Distal radial epiphyseal displacement after impaired distal ulnar growth.

Impairment of growth of the distal end of the ulna was produced in rabbits by excision of the distal epiphyseal plate. This caused a sequence of changes in the distal radial epiphysis consisting of combined increased chondrogenesis and decreased osteogenesis of the radial two-thirds of the distal epiphysis, and decreased chondrogenesis and increased osteogenesis on the ulnar side. At six to nine days postoperatively, cracks appeared concomitant with tilting of the plate and epiphysis, in the epiphyseal plate or at its metaphyseal junction. An incomplete radial epiphyseal separation occurred, a step-like deformity developed in the metaphysis, and an ulnar deviation developed.