Selective transfer of nerve to supinator to restore digital extension in central cord syndrome: An anatomical study and a case report.

Background: Nerve transfers are increasingly used to restore upper extremity function in patients with spinal cord injury. However, the role of nerve transfers for central cord syndrome is still being established. The purpose of this study is to report the anatomical feasibility and clinical use of nerve transfer of supinator motor branches (NS) to restore finger extension in a central cord syndrome patient.

Materials And Methods: The posterior interosseous nerve (PIN), its superficial division, and branches were dissected in 14 fresh cadavers, with a mean age of 65 (58-79). Measurements included number and length of branches of donor and recipient, diameters, regeneration distance from coaptation site to motor entry point and axonal counts. A NS transfer to extensor carpi ulnaris (ECU), extensor digiti quinti (EDQ) and extensor digitorum communis (EDC) was performed in a 28-year-old patient, with central cord syndrome after a motorcycle accident, who did not recover active finger extension at 10 months post injury.

Results: The PIN consistently divided into a deep and superficial branch between 1.5 cm proximal to, and 2 cm distal to the distal boundary of the supinator. The superficial branch provided a first common branch to the ECU and EDQ. In 12/14 dissections, the EDC was innervated by a 4 cm long branch that entered the muscle on its radial deep surface. In all cases, the superficial branch of the PIN could be separated in a retrograde fashion from the PIN and coapted with NS. The mean myelinated fiber count in nerve to EDC was 401 ± 190 compared to 398 ± 75 in the NS. At 48 months after surgery, with the wrist at neutral, the patient recovered full metacarpophalangeal extension scoring M4. Supination was preserved with the elbow extended or flexed.

Conclusions: Restoration of finger extension in central cord syndrome is possible with a selective transfer of the NS to EDC, and is anatomically feasible with a short regeneration distance and favorable axonal count ratio.