定制型膝关节假体修复股骨远端骨缺损假体柄长的有限元分析

以男件健康自愿者右股骨的CT图像为原始数据,分别建立柄长150,160,170,180,190 mm的定制型膝关节假体修复重建股骨远端40%骨缺损的三维有限元模型,对应的股骨十截骨长度分别为160,170,180,190,200 mm,加载平地慢速(3 km/h)行走步态周期中F肢4倍体质量负荷.皮质骨最大应力出现在股骨近端内侧,随假体柄长由150 mm增加至190 mm,应力最大值由106.8 MPa减少甭91.78 MPa.骨水泥最大应力出现在骨水泥上1/4段内侧,应力最大值由27-2 MPa减少至19.06 MPa.假体柄承载最大负荷,应力值变化不明显.5个模型出现骨折、骨水泥碎裂及假体柄断裂概率均较小.提示定制型膝关节假体重建保肢符合人体生物力学规律;短柄假体可引起骨、骨水泥应力集中,重建后发生骨折、骨水泥碎裂风险较高,而增加柄长对骨的应力遮挡水平也相应增大.     

股骨柄假体的二维生物力学评价与优化选择

背景:人工髋关节置换术前选择假体时,不仅要考虑在几何学上达到与患者股骨髓腔的匹配,而且还要在生物力学性能上达到最优,这对提高全髋关节置换术后疗效,具有较现实的意义.目的:对4组与股骨匹配的股骨柄假体进行生物力学的评价,寻找与正常股骨力学分布最为接近的股骨柄假体.设计:对比观察.单位:同济大学附属东方医院骨科、解放军第二军医大学长海医院骨科、上海交通大学机械与动力工程学院.材料:实验于2004-12/2005-10 在上海交通大学机械与动力工程学院生命质量与机械工程实验室完成.选用无髋部疾患、股骨近端形态正常志愿者(男性,40岁,身高175 cm,体质量78 kg)的股骨拍摄标准正位X射线片,并以DICOM格式存入存贮器中.志愿者签署知情同意书,同时报医学伦理委员会审批.模板:Ⅰ号假体:Zimmer versys Fiber Metal Taper11#;Ⅱ号假体:Plus APL 2#;Ⅲ号假体:Welink Ribbed system cementless11#:Ⅳ号假体:Lima F2L 1#.方法:在Matlab中导入股骨近端X射线正位片及4组股骨-股骨柄假体模板的bmp格式的图像文件,分别提取股骨、带假体模板的股骨二维轮廓数据,利用ANSYS软件建立股骨、股骨-股骨柄几何模型及二维非线性有限元模型,负荷加载后对股骨近端的应力分布进行分析、比较.主要观察指标:股骨近端的应力分布.结果:Ⅰ,Ⅳ号假体对所研究的股骨而言其应力大小及分布与正常股骨相近,但两者相比Ⅰ号更为接近,应为最佳选择.结论:通过基于X射线片与模板的股骨柄假体二维生物力学的分析比较,可对股骨柄假体的生物力学性能作出评价,为假体的优化选择提供依据.     

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1500N,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。     

股骨柄假体表面多孔层孔隙形状改造的动物实验

目的:观察菱形孔隙及方形孔隙两种不同几何形状多孔层设计股骨柄假体的生物学固定效果,分析孔隙几何形状对假体生物学固定的影响。方法:于2003-03/2004-04在中山大学医学部动物中心完成全部实验过程。纳入24只成年杂种犬,雌雄不拘,以随机数字表法均分为2组,即菱形孔隙组及方形孔隙组,各12只。自行设计完成犬骨重建型股骨柄假体,将股骨柄假体近2/3段表层改成两种不同几何形状的粗大多孔层结构,钛丝表面假体,钛丝直径改为1.0mm,孔径加大至5.0mm,孔隙度可达80%。菱形孔隙组钛丝沿股骨假体柄呈螺旋形排列并斜形相交,方形孔隙组钛丝沿股骨假体柄纵横排列并直角相交。均将假体表面孔隙内充填自体股骨头颈骨质制成的骨泥后,行右侧人工股骨头置换术。术后6个月行X射线摄片、组织学检查及生物力学测试,以股骨近端骨吸收情况、新生骨长入深度及孔隙充满度、假体-骨界面最大剪切强度测量为评价指标,了解假体内外成骨和固定情况。结果:菱形孔隙组及方形孔隙组各12只,实验中手术不成功或术后生存不够观察时间的均予实验过程中随时补足,最终每组12只进入结果分析。①组织学观察显示菱形孔隙组多孔层孔隙内最大骨长入深度及孔隙内新生骨平均充盈率均优于方形孔隙组(3000,2450μm;96.2%,71.6%)。②菱形孔隙组假体-骨界面最大剪切强度高于方形孔隙组,差异有显著性意义[(8.57±0.51),(3.15±0.41)N/mm2,P<0.01]。③菱形孔隙组6个月标本肉眼及X射线观察股骨近端无明显骨吸收,优于方形孔隙组;所有实验犬术后伤口缝线任其自行脱落,除1只伤口感染并于术后17d死亡外,余实验犬均伤口愈合良好,未出现不良反应。结论:股骨柄假体表面不同几何形状多孔层设计能影响其生物学固定效果,菱形孔隙设计优于方形孔隙。     

双锥面高抛光股骨柄治疗老年股骨颈骨折的临床应用

目的探讨抛光型股骨柄假体在老年股骨颈骨折假体置换中的应用。方法采用双锥面高抛光股骨柄段体治疗老年股骨颈骨折63例67髋。股骨假体固定采用第二代骨水泥技术,分析其临床效果。结果所有患者术后均无髋关节脱位发生。双下肢长度差异为（3.1±1.2）mm。术后3个月髋关节Harris评分为（86±10）分。结论抛光型股骨柄假体通过其在假体设计和假体固定上的改进,可以比较好地解决老年人股骨颈骨折假体置换中所遇到的假体固定困难等问题。     

人工股骨头置换治疗骨质疏松股骨转子间不稳定骨折的有限元应力分析

背景:通常的力学实验手法基本上无法直接应用于人体且模型间可比性低,对人体的力学行为进行有限元数值模拟就成为深化对人体认识的一种有效手段。目的:运用计算机模拟骨质疏松股骨转子间不稳定型骨折人工股骨头置换,并做置换后股骨及假体的应力分析,评估置换后假体的初始稳定性。方法:对志愿者双下肢进行薄层CT扫描获得股骨数据,图像处理软件Mimics11.1进行图像处理后数据导入建模软件UG4.0建立股骨三维模型;假体柄与股骨间行布尔运算,分为正常关节置换组和转子间骨折人工关节置换组,观察两组材料赋值、定义接触、受力加载、应力分析等情况。结果与结论:人工关节置换改变了股骨的受力方式,股骨转子间骨折关节置换后的假体稳定性较好,在正常载荷下人工关节稳定。     

生物固定型股骨柄假体的几何系统设计

生物固定型股骨柄假体要达到取代病变骨组织、完成被替代部分的动力学功能的目的,就必须要求假体在结构设计上达到两个指标要求,即:与股骨髓腔良好的结构相容性(假体与股骨良好的匹配、稳定密合)和与骨组织的生物力学相容性。股骨柄假体几何设计体现了临床解剖学、统计学、材料力学、机械设计及计算机虚拟设计与分析等技术的综合应用,对设计者综合知识要求较高。股骨柄假体的几何设计是设计与评价相结合的并行工程,系统的思路对设计人员至关重要。文章从设计角度出发,为股骨柄的几何设计提供系统思路;基于数理统计原理,阐述股骨柄分型的方法;通过对人体股骨解剖及其生物力学环境特征分析探索出股骨柄几何形状确定的一般原则;并运用CAD/CAE虚拟设计与分析系统以及生物力学试验等必要的评价来说明股骨柄假体几何设计的系统思路。     

C．F．P．与THA术后股骨近端生物力学的比较研究

目的 通过在股骨标本中模拟C.F.P（collum femoris preserving.保留股骨颈）假体置换术及THA（total hip arthroplasty,全髋关节成形术）,进行股骨近端的生物力学实验并进行比较,以了解C.F.P假体的生物力学特点,为其进一步的研究和应用范围提供坚实的理论依据.方法 取4副8根新鲜成人股骨标本,将其作为正常组.①廊力分析：分别在股骨标本上粘贴电阻应变片.通过静态电阻应变仪测定300N载荷下各测点的应变值.正常组做完后,将股骨标本按左右侧分为2组,每组4根.左侧安装C.F.P.人工髋关节假体,右侧安装传统生物型人工髋关节假体,重复上述实验.②疲劳实验：将安装了假体的股骨标本置于万能材料实验机的工作平台上.以300HZ的实验速度对标本进行压缩疲劳实验.最大的加载载荷为0.75kN.最小的加载载荷为0.075kN.直到股骨标本出现裂纹破坏为止.得出在人体正常的循环载荷下,假体组中股骨标本出现裂纹破坏所需的循环次数.结果 实验结果表明,C.F.P.假体组的张应力值差和压应力值差均明显小于传统生物型假体组,差异有显著性意义（P〈0.05）,更接近于正常组.在人体正常的循环载荷下,C.F.P.假体组中股骨标本出现裂纹破坏所需的循环次数多于传统生物型假体组,差异有极显著性意义（P〈0.01）.结论 与传统生物型假体相比,置入C.F.P.假体后股骨上段的应力分布和传导更接近正常生理状态,更符合人体生理需求.C.F.P.假体的使用寿命比传统生物型假体更长.C.F.P.人工髋关节假体适用于股骨颈完好、无骨质疏松的患者,尤其是年轻、运动量大且将来面临再次置换的患者.     

采用锥形沟槽式股骨组配柄假体行股骨侧翻修

背景:组配式股骨柄翻修假体在理论上被认为能够克服骨水泥固定型股骨柄假体或生物学固定型非组配式股骨柄假体存在的各类缺点,一些文献也初步证实这类假体能取得更为满意的疗效.目的:回顾性分析采用锥形沟槽式股骨组配柄假体行全髋股骨侧翻修的效果.方法:2000-05/2005-08苏州大学附属第一医院收治全髋股骨侧翻修患者19例(21髋).翻修前诊断均为股骨柄假体合并臼杯假体的无菌性松动.股骨侧骨缺损按Paprosky标准,诊断为Ⅱ型缺损者4髋,Ⅲa型缺损者14髋,Ⅲb缺损者3髋.全部患者的股骨侧翻修均采用利马锥形沟槽式股骨组配柄假体,股骨柄假体为钛合金制造.对翻修效果进行随访观察.结果与结论:所有假体均获初始稳定,未发生感染、脱位等并发症.随访5～10年,末次随访Harris评分维持在(92.2±3.5)分.X射线片显示翻修柄获广泛骨长入达骨性稳定者20髋(95%),纤维性稳定者1髋(5%).所有患者的近段骨缺损植骨区均显示广泛性骨修复.翻修柄在正、侧位X射线片上的髓内充填率分别达80%和70%以上者18髋(86%),< 80%和70%者3髋(14%),全组假体平均下沉2.4 mm.至今未见因假体松动或其他原因需行再翻修治疗患者.提示采用锥形沟槽式股骨组配柄假体行全髋股骨侧翻修,必须注重手动扩髓等方法预防骨折,合理的髓内充填和近段组件调整以预防假体下沉和脱位,以及锥形连接处近段的植骨重建等技术关键,才能取得更为满意的效果.     

不同骨质密度下生物型及骨水泥型股骨假体置入后的三维有限元分析

背景:患者自身骨质情况往往决定髋关节置换手术中假体的选择,目前对假体的选择尚无金标准,而通过计算机二维有限元分析、模拟对比力学实验,对不同骨密度下股骨假体类型进行选择,将更具科学性.目的:通过计算机三维有限元分析,选择不同骨密度下的股骨假体类型,并行模拟对比力学实验,从而确定临床全髋关节置换选择股骨假体的年龄标准.设计、时间及地点:开放性实验,于2006-09/2007-05 在吉林大学第一临床医院骨科研究所和吉林大学生物力学研究所完成.材料:成人新鲜股骨尸体骨.方法:利用Solidworks计算机软件建立人体股骨三维有限元模型.利用已有公式转化计算不同年龄段下骨质的密度及弹性模量,分别输入计算机.模拟人体单足站立状态,对重建的股骨模型进行力的加载与约束.主要观察指标:测量生物型和骨水泥型股骨假体在不同股骨密度下的应力分布及初始微动等生物力学特性.结果:生物型股骨假体上的整体应力在男性30～60岁年龄段分布相对较均匀,初始微动变化较小;在女性40～55岁年龄段分布相对较均匀,仞始微动变化较小.骨水泥型股骨假体上的整体应力在男性60～70岁年龄段分布相对较均匀,初始微动变化较小;在女性55岁后分布相对较均匀,初始微动变化较小.结论:计算机三维有限元分析及模拟对比力学实验结果提示,男性小于60岁,女性小于55岁使用生物型人上股骨假体优于骨水泥型人工股骨假体.     

Primary stability in cementless femoral stems: custom-made versus conventional femoral prosthesis

OBJECTIVE: To compare a custom-made femoral stem with a conventional cementless stem for initial stability in human femurs. DESIGN: The bone-femoral prosthesis interface motion was measured in vitro using displacement transducers. Combined axial and torsional loads simulating single-leg stance, loading were applied. BACKGROUND: The custom-made prosthesis is a cementless femoral stem fabricated from the patient's CT-reconstruction. To justify its clinical use its design has to be tested regarding his primary stability. METHODS: Seven pairs of human cadaveric femurs were used for testing the custom-made prosthesis versus a conventional cementless stem. Subsidence, rotation and interface motion were measured with load cycles up to 2000 N. RESULTS: The critical interface motion of 150 microm for the cementless prosthesis was not exceed for both types of prosthesis. The custom-made prosthesis enlarged in its metaphyseal part showed a decrease of dynamic micromotions and rotation behavior in the proximal region compared to the Alloclassic prosthesis stem. CONCLUSIONS: The initial stability of the custom-made femoral stem was comparable to that of a conventional femoral stem. RELEVANCE: The data set for initial stability justifies the clinical use of a custom-made femoral stem in primary hip replacement. An individualized stem fit into the endosteal cortical bone decrease micromotion.     

Design and testing of a flexible hip prosthesis

A prosthesis with flexibility and optimal proximal fit was constructed in titanium alloy. The aim was to create the same elasticity as in the femoral shaft. Distally it was cylindrical with slots in the stem and a spacer made of polymer was placed in the slots. The proximal part of the prosthesis was wedge-shaped in both planes and a collar with a conical contact surface to bone was used. Pure titanium was plasma sprayed on the upper part as well as underneath the collar allowing bony ingrowth. A test jig was constructed and 10 million cycles with 4000 N loading was planned. The prosthesis broke after 600 000 cycles and it was a typical fatigue failure. A commercially available flexible prosthesis was tested as a reference and broke after 29 000 cycles.

It is concluded that construction of a flexible hip prosthesis using metal with reasonable security against fatigue failure breakage is difficult, and we are somewhat doubtful if it is possible.     

Influence of muscular contractions on the stress analysis of distal femoral interlocking nailing

BACKGROUND: In the literature, the commonly assumed loading conditions on the proximal femur are hip compression and/or gluteus contractions. However, no study has discussed the influence of muscle forces on failure of distal nail holes and locking screws. METHODS: This finite-element study analyzed the influence of muscular contractions on stress analysis of distal nail holes and locking screws. Three loading conditions were used for comparison, comprised of either hip compression alone or with muscle contractions. The head displacement of intact and fractured femur, the nail and screw stresses vs. fixation depth, and the stress distribution at the distal nail-screw interfaces were chosen as the comparison indices. FINDINGS: The addition of trochanteric and diaphysial muscles showed the more physiologically reasonable displacement of the femoral head. However, all loading conditions consistently showed the hole and screw stresses increase as the nail was inserted deeper. The stress distribution at the distal nail-screw interfaces was remarkably different under the condition of with or without the muscular contractions. The exertion of muscles predicted the fatigue cracking originated at the edge of the nail holes on the medial rather than lateral side. INTERPRETATION: Only hip compression and/or gluteus contraction generated a characteristic bending stress pattern and medially deflected nail curvature. Comparatively, the trochanteric and diaphysial muscles stabilized the femoral head and resulted in the higher stress concentration at the distally medial nail-screw interfaces. However, further experimental and clinical studies, focusing on the failure sites of the distal femoral hardware, should be undertaken to validate such findings.     

股骨侧远端生物固定假体在高龄患者全髋关节翻修中的应用

背景:对高龄患者行人工全髋关节翻修时如何正确选择股骨侧假体固定方式,可否应用组配式股骨假体处理此类难题?目的:验证股骨侧生物固定型假体在老年人全髋翻修后的效果。方法:采用远端固定生物型股骨假体对11例75岁以上股骨侧假体松动患者进行翻修。11例股骨骨缺损根据Paprosky分型,Ⅰ型2髋,Ⅱ型2髋,ⅢA型7髋。结果与结论:11例患者均随访16个月以上,患者Harris评分从翻修前的37分(22～49分)改善至随访结束时的89分(78～92分),优良率>90%,无患者发生再次松动。翻修后X射线片显示假体周围骨质密度和厚度明显增加。提示远端固定生物型假体可在股骨远端髓腔内获得可靠的轴向及抗旋转初始稳定性,尤其适用于伴有近端骨缺损的高龄患者的翻修治疗。     

Initial stability of fully and partially cemented femoral stems

Objective. To test the initial stability of a newly designed partially cemented femoral stem in comparison with a fully cemented conventional stem.

Design. An in vitro study to determine the interface motion between femoral stem and bone as a response to loading.

Background. The aim of the new prosthesis design is a proximal load transfer by a defined partial cement fixation in the proximal femur region and a slim prosthesis stem in the distal region. Before a clinical study can be started, the new stem has to show an initial stability comparable to that of fully cemented prostheses.

Method. Six paired fresh cadaveric femora were used for the testing of the new partially cemented stem (Option 3000, Mathys Orthopaedics, Bettlach, Switzerland) and a fully cemented stem (Weber Shaft, AlloPro, Baar, Swizerland). Under cyclic loading up to 1600 N hip joint forces, the interface motion between implants and bone was measured at six locations.

Results. Both stems showed uncritical interface motions below 43 μm. However, the Option 3000 stem exhibited significantly smaller motions in the proximal region and slightly larger movements in the distal regions than the Weber prosthesis.

Conclusions. The new type of partially cemented stem provided a comparable initial stability to the fully cemented Weber prosthesis.Relevance

The high initial stability of the Option 3000 stem justified the clinical use of the new implant. More than 100 implantations in the last three years, with very good preliminary clinical results, support the preclinical findings.     

Changes in strain distribution of loaded proximal femora caused by different types of cementless femoral stems

BACKGROUND: A number of clinically used total hip femoral implants are claiming a more or less physiologic load transfer, mostly without providing experimental data. To compare three clinically cementless total hip stems of fundamentally different design, the strain distribution before and after insertion in human cadaver femora was measured in vitro. METHODS: A conventional straight stem based on a distal anchorage concept, a so-called "anatomic" stem designed to have a proximal force transmission and a "stemless" femoral neck prosthesis were evaluated under similar loading conditions. Strain distribution was measured with tri-axial strain-gauge rosettes before and after implantation of the stems. The same bending moment was used in all femora tested to compare magnitude and direction of the resulting strains. FINDINGS: The straight and the "anatomic" stem both led to a decrease of the longitudinal strains in the proximal femur, while the femoral neck implant mainly led to an increase of measured strains on the lateral side of the greater trochanter. The observed medial strains were closer to physiological values in the "stemless" prosthesis than those of the two full-stem prosthesis. INTERPRETATION: The decrease in strains seen in the proximal region of the femora with implanted conventional hip prosthesis corresponds well to the decrease of bone density in this region noted in clinical follow-up studies. The more physiological strain at the inferior base of the neck seen in "stemless implant" may induce a remodelling process that better retains bone stock in that area. However, the increase of strains noted after implantation of this prosthesis require further investigation to assess the risk they may pose to bone failure.     

In vitro testing of a novel limb salvage prosthesis for the distal femur

Objective. The aim of this paper was to define strain pattern in the host bone following distal femoral resection and implantation of a massive prosthesis. Two methods of coupling the prosthesis to the bone were compared: the Compliant Pre-Stress device, and a standard cemented tumour prosthesis.

Design. The composite femur model was selected to minimize variables. Four femurs were tested before and after implantation. Both coaxial and cantilever loading were applied.

Background. Cemented distal femoral replacement following resection of malignant tumours has a high failure rate at 5 years and is associated with extensive bone resorption thought to be secondary to stress shielding.

Methods. Strain was measured in the medial and lateral sides at four levels with physiologic loads applied, in the intact, Compliant Pre-Stress, and cemented femurs. Repeated measurements were taken. Strains in the implanted femur were calculated as percentage of the intact, and statistically analyzed.

Results. The most reproducible results were noted in cantilever bending (variability <5%). The Compliant Pre-Stress device demonstrated a more physiologic strain pattern than the cemented stem. The most significant difference between the two implants was in the area adjacent to the interface.

Conclusion. The Compliant Pre-Stress device shows less stress shielding than a standard cemented implant. The protocol described and the use of composite femurs demonstrated reproducible results.     

聚醚醚酮髋股骨头假体置换术后股骨近段载荷传递的力学性能

背景:人工关节无菌性松动的力学因素是传统金属假体的弹性模量远远超过骨的弹性模量,组合后产生应力遮挡,引起骨吸收、骨萎缩.目的:体外测试自制的碳纤维增强聚醚醚酮(CF/PEEK)假体置换后股骨的应变,并与国产AML假体进行比较,探讨复合材料在全髋股骨头假体中的应用前景.设计、时间及地点:对比分析实验,于2002-09/2004-03在苏州大学第一附属医院骨科实验室和上海大学生物力学工程研究所完成.材料:CF/PEEK假体为自行设计,内层采用长CF/PEEK复合材料,模量为100 GPa;外层采用短CF/PEEK复合材料,模量为 20 GPa;在应力集中区,适当加强铺层密度;几何形态与相关尺寸同国产仿AML型钴合金假体.AML假体为北京华杰豪公司生产.标本为5对新鲜成人尸体股骨10具.方法:5 对人体新鲜尸体股骨平均分成左右两组,一组行钴铬钼合金股骨头假体置换术,另一组行CF/PEEK假体置换术.在假体和近端股骨表面粘贴应变片,模拟单肢站立施加载荷.主要观察指标:①正常股骨表面和两种假体置换后的股骨表面的应变分布.②两种假体置换后股骨-假体界面剪切应变分布. 结果:股骨应变在假体植入后,从近端到远端逐渐增加,变化形式与完整股骨的应变形式相似,并且在假体远端最大.两种假体植入后,股骨内外侧表面的应变皆减少;但CF/PEEK假体组产生的应变形式和大小比钴铬钼合金假体组更接近正常股骨. 结论:CF/PEEK复合材料假体的力学性能与骨组织相近,加载时两者的应变量一致,因此能提供术后即刻稳定性和良好的近端载荷传递.