| PurposeThe wrist joint is one of the most flexible joints in the human body,and its anatomical structure is relatively complex.Among them,a group of very important and complex structures is called triangular fibrocartilage complex(TFCC).A large number of studies have proved that TFCC plays an important role in stabilizing the wrist joint,especially in stabilizing the lower radioulnar joint.Due to its complex structure and great difficulty in research,there are few biomechanical studies on it at present.The finite element analysis method can extract the target structure from the complex structure,study it separately,and eliminate the interference of external factors to the greatest extent.Therefore,this experiment aims to use the finite element analysis method to carry out a preliminary study of the biomechanical characteristics of TFCC,and provide a biomechanical theoretical basis for TFCC injury and repair.Method1.Collaborated with ten healthy volunteers who had no history of carpal bone and ligament diseases and had no wrist injury through X-ray examination,and collected CT and MRI imaging data of their wrist joints(including 1-5 metacarpal bases,proximal and distal carpal bones,and TFCC of the proximal radius and ulna).2.Import the collected CT and MRI data into Mimics in DICOM format,and obtain 10 groups of 3D models of the first,second,third,fourth,and fifth metacarpal bases,navicular,lunate,triangular,pisiform bone,trapezium,trapezoid bone,capitate bone,hamate,and proximal ulna and radius after generating masks,Boolean operations,regional growth,morphological operations,fairing and other processing,and save the generated models in stl format.3.Modify the bone model obtained by Geomagic Studio without destroying the original anatomical structure,including sharpening,removing nails,etc.,and finally mesh it.The generated CAD model is saved in IGS format.4.Import the file into Solidworks software,establish the TFCC model in the CAD bone model according to the anatomical and MRI image data,establish the starting and ending points,draw the guide line,generate the curved surface,fill the curved surface,etc.,and finally obtain the central triangular fibrocartilage disc,volar ulnar radial ligament,dorsal ulnar radial ligament,ulnar triangular ligament,ulnar lunar ligament and ulnar head ligament models in STEP format.5.Import the model into Workbench Ansys,set the materials of bone and ligament according to the literature and relevant data,and test the changes of TFCC and ulna surface stress under different axial loads(5N,10 N,15N,20N)to verify the validity of the finite element model.6.After verifying the validity of the model,carry out TFCC biomechanical analysis,and design the force size and force mode of each part of the model in the static analysis plate.The force size is divided into10 groups,which are 5N,10 N,15N,and 20 N respectively.The force state is set as flexion,extension,ulnar deviation,radial deviation,pronation,and supination according to the wrist movement characteristics.The force distribution diagram and force data of the wrist TFCC in different states are solved through the analysis block.7.To explore the role of TFCC in the wrist joint,experimental group A(TFCC defect model)and control group B(normal wrist joint model)were designed to apply axial load(5N,10 N,15N,20N)to the two groups of models along the direction of the third metacarpal-skull-lunar-ulna respectively,and to compare the changes of the stress on the surface of the ulna(CV value calculated by comparing the stress distribution diagram and data).Result1.Effective validation of the model: the stress value and stress distribution of TFCC surface change with the increase of axial load,which proves that the model is true and effective and can be applied to further experiments.2.The stress distribution range of the TFCC surface is more extensive with the increase of the load force along the direction of the third metacarpal-skull-moon and ulna,and the stress value increases with the increase of the load force along the direction of the third metacarpal-skull-moon and ulna.3.Stress analysis of the central structure of TFCC: the stress and deformation during supination are mainly produced in the volar ulnar radial ligament,while the stress and deformation during pronation are mainly produced in the dorsal ulnar radial ligament.However,the triangular cartilage disc only produces slight deformation during pronation and supination,and its stress and deformation mainly focus on the ulnar deviation of the wrist joint.With the increase of the ulnar deviation angle of the wrist joint,the stress range and stress value of the triangular cartilage disc increase.During the other three activities,the volar ulnar and radial ligaments have a cooperative movement due to the traction of the ulnar and wrist ligaments,so the stress and deformation of the volar ulnar and radial ligaments are greater than that of the dorsal ulnar and radial ligaments.4.Stress analysis of the ulnar ligament: the tension of the ulnar ligament increases with the radial deviation of the wrist joint,and its tensile length increases with the increase of the radial deviation angle,and its stress distribution is relatively uniform.When the wrist joint deviates from the ulnar,the tension of the ulnar ligament still increases,and its tensile length increases with the increase of the ulnar deviation angle,and its stress distribution is relatively uniform.When the wrist joint is extended,the tension of the ulnar ligament increases,and its extension length increases with the increase of the back extension angle.During supination,the ulnar lunate ligament was pulled by the dorsal radioulnar ligament and produced cooperative movement,resulting in a certain degree of deformation and stress of the ulnar lunate ligament.5.Stress analysis of the deltoid ulnar ligament and the ulnar head ligament: When the wrist joint deviates radially,the tension of the deltoid ulnar ligament and the ulnar head ligament increases.Its tensile length increases with the increase of the radial deviation angle.Its stress distribution is relatively uniform.The deformation and stress of the deltoid ulnar ligament are greater than that of the ulnar head ligament.When the wrist joint is extended,the tension of the deltoid ulnar ligament and the ulnar head ligament increases,and its extension length increases with the increase of the back extension angle.The deformation and stress of the deltoid ulnar ligament are greater than that of the ulnar head ligament.When supination occurs,the deltoid ulnar ligament and the ulnar head ligament are pulled by the dorsal radial ulnar ligament and produce cooperative movement,resulting in a certain degree of deformation and stress of the deltoid ulnar ligament and the ulnar head ligament.6.TFCC function discussion: When the normal model is subjected to the axial load along the metacarpal-ulna,the stress on the ulna surface is relatively small,and the stress distribution on the ulna surface is relatively uniform,and the change of stress on the ulna surface is relatively gentle with the increase of the load.When the TFCC defect model is subjected to the same axial load as the normal model,the force on the surface of the ulna is larger than that of the normal model,and the force is uneven.The force is concentrated in one area.With the increase of the load force,the force on the surface of the ulna changes greatly.It proves that TFCC reduces the force transmitted to the surface of the ulna along the metacarpal bone.Conclusion1.In this experimental study,the three-dimensional finite element model of the complex of carpal joint bone and triangular fibrocartilage,which conforms to human anatomy,was established by using the electronic computer tomography(CT)technology combined with software such as MIMICS,Geomagic Studio,Solidworks,Workbench Ansys,etc.After verification,it conforms to the true anatomical mechanism and biomechanical characteristics of the wrist joint,and the model can be used repeatedly in the experiment.2.The stress distribution range and stress value of TFCC change with the increase of axial load.3.The stress and deformation of the ligament in the central area of TFCC are mainly concentrated in pronation,supination and ulnar deviation.4.The stress and deformation of the ulnar ligament are mainly concentrated in the ulnar deviation,radial deviation and back extension.5.The stress and deformation of the deltoid ulnar ligament and the ulnar head ligament are mainly concentrated in radial deviation and back extension,and the deformation and stress of the deltoid ulnar ligament are greater than those of the ulnar head ligament.6.TFCC has the function of reducing the stress transmitted from the metacarpal bone to the surface of the ulna. |
PDF Full Text Request