Effects of dynamization after interlocking tibial nailing: an experimental study in dogs.

Dynamization of statically locked tibial nails was studied in a canine model. Reamed static interlocking nails were inserted in 16 canine tibiae with unstable osteotomies. At 8 weeks, half were dynamized. At 20 weeks, the tibiae were harvested and studied radiographically, biomechanically, and histologically. Apparent clinical union was present in all tibiae. Complete radiographic bony union was achieved in 13 of 16, with residual radiolucent lines in two tibiae in the static and one in the dynamic group. Biomechanically, dynamization improved stiffness at the fracture site. Histological patterns were similar, but there were trends toward a denser trabecular callus pattern in the dynamized group. The results of this animal study indicate that although dynamization may have a beneficial effect on the quality of early bony healing, static interlocking does not decrease the rate of bony union.