EFFECTS OF RIGIDITY OF INTERNAL-FIXATION PLATES ON LONG BONE REMODELING - BIOMECHANICAL AND QUANTITATIVE HISTOLOGICAL STUDY

The effect of rigidity of internal fixation plates on long bone [dog] remodeling was studied using 2 types of plates with considerable differences in stiffness. The plated bones were subjected to bioengineering, quantitative histological and cortical thickness studies after 9 and 12 mo. The biomechanical results, together with the quantitative histological measurements of the macroscopic architecture, showed that tissue characteristics of the plated bones were similar. Because of the larger cortical area, the less rigidly plated femora sustain significantly higher loads and energy before failure. Cortical thickness measurements also showed that rigid plate immobilization results in thinning of the cortex of the underlying bone. Cortical bone apparently remodels according to functional stress demands; the osteoporosis secondary to rigid plate protection is consequent to thinning of its cortex.