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The fingertips are sensitive, mobile, and prone to injury. Blunt trauma to the tip of the finger or toe may result in a variety of injuries including fractures, avulsions to the nail and nail apparatus, contusions, lacerations, and amputations. The most common injuries to the distal fingers and toes are crush injuries. The most common mechanisms of injury are closure of some type of door (car, house, etc.) on the finger, dropped objects on the fingers or toes, hand tools, and power tools.

Subungual hematomas often develop following blunt trauma to the distal finger or toe.13 They result from the accumulation of blood between the nail and the nail bed. Treatment of a subungual hematoma is relatively straightforward, yet in some cases it is still controversial. It is important to understand the structure of the distal finger or toe, to determine whether simple drainage will be sufficient management, and to consider how initial management may affect outcome.

The distal digits of the fingers and toes and the nail apparatus are complex structures (Figure 102-1). The perionychium is composed of the nail bed and the surrounding soft tissue. The hyponychium is the junction of the nail bed at the sterile matrix and the fingertip skin beneath the distal margin of the nail. The eponychium is the distal portion of the nail fold where it attaches to the proximal surface of the nail. The lunule is the white arc seen in the proximal portion of the nail. The nail bed consists of the germinal matrix on the proximal ventral floor of the nail fold and the sterile matrix, which extends from the lunule to the hyponychium. The germinal matrix is primarily responsible for the growth of the nail, with a significant contribution from the sterile matrix.4,5 The nail bed must be smooth for normal nail growth. A nail matrix that has not been well approximated to minimize scar formation may develop a deformed nail.1,3–8

Figure 102-1.

The anatomy of the distal fingertip and nail bed. A. Surface anatomy. B. Midsagittal view.

The nail bed receives its blood supply from the two terminal branches of the volar digital artery, which communicate to form blood sinuses. Venous drainage begins at the proximal portion of the nail bed and the skin proximal to the nail fold.4

Force applied to the tip of the finger or toe disrupts the vascular structures in the nail bed. Trauma causes the capillaries of the nail bed to be compressed between the nail and the distal phalanx. Blood collects between the nail bed and the nail, forming a subungual hematoma (Figure 102-2). The patient's pain is directly related to the injury itself and the increased pressure from the hematoma. The hematoma appears as a black-and-blue or black-and-purple area ...

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