Evaluation of infraspinatus reinnervation and function following spinal accessory nerve to suprascapular nerve transfer in adult traumatic brachial plexus injuries

Purpose: Our objective was to determine the prevalence and quality of restored external rotation (ER) in adult brachial plexus injury (BPI) patients who underwent spinal accessory nerve (SAN) to suprascapular nerve (SSN) transfer, and to identify patient and injury factors that may influence results. Methods: Fifty-one adult traumatic BPI patients who underwent SAN to SSN transfer between 2000 and 2013, all treated less than 1 year after injury with >1 year follow-up. The primary outcome measured was shoulder ER. The outcomes we utilized included “clinically useful ER” (motion ≥ −35° with ≥MRC 2 strength), modified British Medical Research Council (MRC) grading, and electromyographic (EMG) reinnervation. Results: EMG evidence of re-innervation was found in 85% of patients. Surgery resulted in improved ER in 41% (21/51) of shoulders at an average of 28 months follow-up. Of these, only 31% (17/51) had clinically useful ER. The average ER active range of motion was 12° from full internal rotation (Range: −60° to 90°) and MRC grade 2.2 (2–4). The only predictor of ER improvement was an isolated upper trunk (C5-C6) injury. Improved ER was clinically evident in 76%, 37% and 26% of upper trunk (UT), C5-C6-C7 and panplexus injuries, respectively (P < 0.03). Conclusions: Although 85% had EMG signs of recovery, the SAN to SSN transfer failed to provide useful recovery of ER through reinnervation of the infraspinatus muscle in injuries involving more levels than a C5-C6 root/upper trunk pattern. In patients with greater than C5-6 level injuries alternatives to SAN to SSN transfer should be considered to restore shoulder ER.