Nail unit incision lines: A tool to minimize nail unit scarring.

Langer's lines, lines of cleavage, and biodynamic excisional skin tension (BEST) lines have been defined for cutaneous surgery to ensure excisional wound closure with the least tension on any part of the body and minimize scarring. This article describes nail unit incision lines (NUIL) with a similar perspective. NUIL are followed by nail surgeons to help regrowth of a normal nail; however, they are not widely understood or respected during nail surgery. Within the anatomically small nail unit, the orientation of these lines varies depending on the area being operated upon. Nail bed incisions should be oriented longitudinally, while nail matrix incisions should be oriented horizontally. Being the germinative portion, the nail matrix should be dealt with more cautiously, avoiding the lunular margin. Lateral nail fold incisions should be longitudinal, while proximal nail fold incisions should be radial. Distal nail fold (hyponychial) incisions should preferably be oriented parallel to the distal nail ridge. Knowledge and compliance with NUIL can help minimize scarring outcomes in nail surgery.