Dorsal approach in transfer of the distal spinal accessory nerve into the suprascapular nerve: histomorphometric analysis and clinical results in 14 cases of upper brachial plexus injuries

Abstract

Purpose: The spinal accessory nerve (SAN) is conventionally transferred to the suprascapular nerve (SSN) through an incision in the supraclavicular region (the anterior approach) to improve shoulder function in brachial plexus injuries. This approach carries a risk of partial denervation of upper trapezius muscle. Here we describe how dorsal nerve transfer through an incision placed directly over the scapular spine preserves the proximal branches to the upper trapezius muscle and allows nerve transfer close to target muscles.

Methods: We report our experience with the dorsal approach in 14 cases managed between February 2007 and January 2008. Results were compared with 21 control cases treated by the anterior approach. In addition, we submitted proximal cut ends of the SAN in 10 cases from the experimental group for histomorphometry.

Results: A total of 11 patients had C5 and C6 injuries, whereas 3 had associated C7 injuries. The denervation period ranged between 3 and 10 months. In all cases, the distal SAN could be transferred to the SSN without a graft. Histomorphometry revealed an average of 1,671 myelinated axons. Shoulder abduction and external rotation were restored in 13 and 9 cases, respectively, compared with 16 and 12, respectively, in the control group. Electromyography revealed the first sign of reinnervation of infraspinatus muscle at 23 ± 4 weeks, compared with 30 ± 4 weeks in the control group. Initial evidence of shoulder abduction appeared earlier in the study population (28 ± 4 vs 34 ± 4 weeks). Shoulder abduction and external rotation in the study group ranged between 70° and 170° and 30° and 80°, compared with 65° and 160° and 22° and 55° in the control group. Using the Medical Research Council (MRC) grading system, at 6 months postreconstruction, 13 patients had M4 power in the trapezius muscle, whereas 1 had M3, compared with 5 in the control group who displayed grade 3 weakness.

Conclusions: A dorsal approach for transfer of the distal SAN into the SSN is an alternative and effective technique in restoring shoulder function in upper brachial plexus injuries.

Type of study/level of evidence: Therapeutic III.