Targeted Reinnervation as a Means to Treat Neuromas Associated With 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. The current standard surgical treatment for a neuroma is to cut if off and bury the nerve ending in a muscle, to provide cushioning when the neuroma grows back. Even though this is the best current treatment, it is not always successful. 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 plan to compare TMR versus the current standard surgical treatment for painful neuromas. We will measure the effectiveness of both surgeries using an internet-based amputee pain questionnaire. We will also use magnetic resolution imaging (MRI) to look at the nerves before and after surgery. We have received a grant to complete a 4 year study in four hospitals across the US, in around 200 patients, making this the largest neuroma study ever performed. We expect that TMR will be significantly more effective for neuroma pain than the standard treatment. This will change how patients with neuroma pain are treated and help thousands of patients with amputations.