有限元分析LISS-DF治疗股骨远端骨折近端螺钉单双皮质不同组合固定方式的应力分布*☆

背景：如何确定LISS-DF近端螺钉单双皮质合理搭配的固定方式,以便达到骨折两端螺钉固定强度的相对平衡,降低锁定钢板、螺钉和骨皮质之间的剪切应力,避免螺钉的应力集中,产生更有效的治疗结果是避免内固定失败的关键。 目的：对LISS-DF钢板治疗股骨远端骨折近端螺钉单双皮质不同组合的固定方式进行有限元分析及力学评价。 方法：在ANSYS 9.0软件中建立LISS-DF钢板固定股骨远端骨折(AO/OTA33-A3型)的实体模型和有限元模型。在近端螺钉单、双皮质不同组合固定方式下,通过模拟生理应力做轴向加压、扭转实验,同时评估近端螺钉的应力变化。 结果与结论：在16种不同组合方式中,当近端螺钉组合为1,3单2,4双皮质固定时,近端4枚螺钉的应力均值最小为24.219 75 N,同时剪切应力均值亦为最小,位移变化与其他组合固定方式相当且均较小。提示近端螺钉靠近骨折端处双皮质固定,其余螺钉依次单双皮质交替固定时,LISS-DF系统应力分散,抗拔出和抗扭转效果好,从而减少钢板螺钉早期的松动脱落。 关键词：应力分布;LISS-DF;股骨远端骨折;内固定;有限元分析 doi:10.3969/j.issn.1673-8225.2012.04.002     

Intramedullary femoral nails: one or two lag screws? A preliminary study

Failures of proximal femoral nails that treat unstable femoral fractures have been reported. In this communication, a finite element model to include a proximal femoral nail within a fractured femur was used to carry out preliminary investigations into configurations of single or double lag screws. The effects of the different types of fracture were investigated. The results show that in order to share the load evenly between two lag screws, a good configuration seems to be to have a slightly larger screw above the lower screw. This also ameliorates stresses in the nail at the lag screw insertion holes. However, using two screws in this way can lead to large stresses in the cancellous bone in the femoral head, and these stresses may be significant in the initiation of cut-out.     

强化螺钉治疗老年人重度骨质疏松Evans Ⅱ型股骨转子间骨折最佳骨水泥量的有限元分析

目的 探讨强化螺钉治疗老年人重度骨质疏松EvansⅡ型股骨转子间骨折的最佳骨水泥量。方法 选取2020年10月5日新疆医科大学第一附属医院1例73岁女性左股骨粗隆间骨折患者的双侧髋部及股骨CT资料,导入Mimics 20和 Geomagic Wrap 2017软件构建右侧股骨三维模型。使用Solidworks 2017软件建立强化螺钉模型,并将右侧股骨三维模型与强化螺钉模型按照常规标准手术技术进行装配、组合;使用Geomagic Wrap 2017软件在组合后的模型上模拟EvansⅡ型骨折,在股骨转子间骨折不同骨水泥量强化螺钉固定模型与EvansⅡ型骨折模型组装完成后,施加载荷。截取强化螺钉近端周围部分松质骨重新定义为骨水泥部件,按包裹水泥量的不同分别建立A模型（2 mL）、B模型（3 mL）、C模型（4 mL）、D模型（5 mL）、E模型（6 mL）5个模型组,设置材料参数、边界条件、施加载荷后储存为K文件,分别导入Ansys 2019软件中进行有限元分析。观察对比不同骨水泥量强化螺钉固定模型中骨水泥表面对股骨头近端松质骨的切割情况,股骨颈内翻、内旋角度,强化螺钉应力分布情况,以及股骨近端位移情况。结果 A、B、C、D模型组骨水泥表面对股骨头近端松质骨切割最轻微,E模型组切割程度最严重。A、B、C、D、E模型组中股骨颈内翻角度分别为5.2°、6.0°、4.5°、5.1°、2.6°,股骨颈内旋角度分别为1.1°、1.4°、0.9°、1.0°、0.4°,其中E模型组股骨颈内翻角、内旋角均最小。A、B模型组骨水泥量模型应力主要集中在螺钉和主钉连接处; C、D模型组骨水泥量模型应力大部分集中于螺钉和主钉连接处,应力有向主钉分散的趋势;E模型组骨水泥量模型应力主要分布在强化螺钉的尾端,6 mL骨水泥量强化螺钉模型载入股骨转子间骨折模型后,在股骨大粗隆处出现新的骨折。A、B、C、D、E模型组中,股骨近端位移分别为7.7、8.4、8.2、8.1、13.7 mm;其中E模型组股骨近端位移最大,出现了骨水泥漏,且在强化螺钉模型载入股骨转子间骨折模型后,在股骨大粗隆处出现新的骨折。结论 强化螺钉治疗老年人重度骨质疏松EvansⅡ型股骨转子间骨折,使用2~4 mL骨水泥量,具有较好的生物力学效应。     

股骨颈骨折空心钉内固定手术参数的优化分析

闭合复位空心钉内固定手术是目前治疗股骨颈骨折的常用方法,采用有限元方法对空心钉内固定手术进行力学综合分析,根据股骨近端力学实验的结果,建立股骨近端有限元分析模型,对可能影响手术效果的患者体重、骨折线角度、空心钉布局与角度等几个参数进行分组分析,提取骨折面、钉子的应力应变分析结果,获得了216组不同手术参数组合的情况下,影响术后愈合与承载能力的骨折端面的错位位移、钉孔底部应变、钉子最大应力、股骨最大应变四个参数,并进行综合分析比较,找到一组符合生物力学规律的内固定治疗参数,并应用于医疗机器人手术参数规划及手术效果的评价系统。     

股骨颈内固定系统固定股骨颈基底部旋转截骨的有限元分析

目的 采用有限元分析法比较股骨颈内固定系统（FNS）和空心螺钉作为治疗股骨头坏死的旋转截骨术中内固定装置的生物力学特性。方法 采用虚拟有限元建立中日友好医院分型L2型股骨头坏死模型,模拟前旋90°和后旋180°的旋转截骨术,分别模拟植入FNS（FNS组）及空心螺钉（空心螺钉组）,分析股骨近端截骨块、内固定装置、坏死区的应力分布及位移和股骨的位移。结果 前旋90°和后旋180°模型中,FNS组股骨近端截骨块、坏死区的应力和股骨近端截骨块、内固定装置、坏死区、股骨的位移均小于空心螺钉组。FNS组股骨近端截骨块和坏死区的应力峰值比空心螺钉组减少明显,近端截骨块应力峰值减小47.45%和13.64%,坏死区应力峰值减少44.96%和35.52%。结论 与空心螺钉相比,无论截骨后向前旋90°还是向后旋180°,FNS提供了更好的生物力学稳定性。     

强化螺钉骨水泥髓内钉固定治疗重度骨质疏松性股骨转子间Evans Ⅱ型骨折的生物力学有限元分析

目的 通过有限元分析探讨强化螺钉骨水泥髓内钉固定治疗重度骨质疏松性股骨转子间Evans Ⅱ型骨折的生物力学效果。方法 选取新疆医科大学第一附属医院骨科中心2020年10月5日收治的1例重度骨质疏松性Evans Ⅱ型左股骨转子间骨折患者的CT资料。患者女,73岁,身高160 cm,体质量56 kg。将患者髋部及股骨的CT数据在Mimics 20软件和 Geomagic Wrap 2017软件中进行提取、优化,得到右侧股骨三维模型;运用Solidworks 2017软件画出内固定模型并参考标准的手术技术进行股骨模型装配。将装配好的模型在3-Matic软件中进行截骨得到Evans Ⅱ型股骨转子间骨折模型,截取螺钉近端周围的部分松质骨设置为骨水泥部件,分别构建A模型[普通股骨近端防旋髓内钉（PFNA）内固定模型]、B模型（钉道强化PFNA内固定模型）及C模型（强化螺钉内固定模型）。按照患者CT数据及内固定的材质标准赋予相应的参数、条件,以及人体力学在股骨的受力及患者的体质量赋予载荷值分别储存,并利用ansys 2019软件中的Explicit Dynamics模块进行分析。观察指标：对比3种模型螺钉在股骨近端的切割程度、股骨颈向内翻角度、股骨颈内旋角度、应力在股骨的分布情况,以及股骨头近端移位情况。结果 3种模型螺钉在股骨近端骨水泥表面均由螺旋刀片四周向远端发生切割、形变、沉陷,程度由轻到重依次为C、B、A模型。股骨颈骨块内翻角度和股骨颈旋转角度,A、B模型均分别为0.37°和0.16°,C模型稍占优势分别为0.32°和0.15°。A模型应力主要集中在螺旋刀片和主钉交接处,B、C模型相较于A模型发生了应力转移,分散向骨水泥部位;C模型股骨骨折部分发生最大移位的距离为5.8 mm,相较于A、B模型（均为6.7 mm）减小。结论 强化螺钉内固定治疗重度骨质疏松性股骨转子间Evans Ⅱ型骨折较普通股骨PFNA及钉道强化PFNA具有更好的生物力学效果。     

有限元分析股骨颈骨折伴下后方不同程度骨缺损空心螺钉内固定后的稳定性

文题释义：有限元分析：是基于结构力学分析迅速发展起来的一种现代计算方法,通过计算机硬件及软件将载荷、形态、材料结构和力学性能较为复杂的整体划分为有限个简单的单元,进而充分反映整体内外部应力、应变、位移等力学参数的变化情况。通过将股骨近端及空心钉进行有限网格划分,施加载荷后可了解到股骨近端、空心钉每个网格的应力与应变情况。 创伤性股骨头坏死：各类因素引起股骨头血供下降或力学环境改变,导致股骨头内骨小梁坏死塌陷、髋关节疼痛及功能障碍的常见疾病。其中创伤性股骨头坏死与激素性股骨头坏死等不同,生物力学因素在其病情发生发展中发挥重要作用。骨小梁出现“损伤-微骨折-修复”交替反应,超过生理修复负荷,骨小梁修复重塑反应受阻,局部骨小梁走形杂乱无章,这是创伤性股骨头坏死重要的发病机制。 背景：空心螺钉固定为新鲜股骨颈骨折的首选治疗方法,但对于伴有骨缺损的患者,由于股骨近端力学传导及稳定性发生明显改变,易导致内固定物失效、骨折不愈合或延迟愈合等,因此生物力学研究具有重要的临床意义。 目的：利用有限元方法探究骨缺损后股骨近端的生物力学改变,比较不同构型空心螺钉固定内收型股骨颈骨折伴下后方不同程度骨缺损的生物力学效果。 方法：获取一名成年健康男性志愿者股骨近端CT扫描DICOM原始数据,利用MIMICS 10.01软件、Rhino3D NURBS软件制作内收型股骨颈骨折伴后下方不同程度骨缺损模型(无缺损模型、小缺损模型、中缺损模型与大缺损模型),在4组模型中各配置两种构型的空心螺钉(倒三角、正三角),装配完成后进行网格划分、材料属性赋值;通过ABAQUS 6.12软件建立股骨头中心和表面的耦合关系,对所有模型施加缓慢行走时的载荷和约束。 结果与结论：①无缺损模型的股骨颈内侧承受压应力,外侧承受张应力,股骨头应力分布较为均匀,随着股骨颈下后方缺损程度的增加,压力侧和张力侧空心螺钉、空心螺钉尾部及股骨头的应力峰值逐渐上升;②随着缺损程度的增加,空心螺钉压力侧应力峰值逐渐增加,在中、大缺损模型中,倒三角组高于正三角组(P < 0.05),在其余模型中两组之间无差异(P > 0.05);③随着缺损程度的增加,空心螺钉张力侧应力峰值逐渐增加,在无缺损与小缺损模型中,正三角组高于倒三角组(P < 0.05);在大缺损模型中,正三角组低于倒三角组(P < 0.05);在中缺损模型中两组无差异;④随着缺损程度的增加,股骨头应力峰值逐渐增加,3种模型中倒三角组与正三角组均无明显差异(P > 0.05);⑤随着缺损程度的增加,空心螺钉尾部应力峰值逐渐增加,在小、中、大缺损模型中,倒三角组高于正三角组(P < 0.05),在无缺损模型中两组无差异(P > 0.05);⑥结果表明,下后方不同程度骨缺损可显著影响股骨近端力学性能,对于无缺损或缺损程度较小的股骨颈骨折,空心螺钉倒三角构型的生物力学性能优于正三角构型,而对于缺损程度较大的股骨颈骨折,空心螺钉正三角构型的生物力学性能优于倒三角构型。 ORCID: 0000-0001-9190-2904(张成宝) 中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程     

3D Finite Element Analysis of a Man Hip Joint Femur under Impact Loads

Objective： The biomechanical characters of the bone fracture of the man femoral hip joint under impact loads are explored. Methods ：A biosystem model of the man femoral hip joint by using the GE （ General Electric） lightspeed multi-lay spiral CT is conducted. A 3D finite element model is established by employing the finite element software ANSYS. The FE analysis mainly concentrates on the effects of the impact directions arising from intense movements and the parenchyma on the femoral hip joint on the stress distributions of the proximal femur. Results：The parenchyma on the hip joint has relatively large relaxation effect on the impact loads. Conclusion：Effects of the angle δ of the impact load to the anterior direction and the angle γ of the impact load to the femur shaft on the bone fracture are given;δ has larger effect on the stress and strain distributions than the angle γ,which mainly represents the fracture of the upper femur including the femoral neck fracture when the posterolateral femur is impacted, consistent with the clinical resuits.     

Biomechanical analysis of retrograde intramedullary nail fixation in distal femoral fractures

This study employed both mechanical testing and finite element analysis to compare the stiffness variations among different intramedullary nail constructs used in the treatment of distal femoral fractures. Compressive and torsional experiments were conducted on a transversely, as well as an obliquely fractured sawbone femur restored with the retrograde intramedullary nail. Corresponding finite element models were established to evaluate the stress distributions around screw holes. The results showed that a perifracture screw could increase stiffness by 40% for the obliquely fractured femur, but that it played an insignificant role in stiffness improvement for the transverse fracture groups. Moreover, compared to proximal-screw fixation, distal-screw fixation could improve construct stiffness by 20%. The absence of one of the two distal screws would increase the screw-hole stress by 70%. Therefore, the distal screw around the metaphyseal region has a more important stabilizing effect in the femur-nail construct than does the proximal screw. A twisting stress pattern occurs on the unused screw holes of the metaphyseal region and induces a higher risk for fatigue fracture. The locking screw at the fracture site would be most effective only if it passed through the fracture gap to integrate the separated femoral pieces.     

医用316L不锈钢接骨板固定股骨的有限元方法分析

目的用三维有限元方法对医用316L不锈钢接骨板、螺钉及股骨进行应力计算,最终分析316L不锈钢接骨板对股骨的应力遮挡效应.方法首先建立医用316L不锈钢接骨板、螺钉及股骨的三维几何模型;网格划分后建立对应的三维有限元模型;在定义材料属性的基础上,加载边界条件,对站立位状态下的接骨板及螺钉强度进行有限元计算,同时分析股骨应力遮挡问题.结果通过对螺钉未加压状态和加压状态下股骨所受应力与站立位时正常股骨应力的对比,得出医用316L不锈钢接骨板及螺钉对股骨的应力遮挡效应.结论医用316L不锈钢接骨板及螺钉对股骨产生明显的应力遮挡效应,仅靠螺钉加压对应力遮挡效应的降低作用有限.本文建立的接骨板对股骨应力遮挡的分析方法可广泛应用于其他骨骼骨折应力遮挡的分析.     

不同力学激励对骨重建数值模拟的影响

目的研究采用应变能密度、等效应力、等效应变3种不同力学激励对骨重建数值模拟结果的影响。方法建立股骨近端的二维有限元模型,基于力学稳态理论的重建控制方程并结合有限元法,分别用3种不同力学激励模拟股骨近端的内部结构及密度分布,并与CT数据计算得到的骨密度值进行定量分析比较。结果 3种力学激励模拟得到的重建结果均能反映出股骨近端的主要特征结构,但采用等效应力作为激励时得到的股骨密度曲线图的趋势和数值都与CT图像数据更为一致。结论在骨重建力学调控机制中,应力可能起主导作用。准确预测和模拟骨重建过程将对矫形外科、骨伤治疗、人工假体的优化和个体化设计等临床实践提供理论依据。     

全髋表面置换术后与正常股骨近端生物力学比较

目的 通过三维有限元方法研究全髋表面置换术后股骨近端骨质区应力分布的变化。方法 采用64排螺旋CT扫描获得正常股骨近端图像数据,重建股骨近端的三维有限元模型,对金属对金属全髋表面置换术后股骨近端和正常股骨近端应力分布进行量化研究,分析术后生物力学环境的变化。结果 髋关节表面置换术后,股骨头近端上、前、后、下方4个区域均出现明显应力遮挡,应力峰值分别为0.60、0.57、0.66、0.79 MPa,遮挡率分别为99.80%、99.16%、98.92%、96.66%。股骨头远端大部分区域出现了应力增加,其中应力遮挡只出现在股骨头远端的后方区域,遮挡率为4.92%。术后股骨颈近端前方区域出现了应力增加,在上、下、后方区域出现了应力遮挡,遮挡率分别为16.48%、22.75%和7.83%;股骨颈远端下方区域出现了应力增加,其余区域出现应力遮挡。大粗隆区出现应力增加9.22%;小粗隆区域和股骨颈基底区出现应力遮挡,遮挡率分别为2.49%、14.44%。结论髋关节表面置换术后股骨近端大部分区域的应力分布和正常股骨相比非常接近,应力传递接近生理状态,可有效避免术后股骨近段明显的应力遮挡,同时保留了骨量,有利于患者正常的生理活动。     

Cement mantle stress under retroversion torque at heel-strike

The paper presents a theory of fixation failure and loosening in cemented total hip prostheses and proceeds to investigate this using an experimentally validated finite element model and two prosthesis types, namely the Charnley and the C-Stem. The study investigates the effects of retroversion torque occurring at heel-strike in combination with a loss of proximal cement/bone support and distal implant/cement support with a good distal cement/bone interface. A 3D finite element model was validated by comparison of femoral surface strains with those measured in an in vitro experimental simulation using an implanted Sawbone femur loaded in the heel-strike position and including a simplified representation of muscle forces. Results showed that the heel-strike position applies a high retroversion torque to the femoral stem that when combined with proximal debonding of the cement/bone interface and distal debonding of the implant/cement interface increases the strain transfer to the cement that may ultimately lead to the breakdown of the cement mantle leading on to osteolysis and loosening of the prostheses. Experimental fatigue testing of the implanted Charnely stem in a Sawbone femur produced cracks within the cement mantle that were located in positions of maximum stress supporting the finite element analysis results and theory of failure.     

新型无柄股骨假体应力分布的有限元分析

目的　通过对比传统有柄股骨假体的应力分布来研究新型无柄股骨假体的生物力学性能。方法　利用真实人体股骨上端的CT扫描图像，建立完整股骨、两个或三个固定螺钉的无柄假体、传统有柄假体的三维有限元模型。模拟人单腿直立的载荷情况，分析和比较每种模型的Von Mises应力分布。结果　(l)无柄假体股骨上的Von Mises应力比传统有柄假体和完整股骨上的都要高；(2)与传统有柄假体相比，防止了应力遮挡效应的产生。(3)两个或三个固定螺钉的无柄假体在股骨的Von Mises应力分布上没有明显差别。结论　新型无柄假体可以防止应力遮挡效应，和传统有柄假体相比能够使股骨上的应力分布更加符合实际的生理情况。     

不同材料赋值下股骨静力学有限元模型的力学仿真分析

文题释义： 材料赋值：由于人体骨骼结构复杂,由骨膜、皮质骨和松质骨构成,并且不同骨质的材料属性差异很大,因此在很多生物力学分析过程中为了简化模型,提高分析效率,很多学者在进行生物力学仿真研究中对骨骼模型采用了不同的赋值方法。 股骨模型材料赋值：给股骨分配不同的材料属性成为建立个性化有限元模型的基本步骤,而且材料属性分配将对分析结果产生很大的影响。但是目前有关不同赋值方法对人体骨科生物力学仿真分析研究的影响还很少有全面系统的研究。 背景：不同骨质的材料属性差异很大,因此在很多生物力学分析过程中为了简化模型,提高分析效率,很多学者在进行生物力学仿真研究中对骨骼模型采用了不同的赋值方法,而材料属性分配将对生物力学分析结果产生很大的影响。 目的：采用不同的材料属性赋值方法建立3种股骨有限元模型并进行有限元仿真分析,探究不同材料赋值方法对股骨有限元生物力学仿真分析的影响。 方法：采集志愿者股骨CT扫描数据,以DICOM格式文件导入Mimics医学影像处理软件重建股骨模型,对模型分别赋予3种不同的材料属性,即均一材料赋值、皮-松质骨赋值和灰度赋值,并将模型导入有限元分析软件Abaqus 6.14中,设置相同的载荷和边界条件进行应力及位移分析。 结果与结论：①3种股骨模型的应力输出结果相差不大,且均在合理范围内;②但是均一材料赋值股骨模型与皮-松质骨赋值股骨模型的最大应力主要分布于股骨干部位,而灰度赋值股骨模型的最大应力分布在股骨颈处,这也与现实状态下股骨骨折部位主要出现于股骨颈部位所吻合;③皮-松质骨赋值模型和灰度赋值模型输出的位移值基本一致;而均一材料赋值的股骨模型位移值最小,并且与其他2种模型位移量相差40%左右;④提示灰度赋值的方法能够较好地反映人体股骨的生物力学特性,从而可以更准确地模拟真实股骨的生物力学特征,这也为骨科生物力学进行有限元仿真建模提供了重要理论依据。 ORCID: 0000-0001-5075-7333(颜继英) 中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程     

基于三维有限元建模方法分析维医沙疗对兔股骨力学性能的影响

BACKGROUND:On the basis of modern design method and numerical simulation, studies can explore the action mechanisms of sand therapy in Uyghur medicine. OBJECTIVE:To explore a kind of non-homogeneous and isotropic biological bone finite element modeling method based on CT value, and to study the influence of sand therapy in Uyghur medicine on the mechanical properties of rabbits’ femur. METHODS:Eight adult New Zealand white rabbits were used to establish osteoarthritis models of right posterior femur with papain. These rabbits were divided into sand therapy group and control group. In the sand therapy group, after treatment with sand therapy in Uyghur medicine, rabbit femoral models were scanned with CT. The fault image data were imported into MIMICS software. 3D model of femur was generated. The meshing was done. The material properties were given. Three-point bending in the Ansys was simulated and solved. Simultaneously, the isolated three point bending tests were performed in all rabbit models. The corresponding deflection and the maximum stress values were obtained. Finally, the results obtained from the three-dimensional finite element modeling method were compared with the results obtained from the experiments. RESULTS AND CONCLUSION: (1) The deflection and the maximum stress obtained by the three-point bending simulation analysis with the three-dimensional finite element model of the rabbits’ femur were well correlated with the data obtained from the experiments. (2) These results indicate that the finite element modeling method is consistent with the structural and material properties of bone, which can be used to analyze the stress and deformation of bones.     

骨质疏松股骨转子间不稳定型骨折人工股骨头置换的三维有限元应力分析

BACKGROUND: Artificial femoral head replacement provides a new idea for the repair of unstable intertrochanteric fracture. Artificial prosthesis replacement may affect original femoral biomechanical stability and lead to a variety of adverse consequences.  OBJECTIVE: To analyze the stress distribution of femoral head replacement in the treatment of unstable femoral intertrochanteric fractures with three-dimensional finite element analysis. METHODS: One male old volunteer was randomly selected from population who underwent health examination. The left femur was scanned with spiral CT, and the three-dimensional finite element models of the human femur and prosthesis were established. The three-dimensional finite element model was used to simulate the actual working conditions of human climbing stairs, and the stress distribution of the bone channels around the surface of the femur and the prosthesis was analyzed with three-dimensional finite element analysis. RESULTS AND CONCLUSION: Under normal condition, the stress of the human femur was in a consistent state. Stress changed gradually from the proximal end to the distal end. The stress of the prosthesis was concentrated in the middle section. The prosthesis of inner stress distribution was analyzed to obtain stress distribution of prosthesis and femur cancellous bone interface. The analysis found that stress change trend was consistent. The results suggest that artificial femoral head replacement does not have a significant effect on the overall stress distribution of the human femur, and the overall stress distribution does not change, and the maximum stress region is located in the middle of the whole femur. After the reconstruction, the stress concentration of the femur is not observed.        

Comparison of an inhomogeneous orthotropic and isotropic material models used for FE analyses

Finite element (FE) analysis has been widely used to study the behaviour of bone or implants in many clinical applications. One of the main factors in analyses is the realistic behaviour of the bone model, because the behaviour of the bone is strongly dependent on a realistic bone material property assignment. The objective of this study was to compare isotropic and orthotropic inhomogeneous material models used for FE analyses of the "global" proximal femur and "small" specimens of the bone (cancellous and cortical). Our hypothesis was that realistic material property assignment (orthotropy) is very important for the FE analyses of small bone specimens, whereas in global FE analyses of the proximal femur, this assignment can be omitted, if the inhomogeneous material model was used. The three-dimensional geometry of the "global" proximal femur was reconstructed using CT scans of a cadaveric femur. This model was implemented into an FE simulation tool and various bone material properties, dependant on bone density, were assigned to each element in the models. The "small" specimens of cortical and cancellous bone were created in the same way as the model of the proximal femur. The results obtained from FE analyses support our above described hypothesis.     

In vitro biomechanical evaluation of antegrade femoral nailing at early and late postoperative stages

The present study addresses the question of evaluating, by combining both experimental and numerical methods, the stress/strain distribution within a standardized composite femur implanted with an anterograde intramedullary nail. A transverse diaphyseal fracture has been introduced in order to evaluate the implant response in the early postoperative clinical stage. By comparing these experimental data with those obtained in the fully healed stage, in which the bone continuity had been recovered, it was possible to get information on load sharing between the bone and the intramedullary nail, location of high strain concentrations, bone relative motion at the fracture site, and stiffness reduction caused by bone discontinuity. Experimental data were correlated with those predicted by a validated 3D finite element model of the complete implant/femur assembly to investigate the full field stress distribution either in the cortical bone, in the nail or in the locking screws. The obtained results suggest that full weight bearing in the immediate post-operating stage should not be allowed since high stress levels are generated in the outer shell of the cortical bone either around the proximal screw hole or the upper locking screw hole. Long-term implant reliability should be guaranteed instead, since after fracture consolidation equivalent von Mises stresses never exceed critical levels neither in the bone nor in the implant.     

采用体绘制方法建立人股骨三维有限元模型及其应力分析

背景：目前股骨三维有限元研究建模方法有多种,而采用体绘制分体建模方法还未曾报道过。 目的：采用体绘制方法建立股骨三维有限元实体模型,对所建实体模型模拟力学载荷得出股骨应力分布,并与既往股骨力学实验比较,评估体绘制方法的可行性。 方法：将CT扫描图像去噪等预处理后,采用体绘制技术,利用Mimics和Ansys软件建立人股骨有限元模型,并在Mimics软件中赋予股骨材质,并模拟人体正常站立位时股骨载荷情况。 结果与结论：采用体绘制方法建立的人股骨三维有限元模型,包括皮质骨、松质骨及髓腔解剖结构,网格化后共生成63 900个节点,43 552个实体单元;模拟载荷显示股骨压应力区域主要集中在股骨内侧、尤其是股骨距部位,张应力主要集中于股骨颈外侧、股骨干外侧。表明体绘制方法可以建立高仿真、接近股骨解剖结构股骨三维有限元模型实体模型,可以探索股骨的内部结构,展现其内部细节,模拟股骨生物力学分布。关键词：体绘制;股骨;实体模型;有限元;力学分布 doi:10.3969/j.issn.1673-8225.2012.17.003