Classification of avulsion fractures of the volar plate
Avulsion fractures of the volar plate are very common injuries. The Eaton classification is useful and practical, as follows:
Eaton type I (hyperextension) These are hyperextension injuries, with a simple avulsion of the volar plate and a longitudinal split in the collateral ligaments.
Eaton type II (dorsal dislocation) Complete dorsal dislocation of the PIP joint and avulsion of the volar plate.
Eaton type III (fracture dislocation) A fracture dislocation with an avulsion fracture
Often, in addition to hyperextension, axial pressure applied to the fingertip, causes longitudinal compression forces on the middle phalanx towards the proximal phalanx; this can lead to an additional impaction fracture.