Anatomical basis for functional treatment of dorsolateral dislocation of the proximal interphalangeal joint.

Dorsolateral dislocation of the proximal interphalangeal (PIP) joint is a common injury to the hand. Closed reduction of the dislocation anatomically realigns the avulsed ligaments; thus patients may be managed non-operatively. Standard treatment involves placement of a dorsal splint to prevent hyperextension and lateral stresses. This allows early active motion of the PIP joint while preventing a flexion contracture. In this fresh cadaver study, the PIP joint in 24 fingers was dorsolaterally dislocated. Four digits had to be excluded from the investigation due to a fracture dislocation with a bony fragment of >40% of the articular surface of the middle phalanx. After closed reduction, seven digits were further studied using the cryosection technique described by Kathrein et al. (1996, Clin. Anat. 9:227-231) to demonstrate the position of the avulsed palmar plate. In another 13 joints, the torn ligaments were examined by gross dissection. In 10 degrees of finger flexion, the avulsed palmar plate lay at its previous attachment to the base of the middle phalanx. The collateral ligament, ruptured at its attachment to the side of the head of the proximal phalanx, returned to its original position and was not interposed in the joint. The split between the collateral ligament and the accessory collateral ligament was also closed. Our data suggest that the ligamentous structures of the PIP joint, namely the palmar plate and collateral ligaments, typically return to their anatomic positions upon simple closed reduction of dorsolateral dislocations in fresh cadavers.