Beyond the hype, how is 3D printing really changing medical practice?

The outlandish claims made for the capabilities of 3D printing are a bugbear for many and nowhere do they get much more outlandish than in the medical sphere. Indeed, reports of 3D printed tissue and even organs being a possibility for the future are a regular fixture in the news.

However, while these possibilities are obviously exciting, they can have a tendency to obscure the remarkable ways in which additive manufacturing are already being used in medicine to improve patient outcomes. One remarkable recent instance involves Belgian company LayerWise using metal 3D printing to produce patient-specific titanium implants as part of a pioneering facial reconstruction. Stephen Power was severely injured in a motorcycling accident near Cardiff where he broke both arms and damaged his right leg so badly it required a bone graft. Stephen also suffered major injuries to his head and face. He only regained consciousness after several months in hospital. A specialist team led by consultant maxillofacial surgeon Adrian Sugar at the Morriston Hospital in Swansea, successfully dealt with all facial injuries except Power's left cheek and eye socket. The patient's cheekbone was too far out and his eye was sunken and had dropped. Due to the close proximity of critical and sensitive anatomical structures, the team applied a more accurate expertise approach. This strategy ensured no further damage to his eye in order to maintain his eyesight. The expertise approach entailed the latest 3D computer-aided practices applied by PDR and innovative 3D printing of the titanium implant and fixation plate by LayerWise. LayerWise manufactured the implant and fixation plate in medical-grade titanium (Ti6Al4V ELI) in accordance with the ISO 13485 standard. "The 3D printing technology mastered by LayerWise is perfectly suited for producing this kind of ultra strong, precise and lightweight titanium implants," says Peter Mercelis, managing director of LayerWise. Romy Ballieux from LayerWise's Medical Business Unit says: "The reconstructive orbital floor plate plays an essential role in the repositioning of the eye in light of the targeted facial symmetry and eye alignment. "LayerWise produced the floor plate, and polished its upper surface to minimise friction with soft tissues. The floor plate was fixated to the zygomatic bone through the plate's dedicated slip with attachment holes. The 3D printing technology successfully maintained the accuracy of the precise medical imaging data, pre-operative planning and implant design. The 0.1mm geometric accuracy of the floor plate's freeform surfaces could not be achieved using traditional manufacturing methods." Accuracy is even more critical with regard to the fixation plate. This fairly long, slim, curved 3D printed plate requires precise positioning to be able to tie together many fractured bone pieces of the cheek region. A custom-fitting guide was used to fit securely around the anatomy, with slots located to guide the surgeon's movement when positioning the plate. The fixation plate restored the correct anatomical connection between the frontal, zygomatic and temporal bone. This connection contributed to the successful reconstruction of the patient's anatomy, providing the best possible facial symmetry. Ballieux notes: "Dedicated medical engineering specialising in the production aspects of metal 3D printing was key in achieving the impressive facial reconstruction in such a short timespan. The digital process resulted in the 3D printed implant and fixation plate produced in a single manufacturing step in only a couple of hours." Following his recovery, Power describes the results of the surgery as 'totally life changing'. Instead of using a hat and glasses to mask his injuries, he is now more able to do day-to-day things and go outside. The improved facial symmetry and alignment of his eyes, achieved with the LayerWise implant and fixation plate have also clearly made a big difference to the patient. "We are confident that our metal 3D printing technology is capable of improving the quality of life of many more patients," says Ballieux. "The fast-turnaround digital process, from medical imaging up to the finalised 3D printed implants, delivers the required implant geometry and precision to obtain such great facial reconstructions." These implants were the result of a close collaboration between LayerWise specialists and PDR design experts Sean Peel and Dr. Dominic Eggbeer. PDR has a formal collaboration with the Maxillofacial Unit at Morriston Hospital: CARTIS (Centre for Applied Reconstructive Technologies in Surgery). Another interesting, if perhaps slightly more frivolous example (albeit not for the patient) comes from the US, where additive manufacturing was used to create a unique knee joint for a cat. The veternary surgeon in question, Dr Denis Marcellin-Little, has worked with additive manufacturing for more than 10 years, with much of his research focusing on medical applications, including over 300 models for practising and designing surgeries. Early on, it was decided that the two main components of the artificial knee would be made using direct metal laser-sintering (DMLS) machine from EOS. DMLS can work with a number of different metals; two of which titanium and cobalt chromium – are frequently used for implants. Each has its advantages. "Titanium is great for bone ingrowth," Marcellin-Little points out, "but it's much softer than cobalt chromium." The loads on a titanium femoral head would wear the metal down eventually. Because the implant components would already be thin in some places, they might be subject to breaking or cracking if they eroded further. "So, cobalt chromium was our best choice," says Marcellin-Little. The selection of DMLS for manufacturing the knee was crucial to its design. The addition of the stems and the incorporation of features to match up with custom drilling and cutting guides gave the metal components shapes that were not readily manufacturable by traditional moulding or subtractive cutting processes. After several iterations and a thorough final review, the team sent the metal component models to EOS' global headquarters in Krailling, Germany for manufacture. The cobalt-chrome parts presented a special challenge. Although EOS had been adding surface roughness and porosity to titanium dental prostheses and implants for years, this was the first porous cobalt-chrome device they had produced. EOS successfully manufactured six sets of the metal components and shipped them back to the U.S.The surgery was successful and one of the greatest benefits of this project is the additional experience the researchers gained by designing for additive manufacturing. "When I look back and compare the implants we were building with AM 10 years ago to what we design now, it's like night and day," Marcellin-Little says. "The recent ones are more refined, more precise, and more sophisticated... The main change this technology has brought is that the manufacturing process is no longer a barrier to the imagination of an orthopaedic clinician who needs to create something very specific."