Three-dimensional Finite Element Analysis Of Proximal Tibiofibular Joint Injury

Part 1 Anatomic parameters measurement and study of the proximal tibiofibular jointObjective The anatomical parameters of the proximal tibiofibular joint(PTFJ)were measured to understand the differences of the anatomical parameters of PTFJ in different genders,different sides and different types in detail.It also provides anatomical reference for the establishment of three-dimensional finite element model of the PTFJ and the selection of internal fixation after the injury of the PTFJ.Methods From January 2022 to August 2022,200 adults(100 males and 100 females)who underwent magnetic resonance imaging(MRI)of knee joint in imaging center of our hospital were randomly selected,including 95 cases of left knee and 105 cases of right knee.Excluding cases that may affect the measurement results,such as dislocation of the PTFJ,tumor and cyst of the PTFJ,fracture of the proximal tibiofibula,etc.Software was used to measure the inclination angle(angle A),deflection angle(angle B),contact area(S),horizontal projection area(Sτ),sagittal plane projection area(Sφ)and coronal projection area(Sv)of PTFJ.The anatomical parameters of the PTFJ were compared between sexes,different sides and different types.Through the above comparison,we understand the differences of different anatomical parameters of the PTFJ between different genders,different sides and different types.Results The angle A in male was smaller than female(P<0.05).The deflection angle B,contact area(S),horizontal projection area(ST)and coronal projection area(Sv)in male were all greater than female(P<0.05).There was no significant difference in the sagittal plane projection area(Sφ)of the PTFJ between male and female(P>0.05).There was no significant difference in the above anatomic parameters of the left and right PTFJ(P>0.05).In 200 cases,the inclined PTFJ was more common than the horizontal PTFJ.And the contact area,horizontal projection area and coronal projection area of inclined PTFJ were significantly smaller than that of horizontal PTFJ(P<0.05).Conclusion It is effective to measure the anatomic parameters of the PTFJ by knee MRI.It was found that the deflection angle,contact area,horizontal projection area,and coronal projection area of the PTFJ of males were significantly larger than females due to the physiological differences between sexes.However,there was no significant difference in the anatomical parameters of the left and right PTFJ.It is found that inclined PTFJ are more common,and their contact area,horizontal projection area and coronal projection area were significantly smaller than that of horizontal PTFJ.This part of measurement provides anatomic reference for the establishment of finite element model of the PTFJ and the planning of internal fixation angle after the injury of the PTFJ.Part 2 Establishment and validation of the 3-dimensional finite element model of the knee joint and the proximal tibiofibular jointObjective The three-dimensional finite element model of normal knee joint and PTFJ was established,which included bone tissue,ligament,tendon,meniscus,articular cartilage and other structures.The validated model provides a reliable 3D finite element model for the study of the effect of PTFJ injury on the stability of the knee joint and the selection of internal fixation after PTFJ injury.Methods The knee joint of a healthy young female volunteer was selected as the study object.Physical examination and imaging examination of the knee joint were performed to rule out osteoarthritis,trauma,infection,cyst,tumor and other conditions of the knee joint and PTFJ.CT and MRI scans were performed on the knee joint,ranging from 10cm above the superior margin of patella to 15cm below the line of the knee joint.CT and MRI image data in sagittal,coronal and transverse positions of the knee joint were obtained.The above image data are output in DICOM format and then imported into the 3D reconstruction software MIMICS.Construct knee bone masks using CT Bone function based on CT image Data.Calculate 3D function is used to isolate knee bones and generate an initial finite element model of osseous structure.And the knee ligament,articular cartilage,meniscus and tendon based on MRI imaging data.The above models were imported into 3-MATIC software for deep processing,and the normal knee joint and PTFJ finite element model was obtained.Export CDB file to ANSYS software to assign,setting contacts,define constraints,and load conditions.The reliability of the finite element model is verified by comparison with previous references.Results A complete model of the knee joint and the PTFJ including bone tissue,ligaments,tendons,meniscus and articular cartilage was established,including 203,965 meshes and 327,073 nodes.The accuracy of geometric shape and the reliability of model parameters were verified.At the same time,the mechanical test was carried out to simulate the front drawer of knee joint by loading 134N forward load on the proximal tibia.The calculation of tibia movement was similar to the results in the references,which confirmed the accuracy and reliability of the model.Conclusion In this part,the finite element analysis method based on the modeling of CT,MRI and other image data of knee joint by MIMICS,3-Matic and other software is effective and can be used as an effective means of biomechanical research.It has been proved that the model established in this part is accurate and reliable,which can be used as the basic model to compare the influence of PTFJ injury on the stability of knee joint and the reliability of internal fixation after PTFJ injury.Part 3 Three-dimensional finite element analysis of the effect of the PTFJ injury on knee stabilityObjective An injury model of the PTFJ was established to calculate and analyze the changes of knee stability after the injury of the PTFJ,and to elaborate the influence and mechanism of the PTFJ injury on the stability of the knee joint,so as to provide reference for the selection of clinical treatment.Methods Based on the model established in the second part,the injury model of the PTFJ was constructed by adjusting the load-deformation curve of the relevant ligaments.The model of PTFJ injury was verified under the same working conditions as the model in the reference,which proved that the model was accurate and reliable.The 134N forward and backward force,10N·m internal rotation,external rotation,varus and valgus torque were applied on the normal knee model and the PTFJ injury model.We selected 9 observation sites on the tibial plateau to compare the range of tibial motion between the normal model and the model of PTFJ injury.We evaluated the role of the PTFJ in maintaining knee stability by comparing the range of tibial motion.Results There was no significant difference in tibial activity in both models when applying 134 N forward load force,10N·m internal rotation torque,and 10N·m valgus torque loading conditions to the tibia,respectively(P>0.05).Under the condition of applying 134N backward load force,10N·m varus torque and 10N·m external rotation torque to the tibia,respectively,the movement of tibia was 3.583±0.892 mm,4.799±0.092° and 18.963±0.027°,respectively.The movement of the tibia in the PTFJ injury model was 5.127±1.224 mm,5.277±0.104°,and 21.399±0.031°.There were significant differences between the injured model of PTFJ and the normal model of PTFJ in the above conditions(P<0.05).Conclusion The PTFJ plays an important role in maintaining the posterolateral stability of the knee joint and should be emphasized in clinical treatment.The influence mechanism of PTFJ injury on the stability of knee joint is mainly related to the relaxation of lateral collateral ligament and popliteofibular ligament.The PTFJ injury mainly affects the stability of external rotation,varus and backward knee joint.Part 4 Three dimensional finite element analysis of different internal fixation methods for the proximal tibiofibular joint injuryObjective Three-dimensional finite element software was used to compare the biomechanical characteristics of different internal fixation methods after the PTFJ injury,so as to provide theoretical basis for clinical treatment.Methods On the basis of the model established in the third part,three kinds of internal fixation models were established,including screw internal fixation,anchor internal fixation with wire and bicortical suspension technology internal fixation model.For each model,the same working conditions were respectively loaded(tibia was restrained,100N anterolateral force was applied to the back of the fibula head,and 100N posterior medial force was applied to the front of the fibula head),and the degree of movement and rotation angle of the fibula head were calculated.The above results were compared with the range of motion of the normal PTFJ to analyze the effectiveness of the three internal fixation methods.Results The normal PTFJ model and three internal fixation models were established.The three models were loaded in ANSYS to calculate the range of motion of the fibula head compared with that of the normal model.The results showed that the forward and backward movement and rotation angle of the fibula head in the screw fixation model were smaller than those in the normal PTFJ model(P<0.05).The degree of forward and backward movement and rotation angle of the PTFJ in the anchoring model and the bicortical suspension model were not significantly different from the normal PTFJ model(P>0.05).Conclusion Position screw fixation,anchor fixation and bicortical suspension fixation can effectively restore the stability of the PTFJ after injury.However,after screw fixation,the range of motion of the PTFJ is reduced and there are problems of excessive restraint.Anchoring and bicortical suspension are more consistent with the biomechanical characteristics of the PTFJ,which is worthy of promotion and application.