Patterson Classification of Constriction Band Syndrome

Class 1 simple constriction ring
Class 2 associated deformity of the distal part +/- lymphedema.
Class 3 involves distal fusions like syndactyly/acrodactyly
Class 4 involved intrauterine amputation due to the constriction

Classic Ref:

Patterson T. Congenital ring constrictions. Br J Plast Surg. 1961;69:532–569