Approved: Prosthetic Legs That Anchor Directly To The Bone

No longer just for Oscar the cat

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This prosthetic doesn’t go out on a limb, but into a limb.

The FDA has just approved leg prosthetics that anchor directly to the bone, which could change the lives of amputees who cannot use typical ball-and-socket prosthetics.

Most prosthetics require a cup-shaped socket to be fastened to an amputee’s residual limb, but some amputees don’t have enough limb left to use this method of attaching a prosthetic. The Osseoanchored Prosthesis for the Rehabilitation of Amputees (OPRA) device solves this issue by using fixtures that are implanted directly into the amputee’s bone, which allows them to attach a prosthetic to it, like a bionic K’Nex.

The device is surgically installed with two procedures. In the first procedure, a cylinder-shaped fixture is implanted directly into the remaining bone. The implant is made out of titanium so that the bone does not reject it. After about six months when the tissue has grown around the fixture, a rod is implanted that extends through the skin, which can be inserted and clasped to a prosthetic. The patient is then required to go through six months of training before being fitted with a customized prosthetic.

A 2014 study published in Physical Medicine and Rehabilitation found that amputees using the device reported increased mobility, comfort, and function. Amputees using this device also don’t have to worry about issues such as heat and chafing that prosthetic sockets give.

Although the device can be applied to arm, leg, and hand prosthetics, the FDA has limited its approval to adults who have had leg amputations above the knee.

“The OPRA device may help those with above-the-knee amputations who have had problems with rehabilitation and have not been able to benefit from available socket prostheses,” said William Maisel, acting director of the Office of Device Evaluation in the FDA’s Center for Devices and Radiological Health in a press release.

A major concern with bone-anchored prosthetics is the risk of infection. Stanmore Implants, a prosthetics company in the UK, got around this by modeling their prosthetics after the way deer antlers are attached. The device, called the Intraosseous Transcutaneous Amputation Prosthesis (ITAP), has pores to help soft tissue seal off the connection between the skin and bone, which reduces the chance of bacteria getting it. The device has been shown to be effective in both animals and humans, but has yet to be approved in the U.S.

Even though the U.S. is taking baby steps to approve more bone-anchored prosthetics, it is an exciting prospect for the future of bionic limbs.