Certified Hand Therapist (CHT) Practice Exam

What is the Eaton classification type 2 for sprain/dislocations characterized by?

1. Dorsal dislocation of the PIP joint with avulsion of the volar plate

2. Fracture dislocation with more than 40% articular surface involvement

3. Fracture with dorsal dislocation and an avulsed small fragment

4. Simple sprain without structural damage

The correct answer is: Dorsal dislocation of the PIP joint with avulsion of the volar plate

The Eaton classification type 2 specifically describes a dorsal dislocation of the proximal interphalangeal (PIP) joint, which is characterized by the avulsion of the volar plate. The volar plate is a fibrous structure located on the palmar side of the PIP joint that helps stabilize and limit excessive extension. In this context, when a dorsal dislocation occurs, it usually results from a significant force that causes the dorsal aspect to displace while simultaneously tearing or avulsing the volar plate. Understanding this injury's mechanics is critical for proper diagnosis and treatment, as it distinctly impacts the integrity of the joint and the surrounding structures. By contrast, other classifications refer to different injury types. Fracture dislocations involving significant articular surface involvement or those with dorsal dislocation combined with small avulsed fragments do not fit the criteria specific to Eaton type 2. Additionally, a simple sprain would lack the structural damage inherent in type 2, making it distinct from this classification. Thus, recognizing the specific characteristics of Eaton classification type 2 provides clarity regarding the nature of the injury and informs clinical management.