Targeted Muscle Reinnervation Study (TMR)

After an amputation, patients often experience pain, both from the cut nerves themselves as well as perceived pain from a 'missing' limb. A technique has been developed to regenerate the cut nerve so that it doesn't cause pain. The technique includes sewing the nerve into another nerve so that it continues to function. This technique, called targeted muscle reinnervation, can reduce the postoperative pain amputee patients experience. Targeted muscle reinnervation (TMR) has shown promising success in the reduction of neuroma and phantom limb pain following extremity amputation. TMR was originally designed to allow for regenerative neurotization of end target muscle for the purpose of utilizing myoelectric prosthesis for amputees. While these indications have been successful, it has been the secondary outcome of reduction in neuroma and phantom limb pain that have led to significant improvements in patient outcomes. In the United States there are 200,000 amputations every year, and 1.6 million Americans living as amputees. Despite the technical success of the procedures, over 75% of patients will experience neuroma pain, and 85% will experience phantom limb pain. In addition, this pain limits the postoperative ambulation of many patients leading to a 75% 5-year mortality rate for patients who undergo lower extremity amputation in the US.3 TMR has shown promising clinical results in addressing phantom limb and neuroma pain. In pooled data it showed that patients who underwent TMR had residual limb pain of 0% and phantom limb pain of 7%. In a larger comparative study of 489 patients, patients who underwent TMR had phantom limb pain scores with an average of 1, compared to an average of 5 for control amputees. The TMR patients also had an average residual limb pain of 1, compared to an average of 4 for controls. Yet despite these promising outcomes, questions with TMR still remain. In the Valerio study, the largest study to date, all patients were grouped together regardless of the reason for amputation. While the percentage of patients undergoing amputation for cancer, infection, ischemia, trauma, or other, was reported, there was no comparison of outcomes in these groups. In a new study, the benefits of TMR have been shown to hold in highly comorbid patients presenting to a level 1 trauma center. Given the outcomes of TMR in these studies, there seems to be strong evidence to encourage the procedure, yet no study has yet to randomize patients to measure the true clinical outcome in a trauma population.