SLR - December 2021 - Elizabeth A. Ansert
Reference: Chang, B. L., Mondshine, J., Attinger, C. E., & Kleiber, G. M. (2021). Targeted Muscle Reinnervation Improves Pain and Ambulation Outcomes in Highly Comorbid Amputees. Plastic and reconstructive surgery, 148(2), 376-386.Level of Evidence: Level III
Scientific Literature Review
Reviewed By: Elizabeth A. Ansert, DPM
Residency Program: Saint Vincent Hospital – Worcester, MA
Podiatric Relevance: Over 1 million amputations are performed worldwide with 200,000 involving a lower extremity amputation. Many of the amputations stem from a wide range of causes, such as diabetic foot infections, vascular disease, trauma, cancer, and many more. However, about 75 percent of amputees experience chronic limb pain and a phantom limb phenomenon after the surgery. This not only lowers quality of life but increases mortality. The pain is said to be multifactorial, but many theories involve some component of neuroma pain after amputation due to scar formation. Targeted muscle reinnervation has been recently studied as a way to help amputees reduce or completely relieve the pain experienced by amputations.
Methods: Authors conducted a retrospective, non-randomized cohort study of 200 patients. One hundred patients had below-the-knee amputations prior to a policy change at the institution. Their amputation was performed with traction neurectomy and muscle implantation of all identified nerves. A policy for patients to undergo primary targeted muscle reinnervation was then implemented, and 100 patients who received targeted muscle reinnervation were compared to those who did not. All surgeries were performed by the same surgeon in the same institution with consistent technique. A two-way t-test, two proportion z test, and analysis of variance were used for statistical analysis.
Results: Sixty-seven percent of patients were undergoing amputation for infection of a wound. 15 percent were failed reconstructions, 10 percent had ischemic pain without wounds, and 8 percent had infected hardware. Seventeen different comorbidities were found among the cohort and the average age at amputation was 59.7 years. Seventy percent male and 30 percent female. Sixteen percent were active smokers. No statistically significant differences between compared groups were found except follow up time. The targeted muscle reinnervation group had a 9.6-month follow-up compared to 18.5 months in the nontargeted group.
Seventy-one percent of patients who had targeted muscle reinnervation were pain free at their time to follow up, but only 36 percent of patients who did not have targeted muscle reinnervation were pain free. This was statistically significant. Of the patients that had pain in the targeted muscle reinnervation group, the average was 3.2/10. Patients without targeted muscle reinnervation had an average pain score of 5.2/10, which was a significant difference. Fourteen percent of targeted muscle reinnervation patients had residual limb pain, compared to 57 percent in the nontargeted group. Nineteen percent of targeted patients had phantom limb pain, compared to 47 percent in those without. Six percent of targeted patients had opioid use at their one-month follow-up, compared to 24 percent in the nontargeted group. 90.9 percent of targeted patients were ambulatory at their most recent follow up, compared to 70 percent in the nontargeted group.
Conclusions: This is one of the first studies to examine targeted muscle reinnervation in patients with comorbidities who have amputations due to infection or ischemia. The targeted muscle reinnervation group had significantly lower pain, less opioid use, and higher ambulation rates compared to the group that did not. Targeted muscle reinnervation is a safe and effective way to reduce pain in medically complex patients who undergo amputation.