Reconstruction of the type IIIA hypoplastic thumb.

The management of the hypoplastic thumb depends on the degree of bony malformation, soft tissue anomaly, and deficiencies. Type IIIA thumbs have thumb-index web-space narrowing, hypoplasia of the thenar musculature, metacarpophalangeal joint instability, and extrinsic tendon abnormalities. They also have a hypoplastic metacarpal with a stable carpometacarpal joint, differentiating them from type IIIB thumbs which have an unstable carpometacarpal joint due to partial metacarpal aplasia. Whereas type IIIB thumbs are best treated with ablation and index pollicization, type IIIA thumbs are amenable to reconstruction. Many techniques have been described for correction of the variety of deformities found in theses thumbs. The purpose of this article is to present our preferred technique for comprehensive reconstruction of type IIIA thumbs.