Nail spicules result from incomplete excision of the nail matrix of the fin
ger. We report a histological study to delineate the surface anatomy of the
nail matrix. Sections were cut longitudinally and transversely in 19 finge
rtips. The proximal midline extent of the nail matrix was measured and expr
essed as a ratio of the distance from the nail fold to the distal interphal
angeal joint, In the lateral sections, the angle subtended between the midl
ine vertical and the lateral extent of the nail matrix was measured. The me
an ratio of the proximal extent was 0.55 in the midline and the lateral ang
ular extent was 66 degrees, The authors recommend that excision of the nail
matrix should be rectangular, extending to the midlateral lines and proxim
ally to a point three-quarters of the distance from the nail fold to the di
stal interphalangeal joint crease.