Subungual foreign bodies are often difficult to treat. Foreign bodies (e.g., hair, metal splinters, pencil lead, spines, thorns, and wood) may become lodged beneath the fingernail.1-3 Tradesmen (e.g., auto mechanics, carpenters, landscapers, and metal workers) who work without hand protection with materials that produce small splinters are at risk for this type of injury. Subungual foreign bodies may present less commonly under the toenails.
Patients generally present for medical intervention with pain under the nail after unsuccessfully attempting to remove the foreign body. Prior removal attempts often result in breakage of the foreign body or pushing it further beneath the nail. This can complicate the next extraction attempt. Retained subungual foreign bodies if untreated can become infected, cause tissue reactions, and cause granuloma formation. Subungual foreign bodies can be treated rapidly with complete removal of the foreign body and without causing additional patient discomfort.4
ANATOMY AND PATHOPHYSIOLOGY
The distal fingertip and nail apparatus are complex structures (Figure 128-1). 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 plate. The eponychium is the distal portion of the nail fold where it attaches to the proximal surface of the nail plate. The lunula is the white arc seen on the proximal portion of the nail plate. The nail bed consists of the germinal matrix on the proximal ventral floor of the nail fold and the sterile matrix that extends from the lunula to the hyponychium. The germinal matrix is primarily responsible for the growth of the nail. The subungual space is the area immediately beneath the nail plate.
The anatomy of the distal fingertip and nail bed. A. Surface anatomy. B. Midsagittal view.
Foreign bodies may enter the subungual space at the distal fingertip beneath the nail or may penetrate the nail plate (Figure 128-2). Separation of the nail from the nail bed results in severe pain. Patients frequently attempt to remove the foreign body immediately because of this intense discomfort. An infection or foreign body reaction will often ensue if the foreign body is not removed in its entirety.
Subungual foreign bodies can enter from under the distal nail plate or through the nail plate.
Subungual foreign bodies should be removed to prevent the complications of foreign body reactions, infection, and possible nail deformity. Deeply embedded foreign bodies, splintered foreign bodies, those that traverse the nail plate, or contaminated foreign bodies may require the removal of the nail plate ...