Traumatic volar dislocation of the second, third and fourth carpometacarpal joints: mechanism and manipulation.

Traumatic volar dislocation of the second, third and fourth carpometacarpal joints without associated fracture is extremely rare. A single case, treated successfully by manipulative reduction supplemented with splint immobilization and isometric and isotonic muscle exercise is reported, with restoration of complete anatomical alignment revealed by postmanipulative radiographs. The radiology of carpometacarpal joint dislocation is discussed. The conservative traction-dorsiflexion manipulative reduction for multiple volar carpometacarpal joint dislocations is described and recommended before using open reduction. Based on the case, it is postulated that the mechanism of a carpometacarpal joint dislocation is due to a sudden violent force acting almost perpendicularly to the metacarpal head or heads; the reactive forces create the opposite directed forces as a lever type of strain on the involved carpometacarpal joint and produce the dislocation.