Classification of the pattern of intrauterine amputations of the upper limb in constriction ring syndrome.

Twenty patients with congenital upper limb amputations caused by constriction rings were reviewed to classify the pattern of these amputations. In the 20 patients studied, 31 upper limbs had congenital amputations. The pattern of amputation was classified into three types. Proximal upper limb amputation was considered type I and was only seen in one limb. The most common pattern of amputation was digital amputation associated with "coning" or "superimposition" of the digits (type II) and was seen in 20 hands. Type II amputations were subclassified according to the involvement of all, ulnar, radial, or central digits by the constriction ring. In type III amputations (N = 10 limbs), there was no associated coning or superimposition of the digits. This type of amputation was subclassified into type IIIA (multiple-digit amputations within the same hand) and type III B (single-digit amputation). Associated anomalies are reviewed and the pathogenesis of constriction rings is discussed.