has part has part characteristic of inheres in towards has modifier Metacarpal synostosis Synostosis involving the 1st metacarpal 2009-01-30T04:26:41Z Symphalangism affecting the 1st metacarpal UMLS:C4021397 First metacarpophalangeal joint synostosis Fusion involving 1st long bone of hand HP:0010032 HP:0005614 HP:0009703 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. Abnormal 1st metacarpal morphology abnormal fused with metacarpal bone of digit 1