Finite Element Analysis Of Anatomical Combined Plates For Acetabular Fractures Involving The Posterior Wall

ObjectiveThe finite element analysis was used to investigate the biomechanical stability of T-shape anatomical combined plates in the treatment of classical posterior wall acetabular fracture,in order to provide mechanical basis for clinical application.MethodsCT data of the pelvis was selected from a healthy adult male volunteer.Mimics,ANSYS,Hypermesh and Abaqus digital software were used to construct the threedimensional finite element model of pelvis,then verify the effectiveness of the anatomical morphology and mechanical conduction of the pelvis model.The model of classical posterior acetabular wall fracture was established,and five groups of internal fixation models were established:TS(two screws),RP(reconstruction plate),TSRP(two screws and reconstruction plate),MPRP(mini-plate and reconstruction plate)and T-ACP(T-shape anatomical combined plates).Simulating standing and sitting position of the pelvic,the overall stiffness,the average displacement of fracture line,the stress nephogram of the fracture block and the iliac bone model were compared among the pelvis models and the stress nephogram of the five internal fixators were analyzed.ResultsThe average displacement of the posterior wall fracture line showed the order of T-ACP<MPRP<TSRP<RP<TS in both standing and sitting conditions.The comparison between the two groups showed that the average displacement of model TACP and model MPRP was significantly lower than that of model TS(P<0.05),and the average displacement of model RP was significantly higher than that of model T-ACP(P<0.05).There was no significant difference in the displacement among model T-ACP,MPRP,and TSRP(P>0.05).There was no significant difference in displacement between model TS and model RP(P>0.05);Under the standing condition,the overall structural stiffness of each model was NM>T-ACP>MPRP>TSRP>RP>TS>FM.The average stress path displacement of the posterior wall fracture block was FM<TS<RP<TSRP<MPRP<T-ACP<NM;The stress nephogram of the normal pelvic model showed that the stress was concentrated at the greater sciatic notch and the junction of the middle and upper third of the edge of the posterior wall of the acetabulum.When posterior wall fracture occured,the stress was concentrated at the upper edge of the fracture line close to the edge of the posterior wall of the acetabulum;The maximum stress value of the five internal fixation models from large to small was as follows:TS>RP>TSRP>MPRP>T-ACP.The maximum stress value of the TS model was located near the weight-bearing area of the upper screw and cortical bone,and the stress concentration area was located at the contact area between the middle part of the screw and the cancellous fracture line.The stress concentration area of model RP and model TSRP was located at the upper part of the reconstruction plate close to the fracture line.The maximum stress value of model TSRP was located at the part in contact between the low screw and the cortical bone,and the stress distribution of the two screws was more balanced than that of model TS.The maximum stress value of model T-ACP and model MPRP was located at the micro-plate near the acetabular edge across the fracture line.The stress distribution of the posterior wall bone plate in model T-ACP and model MPRP was more balanced than that in model TSRP and model RP.ConclusionsIn the treatment of classical acetabular posterior wall fractures,the fixation effect of two screws is poor,and the stress concentration of the screws is easy to occur.Tshaped anatomical combined plate,2 screws combined reconstruction plate,mini plate combined reconstruction plate internal fixation system all have good biomechanical stability.Among them,the T-shape anatomical combined plate internal fixation system can restore the mechanical transmission characteristics of the pelvis to the greatest extent,the internal fixation stress distribution is balanced,the maximum stress value is small,and the stability is good.Fixation of acetabular posterior wall fractures is safe and feasible.ObjectiveThe finite element analysis was used to investigate the biomechanical stability of H-shape anatomical combined plates in the treatment of classical posterior wall acetabular fracture,in order to provide mechanical basis for clinical application.MethodsCT data of the pelvis was selected from a healthy adult male volunteer.Mimics,ANSYS,Hypermesh and Abaqus digital software were used to construct the threedimensional finite element model of pelvis,then verify the effectiveness of the anatomical morphology and mechanical conduction of the pelvis model.The model of posterior column and posterior wall acetabular fracture was established,and four groups of internal fixation models were established:TSRP(two screws and reconstruction plate),TRP(two reconstruction plates),MPRP(mini-plate and reconstruction plate)and H-ACP(H-shape anatomical combined plates).Simulating standing and sitting position of the pelvic,the overall stiffness,the average displacement of fracture line,the stress nephogram of the iliac bone model were compared among the pelvis models and the stress nephogram of the four internal fixators were analyzed.ResultsThe average displacement of posterior column with posterior wall fracture line in standing and sitting-standing conditions showed the order of H-ACP<MPRP<TRP<TSRP.The average displacements of H-ACP,MPRP,and TRP in the model were significantly lower than those in the model TSRP(P<0.05).There was no significant difference in displacement among model H-ACP,MPRP and TRP(P>0.05);Under the standing condition,the overall structural stiffness of each model was NM>H-ACP>MPRP>TRP>TSRP>FM;The stress nephogram of the iliac bone of the normal pelvic model showed that the stress was concentrated in the greater sciatic notch and the junction of the middle and upper 1/3 of the posterior wall of the acetabulum.When the posterior column and posterior wall fracture occured,the stress was concentrated above the posterior wall fracture line and the weight-bearing area of the acetabular roof,while the stress below the fracture line was significantly reduced.However,the stress in the classical posterior wall region of the acetabulum gradually increased;The maximum stress value of the four internal fixation models from large to small was as follows:TSRP>TRP>MPRP>H-ACP.The maximum stress value of the TSRP model was located at the fracture line across the posterior column of the posterior column plate,and there was a stress concentration area in the middle part of the two screws fixed the posterior wall.The maximum stress value and stress concentration area of TRP were also located at the fracture line of posterior column plate,and the stress distribution of posterior wall plate was more balanced than that of two screws.The maximum stress values of model H-ACP and model MPRP were smaller than those of model TSRP and model TRP.ConclusionsThe fixation effect of two screws combined with reconstruction plate is the worst in the treatment of acetabular posterior column and posterior wall fractures.H-shape anatomical combined plate,two reconstruction plate,mini-plate combined reconstruction plate internal fixation system all have good biomechanical stability.Among them,H-shape anatomical combined plate internal fixation system has balanced stress distribution,small maximum von Mises,and better stability,which can be used to fix acetabular posterior column and posterior wall fractures.