Mallet Finger



Mallet Finger


Steven R. Niedermeier

Hisham M. Awan



INTRODUCTION



  • Mallet finger is an injury to the terminal extensor mechanism at the level of the distal interphalangeal (DIP) joint. This can be caused by either tendon rupture in zone 1 or an avulsion fracture of the distal phalanx with a fragment of bone that remains attached to the tendon.


  • There are two proposed mechanisms of injury.



    • Traumatic impaction blow (Figure 32.1)—the initial step involves an axial force to finger held in extension followed by either one of two steps:



      • Extreme passive DIP joint hyperflexion, which results most commonly in a tendinous mallet finger.


      • Extreme passive DIP joint hyperextension, which results most commonly in a bony mallet finger.


    • Dorsal laceration—less common; sharp or crushing laceration to the dorsal DIP joint


  • Mallet fingers comprise approximately 9% of all tendinous/ligamentous lesions with an incidence estimated at 5.6% of all tendinous lesions in the hand. The literature does not show any gender difference; however, high-energy injuries are seen in younger, male patients and low-energy mechanisms are seen in the elderly.


  • The ulnar three fingers are the most commonly affected digits, and tendinous injuries are more common than bony avulsion injuries.


  • With the loss of the terminal extensor tendon insertion, the central slip receives all of the tension; the volar plate and transverse retinacular ligament attenuate; the lateral bands sublux dorsally; and the proximal interphalangeal (PIP) joint may be forced into extension in chronic injures. The inability to extend the DIP joint and the PIP joint extension is referred to as a swan neck deformity of the finger (Figure 32.2).







FIGURE 32.1 Mechanisms of injury for mallet finger.






FIGURE 32.2 Mechanism of swan neck deformity in the setting of mallet finger. FDS, flexor digitorum superficialis; FDP, flexor digitorum profundis.


EVALUATION

May 7, 2019 | Posted by in ORTHOPEDIC | Comments Off on Mallet Finger
Premium Wordpress Themes by UFO Themes