Os centrale carpi simulating a scaphoid waist fracture.

The os centrale carpi is a relatively rare accessory carpal bone, and its presence may be confused with a scaphoid fracture. A case is presented which simulated an un-united scaphoid fracture on the plain X-ray film. However, CT in the sagittal plane showed two rounded fragments on the dorsum of the scaphoid with smooth, regular cortical margins differing from an acute scaphoid fracture. Their volume combined with the volume of the scaphoid is more than that of a completely normal scaphoid. There is no evidence of degeneration in the two rounded fragments and scaphoid. Because of these features, the diagnosis of soft tissue injury with an incidental finding of an os centrale carpi was suggested.