Influence of surgeon's tying technique on knot security.

The purpose of this study was to determine the influence of the surgeon's tying technique on knot security using 0 and 2-0 monofilament and multifilament nylon sutures. Using an Instron Tensile Tester and a portable tensiometer, knot security was achieved with these sutures using four-throw square knots (1 = 1 = 1 = 1). After didactic and psychomotor skill training, medical students were taught to construct the four-throw square knot using either a two-hand tie or an instrument tie. Using the portable tensiometer, their knot tying techniques were judged to be superior to those used by surgeons. The surgeon's faulty technique can easily be corrected by didactic information and psychomotor skill training.     

玻璃化法和低温冷冻法保存兔股动脉的形态结构及力学性能比较

背景:一种有效的保存方法必须能够保存组织的完整结构.目的:比较玻璃化法和低温冷冻法保存对动脉形态结构和力学性能的影响.设计、时间及地点:随机对照动物实验,于2001-0912004-08在解放军总医院骨科研究所完成.材料:新两兰兔18只,按随机数字法分为3组:玻璃化法保存组,低温冷冻法保存组,新鲜血管组,每组6只.方法:切取股动脉标本,置于平衡液中备用.玻璃化法保存组血管在4℃条件下经25%,50%和100%梯度玻璃化溶液浸泡后,直接投入液氮中.低温冷冻法保存组血管由常温状态下,经过0,-20,-70℃梯度降温,平衡60 min,直接投入液氮中.样本在液氮中保存14d以上.主要观察指标:进行大体形态和显微形态观察,以了解保存后动脉形态结构的改变;观察动脉的滞后环和应力松弛,测定其断裂强度.结果:两种方法均较好地保存了动脉的结构,玻璃化法保存组完整率为91.67%,低温冷冻法保存组完整率为54.17%(P<0.01):3组动脉均具有滞后环和应力松弛现象,玻璃化法保存组的断裂张力为(2.286 3±0.417 6)N,低温冷冻法保存组的断裂张力为(1.951 0±0.413 0)N,新鲜血管组的断裂张力为(2.543 5±0.5454)N,3组之间的差别无显著性意义(P>0.05).结论:玻璃化法和低温冷冻法对动脉的形态结构和力学性能无显著影响;玻璃化法保存造成的组织断裂较少,适合大段血管的保存.     

青年与老年尸体肋骨冲击力学特性的比较

背景:骨质疏松、骨重建、骨再造、胸椎骨折固定器选择等都需要了解青年和老年尸体肋骨的冲击力学特性.以往的研究多以单独青年尸体或单独老年尸体肋骨为观察对象,而有关青年和老年尸体肋骨冲击力学特性的研究报道极少.目的:对正常国人青年和老年新鲜尸体肋骨进行冲击实验,分析肋骨的冲击力学性质,确定老年尸体肋骨和青年尸体肋骨是否具有不同的冲击力学性质.方法:实验标本取自4具正常国人男性新鲜尸体,年龄分别为20,25,70,75岁,由吉林大学医学部解剖教研室提供.人死亡后1 h内解剖取出死者肋骨T3～12标本,将标本沿纵向切成长55 mm的试样,青年组和老年组各20个.以能量释放的方法对2组试样进行冲击实验.实验结束后,试验机测量度盘自动显示试样的冲击功,根据材料力学公式计算出每个试样的冲击韧性,观察各试样的宏观断口形貌.结果与结论:青年组肋骨冲击功、冲击韧性均显著大于老年组(P<0.05).肋骨冲击实验断口多数为粉碎性断口,少数为横断口或斜断口.肉眼观察发现青年组肋骨骨小梁排列细密,老年组肋骨骨小梁排列稀疏,孔隙较大,呈现出老年骨质疏松的表现形式.提示青年组肋骨和老年组肋骨具有不同的冲击力学特性,老年组试样由于骨质疏松导致冲击力学特性发生改变.     

Relationship between CT intensity, micro-architecture and mechanical properties of porcine vertebral cancellous bone

BACKGROUND: In vivo assessment of bone density is insufficient for the evaluation of osteoporosis in patients. A more complete diagnostic tool for the determination of bone quality is needed. Micro-computed tomography imaging allows a non-destructive method for evaluating cancellous bone micro-architecture. However, lengthened exposure to ionizing radiation prevents patients to be imaged by such a system. The aim for this study was to elucidate the relationships between image intensity (of Hounsfield units), cancellous bone micro-architecture and mechanical properties. METHODS: Using pig vertebral cancellous bone, the bone specimens were imaged using clinical and micro-computed tomography scanners and subsequently subjected to uniaxial compression testing. RESULTS: Results indicate that micro-architecture can be predicted using clinical image intensity. Micro-architectural parameters relevant to osteoporosis study, such as percent bone volume, trabecular bone pattern factor, structure model index, trabecular thickness and trabecular separation have shown significant correlation with R2 values of 0.83, 0.80, 0.70, 0.72, and 0.54, respectively, when correlated to Hounsfield units. In addition, the correlation of mechanical properties (E, sigma yield, and sigma ult) in the superior-inferior direction (the primary loading direction), to micro-architecture parameters has also been good (R2 > 0.5) for all except tissue volume, tissue surface and degree of anisotropy. INTERPRETATION: This proves that the predictive power of bone strength and stiffness was improved with the combination of bone density and micro-architecture information. This work supports the prediction of micro-architecture using current clinical computed tomography imaging technology.     

Influence of knot configuration and tying technique on the mechanical performance of sutures

The purpose of this investigation was to determine the influence of knot configuration and tying technique on the mechanical performance of surgical sutures. Multifilament and monofilament nylon sutures were selected for this evaluation because they are commonly used in wound closure. The mechanical performance of these sutures was judged by the following parameters: knot breakage force, configuration of secure knots, and knot run down force. During each test, tension was applied at either rapid or slow rates, which correlates with the physician's speed of tying knots. On the basis of these mechanical performance tests, four throw square (1 = 1 = 1 =1) knots and five throw square (1 = 1 = 1 = 1 = 1) knots are recommended for monofilament nylon and multifilament nylon sutures, respectively, in which the speed of application of forces to the knots is relatively slow. Because these tests can easily be replicated in any laboratory, manufacturers now have a scientific basis for recommending specific tying techniques for their surgical sutures.     

同种异体人心脏主动脉与肺动脉瓣膜的生物力学比较

背景:目前同种心脏瓣膜已成熟应用于瓣膜替换手术及复杂先天性心脏病矫治手术中,但人心脏肺动脉瓣膜与主动脉瓣膜生物力学特性的对比研究报道较少.目的:对比分析深低温液氮保存人心脏主动脉瓣膜和肺动脉瓣膜的生物力学特性.方法:对比观察试验于2004-03/07在中国医学科学院心血管病研究所先天性心脏病研究室完成.取深低温液氮保存的健康成年男性脑死亡6 h内志愿捐献者的人心脏主动脉瓣膜和肺动脉瓣膜各6例,符合医学伦理学要求.应用HD-10型厚度仪测定瓣膜组织的厚度,应用Instron拉伸机测定周向瓣膜组织的生物力学参数:瓣膜组织的断裂强度、应力应变曲线的斜率及伸长比.结果与结论:与人主动脉瓣膜相比,人肺动脉瓣膜组织厚度明显变薄;但二者的乍物力学参数瓣膜组织的断裂强度、应力应变曲线的斜率及伸长比差异均无显著性意义(P>0.05).结果提示,人主动脉瓣膜与肺动脉瓣膜的生物力学特性基本相似,从瓣膜水平上分析,人肺动脉瓣膜可满足主动脉瓣位生物力学的需要.     

两种偶联剂改性纳米二氧化硅可影响树脂基托的力学性能

背景:聚甲基丙烯酸甲酯基托材料因其良好的生物相容性,色泽好,易于加工成型等优点被广泛使用,但因其韧性、硬度问题也存在容易折裂的不足.目的:对比两种偶联剂改性的纳米SiO2颗粒对聚甲基丙烯酸甲酯材料的弯曲强度、弯曲弹性模量和硬度改变.方法:将两种偶联剂KH-570 和KH-502 改性的纳米SiO2颗粒按质量比3%加入聚甲基丙烯酸甲酯粉体中制成(SiO2/聚甲基丙烯酸甲酯)纳米复合材料.实验分为聚甲基丙烯酸甲酯材料、纳米SiO2/聚甲基丙烯酸甲酯复合材料、KH-570-SiO2/聚甲基丙烯酸甲酯复合材料、KH-502-SiO2/聚甲基丙烯酸甲酯复合材料4 组.结果与结论:未经过偶联剂改性的纳米SiO2/聚甲基丙烯酸甲酯复合材料与聚甲基丙烯酸甲酯材料相比,其弯曲强度、弯曲弹性模量和硬度差异无显著性意义(P>0.05),而经过偶联剂改性的纳米SiO2/聚甲基丙烯酸甲酯复合材料与聚甲基丙烯酸甲酯材料之间比较,其弯曲强度、弯曲弹性模量显著增强(P<0.05),KH-502-SIO2/PMMA组弯曲强度、弯曲弹性模量和硬度值显著大于与其他3 组(P<0.05).结果表明,把经过偶联剂改性的纳米SiO2颗粒添加到聚甲基丙烯酸甲酯材料中制成SiO2聚甲基丙烯酸甲酯复合材料,可使材料的弯曲强度、弯曲弹性模量和硬度明显提高.而经过偶联剂KH-502 改性的纳米SiO2聚甲基丙烯酸甲酯复合材料性能提高更为显著.     

不同混合比例聚甲基丙烯酸甲酯的力学性能比较

背景:已证实不同聚合方式聚甲基丙烯酸甲酯的力学性能不同,且不同种类的聚甲基丙烯酸甲酯的力学性能也存在差异.目的:探讨不同混合比例聚甲基丙烯酸甲酯的力学性能差异.设计、时间及地点:材料学对比观察,于2009-02/05在天津医科大学总医院骨科生物力学实验室完成.材料:义齿基托树脂Ⅱ型自凝牙托粉由上海珊瑚化工厂生产,义齿基托树脂自凝牙托水由天津市口腔医院材料研究室生产.方法:在室温25℃环境下,将自凝牙托粉与牙托水分别按质量体积比1.5:1,1:1,1:1.25,1:1.5,1:1.75,1:2这6种不同混合比例调和,调配时搅拌速率为60次/min.当牙托水基本与牙托粉结合,无多余牙托水存在,黏着感消失时,即为填塞型盒最适宜时期,此时将混合材料充入直径13 mm、长度100 mm的模具中,分别制作出外形相同的聚甲基丙烯酸甲酯试件,对其进行压缩、拉伸和三点弯实验,直至屈服或破裂.主要观察指标:同混合比例聚甲基丙烯酸甲酯的抗压强度、抗拉强度、挠度和弹性模量.结果:①牙托粉与牙托水比例1.5:1,1:1组的抗压强度无明显差异(P=0.326),但均显著高于后4组(P<0.01);后3组的抗压强度无明显差异(P>0.05).②牙托粉与牙托水比例1.5:1,1:1,1:1.25组的抗拉强度无明显差异(P>0.05),但均显著高于后3组(P<0.01).后3组的抗拉强度无明显差异(P>0.05).③随着牙托粉与牙托水的比例越来越小,其挠度值逐渐增大,说明韧性越来越好.④从前5组来看,随着牙托粉与牙托水的比例越来越小,其弹性模量值逐渐缩小,说明试件的刚性越来越差(P<0.01).结论:聚甲基丙烯酸甲酯具有较高的强度和刚度,不同混合比例聚甲基丙烯酸甲酯的力学性能有明显差异.随着牙托粉与牙托水的混合比例逐渐缩小,聚合后液态单体的剩余量就越多,其抗压强度、抗拉强度和弹性模量值就越小.     

Mathematical relationships between bone density and mechanical properties: a literature review

BACKGROUND: In many published studies, elastic properties of bone are correlated to the bone density, in order to derive an empirical elasticity-density relationship. The most common use of these relationships is the prediction of the bone local properties from medical imaging data in subject-specific numerical simulation studies. The proposed relationships are substantially different one from the other. It is unclear whether such differences in elasticity-density relationships can be entirely explained in terms of methodological discrepancies among studies. METHODS: All relevant literature was reviewed. Only elasticity-density relationships derived from similarly controlled experiments were included and properly normalized. The resulting relationships were grouped according to the most important methodological differences: type of end support during testing, specimen geometry, and anatomical sampling location. FINDINGS: Even after normalization with respect to strain rate and densitometric measurement unit, substantial inter-study differences do exist, and they can only be partially explained by the methodological differences between studies. INTERPRETATION: Some recommendations are made for the application of elasticity-density relationships to subject-specific finite element studies. The importance of defining a standardized mechanical testing methodology for bone specimens is stressed, and some guidelines that emerged from the literature are proposed. To identify density-elasticity relationships suitable for use in subject-specific FE studies, the development of a benchmark study is also proposed, where the elasticity-density relationship is taken as the variable under study, and a numerical model of known numerical accuracy predicts experimental strain measurements.     

Comparison of mechanical compressive properties of commercial and autologous fibrin glues for tissue engineering applications

BackgroundFibrin glues are widely used in orthopedic surgery as adhesives and hemostatic agents. We evaluated the compressive properties of selected fibrin glues in order to identify which are appropriate for tissue regeneration applications subject to compression.MethodsUniaxial unconfined compression tests were performed on fibrin gels prepared from commercial and autologous products: (1) Evicel (Ethicon), (2) Tisseel (Baxter), (3) Angel (Arthrex), and (4) ProPlaz (Biorich). Cyclic loads were applied from 0 to 30% strain for 100 cycles at 0.5 Hz. Following cyclic testing, specimens were subjected to ramp displacement of 1% strain per second to 80% strain.FindingsThroughout cyclic loading, Evicel and Tisseel deformed (shortened) less than Angel at all but one time point, and deformed less than ProPlaz at cycles 10 and 20. The dynamic moduli, peak stress, and strain energy were significantly greater in Tisseel than all other groups. Evicel displayed significantly greater dynamic moduli, peak stress, and strain energy than Angel and ProPlaz. Following cyclic testing, Tisseel and Evicel were significantly less deformed than Angel. No specimens exhibited gross failure during ramp loading to 80% strain. Ramp loading trends mirrored those of cyclic loading.InterpretationThe tested commercial glues were significantly more resistant to compression than the autologous products. The compressive properties of Tisseel were approximately twice those of Evicel. All preparations displayed moduli multiple orders of magnitude less than that of native articular cartilage. We conclude that in knee surgeries requiring fibrin glue to undergo compression of daily activity, commercial products are preferable to autologous preparations from platelet-poor plasma, though both will deform significantly.     

肺与食管切除病人术后痰液性质对比研究

目的:进一步了解肺与食管切除病人术后呼吸道炎性反应和痰液黏弹性状况,为采取针对性护理措施提供依据.方法:测量39例肺与食管切除病人术后第1～5日痰白细胞计数,白细胞介素8(IL-8)水平和痰液黏、弹性等流变学指标.结果:肺切除组术后第2日痰白细胞计数最高(15.86×106mg-1),食管切除组术后第3日痰白细胞计数最高(17.81×106mg-1).肺切除组术后痰IL-8水平呈逐渐降低趋势,术后第4日明显降低至0.39ng·ml-1与术后第1日的2.61ng·ml-1比较差异显著(P=0.02).食管切除组术后第2日痰IL-8水平5.00ng·ml-1,明显高于第1日0.93ng·ml-1,有显著性差异(P=0.002),术后第3、4日逐渐降低.两组术后痰IL-8水平在术后第3、4日有显著性差异(P=0.05和0.01).食管切除组痰黏性明显低于肺切除组,除术后第1日外,均有显著性差异(P=0.00～0.03);肺切除组术后痰弹性大于食管切除组,术后1～3日有显著差异(P=0.00).结论①食管切除术后呼吸道炎性反应过程迟于肺切除术后,术后留置胃管可能是引起食管切除病人呼吸道炎性反应的相关因素.②肺切除术后痰黏弹性高于食管切除术后,对此类病人更应加强降低痰黏稠度的促进排痰护理措施.     

Comparison of nonuniform rotational distortion between mechanical IVUS and OCT using a phantom model

Optical coherence tomography (OCT) is an optical analog of mechanical intravascular ultrasound (M-IVUS) with much higher spatial resolution. However, no data exist regarding the nonuniform rotational distortion (NURD) with OCT. The aim of the study was to investigate whether OCT generates less NURD relative to M-IVUS. A coronary artery phantom model was constructed with a rubber ring (3.68 mm in diameter), located at the distal end of the phantom. This model was also composed of eight equally spaced steel wires and an additional marker-wire. Two types of vascular phantoms were used, mild curve (90 degrees ) and acute curve (near 180 degrees ). Subsequent M-IVUS (n = 6) and OCT (n = 6) imaging was performed. Eight angles between eight wires, except the marker-wire, were measured from each image. These angles, measured with M-IVUS and OCT, were compared with those of high-resolution optical photography as a gold standard. The average in angle differences was significantly smaller in OCT compared with M-IVUS in the mild curve model (3.2 +/- 1.0 degrees vs, 6.9 +/- 2.1 degrees , p < 0.01). Compared with the latter model, the average in angle differences was exaggerated in the acute curve model with M-IVUS (9.1 +/- 0.9 degrees vs. 6.9 +/- 2.1 degrees , p < 0.05) but not with OCT (3.5 +/- 0.8 degrees vs. 3.2 +/- 1.0 degrees , p= not significant). OCT generates significantly less NURD compared with M-IVUS, especially in tortuous situation.     

Comparison between the removal effect of mechanical, Nd:YAG, and Er:YAG laser systems in carious dentin.

OBJECTIVE: The purpose of this study was to compare the effectiveness of carious dentin removal by using an Er:YAG laser irradiation and Nd:YAG laser under a continuous water spray with that of the conventional mechanical treatment in vitro. BACKGROUND DATA: Lasers are being considered as a potential replacement of conventional mechanical systems to remove diseased and healthy dental hard tissues. METHODS: First, one half of the 10 carious lesions were treated with the round steel bur and then removed. The other half were treated with the Er:YAG laser at 200-mJ pulse energy at 2 Hz. After that, one half of another set of 10 teeth was subjected to the round steel bur in which the other half was removed using the Nd:YAG laser at 6-W output power, 20 pps, and under a continuous water spray (120 mL/min). Thermal change during each treatment and the time required for carious dentin removal was determined, and the surface characteristic was observed using the scanning electron microscopic (SEM). RESULTS: The Er:YAG or Nd:YAG laser irradiation time was almost two or three times longer than the bur treatment, respectively. From the SEM study, it was found that the lased cavity surface revealed various patterns of microirregularity, and there was also no smear layer. CONCLUSIONS: It can be suggested that under adequate water spray and with a careful irradiation technique, cavities without sign of thermal damage to the surrounding tissues as well as dental pulp could be produced with the Er:YAG and Nd:YAG laser.     

人工椎体的组织相容性和力学性能

背景：近年来,随着组织工程学的发展,椎体替代材料趋于多样化,学者们不再满足于其能否恢复椎体高度与即刻稳定性,而是更为关注远期的融合,良好的组织相容性和力学性能。目的：分析国内人工椎体的组织相容性和力学性能。方法：以＂人工椎体、相容性、生物力学＂为检索词在中国期刊全文数据库中检索与人工椎体生物相容性和生物力学研究相关的文献进行分析。结果与结论：人工椎体组织相容性的动物实验显示,纳米羟基磷灰石/聚酰胺66复合人工椎体成分和结构与人体骨相似,具有良好的生物相容性,成骨活性;可发生生物降解,其降解作用与成骨能力匹配。人工椎体的生物力学研究显示出纳米羟基磷灰石/聚酰胺66复合人工椎体不仅具有良好的生物活性,而且具有良好的轴向压缩载荷和椎间支撑能力,力学性能优异。生物陶瓷人工椎体不仅具有良好的生物相容性,而且在治疗椎体肿瘤中有靶向定位作用;金属材料的人工椎体经过多年的改进,其生物相容性亦可满足临床要求。就各类型人工椎体优劣而言,仍需进一步大量研究和实践,就其临床应用而言,需根据临床需要进行选择。     

异种骨支架材料的制备及其理化性能

目的:对比观察猪骨支架材料与同种异体骨支架材料的理化性能及力学性能。方法:实验于2006-03/12在南方医科大学人体解剖教研室(暨南方医科大学临床解剖学研究所和广东省组织构建与检测重点试验室)完成。实验材料:低温深冻6个月的6只成年猪(雌雄各3只)和4具新鲜健康成人尸体(男女各2具,由广州市红十字会南方医科大学遗体捐献接收点提供,家属知情同意)髂骨。实验方法:剔除软组织,刮除骨髓和骨膜,用锯骨机将松质骨切成5mm×5mm×40mm左右的骨条,超声清洗、H2O2和乙醇浸泡、甩干、冻干、辐照处理得到异种骨支架材料和同种异体骨支架材料。实验评估:①对2种材料进行扫描电镜观察。②对比2种材料孔隙率、蛋白质和钙磷含量及力学性能。结果:①扫描电镜观察结果:2种材料均具有骨本身的骨小梁、小梁间隙及骨内管腔系统,具有天然网状结构。三维支架系统形态完整。其中猪源性异种骨支架材料较人同种异体骨支架材料具有更多的三维孔隙,2种材料的孔隙大小接近,均在400μm左右。②材料蛋白质、钙磷含量及力学性能检测结果:异种骨支架材料的孔隙率高于同种异体骨[(57.20±1.37)%,(53.21±1.63)%,P<0.005],但蛋白含量低于同种异体骨[(23.36±0.48)%,(26.50±0.23)%,P<0.005],钙、磷含量与同种异体骨比较差异无显著性[钙:(1.7×105),(1.8×105)μg/g;磷:(1.0×105),(1.0×105)μg/g],2种材料弹性模量差异无显著性。结论:猪源性异种骨支架材料在理化性能方面与人骨支架材料极相近,可为骨细胞的生成提供基本的保证。     

人工椎体的组织相容性和力学性能

背景:近年来,随着组织工程学的发展,椎体替代材料趋于多样化,学者们不再满足于其能否恢复椎体高度与即刻稳定性,而是更为关注远期的融合,良好的组织相容性和力学性能。目的:分析国内人工椎体的组织相容性和力学性能。方法:以人工椎体、相容性、生物力学为检索词在中国期刊全文数据库中检索与人工椎体生物相容性和生物力学研究相关的文献进行分析。结果与结论:人工椎体组织相容性的动物实验显示,纳米羟基磷灰石/聚酰胺66复合人工椎体成分和结构与人体骨相似,具有良好的生物相容性,成骨活性;可发生生物降解,其降解作用与成骨能力匹配。人工椎体的生物力学研究显示出纳米羟基磷灰石/聚酰胺66复合人工椎体不仅具有良好的生物活性,而且具有良好的轴向压缩载荷和椎间支撑能力,力学性能优异。生物陶瓷人工椎体不仅具有良好的生物相容性,而且在治疗椎体肿瘤中有靶向定位作用;金属材料的人工椎体经过多年的改进,其生物相容性亦可满足临床要求。就各类型人工椎体优劣而言,仍需进一步大量研究和实践,就其临床应用而言,需根据临床需要进行选择。