The Effect Of Lag Screw Position For The Stabilization Of The Treatment Of Stable Intertrochanteric Fractures With Intertan:a Finite Element Analysis

Objective:To explore the effect of the position of Intertan lag screw on the stability of the treatment of stable intertrochanteric fracture(Evans-Jensen type Ⅰ)by finite element analysis.Methods:Using the CT image data to carry out the digital three-dimensional reconstruction of the proximal femur and finite element model,using computer software tools to applying the three-dimensional anatomical measurement for anatomical parameters of the proximal femur.Through skinning,segmentation,smoothing and material property assignment to establishing the finite element model of the femoral head and implant material Intertan.Dividing the femoral head into 9 regions and implanting the Intertan model into the 9 corresponding regions of the fracture model respectively.Test was carried out by loading load and boundary conditions for the model.By comparing the strain magnitude and strai volume generated by each model of femoral head fracture,to determin which position of the implant in the femoral head can achieve high stability.Results:In all 9 regions of the femoral head models,when the lag screw was located in the central region of the femoral head,can achieve the maximum strain value,which was2.004x10-6,when the screw was located in the posterior-inferior of the femoral head,can achieve the minimum strain value,which was 1.792x10-6.The maximum volume in the region with strain larger than 1500x10-6 was 1.7398 x10-3,at this time,the lag screw was located in the anterosuperior of the femoral head;the minimum volume was 0.6962x10-3,at this time,the screw was located in the posterior-inferior of the femoral head.With lag screw located in inferior region,obtained strain volume was obviously smaller as compared to located in middle-upper region,suggesting higher stability.Conclusion:In our experiment,when using the Intertan to treat the stable intertrochanteric fracture(Evans-Jensen type Ⅰ),it was considered higher stability when the lag screw of Intertan is in the posterior-inferior of the femoral head.