Reconstruction of the hypoplastic thumb.

Thumb hypoplasia is characterized by diminished thumb size, metacarpal adduction, metacarpophalangeal joint instability, thenar muscle hypoplasia or aplasia, extrinsic tendon dysplasia, and in the most severe cases, carpometacarpal joint instability or thumb aplasia. Severe thumb hypoplasia and aplasia are best treated by thumb ablation and pollicization of the index finger. Less severe thumb hypoplasia can be reconstructed by a combination of soft tissue release, first web space local flap coverage, metacarpophalangeal joint collateral ligament and capsule reconstruction, extrinsic tendon tenolysis, and muscle or tendon transfers.