β钛合金研究进展及其在骨科中的应用前景

前言 医用钛合金的发展经历了三个阶段:纯钛和六铝四钒钛合金;以Ti-6A1-7Nb和Ti-5A1-2.5Fe为代表的a+β型合金;具有更好生物相容性和更低弹性模量的β钛合金.本文从材料学角度和生物相容性角度重点介绍了新型β钛合金的国内外研究进展.另外,本文还探讨了新型低弹性模量β钛合金在骨科方面的应用前景.     

孔隙率对多孔镍钛合金力学性能及离子析出量的影响

目的筛选生物力学相容性优良的颌骨内植入用多孔镍钛合金,比较二氧化钛(TiO2)与羟基磷灰石(HA)涂层后的镍离子析出量。方法采用粉末冶金法制备多孔镍钛合金,用金相显微镜观察孔隙形貌,进行压缩与抗折破坏实验,记录其弹性模量与断裂强度值;采用溶胶-凝胶法分别涂覆TiO2与HA涂层,测定1、3、7、15 d镍离子析出量。结果孔隙由相互连通的50～200μm大孔和～50μm微孔组成,孔隙率为(23.5±5.24)%～(38.8±1.82)%;弹性模量为(9.55±0.19)～(4.28±0.32)GPa,断裂强度值为(133±6.75)～(80.5±5.58)MPa。表面涂层组与未涂层组比较,离子析出量显著降低;氧化钛与羟基磷灰石涂层组间差异无统计学意义。结论随造孔剂增加,孔隙率增大,多孔镍钛合金的力学性能呈下降趋势;涂层能有效抑制多孔镍钛材料中镍离子析出。     

纳米压痕技术在骨组织微纳观结构研究中的应用

目的:纳米压痕技术测得骨的微观弹性模量及硬度反映骨的微观力学性能,在骨组织微结构研究中的应用已经日益广泛,本文的目的在于对纳米压痕技术在骨微结构研究中的应用进展过程进行回顾性的综述。方法:阅读相关文献分别对纳米压痕技术原理组成、使用及计算方法及其在骨力学、微结构、骨愈合、骨软骨组织研究中的应用等几个方面进行归纳总结性阐述,从而得出该技术在整个骨组织研究中的应用趋势及发展现状。结果:在骨研究中骨的整体宏观力学性能变化情况与纳米压痕技术所测得的微观力学性能可能并不一致。骨微结构研究中纳米压痕硬度能有效地反映骨材料的各向异性程度。纳米压痕技术可以将骨愈合潜在的生物学原理与机械性能逐渐恢复过程相联系起来。纳米压痕与原子力显微镜等技术相结合可以提高试验的准确度。结论:纳米压痕技术是作为测量骨表面和骨组织的纳米量级形貌特征和100 nm~600 nm下的凹痕压痕模量与硬度等力学性质的重要手段。纳米压痕技术在评价骨组织材料质量方面有着良好的应用前景,日渐成熟且仍有很大的发展空间。     

New β Ti alloy mini-prosthesis with low elastic modulus resurfacing articular surface defect in dogs

Objective To assess the effect of a new β Ti alloy mini-prosthesis with low elastic modulus on resurfacing the full-thickness Surface defect of the knee joint in dogs.Methods A full-thickness osteochondral defect of 7 mm in diameter was created at the medial femoral condyle of both hind limbs in 8 healthy adult dogs.The titanium alloy mini-prostheses with high-modulus of elasticity were implanted on the right side(control group)and those with low-modulus of elasticity on the left side(experiment group)to repair the cartilage defects.After 3 months,all the 8 dogs were sacrificed to harvest the specimens.Radiographic,histologic and micro-CT examinations were conducted to observe stability of the mini-prostheses and growth of the bone and cartilage surrounding the implants. Results Radiographic evaluation revealed no indications of device disassembly or subsidence.Bone trabeculae surrounding anchoring screws in the experiment group was visibly more and denser compared with the control group.Micro-CT data revealed that the bone volume fraction,trabecular thickness,trabecular number and tissue mineral density were 0.389%±0.025%,0.049±0.002 μm,8.9±0.4 mm-1 and 652.7 ±12.6 mg/mm3 respectively in the experiment group,compare with 0.253%±0.024%,0.038±0.002 μm,5.9±0.4 mm-1 and 595.2±7.6 mg/mm3 in the control group,with statistically significant differences between the 2 groups(P<0.05).Cartilage around the cap grew well and the surface remained smooth.Periphery of the resurfacing implant was covered by an extension of the superficial cartilage emanating from the defect margins. Conclusions The new β Ti alloy mini-prosthesis with low elastic modulus is favorable toward resurfacing the articular surface defect.The low-modulus of elasticity can improve new bone formation on the implant-bone interface.     

血管内超声弹性成像中成像参数的比较研究

目的验证血管内超声弹性成像用于检测血管斑块的有效性。方法建立血管斑块的平面应变模型并生成超声仿真数据。通过一维数值优化算法获得血管径向位移分布和应变分布。通过有限元分析和迭代的方法得到血管的弹性模量分布。结果位移、应变、弹性模量3个分布图均能够检测到血管斑块,弹性模量能够提供斑块的形状大小信息,位移和应变分布图上斑块的轮廓尚不清晰。结论相对于位移和应变,弹性模量对于斑块的检测有着明显的优势,但受应变估计准确度的影响。     

不同运动步态下锁定加压钢板固定胫骨干骨折的有限元分析

背景：目前有限元分析广泛应用于人体骨折内固定模型的力学分析,但大多研究局限于静态下,动态下的骨折模型有限元分析尚未见报道。 目的：通过三维有限元分析来探讨锁定加压钢板固定胫骨干不同类型骨折在不同运动步态下的应力分布情况。 方法：利用CT扫描获得正常成人胫腓骨及足部的薄层扫描图像;运用相关软件建立其三维模型,在此模型上模拟出胫骨中段横行、斜行、粉碎性、螺旋形4种类型骨折,并与锁定钢板进行装配生成实验模型,各组模型加载相同的轴向压缩载荷600 N。通过有限元分析软件Ansys 12.0分别测定各组模型在落地相、中立相、离地相三种步态下的应力分布情况。 结果与结论：在步态下,胫骨在骨折各组中的应力分布由小到大均为：落地相<中立相<离地相。锁定钢板在胫骨中段横行、斜行、粉碎性骨折中的应力分布由小到大均为：中立相<落地相<离地相;在胫骨中段螺旋形骨折中应力分布由小到大为：离地相<中立相<落地相;提示在运动步态中,钢板和胫骨均在离地相受力最大。钢板的应力集中在中间或边缘;而胫骨的应力分布在骨折线以上靠近近端,骨折线以下靠近骨折线。就胫骨整体而言,呈现两端集中,中间分散的状态。     

构建可控释血管内皮生长因子多壁碳纳米管的复合支架

背景：单纯植入猪小肠黏膜下层修复腹壁缺损存在早期血管化不足,导致修复失败。 目的：构建可控释血管内皮生长因子的多壁碳纳米管-猪小肠黏膜下层复合支架,评价其体外控释血管内皮生长因子性能、力学性能及细胞毒性。 方法：通过浸染将装载血管内皮生长因子的多壁碳纳米管复合到猪小肠黏膜下层上,构建可控释血管内皮生长因子的复合支架,并根据多壁碳纳米管与猪小肠黏膜下层的不同质量比(0,1%,3%,5%,10%)构建5种多壁碳纳米管-猪小肠黏膜下层。 结果与结论：①复合支架的血管内皮生长因子控释性能：随时间的延长,各组的累积浓度增高,且随着多壁碳纳米管质量的增加,释放浓度也逐渐增加。②复合支架的力学性能：1%,3%,5%,10%多壁碳纳米管-猪小肠黏膜下层最大载荷及弹性模量均高于猪小肠黏膜下层(P < 0.05),且随着多壁碳纳米管质量的增加,最大载荷逐渐增加。③复合支架的成纤维细胞毒性：多壁碳纳米管在复合支架中质量分数≤5%时对细胞的生长无影响。表明构建的多壁碳纳米管复合支架具备良好的血管内皮生长因子控释性能、力学性能及促进内皮细胞增殖的能力。     

纳米羟基磷灰石/聚醚醚酮复合种植体受力的三维有限元分析

目的:评价纳米羟基磷灰石/聚醚醚酮(Nano-hydroxyapatite/Polyetheretherketone ,n-HA/PEEK)仿生种植材料受力时种植体及其周围骨组织的应力特征,为该种植材料的临床运用提供生物力学依据。方法:根据CT扫描数据及种植体产品数据建立包括牙槽骨、种植体的三维有限元模型,比较在150N垂直加载条件下n-HA/PEEK和钛种植体周围骨皮质及骨松质的应力分布。结果:两种材料应力分布规律:紧邻种植体颈部的骨皮质应力最大远离处逐渐减小,皮质骨内两种材料的表面最大应力有显著性差异(P<0.05)。负重时钛金属种植体其表面应力波动变化范围增大,容易形成应力集中。同骨组织具有相似弹性模量的n-HA/PEEK材料表面应力分布更均匀。结论:n-HA/PEEK材料更有利于将种植体所受载荷以应力的形式传递到周围骨组织中去,有利于保持骨结合面的长期稳定。     

低弹性模量新型组合式锁定加压钢板固定股骨粉碎性骨折的三维有限元分析

目的 通过有限元分析的方法观察低弹性模量Ti2448的新型组合式锁定加压钢板(NALCP)固定股骨粉碎性骨折的应力分布情况。方法 采用64排螺旋CT对1名健康成年男性股骨进行层厚为5 mm(拆薄图像层厚0.625 mm)扫描,获得股骨CT数据,通过Mimics 10.0、Geomagic studio 12.0等逆向工程软件获得股骨有限元模型,模拟股骨中段粉碎性骨折,分别采用Ti-6Al-4V(普通弹性模量,为110 GPa)及Ti2448(低弹性模量,为30 GPa)两种弹性模量方案钢板模拟手术固定,加以缓慢行走单腿股骨载荷及扭转载荷,分析两种弹性模量钢板及股骨的应力分布情况。结果 两种载荷情况下,两种固定方案钢板应力分布变化趋势均匀,骨折断端周围为应力集中区域,最大应力集中点位置均位于滑槽钢板与主钢板锁定孔,两种方案主钢板应力变化不大。与Ti-6Al-4V钢板方案相比,Ti2448滑槽钢板最大应力在缓慢行走载荷和扭转载荷下分别减少了20.6%和15.2%,而骨折块轴向最大应力则分别增加了95.8%和95.7%。 结论 低弹性模量NALCP既能够为股骨干32-C2.1型骨折提供坚强的力学稳定性,又能增加骨折断端力学刺激,并能有效固定骨碎块。     

生物反应器中的力学刺激促进组织工程软骨再生

BACKGROUND: Cartilage tissue engineering has been widely used to achieve cartilage regeneration in vitro and repair cartilage defects. Tissue-engineered cartilage mainly consists of chondrocytes, cartilage scaffold and in vitro environment. OBJECTIVE: To mimic the environment of articular cartilage development in vivo, in order to increase the bionic features of tissue-engineered cartilage scaffold and effectiveness of cartilage repair. METHODS: Knee joint chondrocytes were isolated from New Zealand white rabbits, 2 months old, and expanded in vitro. The chondrocytes at passage 2 were seeded onto a scaffold of articular cartilage extracellular matrix in the concentration of 1×106/L to prepare cell-scaffold composites. Cell-scaffold composites were cultivated in an Instron bioreactor with mechanical compression (1 Hz, 3 hours per day, 10% compression) as experimental group for 7, 14, 24, 28 days or cultured statically for 1 day as control group. RESULTS AND CONCLUSION: Morphological observations demonstrated that the thickness, elastic modulus and maximum load of the composite in the experimental group were significantly higher than those in the control group, which were positively related to time (P < 0.05). Histological staining showed the proliferation of chondrocytes, formation of cartilage lacuna and synthesis of proteoglycan in the experimental group through hematoxylin-eosin staining and safranin-O staining, which were increased gradually with mechanical stimulation time. These results were consistent with the findings of proteoglycan kit. Real-time quantitative PCR revealed that mRNA expressions of collagen type I and collagen type II were significantly higher in the experimental group than the control group (P < 0.05). The experimental group showed the highest mRNA expression of collagen type I and collagen type II at 21 and 28 days of mechanical stimulation, respectively (P < 0.05). With the mechanical stimulation of bioreactor, the cell-scaffold composite can produce more extracellular matrix, such as collagen and proteoglycan, strengthen the mechanical properties to be more coincident with the in vivo environment of cartilage development, and increase the bionic features. With the progress of tissue engineering, the clinical bioregeneration of damaged cartilage will be achieved.   中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程