April 15, 2013: the day of the Boston Marathon bombing. Tragically, some were killed and many were injured. For many, their lives would never be the same as they navigate this world as an amputee. These individuals had to go through many hardships including experiencing phantom limb pain, where pain is felt in areas where a limb has been amputated, as well as amputation site pain. In the article “Targeted Muscle Reinnervation Treats Neuroma and Phantom Pain in Major Limb Amputees”, Dr. Gregory Dumanian et al. discovered a new surgical way to treat neuroma that would also decrease phantom limb pain in these individuals. Instead of performing a standard treatment for neuroma where the tumor is excised then placed back into the muscle, a new way, called Targeted Muscle Reinnervation (TMR) was created. In this surgical procedure, an incision is made and the neuroma is removed. The next steps in TMR require a healthy neuron to be cut and connected with the old neuron that previously had the tumor. It is then buried deep inside of the muscle (Dumanian et al. 2019). This connection allows for the regeneration and growth of the neuron and improves both amputation site pain as well as phantom limb pain.
Although the pain of these amputees was greatly alleviated, it did not play a role in helping them explore life without a limb. In the article “New surgery may enable better control of prosthetic limbs” by Anne Trafton, researchers of MIT and Harvard Medical School teamed up and discovered agonist-antagonist myoneural interface (AMI), a new surgical way to help amputees gain better control over their residual muscles at the amputation site and even allow them to receive sensory feedback from these areas. Not only does AMI allow patients to experience more freedom in their movement, but it also reduces pain and restores sensation in the area (Trafton). Trafton goes on to give an example of an agonist-antagonist pair: the biceps and triceps. “When you bend your elbow, the biceps muscle contracts, causing the triceps to stretch, and that stretch sends sensory information back to the brain” (Trafton). Standard surgical amputations restrict the movement of these agonist-antagonist muscles which furthermore restrict sensory feedback and makes it more difficult for amputees to feel and control prosthetics. AMI connects the two muscles and allows them to communicate rather than completely severing the connection as seen in a standard surgical operation. Results showed that, when compared to those who have undergone standard amputations, AMI patients showed very similar activation in both the amputated and intact, healthy limb alike (Trafton) showing increased sensory feedback in patients who have undergone AMI surgery rather than standard amputation surgery. Although the experiment was not specifically designed to study the patients’ freedom of movement after the AMI operation, the majority of participants reported having a better perception of where their amputated limb was in space. These studies have increased the opportunities of those who have suffered from an amputation, allowing them to feel more connected with their bodies in a new way.
Dumanian, G. A., Potter, B. K., Mioton, L. M., Ko, J. H., Cheesborough, J. E., Souza, J. M., Ertl, W. J., Tintle, S. M., Nanos, G. P., Valerio, I. L., Kuiken, T. A., Apkarian, A. V., Porter, K., & Jordan, S. W. (2019). Targeted Muscle Reinnervation Treats Neuroma and Phantom Pain in Major Limb Amputees: A Randomized Clinical Trial. Annals of surgery, 270(2), 238–246. https://doi.org/10.1097/SLA.000000000000308
Trafton, A. (2021). New surgery may enable better control of prosthetic limbs: Reconnecting muscle pairs during amputation gives patients more sensory feedback form the limb. MIT News. https://news.mit.edu/2021/surgery-control-prosthetic-limbs-0215
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