What is polydactyly?
Polydactyly literally means extra digits. They can be present on the side of the thumb (preaxial) on the side of little digit (post axial) or with central digits (central) which is very rare.
What is preaxial polydactyly?
In medical terms the outer side (the side of thumb) is called preaxial border of the hand. As thumb deformities are on this side all the thumb deformities are termed preaxial. Polydactyly of thumb is also called ‘Duplication of Thumb’.
Most of these cases are unilateral, sporadic, and are not associated with systemic problems.
What investigations are required?
Clinical examination would give most of the details regarding the diagnosis. Additionally X ray is taken to know exact bony level of duplication and adequacy of individual digit.
How is it classified?
Categories are based on the degree of skeletal replication starting from the duplication of distal most bone (class I) to the duplication of basal bone (class VIII).
Important things in the management are whether joints are involved? Whether one digit is better developed than the other?
What is the treatment?
Surgery can correct this problem. The decision regarding the type of operation depends upon the involvement of joints and the adequacy of the digits. In case the individual digits are in-adequate then they are fused together in the centre (each half of new thumb coming from duplicated digits. While if one digit is well formed. That will contribute majority of the new thumb and only minor parts are taken from the smaller thumb.
Case 1: Child with extra thumb. The extra digit needs to be remover to get normal looking hand.