Traumatic injury, tumours, and different types of illness can damage the ossicles of the middle ear – the smallest bones in the human body – which transmit vibrations from the ear drum to the liquid located in the inner ear itself.
Resultant hearing impairment is currently treated surgically by replacing the bones with tiny prostheses, which leads to failure in as many as 25 to 50 percent of cases.
To address this, researchers from the University of Maryland Medical Centre had employed 3D printing technology to manufacture custom-fitted ear bones which they hope will eventually be used in humans.
Based on the images, the researchers then fashioned a set of tiny prostheses, which varied by mere fractions of a millimetre, and had four different surgeons guess which one went in which ear.
“They said it wasn’t that hard to figure out,” said lead author on the study Jeffrey Hirsch, Professor of Radiology at Maryland. “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.”
Discussing their findings in a paper, recently published in the journal 3D Printing in Medicine, the authors hope to run experiments with animal models and human cadavers in the foreseeable future.
The main difficulties will be designing prostheses based on actual patients (the skulls used in the study included only a part of the surrounding bone, making the imaging process less complicated), and finding biocompatible materials to minimise the risk of rejection.
Researchers around the world, including the University of Maryland, have been experimenting with 3D printing technologies to produce ear parts, which could eventually form an integral part of regenerative medicine.
“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.”