3D printing medical breakthroughs are driven by enabling technologies and developments in other, typically unrelated, disciplines.
Medical applications of 3D printing technology date back to the earliest days of stereolithography and, if you can believe it, even earlier. Just recently, I sat with an engineer who recounted times during the early 1980s, after the advent of computed tomography (CT) in the late 1970s, when they would create crude anatomical models through an “additive” process.
CT scans are akin to x-ray slices of an object. In the ‘old days’, one would take a sheet of plastic and cut out, by hand, the cross sectional image from a piece of x-ray film. Stacking successive sheets one on top of each other would form a crude 3D model of an anatomic object, and this is exactly how it was done before 3D printing was invented.
Chuck Hull, the inventor of stereolithography and founder and Chief Technology Officer of 3D Systems, probably didn’t imagine Stereolithography as a game-changing tool for the medical industry, but it has had a tremendous impact on healthcare and promises even greater benefits in the future. Achieving these greater gains, however, will require utilising further technologies—I call them “enabling technologies.” Yet, to identify the enabling technologies that will propel us into the future, we must look to the past. With the benefit of hindsight, we can identify the supporting technological advances that first enabled medical applications of 3D printing, and start to recognise the puzzle pieces still missing.
The key enabling technologies that have brought us to our current medical applications include:
- The advent of volumetric medical imaging (CT in the 1970s, MRI in the 1980s),
- The advent of 3D printing (also known as “additive manufacturing”),
- The advent of biocompatible materials (circa 1996, Stereocol by Astra Zeneca in the UK, later Huntsman and 3D Systems) as well as laser sintering in nylon,
- The advent of haptic-enabled design tools,
- The advent of cone-beam computed tomography (for head and neck use, circa 2000),
- The widespread use of virtual surgical planning combined with personalised instrumentation
- The advent of 3D printing in biocompatible metals, and
- The bioprinting of living cells for replacing human parts with human parts.
Volumetric imaging and 3D printing are obviously the foundational technologies in enabling current medical applications of 3D printing. Combining these two revolutionary technologies together places life-size, physical 3D replica models into surgeons’ hands before major reconstructive surgeries. These models help surgeons better prepare for surgery, make better decisions during surgery and, most importantly, help improve patient outcomes while reducing surgical time. These anatomical models also became the basis for the design of personalised implants for areas ranging from the skull to the ankle. 3D Systems Medical Modeling is used by more surgeons worldwide in this area than any other for “tactile” surgical guidance.
Biocompatible materials emerged in the mid-1990s and opened up the feasibility of taking these tools into the operating theatre, transforming outputs of 3D printing from mere diagnostic and planning tools to surgical guides.
Haptic-enabled design tools were commercialised in the early 2000s, making the hugely labourious process of designing organic shapes simple and intuitive. Overnight, designers discovered new applications in haptic-enabled medical design, creating freeform designs that were impossible to imagine before.
Cone-Beam Computed Tomography (CBCT)
In the head and neck surgical specialties, no bigger invention has impacted the use of 3D printing than Cone-Beam Computed Tomography (CBCT). This is a smaller version of a hospital CT scanner, designed and priced to fit within a doctor’s office. Quick, affordable and with much less radiation than a typical CT scan, these devices have transformed diagnostic imaging for specialties like orthodontics, oral and maxillofacial surgery and are now impacting general dentistry. The explosion of volumetric medical image data has enabled broader access to medical tools like 3D printed dental implant drill guides, invisible orthodontic devices and 3D printed occlusal wafers used in orthognathic surgery.
Additive manufacturing of implantable metals emerged in the mid-2000s, made possible by both electron beam-based and laser-based technologies. Today, the production of titanium, titanium alloy and cobalt-chromium implants, focussed mostly around porous geometries, represents only a small percentage of the overall 3D printing medical market, but is rising quickly. At the same time, throughput of 3D printers is going up, quality of the parts is going up and cost of the components in production is going down. This trend means that metals printing is poised to make major impacts in manufacturing of off-the-shelf joint replacement and trauma devices over the next ten years.
Virtual surgical planning and surgical simulators help make surgery safer and more effective
Virtual surgical planning combines accurate, computer-based planning for surgical procedures in the computer with custom-designed, disposable instruments meant to carry the virtual plan from the computer to the operating room. Consider surgeons who cut bone for relocation or replacement with another piece of bone or an implant. Using virtual surgical planning, surgeons can use instruments for cutting a bone that fits along the patient’s bone structure and guides a saw-blade in a precise place, thus cutting the bone exactly as it was done digitally.
Bioprinting is typically used as a term today to describe either scaffold-based printing or true 3D biologic structure printing, using living cells as print materials. These emergent capabilities open up a new world of possibilities, allowing for the deposit of cells into infinitely complex and “living” 3D structures. Researchers at Cornell University, for example, are using live cells to 3D print ears. Researchers at Wake Forest University are looking at how to develop replacement organs using a patient’s cells, with the overall goal of reducing demand for donated organs and the rejection rates of transplanted organs.
The market for 3D-printed medical devices is larger than most people realise and growing rapidly. Dentistry, orthodontics and the hearing aid industries all rely on 3D printing to produce millions of patient-specific pieces every year. In orthopedics, these technologies are impacting surgery in many ways, most notably in the use of custom implants and custom instruments for personalised surgical procedures, as well as the production of off-the-shelf implants. All combined in just orthopedic surgery 3D printing touches more than 150,000 patients per year.
Centre for Applied Reconstructive Technologies
CARTIS, the Center for Applied Reconstructive Technologies in Surgery, in Cardiff, Wales, has been particularly successful in delivering 3D printed surgical guides and implants customised to a patient’s data. By having designers and surgeons work together, they have proved that complex surgeries can be less invasive, and with faster, more successful outcomes than before.
That same usable 3D data from the patient has allowed major advances in virtual surgery planning.
NYU’s Langone Center uses 3D technology on many procedures, notably one that they call ‘Jaw in a Day’ that allows the planning of critical jaw surgeries using a combination of 3D Systems’ VSP (Virtual Surgical Planning) and Stereolithography. ‘Jaw in a Day’ allows patients with large tumours of the mandible or maxilla to check into the hospital with a serious problem and check out the next day with a new tumour-free, functional jaw—complete with teeth. This process combines cutting-edge technology with virtual surgical planning to create disposable, personalised surgical tools and even custom-designed teeth—all meant to reconstruct the patient in a single procedure versus what’s typically taken several surgeries to accomplish in the past.
Use of 3D data has also fuelled breakthroughs in touch-based simulation for surgeons—not unlike flight simulations for pilots. Simbionix’s Procedure Rehearsal Studio (PRS), for example, utilises an individual’s medical image data to create an immersive, virtual simulation for a medical procedure.
Combining this technology with existing virtual surgical planning technology creates an entirely digital workflow for preparing and conducting a surgery. In a day not so far away, surgeons will be able to take a CT scan, import it into a surgical planning software, simulate the procedure in a very realistic way and then quickly output 3D printed instruments or templates to enable a seamless transfer of the digital plan to the surgical theater. Far-fetched? I don’t think so.
So what is ahead? What are the enabling technologies of tomorrow that will drive further innovation in 3D-printed medicine and how will they impact the space? I believe a number of developments will play a key role.
First, I expect to see 3D printing move from today’s uses for hard-tissue (bone) reconstructive procedures to more work in organs and other soft tissues. In fact, work in soft-tissue 3D printing is already becoming a topic of conversation. At Tulane University in New Orleans, professors are working out how to recreate realistic human organs for practice models. This means developing materials that resemble the softer feel of, say, a kidney, so that surgeons can practice their surgeries before performing them. Many of these procedures are starting to use robotic surgical assistance. The rise of robotics will bring greater automation and control to surgical procedures—an important factor considering our rapid shift from traditional to digital surgical workflows and further compelling the need for accurate surgical planning.
Formerly conjoined Filipino twins benefitted from digital surgical advances at CHAM
Second, as these technologies become more sophisticated, and price points continue to decline, we’re going to witness a large-scale localisation of medical 3D printing. Within one decade, expect to see push-button 3D printing capabilities used with increasing frequency at hospital facilities and even your local surgeons’ office. Already, surgeons and medical schools are beginning to reimagine the surgeon’s desktop, understanding that no practitioner’s workspace will be complete without 3D printing, haptic modeling for intuitive design and virtual surgical planning tools.
Finally, I believe design to mimic nature is the next frontier. In ten to fifteen years from now, we will view today’s chunky, non-anatomic-looking hip, knee, ankle and shoulder replacements as primitive. We are in the process of developing a new, more eloquent design methodology—a design language powered by the body and its needs. This will give rise to a new genre of implants, designed with the stress and strain of adjacent tissues in mind and optimised for both functional and mechanical properties.
Until now the healthcare applications for 3D printing have been exciting, but they pale in comparison to what’s to come. When we combine the incredible technologies available to us in the near tomorrow and apply them to the medical field, we will unleash new, powerful and life-altering capabilities. Of all the incredible applications of 3D printing, healthcare is the most “human” of all. And in the next decade, we will see this “human” technology touch the lives of millions of our fellow humans.