There is a number of lesions produced by a hyperflexion mechanism.
All of these are characterized by detachment of the central slip of the
extensor apparatus. They are considered as acute boutonnière injuries.
Lesions without dislocation
- Hyperflexion with detachment of the central slip (no fracture)
- Simple avulsion fracture of the central slip with a small nonarticular
- Simple avulsion fracture of the central slip with a larger articular