A mallet finger commonly occurs after the DIP joint is forcibly flexed against an actively extended finger, tearing the extensor mechanism as it inserts on the distal phalanx. This can occur after a sudden axial blow to an extended fingertip. The patient presents with an inability to actively extend the distal phalanx while maintaining a normal passive range of motion, and the DIP joint remains passively flexed. On radiography, there may be a small bony avulsion fragment on the dorsum at the distal phalanx.
A jersey finger involves an avulsion of the distal phalanx flexor mechanism. The flexor digitorum profundus (FDP) tears because of forced extension of a fully flexed DIP, as would occur when someone grabs the jersey of an opponent while attempting to tackle them. Most commonly, the ring finger is involved. Clinically, the patient presents with an inability to actively flex the DIP joint while maintaining a full passive range of motion. Radiographically, a bony avulsion fragment may be present.
Management and Disposition
A closed mallet finger without involvement of the joint can be treated by splinting the DIP joint in extension; the PIP joint should not be splinted. This splint should be worn continuously for at least 6 weeks. Operative treatment is usually not required. A jersey finger often requires surgical repair; early referral is recommended. Prognosis worsens if treatment is delayed or severe tendon retraction is present.
Mallet Finger. This illustration demonstrates that the unopposed flexion of the DIP joint is secondary to the complete tear of the tendon (A), or an avulsion of a small chip fragment (B).
Mallet Finger. The distal phalanx is held in flexion and the patient is unable to extend it. (Photo contributor: Kevin J. Knoop, MD, MS.)
Avulsion of a significant portion of the mallet finger articular surface (more than one-third) may require open reduction with internal fixation.
The jersey finger involves the FDP tendon at the DIP joint. It may be tested by isolating the affected DIP (ie, holding the MCP and PIP joints in extension while the other fingers are in flexion) and asking the patient to flex the DIP joint.
Mallet Finger. Classic mallet finger—the long finger remains flexed at the DIP joint while the patient is attempting to actively extend his fingers. (Photo contributor: Matthew Kopp, MD.)
Jersey Finger. The normal cascade of flexion is disrupted in the injured hand, consistent with a Jersey finger. (Used with permission from Brunicardi FC, Andersen DK, Billiar TR, et ...