Targeted Muscle Reinnervation For Post-amputation Pain And Prosthetic Function: A Systematic Review
Amanda L. Chow, B.A.1, Waverley Y. He, B.A.2, Wilmina N. Landford, M.D.2, Jaimie T. Shores, M.D.2.
1Rutgers New Jersey Medical School, Newark, NJ, USA, 2The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
PURPOSE: Targeted muscle reinnervation (TMR) is a surgical technique where transected nerves from amputated limbs which no longer possess terminal targets for innervation are redirected via nerve transfer to new motor targets. TMR was originally developed to enhance prosthetic control following amputations; however, its dual ability to manage post-amputation pain has gained popularity in recent years. Nevertheless, the development of standard assessment tools for evaluating pain and prosthetic function pre- and post-amputation has yet to be established. The aim of our systematic review was to identify tools used to assess pain and prosthetic function following TMR and to establish a standardized method of measuring outcomes in future TMR studies.
METHODS: A systematic search was conducted according to PRISMA guidelines. PubMed, EMBASE, Cochrane, Web of Science, and Scopus were queried using keywords including "targeted muscle reinnervation", "amputation", and "extremity". Randomized clinical trials, cohort studies, case-control studies, case series and reports published in English that evaluated pain or prosthetic function outcomes of TMR were included. Two independent reviewers completed screening and data extraction, and studies describing duplicated patient populations were identified. Methodological quality was evaluated using the Newcastle-Ottawa Scale and Cochrane Risk of Bias tool for non-randomized and randomized studies, respectively.
RESULTS: A total of 476 articles published between 2005-2019 were identified for screening. Title and abstract screening identified 62 studies for full-text screening, of which 16 articles met inclusion criteria. Overall, 253 unique patients underwent TMR to prevent or treat post-amputation pain, improve prosthetic function, or both. One hundred (39.53%) patients were male, 40 (15.81%) female, and 113 (44.66%) had no recorded sex. The mean age was 40.1 (n=99, 39.13%). The 16 studies included for qualitative analysis were grouped based on the primary outcomes evaluated. Ten studies assessed pain and 7 assessed prosthetic function pre- and post-TMR. Three assessment tools were used to analyze the frequency and intensity of neuroma and phantom limb pain pre- and post-TMR including Patient-Reported Outcomes Measurement Information System (PROMIS) (5 studies), numerical rating scale (3 studies), and visual analog scale (3 studies). Among these, PROMIS was the most commonly used tool and demonstrated that patients who underwent TMR had a greater decrease in pain scores in the first postoperative year compared to patients who did not undergo TMR or underwent standard neuroma excision treatment. Nine assessment tools were used to evaluate prosthetic function following TMR, with the most commonly used tools being box-and-block test (5 studies), clothes-pin relocation test (4 studies), and amputee mobility predictor (3 studies). Of the 5 studies evaluating prosthetic function using box-and-block test, 4 demonstrated improved prosthetic function following TMR.
CONCLUSION: Overall, the most frequently used assessment tools for evaluating pain and prosthetic function following TMR were PROMIS and box-and-block test. While early results are encouraging, the clinical impact of TMR on post-amputation pain and prosthetic function remains unclear. Furthermore, several of these studies consisted of case series or reports. Therefore, we recommend more prospective studies that evaluate pain and prosthetic function while using outcomes measures such as PROMIS and box-and-block test.
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