Radial nerve excursion and strain at the elbow and wrist associated with upper-extremity motion

This study evaluated the excursion necessary to accommodate common motions of daily living and associated strain on the radial nerve. The radial nerve was evaluated at the wrist and proximal to the elbow before it bifurcated.

Five fresh-frozen transthoracic cadaver specimens (10 arms) were dissected; the radial nerve was exposed at the elbow and wrist only enough to be marked with a microsuture. Excursion was measured using a laser mounted on a caliper fixed to the bone and aligned in the direction of nerve motion. Strain was measured with a device applied to the nerve at the elbow. Nerve excursion associated with motion of the shoulder, elbow, wrist, and fingers (measured by a goniometer) was assessed at the wrist and elbow.

An average of 4.3 mm of radial nerve excursion was required at the wrist to accommodate wrist motion from 15 degrees of radial deviation to 30 degrees of ulnar deviation and 8.8 mm was needed for elbow motion from 10 degrees to 90 degrees . The radial nerve at the elbow experienced a 28% strain associated with the same motion of flexion and extension at the elbow. When all the motions of the wrist, fingers, elbow, and shoulder were combined 9.4 mm of radial nerve excursion was required at the wrist and 14.2 mm at the elbow.

Any factor that limits excursion at these sites could result in repetitive traction of the nerve and possibly could play a role in the pathophysiology of a mechanical neuropathy, which in the case of the radial nerve most often manifests as pain.