Targeted Muscle Reinnervation at time of Below Knee Amputation: A Posterior Approach
Jeffrey N Gross, MD1, Sri Charan Kanthala, BS1, Cameron M Harmon, BS1, Aladdin H. Hassanein, MD, MMSc2, Rachel M Danforth, MD1, Erin L Weber, MD, PhD3, Anthony J Archual, MD1, Brian M Christie, MD, MPH1 and Joshua M Adkinson, MD2, 1Indiana University, Indianapolis, IN, 2Indiana University School of Medicine, Indianapolis, IN, 3Indiana Univeristy, Indianapolis, IN
Introduction:
Targeted muscle reinnervation (TMR) is a well-described technique utilized to combat neuroma and phantom limb pain and provide greater control of a myoelectric prosthetic. At many centers, TMR is now performed concomitantly with primary amputation. TMR for below knee amputation (BKA) is detailed in the literature via a “through-the-wound” approach (TTWA). However, a potentially more straightforward technique is to perform TMR via a “posterior approach” (PA). In contrast to the TTWA, the patient is flipped prone and TMR is then performed via the popliteal fossa. In this study, we sought to compare the PA to a TTWA. Our hypothesis was that the PA would not significantly extend the duration of surgery or impact time to prosthetic fitting.
Methods:
We identified all patients who underwent TMR during BKA via either the PA or TTWA at two facilities in Indianapolis, IN from January 2020 through January 2023. Patients were identified by ICD-10 codes indicative of a BKA combined with the CPT code 64905. Demographic data, operative duration, and physical medicine and rehabilitation notes were obtained from chart review. This study was approved by the Indiana University Institutional Review Board.
Results:
18 patients underwent the PA, and 32 patients underwent the TTWA for TMR at time of BKA. Patients undergoing TMR through the PA had an average operating room time of 236 ± 44 minutes, whereas patients undergoing TMR TTWA had an average operating room time of 193 ± 63 minutes (p = 0.014). 10/18 (55.6%) of patients who underwent TMR via the PA were confirmed to have undergone prosthetic fitting and this occurred at a mean of 1.6 months after surgery. In contrast, 16/32 (50%) of patients who underwent TMR via TTWA were confirmed to have undergone prosthetic fitting and this occurred at a mean of 5.79 months after surgery (p=.008).
Conclusion:
This is the first proof of concept study evaluating the PA to TMR at time of BKA. In this study, we found that a TTWA takes significantly less time than the PA. Despite this, a PA may be technically more straightforward due to the dissection of normal anatomy in a bloodless field. Patients were fit for a prosthetic significantly sooner after TMR via the PA. This could be due to increased dissection through the amputation stump leading to delayed healing in the TTWA. The PA should be considered as an acceptable alternative technique for TMR at time of BKA.
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