Avulsion at the proximal end segment

In the phalanges of the hand, avulsions usually involve the articular surface and are, therefore, partial articular fractures. They are classified according to AO/OTA as 78.2–5.1.1B, where 2–5 indicates which finger is injured. The fractures may be simple or fragmentary.

An avulsion fracture may be associated with a metacarpophalangeal (MCP) joint dislocation.

$Simple and multifragmentary avulsion fractures of the phalangeal proximal end segment$

Avulsion fractures result from side-to-side (coronal) forces acting on the finger, putting the collateral ligament under sudden tension. The ligament is usually stronger than the bone, causing the ligament to avulse a fragment of bone at its insertion.

Avulsion fractures result in marked joint instability. Compare with the contralateral finger.

$Coronal forces acting on finger put the collateral ligament under tension resulting in an avulsion fracture$