has part has part Complete duplication of proximal phalanx of the thumb Duplication of the proximal phalanx of the thumb 2009-01-29T03:59:56Z HP:0009613 Complete or partial duplication of the proximal phalanx of the thumb. Depending on the severity, the appearance on x-ray can vary from a notched phalanx (the duplicated bone is almost completely fused with the phalanx), a partially fused appearance of the two bones, or two separate bones appearing side to side. In contrast to the proximal phalanges of the digits 2-5, 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. Partial/complete duplication of the proximal phalanx of the thumb UMLS:C4021424 Notched innermost bone of thumb Bifid proximal phalanx of the thumb Abnormality of the proximal phalanx of the thumb Duplication of thumb phalanx Duplication of the middle phalanx of hand