A comparative study of A1 pulley compliance.
BACKGROUND
Trigger finger is most common in the ring finger, but the reason for this is not known. We hypothesized that the compliance of the A1 pulley might be one of the factors responsible for this phenomenon. The purpose of this study was therefore to compare the compliance of the normal A1 pulley of the thumb, index, middle, ring and little fingers using human cadavers.


METHODS
Eight normal thumbs, index, middle, ring and little fingers from eight fresh frozen human hand cadavers were used in this experiment. The compliance of the A1 pulley was measured by the resistance when passing a tapered metal rod through the A1 pulley. The slopes of the linear region of radial force/increasing area ratio curve were calculated and analyzed.


RESULTS
The mean slope of the linear region of the radial force/increasing area ratio curve was significantly different among the five digits (p<0.05). Post hoc analysis indicated that the mean slope for the middle finger A1 pulleys was larger than the thumb and little finger A1 pulleys (p<0.05).


CONCLUSIONS
The findings did not support our clinical hypothesis that A1 pulley stiffness would parallel the relative frequency of trigger finger by digit.
Tung
Wen-Lin
WL
Biomechanics Laboratory, Department of Orthopedics, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
Zhao
Chunfeng
C
Yoshii
Yuichi
Y
Amadio
Peter C
PC
Su
Fong-Chin
FC
An
Kai-Nan
KN
D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D004867:Equipment Design; D005260:Female; D005385:Fingers / Q000033:anatomy & histology* / Q000473:pathology; D006225:Hand / Q000033:anatomy & histology; D006801:Humans; D008297:Male; D013717:Tenosynovitis; D013933:Thumb / Q000033:anatomy & histology* / Q000473:pathology; D052582:Trigger Finger Disorder / Q000473:pathology* / Q000601:surgery