Targeted Muscle Reinnervation in the Upper Arm: A Functional Anatomical Study.

Background: The aim of this study was to accurately locate the neural fascicle controlling hand movement in the upper arm, to enhance expression of motor intention after targeted muscle reinnervation.

Methods: The right sides of the median, ulnar and radial nerves were dissected from distal to proximal in 6 fresh cadaver specimens. The sectional location and diameter of the functional fascicle were measured at 10 and 20 cm below the acromion. The diameter of the main muscle branches of muscle reinnervation target muscles was measured.

Results: The median nerve branch of finger and wrist flexion was mainly located between the 9 and 12 o'clock positions in the plane 10 and 20 cm below the acromion, where the diameter of the nerve fascicle was 2.07 and 2.04 mm, respectively. The ulnar nerve branch of finger and wrist flexion was mainly located between the 8 and 12 o'clock positions, with a diameter of respectively 1.80 and 1.99 mm. The radial branch of finger and wrist extension was mainly located between the 10 and 2 o'clock positions in the plane 10 cm below the acromion and between 6 and 12 o'clock in the plane 20 cm below the acromion, with a diameter of respectively 2.57 and 3.03 mm.

Conclusions: The nerve fascicles innervating the flexor and extensor fingers were distributed in relatively constant regions of the median, ulnar and radial nerve trunks, and their diameters closely matched the muscle branches of the target muscle.