| Background and objectiveThe mandibular bone plays a vital role in the integrity of the human face structure and kinetic energy.The reconstruction method of mandibular defects caused by various reasons has gained great development.At present,vascularized free bone flaps are the most widely used in such treatment schemes.Compared with the vascularization of blood vessels that have been widely used and long-term follow-up,the use of femoral flaps is rare.One of the factors that cause this situation is concerns about the overall stability of the femur after surgery.Therefore,this study is committed to adopting the method of finite element modeling analysis,and preliminary inquiry of the feasibility of femoral flaps production from the perspective of biomechanics,and provides more feasibility for clinical circumstance of mandibular defects due to various limitations that the traditional bone flaps will be invalidated.MethodsFirstly,the femoral load under natural gait was simulated in Opensim.By collecting CT data from volunteers’ lower limbs,a normal three-dimensional model of the femur containing bone cortex and cancellous material was constructed using the image reconstruction software Mimics,as well as a three-dimensional model of femoral defects in different lengths,inner and outer sides,and arc angles of the femoral bone flap.ABAQUS software was used to mesh the above models,Simulate pressure and torsional load tests under superphysiological conditions in finite element analysis software,and analyze the biomechanical changes and stability of femoral bone flaps under different fabrication methods.ResultsWhen Opensim simulates the natural gait of human body,the maximum moment of force on the right femur is the single leg upright phase,and the corresponding vertical load is 1284.1N.Under the compression load condition,the stress on the femur is distributed on the lower surface of the femoral head and neck of femur,and on the upper part of the femoral body along the pubic muscle line.The maximum stress value is 19.5Mpa,and the maximum deformation value is 2.0mm;Under torsional load conditions,the stress on the femur is mainly distributed on the inner side of the lower half of the femoral shaft,with a maximum stress value of 2.6Mpa.When the finite element models with bone lengths of 60mm,90mm,120mm,and 135mm are subjected to the same load as the normal femur,the corresponding maximum deformation variables are 2.9mm,3.2mm,3.7mm,and 4.1mm;The maximum tensile stress under compressive load when the bone length is 135mm is 38.8Mpa,which exceeds the maximum tensile stress that the femoral material can withstand.Under compression load conditions,the maximum mises stress of the outer bone extraction method is 44.5Mpa,the maximum tensile stress is 39.1Mpa,and the maximum mises stress of the inner bone extraction method is 77.9Mpa,and the maximum tensile stress is 41.6Mpa.Whether in terms of maximum mises stress or maximum tensile stress,the maximum value of the outer bone extraction method is lower than that of the inner bone extraction method.In terms of the shape of the bone extraction incision,the maximum mises stress and maximum tensile stress of the arc-shaped incision bone extraction model under compression conditions are 27.0Mpa and 27.7Mpa,respectively,which are lower than the 28.8Mpa and 32.4Mpa values obtained during medial bone extraction.ConclusionAfter obtaining the femoral flap within an appropriate range,the overall stability of the femoral donor site is achieved.The finite element analysis results can serve as a reference for the range of bone extraction for the femoral valve.The length of the femoral valve extraction should not exceed 120mm,the lateral bone extraction method,and the arc shaped osteotomy incision are expected to reduce the risk of bone extraction. |
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