https://www.nature.com/articles/d41586-024-02157-3A new neural interface connects a bionic limb to nerve endings in the thigh, allowing the limb to be controlled by the brain. The new device, which is described today in Nature Medicine, could help people with lower-leg amputations feel as if their prosthesis is part of them. >"When you ask a patient 'What is your body?' They don't normally include the prosthesis," says MIT biophysicist Hug Her, one of the lead authors on the study. The work is personal for him: he lost both his lower legs in a climbing accident. He says linking the brain to the prosthesis can make it feel more like part of someone's anatomy, which can have a positive emotional impact.Getting the neural interface hooked up to a prosthetic takes two steps. First, patients undergo surgery. Following a lower leg amputation, portions of shin and calf muscle still remain. The operation connects shin muscle, which contracts to make the ankle flex upward, to calf muscle, which counteracts this movement. The prosthetic can also be fitted at this point. Reattaching the remnants of these muscles can enable the prosthetic to move more dynamically. In step two, surface electrodes measure nerve activity from the brain to the calf and shin muscles, indicating an intention to move the lower leg. A small computer in the bionic leg decodes those nerve signals and moves the leg accordingly, allowing the patient to move the limb more naturally. "If you have intact biological limbs, you can walk up and down steps, for example, and not even think about it. It's involuntary," says Her. "That's the case with our patients, but their limb is made of titanium and silicone." The authors compared the mobility of seven patients using a neural interface with that of patients who had not received the surgery. Patients using the neural interface could walk 41% faster and climb sloped surfaces and steps. They could also dodge obstacles more nimbly and had better balance.
