A Titanium Arm From Hopkins Is Almost Better Than the Real Thing

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Photo via JHU APL
Photo via JHU APL

Johns Hopkins has made it their business to become a leader in the world of prosthetics, working to develop everything from a prosthetic eye to thought-controlled artificial limbs.

Now the surgeons over at Hopkins have developed a new technique that makes their prosthetics even more advanced. “It moves the whole field forward, and not just a small step,” Michael McLoughlin, chief engineer of the university’s Applied Physics Lab’s Research and Exploratory Development Department, told the Hopkins Hub. “I mean, it is a really big jump.”

Even as prosthetic limbs became increasingly advanced, the problem of how to connect the fake limb with the residual one always posed a problem. The socket that joined the two limbs had to fit perfectly without being chafe-y or loose. “The socket is paramount over all other components,” amputee Rick Riley told Popular Mechanics a few years ago. “If the leg hurts you, I don’t care how technologically advanced all the components are, the amputee will have a hard time wearing it day to day.”

The new technique developed at Hopkins involves attaching the new titanium prosthetic directly to the remaining limb, was tested out on Johnny Matheny, a man who lost his arm to cancer several years ago. The surgeons used targeted muscle reinnervation in order to attach nerves that once connected to his hands to his prosthetic arm instead. He also underwent a procedure called osseointegration. As the Hopkins Hub describes it,

first, a threaded titanium implant called a fixture is inserted into the marrow space of the bone of the residual limb; over time, the fixture becomes part of the bone. Several weeks after the first surgery, a titanium extension known as an abutment is attached to the fixture and brought out through the soft tissues and skin. The prosthesis can then be directly attached to the abutment.

According to Matheny, the difference was pretty much instantaneous: “Before, the only way I could put the prosthetic on was by this harness with suction and straps,” he said. “But now, with osseointegration, the implant does away with all that. It’s all natural now. Nothing is holding me down. Before, I had limited range; I couldn’t reach over my head and behind my back. Now, boom, that limitation is gone.”



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