The aim of this study was to investigate the effect of the rigidity of
external fixation on osteotomy healing based on radiographic,
morphological, histological, and biomechanical analyses of canine tibial
osteotomies treated with more rigid (six half-pins) and less rigid (four
half-pins) unilateral external fixators. Successful healing was obtained in
all tibiae, but the bone-healing mechanisms appeared to be different
depending on the rigidity of the device used. On the side with more rigid
fixation, early clinical union was observed thirty days after osteotomy.
Periosteal callus formation was significantly increased on the less rigidly
fixed side at both ninety and 120 days (p less than 0.05). Fixation
stiffness was found to affect the incidence of pin loosening (p less than
0.01) and of bone porosity (p less than 0.05) at the osteotomy site.
However, new-bone formation and the structural strength of the bone were
not significantly different between the four-pin and six-pin sides. These
results seem to indicate that a longer period is required for fracture
repair and remodeling when external fixation with less rigidity is
used.