Review Question - QID 218847

This patient has an irreducible dorsal dislocation of the metacarpophalangeal joint (MCPJ). The most common interposed structure is the volar plate which serves as an attachment site for the A1 pulley.

MCPJ dislocations are typically dorsal and most commonly involve the index finger. MCPJ hyperextension is the most common mechanism of injury, which results in the avulsion of the proximal volar plate from its metacarpal head origin. Simple dislocations without soft tissue interposed are amenable to closed reduction. Complex dislocations with interposed soft tissue require open reduction.

Afifi et al studied 9 cadaveric specimens with simulated dorsal MCPJ dislocation and examined the structures around the MCPJ and their contribution to irreducibility. They found that the volar plate was the primary structure preventing reduction in all specimens and division of it was required for reduction.

Patel et al presented a case report and literature review of volar MCPJ dislocations. They cite the most common soft tissue interposed for volar dislocation are dorsal capsule, volar plate, and a ruptured collateral ligament. They described a unique case where the junctura tendinum was interposed which required open reduction along with repair of the dorsal capsule and radial collateral ligament.

Figure A shows a PA and lateral XR of the hand demonstrating a dorsal dislocation of index MCPJ

Illustration A demonstrates the anatomy of the volar plate and shows the A1 pulley inserted into it.

Incorrect Answers:
Answer 1: The A2 and A4 pulleys are critical to preventing bowstringing, not the volar plate.
Answer 3: The volar plate attaches to the deep transverse metacarpal ligament not superficial.
Answer 4: Describes the sagittal band which is not likely to be interposed.
Answer 5: The volar plate is more likely to be interposed than the FDP.