Reinnervating the Median and Musculocutaneous nerve in Total Brachial Plexus Injury: Free Ulnar Nerve (FUN) flap for C5 grafting

Median nerve (MN) reinnervation in total brachial plexus injury (TBPI) is often neglected due to inconsistent outcomes with sural grafting or use of extra-plexus donors for nerve transfer. 1 Here we describe the novel use of the vascularized nerve flap concept to improve grafting from the C5 root to the MN, using the Free Ulnar Nerve (FUN) flap to improve reliability of perfusion along the entire nerve length. Targeting the MN allows movement of the finger flexors, wrist flexors, and forearm pronators and provides sensation in the hand. Magnetic Resonance Neurography of C5 ventral and dorsal rootlets enables preoperative assessment of C5 spinal nerve stump quality to improve donor reliability. Click or tap here to enter text.2 In 13 consecutive patients with long-term follow-up, ten (77%) regained finger flexion ≥ MRC M2 after median nerve reinnervation. Three achieved ≥ M3 with nerve reconstruction alone, six required tendon transfer from the reinnervated wrist flexors to achieve ≥ M3 and one required additional functioning muscle transplantation reusing the motor branches of the reinnervated median nerve. In 12 patients, the FUN flap simultaneously innervated the musculocutaneous nerve via the dorsal cutaneous branch of the ulnar nerve. Ten patients (83%) achieved ≥ M3 elbow flexion, and 7 (58%) achieved M4 flexion. Twelve patients (92%) regained ≥ S2 sensory function in the palm and thumb. Patients reported meaningful limb use, including eating, carrying objects, and performing daily tasks.