Experience with Ultrasound Neurography to Evaluate Targeted Muscle Reinnervation Surgical Outcomes
Emily R Finkelstein, MD1, Arielle Gregory, BS1, Natalia Fullerton, MD1, Jean Jose, DO2 and Helen Hui-Chou, MD, FACS2, 1University of Miami Miller School of Medicine, Miami, FL, 2University of Miami, Miami, FL
Background: Targeted Muscle Reinnervation (TMR) is a nerve transfer procedure that coapts residual mixed motor and sensory nerve endings to motor nerves of target muscles that have lost their primary function following amputation. This study demonstrates the clinical course of patients with poor TMR surgical outcomes, along with the utility of postoperative ultrasound neurography in differentiating the mechanisms of failure.
Materials and Methods: The authors conducted a retrospective review of patients that underwent TMR with senior authors H.H or N.F. between October 2020 and July 2022. Inclusion in this study required the patient to have one or more sites of failed TMR verified postoperatively by ultrasound neurography.
Results: Five patients with an unfavorable TMR outcome were identified. Average patient age was 38 years (range 13 - 58), and the mean body mass index was 26.1 kg/m2 (range 23.7 – 30.7). Four patients (80%) had an amputation in the hand or upper extremity and one patient (20%) had an above-the-knee amputation. Amputation was coupled in the same procedure as TMR in two cases (40%), with the remaining three patients having an average delay between amputation and TMR of 141 days (range 15 - 398). A total of 16 nerve transfers were completed (Table 1). Mean patient follow-up duration was 12 months. Four patients complained of neurogenic pain postoperatively, while three patients had a positive physical examination finding. Patients had an average delay of nine months between neurogenic symptom onset and completion of postoperative imaging. Of the 16 total TMR sites, nine were deemed unsuccessful due to neuroma formation and a lack of integration into the target muscle identified on ultrasound evaluation (Figure 1).
Conclusions: Patients with unsuccessful reinnervation after a TMR procedure can have a non-specific presentation. Ultrasound neurography may have utility by accurately differentiating sites of failed versus successful TMR. Early identification of unfavorable TMR outcomes may lead to timely intervention and foster the discovery of failure mechanisms that can refine surgical practice and improve functional recovery.
Table 1 - ASPN.jpg
Figure 1 - ASPN .jpg
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