Healing of plated femoral osteotomies in dogs. A mechanical study using a new test method.

We investigated changes in whole bone flexural rigidity during healing of plated osteotomized beagle femora. Using a recently developed mechanical method, healing femora and their intact contralateral controls were tested in non-destructive bending in 24 planes at 15 degree angular increments. The elliptical distributions of flexural rigidity were used to define 4 parameters which describe the mechanical status of a healing bone relative to its control. Plates of 3 different rigidities were used in 21 beagles; 6 for 2 months and 15 for 6 months. 2 healing efficiency parameters, describing bone rigidity, indicated that plated femora may never reach the rigidity of their controls. One of the parameters, describing bone asymmetry, showed that changes in bone asymmetry occurred early in the healing process. Results at 6 months showed no differences in rigidity and asymmetry of bones plated with the different plates. This is attributed to antagonistic effects of axial and flexural rigidities of the plates on bone healing. Our results indicate that the method may be useful for bone healing research.