(See also Overview of Sprains and Other Soft-Tissue Injuries Overview of Sprains and Other Soft-Tissue Injuries Sprains are tears in ligaments; strains are tears in muscles. Tears (ruptures) may also occur in tendons. In addition to sprains, strains, and tendon injuries, musculoskeletal injuries include... read more .)
The usual mechanism is forced flexion of the distal phalanx, typically when hit with a ball. The extensor tendon may avulse part of the proximal aspect of the distal phalangeal bone (see figure Mallet finger Mallet finger Mallet finger is a flexion deformity of the fingertip caused by avulsion of the extensor tendon, with or without fracture, from the proximal end of the distal phalanx. (See also Overview of... read more ). The avulsed part involves the articular surface.
The finger is usually painful and may be swollen and bruised immediately after the injury. Occasionally, blood collects under the nail (called subungual hematoma Subungual hematoma and nail bed trauma Deformities are often considered together with dystrophies, but the two are slightly different; deformities are generally considered to be gross changes in nail shape, whereas dystrophies are... read more ).
The affected dorsal interphalangeal (DIP) joint rests in a more flexed position than the other DIP joints and cannot be actively straightened but can easily be passively straightened, usually with minimal pain.
Treatment of Mallet finger is with a dorsal splint that holds the DIP joint in extension for 6 to 8 weeks; during this time, the tip cannot be allowed to flex (eg, when cleaning the finger).
Fractures that involve > 25% of the joint surface or that cause joint subluxation may require surgical fixation.