Volar dislocation of second, third, and fourth carpometacarpal joints: a rare and easily missed diagnosis
© The Author(s) 2012
Received: 10 May 2011
Accepted: 31 January 2012
Published: 6 March 2012
Volar carpometacarpal dislocation is a rare form of hand injury that can be easily missed without applying a high level of suspicion and performing a meticulous examination. In this case report, we present a rare case of compound volar dislocation of the second, third, and fourth carpometacarpal joints in a 40-year-old male. This was managed by closed reduction and the use of a mini external fixator. The patient regained a good range of motion in 6 weeks with no pain. It is important to diagnose and treat this injury in order to avoid the considerable morbidity associated with this condition.
Volar carpometacarpal dislocations of the fingers of the ulnar side of the hand are a relatively uncommon injury [1, 2], but those involving the middle three metacarpals are rarer still. Diagnosis of this unusual form of injury requires a high level of suspicion, careful examination, and good radiography. Dislocations at the finger carpometacarpal joints are usually high-energy injuries that are commonly seen in boxers and motorcyclists [3, 6]. The diagnosis can easily be missed due to other serious injuries. These injuries account for <1% of all hand injuries  and are frequently overlooked or missed. Disability of the hand is severe in untreated cases or in those where treatment has been delayed. Volar dislocations of these joints have been reported on rare occasions, but to our knowledge no such dislocations of just the second, third, and fourth carpometacarpal joints have been placed on record. The case presented here is therefore of significant interest.
Carpometacarpal dislocations are seen following high-energy trauma. The increased mobility on the ulnar side may predispose to the noted greater frequency of injury. The mechanism of injury in our case would have been a direct thrust over the knuckles that forced the metacarpals to rotate from the dorsal to the volar direction, causing dislocation of the middle three carpometacarpal joints.
The joints between the carpal bones and the second, third, fourth, and fifth metacarpals are all of the modified saddle type. The second and third metacarpals form the rigid central pillar of the hand and are firmly joined to the relatively immobile carpus through their irregularly shaped carpometacarpal articulations. Stability at the finger carpometacarpal joints is provided by a system of four ligaments. They are the dorsal metacarpal, the palmar metacarpal, and the two sets of interosseous ligaments . These injuries are frequently missed initially because of gross swelling of the hand and because overlap on the lateral X-ray obscures the accurate depiction of the injury pattern. Therefore, at least one variant of an oblique view is required for diagnosis in cases with a high level of suspicion . Treatment includes closed reduction, which is usually successful in dislocations <10 days old, and an unstable reduction can be held with percutaneous Kirschner wires. When 3 weeks or more have elapsed since the injury, open reduction will be necessary .
To the best of our knowledge, this is the first case of the volar dislocation of the middle three carpometacarpal joints to be reported in the literature. Volar carpometacarpal dislocation is a rare form of hand injury and can easily be missed without applying a high level of suspicion and performing a meticulous examination. All three radiographic views are necessary to make a diagnosis and to avoid the considerable morbidity associated with this condition.
Conflict of interest
The patient provided his consent to the publication of this case report.
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