Prosthetic legs usually fit to a person’s stump using a cup and straps. The skin isn’t made for such pressures, and the cup rarely fits perfectly. Sweat and swelling make it uncomfortable after a while, even if the day started well.
The FDA has just approved a potential solution. The OPRA (Osseoanchored Prostheses for the Rehabilitation of Amputees) is a leg that screws into the bones of the residual limb and can be attached and removed easily.
A metal cylinder is implanted into the central canal of the thigh bone and allowed to heal for six months. A second surgery adds a rod to the original cylinder, and this rod pokes out through the skin. This is where the prosthetic leg attaches.
An OPRA leg clicks into place with a bayonet-like mount. The OPRA site lists several advantages: The leg is always firmly attached, and it doesn’t chafe or cause pressure sores. Another advantage is easy attachment. A user can remove their leg to rest more comfortably, without having to worry about the time and effort it’ll take to put it back on. You could walk to the bathroom in the middle of the night, for example, instead of having to go on crutches.
The FDA says that clinical trials were mostly a success:
Study subjects reported increased prosthetic use, and improved mobility, comfort, function, and quality of life compared to the subjects’ own outcomes prior to the surgeries. The most common adverse event was infection.
OPRA limbs have been in use outside the U.S. for quite some time–the Osseointegration site says that the Australian government gave approval as far back as 1999. What’s taken the FDA so long? Concerns about infection, which is why the agency has only approved the devices for above-the-knee amputations.
The OPRA has also gotten a special designation called a HUD (Humanitarian Use Device). A HUD is a “medical device intended to benefit patients in the treatment or diagnosis of a disease or condition that affects or is manifested in fewer than 4,000 individuals in the United States per year.” The HUD designation has fewer restrictions than other designations, making it easier to get.
Femur-coupled protheses aren’t the only application either. The same technology has been used for arms and even fingers and thumbs. I wonder if the modular nature of the OPRA would let you attach more useful appendages as to fit the task at hand, when cooking or in the workshop for example. That could be pretty handy.