Thumb duplication.

Thumb duplication is a complex congenital anomaly. Treatment requires a detailed understanding of the pathophysiology as well as an appreciation of all the components involved. The goals of surgery are to restore the normal anatomic relationships of the residual thumb. Successful reconstruction requires evaluation and correction of the bony axis; articular congruity; size and angulation; intrinsic and extrinsic musculotendinous abnormalities; and ligament, skin, and soft-tissue elements. The reconstructed thumb may not match the normal thumb because of the hypoplasia that is inherently associated with the condition. With careful preoperative planning and attention to detail, however, a satisfactory cosmetic and functional result can be achieved.