Targeted Reinnervation for Neuromas as a Means to Improve Prosthesis Control in Major Limb Amputation

Loss of an arm or leg is a significant injury that affects a person's job prospects, personal relationships, and overall quality of life. Approximately 25% of all amputees will develop chronic local pain in the remaining part of their amputated limb. This pain is caused by neuromas- disorganized nerve endings and scar tissue that form when an injured nerve tries to heal. Every cut nerve will develop a neuroma unless the two ends of the nerve can be rejoined. With limb amputation, the nerves are cut and one end is lost with the limb, preventing the nerve from repairing itself. Instead, the cut nerve ending forms a painful neuroma. Chronic pain from neuromas is a major reason that amputees cannot wear or use their prostheses comfortably and increases their disability.

Even when a limb is amputated, the nerves that used to control that limb still carry messages from the brain. Those messages are intended to tell the muscles how or when to move the missing limb, but after amputation, these limb-control nerves are no longer connected to muscles. In 2002, researchers at Northwestern Memorial Hospital in conjunction with the Rehabilitation Institute of Chicago developed a new type of surgery called targeted muscle reinnervation (TMR). In TMR, limb-control nerves are transferred so that they can control new target muscles. The neuromas from the limb-control nerves are removed, then the small nerve that controls the target muscle is cut. The two nerves are joined together so that the limb-control nerve can then grow into, or reinnervate the target muscle. After TMR, when the person tries to move the missing limb, the target muscle contracts instead and these signals can be detected and used to control a prosthesis. TMR has now been done successfully almost 100 times worldwide. Interestingly, almost all of the patients who had painful neuromas before TMR had no neuroma pain after surgery. This result was investigated in laboratory studies - both rat and rabbit amputee neuromas were "cured" with TMR. We think that giving the cut nerve endings somewhere to go and something to do prevents a neuroma from forming.

We will measure the effectiveness of both surgeries using an internet-based amputee pain questionnaire. We expect that TMR will be more effective for neuroma pain and prosthesis control than the standard treatment. This will change how patients with neuroma pain are treated and help thousands of patients with amputations.

Inclusion criteria

• Adult, 18 years or older: the Patient Reported Outcomes Measurement Information System (PROMIS) questionnaire is not validated for pain-related evaluation in minors
• An upper limb amputation above the wrist with or without a residual limb or a lower limb amputation above the ankle with a residual limb
• A neuroma within the residual limb: defined as patient-reported chronic localized pain consistent with a physical exam that demonstrates that the pain is related to a cut nerve and excludes other causes. There must be a supporting Tinel's sign on physical exam, or localization of a neuroma by prior intervention (surgical or otherwise) to distinguish the pain from phantom limb pain or cold intolerance that are nonspecific signs of nerve damage that would not be affected by treatment of a neuroma
• English or Spanish speaking

Exclusion criteria

• Prior TR Surgery: these patients have already had a procedure to improve their prosthetic function and in these cases the nerves have been shortened. To perform a second TR procedure with the previously shortened nerves would require a significant proximal dissection and potentially greater soft tissue morbidity than the standard treatment.
• Cognitive impairment, due to TBI or other causes, sufficient to adversely affect understanding of or compliance with study requirements, ability to respond to questionnaires, or ability to give informed consent: The ability to understand and comply with requirements of the study is essential in order for the study to generate useable, reliable data. The ability to obtain relevant feedback through questionnaires is essential to this study.
• Pre-operative assessment that precludes the patient from being eligible for TR or control surgery due to technical surgical concerns.
• Significant other comorbidity: Any other medical issues or injuries that would preclude safe administration of anesthesia or surgical intervention.
• Participation in other ongoing studies related to neuropathic pain.