The Branching Pattern and Intraneural Distribution of the Musculocutaneous Nerve

Objective: The purpose of this study was to gain additional insights into the musculocutaneous nerve (MCN) branching pattern and its intraneural distribution that should improve the outcome of surgical treatments of elbow flexor spasticity (EFS) and MCN injury.

Methods: The study was performed on 20 human cadaveric arms. The distance from the coracoid process to the exit points of the MCN motor branches was measured and expressed as a percentage of the arm length. The intraneural distribution of each fasciculus was identified at proximal, middle, and distal levels following blunt intraneural dissection from the respective branch termination to the lateral cord.

Results: The MCN branches to the coracobrachialis, biceps, and brachialis muscles arise respectively at approximately 17%, 45%, and 60% of the distance between the coracoid process and the medial epicondyle. Intraneural dissection revealed that sensory fascicles occupied the medial segment of the MCN at the proximal level and the lateral segment at the distal level. In contrast, motor fascicles occupied the anterolateral, lateral, and posterior segments of the MCN at the proximal level and the medial segment at the distal level.

Conclusion: Based on the current data, the lateral half of the proximal and middle levels and the medial half of the distal level of the MCN would be the preferred sites for motor nerve transfer thereby improving chances for positive outcomes of the surgical techniques for EFS and MCN injury treatments.

Author(s): Yehia Elgammal, Andrey Frolov, Yun Tan and John R. Martin*

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