External Fixation&Locking Plate Fixation In Distal Radiusfracture Of Finite Element Analysis

Objective and significance:Distal radius fracture is the most common type of fracture in adults.It can be seen at all ages,especially in young adults and the elderly.Distal radius fractures can directly or indirectly involve the wrist,which can affect the rotation,adduction,and abduction function of the upper limb.Therefore,the treatment of distal radius fractures is important for prognostic function and recovery.At present,the most important surgical treatment for distal radius fracture is internal fixation with plate,screw and external fixation with stent.Many scholars have studied and compared the recovery and function of the two after treatment,but there is still a relative lack of research on their biomechanics.This study supplements the research in this respect and provides reference for clinical treatment.Methods:A 60-year-old healthy volunteer was recruited for CT scans of the hand,wrist and forearm.Mimics 21.0 software was used to establish 3D data of distal radius fractures from 2D CT images and save them in STL format.The 3D data was imported into the Geomagic Wrap 2017 software,the model was modified,impurities were removed,surfaces were smoothed,meshed,finite element solid models were generated,and output in WRP format respectively.The finite element model of distal radius was imported into Soildworks 2017 software and divided into groups 1,3,5 and 7 according to Frayman Type Ⅰ,Frayman type Ⅲ,Frayman type Ⅴ and Frayman type Ⅶ.The finite element model of distal radius fracture was generated by osteotomy.According to the data of plate screws and external fixation scaffolds provided by the manufacturer,the volar plate screw fixation model and external fixation scaffolds of the distal radius were designed,and the internal fixation device and external fixation scaffolds were placed in appropriate positions in the finite element model of distal radius fracture.They were divided into groups according to the fixation method,including group A for internal fixation with plate screw and group B for external fixation with stent.Combined with the grouping of fractures,a total of 8 groups of finite element models were obtained,including group A1,A3,A5,A7,B1,B3,B5 and B7.Finite element models of internal fixation and external fixation of distal radius fractures of each group were imported into Ansys 17.0 software,and material attributes,contact relations,meshing,boundary conditions and loading were set.Biomechanical characteristics of different fixation devices used for distal radius fractures were analyzed,and stress,displacement and other data were counted.Results:In all fracture models in group A,the stress of plate and screw was concentrated near the fracture end under any kind of load.The ratio of the peak stress of the plate to the peak stress of the distal radius is about 2-22 times in longitudinal load,volar flexion load and rotation load,and about 2-5 times in rotation load.There is no significant difference in the maximum displacement of group A models under various loads.In the fracture models of group B,the stress of the external fixation scaffold was mainly concentrated on the bone traction needle under any load,and the stress distribution was similar under various loads.The external fixation scaffolders placed 1%-50%of the stress on the distal radius fracture.The longitudinal load placed a relatively high stress of 20%-50%on the distal radius fracture and a relatively low stress of 1%-5%on the volar flexion and rotation load.There is no significant difference in the maximum displacement of group B models under longitudinal load and palmar flexion load.The maximum displacement of group B5 and group B7 models under rotating load is about 2-3 times that of group Bl and B3 models.Main Conclusions:The results of this study suggest that locking plate internal fixation is better than external fixation in coping with various stresses.However,external fixation of distal radius fractures may be considered in open fractures,fractures with joint collapse,comminted fractures of the distal radius,the elderly,and those at high surgical risk.This study ignored the consideration of surrounding tissue,so the actual effect of external and domestic fixed stents is better than that of this experiment.