American Society for Peripheral Nerve

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Targeted Muscle Reinnervation in Upper Extremity Spare-Parts Surgery
Michael T Larsen, MD, MPH; Department of Plastic and Reconstructive Surgery, 915 Olentangy River Rd, Suite 2100, columbus, OH; Kyle R Eberlin, MD; Orthopaedic Hand and Upper Extremity Service, Massachusetts General Hospital, Massachusetts General Hospital/Harvard Medical School, Boston, MA; John Byers Bowen, MD, MS; Department of Plastic Surgery, The Ohio State University Wexner Medical Center, Columbus, OH; Ian L. Valerio, MD, MS, MBA; Department of Plastic Surgery, The Ohio State University, Wexner Medical Center, Columbus, OH

Introduction: Targeted muscle reinnervation (TMR) is a relatively recent technique which opens up the possibility for an amputee to operate a myoelectric prosthesis through neural control by coapting severed nerves to alternate muscle recipient sites. Furthermore, this technique shows much promise in decreasing neuroma and phantom limb pain. However, in some extremity amputations, especially fore-quarter amputations, there may be no nearby recipient muscle sites, or the residual nerve may be too short to perform TMR. Using spare-parts from the amputated limb can help solve this problem by providing nerve autograft or by bringing muscle recipient sites more proximal. This study examines techniques and outcomes for spare-parts TMR in upper extremity amputees.

Methods: A retrospective review of all patients that underwent spare-parts TMR between 2016-2017 at two institutions, was performed. Intraoperatively, the proximal stumps of the amputated nerves were identified. A nerve stimulator was used to identify motor nerve branches entering specific muscle sites. These target motor nerves were divided near their entrance into the muscle, and where possible, the proximal stumps of the amputated nerves were then coapted to them. When the proximal nerves were too short, median and/or ulnar nerve was harvested from the amputated limb and used as reverse autograft to span the gap. When amputation resulted in a large soft tissue defect, a spare-parts free flap was used for reconstruction and TMR was performed to target motor nerves in the free flap. Patients are followed to assess for neuroma and phantom limb pain, patient satisfaction, and function.

Results: Five patients have undergone spare-parts TMR. One patient has been lost to follow up. None of the other patients are currently experiencing neuroma or phantom limb pain. A trend toward decreased narcotic use was noted. The patient with the longest follow up, who is six months status post TMR, demonstrates intuitive control of targeted muscles and is being fit for an insurance-approved myoelectric prosthesis.

Conclusion: Our study shows that TMR with eventual neurotization can successfully be performed in amputations without nearby target muscles by using the spare-parts technique. Our results support other published data which show that TMR may decrease the incidence of neuroma and phantom limb pain, and we show that this can be done with nerve autograft or free flap target muscles.

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