have to be attached directly to the spine. So, instead, the patient agreed to undergo an experimental, 3D-printed half pelvis implant.
In order to get the fit just right, the doctors first scanned the patient to determine how much bone would need to be removed and replaced. After designing a model to fill in the missing area, the implant was 3D printed out of titanium with the laser sintering process. The titanium part was then coated in a mineral to aid in the natural regeneration of bone while in the body. Finally, a standard hip implant was fitted into the 3D printed pelvis socket. The surgery to install the new pelvis half took 12 hours, with the surgical team relying on surgical navigation technology. As Dr. Gerrand points out, “It’s quite easy with a complex organ such as the pelvis to get lost or take too much or too little bone. Using surgical navigation technology means you can cut the bone exactly where you planned to cut.” Since the surgery took place about three years ago, the patient has been walking well with the help of a stick, one small example of the possible longevity of 3D printed implants.
While at the 3D Printer World Expo, Mark Dewey of Stratasys retailer, Purple Platypus, told an audience that 3D printing hasn’t been used all that often for internal implant purposes. I asked Andrea Stevenson Won, of Biomodal, why that might be and why Oxford Performance Materials was able to 3D print their cranial implants, given what Mark had said. Though she didn’t claim to be a medical expert, she suggested that, when it comes to most implants — such as a hip or, in this case, a pelvis — they have to support a great deal of weight. So, with Dr. Gerrand’s patient, 3D printed titanium worked well. At the same time, such a process can be extremely costly. Andrea believed that, until 3D metal printing is less cost-prohibitive or non-metal 3D printing produces stronger materials, it would be more likely that 3D printing will be used to tailor less weight-bearing implants, such as OPM’s cranial implant. At the same time, these procedures still have to overcome a number of obstacles from regulatory agencies, like the FDA. What the case of the 3D printed pelvis indicates, then, is that we’re still at the beginning of the curve, in terms of 3D printed implants, but that we’re slowly making progress.
Source: The Daily Mail