Finger fractures are among the most common injuries 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.
Fractures of the middle phalanx will be discussed here. Finger anatomy, other common finger injuries, and thumb injuries are reviewed elsewhere. (See "Finger and thumb anatomy" and "Distal phalanx fractures" and "Extensor tendon injury of the distal interphalangeal joint (mallet finger)".)
Anatomy of special importance to middle phalanx fractures is described below; a more detailed discussion of finger anatomy is found elsewhere. (See "Finger and thumb anatomy".)
The proximal interphalangeal (PIP) joint and the distal interphalangeal (DIP) joint form the articulations of the middle phalanx (figure 1 and figure 2). These joints are stabilized by a volar plate, extensor apparatus, capsule, and collateral ligaments. Just proximal to the PIP joint, the flexor digitorum superficialis tendon splits to allow for the flexor digitorum profundus (FDP) to travel through its center (figure 3). The FDP then passes along the palmar surface of the middle phalanx and attaches to the distal phalanx. The FDP enables DIP joint flexion.
The flexor digitorum superficialis (FDS) attaches to the palmar surface of the middle phalanx and is the primary flexor of the PIP joint. Deep to the flexor tendons the volar plate provides stability against hyperextension.