Biomechanical Analysis Of Three Different Internal Fixation Methods In The Treatment Of Tile-C Pelvic Fracture

Background: Pelvic fracture is a common type of fracture in clinic.Tile-C pelvic fracture refers to the unstable rotation and vertical of pelvic posterior ring,which is the most serious type of unstable pelvic injury with complex treatment and more complications.The rupture of sacroiliac complex after Tile-C fracture is the absolute indication of operation.It needs to fix pelvis timely and effectively,reconstruct the stability of posterior pelvic ring,and reduce the occurrence of complications.In the fixation of posterior ring fracture,how to choose the appropriate fixation method and what is the best fixation method are still controversial.Closed sacroiliac screw fixation and posterior portal plate fixation are commonly used in clinical practice.In recent years,pedicle screw system has been gradually used in the fixation of complex pelvic fractures,namely iliolumbar fixation.In order to verify the biomechanical stability of iliolumbar fixation compared with the two traditional internal fixation methods,it is necessary to conduct biomechanical analysis on the internal fixation model.Three dimensional finite element analysis is a method of biomechanical analysis through computer modeling.It has the advantages of individuation and repeatability,and also high reliability under standard operation.It can be used for biomechanical analysis and comparison of three different internal fixations.Objective: At present,there is no detailed comparative analysis between iliolumbar fixation and traditional internal fixation in terms of biomechanics.Purpose of this study is to verify whether iliolumbar fixation has reliable biomechanical stability compared with traditional surgical methods by three-dimensional finite element analysis of iliolumbar fixation,sacroiliac screw fixation and posterior portal plate fixation.A fixation method with satisfactory fixation effect was obtained,so as to provide an effective basis for clinical treatment.Methods: A normal volunteer was selected for pelvic CT scan.The image files were processed to establish a normal pelvic solid model,and the finite element model of Tlie-C pelvic fracture was established through sacral foramen and pubic symphysis.The models of iliolumbar fixation,posterior portal plate fixation and sacroiliac screw fixation were established by modeling software and installed on the established pelvic fracture model.The three groups of pelvic fracture models with different internal fixations were imported into the finite element analysis software,then the ligaments and cartilage were installed in turn,and the mechanical properties of the pelvic parts were assigned.By fixing the bilateral acetabulum and applying500 N load on the plane above the vertebral bone,the pelvic stress was simulated when the two feet were standing.The maximum von Mises stress,total pelvic displacement,fracture separation and displacement,average stress of fracture surface and maximum stress of injured sacrum in different internal fixation fracture models were compared.Results: In the upright condition,the maximum pelvic displacement of iliolumbar fixation,posterior portal plate fixation and sacroiliac screw fixation were 1.65 m,1.77 mm and 0.59 mm.The maximum Von Mises stresses of internal fixation were 168.66 Mpa,95.4Mpa and 101.8 Mpa.The fracture separation and displacement were 0.52 mm,0.90 mm and 0.40 mm.The maximum Von Mises stresses of injured sacrum were8.908 Mpa,20.019 Mpa and 16.033 Mpa.The average Von Mises stress of bone fracture was 6.11 Mpa,8.36 Mpa and 4.22 Mpa.Conclusion:There are some differences in biomechanics among sacroiliac screw,posterior portal plate and iliolumbar fixation.In terms of stress conduction,the three internal fixation methods can effectively restore the stress conduction path of the injured pelvis.The stability of iliolumbar fixation was slightly worse than that of sacroiliac screw fixation,and the stability of posterior portal plate was the worst.In terms of fracture surface stress,the three internal fixation models can maintain the appropriate stress stimulation on the fracture surface and promote fracture healing.Iliolumbar fixation has good biomechanical properties and can be used as a good choice for Tile-C pelvic fractures.