3D Printed Ear Bones Could Fix A Kind of Hearing Loss

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3D printing has become a tremendously useful adjunct in the field of medicine and is especially beneficial in making patient-tailored prosthetics. The relative ease of the technology in translating high-resolution digital images to precise 3D-reconstructions has made it an ideal tool for prosthetic medicine.

Now, to treat a particular kind of hearing loss that involves damaged ear bones, researchers from the University of Maryland have turned to 3D-printing in the hope that it could improve the success of currently available procedures.

Middle Ear Anatomy Credit: Wikimedia commons
Middle Ear Anatomy Credit: Wikimedia commons

The middle ear contains three tiny bones, also known as the ossicles – Malleus, Incus and Stapes. The function of these ossicles is to amplify and conduct sound vibrations from the outer ear to the fluid in the inner ear.

The middle ear contains three tiny bones known as the ossiclesmalleusincus, and stapes.

Trauma or infection of these tiny bones can lead to a certain type of deafness called ossicular conductive hearing loss. The ossicle that is usually damaged is the middle linking bone or the incus.

Treatment involves an established surgical operation called ossiculoplasty, where the damaged ear bone is replaced by a steel-ceramic prosthetic fabricated in the operation room.

However, the current rate of failure for the procedure is as high as 25 to 50% of the operated cases, which could be due to misfit of the fabricated prostheses in the patient’s ear.

“The ossicles are very small structures, and one reason the surgery has a high failure rate is thought to be due to incorrect sizing of the prostheses,” said study co-author Dr. Jeffrey Hirsch.

“If you could custom-design prosthesis with a more exact fit, then the procedure should have a higher rate of success.”

The team of researchers removed the middle ear bones from three cadavers and took CT scans of the cadaver skulls. They then reconstructed the incus from the missing gaps in the images of the scan.

The three fabricated prostheses were then given to four surgeons, who were asked to fit them into the right ears. The surgeons independently matched the printed ear bones to the correct ears, despite the fact that the bones varied only slightly in angles and dimensions.

“They said it wasn’t that hard to figure out,” said Jeffrey Hirsch.

“It was almost like a Goldilocks sort of thing – this prosthesis was too tight in this ear and too loose in this ear, but in this ear it’s just right.”

The research was published in the journal 3D Printing in Medicine.

The authors also highlighted possible limitations of the study that need to be addressed in the future.

Rendering of prosthesis in place (University of Maryland Medical Center)
Rendering of prosthesis in place (University of Maryland Medical Center)

In the current study, CT scans were taken of cadaver skulls that had been cut down to only a part of the surrounding bone, so as to improve the quality of the scans. Future research will need to find how an intact skull might mask image features needed for prosthetic reconstructions.

Also, the bones will need to be bio-printed, or fabricated from biocompatible materials, before it can be approved as a viable option for treatment of hearing loss.

However, with the advances that have been made in printing ear cartilage, synthetic skin, organs such as the liver and even blood vessels, it may not be very long before custom-printed ear bones are available.

“I really think that 3D printing is going to become a standard of care whenever there’s a need for a prosthesis, whether it be a joint or a middle ear,” said Hirsch.

“The standard of care will not be an off-the-shelf component, but a component that’s custom designed for that specific patient.”

Original article can be accessed here.