Keifhaber-Stern Classification The Keifhaber-Stern classification was proposed originally by Hastings and later modified by Keifhaber and Stern in 1998. This classification, along with the Eaton classification, is the most widely accepted classification at the time of writing (August 2016) for the management of volar plate avulsion injuries of the PIP joint 1. According to this classification, there are three types of volar plate avulsion injury: stable avulsion fracture involving <30% of the articular base of the middle phalanx tenuous avulsion fracture involving 30%-50% of the articular base of the middle phalanx; reduces with <30° of flexion unstable avulsion fracture involving <50% articular base of the middle phalanx but requires >30° flexion to maintain reduction Eaton Classification Type I: hyperextension mechanism, avulsion of the volar plate, and a longitudinal tear of the collateral ligaments[rx] The opposing joint surface remains congruent Type II: dorsal dislocation of the PIPJ, avulsion of the volar plate; complete tear of the collateral ligament Type IIIa: fracture-dislocation with an avulsed small fragment. <40% of the articular surface The dorsal aspect of the collateral ligament remains attached to the middle phalanx Type IIIb: fracture-dislocation with fracture, impaction of the articular surface of more than 40% Keifhaber-Stern Classification Stable: Avulsion fracture involving <30% articular base of the middle phalanx[2] Tenuous: Avulsion fracture involving 30%-50% articular base of the middle phalanx; reduces with <30° of flexion Unstable: Avulsion fracture involving <50% articular base of the middle phalanx but requires >30° flexion to maintain reduction