Dec 1, 2017 | By David

Hardly a day goes by without another 3D printing breakthrough in the field of prosthetics, and while the majority of these are intended to replace or repair limbs or other major parts of the body, the latest development is focused on a smaller but equally important part - the ear. A team of researchers in Maryland have pioneered a technique that makes use of 3D printing technology in order to substitute damaged parts of the middle ear with artificial equivalents, with huge potential for treating hearing loss and other related problems.

(3D printed middle-ear prosthetic)

In a healthy patient, hearing works partly through the transmission of vibrations from the ear drum to the cochlea, which is the sensory organ of hearing. These vibrations are transmitted via three tiny bones in the middle ear, which are known as ossicles. This 3D printing project was intended as a innovative solution to treat ossicular conductive hearing loss, which occurs when the ossicles are damaged because of physical trauma or bacterial infection, amongst other reasons. Conductive hearing loss is often treated through surgical reconstruction, which makes use of prostheses that are made from stainless steel struts or ceramic cups. The surgery generally involves tailoring a unique prosthesis for each individual patient in the operating room, and it is plagued by high failure rates.

"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 author Jeffrey D. Hirsch, M.D., assistant professor of radiology at the University of Maryland School of Medicine (UMSOM) in Baltimore. "If you could custom-design a prosthesis with a more exact fit, then the procedure should have a higher rate of success."

Hirsch and his team’s groundbreaking project has gone some way towards permanently solving the problem of middle ear prosthetics not fitting correctly into a patient’s ear, which has been the main cause of failure for surgical procedures aimed at fixing the hearing of patients with damaged middle ears. Like their forebears across the medical world who benefitted from the growing accessibility of 3D printing, they made use of CT scans that were converted into digital 3D models, which could then be sent to a 3D printer for direct manufacturing.

They captured scans of the middle ear bones taken from three cadavers, and used an affordable, commercially available SLA machine to produce the 3D printed replicas. Four surgeons were then asked to match the prosthetic bone to the original middle ear section, and they were all able to successfully complete this macabre jigsaw. The chances of this happening randomly, according to Hirsch, are around 1 in 1, 296. This suggests the incredible level of accuracy that is now possible with their 3D printed ear prosthetic technique.

(size comparison)

Now the problem of getting a correct fit has been provisionally solved, the next stage could be to explore 3D bio-printing techniques, which could enable the production of bio-compatible prostheses from human stem cells. These advanced devices could be incorporated even more naturally and effectively into a patient’s ear, with significantly improved durability and longevity, perhaps being the only prosthetic that a patient would ever need. "Instead of making the middle ear prosthesis solid, you could perforate it to be a lattice that allows stem cells to grow onto it," Dr. Hirsch said. "The stem cells would mature into bone and become a permanent fix for patients with hearing loss."

The results of this groundbreaking project were recently presented at the annual meeting of the Radiological Society of North America (RSNA). The study was led by Hirsch and co-authored with David Eisenman, M.D., and Richard Vincent, M.D.



Posted in 3D Printing Application



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