Reconstruction of the hypoplastic thumb.

Blauth has classified congenital hypoplasia of the thumb into five grades. Grade I requires no treatment. Grade II can be reconstructed by widening the first web space with various flaps, stabilizing the metacarpophalangeal joint, and performing an opponensplasty. In such cases, a pollex abductus configuration of the flexor pollicis longus should be sought, and if found, corrected. Grades III, IV, and V require pollicization, a procedure that has become more sophisticated by attention to skin flap design, intrinsic transfer, and positioning of the head of the second metacarpal. Partial aplasia should be treated by phalangization, distraction lengthening with free toe phalanx transfer, on-top plasty, or toe-to-hand transfer. The last is made more complex by the anomalous anatomy frequently present in aplasia. Reconstruction of the infant thumb should be complete before the first birthday.