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Use of Nerve Allograft in Targeted Motor Reinnervation
Peter S. Wu, MD, MSc ; Brian T. Carlsen, MD Division of Plastic Surgery, Mayo Clinic, Rochester, MN
Introduction: Targeted motor reinnervation (TMR) is a relatively new approach to improving function after upper limb loss. TMR involves surgically re-routing divided nerves to defunctionalized muscles in the residual limb for the purpose of generating electromyographic signals for prosthetic control. Commercially available nerve allograft has been successfully used to bridge nerve gaps, but its use in TMR has not been described. We present a case of a transhumeral amputee who successfully underwent a targeted motor reinnervation procedure using nerve allograft.
Materials/Methods: A 50-year old, right hand dominant woman presented several months after a left transhumeral amputation from a rollover automobile crash. The patient is a nonsmoker, an avid outdoorsman, and uses her hands extensively as an engineer. She had previously undergone amputation revision at an outside facility. Pre-operatively Tinel’s signs were used to localize signals corresponding to median, ulnar and radial innervation. Her biceps and triceps muscles were noted to be present and intuitively functional. A large posterior skin flap was used to cover an anterior defect presumably due to the obliquity of the amputation and loss of anterior soft tissue. The patient underwent TMR of her radial nerve to the long head of the triceps for intuitive hand open signal. Anteriorly, it was recognized intra-operatively that the nerve transection was very proximal (at the level of the medial cord) and there was insufficient length to reach the short head of the biceps. An interpositional human nerve allograft (2-3mm x 3cm Avance. Axogen Inc., Alachua, FL) was used to bridge the nerve gap to the motor branch of the short head of the biceps. Due to a size mismatch, the excess fascicles of the graft were directly implanted into the muscle.
Results: Six months following this procedure, the patient demonstrated voluntary muscle contractions in the distributions of the radial and median nerves consistent with their motor reinnervation. The patient was subsequently able to use a left upper extremity myoelectric prosthesis.
Conclusions: Although the use of patient autograft is traditionally the preferred conduit for motor nerve reconstruction for segmental nerve injury, our patient successfully underwent targeted motor reinnervation with allograft. Further study is needed to determine whether clinical differences exist between autograft and allograft for the purposes of TMR, however we demonstrate that nerve allograft is a feasible option if autograft is unavailable.
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