THE LUNULA - A MAGNETIC-RESONANCE-IMAGING APPROACH TO THE SUBNAIL MATRIX AREA

High-resolution sagittal magnetic resonance images depict an oval area in the dermis beneath the nail matrix that gives a particular signal. This study defines the magnetic resonance imaging characteristics of this area and examines its correlation with the lunula. A high-resolut ion surface gradient coil specially designed for skin imaging was used on a 1.5 T magnetic resonance unit. The subnail matrix (SNM) areas of 12 subjects had a significantly longer T2 relaxation time and a highe r enhancement ratio after injection of gadolinium than did the nail be d dermis. The length of the SNM area distal to the free edge of the pr oximal nail fold was highly correlated with the length of the lunula ( R = 0.98) in 30 fingers and 10 toes. The total length of the SNM area was somewhat correlated with the nail thickness (R = 0.86) in 30 finge rs. The histology and microvascularization of the subungual tissue in 21 fingers showed that this SNM area had specific features: The area w as composed of loose connective tissue without bundles, and the reticu lar and subdermal vascular networks had large regular meshes in this o val area. The lunula is shown to be linked to a well-defined area in t he underlying dermis with a specific histology and microvascularizatio n.