Bilateral bony prominences at the dorsum of the hand
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Joint space narrowing and osteophytosis noted at the base of the third metacarpal and its articulation with the capitate bilaterally. This is consistent with degenerative changes representing bilateral carpal boss.
No other significant abnormality seen.
Carpal boss is the presence of a bony protuberance at the dorsum of the quadrangular articulation of the carpus, which comprises the second and third metacarpals, the capitate and trapezoid.
Carpal boss has been found in as many as 19% individuals on cadaveric studies. Most of these would have been asymptomatic and it is thought only ~1% cases are symptomatic. It is found to be an issue more commonly in the dominant hand 1.
It is most commonly found to be symptomatic in 20 to 50 year olds with no gender predilection. It is bilateral in up to 20% cases.
Typically patients complain of discomfort of the dorsal carpus particularly with heavy physical or repetitive exertion. Often a degree of impairment of mobility is also present.
For a long time it was presumed to be a degenerative pathogenesis; however, this viewpoint is now contentious. Interestingly, almost two-fifths patients are found to have experienced relevant trauma. Those with an os styloideum also seem to have increased risk.