Determinants of nail thickness and length.

The determinants of final nail thickness and length at its point of detachment at the onychodermal band were studied in 20 normal great toe-nails, removed after injury, by correlating measurements of nail thickness, taken at six anatomical points, with length of nail and its lunular (matrical) and ventral nail components. Final nail thickness at the onychodermal band was related to initial thickness of the proximal matrix, and independently to the lengths of the lunula and ventral nail, but not to final nail length. There was an increase in nail thickness with age, particularly in the first two decades; this appeared not to be due to a decrease in frictional loss of nail.