The promise is incredible but the pathway isn’t clear
On our Facebook and Twitter feeds yesterday, we posted about the incredible news from Spain late last week that a man with cancer was provided a custom rib cage by Australian medical device company Anatomics and the team of doctors at Salamanca University Hospital.
The rib cage, 3D Printed in titanium, was designed for the customer using CAT Scan data converted into a CAD design, and then printed on an Arcam Electron Beam Melting 3D Printer.
This incredible story sets the stage for a broader discussion of 3D Printed prosthetics. What are they? Are they better than traditional implants? If so, why? And for those of us with creaky knees or hips, can I get one?
In this post, we aim to outline a brief history of metal prosthetics, note some of the key benefits of 3D Printing for orthopedic surgery, and discuss a few hurdles to adoption that 3D Printed prosthetics face.
A brief history of metal “bone mimicry”
Ever since people have experienced failing joints, doctors have tried to develop new and better ways to stabilize and revitalize them. In recent decades, that has taken the form of prosthetic implant devices which effectively mimic the behavior of failing or failed bone. Companies like Medtronic and DePuy have mass produced replacement joint components of varying shapes and sizes, which are implanted into the body during surgery. The inherent risk of an implant, however, is that the patient’s body rejects it. If it’s dimensionally inaccurate in the wrong place or made of the wrong material, for example, it can lead to a host of complications tied to the body’s rejection of the implant. Recognizing these challenges, actions have been taken and advances made. Still, there aren’t perfect solutions. Mass produced implants can effectively serve the bulk of the population, but when a part doesn’t quite fit, it’s forced to fit by way of bone sawing and other surgical techniques. Once the implant is in, getting it to integrate with the patient’s skeletal system is another issue. Dr. Peter Sculco, an orthopedic surgeon with New York City’s Hospital for Special Surgery, spoke to some of the progress of the past two decades in combating this issue: “First there was a metal mesh, then small cobalt chrome metallic beads, then a titanium plasma spray.” Still, he noted the key shortcoming of those advances: “These techniques encourage bone to grow onto, but not into implants.”
Custom matching at the macro and micro level
3D Printing addresses both of these lingering issues.
For those cases where a size S, M, L, or XL implant doesn’t quite fit, 3D Printing allows for custom designed implants to match a patient’s unique anatomy. This minimizes the impact that the surgery needs to have on surrounding muscular systems, expediting the time it takes for the muscles to reform around the implant and shortening recovery times. The story from Salamanca is a perfect case example of this – the patient’s cancer called for a unique geometry that simply wasn’t available in mass produced form.
Additionally , 3D Printing opens the door to bone growth into the implants themselves. Bone is inherently porous, and will grow into metallic structures that can match its porosity. Prior to the advent of 3D Printing, creating such porous structures via traditional manufacturing methods was extremely time and labor intensive. “The manufacturing process was restricted to a predetermined structure [which] limited the shapes and porosity of the designed metal,” Sculco said. 3D Printing allows for this porosity to be integrated into the design at the time of its manufacture. So not only can prosthetic designs be matched to the specific body geometry of the patient in question, but different microstructures can be embedded into the prosthetic to match the desired porosity and stiffness of the bone in question. As Sculco notes, this is very advantageous in a complex surgery with varying amounts of bone loss. “The microscopic 3D structure and overall porosity can be carefully calculated to reflect the surrounding bone environment and such biomimicry optimizes bone ingrowth and implant fixation.” In sum, with 3D Printing, a patient’s bone and the implant become a single functioning part rather than two separate parts that find a way to cohabitate, as with traditional prosthetics.
Hurdles for 3D Printed Prosthetics
While 3D printed implants offer tremendous promise for the reasons outlined, don’t sign up for your new knee or hip just yet. There are a few barriers that limit custom prosthetics from becoming commonplace in the immediate term.
The first hurdle to clear is demonstrated performance. 3D Printed prosthetics are fairly new phenomena – while skulls, vertebra, and jaws have all been printed, for instance, the rib cage and sternum case was a world first. So while the possibilities for improved patient care seem tremendous, there is still a lot of testing and learning to be done. It will be important to watch how cases like the cancer patient in Spain unfold, to see whether ongoing performance in these special case exemptions are positive. It’s worth noting that 3D Printed parts are not as inherently strong as forged parts – which is the current process for traditional metal medical implants. While they are stronger than cast parts, they simply wear down faster than forged parts in a lab testing environment. This may not matter if the implant integrates with the existing skeletal system, but this tradeoff of osteointegration vs. impact resistance over time is at the crux of demonstrating the superiority of printed implants or traditional options.
Presuming data favorable to 3D Printing continues to come back, you can assume more companies will push into the sphere of registering products tailored for 3D Printing. As Matthew DiPrima of the FDA told participants at the IPQC Summit for Additive Manufacturing in Life Sciences, more than 70 3D printed devices have been cleared via the 510(k) pathway, including patient matched implants (e.g., skull), patient-matched surgical guides, dental devices, and orthopedic devices. While those approvals have taken place, DiPrima noted that draft technical guidance for medical device companies is still to be published by the FDA later this year. Until then, companies exploring 3D Printed innovations face a fairly uncertain approval pathway. Once that guidance is provided, it remains to be seen how narrow or broad the guidance will be. The default means of 3D Printing metal prosthetics is by selectively fusing grains of metal powder – something that is subject to the inherent variability of a laser, among other variables. How directive the FDA wants to be remains to be seen.
And that is just approval in America. There is no governing body worldwide. So 3D Printed innovations will need to go through separate approval processes for the governing body in each market where it would like to sell 3D Printed solutions en masse.
3D Printed prosthetics hold a world of promise and developments in this space should be watched closely. In conjunction with 3D Printed assays for drug testing, they represent two fairly near term game changing 3D printing applications in the life sciences space. With all of that said, keep being nice to your knees! Custom 3D Printed implants for all are coming as fast as they can, but there’s still a bit of ways to go.
Cullen Hilkene is CEO of 3Diligent, the Sourcing Solution for Industrial Grade Rapid Manufacturing. He is an alumnus of Princeton University, the UCLA Anderson School of Management, and Deloitte Strategy and Operations Consulting. For more information about 3D Printing and to access 3Diligent’s marketplace of 3D Printing vendors, visit www.3Diligent.com.