The Resolution
Figure 3 shows PIP hyperextension of the R 5th finger to about 30° beyond neutral.
Initially, sublaxation was suspected, a digital block was performed, and the PIP joint was unsuccessfully reduced.
Post-reduction films showed mild straightening, but persistent PIP joint hyperextension. This patient has a volar plate disruption of her R 5th PIP joint. The volar plate forms the floor of the PIP joint, ligaments at its origin on the proximal phalanx and cartilaginous in its insertion onto the middle phalanx.
A volar plate disruption is usually caused by a hyperextension injury or dislocation of the PIP joint; a mild force may rupture the plate at its distal insertion which will cause a swan neck deformity. Occasionally, a volar plate disruption may also be associated with a fracture of the base of the middle phalanx, which appears on x-ray with a small fragment of bone avulsed form the volar aspect.
As long as the PIP joint is slightly flexed, the joint is considered stable. A lateral x-ray should be done to confirm that the joint is reduced, and the finger should be splinted in a slightly flexed position with follow-up within three to five days with an orthopedist. If the joint remains dislocated, the patient should be referred immediately.
Acknowledgement: Case presented by Gloria Kim, MD, and urgent care Fellow at University Hospitals Urgent Care, Cleveland, OH.