Congenital malformations of the hand and forearm in children: what radiologists should know.

Congenital upper limb malformations represent complex pathologies because of their varied clinical presentations, imaging features, and etiologies. They can be divided into (1) failure of formation with transverse, intercalary, and longitudinal (preaxial, postaxial, and mesoaxial) deficiencies, (2) failure of differentiation with synostoses, carpal coalitions, syndactylies, and symphalangism, (3) duplication with ulnar dimelia and polydactylies, and (4) brachydactylies. Congenital Madelung's deformity, clinodactyly, camptodactyly, and Kirner's deformity are usually included in these malformations. Despite advances in molecular diagnosis, a good knowledge of clinical and imaging features as well as special consideration of other skeletal or nonskeletal abnormalities are essential to eventually diagnose an embryo fetopathy (maternal valproate treatment, constriction band syndrome), a genetic disorder (trisomy 21 or Down syndrome, Turner's syndrome, Holt-Oram syndrome), or a nongenetic syndrome (vertebral, anal, cardiac, tracheal, esophageal, renal, limb association, Poland's syndrome). Genetic counseling for a child presenting with a congenital upper limb malformation is of great value, both for the treating team and the parents, and imaging is often required. The latter is still largely supported by conventional radiography, both for diagnosis and functional prognosis, but ultrasound and magnetic resonance imaging will be great tools in the near future to better evaluate these conditions.