The Effects of Rigidity of Internal Fixation Plates on Long Bone Remodeling: A Bio Mechanical and Quantitative Histological Study

Abstract

The effect of rigidity of internal fixation plates on long bone remodeling was studied using two 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 months. The biomechanical results, together with the quantitative histological measurements of the macroscopic architecture, showed that tissue characteristics of the plated bones were similar. However, because of the larger cortical area, the less rigidly plated femora can sustain significantly higher loads and energy before failure. Cortical thicknéss measurements also showed that rigid plate immobilization results in thinning of the cortex of the underlying bone. The experimental results suggest that cortical bone remodels according to functional stress demands, and the osteoporosis secondary to rigid plate protection is consequent to thinning of its cortex.

Key Words:

• internal fixation plates
• stiffness
• osteoporosis
• cortical thinning
• biomechanical properties
• quantitative histology