Spinal accessory to suprascapular nerve transfer in brachial plexus injury: outcomes of anterior vs. posterior approach to the suprascapular nerve at associated ipsilateral spinal accessory nerve injury

Objective: The spinal accessory nerve (Acc) is susceptible to trauma in at least 6% of cases of brachial plexus injury (BPI). The impaired Acc function disables its utilization for transfer to the suprascapular nerve (SS). The selection of approach to SS is highly dependant on the anatomy of BPI. The purpose of this study was to determine the incidence of the anterior-posterior approach of Acc to SS transfer in BPI and associated functional outcomes. Methods. Twenty nine patients with BP/Acc associated injury were included. Ten patients underwent the transfer of Acc to SS by the anterior approach (AA), 19 patients – by the posterior approach (PA). Nine nerve transfers through AA and one nerve transfer through PA required the interposition of an autologous nerve graft. The functioning of the supra-/infraspinatus muscle was evaluated at 9 and 15mos. on the basis of the MRC and the external rotation (ER) range. ER more than +400 beyond the sagittal plane was regarded as effective recovery of function. Results. Impaired function (M3 or lower on MRC) of the lower trapezius muscle was associated with preserved anatomy of the SS in the supraclavicular region in 9 out of 10 cases. Eighteen patients (62%) recovered to M3 and higher (shoulder stability), 11of these (38%) showed recovery to M4-M5. Five of all patients recovered to M4-M5 and were able to produce ER within the effective ROM (+400-600 of ER). After the AA to the SS, shoulder stability was restored in 60% of cases (M4-M5 in 30%). After the PA to the SS, shoulder stability was restored in 74% of cases (M4-M5 in 42%). Only non-complete BPI showed effective recovery of power and function in terms of less than 6 mos. after injury. PA to SS with no graft provided shoulder stability in 72% of cases, AA to the SS and the graft interposition ensured shoulder stability in 50% of cases. Conclusions. The incidence of AA to the SS was 35%, PA – 65%; preserved anatomy of the SS in supraclavicular region was associated with an increased risk of trapezius muscle dysfunction; the PA to SS and consecutive direct end-to-end transfer of Acc showed better results compared to other combinations of nerve transfers in providing shoulder stability.