Microsurgical reconstruction of the hypoplastic thumb, type IIIB.

If a classically hypoplastic thumb, type IIIA, presenting with a first carpometacarpal joint, is amenable to reconstruction, a type IIIB case without the basal joint, is classically treated by pollicization. The authors concur with this opinion, but found two circumstances in which reconstruction is an option in a type IIIB thumb, either when an adolescent asks for improvement of an unstable but utilized thumb, or when a parent definitely refuses pollicization. In such cases, a free, vascularized metatarsophalangeal joint is the first step of the reconstruction, followed by classic non-microsurgical steps. The authors reviewed five cases, with a mean follow-up of 7.8 years. Hypoplasia of the reconstructed thumb, and a limited pinch, allow this option only with restricted indications.