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Targeted Muscle Reinnervation (TMR) Helping Restore Function & Relieve Pain for Upper-and lower-extremity Amputees

Advance With MUSC Health
January 03, 2022
Dr. Dane Daley

Upper- and lower-extremity amputations can lead to chronic pain, difficulty with activities of daily living, and a constant search for relief through pain management, physical therapy, and/or surgery.

MUSC Health is one of several medical centers in the Southeast that offers targeted muscle reinnervation (TMR), a surgical procedure that helps to relieve neuroma-based pain and, to a lesser degree, phantom limb pain in upper and lower extremity amputees.

“While TMR is not a novel treatment, it has been refined and better understood over the past decade,” says Dr. Dane Daley, an MUSC assistant professor and orthopedic hand surgeon who performs TMR for upper- and lower- extremity amputees.

After an extremity amputation, the severed nerves are no longer connected to their distal muscles. With TMR, those severed nerves are spliced into a more proximal muscle that is still present in the amputated extremity, thus giving that nerve a new purpose.

The severed nerve then regenerates into that muscle, and if the procedure is successful, prevents the formation of a painful neuroma. This nerve, after appropriate healing time, can innervate its new target, causing the muscle to contract. This regeneration process can take months to over a year to work.

“Simply put, TMR is a way to repurpose a nerve that is no longer connected to a muscle and give it a new target muscle to innervate,” Dr. Daley says. “It essentially tricks the brain by rewiring patients’ nerves.”

In the right patient, TMR can help to restore function, Dr. Daley says. TMR has been shown to significantly decrease stump pain, remove symptomatic neuromas, reduce, if not completely eliminate, pain medication, as well as increase prosthetic wear.

The surgery, which is an outpatient same-day procedure, can be performed simultaneously with a scheduled amputation or years after an amputation. “There’s no specific timeframe. The majority of my cases are patients who are unable to wear their prosthetic because of painful neuromas or “hot spots,” Daley says.

TMR is a technically challenging microsurgery that can take from two to three hours to complete. “We’re working around the major neurovascular structures in the limbs, and the technical part is identifying an appropriate target to use,” Dr. Daley says. “A target isn’t just a nearby muscle; I have to find the nerve branch innervating a viable muscle. That nerve branch is then cut and spliced together with the previously amputated nerve.”

Outcomes are very good in the correct patient population, including patients who have suffered a traumatic amputation, severe disabling extremity injuries, and certain patients with upper- and lower-extremity soft-tissue sarcoma.

Therapy plays a huge role in recovery and, along with TMR, affords the patient the ability to lessen pain medications and to break the pain management cycle, Dr. Daley says.

“The change is enormous, especially for my below-knee amputees who often cannot use their prosthetic or bear weight on their stumps because of the symptomatic neuromas,” he says. “The ability to wear a prosthetic and ambulate improves their quality of life.”

Dr. Daley says successful patient outcomes are the result of a team effort.

“MUSC Health has an excellent multidisciplinary team of dedicated clinicians and therapists, as well as a strong referral network with psychiatrists and prosthetic teams to get people ambulatory and functional again.”

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Keywords: Physical Therapy, Orthopaedics, Surgery