Congenital central ray deficiency in the hand- a survey of 59 cases and subclassification.

Eighty-nine hands were studied in 59 patients with central ray deficiency. A subclassification into two subgroups was established based on the clinical and radiological findings-subgroup I: typical type and subgroup II: (atypical type) with type a, syndactylous type, and type b, polydactylous type. In subgroup I, the sequential severity of deficiency ranged from a partial defect of phalanges of the middle finger to a monodigit hand. The central digital elements were fused to adjacent digital rays in subgroup II-type a. Supernumerary bony elements were seen in subgroup II-type b. The close relationship between central ray deficiency, syndactyly, and polydactyly was discussed from the standpoint of development of the hand. The classification of central ray deficiency into the longitudinal deficiency category of the International Classification of Congenital Limb Malformations was recommended.