Ever since we imagined the future of medical technology, we’ve toyed with the idea of replacing body parts that are missing or no longer work. In the final scene of the 1980s Star Wars movie The Empire Strikes Back, for example, Luke Skywalker receives an indistinguishably realistic prosthetic hand from a finicky medical droid. Now, we’re closer than ever to realizing that vision (although probably without fuss).
Over the past decade, healthcare professionals and researchers have embraced additive manufacturing technologies, more commonly referred to as 3D printing, to make great strides in their respective fields. The process was used to create prostheses, custom orthopedic implants, patient-specific anatomical models, and surgical cutting guides. And as researchers and bioengineers work to expand the realm of possible applications, surgeons and physicians have begun to use point-of-care technology.
For many it has proven to be an invaluable tool.
David Zopf straddles the line between scientist and doctor; As an Affiliate Professor at the University of Michigan, he conducts research at the intersection of biomedical engineering and 3D printing. And as a pediatric surgeon there, he works with children born with head and neck deformities.
In 2019, a 9-year-old boy with cerebral palsy – a group of disorders that affect movement and posture – came to his practice. His breathing was extremely labored and his parents had tried unsuccessfully to alleviate the problem with other specialists. “These kids will work really hard with every breath,” Zopf says. “It’s almost like they snore when they’re awake.”
The boy lacked the muscle tone to prevent his upper airway from collapsing spontaneously; every breath was a struggle between his lungs and the muscles of his throat. What he needed was a simple device to keep the airway open, so Zopf took careful measurements and then came up with a design for a 3D-printed device that would bypass the obstruction.
A few days later, he implanted a prototype in the boy’s throat. “There was an immediate improvement,” says Zopf. “His eyes widened and I saw him smile. He took a deep breath – that struggle for every breath was relieved.
3D printers have long been hailed for their “rapid prototyping” capability. Engineers can quickly produce unique iterations of a device and modify them if something goes wrong. In the medical field, the same qualities allow doctors to quickly produce devices adapted to the anatomy of a patient at a relatively low cost. Once a practitioner has access to a 3D printer, the marginal cost of producing a device is often no more than a few dollars.
(Credit: Geoff Fosbrook/Formlabs)
Eliminate surgical uncertainty
In 2018, Associate Professor of Orthopedic Surgery Alexis Dang had already accumulated more than 5 years of experience using 3D printers at the University of California, San Francisco. He used the devices to make implants and dental appliances to test on rodents with fractured bones and fused spines. But he had yet to implement the devices in his clinical work at the San Francisco Veterans Affairs Medical Center.
That changed when a patient arrived with an unusual illness. The 28-year-old veteran suffered from chronic shoulder pain, but after careful examination, Dang determined the cause was an improperly healed collarbone. The patient had fractured his collarbone as a teenager and allowed it to heal naturally, but now he was paying the price: the bone had shortened during the healing process, causing the man to have poor posture. go sideways and interfere with his current job as a professional photographer.
Dang opted for a procedure that was both unusual and unpredictable. It would make a diagonal cut through the man’s collarbone, allowing the surgeon to slide the two halves of the collarbone in opposite directions and ultimately lengthen the bone while maintaining contact between the two sections. Then he secured the sections together using an alloy plate.
“It would have been incredibly difficult to figure out mid-surgery because you kind of have to guess how things are going to move based on how you cut the bone,” Dang says. Using data from a CT scan, he 3D-printed a life-size replica of the veteran’s collarbone. He and his team then experimented with different cutting angles and plate sizes until they found the best fit. “[Once] we knew where to make our cut and where to put the plate,” says Dang, “it became a relatively routine operation.
Now, a few years later, the hospital uses 3D printing to model hundreds of surgeries each year. Sometimes, as in the case of the veteran’s shortened collarbone, models help surgeons meticulously rehearse a difficult operation. Other times, the models help surgeons decide if surgery is even necessary.
More frequently, replicas are shown to patients to help explain the procedures. In 2015, Zopf diagnosed a 15-year-old boy with an abnormal tissue growth, called a polyp, that created pressure between his left eye and his brain. To help the patient visualize the problem, he printed an exact replica of the tumor in plastic.
(Credit: Elizabeth Gourlay/Formlabs)
“Having the patient be able to see the extent of the tumor and where it was positioned, that really provided another level of informed consent,” says Zopf.
While surgical modeling has proven incredibly useful, plastic replicas are a far cry from the sci-fi vision of functional, fabricated body parts. This fantasy, however, is closer to reality than you might imagine.
“I think it will be at least another 10 years before we can print a full-sized functional human heart that can be transplanted,” says Tal Dvir, the driving force behind the Laboratory of Tissue Engineering and Regenerative Medicine at the Institute. Tel Aviv University in Israel. “But I really think that’s the future of medicine. We’re going to create organs in the lab and transplant them.
In recent years, this new scientific field has emerged at the intersection of stem cell research, 3D printing and medicine. In 2019, the Dvir team bio-printed the very first human heart, though about the size of a grape. The researchers started by taking a fat biopsy from the stomach of a lucky volunteer, then separating the cells from the extracellular fluid. They reprogrammed the cells to become pluripotent stem cells, capable of dividing into several different cell types, and then differentiated them again into cardiac or endothelial tissue.
Once the research team had these building blocks, they loaded them into a multi-material 3D printer and watched as the machine rearranged the biological components into the shape of a tiny human heart – complete with blood vessels, arteries and veins.
To date, bioprinting has remained a research-based speculative field. But, as problems arise, scientists find a way forward. As stem cells continued to die outside of a living body, a Harvard team developed a technique to 3D printing vascular channels in dense cellular matrices. When bioprinted structures have regularly collapsed due to poor structural integrity, a team of researchers from Tel Aviv University developed a polymer which could be added to “bioink” to increase its strength.
According to Dvir, two lingering issues remain major obstacles to realizing a vision of bioprinted human tissue. The first is practical: once an organ is printed, how do researchers train it to function with reliable vigor? The second is the complex question of how to regulate the technology once it becomes viable. “With any new medical technology, it’s a long process of working with the FDA to make sure it’s going to be as safe as possible with minimal risk,” Zopf says.
Still, proponents remain hopeful that 3D printers will soon be able to build a liver from a patient’s thigh fat or print healthy skin for a burn victim. Unlike the hand of Luke Skywalker, these fabrics do not rely on wires and circuits. They will be the real thing.