Review Question - QID 217825

This patient has sustained a simple, dorsal dislocation of the thumb metacarpophalangeal joint (MCPJ). The preferred closed reduction maneuver is wrist flexion with a volarly directed forced applied to the dorsal aspect of the proximal phalanx (Answer 5).

MCPJ dislocations are rare injuries caused by a fall and subsequent hyperextension of the MCPJ. Dorsal dislocations are the most common variant, and the index finger, followed by the thumb, are the two most commonly involved digits. Initial treatment is closed reduction, which is often successful unless there is concomitant soft-tissue interposition. The most common mistake during attempted closed reduction is the application of longitudinal traction, which risks displacing the palmar plate into the MCPJ, thus rendering the dislocation irreducible. Dislocations which cannot be close reduced must be brought to the operating room for open reduction, through either a dorsal or volar approach.

Dinh et al. provide a review of MCPJ dislocations. They note that the preferred closed reduction technique is wrist flexion (to relax the intrinsic and extrinsic flexors) with a direct volarly directed force applied to the proximal phalanx. The authors stress the importance of the avoidance of longitudinal traction. They note that if surgery is required, a dorsal approach may lessen the risk of iatrogenic damage to the radial digital nerve.

Becton. et al outline their preferred method for approaching the irreducible dislocation of the MCPJ. They note that a direct dorsal longitudinal approach allows for full visualization of the likely interposed palmar plate and go on to state that reduction can be achieved through a longitudinal split of the palmar plate.

Figures A and B are a lateral and anteroposterior radiograph of the thumb demonstrating a dorsal MCPJ dislocation.

Incorrect Answers
Answers 1 and 2: Closed reduction often requires wrist flexion in order to relax the intrinsic and extrinsic flexors. Wrist extension would likely impede closed reduction.
Answer 3: A dorsally directed forced would not reduce a dorsal dislocation.
Answer 4: Longitudinal traction will likely cause interposition of the palmar plate, thereby blocking closed reduction attempts.