Evaluation of lower trapezius function after transfer of axillary nerve to suprascapular nerve in patients with ERB's palsy.

Background: It is expected that transfer of spinal accessory nerve to suprascapular nerve, which is widely used in the restoration of the shoulder function in brachial plexus birth injury (BPBI), impairs the trapezius function.

Aim: To hypothesize that the lower trapezius muscle remains functional after this neve transfer.

Methods: In a retrospective cross-sectional study, patients with BPBI who underwent nerve transfer from accessory nerve to supraclavicular were followed for at least six months following the operation and demographic data were extracted from the database. To assess the lower trapezius function, shoulder abduction and external rotation were examined, and electromyography and nerve conduction velocity (EMG-NCV) was performed.

Results: A total of 19 patients with a mean age of 2.69 ± 1.40 years and a mean follow-up of 10.5 months were included in the study. Shoulder abduction was disabled completely only in one patient (5.26%); 10 (52.63%) had good, 3 (15.78%) moderate, and 5 (26.31%) had poor shoulder abduction. Regarding external rotation, one (5.26%) was unable to externally rotate the shoulder; among 18 (94.73%) patients who had satisfactory results, 8 (42.10%) were evaluated to be good, 5 (26.31%) moderate, and 5 (26.31%) poor. EMG-NCV showed functional lower trapezius in all patients; its function was evaluated to be good in 11 (57.89%), moderate in 6 (31.57%), and poor in 2 (10.52%) cases.

Conclusion: This study supports the hypothesis that the lower trapezius muscle has a dual motor innervation which provides the possibility of further trapezius tendon transfer to restore a better shoulder function.