Summary
Bilateral transverse mid-shaft tibial osteotomies, with a 4-mm gap, were performed
in purpose-bred research dogs and stabilized using a Securos™ Type 2 external skeletal
fixator (ESF). Full (100%) axial dynamization of one randomly selected ESF in each
dog was performed at 31 days postoperatively. Caudo-cranial radiographs were obtained
at weekly intervals, which were qualitatively and quantitatively evaluated (densitometry
and ImageJ analysis). The dogs were euthanatized 13 weeks postoperatively, at which
time dual energy x-ray absorptiometry (DEXA), peripheral quantitative computed tomography
(pQCT), mechanical testing in torsion, and qualitative histological analysis were
performed. A two-tailed paired Student's t-test was performed for statistical analysis
of all parameters of interest, with significance set at p<0.05. Three of five dynamized
bones bridged quicker, and four of five dynamized bones appeared to have greater callus
formation, however, statistically significant differences could not be definitively
determined. Statistically significant differences were not found with densitometry
(any time frame), DEXA, pQCT, torsional stiffness or maximum torque. Despite the lack
of statistically relevant data, trends were observed with larger callus size and density
in the dynamized tibiae. The dynamized tibiae appeared to fracture more consistently
outside of the area of the healing callus as compared to the control tibiae. Histological
evaluation showed greater remodelling in four of five control limbs when compared
to the dynamized limb. Dynamization at 31 days postoperatively may delay bone remodelling,
despite a trend towards a larger callus size. The results of this study failed to
show a definitive role for early full axial dynamization.
Keywords
Tibial fractures - external skeletal fixation - dynamization
