A new type of surgery can help amputees control the remaining muscles and sense where their “phantom” limb is in space.
That should mean better control of prosthetic limbs, as well as less pain for patients, according to a study of a new procedure.
Researchers at the Massachusetts Institute of Technology (MIT) said most amputations break muscle pairs that control affected joints, such as elbows or wrists.
But reconnecting these pairs allows them to maintain their normal push-pull connection, providing amputees with better sensory feedback.
The study included 15 amputees who received a new procedure – an agonist-antagonist myoneural interface (AMI) – for below-knee amputations and seven patients who had traditional amputations.
The researchers measured the precision of movement in the ankle and foot joint after amputation.
Patients in the first group were able to control their muscles more precisely, also saying that they felt greater freedom of movement and less pain in the affected limb.
During surgery, two sets of muscles are reconnected to this group – the muscles that control the ankle and the muscles that control the subtalar joint – allowing the sole to tilt.
Shriya Srinivasan, lead author of the study, said: “Both our study and previous studies show that the better patients can move their muscles dynamically, the more control they will have.
“The better a person can move the muscles that move the phantom joint, for example, the more capable they are of using their dentures.”
Another version of surgery is being developed for other types of amputations, including above the knee and above and below the elbow.
Researchers have also developed a version that can be used for people who have already had a traditional amputation.
This involves grafting small sections of muscle that serve as agonist and antagonist muscles of the amputated joint. It is called regenerative AMI.
The study was published in the Proceedings of the National Academy of Sciences.