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The fingernail plays an important functional role in the mechanism of pinch and grasp.1,2 It increases the sensitivity of the fingertip.2 The fingernails are frequently injured due to their anatomic location and their functional role. Immediate primary repair is the ideal management when these injuries involve the nail bed and surrounding skin fold structures.2,3 Careful repair is necessary to avoid functional impairment and cosmetic derangement of the nail plate.4 The following discussion will refer primarily to the fingernail. The toenail has less importance, both cosmetically and functionally, as grasp and pinch are not needed. However, all the principles and recommendations made also apply to the toenail.5

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The nail plate enhances the sensibility of the fingertip by applying a counterforce to the pulp space nerve endings.2 The digital tip and the nail plate also function in unison to smoothly coordinate normal pinch and grasp, which are important for picking up fine objects such as coins and pins.1,2

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The nail plate is comprised of compacted, flattened, and elongated anucleated cells that originate from cornified epithelial cells.6 There are three atomic sites where these cells exist.1,3 The nail bed contains two of the sites: the sterile matrix and the germinal matrix.1 The other location is the dorsal roof matrix (Figure 87-1A). Of these, the germinal matrix is the most important for normal nail growth.3 The germinal matrix is responsible for approximately 90 percent of the nail plate by volume.1 The sterile matrix is responsible for a small percent of the nail plate by volume and varies from individual to individual. This cell production accounts for the nail plate being thicker at its distal tip compared to its proximal origin.1 The nail cells from the dorsal roof matrix are small in number and form a very thin layer on the surface of the nail plate. These cells are responsible for the shine of the nail. If the dorsal roof is destroyed, the nail will lose its shine and become dull.

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Figure 87-1
Graphic Jump Location

Anatomy of the fingernail. A. Lateral view. B. Top view. The colored area represents the perionychium.

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Skin overlies the nail plate proximally and laterally (Figure 87-1B).6 The proximal skin fold is referred to as the eponychium. The eponychium protects the germinal matrix located in the proximal nail bed and is the home of the dorsal roof matrix. The skin immediately over the dorsal roof is called the nail wall.1 The lateral skin folds, the adjacent cutaneous areas, and the adjacent nail bed (germinal matrix and sterile matrix) are collectively referred to as the perionychium (Figure 87-1B).1,4,6 The lunule is the pale arc just distal to the eponychium ...

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