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

Abstract

Significant excursion of the ulnar nerve is required for unimpeded upper extremity motion. This study evaluated the excursion necessary to accommodate common motions of daily living and associated strain on the ulnar nerve. The 2 most common sites of nerve entrapment, the cubital tunnel and the entrance of Guyon's canal, were studied. Five fresh-frozen, thawed transthoracic cadaver specimens (10 arms) were dissected and the nerve was exposed at the elbow and wrist only enough to be marked with a microsuture. Excursion was 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) DVRT strain device was applied to the nerve at both the elbow and wrist. Nerve excursion associated with motion of the shoulder, elbow, wrist, and fingers (measured by goniometer) was measured at the wrist and elbow. An average 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 excursion of the ulnar nerve was required at the wrist. When all the motions of the wrist, fingers, elbow, and shoulder were combined, 21.9 mm of ulnar nerve 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 and 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 syndrome or ulnar neuropathy at Guyon's canal.

Strain and excursion of the sciatic, tibial, and plantar nerves during a modified straight leg raising test

“…This is consistent with human upper limb 16,17 and animal studies. 18 In agreement with earlier work by Daniels et al, 19 ankle dorsiflexion increased strain in the tibial nerve around the ankle (þ3.3%) and resulted in a considerable distal excursion (9.5 mm).…”

“…Although previous studies have demonstrated the usefulness of these transducers to measure strain in nerve trunks, [15][16][17] we used three consecutive repetitions of SRL TIBIAL in five cadavers to calculate the intraclass correlation coefficient [ICC(2,1)] and standard error of measurement (SEM) as measures of reliability for the strain in the tibial nerve around the ankle. The analysis revealed that the strain measurements were reliable in the different position of SLR TIBIAL …”

Incidence of ulnar nerve entrapment at the elbow in repetitive work

“…The boundaries of the fibro-osseous cubital tunnel involved in "cubital tunnel entrapment" in the elbow (alternative name for ulnar nerve entrapment at the elbow) are the olecranon and the ulnar collateral ligament laterally, the medial epicondyle with the ulnar nerve sulcus anteriorly, and the cubital tunnel retinaculum (also called Osborn ligament), and the bridging aponeurosis of the two heads of the flexor ulnar carpi muscle (one of the medial epicondyle muscles) medially (21)(22)(23)(24)(25). Anatomic studies explain the effects of repetitive strain on the ulnar nerve at the elbow, and this explanation furthers the understanding of the physiopathology of the disorder (25,26). The association observed between obesity and ulnar nerve entrapment at the elbow can be explained by mechanisms similar to those involved in carpal tunnel syndrome, dealing with the increase of fat and edema in the cubital tunnel.…”

The “Hierarchical” Scratch Collapse Test for Identifying Multilevel Ulnar Nerve Compression

“…These findings make sense considering the known pathophysiology of cubital tunnel syndrome. Indeed, whereas the ulnar nerve may be compressed by the thickened confluence of fascia between the two heads of the FCU (and therefore more likely to generate a positive SCT), it is the dynamic tension on the nerve with elbow flexion behind the medial epicondyle that may also contribute to symptomatology [9,11,28,33,37].…”