Abduction-pronation and recession of second (index) metacarpal in thumb agenesis

Abstract

Thumb dysplasia imposes a proportionately greater functional deficit than does dysplasia of any other digit. To simulate an opposable unit, the child with but four normal fingers naturally will turn to the next most radial (index) digit and by abducting and pronating will widen his first cleft. When the thumb is absent bilaterally, formal neurovascular pollicization of at least one index digit is the logical choice. The inherent deficiencies in formal pollicization, however, may detract from its use in certain instances, for example, unilateral thumb aplasia or thumb aplasia associated with radial club hand. A simpler procedure performed at age 3 or 4 years avoids many of these deficiencies while still creating a more functional pinch and grasp. Through a small web incision, the index metacarpal is separated from the adjacent metacarpal. The base of the index metacarpal is sectioned and shortened 1.5 cm. The digit is recessed, rotated and abducted radially and palmarly, then immobilized by a K-wire fixation to its base. Since 1960, 17 procedures have been performed with good functional results and acceptable appearance.