股骨柄髓外设计对髋关节接触力影响的骨肌多体动力学研究

目的 探讨全髋关节置换(total hip arthroplasty, THA)假体股骨柄颈干角、偏心距和前倾角等设计参数对髋关节接触力的影响。方法 基于AnyBody软件建立THA骨肌多体动力学模型,参数研究股骨柄颈干角在±10°、偏心距在±20 mm和前倾角在±10°内变化时单因素或多因素对髋关节接触力的影响规律。结果 偏心距减小20 mm,最大髋关节接触力增加26.08%。颈干角增加10°,最大髋关节接触力增加5.99%。前倾角增加10°,会减小步态周期0%～24%时髋关节接触力,峰值减小19.16%;但会显著增加步态周期38%～70%时髋关节接触力,峰值增加67.78%。结论 在进行股骨柄髓外个性化设计时,在重建患者解剖参数的基础上,可以适当增加股骨柄的偏置距离,减小颈干角和前倾角,以避免增加髋关节受力。     

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。     

全髋关节置换术对股骨近端骨重建的影响

目的 采用Wolff骨重建理论分析全髋关节置换（total hip arthroplasty,THA）对股骨近端骨重建进程的影响。方法 根据骨重建控制方程,利用Python语言编写骨重建程序。在ABAQUS软件中分别建立术前股骨模型与术后股骨及假体有限元模型。对比THA手术前后骨重建进程,分析假体植入对THA术后中远期股骨力学性能的影响。结果 假体植入后,股骨近端应力持续降低,受力点由股骨头转移到假体,出现明显的应力遮挡现象。应力遮挡区域内骨丢失现象严重。股骨干皮质骨变薄,应力遮挡有所缓解。假体底端内侧受挤压,应力显著高于外侧,此处骨质分布不均。结论 THA术后股骨近端内侧出现明显的应力遮挡,导致骨丢失,造成假体松动;假体底端两侧应力水平存在差异,引起骨质分布不均,导致假体与股骨配合不紧密,造成术后患者大腿中段的疼痛。     

个性化钛合金短柄股骨假体的生物力学研究

目的通过有限元方法评价个性化钛合金短柄股骨假体的生物力学性能。方法在已验证有效性的股骨有限元模型基础上,模拟股骨颈基底部截骨,通过置入不同短柄股骨柄假体,分别建立4种人工髋关节置换(total hip replacement,THR)手术模型:SMF柄模型(模型A)、BE1柄模型(模型B)、MINI柄(模型C)、个性柄模型(模型D)。对4组THR模型施加同样的载荷和约束,计算分析模型von Mises应力分布和变形,比较各组模型的力学稳定性。结果所有THR模型变形都比生理状态模型要小。模型B、C变形量接近,模型A、D变形量接近。模型C应力峰值高于其他组模型,达到95.55 MPa,整体应力趋势是模型C模型B模型D模型A生理状态模型。结论个性化短柄股骨假体应力峰值、应力分布与SMF柄相当,应力分布合理,对股骨近端应力遮挡小,应力下假体整体变形度及剪切应力最小,其有效性和稳定性能满足人体生物力学要求,可为关节外科医生和假体研发人员提供参考。     

解剖型生物固定股骨柄假体的设计特征与临床应用效果

背景:Ribbed解剖型生物固定柄设计符合股骨生物力学特性,具有初始稳定性好、骨长入快及应力遮挡低等优点,获得满意的临床疗效。目的:探讨Ribbed解剖型生物固定股骨柄假体(Ribbed柄)的设计特征及其与临床疗效的关系。方法:对2010年3月至2012年3月因髋关节疾病采用Ribbed柄行全髋关节置换的患者进行回顾性分析。共获完整资料者52例(52髋),男20例,女32例;置换时年龄22-78岁,平均59岁。随访时间2-4年。评估置换前后Harris评分、置换后大腿疼痛率、术中骨折发生率、切口愈合情况、脱位及翻修等。影像学重点评估股骨柄髓腔充填率、股骨柄假体下沉、假体周围放射学透亮线、骨长入、应力遮挡及骨溶解等。结果与结论:术中股骨骨折发生率为6%;所有切口均一期愈合;无髋关节脱位及翻修病例;大腿疼痛率为6%,均于置换后1年消失;末次随访时,平均Harris评分由置换前48分提高到末次随访时96分。置换后X射线片示所有患者股骨髓腔充填满意,平均充填率:正位片上干骺端、中段和远端分别为91%,88%和86%,侧位片上干骺端、中段和远端分别为88%,85%和81%;末次随访时,49髋(92%)为稳定性骨长入固定,3髋为稳定性纤维长入固定,股骨侧及髋臼侧假体周围均未见骨溶解;5髋(10%)发生股骨柄假体下沉,但均小于2 mm;所有患者均出现不同程度的应力遮挡现象,其中1度31髋、2度19髋、3度2髋,无4度应力遮挡发生。提示Ribbed柄设计符合生物学固定要求,具有初始稳定性好、骨长入快及应力遮挡低等优点,可获得满意的临床疗效。     

非骨水泥全髋关节置换术中股骨内侧皮质骨的应力公布

目的　股骨近端术中骨折是影响非骨水泥全髋置换术的重要因素 ,本研究探讨股骨髓腔扩大后 ,不用锤打入假体柄 ,可减少术中股骨近端骨折的危险。方法　应用圆桶状应力仪 ,比较 6件扩大股骨髓腔后插入假体柄 ,股骨解剖试件内侧和前内侧应力分布情况。另比较 8件股骨试件 ,分别用锤打入和恒速机械负荷打入假体柄 ,测量各假体柄应力分布情况。在机械负荷打入假体柄中 ,模拟股骨周围的软组织 ,用力学试验机将假体柄恒速打入。结果　用股骨环轴定位测量 ,最大应力首先出现在股骨内侧和前内侧。最大应力的大小、方向和位置 (张应力或压应力 )各股骨…     

人工髋关节活体有限元建模及力学分析

背景：有限元分析最为广泛地应用于人工髋关节置换的研究,能够反映人工髋关节置换前后的应力分布情况。 目的：通过CT扫描图像建立人工髋关节置换后的三维有限元模型,分析假体和股骨的力学分布,提供研究活体内假体的评估方法。 方法：选非水泥型人工髋关节假体置换后患者1例,64排CT扫描髋关节,通过三维建模软件建立三维有限元模型,加载载荷1 500 N,分析假体和股骨的应力分布,并与体外建模和正常股骨有限元模型比较。 结果与结论：应用患者人工髋关节置换后CT扫描图像建立的三维有限元模型,加载后应力主要分布在股骨干上端1/3处,在股骨假体柄颈结合处,假体外侧,假体的远端与股骨接触处,是假体置换后应力在体内传递的真实反映。结果说明活体髋关节建模优于体外建模,不改变假体在体内的位置,人工髋关节活体建模是假体评估新方法。     

膝关节活动单髁假体衬垫形状及安装位置对置换后膝关节应力分布影响的有限元分析EI北大核心CSCD

在单髁置换手术中,市面上可供选择的单髁假体种类较多,常见的衬垫与股骨假体接触面一致性与否,会对置换后的膝关节应力分布产生不同的影响。单髁置换术后胫骨平台内侧断裂以及衬垫脱位是常见的两种失效形式,原因之一是单髁假体在膝关节中的安装位置不匹配,可能导致失效。故本文主要研究衬垫与股骨假体接触面的形状及单髁假体的安装位置对置换后膝关节应力分布的影响。首先,本文建立了正常人体膝关节有限元模型,通过应力和变形两种方式验证了该模型的有效性。其次,建立了两种不同形状衬垫膝关节假体模型(A型和B型),模拟分析在单腿站立情况下,两种衬垫5种内外翻安装位置的膝关节应力分布情况。结果表明,在1 kN轴向载荷下,衬垫峰值接触压力、前交叉韧带峰值等效应力、外侧半月板峰值接触压力,这3种参数A型均比B型小,5种内外翻安装位置下A型在内翻3°时衬垫变形、衬垫峰值接触压力、胫骨峰值等效应力、前交叉韧带峰值等效应力均最小。单髁置换时,建议假体内翻6°以内,选择A型或B型衬垫,需结合患者的其他因素综合分析选择。综上所述,本文研究结果或可降低单髁置换后衬垫脱位、胫骨内侧平台断裂的风险,以期为单髁假体设计提供生物力学参考。     

人工全髋关节置换术对天然股骨生物力学行为的影响

目的研究人工全髋关节置换术后股骨的变形及应力改变,同时研究关节置换术对股骨振型及固有频率的影响。方法选取1名正常男性青年进行股骨段CT扫描,构建正常股骨和术后股骨的有限元模型,对其进行步态情况下的生物力学行为分析、模态分析。结果 (1)关节置换术后假体柄部有明显的应力集中,并产生了应力遮挡;(2)术后股骨的峰值应力增大到原来的4.36倍;(3)约束模态的固有频率明显高于自由模态;(4)振型阶次越高,术后股骨与正常股骨固有频率的差距越大;(5)股骨的振型主要为弯曲和扭转,且置换前后振型变化不大。结论假体的植入改变了股骨原有的力学结构特性。在假体设计方面,必须考虑到股骨的振动特性,避免共振带来的假体松动。     

DDH患者全髋关节置换中股骨偏心距对骨肌多体动力学和接触力学的影响

目的探讨先天性髋关节发育不良(developmental dysplasia of the hip,DDH)患者全髋关节置换(total hip arthroplasty,THA)中股骨偏心距的生物力学影响。方法以1例CroweⅣ型DDH女性患者的相关数据为材料,基于骨肌多体动力学软件AnyBody,建立与患者对应的个体化THA下肢骨肌多体动力学模型,分析股骨偏心距在±20 mm内变化时髋关节力、外展肌力的改变。同时建立不同偏心距下股骨-S-ROM假体动态有限元模型,由骨肌模型计算的不同偏心距下水平匀速行走步态内的动态载荷被加载至相应的有限元模型,对S-ROM假体柄与袖套之间的应力、接触应力和微动进行分析。结果股骨偏心距±20 mm内的变化对髋关节力峰值影响较小,股骨偏心距减小会导致外展肌力峰值显著增加,股骨偏心距增大会导致柄的最大应力、接触应力和微动显著增加。结论 DDH患者THA中股骨偏心距改变对外展肌力和假体最大应力、接触应力与微动影响显著,医生应予以考虑。     

Biomechanical comparison of newly designed stemless prosthesis and conventional hip prosthesis--an experimental study

Local bone loss after implantation of traditional stem-type prostheses remains an unsolved problem during the long-term application of total hip replacement. The stress shielding effect and osteolysis were thought to be the two main factors that result in local bone loss after prosthesis implantation. A newly designed stemless cervico-trochanteric (C-T) prosthesis was thus developed to reduce stress shielding and osteolysis caused by the implantation of conventional stem-type prosthesis. Eight synthetic femora were implanted with C-T and porous coated anatomic (PCA) prostheses. Under 2,000-Newton load, the surface strains of proximal femora were compared between the intact, PCA press-fit femora and the C-T implanted femora with three different fixation modes: two-screw fixation, three-screw fixation, and three-screw combined with cement fixation. The results revealed that stress shielding in the C-T implanted femora was significantly eliminated compared to that of the PCA implanted femora (p<0.01). No statistical difference in strain magnitude was found for the C-T implanted femora among the three different fixation modes (p>0.1). The C-T implanted femur has more physiological strain distribution. Moreover, from the C-T prosthetic characteristic design, the localized osteolysis would be also reduced due to the overall coverage of neck-trochanteric area. The newly designed C-T prosthesis may be a useful alternative to the traditional stem-type prosthesis in the future.     

不同材料人工髋关节假体对骨界面应力分布及生物力学的影响

BACKGROUND: During joint replacement, different materials of prosthesis can be used. Different prosthesis can produce different effects and the stress distribution of bone interface. OBJECTIVE: To explore the effects of different materials on the stress distribution and biomechanics of the bone interface of artificial hip joint. METHODS: The CT scan of the hip was carried out. The image data were saved in DICOM format and processed by MIMICS software. The 3D finite element model of the femur was obtained by ANSYS. A three dimensional finite element model of the femur was made with the material properties of the femur. Three kinds of different replacement prosthesis materials (Co Cr Mo alloy, titanium alloy and composite materials) were selected, and the specific requirements of the actual joint replacement were selected, and different types of prosthesis were designed in CAE software. In the STL format, the prosthesis model was imported into MIMICS, and the femur and prosthesis were assembled. The stress status of different prosthesis was analyzed, and the stress shielding rates of exterior and interior sides of middle and lower parts of the femur, right to and 30 mm below lesser trochanter and right to lesser trochanter of the proximal femur were calculated. RESULTS AND CONCLUSION: Through three-dimensional finite element analysis, a direct and accurate model of the femur and the three-dimensional model of the prosthesis were established. According to the actual situation, material assignment of the femoral three-dimensional finite element model was conducted to obtain the corresponding model. Thus, the properties of different materials of the femur were shown visually. The femoral stress of cobalt chromium molybdenum alloy, titanium alloy, and composite material was simulated after replacement. Results found that the stress shielding rate can decrease in the middle and lower parts of the femur. After replacement, the femoral stress is higher than that of the intact femur. The experimental results show that the stress shielding of the joint was performed after joint replacement with Co Cr Mo alloy, titanium alloy and composite materials. Among them, the composite material is more close to the actual physiological environment of the human body, and it can better reduce the stress shielding effect, and is beneficial to the stress from the prosthesis to the femur.      

股骨近端假体周围骨折锁定加压接骨板的设计

目的 探索适用于国人全髋关节置换术(THA)术后股骨近端假体周围骨折(PPFF)内固定的锁定加压接骨板(LCP)的设计。方法 (1)回顾性分析2012年9月—2013年12月南京中医药大学附属常州市中医医院骨科收治首次行THA治疗的90例患者的影像学资料。在90例患者术后髋关节侧位X线片上测量股骨假体近端1/2假体柄后边缘与股骨后方外皮质、远端1/2股骨假体柄前边缘与股骨前方外皮质的最小和最大垂直距离。(2)选取20具股骨标本,测量股骨标本长度和周径。将20具股骨标本植入股骨假体,建立股骨假体模型;对其中5具标本模型进行宝石能谱CT扫描和三维重建,测量股骨假体近端1/2假体柄后边缘与后方股骨外皮质、远端1/2假体柄前边缘与前方股骨外皮质间垂直距离,测量股骨假体近端1/2和远端1/2垂直距离＞6 mm的股骨长度,测量股骨中段侧方的弧度。(3)依据90例患者和5具股骨假体模型的测量数据设计并数字化定制LCP。采用定制LCP固定5具股骨假体模型,通过大体和影像学观察LCP近段锁定螺钉与假体的关系,调整可能与假体接触的锁定螺钉的角度;再采用调整后的LCP固定10具股骨假体模型,观察LCP近段锁定螺钉与假体的关系,确定LCP的设计方案。结果 (1)90例患者术后髋关节侧位X线片测量结果:股骨假体近端1/2假体柄后边缘与股骨后方外皮质的垂直距离,最小(11.26±3.58)mm,最大(17.97±6.94)mm;远端1/2假体柄前边缘与股骨前方外皮质之间的垂直距离,最小(9.18±2.32)mm,最大(14.22±3.10)mm。(2)20具股骨标本的股骨长度为(41.67±0.24)cm,周径为(9.19±0.74)cm。股骨假体模型CT测量结果:假体近端1/2假体柄后边缘与股骨后方外皮质的垂直距离为(12.36±3.24 )mm;假体远端1/2假体柄前边缘和股骨前方外皮质的垂直距离为(8.14±1.21)mm。假体近、远端1/2与股骨外皮质垂直距离＞6 mm的股骨长度分别为(69.20±4.53)mm 和(57.31±3.82)mm。(3)LCP设计方案:LCP与假体近端1/2对应的部分设计3枚向后内成一定角度的锁定螺钉,对应3个锁定孔,分布于LCP中轴线偏后,向后内方向;与假体远端1/2对应的部分设计3枚向前内成一定角度的锁定螺钉,对应的3个锁定孔,分布于LCP中轴线偏前,向前内方向。采用设计、定制LCP固定股骨假体模型,LCP与股骨侧方弧度一致,锁定螺钉在股骨假体的后方或前方均实现双层皮质固定,角度合适。结论 根据国人资料设计、定制LCP,在股骨假体模型上获得有效的固定空间,为THA后PPFF的处理提供可行方案,但临床应用效果有待进一步验证。     

The biomechanical effect of anteversion and modular neck offset on stress shielding for short-stem versus conventional long-stem hip implants

Short-stem hip implants are increasingly common since they preserve host bone stock and presumably reduce stress shielding by improving load distribution in the proximal femur. Stress shielding may lead to decreased bone density, implant loosening, and fracture. However, few biomechanical studies have examined short-stem hip implants. The purpose of this study was to compare short-stem vs. standard length stemmed implants for stress shielding effects due to anteversion–retroversion, anterior–posterior position, and modular neck offset.Twelve artificial femurs were implanted with either a short-stem modular-neck implant or a conventional length monolithic implant in 0° or 15° of anteversion. Three modular neck options were tested in the short-stem implants. Three control femurs remained intact. Femurs were mounted in adduction and subjected to axial loading. Strain gauge values were collected to validate a Finite Element (FE) model, which was used to simulate the full range of physiologically possible anteversion and anterior–posterior combinations (n = 25 combinations per implant). Calcar stress was compared between implants and across each implant's range of anteversion using one and two-way ANOVA. Stress shielding was defined as the overall change in stress compared to an intact femur.The FE model compared well with experimental strains (intact: slope = 0.898, R = 0.943; short-stem: slope = 0.731, R = 0.948; standard-stem: slope = 0.743, R = 0.859); correction factors were used to adjust slopes to unity. No implant anteversion showed significant reduction in stress shielding (α = 0.05, p > 0.05). Stress shielding was significantly higher in the standard-stem implant (63% change from intact femur, p < 0.001) than in short-stem implants (29–39% change, p < 0.001).Short-stem implants reduce stress shielding compared to standard length stemmed implants, while implant anteversion and anterior–posterior position had no effect. Therefore, short-stem implants have a greater likelihood of maintaining calcar bone strength in the long term.     

骨表面再造数值模拟在人工股骨头假体优化设计中的应用

人工股骨头假体植入技术目前存在的主要问题之一是：植入假体存在远期等工发症,从而导致手术失败。对于引起松动的主要原因,通常人们认为是磨损磨屑和应力遮挡所造成的骨质吸收。因此,对人工股骨头假体植入物的结构进行优化是具有特别重要的意义,本文采用骨再造理论与有限元结合的方法,用计算机模拟人工股骨头假体植入股骨的再造行为,用截面吸收率和抗弯截面模量损失率定量分析假体所产生的应力遮挡效应,骨再造理论采用变能密度作控制变量的表面再造理论,有限单元采用二十节点等参数等单元。结果表明：在所讨论的假体模型中,三种围领形式的假体产生的骨吸收仅相差4％。三种长度直柄的假体所产生的骨吸收相差近30％,直柄长度的变化对应力遮挡效应有更显著的影响。     

髋关节置换前后不同步态下股骨应力分布

目的探讨人工髋关节置换(total hip replacement,THR)前后慢走及上下楼梯两种不同步态下股骨的生物力学性能,为髋关节假体的优化设计和制造提供理论基础。方法建立人工髋关节股骨的三维有限元模型,并进行有效性验证;计算慢走和上下楼梯时THR前后股骨的应力分布及应力遮挡率。结果慢走运动时,THR前股骨应力由近端到远端逐渐递增,在股骨中下段达到最大,最大应力为90.6 MPa;THR后股骨出现应力遮挡现象,股骨的应力幅值有所下降,最大应力为82.5 MPa,股骨近端假体周围大转子附近股骨遮挡率最大,总体遮挡率为14.9%~99.0%。此外,假体颈部出现过大的应力集中现象。上下楼梯运动时,股骨应力分布的变化规律与慢走运动时大体相似,但应力遮挡效应更为明显。结论植入假体后,上下楼梯时股骨近端出现较大应力遮挡,并且假体自身出现过大应力集中,会影响THR手术质量,建议病人在术后应尽量减少关节角变化较大的运动。     

Effect of implant material properties on the performance of a hip joint replacement

A composite material implant prosthesis for hip replacement has been developed. The design of the prosthesis substructure was based on investigation of the stress and strain fields that were developed in the human femur at the proximal end when a prosthesis stem had been inserted into it. The prosthesis stem structure was of unidirectional fibrous composite material core (graphite fibres in polysulfone matrix), wrapped with four layers of the same material but orientated at different angles. The orthotropic moduli of the outer layer are very close to the moduli of a human cortical bone in the vertical and circumferential directions. The moduli increased gradually from the outer layer to the inner core. A three-dimensional finite element model of the prosthesis and the bone has been constructed and loaded with the range of forces that might appear upon operation. The behaviour of the composite prosthesis and the femur was then compared with the intact femur and three other types of prosthesis materials, namely stainless steel, titanium, an isoelastic material and a hypothetical one with moduli identical to the cortical bone. The titanium has modulus of elasticity that is only half of the stainless steel. It was found that the composite prosthesis gave the best performance for most of the categories that were examined.     

Stress Transfer Modeling at the Interface of Cemented Prosthesis and Femur

Objective：To model the stress transfer at the interface of the cemented prosthesis and femur, an axisymmetric model of the interfacial stress transfer was established. Methods ： Assuming that the prosthesis, the cement and the femur were concentric cylinders with linear elastic and isotropic properties, distributions of the axial stresses in the prosthesis, the cement and the femur as well as the interfacial shear stresses at the prosthesis/cement interface and the cement/femur interface in the axial direction were obtained from the established axisymmetric stress transfer model. Results ： Interfacial failure was the main form for the prosthesis/cement/femur structure under external loads. Considering the residual thermal stresses, it was more likely to produce the mixed failure form than the pure shear failure form. Since the cement had a relatively high thermal expansion coefficient, the thermal effect accelerated the interface failure and thus aggravated the stress shielding effect. Due to a relatively high thermal residual temperature difference, the interfacial debonding and femur failure was more likely to occur for the cobalt-chromium alloy prosthesis material than the Ti-6A1-4V alloy prosthesis material. Conclusion： Assuming that the prosthesis, the cement and the femur are concentric cylinders with linear elastic and isotropic properties, distributions of the axial stresses in the prosthesis, the cement and the femur as well as the interfacial shear stresses at the prosthesis/cement interface and the cement/femur interface in the axial direction was obtained using the basic equations of axisymmetric elastic mechanics when the prosthesis bears the compressive stresses. Interface failure is the main failure form for the prosthesis/cement/femur structure under external loads. The thermal effects accelerate the failure of the prosthesis/cement interface and the cement/femur interface and the relaxation of the prosthesis, and then aggravates the stress shielding effect of the femur. Also, the thermal