Effect of mechanical forces on finger nail curvature: an analysis of the effect of occupation on finger nails.
BACKGROUND
We studied the relationship between mechanical force and nail curvature.


METHODS
The effect of different frequencies and strengths of mechanical force on nail curvature was assessed. In Study 1, 63 carpenters and 63 office workers were enrolled, and the configurations of their thumb nails were assessed by measuring the curve index (defined as nail height/width) and pinch strength. In Study 2, nail curvature and pinch strength of jazz bassists, who characteristically do not use the right fourth and fifth fingers but use the left fifth finger a lot, were compared. In Study 3, the thumb nail curvature and pinch strength of the dominant and nondominant sides of the 126 participants from Study 1 were compared.


RESULTS
Study 1: Carpenters had a significantly lower mean thumb nail curve index and higher mean pinch strength. Study 2: The nails of the unused right fourth and fifth fingers were much more curved than the nails of the frequently used left fourth and fifth fingers. The pinch strength of the right fifth finger was much weaker than the pinch strength of the left fifth finger. Study 3: The dominant side had a significantly lower nail curve index and higher pinch strength.


CONCLUSIONS
The frequency and strength of mechanical forces on finger nails significantly affect nail appearance.
Department of Surgical Science, Graduate School of Medicine, University of Tokyo, Tokyo, Japan; Department of Plastic, Reconstructive and Aesthetic Surgery, Nippon Medical School, Tokyo, Japan.
Hitomi
H
Sano
Kaori
K
Shionoya
Rei
R
Ogawa
D000328:Adult; D060389:Construction Industry; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D009146:Music; D009262:Nails / Q000033:anatomy & histology*; D016273:Occupational Exposure; D052581:Pinch Strength; D013314:Stress, Mechanical