Finite Element Analysis Of The Coronal Reduction Degree Of Femoral Intertrochanteric Fractures

Objective: To compare the biomechanical differences between PFNA internal fixation models under the same physiological load,same fracture type and different degrees of coronal reduction by finite element analysis,in order to provide a biomechanical reference for clinical diagnosis and treatment.Methods: Using the reverse engineering principle,the proximal femur of normal human was CT scanned to build the accurate 3D finite element model of proximal femur.The type A1.2 intertrochanteric fractures were simulated.The 3D finite element models of proximal femur were simulated at 100%,95%,90%,85% and 80% fit degrees of anterior and posterior fracture end placements,respectively,which were assembled with the PFNA internal fixation device to create the integral 3D finite element models.The finite element analysis software was used to study the biomechanical differences between the PFNA internal fixation models under varying coronal reduction degrees of femoral intertrochanteric fractures and to make a comparative analysis.Results: The stress distribution nephograms of the PFNA implants at various anatomical structures of proximal femur were obtained under differing degrees of coronal reduction by finite element calculation.With the gradual decline in the fit degree,the stress imposed on various structures increased gradually,and the stress curves rose.The stress on various sites: main nail > spiral blade > lateral wall > femoral neck > femoral head.Besides,inflexion point appeared at a reduction degree of 80%,and the stress was higher for the posterior fracture end placement than the anterior placement at the same fit degree.Conclusion: After PFNA fixation of intertrochanteric fractures under varying degrees of coronal reduction,the stress curves for implants at various proximal femur sites rose,and inflexion point appeared at an 80% reduction degree.Therefore,in the surgical reduction of intertrochanteric fractures,the degree of coronal reduction should be at least 80%,and anterior placement is preferred over posterior placement,so as to reduce the stress of internal fixation and thereby lessen the problem of spiral blade cut-out.We should not blindly rely on the new internal fixation devices or exaggerate the effect of surgery.Instead,we should choose a reasonable surgical approach according to the patients' conditions and develop a detailed surgical plan to strive for early rehabilitation of patients.