A biomechanical study of the modified intertrochanteric valgus osteotomy:a three-dimensional finite element analysis

Abstract

Objective To evaluate the differences in biomechanical performance between the traditional Bombelli-type and modified Z-type valgus osteotomies through finite element analysis. Methods The CT images obtained from a standardized composite femur were used to create 4 solid femoral models and hexahedral finite element meshes of intertrochanteric valgus with the preoperative neck-shaft angle at 120°, 110°, 100° and 90° respectively. Four finite element models with the postoperative neck-shaft angle corrected at 150° for each type of osteotomy were then created. Single leg stance was applied in simulated loading on each finite element model, and the material properties were assumed linear, isotropic and homogeneous. The stress distribution in the postoperative femora and fixation plate as well as the normal contact force of the osteotomized plane were analyzed and compared between the 2 types of osteotomy through the 4 models. Results Serious deformity and high local stress near the osteotomized plane were found in Bombel- li-osteotomized femur with preoperative femoral shaft-neck angle at 90° However, no obvious difference in the stress distribution was found among the 4 Z-osteotomy models. The deformity in Z-osteotomy models was less than that in the Bombelli-osteotomy models. Besides, the stress distributed on osteotomized plane in Z-osteotomy was higher than that in the traditional Bombelli-osteotomy when the preoperative femoral shaft-neck angle was 90°. Conclusion The Z-osteotomy may be a better alternative for large range correction of intertrochanteric varus of femur. Key words: Femur; Osteotomy; Biomechanics