“Anatomy of the superficial radial nerve and its target nerves for targeted muscle reinnervation: an anatomical cadaver study”

Abstract

Background: Targeted muscle reinnervation (TMR) is a surgical procedure for treating symptomatic neuroma, in which the neuroma is removed and the proximal nerve stump is coapted to a donor motor branch innervating a nearby muscle. This study aimed to identify optimal motor targets for TMR of the superficial radial nerve (SRN). Methods: Seven cadaveric upper limbs were dissected to describe the course of the SRN in the forearm and motor nerve supply—number, length, diameter, and entry points in muscle of motor branches—for potential recipient muscles. Results: The radial nerve provided three (three of six) motor branches, two (two of six) motor branches, or one (one of six) motor branch to the brachioradialis muscle, entering the muscle 21.7 ± 17.9 to 10.8 ± 15 mm proximal to the lateral epicondyle. One (one of seven), two (three of seven), three (two of seven), or four (one of seven) motor branches innervated the extensor carpi radialis longus muscle, with entry points 13.9 ± 16.2 to 26.3 ± 14.9 mm distal from the lateral epicondyle. In all specimens, the posterior interosseous nerve gave off one motor branch to the extensor carpi radialis brevis, which divided into two or three secondary branches. The distal anterior interosseus nerve was assessed as a potential recipient for TMR coaptation and had a freely transferable length of 56.4 ± 12.7 mm. Conclusions: When considering TMR for neuromas of the SRN in the distal third of the forearm and hand, the distal anterior interosseus nerve is a suitable donor target. For neuromas of the SRN in the proximal two-thirds of the forearm, the motor branches to the extensor carpi radialis longus, extensor carpi radialis brevis, and brachioradialis are potential donor targets.

Use of Supinator Motor Branches in Targeted Muscle Reinnervation of the Superficial Radial Nerve

“…5,6 Several recent studies have investigated possible TMR targets for SRN neuromas, with cadaver studies demonstrating the technical feasibility of performing TMR of the SRN into the terminal anterior interosseous nerve, 3,7 and into motor branches to the ECRL, ECRB, and BR. 7 One case report discusses the successful use of TMR of the SRN in an end-to-side fashion into a motor branch of the PIN, 6 and a recent case series reports the management of painful neuroma of the SRN with TMR into a distal motor branch of the ECRB with compelling early improvement in the pain scores in all patients. 5 The technique described in this study uses TMR of the SRN into the nerve to supinator branches.…”

“…They are also a favorable size match for the SRN, unlike many clinical examples of TMR that have substantial donor and recipient size mismatches. 7 The supinator is a reliable nerve-transfer donor with minimal donor site morbidity. 10 In contrast, the ECRB and the ECRL may only have one motor branch available, and TMR in these scenarios can result in denervation of major contributors to wrist extension.…”

“…10 In contrast, the ECRB and the ECRL may only have one motor branch available, and TMR in these scenarios can result in denervation of major contributors to wrist extension. 7 TMR to the BR or the ECRL may require a much more proximal incision crossing the elbow joint. The ECRL, ECRB, and BR are common tendon and nerve transfer donors, and saving them may be prudent in the event of any future or concurrent hand trauma.…”

“…3,4 Recent reports demonstrate promising early outcomes of TMR of the SRN to motor branches of the extensor carpi radialis brevis (ECRB) 5 and posterior interosseous nerve (PIN), 6 with cadaveric studies demonstrating technical feasibility of TMR of the SRN to the extensor carpi radialis longus and brevis (ECRL/ ECRB), brachioradialis (BR), and anterior interosseous nerve. 3,7 Although motor targets such as the BR, ECRL, or ECRB can be used, exposure of these motor targets can require surgery at or proximal to the elbow. Denervation of these muscle groups may be undesired in cases of complex upper extremity injury where these critical donors may be needed for other tendon or nerve transfer procedures.…”