Median nerve fascicle to posterior interosseous nerve transfer to restore finger extension.

BACKGROUND

A 19-year-old man who developed wrist drop due to a radial nerve injury secondary to a right humeral shaft fracture sustained during a motor vehicle accident that required open reduction and internal fixation, complicated by infection requiring plate removal. Electromyography (EMG) showed severe radial neuropathy distal to the innervation of the triceps with prolonged latency and decreased amplitude. The patient's history, physical examination, and EMG findings were convincing for traumatic radial neuropathy. We therefore recommended a two-stage radial nerve surgery. Stage I, a median nerve flexor digitorum superficialis (FDS) branch to the posterior interosseous nerve (PIN) transfer, is detailed in this video. Stage II, a sural nerve interposition cable graft replacing the nonfunctioning traumatic neuroma found proximally in the radial nerve adjacent to the humeral shaft plate, was performed 5 weeks later.

CASE DESCRIPTION: Neurological examination demonstrated an inability to extend his wrist and fingers and diminished sensation over the radial nerve distribution of the dorsal hand and fingers. Right upper extremity strength was otherwise 5/5 with intact sensation in the remaining nerve distributions. The patient consented to a median nerve FDS branch to PIN transfer. Risks, benefits, and alternatives were discussed; he asked several well-informed questions and agreed to proceed with surgery. At 3- and 6-month follow-up, the patient had no return of radial nerve motor or sensory function. Repeat EMG at 3 and 6 months demonstrated no motor unit potentials in radial nerve-innervated muscles distal to the triceps. 5-weeks after this procedure, the patient underwent stage II of this radial nerve surgery with a sural nerve interposition cable graft replacing the nonfunctioning traumatic neuroma found proximally in the radial nerve adjacent to the humeral shaft plate location. At 1-year follow-up, the patient was found to have 4/5 wrist extension with radial deviation, 2/5 finger extension, and 0/5 extensor pollicis longus. Repeat EMG performed at 12 months demonstrated evidence of reinnervation of the brachioradialis, extensor carpi radialis, extensor digitorum communis, and extensor indicis proprius.

CONCLUSION

In the setting of traumatic radial nerve injury leading to loss of wrist and finger extension, the transfer of a fascicle of the median nerve to the PIN is able to restore finger extension at 1 year.