Dislocations of the Pip Joint

The mechanism of injury in dorsal dislocations is usually PIP joint hyperextension combined with some degree of longitudinal compression, which frequently occurs in ball-handling sports if the tip of the digit is hit with the ball. In the majority of cases, dorsal dislocation produces a soft tissue or bone injury to the distal insertions of the three-dimensional ligament-box complex. The greater the longitudinal force, the more likely the volar lip of the middle phalanx will be sheared off or impacted, producing a fracture-dislocation. On rare occasions, the volar plate ruptures proximally and can become interposed, perhaps with an osteochondral fragment, between the head of the proximal phalanx and the base of the middle phalanx. This results in an irreducible dislocation and necessitates an open reduction. 13,36,55,57,82,84 The volar fracture fragment may even become trapped within the flexor sheath and inhibit motion. 29 Dorsal displacement of the middle phalanx produces specific lesions of the ligament system that can be classified into three major types (Fig. 9-4). Each lesion represents a specific disruption of this ligament-box complex. Types I (hyperextension) and II (dorsal dislocation) rarely require surgical treatment, whereas type III (fracture-dislocation) injuries may require a more intensive, often surgical, treatment regimen.