Abstract
Background and objectives: The subscapularis muscle is typically innervated by two distinct nerve branches, namely the upper and lower subscapular nerve. These usually originate from the posterior cord of the brachial plexus. A large number of variations have been described in previous literature. Materials and Methods: Dissection was carried out in 31 cadaveric specimens. The frequency of accessory subscapular nerves was assessed and the distance from the insertion points of these nerves to the myotendinous junction was measured. Results: Accessory subscapular nerves were found in three cases (9.7%). According to their origin from the posterior cord of the brachial plexus proximal to the thoracodorsal nerve all three nerves were identified as accessory upper subscapular nerves. No accessory lower subscapular nerves were found. Conclusion: Accessory nerves occur rather commonly and need to be considered during surgery, nerve blocks, and imaging procedures.
Highlights
The brachial plexus is typically formed by the ventral rami of the lower four cervical and the upper thoracic nerve roots
The brachial plexus was dissected free from two directions and the path and distribution of nerves innervating the subscapularis were investigated from proximal to distal to the innervation site
An accessory third subscapular nerve was observed in three out of 31 cases: one male left side (Figure 1) and one male and female right side (Figure 2). These accessory nerves originated separately, proximally to the thoracodorsal nerve, from the posterior cord of the brachial plexus, and terminated in the upper and middle part of the subscapularis muscle. Based on these two criteria, the given three nerve branches were identified as accessory upper subscapular nerves
Summary
The brachial plexus is typically formed by the ventral rami of the lower four cervical and the upper thoracic nerve roots. The subscapularis muscle is typically innervated by two distinct nerves, namely an upper and a lower subscapular nerve, both originating from the brachial plexus [4]. The typical pattern described in textbooks are two subscapular nerves, both originating from the posterior cord of the brachial plexus [7]. The subscapularis muscle is typically innervated by two distinct nerve branches, namely the upper and lower subscapular nerve. These usually originate from the posterior cord of the brachial plexus. Conclusion: Accessory nerves occur rather commonly and need to be considered during surgery, nerve blocks, and imaging procedures
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