Intramuscular innervation of upper-limb skeletal muscles.

We studied 150 skeletal muscles from 8 upper limbs using the modified Sihler's staining technique. Based on the pattern of the intramuscular innervation and shape, the muscles were grouped into trapezoidal-shaped (Class I), spindle-shaped (Class II), and muscles that were combinations of these two classes (Class III). Such distinctions are clinically important for limb reconstruction procedures. Bipennate, spindle-shaped muscles with the aponeurosis of the tendons of insertion extending proximally into the muscle belly and Class III muscles with multiple tendons of origin may be split for separate independent functional transfers.