Strain in the median and ulnar nerves during upper-extremity positioning.

The purpose of this study was to quantify the strain of the median nerve and the ulnar nerve throughout upper-extremity positioning sequences used by clinicians to evaluate nerve dysfunction. A microstrain gauge was used to quantify strain and digital calipers were used to assess nerve excursion in 4, fresh, intact cadavers. Data analysis of noncontinuous motion trials showed that the median nerve tension test caused a maximum summative strain in the median nerve at the carpal tunnel of 7.6%, with the largest increase in strain during elbow extension (3.5%). Components of the median nerve tension test decreased strain in the ulnar nerve at the cubital tunnel. The ulnar-nerve tension test caused a maximum summative strain in the ulnar nerve of 2.1%, with the largest increase in strain during shoulder abduction (0.9%). Some components of the ulnar-nerve tension test decreased strain in the median nerve. These cadaver findings lend support to the use of upper-extremity positioning sequences in the clinic to induce nerve strain during evaluation of nerve dysfunction.