Static wrist position associated with least median nerve compression: sonographic evaluation.
OBJECTIVE
To determine the wrist angle that produces the least compression to the median nerve and to evaluate the usefulness of sonography in determining the optimal position.


METHODS
Seventeen wrists of 17 healthy volunteers received dynamic, high-frequency (8 MHz), high-resolution sonography with the wrist splinted at various positions: 15 degrees of flexion, neutral position, and 15 degrees and 30 degrees of extension. The morphologic changes of the median nerve were evaluated with the wrist positioned at various angles.


RESULTS
The neutral position caused significantly lower compression of the median nerve than it did in the other positions. However, in some cases, the lowest pressure was found when the wrist was fixed in 15 degrees of flexion or 15 degrees of extension. Because median nerve compression may decrease the anteroposterior diameter, increase the transverse diameter, and decrease the cross-sectional area, greater anteroposterior diameter, lower flattening ratio (transverse diameter/anteroposterior diameter), and greater cross-sectional area were considered to indicate lower median nerve compression.


CONCLUSIONS
Neutral position of the wrist is the best position with the least median nerve compression in most individuals. However, the optimal position may vary from person to person. Sonographic examination can help to determine the splint position that results in the lowest median nerve compression.
Department of Physical Medicine, Chang Gung Memorial Hospital, Kaosiung, Taiwan.
M H
MH
Kuo
C P
CP
Leong
Y F
YF
Cheng
H W
HW
Chang
D000328:Adult; D000704:Analysis of Variance; D002349:Carpal Tunnel Syndrome / Q000000981:diagnostic imaging* / Q000534:rehabilitation; D005260:Female; D006801:Humans; D007103:Immobilization; D008297:Male; D008475:Median Nerve / Q000000981:diagnostic imaging* / Q000502:physiology; D011187:Posture; D013165:Splints; D014463:Ultrasonography; D014955:Wrist Joint / Q000000981:diagnostic imaging* / Q000502:physiology