Biomechanical Evaluation And Structural Optimization Of Far Cortical Locking Constructs For Long Bone Fractures

BackgroundWith the emerging concerns for more flexible and less stiff bridge constructs in the interest of stimulating bone healing,the technique of far cortical locking has been designed to reduce the stiffness of locked plating constructs while retaining construct strength.and targeted to improve locked plating construsts' stress concentration,stress shielding and inhibition of fracture healing issues.Provide more reliable engineering mechanics theoretical basis and reference data for far cortical locking construsts,and put forward objective design requirements and anti-fatigue design schemes for far cortical locking construsts,and promote the clinical application of this new dynamic fracture internal fixation structure is of great significance.Objective1.Describe and explain the mechanical mechanism of the far cortical locking construsts and compare the stress condition of the locking screws in locked platign construsts and far cortical locking construsts.2.Compare the fatigue behavior between the far cortical locking construsts and the locked plating constructs under physiological load and rehabilitation load during fracture healing.3.Put forward objective design requirements and anti-fatigue design schemes for the far cortical locking construsts.Materials and Methods:1.Establish an equivalent mechanical model of far cortical locking construsts and analyze locked plating construsts and far cortical locking construsts theoretically.2.Establish a numerical simulation model of locked plating constructs and far cortical locking construsts in non-osteoporotic and osteoporotic bones to conduct statics assessment and evaluate the safety of the constructs by the allowable stress method.And compare the fatigue performance of the two construsts through fatigue numerical analysis and life prediction.3.Verify the established numerical simulation models through statics tests and high cycle fatigue tests,and quantitatively analyze the fatigue damage degree of structure through defect detection.4.Use the Isight platform to intelligently optimize the far cortical locking screw for multiple working conditions.Results:1.In the far cortical locking construsts,higher stress is generated in the screw gap area and the proximal cortex area,and the maximum von Mises stress slightly exceeds the allowable stress.Compared with the locked plating construsts,the far cortical locking screws have higher maximum von Mises stress(normal bone:p<0.0001;osteoporotic bone stress:p<0.0001).2.Under physiological load and rehabilitation load,only the far cortical locking constructs have the problem of safety factor and life prediction less than 1,and the range of each group of locked plating construvts is much greater than 1.3.Structural damage was found only in the contralateral cortex locking structure.The maximum length of the crack was 11.43mm,the maximum depth was 0.45mm,and the maximum volume was 0.18mm3.There is a significant positive correlation between the damage factor of the fatigue numerical analysis and the structural damage volume of the defect detection(R2=0.5949,R2=0.5847).4.The optimized structure increased the safety factor to 5.Under various physiological loads,the optimized structure can achieve sufficient parallel interfragmentary motion,and the maximum von Mises stress of the structure is less than the allowable stress of the material.Conclusions1.The fracture risk of the screws in the far cortical locking constructs increases in the non-osteoporotic and osteoporotic diaphysis compared with the screws in the locked plating constructs.2.Fatigue numerical analysis will be a viable alternative method for studying the fatigue life and fracture mode of orthopedic implant systems and optimizing implant design.3.The sandwich structure composite metal screw optimized by multi-operation intelligent cycle optimization,and can provide a reliable anti-fatigue screw design for the far cortical locking constructs.