Post Operative Chronic Pain in Amputees

    For years, researchers have been attempting to truly understand the neurophysiology behind pot operative chronic pain in patient who had undergone limb amputations. Due to extenuating circumstances, amputation is often the last resort for patients in order to save their lives, but this may be at a heavier cost. Amputees often experience a phenomenon called "phantom limb pain", which refers to the pain felt by patients in the limb that is no longer there. Phantom limb pain has been known to be caused by a combination of factors such as overactive pain signals to the brain, plasticity in the brain's sensory map and recently attributed to trauma to the nerves, muscle and bone at the site of the amputation. A lot of these explanations are useful in understanding the reasons for the pain, but still ask the question of how we can help patients with their phantom limb pain. Groundbreaking insights have been made in recent years regarding this construct and possible surgical techniques to help these patients. 

    Using previous knowledge of muscle and nerve trauma being a main factor in postamputation pain, a surgical technique known as Targeted Muscle Reinnervation (TMR) was proposed by Dumanian et al. The reasoning behind this procedure is the knowledge that most chronic residual limb pain is caused by terminal neuromas, which are cut nerve endings at the site of the amputation which become encased in scar tissue. The TMR procedure attempts to remove terminal neuromas and attach fresh nerves to a nearby motor nerve in order to encourage reinnervated growth in the denervated muscle (Dumanian et al., 2019). The researchers used a randomized clinical trial with 28 amputees experiencing chronic pain who were then assigned the standard treatment, which is simple neuroma excision, or the TMR procedure. Resulting data showed an overall decrease is postoperative pain, neuroma size and patient function. Dumanian et al. emphasize the ability to integrate the TMR procedure into the initial amputation surgery to proactively aid with neuroma growth and pain. 

    Though the possible implications of TMR in aiding postamputation pain are revolutionary, there are limitations as to how far it can take us due to the interconnectivity between the physical neuromas and the cortical reorganization that takes place in the central nervous system. As explained earlier, the plasticity of the brain allows for cortical reorganization in the sensory map of the brain, which calls for a deeper level of understanding of the psychological implications of phantom limb pain. Research compiled by Aternali and Katz reviews different standard treatments for phantom limb pain, including TMR, transcranial magnetic stimulation, imaginal phantom limb exercises, mirror therapy, virtual and augmented reality, and desensitization and reprocessing therapy (Aternali & Katz, 2019). Each individual therapy or treatment provided respective benefits to the amputees in managing pain and improving their quality of life, however, they found that no one treatment significantly overpowers the other in terms of being consistently better than a control condition. 

    There are many limitations in understanding and successfully treating chronic phantom limb pain in amputees due to the interplay between physiology and psychology, and the underpowered sample sizes of amputees able to participate in studies. By using these respective studies, we can hopefully take aspects of the two distinct constructs of postoperative pain and develop a standard treatment to aid amputees with chronic pain. The pain cannot be decreased by ignoring either the psychological aspects nor the physiological aspects that cause the pain, so by breaking it down into smaller pieces, researchers can draw out the clinical implications. 

References:

Aternali, A., & Katz, J. (2019). Recent advances in understanding and managing phantom limb pain.    F1000Research, 8, F1000 Faculty Rev-1167. https://doi.org/10.12688/f1000research.19355.1

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.0000000000003088