Fusion of the 1st metacarpal with another bone. In contrast to the proximal phalanges of the digits 2 to 5, the proximal phalanx of the thumb is embryologically equivalent to the middle phalanges of the other digits, whereas the first metacarpal is embryologically of phalangeal origin and as such equivalent to the proximal phalanges of the other digits.
Synonyms:
exact_synonym:
First metacarpophalangeal joint synostosis; Fusion involving 1st long bone of hand; Symphalangism affecting the 1st metacarpal