Finger fractures are among the most common fractures managed by primary care and emergency clinicians. An understanding of basic finger anatomy and common injury patterns provides the basis for diagnosing and treating these injuries.
This topic review will discuss fractures of the distal phalanx. Finger anatomy and other common finger injuries are reviewed elsewhere. (See "Finger and thumb anatomy" and "Middle phalanx fractures" and "Extensor tendon injury of the distal interphalangeal joint (mallet finger)".)
EPIDEMIOLOGY AND INJURY LOCATION
Distal phalanx fractures represent common sports and work-related injuries, accounting for approximately half of all hand fractures [1-3]. These fractures are commonly caused by trauma or crush injuries. The middle finger is most often affected, followed by the thumb. The distal metaphysis, which anchors the complex nail matrix and nail plate, is often affected by distal fractures.
Anatomy of special importance to distal phalanx fractures is described below. A more detailed discussion of finger anatomy is found elsewhere. (See "Finger and thumb anatomy".)
The range of motion of the distal phalanx is limited in flexion by the flexor digitorum profundus, while extension is limited by the extensor terminal slip. The terminal slip of the extensor tendon inserts on the dorsal surface of the distal phalanx, while the flexor digitorum profundus (FDP) inserts at the volar base of the distal phalanx [4,5]. The FDP tendon causes the distal phalanx to flex after avulsion of the extensor tendon (creating a classic "mallet" deformity). Multiple fibrous septa attach the tuft of the distal phalanx to the volar skin. This contributes to bony stability and minimizes displacement with distal phalanx fractures (figure 1 and figure 2). The nail matrix is the tissue under the nail that permits nail growth and migration. Its longitudinal fibers anchor the dermis to the periosteum of the distal phalanx (figure 3).