Review Question - QID 219826

This 22-year-old male sustained a dorsal left index finger metacarpophalangeal joint dislocation. Subsequently, he underwent an attempted reduction, during which the volar plate was likely interposed secondary to excessive traction (Answer 3).

Metacarpophalangeal joint (MCPJ) dislocations are uncommonly encountered, especially when compared to interphalangeal joint (IPJ) dislocations. Similar to IPJ dislocation, the most common direction is dorsal and can be broken down into simple (closed reduction is possible) and complex (requiring open reduction). Open reduction is often required due to interposed soft tissues, the most commonly interposed structure being the volar plate. This occurs frequently with excessive or exclusively longitudinal traction. Closed reductions can be achieved by applying direct pressure over the dorsal aspect of the proximal phalanx with the wrist in flexion while applying gentle longitudinal traction. This prevents over-distraction of the joint, reducing risk for volar plate interposition.

Becton et al. provide a novel technique for reducing complex dislocations of the MCPJ, involving a midline dorsal approach to the MCPJ in order to provide adequate visualization of the interposed volar plate. The authors recommend splitting the volar plate longitudinally, facilitating spontaneous reduction of the metacarpal head. The authors conclude this approach is advantageous as it allows for full exposure, is less likely to injure the digital nerves compared to the palmar approach, and can also allow for fixation of any osteochondral lesions associated with the dislocation.

Green and Terry review the associated anatomy seen with complex dislocations of the MCPJ. The authors reported on nine patients who sustained complex MCPJ dislocations. They note that the volar plate is the single most important structure that prevents the reduction of MCPJ dislocations. The authors recommend allowing immediate range of motion following open reduction to restore full range of motion.

Figures A, B, and C represent AP, oblique, and lateral radiographs of a left hand demonstrating a dorsal MCPJ dislocation of the index finger without any bony abnormalities. Figure C is a cross-sectional diagram highlighting the anatomy of the metacarpal head.

Incorrect Answers
Answer 1: Structure 1 represents the deep transverse metacarpal ligament
Answer 2: Structure 2 represents the sagittal band
Answer 4: Structure 4 represents the proper collateral ligament
Answer 5: Structure 5 represents the dorsal capsule/deep articular extensor tendon fibers