Partial duplication of the distal 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) to a partially fused appearance of the two bones.
Comment:
Note that with bifid distal phalanx, the terminal phalanx of the thumb is clefted but is still one bone. With duplication of the terminal phalanx of the thumb, the distal phalanx is split into two bones that are located side by side. With triphalangeal thumb, the thumb has three phalanxes located one after the other.
Synonyms:
exact_synonym:
Bifid distal phalanx of thumb; Bifid terminal phalanges of thumbs; Bifid thumb distal phalanx; Incipient distal thumb phalanx duplication; Notched outermost bone of the thumb; Notched outermost bone of thumb; Notched terminal thumb phalanx