The Assessment Of Structural Stability Of Five External Fixators And Closed Accurate Reduction Of Tibia Fracture

Purpose:(1) To compare the biomechanical properties of five kinds of external fixations(Unilateral, Hybrid, Ilizarov, Taylor and Ortho-SUV) for A2 tibiofibula fracture with mechanical experiment and finite element analysis.(2) To make a comparison between standard measurement and fit ellipse measurement in accurate assessment for reduction of tibia fracture with Stewart platform.(3) To investigate the clinical feasibility of closed reduction of tibia fracture using Taylor fixator with combination between Fit ellipse and three dimensional measurements.Methods:(1) Fifteen 30 cm long Unplasticized Polyvinal Chloride(UPVC) tubes were cut in the middle and lower 1/3 to establishing tibiofibular fracture models. Five kinds of external fixators were attached to these fracture models according to clinical habits. Then all the assemblies were tested by axial compression, torsion experiment and bending test with biomechanical experiment and finite element analysis.(2)Fifteen 3D printed plastic tibia bones were cut randomly in the middle and lower 1/3to establishing tibiofibular fracture models. Firstly, make a solid fixation to those fracture models with Stewart platform(Xinzhong ring fixation with bundled software was adopted in this research). All the assembly of bone model and external fixations were taken anteroposterior and lateral film, then imported the film to related software to measure the ramnant displacement with standard measurement and fit ellipse measurement. In order to eliminate the choice bias, three softwares were used,including CorelDraw, Trauma CAD and word united with vernier caliper. Finally,remnant displacement was imported into Xinzhong bounded software to calculating the digital prescription. Adjusting the length of the connected bar based on the prescription, taken anteroposterior and lateral film of tibia again to checking the reduction quality.(3) Two patients with closed tibia fracture were included in this research. At first, fractured fragments were operated with manual reduction, and then Taylor fixator was installed. The patients should be taken standard anteroposterior and lateral film, importing the film into software(word, Trauma CAD and CorelDraw)to identify the displacement of the fractured fragments. Secondly, the displacement parameter was inputted into Taylor fixator bounded software; to assisting calculate the recipe of accurate reduction. Thirdly, the patients should be taken the examination of CT scan, importing the CT files into Mimics to calculating 3D model. Accuratedisplacement was measured by spatial methods, taking into Taylor fixator bounded software to forming final recipe.Result:(1) The axial stiffness, torsion stiffness and bending stiffness in test of mechanics and simulation shows that Unilateral external fixator> Hybrid external fixator > ring external fixator(2) All the operations were completed; it revealed that improvement degrees of remnant displace and angle were 61.55%,71.70% based on the anteroposterior film; 77.19%, 79.22% based on the lateral film; 63.43%, 73.43%in the shorten aspect.(3) Totally two patients were included in this research, one is left limb injured, and the other one is right. All the fracture type is spiral fracture. Is a piece of lateral displacement of 4.26 mm respectively, 4.06 mm and lateral deflection13.5° and4.22 °, the lateral shift 3.42 mm and 4.28 mm before and after slice. For3.65 ° 2.57 mm and deflection Angle, axial displacement is2 mm, 2.16 mm. Reset after shift parameters: for the first time is a piece of lateral displacement of 0.34 mm and1.26 mm respectively, 0.25 mm and 0.52 mm. Lateral deflection is 4.84° and 2.42°,lateral shift 0.25 mm and 0.52 mm before and after the slice. For deflection Angle is0.81 ° and 1.08°; Axial displacement is 0.37 mm, 0.51 mm.Conclusion:(1) Comparing the simulation result with experiment, a good identity of results has been reached. Besides, five external fixations both could achieve better stabilities.(2) fit ellipse measurement has advantage in describing displacement of long bone, it has benefit in reduction with Stewart platform.(3)ellipse fitting combined with 3 d measurement that can guide Taylor accurately closed reduction and dry tibia fracture plane and is worth clinical popularizing widely.