Volar plate avulsion injuries are a type of avulsion injury. The volar plate of the proximal interphalangeal (PIP) joint is vulnerable to hyperextension injury, in the form of either a ligament tear or an intra-articular fracture.

Gross anatomy

The volar plate forms the floor of the PIP joint separating the joint space from the flexor tendon sheath. The volar plate has a ligamentous origin on the proximal phalanx with a capsular insertion onto the middle phalanx. 

Pathology

Hyperextension injury involving the PIP of the finger can avulse the volar plate which is commonly associated with a volar avulsion fracture at the base of the middle phalanx.

When the volar avulsion fracture involves a significant portion of the articular surface, instability and dorsal dislocation of middle phalanx can occur. This is because a greater portion of the stabilizing collateral ligaments is attached to the avulsed fragment.

Classification

Two classification systems are considered most useful for the management of these injuries ⁷:

• Eaton classification

• Keifhaber-Stern classification

Radiographic features

Plain radiography / CT 

A small fragment of bone is avulsed from the volar base of the middle phalanx. If there is significant involvement of the articular surface, this may be associated with dorsal dislocation of the middle phalanx.  

Ultrasound 

May be seen as a small displaced echogenic focus. High-resolution sonography may be useful evaluate palmar plate stability and to assess reduction of edema especially in an acute setting ⁶.

Treatment and prognosis

Overall, a small fracture fragment (<40% articular surface) and/or reducible fracture with <30 degrees of flexion is usually managed conservatively with finger splinting ⁷. A large fragment (>40% articular surface) or >30 degrees of flexion to reduce the fragment and malalignment post-closed reduction are indicators for operative treatment ⁷.