Palmar dislocation of the PIP joint with fracture:

D. If not splinted properly, will cause a boutonniere deformity.

DISCUSSION: Palmar dislocation of the PIP joint is much less common than dorsal dislocation. Palmar dislocation of the PIP joint can disrupt the central slip of the extensor mechanism at the proximal part of the middle phalanx and can disrupt the dorsal capsule in addition to the palmar plate. If the joint is stable after reduction it is treated by splinting to immobilize the PIP joint in extension, while the DIP is allowed to actively flex. If not splinted properly, this injury can cause boutonniere deformity with resultant loss of normal PIP extension and hyperextension of the distal joint.