Pathophysiology: Proper understanding of the anatomy of the nail and distal finger are important for this topic. The perionychium consists of the nail, nail bed, and surrounding skin. The lateral nail folds are termed the "paronychium." The tissue distal and palmar to the nail plate is termed the "hyponychium." The dorsal nail fold and the skin proximal to it are termed the "eponychium." The tissue under the nail plate consists of 2 parts: the lunula and the matrix. This tissue adheres to both the underside of the nail plate and the periosteum of the distal phalanx. The lunula is the white part of the proximal nail. The matrix is the most important part of the nail complex and is distal to the lunula. The matrix consists of 2 parts: the sterile and germinal matrices. The sterile matrix adheres to the underside of the nail. The germinal matrix is more proximal than the sterile matrix and is responsible for the development of the nail itself. Preservation of this germinal matrix is of the utmost importance when repairing nail bed lacerations.
Classic history and presentation: Three types of traumatic nail injury are discussed in this article: subungual hematoma, nail bed laceration, and nail bed avulsion. These injuries may present alone or concomitantly, often with associated bony / ligamentous injury of the distal phalanx and/or DIP joint.
The presentation of distal finger injuries typically includes recent history of trauma to the distal finger (eg, hitting the finger with a hammer or closing it in a door). The patient will complain of marked distal finger pain that is exacerbated by movement of the finger as well as palpation of the distal finger.
- Subungual hematoma – Bleeding underneath the nail.
- Nail bed laceration – Laceration of the nail and underlying matrix. The nail is variably intact, and there is typically a hematoma involving more than 50% of the nail bed surface area.
- Avulsion of the nail – The nail and a portion of the underlying matrix are traumatically removed.
