Causes / typical injury mechanism: Axial force that causes flexion of the distal interphalangeal  joint (DIP) while extended, hyperextension of the DIP, or laceration on dorsal finger. Any of these can lead to rupture of the common extensor tendon, with or without distal phalanx avulsion fracture.

Classic history and presentation: Doing chores around the house, hands-on activity at work, or playing a sport that includes catching a ball (eg, basketball, baseball) that causes flexion or extension of the DIP with deficit in extending the DIP.

Prevalence:

• Age – Usually younger patients who are working / playing sports.
• Sex / gender – Various reports. Can be more common in men during the first 5 decades of life. High impact mechanisms are more common in men, whereas low impact mechanisms are more common in older women.

Risk factors: Hands-on work, sports.

Pathophysiology: Disruption of the distal insertion of the terminal extensor tendon prevents extension of the DIP, leaving the finger with the unopposed pull of the flexor tendons.

Grade / classification system: Doyle's Classification (most commonly used)

I: Closed injury with or without small avulsion fracture
II: Open injury resulting from superficial laceration
III: Open injury resulting from deep soft tissue abrasion that reaches tendon
IV: Mallet fracture

1. Pediatrics – distal phalanx physeal fracture
2. 20%-50% of the articular surface involved
3. More than 50% of the articular surface involved