Using 3-D printing techniques, complex structures such as heart openings can be designed with such accuracy that implants work better and recovery from surgery is improved.
This article first appeared in the April 2016 issue of HealthLeaders magazine.
Three-dimensional printing in healthcare has received a lot of attention as a gee-whiz, futuristic technology, with photos of prosthetics for injured soldiers and children. But 3-D printing is about to get a whole lot more personal. Sophisticated imaging and modeling means that complex structures such as heart openings can be designed with such accuracy that implants work better and recovery from surgery is improved.
"3-D printing already is becoming more patient-specific, and that will continue. Instead of having different sizes that you have to fit the patient into, implants will be modeled from the patient's own anatomy," says Joseph Lipman, MS, director of device development at Hospital for Special Surgery in New York City. Physicians at HSS perform more than 29,000 surgical procedures annually.
The 3-D printing market is expected to reach more than $4 billion by 2018, according to a 2014 report by Visiongain, a London-based intelligence provider. Not only are the printers being used to customize medical implants but also the associated models, guides, and tools.
HSS uses stacked 2-D scans to create detailed 3-D images that can then be printed using ABS plastic. Use cases are increasingly sophisticated. For instance, a recent surgery involved a hip replacement complicated by bone that had grown around a previously implanted plate. The surgeon used a 3-D printed model to practice removing the plate to make the surgery more effective and efficient.
"Surgeons are tactile, and before we could only show them 2-D pictures and they'd have to create the 3-D image in their head," says Lipman, who collaborates with HSS' orthopedic surgeons on 3-D modeling and printing. "Now they have a 3-D physical object to give them a sense of scale and help visualize how to cut the bone and better align it."
As 3-D printers evolve in granularity and the materials they use, HSS has started experimenting with replacement joints for fingers, thumbs, and elbows—something that had been out of reach thus far because of the size and complexity of the joints. "We now can make the metal porous where we need it to be porous, enabling implants to affix better to the bone, change shape, and be smaller," he says.
Lipman says 3-D-printed models also will help surgeons to communicate better with patients. They can use the model to spark a conversation about expectations and to explain "tricky anatomy." The visual aid, he says, will help patients become more educated about their rehabilitation and lead to improved outcomes.
Heart openings
At Henry Ford Hospital's Center for Structural Heart Disease, 3-D printing is being squarely focused on the problem of repairing hearts of all shapes and sizes.
Center director William O'Neill, MD, FACC, says the center is printing customized models of each patient's heart to properly size new bioprosthetic valves, as well as devices used to seal off left atrial appendage occlusions. Typically, the devices come in a circular shape. But O'Neill says 3-D imaging reveals many of the heart openings they're designed to fit in are actually oval or other odd shapes. Incorrectly sizing the devices can lead to leaks, which, once detected, have to be sealed in another surgery.
By printing a model of the heart that matches the patient's anatomy and allows doctors to plan procedures in advance, follow-up surgeries can be avoided.
The project is currently in the pilot incubator stage, but O'Neill says he is confident it will become an important application for cardiac departments. "Sizing valves and deciding how to place them with 3-D images and models could be a mainstay," he says.
Bone reconstruction
David Dean, PhD, associate professor in the department of plastic surgery at The Ohio State University in Columbus, has been making use of 3-D printing for clinical cases since the late 1990s, studying how to print replacements for skull bone as well as the tools and guides needed to properly set them. Implants for the skull must be carefully designed because they could inadvertently pinch off arteries to the scalp or press on the brain and cause damage.
Today, through a grant from the Department of Defense Armed Forces Institute of Regenerative Medicine, Dean is focused on facial reconstruction, specifically for soldiers, including those injured by improvised explosive devices, or IEDs. "Craniomaxillo-facial injuries make up more than one-quarter of today's battlefield injuries," he says.
Dean 3-D prints porous, resorbable implants, which are then seeded with bone progenitor cells. Those cells are cultured in a way that results in a bonelike coating of the implant prior to its implantation. Once implanted, the body replaces the implant with bone. During the replacement process, the 3-D printed resorbable polymer fully resorbs in time for the bone to remodel itself, a necessary process if the bone is to become strong.
Dean's current research is focused on the lower jaw because the blood supply in the upper jaw is more challenging. This research is expected to go to clinical trial at the end of 2018.
Printing costs
While 3-D printing is decidedly the wave of the future, who will absorb the costs is not yet wholly decided. At Mercy Medical Center in Baltimore, Chief of Orthopedics Marc Hungerford, MD, MBA, has worked with the hospital's 3-D printing vendor to even out costs.
Mercy uses a qualified Boston-based factory to manufacture perfect matches of patients' knees using 3-D printing, along with kits of customized instruments to set them.
"We know the better an implant fits, the better it works," Hungerford says. "It's the difference between a tailored suit and an off-the-rack suit."
Though he says there is not enough data to support his theory yet, outcomes with 3-D-printed services should improve patient outcomes through a better fit after the implant.
Because the vendor charges the same amount for a custom-made implant as a traditional one, the hospital has approved the 3-D procedures. "If the implant was twice as expensive, the hospital would say no," he says. Knee replacements are a bundled service so implant costs are more or less expensive, but hospital reimbursement is fixed.
He says if custom-made 3-D implants ever prove to be of better quality and price than traditional implants, they could be mandated.
Some industry observers believe the prospect of better outcomes will resonate with employers who pay for bundled services. If recovery time drops by a week or two using customized implants, employers will consider them.
Becoming the better alternative
John P. Geibel, DSc, MD, AGAF, is Yale School of Medicine professor of surgery (gastrointestinal) and of cellular and molecular physiology. He says 3-D printing will become attractive to payers when they outpace the alternative, such as complicated transplants, expensive treatments, and recurring hospitalizations.
Geibel is researching how 3-D printing can be used to cure gastrointestinal conditions such as short gut syndrome, in which children are born with an intestinal malformation that prevents them from properly absorbing nutrients and secreting waste.
Currently these patients must receive complex and costly inpatient care to ensure proper nutrition and bowel movements. Although there are intestinal transplants that can be performed, they are rare—only about 100 are done every year, with 10,000 adults and children waiting for the procedure—and there are considerable complications, including rejection, he says.
Geibel aims to use the patient's own cells to print sections of their intestine as well as the infrastructure, or rods, to secure the implant in place once in the patient's body. If successful, short gut syndrome patients will be able to receive iterative intestinal implants that align with the child's natural growth cycle.
In 2014, Yale announced a collaboration with 3-D bioprinting technology maker Organovo to develop bioprinted tissues for surgical implantation research. Geibel's research strategy has been intentionally slow and methodical, with no end date marked out as of yet. Instead, he is creating incremental benchmarks, including printing smaller cylindrical items, such as blood vessels and arteries, to be studied in rats.
He says his cautious approach will be instrumental in showing payers the viability of 3-D printing. "We'll be able to prove that using the individual's own cells reduces risk of rejection and might eliminate the need for antirejection drugs, which have their own side effects." Also the cost comparisons will be persuasive, he says.
For instance, total parenteral nutrition, a common treatment for intestinal failure, can cost $100,000 to $200,000 a year. "As reagents get more expensive and patients require recurrent hospitalizations, that number jumps up," he says. "These patients cost an incredible amount of money to maintain." As 3-D printing costs decrease, implants, he says, will likely be less expensive than the alternative.
So although he expects insurance companies to initially consider 3-D implants "risky" and to be conservative in approval, ultimately, he says he expects them to understand the advantage to the patient and overall care costs.
Payers already recognize the value of 3-D printing, and that will only increase if the science is supportive, according to Geibel. "If you're getting into 3-D printing, move cautiously," he says.
Henry Ford Hospital's O'Neill says, "If you don't have a clinical use for 3-D printing, it will die out." However, he says he is confident that helping resolve cardiac issues will be just one of many applications that will keep the technology around.