Hard bump on the dorsal of the hand.
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Hypertrophied bony protuberance of the base of the 3rd metacarpal bone and the trapezoid bone with osteoarthritic changes manifesting by narrowing of the dorsal aspect of their joint space and subcortical pseudocystic changes.
Carpal boss may occur secondary to:
- os styloideum (an accessory ossicle of the wrist)
- hypertrophied bony protuberance on the dorsal surfaces of the base of the second or third metacarpals, near the capitate and trapezium, as in this case, there's elongation of the 3rd metacarpal base and the trapezoid bone with secondary pseudoarthrosis.
Degenerative changes at the site of the pseudoarthrosis are also common, as in this case.