3D Reconstruction Mapping Of Acetabular Fracture And Finite Element Analysis Of Internal Fixation Of Acetabular T Shaped Fracture

Objective1.By analysing the acetabular fracture line through three-dimensional reconstruction,it can provide a new method for better understanding of the classification of acetabular fracture and internal fixation.2.To investigate the biomechanical stability of acetabular T-shaped fractures with single-incision of three internal fixations,minimally invasive double screws,and joint approach with double-plate fixation using finite element analysis,it provides theoretical basis for the choice of more ideal surgical procedures.The first part 3D reconstruction mapping of acetabular fractureMaterials and Methods1.Subjects:1 healthy male adult pelvis CT plain scan data were collected without the history of dysplasia,malformation and injury as a normal template.In line with the condition of the Nanfang Hospital,Southern Medical University 153 patients with acetabular fracture from 2010 to 2017,including 118 males and 38 females,aged from 14 to 82 years old,the average age is 40.5±14.8 years old.7 patients with bilateral acetabular fractures,78 cases of left hip,right hip in 82 cases,a total of 160 cases of acetabular fractures.According to Judet-Letournel classification:38 cases of posterior wall fractures,6 cases of posterior column fractures,2 cases of anterior wall fractures,29 cases of anterior column fractures,11 cases of transverse fractures,7 cases of posterior column fractures with posterior wall,14 cases of transverse posterior wall fractures,Anterior column with posterior semi-transverse fracture in 8 cases,T-type fracture in 16 cases,29 cases of double-column fracture.2.Method:Select a healthy pelvis and establish normal pelvis CT scan,then output the picture in DICOM format.This two-dimensional data is introduced into the Mimics17.0 software.Through the default bone threshold,we choose the pelvis area by the way of regional growth,remove the femur and sacrum,get the right hip bone,and get the three-dimensional solid model of hip bone by three-dimensional calculation,and intercept the medial view as a template.Research object modeling and information collection:We collect 153 people CT scan conform to the standard of 160 cases of acetabular fracture.The data were imported into Mimics 17.0 software,and the three-dimensional model of the right hip bone was obtained by the same method.And complete the reset joint modeling fracture by cutting separation,rotating to reduction of fracture,for several different angle shot on the inner side of the acetabulum,the left hip image flip horizontal into right hip,drawing with Adobe illustrator software.After all fractures and dislocations were completed,the fracture line mapping was formed by overlaying,and the morphological characteristics were observed.3.Application of 3D reconstruction technique in fracture mapping and treatmentThe use of CT scan data for three-dimensional reconstruction can help to observe the fracture morphology and damage,help to statistically observe the characteristics of a certain type of fracture,and the design of the surgical plan,the choice of surgical approach,internal fixation and fracture classification Standardization provides guidance.ResultA total of 160 cases of acetabular acetabular fractures were included,including 78 cases of left hips and 82 cases of right hips.The acetabular fractures were classified according to Judet-Letournel classification:38 cases of posterior wall fractures,6 cases of posterior column fractures,2 cases of anterior wall fractures,and anterior column fractures.In 29 cases,11 were transverse fractures,7 were posterior columns with posterior wall fractures,14 were posterior wall fractures,8 were posterior semi-transverse fractures,16 were T-shaped fractures,and 29 were double-column fractures.The acetabular fracture line drawn by three-dimensional reconstruction involved 100 anterior column fracture lines,68 posterior column fracture lines,and 40 posterior acetabular fracture lines.In all types of fracture lines(Table 2-1),48.1%(100/208)of the posterior column accounted for 32.7%(68/208)of the posterior column and 19.2%of the posterior fracture line(40/208).The second part The finite element analysis of internal fixation of acetabular T shaped fractureMaterials and Methods1.The experimental objectA healthy adult male volunteer was selected and X-ray examination was performed to exclude abnormalities such as pelvic fractures and deformities.Use a multi-slice spiral CT to perform a thin layer CT scan with a 0.8 mm slice thickness and save as the DICOM format.A total of 350 CT images were obtained.2.Establish a pelvic modelThe above CT scan data was imported into Mimics 17.0 software,and processing such as segmentation,filling,patching,and smoothing was performed.The cancellous and cortical bones of each bone were extracted,which were imported into Geomagic Studio 2013 software in STL format.We smoothed,divided,mesh,fitting surface and other operations to reverse molding and saved in STEP format.The processed model was imported into Slidworks 2016 software for assembly and articular cartilage processing.Then the whole pelvis model was introduced into Ansys 17.0 software to set up the ligaments,the properties of the bone material and the contact of the joint surface,and to establish a complete pelvic finite element model.3.Verification of validity.The anatomical differences were verified by measuring the distance between the reconstructed original pelvic 3D model and the optimized landmarks of the finite element pelvic model after treatment,and t-test was used to count the differences between the two.Mechanical transmission characteristics verification:The normal pelvis model was imported into the Ansys software to simulate the standing position and the sitting position,and the displacement cloud image and the stress cloud image were observed.The left and right sides were symmetrical.The model established in this experiment was effective.4.Establishment of internal fixation model for T shaped fracture of acetabulumThe validated pelvic model was imported into Solidworks 2016 software to establish an acetabular T-shaped fracture model;and five different internal fixation models for acetabular T-shaped fractures were made:(A)reconstruction plate for anterior column+lag screws for posterior column,(B)lag screw for anterior column+reconstruction plate for posterior column,(C)anterior column and internal posterior column reconstructive plate(combined plate)and(D)retrograde lag screws for two columns,(E)anterior column and behind posterior column reconstructive plate.5.Constraint loading and data collection of fracture modelsFive kinds of internal fixation models of acetabular T-shaped fractures were introduced into Ansys 17.0 software.When the standing position was placed,the ends cross-sections of the bilateral femurs were restrained and fixed.When sitting,the ischial tuberosities were restrained and fixed.600N load was applied to the S1 vertebral endplate for mechanical analysis.The detection indexes include:(1)Measuring the displacement data of 16 nodes of the front column and the rear column of the fracture line.The larger the average displacement,the less stable the internal fixation method is.(2)Comparing the maximum stress on the fracture line.The greater the stress,the more unstable it is.ResultsRegardless of the standing position or the sitting position,the average displacement of each node of the front column is from large to small as follows:D>B>A>C>E.The displacement of the posterior column is:D>A>B>C>E.That is,the displacement of the steel plate is smaller than that of the screw.The maximum stress at the fracture end,regardless of the type of the internal fixation,the stress concentration area under the standing position is mainly in the fracture line of the anterior column,and the stress of the anterior column is greatest when the anterior column screw is used for fixation;the stress concentration area under the sitting position is mainly in the posterior column.When the posterior column screw is fixed,the stress at the fractured end of the posterior column is the greatest,and the stress at the fracture end is smaller when the combination plate and the double plate are fixed.ConclusionsTherefore,on the choice of the reduction and fixation method for acetabular T-shaped fractures,the author believes that the single incision anterior column reconstruction plate combined with the internal post-columnar plate(combined steel plate)fixation is a method with less trauma and good fixation effect.Column with large displacement or posterior wall fracture can be fixed by double-column reconstruction plate.For the degree of comminution is small of one column,and the displacement is small or basically no displacement,It can be fixed by one column reconstructive steel plate and another column lag screw by poking a good reduction.