Quantitative in vivo studies of median nerve sliding in response to wrist, elbow, shoulder and neck movements.
OBJECTIVE
To examine median nerve sliding in response to upper limb movements in vivo. To determine whether the median nerve can be unloaded.


METHODS
Exploratory study in healthy subjects.Background. Impaired sliding may lead to neuropathic symptoms. In vivo results for neural dynamics in normal subjects are essential to understand changes in upper limb disorders.


METHODS
Ultrasound imaging of the median nerve during 40 degrees wrist extension, 80 degrees shoulder abduction, 90 degrees elbow extension, and 35 degrees contralateral neck side flexion. Frame by frame cross-correlation of image sequences to measure nerve sliding and strain.


RESULTS
Nerve excursion in the forearm and upper arm ranged from 0.3 mm for neck side flexion to 10.4 mm for elbow extension. Additional strain in the forearm for wrist extension was 1.1% (SEM, 0.2%), for shoulder abduction 1.0% (SEM, 0.2%), and for neck side flexion 0.1% (SEM, 0.1%). With the limb flexed, sliding was delayed and sometimes the nerve or the nerve fascicles had a wavy appearance.


CONCLUSIONS
The median nerve is unloaded when the shoulder is adducted or elbow flexed. When the arm is extended (90 degrees shoulder abduction, 60 degrees wrist extension, and elbow straight) the total additional strain in the forearm will be 2.5-3.0%. Even in this position the strain is likely to be below levels that impair blood flow or conduction. Therefore, the median nerve appears well designed to cope with changes in bed length caused by limb movements.


CONCLUSIONS
These results will provide baseline data that can be used to examine entrapment neuropathies.
Dilley
Andrew
A
Department of Physiology, University College London, Gower Street, London WC1E 6BT, UK. a.dilley@ucl.ac.uk
Lynn
Bruce
B
Greening
Jane
J
DeLeon
Nicola
N
D000328:Adult; D001132:Arm / Q000502:physiology*; D001696:Biomechanical Phenomena; D004551:Elbow Joint / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000000981:diagnostic imaging / Q000502:physiology*; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D009333:Neck / Q000502:physiology; D012785:Shoulder Joint / Q000502:physiology; D014463:Ultrasonography; D014955:Wrist Joint / Q000502:physiology