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ST. LOUIS — Just inside the 3D Printing Center of Excellence at SSM Health Cardinal Glennon Children's Hospital in St. Louis, wall shelves display dozens of colorful plastic models. At first glance, they look like toys.

Each model represents an effort to help or potentially change the life of a patient, many of them children. Pink, red and turquoise models of hearts represent those that need repair. A twisted green spine represents that of an infant with severe scoliosis. A white skull with multicolored pieces around the nose represents a plan for repair after a traumatic injury.

Working in three dimensions makes it easier for almost everyone — surgeons, residents, patients, and their families — to understand what's needed for treatment.

"These are my kids. I do facial things. All the skulls and stuff are mine," explained Dr. Kevin Chen, head of pediatric plastic surgery at Cardinal Glennon and the surgical director of the 3D lab, as he motioned toward the shelves. "You can imagine that it's totally different for a trainee, or even me, to understand the cuts that I have to make to separate the front of the face from the back of the face. You can spin it around and look at it. It's hugely different to have something tactile as opposed to just spinning it in your three-dimensional computer space."

Limitless uses
The lab is another evolution of what 3D printers can achieve in the medical field. In recent years, the printers have become a ubiquitous hobby tool available for homes and in libraries. But in hospitals and labs, they're used to print learning tools for in the classroom, produce equipment like stethoscopes and tourniquets to use in the field, and customize aids for radiation therapy.

During the pandemic, people used the printers to make hard-to-come-by supplies like face shields and face masks. Researchers are exploring how to 3D print drugs and even potentially print human tissues and organs. One day it may be commonplace to print skin tissue and organs on-demand.

At Cardinal Glennon, Chen works with engineers Vicky Karamouzi and Stanley Dsa to develop and print 3D-models for clinicians. The models are usually used for presurgical and preprocedural planning for complex conditions like structural heart defects, spine abnormalities, and congenital facial and skull deformities.

More precision
Cardinal Glennon established the center in 2017. The center printed the first congenital heart model in Missouri in collaboration with Saint Louis University. The center also created the first in-house printed surgical guides in Missouri.

About 60% of its work involves making models; 30% is making surgical cutting guides that can be placed inside the patient in the operating room, and 10% is patient-specific treatment, such as a nasal conformer for a patient with a cleft nose. Prefabricated conformers are symmetric, and a cleft nose is inherently asymmetric, explained Chen. A custom one made for a patient fits better.

"And so far I think my results have been better with these very, very customized, patient specific treatments," he said.

For patients who need certain types of craniofacial surgery, Chen can create a skin overlay to decide how much he wants to push a patient's facial bones forward to stretch the skin. "So I kind of have an idea of what the skin change is going to be like," he said. "This part is for how to cut the skull. And the skin overlay was to help me to decide how much to move it."

Quelled nerves
The patients and their families often see the 3D models, which helps them better understand their treatment and surgery. Sometimes, they get to take the models home.

Dsa said this can help quell nerves, especially with the parents of younger patients. "Otherwise, parents would look at the CT scans and they wouldn't understand," said Dsa. "They look at the 3D models, they have a sense of hope. They have more confidence."

"It makes it look less scary," added Karamouzi.

Chen also shows residents the models, especially ones from complex cases. "For a trainee, it's pretty much impossible to visualize unless they have something like this, to see it," he said. "As many senses as you can engage while learning is better."

Making the models can translate into decreased wait times for surgeries. The center's staff can get something printed in a matter of hours rather than the weeks it would take if they had to contract the work out. That's extremely helpful in a case that involves something that needs quick treatment, like crushed facial bones from a car crash.

Chen says that without 3D printing, his job would be a lot more difficult: he likens it to having an impression made of his teeth before getting braces as a teenager. Now, orthodontists use a 3D scanner to do the same work.

"It's getting applied everywhere, and we're just trying to push the limits of how we can apply it in the medical surgical space," he said, adding that 3D printing for the medical surgical space is relatively new, so not much has been established or written about it. "There's no limits. We're just kind of limited by our own creativity."

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