Long-term outcome of accessory nerve to suprascapular nerve transfer in obstetric brachial plexus lesion: functional, morphological, and electrophysiological results.

Purpose: An accessory to suprascapular nerve (XIN-SSN) transfer is considered in patients with obstetric brachial plexus lesion who fail to recover active shoulder external rotation. The aim of this study was to evaluate the quality of extraplexal suprascapular nerve neurotization and to perform a detailed analysis of the infraspinatus muscle (IM) and shoulder external rotation.

Methods: A XIN-SSN transfer was performed in 14 patients between 2000 and 2007. Patients had been operated at the age of 3.7 ± 2.8 years. Follow-up examinations were conducted up to 8.5 ± 2.5 years. Magnetic resonance imaging was performed to investigate muscle trophism. Fatty muscle degeneration of the IM was classified according to the Goutallier classification. We conducted nerve conduction velocity studies of the suprascapular nerve and needle electromyography of the IM to assess pathologic spontaneous activity and interference patterns. Active glenohumeral shoulder external rotation and global shoulder function were evaluated using the Mallet score.

Results: Postoperatively, growth of the IM increased equally on the affected and unaffected sides, although significant differences of muscle thickness persisted over time. There was only grade 1 or 2 fatty degeneration pre- and postoperatively. Electromyography of the IM revealed a full interference pattern in all except one patient, and there was no pathological spontaneous activity. Glenohumeral external rotation as well as global shoulder function increased significantly.

Conclusion: Our results indicate that the anastomosis after XIN-SSN transfer is functional and that successful reinnervation of the infraspinatus muscle may enable true glenohumeral active external rotation.