Joseph A. Rosenbaum
Hisham M. Awan
Dislocation of the metacarpophalangeal (MCP) joint secondary to trauma
Force applied to the MCP joint exceeds the strength of its capsuloligamentous support.
Mechanism of injury
Mechanisms of injury include torsional, angular, and tractional forces across joint.
Dorsal dislocations may be caused by forced hyperextension.
Dislocation may be part of a more severe overall injury pattern including soft tissue injury to ligament, tendon, nerve, and/or vessels.
Dislocations of MCP joints are not very common.
Often seen in laborers or athletes
Males are affected more than females.
Typically caused by trauma, either direct or indirect
Presentation is usually acute due to deformity and pain.
May be overlooked initially in polytrauma cases
Digit may be held in extension at the MCP with flexion at proximal interphalangeal and distal interphalangeal.
Palmar skin puckering indicates a complex dislocation.
Assess for edema, angular deformity, rotational deformity, and quality of soft tissues.
Identify any lacerations, and rule out open dislocation.
Assess sensation and capillary refill distally.
Assess the other digits as well as the hand and wrist.
Obtain hand radiograph if MCP joint dislocation is suspected.
Brewerton view may help to identify fractures or joint dislocation.
Identify any fractures if present.
As with other dislocations, the nomenclature of direction of dislocation is based on which way the distal bone dislocates relative to the proximal bone.
Dorsal dislocations—P1 is dislocated dorsally relative to the metacarpal head.
Volar dislocations (uncommon)—The proximal phalanx (P1) is dislocated volarly relative to the metacarpal head.