A Finite Element Analysis On Fixation Of Distal Radius Fracture Using AO Oblique T-plate

Objective1. To establish the three-dimension finite element models of radius and ulna,including the interosseous membrane of forearm and dorsal ligament of distalradioulnar joint and volar ligament of distal radioulnar joint. By analyzing thestress distribution and conduction under four normal situations, that is compress-ion, tension and torsion, the rationality of those models can be validated. It canprovide the foundation for further research.2. To establish the three-dimension finite element models of distal radius fracture(AO: 23A2.2) and AO oblique T-plate. And then the internal fixation model ofdistal radius fracture can be established using AO oblique T-plate. (AO stand forAssociation for Osteosynthsis)3. The distal radius fracture model which was fixated by AO oblique T-plate wasstudied, to see the stress distribution and conduction under several loadingconditions such as compression, tension and torsion. The method of internalfixation can then be authenticated. It can provide the biomechanical theoreticalfoundation for clinical application.Methods1. A cadaveric forearm was scanned by CT. The two-dimension image and threedimension coordinate of CT date was then input to simulation software MIM -ICS8.1 to establish the three dimension models of ulna and radius. The modelswere input to finite element analysis software ANSYS8.1 after transformed byanother software Freeform. Modeling the interosseous membrane of forearmand dorsal ligament of distal radioulnar joint and volar ligament of distalradioulnar joint, meshing all the models and endowed with their materialquality, and then the finite dement models of ulna and radius, including theintero -sseous membrane of forearm and dorsal ligament of distal radioulnarjoint and volar ligament of distal radioulnar joint, can be established.2. Four loading conditions were simulated in this study after confining the degreeof freedom in normal ulna and radius models, that is an axial compression of100N, an axial tension of 100N, and a torsion load of 1NM at the end of theradius (inward rotation and outward rotation), to analyze the stress distributionand conduction.3. A 1 mm fracture gap, 25 mm from the distal end of the radius was modeledusing an idealized planar cut to simulate the distal radius fracture. The date ofT-plate was put into ANSYS8.1 to build the finite element model of plate, theplate was projected onto the corresponding bony surfaces using Booleanoperation to simulate the fixation of distal radius fracture.4. Confining the degree of freedom in the fixation of distal radius fracture model,and then the same loading conditions as above were putted on, that is an axialcompression of 100N, an axial tension of 100N, and a torsion load of 1NM atthe end of the radius (inward rotation and outward rotation), to analyze thestress distribution, conduction and the displacement under loading.Results1. The three-dimension finite element models of ulna, radius, the interosseousmembrane of forearm, dorsal ligament of distal radioulnar joint and volarligament of distal radioulnar joint were established, as were as the distal radiusfracture model(A0:23A2.2) with or without the internal fixation of AO obliqueT-plate. Further research can be carried on basic on those models.2. The stress distribution and conduction had been show under the above fourloading conditions, that was an axial compression of 100N, an axial tension of100N, and a torsion load of 1NM at the end of the radius (inward rotation and outward rotation), it can be seen that the stress was concentrate approach to thefracture line area. The result was coordinated with the real situation.3. The stress distribution, conduction and displacement of the internal fixationmodel had been analyzed under the four loading conditions. It can be seen thatthe stress was concentrate on the plate, and especially concentrate on the neckof plate under axial compression and tension conditions. And the displacementunder loading conditions was insignificant. It is a suitable implantation for thiskind of fracture.Conclusion1. The models of ulna, radius, the interosseous membrane of forearm, dorsalligament of distal radioulnar joint and volar ligament of distal radioulnar jointwere established. Those models were all proved to be dummy and similar toreal situation, and can be used in further research of finite element analysis.2. The fixation of distal radial fracture (AO:23A2.2) using AO oblique T-plate hadfine biomechanical characteristic, the stress was distribute, conducted andconcentrated well on the plate. It can be a useful method in clinical application.The innovation in this study1. The finite element models of ulna and radius, including the interosseousmembrane of forearm and dorsal ligament of distal radioulnar joint and volarligament of distal radioulnar joint, were established. The layer thickness of the CTdate we used was 0.6mm. It is thinner than any one of the model that had everreported.2. According to the finite element analysis and biomechanical study in internalfixation and external fixation of distal radius fracture, most of them only simulat-ed the situation of axial compression. In this study, we also simulated the situatio-ns of tension and torsion beside compression.3. It is the first finite element analysis of internal fixation of distal radius fractureusing T plate (AO: 23A2.2). It can provide the biomechanical theory for clinicalapplication.