Background and objective.

The musculocutaneous nerve (NMC) innervates biceps, coracobrachialis and brachialis muscle, whose main function is to flex the elbow. Knowledge of the anatomy and variations in motor branches allow to carry out nerve transfer surgery to recover the functionality of elbow flexion when the musculocutaneous nerve is injured.

Our aim is to describe the anatomical and biometric distribution of the main terminal motor and sensitive branches of the MCN during its course in the upper limb in bodies of a local Colombian population.

Methods.

Descriptive anatomical study in corpses of upper limbs using dissections to find the origin site of the NMC motor and sensitives branches in relation to constant anatomical structures and their number of terminal branches when they reach the respective muscle bellies.

Results.

Dissections were performed on 30 upper extremities. MCN crosses the coracobrachialis muscle 56 mm (SD 17) from the coracoid process; the motor branch of the biceps leaves de NMC trunk at 142 mm (SD 44); 80% of the branches are located in the middle third, 14% in the proximal third and 6% in the distal third; there is 1 motor branch for biceps in 57% of cases, 2 in 27% and 3 or more in 16%; the length of the motor branches is 34 mm (SD 17). For brachialis muscle, the motor branch leaves de NMC trunk at 181 mm (SD 28) from the coracoid process; there is 1 motor branch for brachialis muscle in 70% of cases, 2 in 20% and 3 or more in 10%; 88% of the branches are located in the middle third and 12% in the distal third; the length of the motor branches of the BR is 44 mm (DS 17). Union with the median nerve was found in the middle third of the arm in 10%.

Conclusions.

In our local Colombian population study, the NMC nerve presented a constant anatomical distribution along its path, showing variation in branching patterns for the biceps and brachialis muscle. Anatomical variations such as the junction with the median nerve are found in a presentation similar to those reported worldwide.

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