| Part One Injury mechanism simulation and classification of flexion tibial plateau fractures with 3-dimensional CT reconstructionObjective: Flexion tibial plateau fractures(FTPFs)involving posterior condyle have a complex injury mechanism and are rarely reported in literature.The aim of this study is to simulate the injury mechanism of FTPFs with3-dimensional CT reconstruction technology and propose the classification of FTPFs based on 3-dimensional injury mechanism.Methods:1.DICOM files were generated from the CT scans of FTPFs and imported into Mimics software(19.0,Materialise,Leuven,Belgium)to create3 D segments of the tibia and femur separately.The reference position was defined as full extension and then the tibial 3D segment was aligned with the articular surface of the femoral condyle.Adjustments were also made by using two-dimensional(2D)images to obtain the optimal alignment,and then the corresponding injury patterns were deduced,the magnitudes of translation and rotation incurred after the segments were aligned were calculated by Mimics software.2.FTPFSs were divided according to the fracture region and further subdivided according to the data from the simulated injury patterns.Varus and valgus were defined as the degree of rotation in the coronal plane(varus<0°;valgus>0°),internal rotation and external rotation were defined as the degree of rotation in the axial plane(internal rotation>10°;flexion-neutral-10°～10°;external rotation<-10°).3.Interobserver reliability among the 3 observers was assessed in the first round,and another round of evaluation was performed among the same 3observers after an interval of 8 weeks to evaluate the intraobserver reliability.Results:1.A total of 108 patients with FTPFs were enrolled.FTPFs were classified into two groups according to the fracture region: unicondylar FTPFs(type I)and bicondylar FTPFs(type II).According to the injury patterns simulated in this study,the two types of FTPFs were further subdivided into 5subgroups: pure flexion-varus fractures(type IA),pure flexion-valgus fractures(type IB),flexion-neutral fractures(type IIA),flexion-internal rotation fractures(type IIB)and flexion-external rotation fractures(type IIC).The most common type of fracture in this case series was type IIB(35.2%,38/108),followed by type IB(26.9%,29/108),type IIC(21.3%,23/108),type IIA(13.0%,14/108)and type IA(3.7%,4/108).2.The average kappa value was 0.66 for interobserver reliability and 0.71 for intraobserver reliability,both representing substantial agreement according to the levels of agreement proposed by Landis and Koch.Conclusions:1.The 3-dimensional CT reconstruction simulation technology can infer the injury mechanism of FTPFs.2.The FTPFs are often accompanied by rotation of knee.3.The classification of FTPFs simulated by 3-dimensional CT reconstruction technology has high reliability.Part Two Morphological characteristics and associated injuries of flexion tibial plateau fracturesObjective: The flexion tibial plateau fractures are complex intra-articular fractures with different fracture morphologies.The purpose of this part of this study is to investigate the morphological characteristics and associated injuries of different types of flexion tibial plateau fractures,which is helpful for a comprehensive understanding of the flexion tibial plateau fractures.Methods:1.The imaging data of FTPFs were in the first part of this study were selected.The tibial plateaus were reconstructed by computer and the morphological charateristics were observed.2.The tibial plateaus were reconstructed by 3-dimensional CT reconstruction technology,and the direction and position of the main fracture plane of the tibial plateaus were observed.3.The tibial plateaus and fibulas were reconstructed by 3-dimensional CT reconstruction technology.Fisher’s exact test was used to compare the incidence of concomitant injuries such as proximal fibular fractures、avulsion fractures of intercondylar eminence 、 anterolateral quadrant fractures 、posterolateral quadrant split fractures and posterolateral quadrant collapse fractures among different types of FTPFS,and was also used to compare the incidence of proximal fibular fractures between posterolateral quadrant split fractures and posterolateral quadrant collapse fractures.Differences were considered significant if the P value was less than 0.05.Results:1.For pure flexion-varus fractures,the stress zone between the femoral condyle and the tibial plateau was located in the posteromedial plateau.For pure flexion-valgus fractures,the stress zone between the femoral condyle and the tibial plateau was located in the posterolateral plateau.For flexion-neutral fracture,the contact zone between the lateral femoral condyle and the tibial plateau was located in the posterolateral plateau,and the contact zone between the medial femoral condyle and the tibial plateau was located in the posteromedial plateau.The main fracture plane starts from the posteromedial region,passes through the centre of the tibial plateau involving the tibial eminence,and ends in the posterolateral region.The posteromedial fracture fragment often involves approximately half of the medial condyle,and the posterolateral plateau fracture is often compressed.For flexion-internal rotation fracture,the contact zone between the lateral femoral condyle and the tibial plateau was located in the centroposterior-lateral plateau,and the contact zone between the medial femoral condyle and the tibial plateau was located in the anteromedial plateau.The main fracture plane starts from the anteromedial region,passes through the centre of the tibial plateau involving the tibial eminence and ends in the posterolateral region.The posteromedial fracture fragment often involves a large portion of the medial condyle,and centroposterior fractures of the lateral plateau often collapse and comminute.For flexion-external rotation fracture,the contact zone between the lateral femoral condyle and the tibial plateau was located in the anterolateral plateau,and the contact zone between the medial femoral condyle and the tibial plateau was located in the posteromedial plateau.The main fracture plane starts from the anterolateral region,passes through the centre of the tibial plateau involving the tibial eminence and ends in the posteromedial region.Anterolateral fractures of the plateau are often split and collapsed,and the posteromedial fragment often involves a small portion of the medial condyle.2.The incidence of posterolateral quadrant collapse fractures among patients with type IIB fractures is significantly increased relative to that among patients with type IIC fractures.The incidence of posterolateral quadrant split fractures,anterolateral quadrant fractures and proximal fibular fractures among patients with type IIC fractures is significantly higher than that among patients with type IIB fractures.A high incidence of avulsion fractures of the intercondylar eminence was found in this series of cases(72.2% 78/108).All type IIA and type IIB fractures are associated with avulsion fractures of intercondylar eminence,and 44.8% of type IB fractures and 56.5% of type IIC fractures are accompanied by avulsion fractures of intercondylar eminence.The number of these concomitant injuries significantly differed between patients with type IIB fractures and those with type IIC fractures(P<0.001).The incidence of posterolateral quadrant split fractures combined with proximal fibular fractures was significantly higher than that of posterolateral quadrant collapse fractures was also found in this study.(87.5% vs.13.6%)(P<0.001)Conclusions:1.The fracture morphology and main fracture plane of different types of flexion tibial plateau fractures are different.2.The associated injuries of different types of flexion tibial plateau fractures are different.The number of these concomitant injuries significantly differed between patients with type IIB fractures and those with type IIC fractures.Part Three The surgical strategy of flexion tibial plateau fracturesObjective: The surgical approach of flexion tibial plateau fractures is different from the traditional medial and lateral approach,which is usually posterior approach,and the operation is more complicated.The purpose of the third part of this study is to formulate specific surgical plans according to the morphplogical characteristics and injury mechanisms of different types of flexion tibial plateau fractures and conduct postoperative evaluation aimed at Patients with flexion tibial plateau frature treated by Carlson approach.Methods:1.Patients with flexion tibial plateau frature treated by Carlson approach were selected and classified according to the injury mechanism simulated by computer 3d reconstruction using the research method of the first part of this study.For pure flexion-varus fracture,S-shaped arc incision was used in the posteromedial knee joint.For pure flexion-valgus fracture,the posterolateral S-shaped arc incision of the knee joint was used.For the flexion-neutral fracture and the flexion-internal rotation fracture,the posteromedial and posterolateral fracture fragments were fixed by the posteromedial and posterolateral S-shaped arc incision of the knee joint.For the flexion-external rotation fracture,after the posterior fracture fragments were treated by Carlson approach,the position was changed and the classical anterolateral tibial plateau approach was used for reduction and fixation of the anterolateral quadrant fracture.2.The operation time and blood loss of each patient were recorded.The patients were followed up every 3 months after discharge,including X-ray examination,knee pain examination and knee range of motion examination.The fracture healing time,fracture reduction,knee function score,knee range of motion and postoperative complications of each patient were recorded.Fracture healing time was determined by clinical and radiographic criteria,and knee function was evaluated using the Rasmussen score,the fracture reduction was evaluated using the method proposed by Biggi.3.The simple single-condylar fractures were assigned to Group A,and complex double-condylar fratures were assigned to Group B.T test was used to compare the operation time,blood loss,the fracture healing time,knee function Rasmussen score,knee range of motion between Group A and Group B.Fisher’s exact test was used to compare the fracture reduction between Group A and Group B.Results:1.A total of 66 cases of flexion tibial plateau fracture treated by Carlson approach were included in this study,followed up for 9-12 months(mean 10.6months).According to the classification system of the first part,32 cases(48.5%)were simple single-condylar fractures and 34 cases(51.5%)were complex double-condylar fractures.Pure flexion-varus fracture in 4 cases(6.1%),pure flexion-valgus fracture in 28 cases(42.4%)the flexion-neutral fracture in 12 cases(18.2%),the flexion-internal rotation fracture in 16 cases(24.2%),the flexion-external rotation fracture in 6 cases(9.1%).32 simple single-condylar fractures were assigned to Group A,and 34 complex double-condylar fratures were assigned to Group B.2.There were statistically significant differences in the operation time and blood loss between simple single-condylar fractures(Group A)and complex double-condylar fratures(Group B).There were no significant differences in fracture healing time,knee function Rasmussen score and knee range of motion(P>0.05).There was no significant difference in excellent and good reduction rate(P > 0.05).There was statistically significant difference in excellent reduction rate(P<0.001).Conclusions:On the basis of the fracture morphologies and injury mechanism,the FTPFs can be divided into simple single condylar fractures and complex double condyle fractures.According to the Carlson approach,the posteromedial and posterolateral fracture fragments were exposed and fixed by the posteromedial and posterolateral S-shaped arc incision,single incision single plate fixation and multiple incision multiple plate fixation respectively,and excellent reduction and clinical results were obtained.Based on a clear and comprehensive understanding of different types of FTPFs,corresponding surgical treatment strategies and surgical approach are provided. |
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