LaT Branch Nerve Transfer for Biceps Reinnervation
Asher Schusterman, MD, Rishi Jindal, MD, Jignesh V. Unadkat, MD, MRCS, Alexander M. Spiess, MD.
UPMC, Pittsburgh, PA, USA.
BACKGROUND: In cases of significant upper extremity trauma, the thoracodorsal nerve is a reliable secondary option for the restoration of elbow flexion. In all previous descriptions, however, the entire nerve is transferred. We describe a case utilizing the lateral thoracodorsal nerve (LAT) branch for biceps reinnervation with an associated cadaver study.
METHODS: Transfer of the LAT branch to the biceps branch was performed on a patient who had sustained a traumatic brachial plexus injury that left him without elbow flexion. The patient was seen for follow-up in clinic for one year and also underwent pre- and post-operative electromyography (EMG) testing to asses for reinnervation and remaining latissimus function. Also, four cadavers (eight upper extremities) were dissected to identify the bifurcation of the thoracodorsal nerve, confirm the feasibility of transferring the LAT branch to the biceps motor branch, and define a consistent location of the bifurcation. Axon counts of the thoracodorsal proper, LAT branch, musculocutaneous proper and the biceps branch were also obtained.
RESULTS: The bifurcation of the thoracodorsal nerve was present in all cadaver specimens, and was located, on average, 7.5 cm (range 6.2 - 9.8 cm) inferior to the insertion of the latissimus dorsi muscle on the humerus. Axon counts revealed the LAT branch contained, on average, 1453 ± 289 axons and the biceps contained 1715 ± 699 axons, resulting in a donor-to-recipient ratio of 0.85:1. Follow-up of our patient at one year showed improvement of elbow flexion manual muscle testing grade from 0 to 4/5. Furthermore, EMG at one year confirmed biceps reinnveration and showed normal readings of the latissimus dorsi compared to preoperative EMG.
CONCLUSIONS: Transfer of the LAT branch is a viable and minimally morbid option for biceps reinnervation after traumatic branchial plexus injury. It is effective and available in nearly all patients, and spares the medial branch of the thoracodorsal nerve, preserving innervation to the latissimus dorsi muscle. Further follow-up of our patient and larger prospective studies are needed to understand the true potential of this nerve transfer.
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