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

Significant excursion of the ulnar nerve is required for unimpeded upper ex tremity motion. This study evaluated the excursion necessary to accommodate common motions of daily living and associated strain on the ulnar nerve. T he 2 most common sites of nerve entrapment, the cubital tunnel and the entr ance of Guyon's canal, were studied. Five fresh-frozen, thawed transthoraci c cadaver specimens (10 arms) were dissected and the nerve was exposed at t he elbow and wrist only enough to be marked with a microsuture. Excursion w as measured with a laser mounted on a Vernier caliper fixed to the bone and aligned in the direction of nerve motion. A Microstrain (Burlington, VT) D VRT strain device was applied to the nerve at both the elbow and wrist. Ner ve excursion associated with motion of the shoulder, elbow, wrist, and fing ers (measured by goniometer) was measured at the wrist and elbow. An averag e of 4.9 mm ulnar nerve excursion was required at the elbow to accommodate shoulder motion from 30 degrees to 110 degrees of abduction, and 5.1 mm was needed for elbow motion from 10 degrees to 90 degrees. When the wrist was moved from 60 degrees of extension to 65 degrees of flexion, 13.6 mm excurs ion of the ulnar nerve was required at the wrist. When all the motions of t he wrist, fingers, elbow, and shoulder were combined, 21.9 mm of ulnar nerv e excursion was required at the elbow and 23.2 mm at the wrist. Ulnar nerve strain of 15% or greater was experienced at the elbow with elbow flexion a nd at the wrist with wrist extension and radial deviation. Any factor that limits excursion at these sites could result in repetitive traction of the nerve and possibly play a role in the pathophysiology of cubital tunnel syn drome or ulnar neuropathy at Guyon's canal. Copyright (C) 2001 by the Ameri can Society for Surgery of the Hand.