Strain in the Median and Ulnar Nerves During Upper-Extremity Positioning Carolyn Byl, MS, Christian Puttlitz, PhD, Nancy Byl, PhD, Jeffery Lotz, PhD, Kimberly Topp, PhD, San Francisco, CA 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 dys- function. 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 se- quences in the clinic to induce nerve strain during evaluation of nerve dysfunction. (J Hand Surg 2002;27A:1032-1040. Copyright © 2002 by the American Society for Surgery of the Hand.) Key words: Upper-limb tension test, excursion, differential variable reluctance transducer, cubital tunnel syndrome, carpal tunnel syndrome. Normal neural tissue accommodates with limb movement. When movement creates global distrac- tion the nerve path straightens and longitudinal slid- ing, or excursion, of the nerve occurs within its bed.i The nerve also elongates first by straightening its undulated axons. 2 The change in length divided by From the Graduate Program in Physical Therapy; and the Depart- ment of Orthopaedic Surgery and the Department of Physical Therapy and Rehabilitation Science, University of California San Francisco/San Francisco State University, San Francisco, CA. Received for publication February 22, 2002; accepted in revised form June 20, 2002. Supported by the California Physical Therapy Fund and the Univer- sity of California San Francisco Willed Body Program. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: Carolyn Byl, MS, PT, 1360 9th Ave, Suite 220, Box 0736, San Francisco, CA 94143-0736. Copyright © 2002 by the American Society for Surgery of the Hand 0363-5023/02/27A06-0006535.00/0 doi:10.1053/jhsu.2002.35886 the initial length is termed nen,e strain. Neural ten- sion tests are used clinically to assess peripheral nerve mobility and achieve noninvasive mobilization of the nervous system. 3-s Based on the anatomic position of the peripheral nerves relative to joints, these tests are designed to target a specific nerve by controlled positioning of the limb ~'3-5"s'9 and length- ening the nerve across a joint. These tests are also designed to progressively stretch the nerve by length- ening first proximally and then distally. For example, with shoulder abduction and glenohumeral external rotation the trunks of the brachial plexus are stretched. 5 The addition of elbow extension then stretches the median nerve. The sequential positioning of the limb also con- trols the direction of nerve excursion and lengthen- ing. s'l° Based on these concepts upper-limb tension tests for the median and ulnar nerves have been developed by Elvey 4 and refined by Butler. 3"7 These tests involve sequential shoulder depression, abduc- 1032 The Journal of Hand Surgery