Experimental nonunion in dogs.

A consistently reproducible nonunion was produced in mongrel dogs by resecting 3 mm of bone and 1 cm of periosteum at the diaphyseal-metaphyseal junction in the radius. Bone wax was used to seal the cut surfaces. No external or internal immobilization was necessary. The animals were sacrificed at various intervals up to one year after the operation. In one subgroup the events were assessed by radiologic and histologic techniques, and in another the limb was examined by microvascular and bone scintigraphic methods. Nonunion of the hypertrophic type occurred in 85% of cases and of the oligotrophic type in 15% of cases. Pseudarthrosis (with persistent mobility, neocapsule, synovial-like fluid, and well-differentiated cartilaginous tissue capping the bone ends) was established by the 28th week.