Motor nerve transfers for restoration of upper arm function in adult brachial plexus injuries

Introduction. Nerve transfers are the only surgical option in reconstruction of directly irreparable injuries of the brachial plexus. In the recent years there has been a trend toward the increased use of  nerve transfers with introduction of many new methods and novel indications. Patients with total brachial plexus palsy generally have a poor outcome because of a very limited number of donor nerves. On the contrary, patients with partial injuries involving the C5, C6 and sometimes C7 spinal nerves have a remarquable outcome in a large majority of cases. In both situations , restoration of elbow flexion and shoulder functions are the main priorities. It should be emphasized, that in the cases with upper brachial plexus palsy this could be a complete functional recovery. The intention of this review article is a detailed survey on basics of nerve transfers with the comments concerning their advantages, problems and controversies. Analysis is documented with reported outcomes in the literature dealing with the most common methods of nerve transfer.Methods. PubMed/Medline databases were searched for English language basic articles concernig nerve transfers and series of adult patients who had nerve transfers for functional restoration of the upper arm nerves, performed within one year after injury and with minimum follow-up of one year.  Finally, we selected 70 articles . Furthermore, literature search for outcome analysis was limited to the articles published after 1990 that included 45 systematic reviews and meta-analyses of the most common nerve transfers ( intercostal, spinal accessory, fascicular and collateral branches of the brachial plexus ). Analysis of clinical outcomes was based on Medical Research Council (MRC) grading system for muscle strenght, and grades M3 or more were considered as useful functional recovery.Results. Generally, intraplexal nerve transfers resulted with higher rate and better quality of recovery, comparing to the extraspinal transfers. Grades M3 or more were obtained in 72% of the  intercostal and 73% of the spinal accessory nerve transfers for restoration of elbow flexion, and in 56% vs. 98% of transfers for restoration of shoulder function. Among intraplexal nerve transfers , elbow flexion was restored in 84% to 91% of the medial pectoral, 100% of the thoracodorsal and 94% to 100% of the single or double fascicular nerve transfers. Shoulder function was restored in 81,8% of the medial pectoral, 86% to 93% of the thoracodorsal and 100% of the triceps branch nerve transfers. Dual nerve transfers, meanning simultaneous reinnervation of the suprascapular and axillary nerves, resulted with 100% rate of recovery.Conclusion. Double fascicular transfer for restoration of elbow flexion and dual nerve transfer for restoration of shoulder function resulted with significantly better results than the other transfers, especially regarding the quality of recovery, meanning representation of grades M4 and M5 among recoveries. Medial pectoral and thoracodorsal nerve transfers proved as a good alternative for restoration of both functions.