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Dr. Albert Woo held the tiny skull in his hands, turning it over and studying its imperfections. There was too much bone around the nose. The right eye socket was out of place. The reconstructive facial surgery would have to protect the tear ducts and delicate structures of the eye.

Woo and a colleague planned out the operation using the replica created with a 3-D printer. The next morning, when they opened up the skull of 5-year-old Myah McWilliams, they already knew what to do.

“If I’m going to take a child to the operating room, I want to know that it counts,” Woo said.

Thirty years ago, a doctor who printed out prescription orders on paper was considered revolutionary. Now doctors can print three-dimensional plastic skulls, collagen ears, even prosthetic arms. In the next 30 years, they aim to create viable human organs with 3-D printing technology.

Three-dimensional printers were invented in the 1980s and use “ink” made of heated plastic, ceramic or metal to create objects by dropping the liquid in layers as instructed by design software. The technology was originally adopted by the transportation and manufacturing industries to build molds for car, airplane and machine parts. In the 2000s, consumers joined in to print their own jewelry, toys and household goods on home printers that cost about $1,000, with 3-D patterns widely available for download.

The medical field eased into 3-D printing with simple plastic devices including hearing aids and umbilical cord clamps. By 2014, medical uses made up less than 2 percent of all 3-D printing applications. That’s expected to rise to 20 percent in the next decade, according to the medical journal Pharmacy and Therapeutics. The science is advancing rapidly. In the last three years:

  • Doctors at the University of Michigan created a 3-D model of a baby’s face from an image taken in the womb. The baby had a cyst on his face that could restrict breathing at birth, requiring a risky surgery in utero. The 3-D model informed the doctors that surgery would not be necessary.
  • A handful of children born with defective windpipes worldwide have received 3-D printed splints that open their airways until their anatomy matures.
  • During an operation to separate conjoined twins born in Washington, surgeons were guided by a 3-D mold of their entwined bodies. The boys shared a liver and a membrane surrounding their hearts. Doctors used the model, created from images in the womb, to determine the safest way to separate the twins, who recovered.

“There’s a remarkable accessibility to being able to hold a model in your hands rather than seeing it on the screen,” said Woo, an associate professor of plastic and reconstructive surgery at Washington University School of Medicine. “You’re able to look upside down, inside out and put fingers in different orifices to see how things fit.”

SURGICAL MOLDS

Woo recently performed surgery on Myah’s skull at St. Louis Children’s Hospital. Myah, 5, was born with a condition that prevented the plates in her skull from fusing properly, causing facial asymmetry.

During the surgery, Woo and Dr. Steven Couch, assistant professor of ophthalmology, referred to a plastic skull mold created from images of Myah’s head and printed in WU’s biomaterials lab. The mold showed the doctors where a tendon behind Myah’s right eye was out of place. They pulled the tendon closer to her nose, allowing her eye to move into a better position.

The mold of Myah’s facial bones and tendons is an exact replica of her complex anatomy, allowing the surgeons to more accurately plan the surgery. Woo said studying a 3-D mold before a surgery can reduce the length of an operation by half.

“In the past you had to wing it and depend more on the art of surgery,” Woo said. “But now with 3-D modeling, you’re able to have a lot more information to make a better informed decision. We hate to go in and perform a case where we have a complex procedure and afterward we’re disappointed and have to redo the surgery. Having that information helps avoid repeat surgeries.”

Surgeons can practice surgeries on the 3-D images on the computer and with the mold — planning where to cut down to the millimeter. That precision brings some confidence not only to the surgeons, but also to patients and their loved ones, such as Myah’s mother. “It makes me feel more comfortable as her mom,” said Destanie Swan of Park Hills, Mo. “It eases the stress a little bit that they can see it before they get into it.”

ON-SITE LAB

Washington University is among the few medical centers capable of 3-D printing. The biomaterials lab opened for business on the medical campus about a year ago. The mold of Myah’s skull was printed there a few weeks before her surgery, although the lab can turn around a surgical mold in a day for emergency or trauma cases. A recent order called for dozens of plastic uterus molds for medical students to study.

Before the on-site lab opened, surgeons could order a 3-D print from outside companies, but it could take a month and cost several thousand dollars. The molds can be printed with see-through materials or in color. They can be sterilized for the operating room. Some replica organs can be made out of rubber, so doctors can push against a structure that feels more like the real thing. Molds can be printed for just a few dollars in materials.

The 3-D printers have been used to create specialized helmets for babies with misshapen heads. They’ve printed copies of tumors so surgeons can determine how to extract cancerous cells without damaging healthy tissue. Anesthesiologists can practice inserting breathing tubes with models of oddly shaped airways. The 3-D molds and implants are also useful in the dental field or as replacements for jawbones.

“If a bone is completely shattered, we can use our technology to design a new bone,” Woo said. “I can create a customized cutting guide, showing exactly where I need to cut that new bone out of skull or hip or other bones in the body, then use that new bone to create the old bone that was missing.”

The lab has five 3-D printers that range in cost from $1,500 to $90,000. About 75 percent of its orders are related to medical research, education or patient care, according to Dominic Thompson, the lab’s staff scientist.

PROSTHETIC ARMS

Nabeel Chowdhury, a senior majoring in biomedical engineering, works about 10 hours a week in the lab. His senior project involves creating prosthetic arms for children using 3-D printing technology. The arms can be made for around $100, making them ideal for kids who need several prosthetics as they grow.

“Resizing is essentially the cost of the plastic,” Chowdhury said. “One of the aims of the project — eventually there is no reason why the parents of a child couldn’t make this at home.”

The arms are battery-powered and have computer chips that tell the hand to open and close when the children move certain muscles in their shoulder or upper arm. The technology needs improvement, and so far the robotic arms are more cosmetic than functional. But compared to a high-tech $30,000 prosthetic, the 3-D printed arms are a viable experiment.

“I would never pretend it’s better than the $30,000 hand,” said Dr. Charles Goldfarb, an orthopedic surgeon at Washington University and a mentor on the students’ prosthetic limb project. “We’re at the early stage of a technological breakthrough. This technology is going to get better and better very fast. It is so cheap and so relatively easy it just makes sense to do it for these kids.”

Sydney Kendall, 14, has had two prosthetic arms printed in the lab, one pink and one blue, and the students are working on a third for her. She doesn’t use the arm as a freshman at Visitation Academy, but she did get a perfect score on a science project about prosthetic limb technology. For a young woman who wants to become a surgeon, Sydney has enjoyed being the project’s first test subject.

Sydney has mastered most skills one-handed since losing her right arm in a boating accident at age 6. She would like a more durable prosthetic arm and hand with a tighter grip to help her carry objects or even type. And water resistance would be nice, too.

THE FUTURE OF 3-D

The applications for 3-D printing in the medical realm are still in their infancy. Ideally, biological 3-D printing will evolve to a point where functioning human organs can be created and the waiting lists for heart, liver or kidney transplants can be cleared out. Already, some labs have figured out how to create small strips of organ tissue that can be used to test medical treatments. For example, scientists can research the toxicity and effectiveness of drugs on liver tissue in the petri dish instead of on people in clinical trials.

The process involves harvesting cells from a patient’s biopsy and then multiplying the cells in the lab. That solution is then used as the ink in the printer. Producing an entire organ as complex as a liver or kidney is inherently more difficult. One main challenge has been figuring out how to sustain blood flow in and out of the artificial organ. The Methuselah Foundation, a Virginia-based charity, has offered a $1 million prize to the first team that can keep any large animal alive for at least 90 days with an artificial liver.

Skin and bone grafts with 3-D printed biological materials are closer to reality. Doctors at Wake Forest University can treat burns with a portable printer that applies layers of skin cells directly onto patients’ wounds. Facial implants have been printed using calcium phosphate, the primary component of human bone. Cartilage has been used in a 3-D printer to create prosthetic ears.

The first 3-D printed pill was approved last year by the Food and Drug Administration to treat epilepsy. In the future, pharmaceutical companies might download the formulas for medications straight to pharmacies, which would then print the pills themselves. Super pills with individualized ingredients might be available to people who now take multiple pills a day.

“We’re just starting to figure out what we’re doing,” Woo said. “As more and more doctors realize the capabilities we have, it really will usher in a new era of improved surgery and improved reconstruction and improved care of patients.”

Blythe Bernhard is a reporter for the St. Louis Post-Dispatch.