Objective: Duplication of all or part of the first rayComments:
There is a wide spectrum of this malformation. The mild end of the spectrum is a bifid (not cleft) nail or a distal phalanx of the thumb with a central lacuna or bifid tip. Broadened thumbs without a recognizable line of anterior/posterior clefting should be coded as Thumb, broad. Note that finger numbering may be affected by the finding of preaxial polydactyly. See the introductory comments for guidance on digit numbering. It is optional to modify the term by adding partial to a duplicated thumb that involves less than the entire ray (metacarpal and both phalanges) and complete for a digit that has complete duplication of all three bones.