Anatomy of the nerves to the teres minor and the long head of the triceps brachii for electromyography

Background We investigated the branching pattern and topographic anatomy of the nerves to the teres minor (Tm) and the long head of the triceps brachii (LHT) in relation to reference lines extending between surface landmarks, to identify the innervation patterns of, and the optimal needle placement points within, the Tm and the LHT. Methods The anatomical courses of the nerves to the Tm and the LHT were investigated in 37 upper limbs of fresh-frozen cadavers. Distances from the acromion to nerve penetration points, and crossing points of reference lines with the Tm and LHT were measured in 27 cadaveric upper limbs. Results The Tm was innervated by the axillary nerve in all specimens in three patterns, and the LHT was innervated exclusively by the radial nerve. Our dissection and measurements indicate that the midpoint of the reference line from the acromion to the inferior angle of the scapula is the optimal needle insertion point for the Tm. The target point for the LHT appears to be the one-third point of the reference line from the acromion to the medial epicondyle, or the two-thirds point of the reference line from the acromion to the axillary fold. Conclusions We investigated the branching pattern of the nerves to the Tm and the LHT and propose optimal needle placement points for electromyography of the Tm and LHT.

Automated summary

This study investigated the branching pattern and topographic anatomy of the nerves to the teres minor and the long head of the triceps brachii, proposing optimal needle placement points for electromyography. The teres minor is innervated by the axillary nerve in three patterns, while the long head of the triceps brachii is exclusively innervated by the radial nerve. The optimal needle insertion points were found to be the midpoint of the reference line from the acromion to the inferior angle of the scapula for the teres minor, and the one-third point of the reference line from the acromion to the medial epicondyle, or the two-thirds point of the reference line from the acromion to the axillary fold for the long head of the triceps brachii.