Tibial Plateau Fractures Involving Posterior Column:Injury Mechanism And Fracture Characteristics In Three Dimensions

Part One Injury pattern simulation of tibial plateau fractures involve the posterior column with three-Dimensional computed tomographyObjective: Posterior tibial plateau fractures(PTPFs)involve a challenging set of considerations;among them,the complex morphology and injury mechanism are poorly characterized.This study aimed to investigate the injury patterns and fracture characteristics of PTPFs using a three-dimensional(3D)simulation technique,then establish a classification base on the 3D injury mechanism?Methods:1.The CT DICOM files of PTPFs were imported into Mimics software to create a project file for each patient.After adjusting the view orientation,3D objects of the tibia and femur were created separately and adjusted to be in full extension as the reference position.The knee position during the fracture was simulated by a 3D technique,which enabled the displaced articular surfaces of PTPFs to match those of the femoral condyles.The motion data of the tibial was recorded.2.The injury mechanism was deduced from the simulated knee position during the fracture?Then the injury mechanism classification for PTPFs was established.According to the rotation angle in the sagittal and axial planes,the PTPFs were classified into four main injury patterns(extension injury pattern,flexion-internal rotation injury pattern,flexion-external rotation injury pattern,and flexion-neutral injury pattern).The subpattern(valgus or varus)were according to the rotation angle in the coronal plane.3.After the exercise,two independent observers classified all the cases respectively,and then 8 weeks later,all the cases with different order were classified again by the two observers The interobserver and intraobserver reliability was analyzed according to the results of classification.Results:1.Total 171 PTPFs were included in this part of the study.According to the injury mechanism classification system,72 PTPFs were extension injury pattern(53 valgus subpattern,19 varus subpattern),61 PTPFs were flexion-internal rotation injury pattern(including 50 valgus subpattern,11 varus subpattern),21 PTPFs were flexion-external rotation injury pattern(18valgus subpattern,3 varus subpattern),17 cases for Flexion-neutral injury pattern.2.Under different injury mechanisms,the femoral condyles impinge on different areas of the tibial plateau,resulting in different fracture characteristics.In the extension type,the lateral femoral condyle impinges anterolateral of the tibial plateau result a split posterolateral fragment,the medial femoral condyle impinges the middle part of the medial tibial plateau,and the characteristics of the posterior medial plateau fragment are split with coronal plane fracture line.In the flexion-internal rotation injury pattern,compression fractures in the posterolateral plateau are formed after the impact of the lateral femoral condyle on the posterolateral plateau,and inverted pyramidal fractures are formed by the impact of the internal condyle on the internal plateau.In the flexion-external rotation injury pattern,the lateral condyle impinges on the anterolateral plateau result a split posterolateral fragment,and the medial condyle impinges on the posteromedial plateau form a smaller fragment.In the flexion-neutral injury pattern,both the medial and lateral condyle of the femur impinges on the posterior plateau,resulting in posterolateral compression fragment and posteromedial cleavage fragment,accompanied by an avulsion fracture of the intercondylar.3.The interobserver and intraobserver reliability of the classification system were both highly reliable(0.63,0.68).Conclusions: In this study,a method involving a simulated injury pattern was developed and combined with the evaluations conducted of fracture characteristics,including two-dimensional(analysis in 2D)and 3D analyses,to make a comprehensive description describe of both the morphology and injury pattern in the cases of tibial plateau fractures with the posterior column.Part Two Primary fracture line mapping for tibial plateau fracture involving the posterior columnObjective: Fracture line mapping is a method applied to demonstrate the fracture characteristics,which is meaningful for the diagnosis and treatment of complex intra-articular fractures.The purpose of this part of this study is to investigate the primary fracture line of tibial plateau fracture involving the posterior column.Methods:1.The CT DICOM files of PTPFs were imported into Mimics software,and all the displaced tibial plateau articular fragments were rendered into 3D objects separately.The 3D fracture fragment objects were moved and rotated to rebuild the articular surface of the tibial plateau,and identified the primary fracture line.2.Fracture line images of the rebuilt TPFs were individually depicted on a 2D tibial plateau template and then the primary fracture line angle(PFLA)were measured ? With the same injury mechanism type,the fracture line images were overlapped with one another,and the overlapping of all layers resulted in a 2D fracture mapping.3.The orientations of the primary fracture line in different injury mechanism types were measured and compared.Results: Extension injury pattern(72 PTPFs),anterior-to-posterior fracture lines(89.13°±14.52°);flexion-internal rotation injury pattern(61 PTPFs),anteromedial-to-posterolateral fracture lines(46.71°±5.39°);flexion-external rotation injury pattern(21 PTPFs),anterolateral-to-posteromedial fracture lines(144.14°±12.78°);and flexion-neutral injury pattern(17 PTPFs),horizontal fracture lines(14.55°±6.14).With significant different fracture line angles(P<0.001),the primary plate should be placed differently between the four types of PTPFs and that enable the screw perpendicular to the fracture line.?Conclusions:1.The Primary fracture line can be identified by the 3D reconstruction technique.2.The orientation of the primary fracture line and fracture displacement were significantly different among different injury mechanism fracture types.The primary fracture line angle was statistically different.Part Three Bicondylar tibial plateau fractures involving posterior column: injury mechanism,fracture characteristics,and surgical strategyObjective: Bicondylar tibial plateau fracture(BTPF)involving the posterior column is a complex intra-articular fracture to treat,however,research focused on the injury mechanism is scarce.The aim was to investigate the relevance between injury mechanism,fracture characteristics and surgical strategy for BTPFs involving the posterior column by a three-dimensional(3D)simulation method.Methods:1.The CT DICOM files of bicondylar tibial plateau fracture involving the posterior column were included in this part of the study.The injury mechanisms were identified and classified by the method proposed in the first part of this study.2.The method in the second part of this study was applied in this part.The three-dimensional characteristics of the posterior fragments and fracture displacement,fracture mapping,primary fracture line orientation and angle were compared between different injury mechanism fracture types.3.For each type,the surgical strategy was made according to the injury mechanism,fracture characteristics and the direction of the main fracture line.Results:1.A total of 96 bicondylar tibial plateau fractures involving the posterior column were included in this study.Sixty cases were extension injury pattern,including 44 valgus subpattern and 6 varus subpattern;twenty-one cases were flexion-internal rotation injury pattern,including 12 valgus subpattern and 9varus subpattern;fifteen cases were flexion-external rotation injury pattern,including 12 valgus subpattern and 3 varus subpattern.2.There were significant differences in fracture characteristics,fracture displacement,primary fracture line orientation and angle,which formed by the three types of injury mechanisms.According to that,the surgical strategy should be different.Conclusions:1.Three main injury mechanisms with distinctive fracture characteristics were found in BTPFs involving the posterior column.2.The "reverse injury mechanism" can be used for the reduction of the BTPFs involving the posterior column.3.According to the degree of fracture displacement and anatomical characteristics of each subpattern of fracture,different surgical strategies should be adopted for fracture reconstruction.