It's a medical breakthrough, thanks to a piece of technology most people are using to make plastic toys. Using a 3D printer, a group of researchers just tested this lifesaving device on three very sick infants.
Researchers at the University of Michigan have 3D-printed a device to keep infants' airways from collapsing. Designed to treat a rare paediatric disease, the airway splints are custom-printed to fit each patient, and they expand along with the child's growing airway and eventually reabsorb into the body.
A Rare but Deadly Disease
This 3D-printed medical device is a badly-needed treatment for a disease most people have never heard of. Tracheobronchomalacia only affects one child in every 2000, but for its rare patients, it can be life-threatening. The disease weakens the walls of the trachea and the bronchii, the branching passages that carry air to and from the lungs. When an affected infant tries to breathe, the airway can collapse.
Children with tracheobronchomalacia spend lots of time in the hospital during their first few years of life, and those with really severe cases may be stuck in intensive care units for several months at a time, sedated and hooked up to an artificial respirator.
So far, the best solution for these children is a splint that wraps around the outside of the airway. Surgeons suture it in place, so that it can act as an exterior support structure for the airway walls. "The airway is suspended from it like a tent on a framework," said Robert J. Morrison, Research Fellow and Resident Surgeon of Otolaryngology, Head and Neck Surgery at the University of Michigan.
The splints available now are expensive, they tend to "migrate", or move, and they have to be replaced as the patient grows. Morrison and his colleagues turned to 3D printing for a solution. They developed an airway splint that is open on one side, so that it can open wider to make room for expansion as the child's airway grows. "The analogy for that would be like opening a hair clip or something like that," explained Associate Professor of Pediatric Otolaryngology Glenn Green.
The polymer material of the splints is designed to gradually break down and pass out of the body after about 3.5 years, because most tracheobronchomalacia patients develop stronger airways on their own by about age three; the challenge for doctors and caregivers is to keep the children alive that long. "If the children are doing well at age 3 we would expect them to do well for the rest of their lives. If the airway has enough structural integrity at that point and is large enough at age 3 we would expect that they would not have trouble for the rest of their lives," said Green.
From Prototyping to Patient Care
This rare childhood illness, say researchers, is a good example of how medicine can use 3D printing. The technology, originally conceived for producing prototypes of designs, could also print uncommon medical devices like this one, for which most companies see little commercial demand. "Cases like tracheobronchomalacia that may not have been a large enough market for a medical device company to invest in the manufacturing, you can do now do that," said Scott Hollister, Professor of Biomedical Engineering and Mechanical Engineering and Surgery.
"Machines that used to cost hundreds of thousands of dollars previously — now you see them on Amazon for $US500-$US1000," he said. The cost of the materials for each splint is about $US10.
According to Hollister, it takes about three days to create an airway splint for a new patient. Doctors use CT scans to create a 3D digital model of the patient's airway, and then they load the model into a computer program, which measures 10 variables in the airway — such as length, diameter, and wall thickness — and then generates a digital version of an airway splint, custom designed to fit the patient's airway.
Doctors check the digital model of the airway splint to make sure it fits the digital model of the airway, and they run a simulation to see how the splint will expand as the airway grows. If everything checks out, they create physical copies of both items on a 3D printer. Surgeons can use a physical 3D model of the patient's airway and the splint to practice the surgery before operating on the real patient, and it gives doctors one more chance to be sure that everything fits, part of a process they call design control.
The fact that each splint is a custom project may make it challenging to regulate 3D-printed medical devices of this kind. It is difficult to regulate a device whose structure is different every time it's made, since regulations are meant to standardise. The University of Michigan research team suggests design control as a possible starting point.
First Patients are Doing Fine
Just over three years after receiving the first 3D-printed airway splint, the team's first patient has an open, healthy airway, and two other children who received splints as part of the study also appear to have outgrown the disease successfully. When the doctors looked at the first patient's airway, the splint appeared to be in the process of being resorption by the patient's body, and the airway was strong and working normally on its own.
The 3D-printed splints haven't been approved for a clinical trial yet, but the FDA approved a special emergency use exemption for the three patients in the study, because their conditions were so desperate. In fact, researchers had begun talking to colleagues about their idea several years ago, and one member of the team remembered, "I got a call from one of the people I told this to and he said, 'know you are to ready to start a trial, but we've got someone here that needs it now. He will die.'"
For all three infants, the study was a last resort.
Now, researchers are working with the FDA to plan a clinical trial involving 30 patients with severe but less urgent cases, but they haven't set any dates.