Finite Element Analysis Of Femur Shaft Fracture In Post-polio Patient Fixed With Custom-made Plate

Purpose: The deformity of femur caused by poliomyelitis often make the use of conventional implants encounter lots of difficulties.The custom-made plate fits the patient’s femur very well,and the outcome in previous studies is also good,but there is still a lack of mechanical analysis reports on the custom-made plate.Therefore,the finite element analysis of custom-made plate was carried out in this study to provide theoretical support for it.Objects and methods: Due to the uniqueness of post-polio,normal bones could not be used in this analysis,and postoperative CT data would have strong artifacts.This study choose the preoperative data of patients and conduct a software simulation of reduction,so as to perform stress analysis on the internal plant and femur after surgery.The postpolio patient,53-year-old,male,65 kg.He received operation on January 29,2019,due to the fracture of the right femoral shaft caused by the fall.His femur and femoral neck are very small,a large anteversion of femoral neck exists.The preoperative femur is scanned by CT,and the modeling is constructed in Mimics software.Such as Edit mask and mask edition are used to get the femur.In Geomagic,the model is further processed by means of various tools.We use Solidworks to simulate surgical reduction and design internal plants.Finally,ANSYS is used to analyze the stress of plate,screw and femur,and the ultimate strength of the material is compared to calculate the safety and rationality of the internal plant.Results :The peak stress of femur was 67.857 Mpa,which was lower than the ultimate strength.The transition of the stress is smooth The peak stress of plate is 370.29 Mpa,which is located at the fracture plane and lower than its’ ultimate strength.The peak stress of the screw was 138.26 Mpa.It is lower than its ultimate strength.And located at the sixth screw which is closed to the fracture plane.The deformation of the femoral head is the most obvious and becomes smaller as it passes down to the distal of the femur.When the load is loaded to the maximum,there is no obvious displacement of the fracture area.Conclusion : Through finite element analysis,the stress of the implant is lower than its ultimate strength and there is no obvious deformation of the fracture.The overall stability of the implants meets the requirements.conventional plate is difficult to meet the clinical requirements.Since the full-length customized plate has a long working area,the stress of the fracture area is shared to the entire plant and the stress transition is smooth,which avoids the occurrence of stress concentration.During postoperative follow-up,callus formed well in the fracture area of the patient,the internal plant is not overly stable.In this case,the fracture area of the patient was located in the proximity of femur.Problems such as small deformed bones and large anteversion of femoral neck present.If we use conventional plate,only 2-3 screws can be inserted into the proximal femur,which cannot reach enough stability.In addition,the conventional plate is larger than the femur,which is easy to cause discomfort and pain because of the friction between the soft tissue and the internal plant.In the treatment of femoral shaft fracture of post-polio patient,the advantages of custom-made plate are obvious both in clinical application and finite element analysis.