形状记忆锯齿臂环抱内固定器的稳定性研究

本文采用５２根犬股骨作中段截骨，分别以新设计的形状记忆锯齿臂环抱内固定器、接骨板和髓内钉进行固定。然后对三种固定方法对固定骨段的应力遮挡率、不同加载方向的弯曲强度和扭转强度进行测试。试验证实环抱器有良好的抱持力，固定后其抗弯强度与接骨板无明显差异，而其应力遮挡率却明显低于接骨板（ｐ＜０．０１），同时抗扭作用又明显高于髓内钉（ｐ＜０．０１）。上述结果提示，环抱器可在对骨折提供可靠固定的同时，避免接骨板所致的应力遮挡性骨质疏松，具备髓内钉所没有的良好抗扭能力，并在安放时不损伤髓内血供和骨膜，具有良好的应用前景。     

钢板固定对犬胫骨生物力学性能影响的实验研究

钢板内固定后所致的局部骨质疏松是钢板取出后再骨折的主要原因。方法:本实验采用316l医用不锈钢制成的三种不同力学性能的4孔钢板固定在犬完整胫骨中段,以单纯普通皮质骨螺丝钉固定作对照组。用静态应变仪测量不同条件下的胫骨应变值,观察活体骨组织不同时期骨CT片灰度变化及测试扭力。结果:上述不同的方法固定均可使局部产生骨质疏松,其程度与钢板的刚度成正比关系,但随时间延长这种骨质疏松可逐渐减轻。生物力学测试表明随着骨质疏松的减轻,骨质的力学性能亦逐渐恢复,但术后5个月时仍未恢复到固定初期水平。     

单皮质钢板内固定长骨折游离大骨片的实验研究

目的：探讨薄形钢板单皮质固定长骨粉碎性骨折所形成的游离大骨片,为临床应用提供理论依据.方法：采用48根长短、粗细相近的新鲜成人尸体胫骨标本,均制作成具有游离大骨片的中段长斜形粉碎性骨折模型,并用重建钢板于胫骨张力侧固定胫骨主干,再随机均分为A、B、C 3组,游离大骨片分别用双股细钢丝环形捆扎固定（A组）、1枚拉力螺钉固定（B组）、薄形钢板单皮质固定（C组）.将标本固定于MTS试验机上,测试并比较3组标本的轴向抗压刚度、抗弯刚度和抗扭刚度.结果：C组的抗弯刚度、抗扭刚度和轴向抗压刚度均强于A组和B组（P＜0.05）.结论：薄形钢板单皮质固定长骨粉碎性骨折所形成的游离大骨片,效果可靠.     

应力松弛接骨板对骨应力遮挡率影响的实验研究

将螺孔部衬有不同数量、不同厚度聚乙烯垫圈的３１６Ｌ不锈钢接骨板置于２０根聚甲基丙烯酸甲酯模拟骨中段。分别在固定后不同时期测定不同载荷下接骨板内二螺孔间的外表面及接骨板对侧模拟骨中段的应变值，从而计算出应力遮挡率。结果发现，有垫与无垫接骨板组在术后１０周内的应力遮挡率无统计学差异，１０周以后两组间出现显著性差异，无垫组保持不变，有垫组的应力遮挡率逐渐下降。在垫圈厚度相同时，衬垫数量越多（本实验最多采用４孔４垫），后期应力遮挡率下降越明显。表明应力遮挡率的变化与垫圈数量关系密切。     

应力松弛接骨板对骨应力遮挡率影响的实验研究

将螺孔部衬有不同数量、不同厚度聚乙烯垫圈的３１６Ｌ不锈钢接骨板置于２０根聚甲基丙烯酸甲酯模拟骨中段。分别在固定后不同时期测定不同载荷下接骨板内二螺孔间的外表面及接骨板对侧模拟骨中段的应变值，从而计算出应力遮挡率。结果发现，有垫与无垫接骨板组在术后１０周内的应力遮挡率无统计学差异，１０周以后两组间出现显著性差异，无垫组保持不变，有垫组的应力遮挡率逐渐下降。在垫圈厚度相同时，衬垫数量越多（本实验最多采用４孔４垫），后期应力遮挡率下降越明显。表明应力遮挡率的变化与垫圈数量关系密切。     

重建钢板与钛制弹性钉两种内固定方式治疗锁骨中段骨折的有限元分析

目的应用有限元方法分析锁骨中段骨折分别采用钛制弹性钉(titanium elastic nail,TEN)髓内固定和重建钢板固定后的应力分布、最大应力。方法利用Mimics软件对锁骨的CT数据进行三维重建,建立无损锁骨、锁骨中段骨折,分别采用TEN髓内固定和重建钢板固定的三维有限元模型。运用Abaqus 6.9软件对建立的模型进行有限元分析,模拟锁骨远端250 N轴向载荷及250 N垂直载荷下,计算三者锁骨远端位移、最大应力及应力分布等情况。结果轴向载荷下锁骨远端轴向位移为TEN固定模型(0.23 mm)>无损锁骨模型(0.14 mm)>重建钢板固定模型(0.11 mm),垂直载荷下锁骨远端垂直位移为TEN固定模型(5.12 mm)>无损锁骨模型(3.71 mm)>重建钢板固定模型(2.25 mm)。轴向载荷锁骨最大应力为TEN固定模型(33.1 MPa)>重建钢板固定模型(18.7 MPa)>无损锁骨模型(15.5 MPa);垂直载荷锁骨最大应力为TEN固定模型(146.3 MPa)>无损锁骨模型(64.1 MPa)>重建钢板固定模型(56.1 MPa)。两种载荷下TEN固定模型锁骨的应力分布均与无损锁骨模型较接近;垂直载荷下重建钢板固定模型锁骨的应力分布与无损锁骨模型明显不同。内植物最大应力,轴向载荷为TEN固定模型(191.5 MPa)>重建钢板固定模型(52.3 MPa),垂直载荷为TEN固定模型(1 248.0 MPa)>重建钢板固定模型(421.7 MPa)。结论 TEN髓内固定治疗简单的锁骨中段骨折,锁骨应力分布更接近于正常锁骨,但其骨折端锁骨及TEN应力均较大。重建钢板固定锁骨中段骨折,其固定效果更稳定,但应力遮挡效应更明显。因此,对于简单移位的锁骨中段骨折,建议采用TEN髓内固定治疗,但术后早期患肩应避免过度锻炼及持重。     

A new approach to the design of internal fixation plates

Mathematical analysis by finite element modeling methods was used in conjunction with laboratory bench experiments in selecting appropriate stiffness parameters for internal fixation plate designs. Bench experiments performed included tests of an idealized plated magnesium tube and of a plated canine femur. Finite element modeling of the plate-tube and plate-bone structures was also performed, and the computed results were compared with those obtained experimentally. Three types of internal fixation plates--one "rigid" control plate and two less rigid experimental plates--were examined using both the finite element and experimental models. These plates were further examined by finite element modeling of a plated human femur during single stance loading. In all cases, the "rigid" control plate was found to shield the underlying bone from stress, while both experimental plates were found to have significantly less bone stress shielding. Our findings suggest that an improved plate design should have a low axial stiffness but moderate bending and torsional stiffnesses to facilitate fracture healing and bone remodeling without causing osteopenia.     

纵向生理加压外固定器的生物力学分析

背景：目前骨外固定器大多为刚性结构,对骨折端存在过多的应力遮挡,影响骨折愈合速度及骨痂质量,甚至骨折发生不愈合。 目的：观察纵向生理加压外固定器固定胫骨中段横断骨折后与人体正常胫骨生物力学强度的差异。 方法：选取12根新鲜胫骨标本随机分为试验组和对照组,试验组分别用线锯造成胫骨中段横断骨折,纵向生理加压外固定器固定;对照组即正常胫骨。分别进行轴向载荷、弯曲载荷、扭转载荷作用下的力学实验,记录每一级加载后胫骨的位移及扭转角度,计算出轴向压缩刚度、弯曲刚度及扭转刚度。 结果与结论：在生理范围内加载下,试验左右应变略大于对照组,但其固定后整体刚度与对照组无显著性差异(P > 0.05);试验组的弯曲应变大于对照组,但其整体刚度与对照组无显著性差异(P > 0.05);两组整体扭转刚度无明显差异(P > 0.05);试验组极限弯曲载荷明显大于对照组(P < 0.05)。提示纵向生理加压外固定器能够达到足够的生物力学强度,有良好的稳定性,对骨折能起到生物学固定。     

前外侧或后内侧辅助钢板结合髓内钉固定胫骨近端 1 / 3 骨折的生物力学研究

目的 研究髓内钉结合辅助钢板固定胫骨近端1/3骨折的稳定性,比较并观察胫骨近端1/3骨折后内侧辅助钢板与前外侧辅助钢板结合髓内钉固定的生物力学特点。方法 选取Sawbones第4代人工胫骨模型。根据辅助钢板位置分为后内侧钢板组和前外侧钢板组,每组4例,髓内钉远近端均2枚锁定钉固定,钢板远近端各3枚皮钉双层皮质固定。模拟AO分型41-A2型骨折,水平截骨平面位于胫骨髓内钉近端锁定钉远端0.5 cm即近端关节面以远5～6 cm位置。截骨完成后,通过生物力学试验机分别进行轴向压缩、三点弯曲、循环加载及极限应力测试,比较各组轴向刚度、三点弯曲刚度等结果。结果 轴向压缩实验表明,后内侧钢板组平均轴向刚度低于前外侧钢板组,两组间差异无统计学意义。三点弯曲实验表明,后内侧钢板组无论是对抗内翻应力(钢板位于骨折压力侧,t=3.679,P<0.05)还是外翻应力(钢板位于骨折张力侧,t=8.975,P<0.05),其弯曲刚度均优于前外侧钢板组。结论 辅助钢板结合髓内钉固定胫骨近端1/3骨折可以提高近端骨折块固定的稳定性,并允许患者更早负重。钢板置于后内侧或者前外侧均能够提供足够的轴向强度,后...     

Assessment of Carbon Fibre Composite Fracture Fixation Plate Using Finite Element Analysis

In the internal fixation of fractured bone by means of bone-plates fastened to the bone on its tensile surface, an on-going concern has been the excessive stress shielding of the bone by the excessively-stiff stainless-steel plate. The compressive stress shielding at the fracture-interface immediately after fracture-fixation delays callus formation and bone healing. Likewise, the tensile stress shielding in the layer of bone underneath the plate can cause osteoporosis and decrease in tensile strength of this layer.In this study a novel forearm internal fracture fixation plate made from short carbon fibre reinforced plastic (CFRP) was used in an attempt to address the problem. Accordingly, it has been possible to analyse the stress distribution in the composite plates using finite-element modelling.A three-dimensional, quarter-symmetric finite element model was generated for the plate system. The stress state in the underlying bone was examined for several loading conditions. Based on the analytical results the composite plate system is likely to reduce stress-shielding effects at the fracture site when subjected to bending and torsional loads. The design of the plate was further optimised by reducing the width around the innermost holes.     

In-vitro biomechanical evaluation of stress shielding and initial stability of a low-modulus hip stem made of β type Ti-33.6Nb-4Sn alloy

Stress shielding-related proximal femoral bone loss after total hip arthroplasty occurs because of the different stiffness of metallic alloy stems and host bone. To overcome this, we fabricated a low-modulus cementless hip stem from β-type Ti-33.6Nb-4Sn alloy (TNS). Then we evaluated its stiffness, stress shielding, and initial stability compared with a similar Ti-6Al-4V alloy stem. Stiffness was determined by axial compression and cantilever-bending tests. Thirteen triaxial strain gages measured cortical strain. Stress shielding was defined as the percentage of intact strain after stem insertion. To evaluate initial stability, displacement transducers measured axial relative displacement and rotation. Intact and implanted femurs underwent single-leg-stance loading. Axial stiffness was 56% lower in the TNS stem than in the Ti-6Al-4V stem, and bending stiffness of the TNS stem decreased gradually from the proximal region to the distal region, being ≤53% that of the Ti-6Al-4V stem, indicating gradation of Young's modulus. The TNS stem decreased stress shielding in the proximal calcar region (A1: 83%, B1: 85% relative to intact cortical strain) without affecting the proximal lateral region (B3: 53%). The initial stabilities of the stems were comparable. These findings indicate that the TNS stem with gradation of Young's modulus minimizes proximal femoral bone loss and biological fixation, improving long-term stability.     

新型点接触锁定加压接骨板的生物力学研究

目的对一种集合点状接触、锁定及加压于一体的新型接骨板(PC-LCP),进行弯曲力学特性、生物力学稳定性测试评估。方法对三种医用不锈钢接骨板,点接触锁定加压接骨板(PC-LCP)、有限接触动力加压接骨板(LC- DCP)、动力加压接骨板(DCP)各3副进行四点弯曲试验;20对新鲜山羊胫骨制成横断骨折,应用三种接骨板固定,进行四点弯曲、扭转及垂直压缩试验。结果PC-LCP弯曲刚度弱于DCP、LC-DCP,三者有显著差异(P<0.05),但三种接骨板固定骨折后的生物力学特性没有显著差异。结论强度稍低的新型接骨板PC-LCP固定骨折后与其它两种接骨板有同样的生物力学强度及较好的力学稳定性。     

限制接触型滑槽螺栓加压双钢板的设计及力学性能研究

目的 设计一种用于固定长骨干粉碎性骨折的新型双钢板，并测试其力学性能。方法 自行设计制造限制接触型滑槽螺栓加压双钢板。并利用电测方法测试其强度及应力遮挡效应，与相同材料和工艺制造的单钢板和普通螺栓双钢板比较，检验其设计的合理性。结果 限制接触型滑槽昆栓加压双钢板的轴向强度介于单钢板和传统双钢板之间，与两者均有显著差异（P＜0．01），抗弯强度接近传统双钢板，与单钢板有显著差异（P＜0．01），应力遮挡率显著低于普通螺栓双钢板（P＜0．01），与单钢板的应力遮挡率没有显著性差异。结论 限制接触型滑槽螺栓加压双钢板的强度高且应力遮挡效应较低，力学设计合理，使早期功能锻炼和加快骨折愈合成为可能。走出了应力遮挡效应随内固定物截面积增大而增大的误区，为坚强内固定的前提下降低应力遮挡效应提供了一种新的方法     

骨组织局部单位体积内生物电能低下与应力遮挡综合症

目的探讨"组织细胞生物电能稳态失衡"概念与骨折内固定后出现应力遮挡综合症发生发展的关系。方法引入一个新的概念,即"组织细胞内环境生物电能稳态"(或"骨组织内单位体积生物电能含量稳态")。这个概念包括骨组织细胞外基质中蛋白聚糖分子生物电能的储存量、细胞膜膜电位以及细胞内负离子含量要维持在一个正常范围。通过这一新理论阐述应力遮挡形成原因的关系。结果骨折内固定(钢板或带锁髓内钉)出现不同程度的应力遮挡现象,应力遮挡区域骨组织出现单位体积内生物电能含量不足,并且处于长期、持续性生物电能含量减低现象,导致内固定应力遮挡范围内骨组织生物电能稳态失衡,骨组织处于长期、持续性极其轻度的酸化环境中,最终出现骨组织局部骨质疏松。结论骨组织单位体积内生物电能含量持续性减低是导致骨质疏松、骨愈合缓慢(应力遮挡)的原因。     

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.     

可变刚度可降解-DL-聚乳酸泡沫衬垫材料与钛合金组成接骨板系统治疗胫骨骨折

背景：理想的骨折固定系统,在骨折早期应能达到坚强固定,后期要能防止应力遮挡作用诱发的固定骨段的骨质疏松。可降解骨科内固定材料无疑为此种骨折固定系统提供了理论可能。 目的：旨在评估自制可变刚度接骨板系统(由可降解聚-DL-乳酸泡沫衬垫材料和钛合金接骨板组成)对兔胫骨干中段骨折的固定效果和对骨折愈合的影响。 方法：新西兰大白兔64只采用随机数字表法分为实验组和对照组,线锯造成兔右侧胫骨中段骨折模型。用相对分子质量为 200 000的自制超高相对分子质量聚乳酸材料膜垫(厚1 mm)和4孔钛合金Tc4接骨板制作成可变刚度接骨板系统固定实验组兔胫骨中段骨折,以单纯Tc4钛合金接骨板固定对照组。于第2,4,8,12周处死动物,从大体观察、X射线平片、组织学和骨生物力学等方面观察和评定骨折愈合情况。 结果与结论：X射线及大体标本示术后两组对位效果佳,无移位。组织学观察可见术后同期实验组标本较对照组标本骨痂内骨小梁排列紧密、髓腔开通完全、新生骨组织改塑重建完整。生物力学结果显示8周时两组愈合骨最大抗弯曲强度差异无显著性意义。12周时实验组愈合骨抗弯曲刚度优于对照组。提示自制可变刚度接骨板系统用于兔胫骨骨折固定效果可靠,有利于骨折段骨痂改塑重建,利于骨折愈合,用于骨折内固定治疗效果优于单纯钢板,为其进一步临床应用研究提供了实验依据。     

应力松驰接骨板对固定段骨结构及力学性能影响的实验 …

目的：了解应力松驰接骨板固定对固定段骨形态结构及力学性能的影响。方法：分别将应力松驰接骨板（实验组）和坚硬接骨板（对照组）固定于兔胫骨干中段,采用ＣＴ扫描及ＣＴ值测定和力学测试,观察固定段骨结构及力学性能的变化。结果：固定后８～１２周,两组板下皮质骨厚度均逐渐变薄,伴ＣＴ值和固定骨段力学强度下降,以对照组为明显。２４～２６周,实验组板上皮质骨厚度、ＣＴ值和固定骨段力学强度逐渐恢复,接近正常;而对照     

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。     

Buttressing angle of the double-plating fixation of a distal radius fracture: a finite element study

Treatment of a distal radius fracture should consider principles including stable fixation and early motion. The aim of this study was to investigate the biomechanical interactions of plate-fixation angles in the internal double-plating method coupled with various load conditions using non-linear finite element analysis (FEA). A 3D finite element distal radius fracture model with three separation angles (50, 70, and 90°) between the buttressed L- and straight plates was generated based on computed tomography data. After model verification and validation, frictional (contact) elements were used to simulate the interface condition between the fixation plates and the bony surface. The stress/strain distributions and displacements at the radius end were observed under axial, bending, and torsion load conditions. The simulated results indicated that the bending and torsion increased the stress values more than the axial load. The radius and straight plate stress values decreased significantly with increasing fixation angles for all load conditions. However, the L-plate stress values increased slightly under the bending buckling effect. The displacements at the radius end and strains at the fracture healing interface decreased with increasing fixation angles for axial and torsion conditions but displayed a slight difference for the bending condition. The findings using FEA provide quantitative evidence to identify that much larger plate fixation angles could provide better mechanical strength to establish favorable stress-transmission and prevent distal fragment dislocation.     

重建钢板前置和上置固定锁骨中段斜形骨折的有限元分析

目的　通过三维有限元法对重建钢板前置和上置固定锁骨中段斜行骨折的生物力学稳定性进行比较,为临床应用提供理论参考。 方法　建立锁骨中段斜行骨折分别予以重建钢板前置位固定和上置位固定的三维有限元模型,相同的加载和约束条件下模拟轴向压缩、顺时针扭转、逆时针扭转和三点弯曲4种工况,评价不同内固定的最大等效应力、骨折块的最大综合位移和骨折断端的最大等效应力。 结果 ⑴压缩工况下前置位和上置位各评价指标无差异;⑵在顺时针扭转和弯曲时,前置位内固定装置的最大应力明显大于上置位,但骨折块的最大综合位移和骨折断端的最大应力差别不大;⑶在逆时针扭转工况下,上置位固定的各个指标数值虽大于前置位,但基本接近。 结论　对于重建钢板固定锁骨中段斜行骨折,前置位固定比上置位更容易出现应力集中,提示上置位固定的生物力学稳定性优于前置位。