Classification and functional management of congenital central defect of the hand.

Classification of central defect of the hand includes three general categories--Type I (typical), Type II (atypical), and Type III (two, three, and four digit hand). These three types of central defect have one common denominator--central metacarpal deficiency or absence. Otherwise, these three distinct types differ completely in inheritance pattern, characteristic features, bilaterality, and functional management. Functional management of the Type I central defect combines release of the tethered thumb metacarpal from its adduction contracture and simultaneous closure of the cleft using that redundant skin to fabricate a physiologic thumb-index web. Type II reconstructive procedures should be planned to provide as effective a pinch and grasp as possible between the radial and ulnar columns by deepening the central cleft, excising "digital nubbins" and any impinging skeleton, and performing rotational osteotomies of either metacarpal base or both and, occasionally, transfers to provide active digital flexion. Type III reconstructive procedures should release the adducted thumb and fabricate a physiologic thumb-index web along with appropriate releases of syndactyly. In the two-digit hand, rotational osteotomies may increase function.