Efficacy of Spinal Accessory Nerve to Suprascapular Nerve Transfer to Restore Shoulder Function in Brachial Plexus Injury: A Systematic Review

Introduction: Transfer of the spinal accessory nerve (SAN) to the suprascapular nerve (SSN) is a common surgical intervention employed for restoring shoulder function in both obstetric and traumatic brachial plexus injuries. Despite its widespread use, there is a paucity of evidence surrounding the efficacy of this procedure.

Methods: A systematic search of the literature in the National Institutes of Health MEDLINE and Embase databases was performed between January 1980 to June 2024 in accordance with the PRISMA guidelines. Clinical trials, and retrospective and prospective cohort studies reporting on shoulder abduction strength, measured using the British Medical Research Council (MRC) scale, or range of motion (ROM) after SAN-SSN transfer surgery for brachial plexus injury, were included. Patients had to have a minimum postoperative follow-up of 6 months. Cohorts containing patients with obstetric brachial plexus injuries were excluded.

Results: Twelve primary studies with a total of 313 total participants met the criteria for inclusion. The average age of participants was 27.03 years (standard deviation [SD]: 1.03) and the male:female ratio was 25:1. Nine studies reported on the shoulder abduction strength using the MRC scale and 9 studies reported shoulder abduction ROM in degrees. All patients underwent surgery following traumatic brachial plexus injury and the average time-to surgery was 6.32 months(SD: 0.07). 66.67% of patients achieved a post-operative MRC grade of shoulder abduction of >=M3 with a mean MRC score of 2.67 (SD: 0.02). Average post-operative shoulder abduction ROM was 57.3 degrees (SD: 2.18). Average follow-up duration for all reported outcomes was 24.62 weeks (SD: 0.1).

Conclusion : The majority of patients achieve a ‘good’ (>=M3) score for shoulder abduction and restoration of ROM to beyond 50 degrees following SAN-SSN transfer. SAN-SSN transfer thus appears to be an effective intervention for the restoration of shoulder function following brachial plexus injury.