The pattern of early healing of canine tibial osteotomies associated
with two different types of external fixation devices was investigated.
Two-plane fixation was significantly more rigid than one-plane fixation in
three of the five loading conditions that were examined. The more rigid
fixation allowed less lateral displacement at the site of the osteotomy,
induced less formation of callus early in the healing process, permitted
direct bridging by osteons more frequently, and provided healing that was
more rigid early in the process of repair. In the later stages of healing
there were no differences in the quantity of callus or in the strength of
the healing bone. In this canine model, external fixation with higher
rigidity resulted in rapid union that differed from the union that resulted
after less rigid external fixation only with regard to porosity, torsional
stiffness, and displacement at the site of the fracture.