Accessory thumb(s)

This code describes the congenital presence of an extra digit or digits on the thumb side of the hand, often appearing as a small, rudimentary projection or a fully formed, duplicated thumb. This anomaly, also known as preaxial polydactyly, can vary in severity and anatomical completeness.

Use this code for patients diagnosed with a supernumerary thumb, regardless of its size or functional capacity. Documentation should clearly specify the presence of an accessory thumb, often noted during a physical examination or imaging studies. This code is appropriate for initial diagnosis, surgical planning for excision, or follow-up care related to the accessory digit.

• Differentiate from postaxial polydactyly (extra digit on the little finger side), which has a different code.
• Specify laterality (left, right, or bilateral) if documented, using an additional character.
• Consider additional codes for any associated congenital anomalies or functional impairments.