The carpal boss is an unmovable hypertrophied bony protuberance at the base of the second or third metacarpals on the dorsal surface, near the capitate and trapezium.
The condition may represent either or a combination of:
- degenerative osteophyte formation
- os styloideum (an accessory ossicle of the wrist)
- bony prominence at the base of the second or third metacarpals
The radiographic appearance of a carpal boss is characteristic, however optimal visualisation of the boss may be difficult to obtain due to superimposed bony structures.
CT may show degenerative disease at a pseudo-arthrosis, and MRI will show oedema related to abnormal motion.
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