Rerouting Nerves During Amputation Reduces Phantom Limb Pain

A novel surgical procedure developed for advanced prosthetics can prevent or reduce debilitating phantom limb and stump pain in amputees, according to a new study.

Researchers at Ohio State University (OSU; Columbus, USA) conducted a study in 22 patients in order to evaluate the results of primary targeted muscle reinnervation (TMR) for below-the-knee amputations. The procedure involves rerouting the severed motor nerves by surgically transferring them to the motor points of the denervated target muscles, which, after reinnervation, can contract in response to neural control signals intended for the missing limb. The operation of the prosthesis thus occurs in response to attempts to move the missing limb, making control easier and more intuitive.

All subjects denied neuroma pain following amputation. Each patient was followed on an outpatient basis for one year to evaluate early symptoms of neuroma or phantom limb pain, patient satisfaction, and functionality. The researchers also found that over the course of three years, none of the patients developed symptomatic neuromas, and only 13% of those who received primary TMR reported pain six months later. In addition, by creating the additional control sites, TMR eliminated the need to switch the prosthesis between different control modes. The study was published in the January 2019 issue of Plastic and Reconstructive Surgery.

“A significant amount of pain in amputees is caused by disorganized nerve endings, i.e. symptomatic neuromas, in the residual limb. They form when nerves are severed and not addressed, thus they have nowhere to go,” said senior author Ian Valerio, MD, of the department of plastic and reconstructive surgery at OSU. “Attaching those cut nerve endings to motor nerves in a nearby muscle allows the body to re-establish its neural circuitry. This alleviates phantom and residual limb pain by giving those severed nerves somewhere to go and something to do.”

“TMR allows for more individual muscle unit firings through the patient's thoughts. It provides for better intuitive control, resulting in more refined functional movements and more degrees of motion by an advanced prosthetic,” concluded lead author J. Byers Bowen, MD, of OSU. “When done at the time of initial amputation, there is minimal health risk, and recovery is similar to that of traditional amputation surgery.”

Approximately 25% of major limb amputees will develop chronic localized symptomatic neuromas and phantom limb pain in the residual stump or limb. Previous studies show that secondary targeted reinnervation successfully treats and, in some cases, resolves peripheral neuropathy and phantom limb pain in patients who have undergone a previous amputation.

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