Multiple carpometacarpal dislocations

Clinical History

A 17-year-old male presented to the accident and emergency department with a swollen and painful right hand, after he punched a wall with his fist, following an argument.

Imaging Findings

On examination, there was deformity found on the ulnar side of the dorsal aspect of the hand. Associated with the significant swelling, a hollow was noted at the base of the 5th metacarpal, with restricted movements at the wrist joint. No distal neurovascular deficit was noted. Plane X-rays were suggested (please refer to the image). This pure dislocation at the carpometacarpal joints of the ring and the little finger was managed with manipulation under anaesthetic, using K wiring and POP plaster. He was reviewed at the clinic one month later, and the injury was noted to be stable with no obvious complications.

Discussion

Multiple dorsal dislocations of the carpometacarpal (CMC) joints is a rare diagnosis. It requires a high index of suspicion, careful examination and good radiography. The patterns of injuries encountered at the CMC joints of the ring finger and the little finger can be explained by the direction and force of the applied load, the position of the CMC joint at the time of loading and the constraints imposed by specific CMC ligaments. The complexity of these injuries is greater than was previously recognised [1]. Swelling, deformity and the presence of a palpable lump are the main clinical features. Various tests such as the “Indian salutation test” are described [2]. The patient may present with complications such as transient motor neuropraxia of the ulnar nerve or compartment syndrome, especially after crush injuries. These injuries are always combined with significant soft tissue damage. The X-ray findings, which are the key to a diagnosis, are a loss of parallelism, an interruption of the so-called M line and the overlapping of articular surfaces [3]. The “true” lateral radiograph of the hand is a technique which has improved the diagnosis of CMC dislocations. Measurement of the angle between the long axis of the 2nd and 5th metacarpal bones, in cases of 5th metacarpal dislocation, is advocated, as the CMC angle is increased compared with controls ( 38.5º as opposed to 9.8º ) [4]. A smaller increase is suggestive of subluxation and should be evaluated under anaesthesia. Oblique views, with the forearm pronated 15º and 45º also provide a good view of the extent of the 4th and 5th CMC injury [5]. CT scans taken in the longitudinal and the longitudinal-oblique axis best display the ulnar CMC joint surfaces and their relationship to each other, and are recommended where the clinical evidence of an injury is not in keeping with the plain radiographic findings, and when planning a complicated surgery [6]. The treatment is controversial and is based on the presence or absence, of associated fractures. It either consists of close reduction and temporary K wire fixation or open reduction and internal fixation.

Differential Diagnosis List

Final Diagnosis

Mulitple dislocations at the CMC joint of the ring finger and the little finger.

URL:	https://www.eurorad.org/case/3456
DOI:	10.1594/EURORAD/CASE.3456
ISSN:	1563-4086