| Background:Femoral neck fractures are common clinical fractures,and the treatment of Pauwels Ⅲ femoral neck fractures is particularly difficult.Arthroplasty is the only option for treatment failure of femoral neck fractures,which imposes serious mental,physical and financial burdens on patients.Compared with Pauwels I and II,Pauwels type Ⅲ femoral neck fractures have a more inclined Pauwels angle and a stronger shear force at the interfragmentary,which requires higher biomechanical strengths of the internal fixation device.Cannulated screw is one of the commonly used internal fixation devices for the treatment of femoral neck fractures.The main factor affecting its biomechanical properties is the spatial configuration between the screws.Parallel inverted triangular screws are widely used in the treatment of Pauwels type I and II femoral neck fractures and can achieve good results.However,inverted triangular screws in the treatment of Pauwels type Ⅲ femoral neck fractures is prone to failure.In view of the complex mechanical environment of high shear in Pauwels Ⅲ femoral neck fractures,the F-shaped cannulated screw and Pauwels screw have changed the screw configuration based on the parallel inverted triangular screw.These provide new option for the treatment of Pauwels Ⅲ femoral neck fractures.Clinical application of F-shaped cannulated screws in the treatment of Pauwels Ⅲ femoral neck fractures has obvious advantages,but the difficulty of screw placement is still a problem that needs to be solved.However,there are few comparative studies on the biomechanics of the two new screw configurations and the traditional screw configuration in the treatment of Pauwels type Ⅲ femoral neck fractures,and the mechanical characteristics of the two new screw configurations are still unclear,and the corresponding relationship between basic biomechanical studies and clinical outcomes needs to be studied further.Objective:To explore the biomechanical advantages of F-shaped cannulated screws and Pauwels screws compared with traditional parallel inverted triangular screws in the treatment of Pauwels Ⅲ femoral neck fractures.To investigate the biomechanical characteristics of F-shaped cannulated screws and Pauwels screws,and to analyze the relationship between biomechanical strength and clinical efficacy of Pauwels Ⅲ femoral neck fractures,verify the advantages of the digital robotic intraoperative navigation and positioning system in clinical application and provides a biomechanical basis and potential clinical treatment options for the optimization of the treatment plan for Pauwels type Ⅲ femoral neck fractures.Methods:This study is divided into two parts,namely the biomechanical experimental research part and the clinical retrospective analysis research part.The specific methods are as follows:1.To construct a Pauwels Ⅲ femoral neck fracture model made of embalmed cadaveric bone and use three screw configurations（parallel inverted triangle screw,Fshaped screw and Pauwels screw）to fix them respectively.The axial stiffness,interfragmentary displacement of gradient pressure,failure load and interfragmentary torque at different angles were measured,and the biomechanical properties of the three screws were analyzed.2.Collect the clinical data of patients with Pauwels type Ⅲ femoral neck fracture who were diagnosed with Pauwels type Ⅲ femoral neck fracture in the Department of Orthopedics of China-Japan Union Hospital of Jilin University from January 2018 to January 2020 and were treated with F-shaped cannulated screws and inverted triangle screws respectively.Evaluate the clinical efficacy between the two screw configurations in the treatment of Pauwels type Ⅲ femoral neck fractures through the comparation of operation time,fracture healing time,full weight-bearing time,hip Harris function score and postoperative complication rate between the two groups.At the same time,the auxiliary role of the digital robot intraoperative navigation and positioning system for F-shaped cannulated nail implantation was explored.RESULTS:In the biomechanical experiment part,the axial stiffness of the F-shaped cannulated screw and the Pauwels screw are greater than that of the parallel inverted triangle screw（The axial stiffness of the F-shaped cannulated screw is 1.42 times that of the inverted triangular screw,and the axial stiffness of the Pauwels screw is 1.41 times that of the inverted triangular screw）.Interfragmentary displacement of Fshaped cannulated screw and Pauwels screw are smaller than that of inverted triangular screw.Interfragmentary torque of F-shaped cannulated screws is greater than that of Pauwels screws,and the torque of Pauwels screws is greater than that of inverted triangle screws.The failure load of F-shaped cannulated screws and Pauwels screws are greater than that of inverted triangle screws（The failure load of F-shaped hollow screws is 1.59 times that of inverted triangle screws,and the failure load of Pauwels screws is 1.70 times that of inverted triangle screws）.In the clinical retrospective analysis and research part,the operation time of the patients in the inverted triangle screw group was shorter than that of the patients in the F-shaped cannulated screw group.The fracture healing time of the patients in the inverted triangular screw group was longer than that of the patients in the F-shaped cannulated screw group.The postoperative weight-bearing time of the patients in the inverted triangular screw group was longer than that of the patients in the F-shaped cannulated screw group.The Harris function score of the hip in the inverted triangle screw group was lower than that of the F-shaped cannulated screw group.The postoperative complication rate of the inverted triangle screw group was higher than that of the F-shaped cannulated screw group.The digital robotic intraoperative navigation and positioning system significantly improves the screw placement accuracy of the F-shaped cannulated screw,and can improve the biomechanical strength of the internal fixation device for Pauwels Ⅲ femoral neck fractures.CONCLUSION:Using different screw configurations to fix femoral neck fractures has different biomechanical properties and changing the screw configuration can improve the mechanical strength of screw fixation for Pauwels type Ⅲ femoral neck fractures.From the biomechanical analysis,both the F-shaped screw and the Pauwels screw have better mechanical strength than the parallel inverted triangle screw configuration and are more suitable for Pauwels type Ⅲ femoral neck fractures treatment.Compared with F-shaped cannulated screws and Pauwels screws,the former has stronger anti-torsion ability than the latter,avoiding the rotation of the femoral neck fracture,the latter is stronger than the former in terms of axial load,and the vertically implanted screw has good anti-slip ability.Therefore,in clinical practice,the most suitable individualized treatment plan should be selected for different patients.The clinical application of F-shaped cannulated screws in the treatment of Pauwels type Ⅲ femoral neck fractures significantly shortens the fracture healing time,reduces the time to full weight-bearing,promotes the recovery of hip joint function and declines the incidence of complications compared with inverted triangle screws.The digital robot intraoperative navigation and positioning system realizes the precise implantation of F-shaped screws with high difficulty,which plays a huge role in promoting the progress of clinical treatment. |
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