Quantitative Analysis of Human Upper Limb Primary Nerve Branching Points

Introduction: Background: There is limited information on the number of primary nerve branches innervating individual upper limb muscles and where along the arm or forearm are these branches are found. Previous studies agree that the location of these branches is highly variable.

Objective: To describe the number of primary nerve branches innervating individual muscles of the human upper limb and from where along the arm /forearm do they branch out.

Methodology and Material: We dissected 10 fresh frozen human cadaveric upper limbs. The each main peripheral nerve was traced into the muscle it supplies with the least amount of dissection necessary so as not to disturb muscle architecture. The number and location of primary motor nerve branches for 23 muscles were measured. Location was measured using bony landmarks (acromion for the arm and lateral or medial epicondyle for the forearm) as reference points. These findings were then compared with data in published literature.

Results: The number of primary motor nerve branch points to upper limb muscles ranged from one to five with the more complex muscles (Lim Class III) having more branches. Primary nerve branch can be found in the proximal 60% of the muscle belly. They are located in the proximal 60% of the arm and extensor forearm, proximal 40% of the flexor side of forearm.

Conclusions: This data are helpful in planning distal nerve transfers or exploring acute traumatic wounds to determine whether the muscle is still innervated or not.