Historical Overview
- In 1939, Kaplan first discussed the pure extension injury at the proximal interphalangeal (PIP) joint.1 Volar plate instability may stem from an injury at the PIP joint. In some cases, this injury tears the attachment of the volar plate or results in a volar plate avulsion fracture from the base of the middle phalanx.
Description
- The volar plate is a capsular ligament that is usually injured at the PIP joint. It may also involve the carpometacarpal (CMC), metacarpophalangeal (MP) and distal interphalangeal (DIP) joints.
- An unstable PIP joint fracture includes >40% of the joint surface.
- The volar plate becomes the main stabilizer to lateral deviation when the collateral ligaments are torn.2
Pathophysiology
- Volar plate stability can be affected by PIP joint injuries or dislocations. These injuries, which often occur in athletic activities, usually damage the volar plate at its attachment to the middle phalanx. If PIP joint injuries are insufficiently treated, this may result in joint stiffness, persistent subluxation, and degenerative changes.3
- Volar plate instability may occur in conjunction with collateral ligament injuries.
- As in other fractures, children demonstrate more rapid and effective healing than do adults with PIP joint injuries involving the volar plate.4
Instructions
- Record the patient’s history, including any sports-related injuries. Ask the patient to rate how much pain s/he usually experiences in the affected finger on a scale from 1 to 10.
- Palpate the volar plate area for tenderness and edema.4
- Measure the stability of the PIP joint by comparing the injured joint to the uninjured joint in the contralateral hand. For instance, the right, uninjured, ring finger PIP joint may extend 5° when the volar plate is stressed, while the injured, left, ring finger PIP joint may be tender and hyperextend 60°. This hyperextension verifies a left ring finger volar plate injury.2
- In cases of PIP dislocation, examine the finger under digital or wrist block anesthesia, to relieve pain.2
Variations
- If there is a fracture, determine how much of the PIP joint surface is involved to decide whether operative treatment is required. Type III injuries, with disruption of >40% of the joint surface, indicate a need for surgery.
Related Signs and Tests
- Plain radiographs with a true lateral X-ray
Diagnostic Performance Characteristics
- If the volar plate injury occurs with a fracture, and the examination shows excessive hyperextension with tenderness, take true lateral radiographs. This will improve the reliability of a diagnosis of volar plate instability.
