Finite Element Analysis Of Percutaneous Nail Rod Internal System For Intertrochanteric Fractures Of The Femur

Objective: To investigate the mechanical feasibility of the percutaneous nail-bar system in the treatment of intertrochanteric fractures of the femur,the PFNA and percutaneous nail-bar internal fixation systems were analysed separately.Methods: A healthy male volunteer was selected,and the CT of the volunteer’s femur was saved in DICOM format,after which the 3D model of the femur was reconstructed by importing Mimics and Geomagic software,and the reconstructed femoral intertrochanteric fracture model(AO31-A3.1)was reconstructed by importing the completed femoral model into Solidworks software,and then the femoral intertrochanteric fracture was fixed by using the nail-rod internal fixation system and PFNA respectively.The intertrochanteric fracture was divided into three groups according to different fixation methods: PFNA fixation group,percutaneous nail rod system fixation group A(fixation of fracture ends in the sagittal and coronal planes respectively)and percutaneous nail rod system fixation group B(fixation of fracture ends in the coronal plane only).The reconstructed fracture internal fixation model was imported into Ansys software,and the stresses,material properties and constraints were applied to the model by simulating the stresses on the femur during standing and walking in a normal person.Finally,the results related to the stress and displacement of the femur,internal fixation and fracture ends were obtained for discussion and analysis.Results: When the load was set to simulate human bipedal standing,the maximum stress of internal fixation in the PFNA group was 56.09 MPa;the maximum stress of internal fixation in the percutaneous nail-rod internal fixation system fixation A group was 101 MPa;the maximum stress of internal fixation in the percutaneous nail-rod internal fixation system fixation B group was 41.21 MPa.The maximum displacement of the fracture end in the PFNA group was 1.91 mm;the maximum displacement of the fracture end in the percutaneous nailrod internal fixation system in group A was 0.77 mm;the maximum displacement of the fracture end in the percutaneous nail-rod internal fixation system in group B was 1.31 mm.The maximum stress in the femur was 26.33 MPa in the PFNA group;the maximum stress in the femur was 26.34 MPa in the percutaneous nail-rod internal fixation system fixation group A;and the maximum stress in the femur was 21.55 MPa in the percutaneous nail-rod internal fixation system fixation group B.When the load was set to simulate human walking,the maximum stress for internal fixation in the PFNA group was 107 MPa;the maximum stress of internal fixation in the percutaneous nail-rod internal fixation system fixation A group was 315.93 MPa;and the maximum stress of internal fixation in the percutaneous nail-rod internal fixation system fixation B group 98.334 MPa.The maximum displacement of the fracture end in the PFNA group was 3.03 mm;the maximum displacement of the fracture end in the percutaneous nail-rod internal fixation system in group A was 3.88 mm;the maximum displacement of the fracture end in the percutaneous nail-rod internal fixation system in group B was 5.99 mm.The maximum stress in the femur in the PFNA group was 39.71 MPa;the stress in the femur in the percutaneous nail rod internal fixation system in group A was 98.98 MPa;the maximum stress in the femur in the percutaneous nail rod internal fixation system in group B was 47.45 MPa.Conclusions: The mechanical performance of the nail bar internal fixation system in the treatment of intertrochanteric fractures of the femur was evaluated by comparing the stresses applied to the internal fixation,the magnitude of displacement of the fracture break,and the stresses applied to the femur.In human standing,all three groups of internal fixation systems performed well in all three aspects,with no irreversible bending of the internal fixation due to excessive stress,no excessive displacement of the fracture end that could affect fracture healing,and no fracture of the femur bone due to excessive stress and accelerated bone resorption.The stress on the internal fixation and the stress on the femur did not exceed the corresponding thresholds during simulated human walking,and no complications such as fracture of the internal fixation and periprosthetic fracture occurred.In terms of controlling fracture end displacement,the fracture end displacement of all three fixation modalities was greater than 2mm,and the displacement of both groups A and B of the percutaneous nail rod internal fixation system was greater than that of the PFNA group,but the fracture end displacement of group A was not much different from that of the PFNA group,and the fracture end displacement of group B was greater than that of groups A and PFNA.In conclusion,the mechanical performance of the percutaneous nail rod internal fixation system in the treatment of intertrochanteric fractures of the femur is good,and the main modality for the treatment of intertrochanteric fractures of the femur is still PFNA,and the percutaneous nail rod internal fixation system needs to continue to be evaluated for feasibility in clinical application after completion of in vitro bionic bone biomechanical experiments and human experiments.