[Triphalangeal thumb].

Triphalangeal thumb is often thought to be a rare congenital abnormality; it has an incidence of 1 in 25,000 births. We reviewed 49 triphalangeal thumbs in 28 Mexico City patients at the Diaz Lombardo Hospital from 1974 to 1979, Shriners Hospital from 1979 to 1982, Instituto Nacional de Ortopedia from 1981 to 1982, and at the ABC Hospital from 1971 to 1998. A total of 21 patients (75%) had bilateral deformity. Patients were classified according to Dieter Buck-Gramcko system and Müller teratologic line. All were surgically treated and evaluated with Cheng graduation scale, finding good results in 48 patients (97%), fair results in one (3%), and no poor results.