The plated femur: relationships between the changes in bone stresses and bone loss.

Calculations were made of the alterations in the in vivo cyclic bone stresses due to the application of various plates on the canine femoral shaft. The plate configurations analyzed were those used by previous investigators when studying the influence of plating on bone remodeling. The magnitude of the reduction in the loads borne by the bone tissue and the degree of shift in the bone stress neutral axis during the stance phase of gait was influenced by the geometry of the plate, the plate elastic modulus, and the location of plate application. From a correlation of the calculated alterations in bone stresses with the resulting measured changes in bone mass, it appears that bone remodeling is very sensitive to small changes in cyclic bone stresses. Changes in cyclic bone stresses of 1 MPa (less than 1 percent of the ultimate strength) can cause measurable differences in bone remodeling after a period of a few months.