Quantification of regional matrix nail production.

The relative nail producing capacity of different regions within the nail matrix has not been quantified. In order to do this, the number of nail plate cells in the dorsoventral axis of 12 human great toenails was counted at five sites in the longitudinal axis, and compared with direct measurements of nail plate thickness at the same sites. The mean number of nail cells in the nail plate reached a maximum at the lunula, with no further increase along the length of the nail bed. At the mid-point between the proximal tip of the germinal matrix and lunula, mean cell numbers achieved 81% of the value at the lunula. Mean nail thickness was only 90% of its maximum at the lunula, with a further significant increase (P = 0.02) between the lunula and end of the nail bed. These observations suggest that the proximal nail matrix is the main source of nail within the matrix. This is consistent with clinical experience where distal matrix surgery has a low potential for scarring in comparison with proximal matrix surgery. The additional finding of increased nail thickness, but not cell numbers, along the nail bed make it likely that cells within the nail plate change shape as they move distally.