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Microtia team embraces 3-D printing to improve ear surgeries

To rebuild ears of children affected by microtia, a rare congenital ear deformity, Stanford physician-researchers have turned to 3-D printing.

One in 5,000 children is born with microtia, a condition whose Latin name translates to “little ear.” Children with microtia have malformed outer ears, or no outer ear at all, and often have missing ear canals. The condition can cause hearing loss, as well as feelings of embarrassment or shame for the child and their family.

Stanford otolaryngologists Mai Thy Truong, MD, and Kay Chang, MD, perform microtia repair surgeries and work as part of the Microtia & Ear Canal Atresia Team at Lucile Packard Children's Hospital Stanford.

Building accurate models to guide the surgery is a key step. Traditionally, ear models have been crafted from flat images. A picture is taken of the child's intact ear and printed out. In addition, an outline of the ear is traced onto X-ray film and flipped to create a reverse image. Surgeons then craft 3-D ears from these two-dimensional images, matching them to the existing ear as closely as possible.

Now, Truong and her colleagues are developing a new method to build ear models using 3-D printing. They adapted their techniques from those already used for other craniofacial procedures, like rebuilding mandibles and skulls. The models are informed by scans that were taken to evaluate the ear canal, which the surgeons repurpose to build the models.

Truong says this technology foreshadows the future of microtia treatment.

“We’ve learned the nuances to 3-D printing and how to really make a useful model, depending on the patient, and how to use the 3-D software to our advantage with surgical planning,” she said. “What I’m learning in designing these models is what we’ll be using if there ever is a day we can 3-D print ears.”

Truong and Chang employ the Firmin technique — Truong has spent months training with its developer, Francoise Firmin, MD, in France, who is shown in the photo above, with Truong and Chang.

“The reason we targeted this surgeon and this technique is because the outcomes are the best we’ve seen,” Truong said.

The Firmin technique is a type of rib cartilage graft surgical reconstruction. Rather than using synthetic materials, Truong and Chang use cartilage from the patient’s own ribcage to build a new ear. This results in a sturdy implant that has a lower risk of being rejected and is intended to last lifetime. If the child needs ear canal surgery as well, this procedure can be incorporated into the process, Truong said.

"We integrate plans for hearing amplification, educating parents on the latest in hearing implants, and guide them through hearing restorative surgeries," said Truong. "This comprehensive plan along with the auricular reconstruction is what makes us special."

The change they see in their patients after surgery is rewarding, she added:

One of my favorite patients started out very shy, had long hair, never showed anyone her ear. We have to cut the hair as part of the stages of surgery, and at her follow-up six months later, she had still shaved her hair around her ear. She loved it – she loved showing her ear off and even said she wanted to be a model. That was the kind of self-confidence she had. It was just awesome.

Previously: A serendipitous save that changed treatment of the most common tumor of infancy and Hearing clearly helped Down syndrome toddler develop on track
Photo courtesy of Mai Thy Truong

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