In a bilateral canine tibial model, the mechanical, radiologic, and histolo
gic characteristics of intercalary allografts stabilized with locked intram
edullary nails were compared with those of allografts fixed with compressio
n plates. Both methods of fixation achieved healing to host bone. Tibiae th
at were plated had more callus with statistically greater mean torsional ri
gidity and strength than those treated with nails (paired t-test, p less th
an or equal to 0.05), On average, tibiae which had been plated had much hig
her bending rigidity than those fixed with locked nails; however, the diffe
rence in means was not statistically significant. Histomorphometric analysi
s showed an overall greater total bone formation in those limbs treated wit
h plates compared to nails (paired t-test, p less than or equal to 0.04), T
he mechanical environment created by the different fixation methods are tho
ught to be responsible for the observed differences in healing pattern. The
traditional concept of fixation for allografts to achieve maximum rigidity
of the construct may not necessarily promote the most appropriate host hea
ling response in all situations, A less rigid fixation method (plates) prod
uced more callus resulting in superior torsional and bending properties. Th
ese data show that in this canine intercalary allograft model, limbs fixed
with plates produced more external callus resulting in stronger, more rigid
healing. (C) 2000 John Wiley & Sons, Inc.