Two cases of trapezial fractures with associated subluxation of the carpo-metacarpal joint of thumb are presented. In both these cases radiographs revealed an unusual displaced, intra-articular, longitudinal sagittally split fracture of the body of trapezium with associated subluxation of the carpo-metacarpal joint of the thumb. In both these fractures, open reduction and internal fixation with a mini fragment 2.7mm lag compression screw was undertaken. No tendinous augmentation of the inter-metacarpal ligament was performed. A below elbow plaster cast extending up to the inter-phalangeal joint of the thumb was applied for six weeks.

On review at one year, an excellent radiological and functional result has been noted with the patients performing normally at their job, having no limitation of activities of daily living or sporting activities, and reporting no pain or instability symptoms.

Discussion

Vertical fractures typically result from a cleavage through the mid-sagittal axis accompanied by proximal radial subluxation of the dorsal fragment with attached metacarpal, and exacerbated by the pull of abductor pollicis longus tendon. Carpo-metacarpal joint dislocation with an associated vertical intra-articular fracture of the trapezium has been described in the past and has been treated by open reduction and internal fixation with a Kirschner wire, and, in addition reconstruction of the dorsal oblique inter-metacarpal ligament, using a slip of Abductor Pollicis Longus tendon

Summary

Longitudinal injuries of carpo-metacarpal joint of thumb are unstable and are accompanied by subluxation of the thumb metacarpal.If these injuries are not accurately diagnosed and treated, they may cause pain, limitation of motion and/or weakness leading to permanent impairment of function. Fixation with Kirschner wires, Herbert’s type compression screws, or inter-fragmentary lag compression screws may be required in these unstable, displaced fractures. Reconstruction of the intermetacarpal and capsular structures, such as an intermetacarpal abductor pollicis longus augmentation may be required, especially in isolated dislocations, but this may not be necessary in fracture-subluxations (as in our paper), where the metacarpal base and dorsal trapezial fragment remain connected by the dorsal capsule. A temporary additional stabilizing Kirschner wire will ensure inter-metacarpal orientation and relationship.