Targeted Muscle Reinnervation (TMR)

Nerve injuries can occur due to a variety of reasons including trauma, surgery (including mastectomy), and amputation. Damaged nerves may form neuromas, which are a painful ball-shaped growths at the end of an injured nerve.

Targeted muscle reinnervation (TMR) is a technique developed by Drs. Todd Kuiken and Greg Dumanian at Northwestern University in the early 2000s for patients with amputations. By transferring the nerves that had been cut to perform an amputation into nearby muscles, the muscles act as signal amplifiers. These amplified signals then could be detected to permit improved control of advanced myoelectric prostheses. For individuals who have access to these advanced prostheses for upper extremity amputations (shoulder disarticulation, transhumeral, or transradial), TMR can be performed to increase the number of myosites for control of their myoelectric prostheses.

Serendipitously, Drs. Kuiken and Dumanian recognized that patients who underwent TMR had decreased rates of post-amputation phantom limb pain and neuroma pain. This observation has been confirmed in numerous additional studies. TMR or a related technique known as RPNI is now performed at the time of amputation at many institutions to reduce phantom limb pain and neuroma pain and to increase quality of life for amputees. For individuals who already have undergone an amputation, TMR remains effective for treatment of established post-amputation phantom limb pain and neuroma pain.

Any patient undergoing an amputation is a candidate for evaluation for TMR or RPNI. For patients who already have undergone an amputation and have established phantom limb pain or neuroma pain, they should be evaluated for TMR or RPNI. This often includes a physical examination to identify sites of neuromas and nerve blocks performed with an injection of local anesthetic. This involves the injection of a local anesthetic near the affected nerve or nerves. If an individual experiences significant pain relief following the nerve block, it may indicate that TMR could be a beneficial treatment option for neuroma-related pain.

For patients interested in TMR to enhance control of their myoelectric prostheses, they should establish a relationship with a prosthetist experienced in working with advanced prosthetic devices. The prosthetist will play a vital role in the patient's journey, ensuring proper fit and function of the prosthesis and guiding the patient through the process of learning to use their new device effectively.

TMR surgery is designed to alleviate pain and/or enhance the function of myoelectric prostheses for amputees. The primary goal of the surgery is to transfer the severed nerves from the amputation site to nearby muscles, enabling these muscles to act as signal amplifiers and improve prosthetic control.

Before the surgery, the surgeon will carefully plan the procedure by identifying the most suitable muscles for nerve transfers. The choice of muscles depends on the patient's specific anatomy, the location of the amputation, and the desired functional outcomes. In some cases, the surgeon may opt to use a combination of TMR and RPNI techniques to achieve the best possible results.

During surgery, the surgeon will make an incision (or multiple incisions) to expose the severed nerves and the target muscles. Once the nerves and muscles are identified, the surgeon will carefully suture the nerves cut at the time of the amputation into nearby muscles, establishing a new connection that allows the muscles to receive and amplify the nerve signals. This process may involve multiple nerve transfers, depending on the complexity of the patient's case.

TMR surgery typically takes less than two hours to complete and is performed as an outpatient procedure.

TMR is generally a same-day outpatient procedure, meaning patients can return home after surgery. Post-operative pain is usually localized and improves quickly, although occasional nerve pain flare-ups may occur. Once the surgical wounds have fully healed, which typically occurs within six weeks post-operatively, patients can resume wearing their prosthesis.

As patients recover, they may work closely with a team of specialists, including physical therapists and prosthetists, to optimize the function of their myoelectric prosthesis if using one. This collaborative approach ensures the best possible outcomes for patients, helping them regain independence and improve their overall quality of life.

Be sure to see an experienced surgeon to treat this condition. Our fellowship-trained specialists at The Buncke Clinic in San Francisco treat patients using targeted muscle reinnervation (TMR) from across the Bay Area and Northern California. Contact us to schedule a consultation.

Below are links for third party resources

TMRnerve.com