The nerve to the levator scapulae muscle as donor in brachial plexus surgery: an anatomical study and case series.

Nerve transfers are commonly used in treating complete injuries of the brachial plexus, but donor nerves are limited and preferentially directed toward the recovery of elbow flexion and shoulder abduction. The aims of this study were to characterize the anatomical parameters for identifying the nerve to the levator scapulae muscle (LSN) in brachial plexus surgery, to evaluate the feasibility of transferring this branch to the suprascapular nerve (SSN) or lateral pectoral nerve (LPN), and to present the results from a surgical series. Supra- and infraclavicular exposure of the brachial plexus was performed on 20 fresh human cadavers in order to measure different anatomical parameters for identification of the LSN. Next, an anatomical and histomorphometric evaluation of the feasibility of transferring this branch to the SSN and LPN was made. Lastly, the effectiveness of the LSN-LPN transfer was evaluated among 10 patients by quantifying their arm adduction strength. The LSN was identified in 95% of the cadaveric specimens. A direct coaptation of the LSN and SSN was possible in 45% of the specimens (n = 9) but not between the LSN and LPN in any of the specimens. Comparison of axonal counts among the three nerves did not show any significant difference. Good results from reinnervation of the major pectoral muscle (Medical Research Council grade ≥ 3) were observed in 70% (n = 7) of the patients who had undergone LSN to LPN transfer. The LSN is consistently identified through a supraclavicular approach to the brachial plexus, and its transfer to supply the functions of the SSN and LPN is anatomically viable. Good results from an LSN-LPN transfer are observed in most patients, even if long nerve grafts need to be used.