Optimal sites and depths for skin puncture of infants and children as assessed from anatomical measurements.

Postmortem measurements were made of distances from skin surface to underlying bone/cartilage on 43 children (up to 8 y old; weights from 0.7 to 26.4 kg) to determine optimal sites and lengths of lancet tips for skin puncture of the heel, great toe, and middle finger. For measuring depths, a needle-like probe was devised that minimized disfigurement. As long as the infant's heel was available for puncture prior to callus formation (to about six months), it offered the greatest depth and the bone/cartilage of the lateral/medial sites was considerably deeper than posterior sites. At age six months, the mean distance of skin surface. At age six months, the mean distance of skin surface to bone/cartilage in the middle finger was 2.5 mm, the lower 95% prediction interval being 1.5 mm. Lengths of lancet tips for finger puncture should therefore be made less than 1.5 mm. To get the desired volumes of blood, a compromise must be reached between depth and width of the lancet tip.