The fingers and toes are two of the most commonly injured areas of the body. The distal ends of these digits (i.e., the nail apparatus) are especially prone to injury. Digital injuries include amputations, avulsions, contusions, crush injuries, fractures, and lacerations. The most common injuries to the distal fingers and toes are crush injuries (e.g., closure of a door and dropped objects). Digital injuries occur when the distal aspect of the finger or toe is caught between two objects and typically involves a large amount of force.
Subungual hematomas often develop following blunt or crush injuries to the distal fingers or toes (Figure 127-1).1-3 Hematomas can form from repetitive mild trauma to the digits (e.g., running while wearing tight shoes). These injuries cause accumulation of blood between the nail and the nail bed and result in a subungual hematoma (Figure 127-2). 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 (Figure 127-3) to determine whether drainage alone will be sufficient management and to also consider how initial management may affect outcome.
A subungual hematoma. (Courtesy of Path Scientific LLC, Carlisle, MA.)
The subungual hematoma. A. Surface view. B. Sagittal view.
The anatomy of the distal fingertip and nail bed. A. Surface anatomy. B. Midsagittal view.
ANATOMY AND PATHOPHYSIOLOGY
The nail apparatus is a complex structure composed of multiple components (Figure 127-3). The nail plate is a keratinized structure that overlies the nail bed and matrix.4 It is curved on three edges to allow it to embed into the surrounding soft tissues. 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 plate. The matrix is visible in the proximal portion of the nail as a white half-moon structure known as the lunula.
The nail bed consists of the germinal matrix on the proximal ventral floor of the nail fold and the sterile matrix extending from the lunula to the hyponychium.4 It was originally thought that the germinal matrix is primarily responsible for the growth of the nail, with a significant contribution from the sterile matrix.5,6 It is now known that the entire nail bed contributes to the growth and migration of ...