Clinical features of embryological failures.

Swanson (1968) et al. l ) proposed the simplest classification and nomenclature of congenital anomalies of the hand based on embryological failure, and this classification has been adopted by the American Society for Surgery of the Hand, the International Federation of Hand Societies, and the International Society for Prosthetics and Orthotics. In this classification, the failure of formation of parts (arrest of development) is divided into two types: transverse and longitudinal. The transverse defects include all so-called congenital amputations except for amputation with the constriction band syndrome. Longitudinal deficiencies include all deficiencies that are not in the transverse category. The failure of differentiation (separation) of parts is classified into that of shoulder, arm, forearm, and hand. The anomalies of the hand are classified into carpal, metacarpal, and digital, and the digital anomalies are further classified into deformities, symphalangism, syndactyly (simple and complicated), and contracture secondary to failure of differentiation of muscles, ligaments, and capsular structures. The other type of anomalies are duplication, overgrowth (gigantism), undergrowth (hypoplasia), congenital constriction band syndrome, and generalized skeletal abnormalities. The worldwide adoption of such a uniform classification is valuable for monitoring the congenital anomalies of the hand, and is of fundamental help in the research of the causative factors, preventative measures, and methods and outcome of treatment. It also permits comparisons of incidence between different areas and different countries. The embryologic failure, however, is not clear, and we have found that etiologic groupings made according to this classification, in some cases, are difficult and misleading. Since 1976, I have had a great interest in the clinical similarity of cases otherwise distinguishable by appearance such as typical cleft hand and webbing of normal fingers, and have reported a few conclusions.24)