Cleft hand.

Definition, incidence, genetics, and etiology of typical cleft hand are discussed in this paper. Cleft hand, central polydactyly, and osseous syndactyly were induced experimentally when the same teratogenic factors acted on the embryos at the same developmental stage. Typical cleft hand, central polydactyly, and syndactyly should be classified together as manifestations of the same entity, that is, failure of induction of finger rays. Typical cleft hand may be further subdivided into five types on the basis of the number of defective finger rays. Treatment of the typical cleft hand involves cosmetic and functional considerations. Reduction of the wide interdigital space is performed primarily for cosmetic reasons, while separation of syndactyly between thumb and index finger and correction of deviation of the thumb is performed for functional improvement. A zigzag incision with a small triangular flap is recommended for reduction of the interdigital space. If metacarpal remnants or cross bones prevent drawing the metacarpals together, they should be removed. The deep transverse metacarpal ligament should be reconstructed by ligamentous flap made out of the flexor tendon sheaths of the index and ring fingers to prevent later spreading of the fingers. A dorsal-based rotation flap fashioned from the skin of the cleft is recommended for the treatment of cleft hand with partial syndactyly of the thumb and index finger. Deviation of the thumb is often caused by a delta phalanx by a trapezoidal-shaped extra phalanx. Deviation of the thumb is corrected by removing the delta phalanx or osteotomy of the trapezoidal phalanx. When the cleft is closed at approximately 1 year of age, spontaneous correction of the flexion deformity of the ring finger is sometimes observed.