MACROSCOPIC AND MESOSCOPIC BIOMECHANICAL STUDY OF THE FUSION SURFACE AFTER TRIPLE JOINT FUSION OF RIGID CLUBFOOT

This study sought to investigate the macroscopic and mesoscopic biomechanical properties and osteogenic potential of bone tissues at each fusion surface after the triple-joint fusion for rigid clubfoot. Macro and Meso-scale models were established using the sub-modeling approach. The osteogenic potential of bone tissues at each fusion interface was analyzed at both macro- and meso-scales under normal physiological conditions of the foot. Additionally, the mechanical properties of mesoscopic bone units were compared with those of macroscopic cortical bone. The results showed that the stress on the calcaneocuboid fusion surface was higher than that on the talonavicular and talocalcaneal fusion surfaces at both scales, with peak stress occurring in the dorsiflexion condition. The stress levels varied among the fusion surfaces. Notably, there were contralateral differences in the stress levels of the bone units at the three fusion surfaces, with the lateral plate of the calcaneocuboid fusion surface exhibiting greater stress differences than the other fusion surfaces. The stress in the mesoscopic structure was about 1.265–9.657 times greater than that in the macroscopic structure. The calcaneocuboid fusion surface exhibited superior osteogenic properties and frequent dorsiflexion was found to promote bone growth. Significant differences in the osteogenic properties were observed among the fusion surfaces, with symmetrical growth of osteoblasts differing among the fusion surfaces, particularly favoring the calcaneocuboid fusion surface. Moreover, a stress amplification relationship was found between the mesoscopic bone units and the macroscopic cortical bone. Overall, these findings validate the surgical protocol employed in this study and highlight the enhanced clinical outcomes associated with its application.