Finite Element Analysis Of The Optimal Amount Of Bone Cement In The Treatment For Elderly Patients With Severe Osteoporotic Intertrochanteric Evans Ⅱ Fracture With Reinforced Screws

Objective: To explore the optimal amount of bone cement in the treatment of severe osteoporotic intertrochanteric Evans Ⅱ fracture with reinforcing screws.Methods: The CT data of a patient with left femoral intertrochanteric fracture were selected,and the three-dimensional model of the right femur was constructed by importing mimics 20 and Geomagic Wrap 2017 software.The right femur model of bone cement was simulated and established by Geomagic Wrap 2017 software.Use Solidworks 2017 software to establish the reinforced screw model,and assemble and combine the three-dimensional model of the right femur and the reinforced screw model according to the conventional standard reinforced screw surgery technology;Then,geomegicwrap2017 software was used to simulate Evans Ⅱ fracture on the combined model,and the model with different amount of bone cement of reinforced screw was constructed to assemble with Evans Ⅱ fracture model,and the load was applied.Part of the cancellous bone around the proximal end of the strengthening screw was cut and redefined as bone cement components.According to the amount of cement wrapped,it was named as five model groups: A model(2m L),B model(3m L),C model(4m L),D model(5m L),E model(6m L).After setting the material parameters,boundary conditions,and applying the load,it was stored as a K file,which was imported into ansys 2019 software for finite element analysis.Observe and compare the cutting of the cancellous bone of the proximal femoral head by the cement surface,the femoral neck varus and internal rotation angle,the stress distribution of the reinforcing screw,and the displacement of the proximal femur in the fixation model with different amount of bone cement.Results: In the model group of femoral intertrochanteric fracture with different amount of bone cement,the cement surface of model groups A,B,C and D cut the proximal cancellous bone of femoral head the slighly,and the cutting degree of model group E was the most serious.In model groups A,B,C,D and E,the femoral neck varus angles were 5.2 °,6.0 °,4.5 °,5.1 ° and 2.6 ° respectively,and the femoral neck internal rotation angles were 1.1 °,1.4 °,0.9 °,1.0 ° and 0.4 ° respectively;The femoral neck varus angle and internal rotation angle in model E group were the smallest.In model group A and B,the stress of the bone cement volume model was mainly concentrated at the connection between the screw and the main screw;C.In model group C and D,the stress of the bone cement volume model was mostly concentrated at the connection between the screw and the main screw,and the stress tended to disperse to the main screw;In the E model group,the stress of the bone cement model was mainly distributed at the tail end of the reinforcing screw,after the 6m L bone cement reinforced screw model was loaded into the intertrochanteric fracture model,a new fracture occurred at the greater trochanter of femur.In model groups A,B,C,D and E,the proximal femoral displacement was 7.7,8.4,8.2,8.1 and 13.7mm respectively;Among them,the proximal femur displacement of model E group was the largest,and there was bone cement leakage,after the 6m L bone cement reinforced screw model was loaded into the intertrochanteric fracture model,a new fracture occurred at the greater trochanter of femur.Conclusion: In the treatment of severe osteoporotic intertrochanteric EvansⅡ fracture,the use of 2 ～ 4 m L bone cement has good biomechanical effect.When 5m L of cement was injected,some of the stress was dispersed towards the main nail,and microfractures occurred when the trabeculae of the proximal bone were subjected to minor stress.The persistence of stress resulted in a larger range of microfractures.When 6ml of cement was applied,cement leakage occurred,significant displacement of the proximal femur and a new fracture occurred at the greater trochanter.