Fingertip Anatomy

The nail plate consists of onychia, which has similar qualities to the keratin on normal skin. Proximally the nail is produced by the dorsal roof of the nail fold, the germinal matrix [2-3].

Distally the nail plate rests on the sterile matrix to which it is intimately attached through the longitudinal nail furrows and ridges. Proximally the nail plate is enclosed by the eponychium and on the sides by the perionychium and distally by the hyponychium. The lunula is a visible white area of the proximal nail bed distal to the eponychium and represents the transition from germinal matrix to sterile matrix. The distal phalanx supports the nail plate and if the bone is too short due to trauma, it will lead to loss of support and a hook nail type of deformity.

The fingernail and its underlying matrix are supported by more than half the bone length of the underlying terminal phalanx. In the distal pulp of the finger the skin is stabilised by fascial bands running from skin to bone, which contain loculated fat; this arrangement stabilises the fingertip pulp skin under pressure. Nail growth is slow, approximately 0.1 mm daily [2], but often with an initial delay following traumatic avulsion, hence may take 4-6 months to grow back fully and up to 12 months to achieve maturity.