A modified intramedullary nail interlocking design yields improved stability for fatigue cycling in a canine femur fracture model

Intramedullary nailing has evolved to become the standard of care for most diaphyseal femoral and tibial fractures, as well as an expanding number of metaphyseal fractures. Owing to the unstable nature of some fractures, the intramedullary device may be subjected to significant stresses owing to a lack of solid cortical contact after nailing. In such cases, excessive interfragmentary motion (due to construct toggle) has been shown to occur. Such motion increases the likelihood of a non- or delayed-union. In the current study, two versions of a modified, angle stable interlocking design were subjected to fatigue testing in a segmental defect fracture model representing a canine femur. As a control, a third group of constructs were stabilized with a traditional nail that allowed a small amount of toggle. All constructs were subjected to 50,000 fatigue cycles representing 12 weeks of cage activity at physiologic levels of combined axial-torsional loading. Torsional testing pre- and post-fatigue revealed 4.6 +/- 1.3 degrees of toggle in the traditional nail and no toggle with the angle stable nail designs. The stable nails were also significantly stiffer in axial compression and torsion before and after cycling. These data indicate that the enhanced stability of the modified interlocking designs can be maintained throughout fatigue cycling in a challenging fracture model.     

Biomechanical comparison of three second-generation reconstruction nails in an unstable subtrochanteric femur fracture model

The purpose of this study is to determine if a biomechanical difference exists in dynamic stiffness, fatigue life, and fracture site displacement by comparing three cephalomedullary reconstruction nails. An examination was made of the Biomet Uniflex reconstruction nail, the Biomet Vector nail, and the Stryker Howmedica Long Gamma nail in the fixation of an unstable subtrochanteric femur fracture model, using a synthetic bone model. Mean stiffness for each nail was initially determined in control specimens (i.e. no fracture and no instrumentation). The nail stiffness values were 1764.0 N/mm (controls), 373.61 N/mm (Uniflex), 294.27 N/mm (vector), and 656.36 N/mm (Gamma). The Gamma was statistically stiffer than the Uniflex and Vector (p < 0.002). Mean fatigue life measurements were: Uniflex at 52,891 cycles, failing at the most distal of the proximal two screw holes; Vector at 45,344 cycles, failing in the nail at the level of the fracture site; Gamma at 88,748 cycles failing at the lag screw hole. The p value between the Gamma and Vector was less than 0.01 and between Gamma and Uniflex was less than 0.05. The mean maximal axial displacement at the fracture site was 2.448 mm, 2.305 mm, and 0.790 mm for the Uniflex, Vector and Gamma, respectively. The p value between the Gamma and the other nails was < 0.01. The mean maximal transverse displacement at the fracture site was 1.223 mm, 1.197 mm, and 0.280 mm respectively. The p value between the Long Gamma and the other two nails was < 0.01. In conclusion, the Long Gamma nail demonstrated statistically significant fixation superiority in stiffness, resistance to fatigue, and fracture site displacement compared to the Uniflex and Vector nails. This biomechanical information may aid in choosing implants for fixation of unstable, subtrochanteric femur fractures.     

Tensile and compressive properties of the medial rabbit meniscus

Quantification of the material properties of the meniscus is of paramount importance, creating a 'gold-standard' reference for future tissue engineering research. The purpose of this study was to determine the compressive and circumferential tensile properties in the rabbit meniscus. Creep and recovery indentation experiments were performed on the meniscus using a creep indentation apparatus and analysed via a finite element optimization method to determine the compressive material properties at six topographical locations. Tensile properties of samples taken circumferentially from the rabbit meniscus were also examined. Results show that the femoral side of the anterior portion exhibits the highest aggregate modulus (510 +/- 100 kPa) and shear modulus (240 +/- 40 kPa), while the lowest aggregate modulus (120 +/- 30 kPa) and shear modulus (60 +/- 20 kPa) were found on the femoral side of the posterior location. Values of 156.6 +/- 48.9 MPa for Young's modulus and of 21.6 +/- 7.0 MPa for the ultimate tensile strength of were found from the tensile samples, which are similar to the values found in other animal models. These baseline values of material properties will be of help in future tissue engineering efforts.     

Experimental validation of a finite element model of a composite tibia

Composite bones are synthetic models made to simulate the mechanical behaviour of human bones. Finite element (FE) models of composite bone can be used to evaluate new and modified designs of joint prostheses and fixation devices. The aim of the current study was to create an FE model of a composite tibia and to validate it against results obtained from a comprehensive set of experiments. For this, 17 strain rosettes were attached to a composite tibia (model 3101, Pacific Research Laboratories, Vashon, Washington, USA). Surface strains and displacements were measured under 13 loading conditions. Two FE models were created on the basis of computed tomography scans. The models differed from each other in the mesh and material properties assigned. The experiments were simulated on them and the results compared with experimental results. The more accurate model was selected on the basis of regression analysis. In general, experimental strain measurements were highly repeatable and compared well with published results. The more accurate model, in which the inner elements representing the foam were assigned isotropic material properties and the elements representing the epoxy layer were assigned transversely isotropic material properties, was able to simulate the mechanical behaviour of the tibia with acceptable accuracy. The regression line for all axial loads combined had a slope of 0.999, an intercept of -6.24 microstrain, and an R2 value of 0.962. The root mean square error as a percentage was 5 per cent.     

方柱织构参数对吻合器钛钉表面疏水性能的影响*

对于吻合器钛钉等体内植入物,感染的第一步是细菌在材料表面的黏附,提高表面疏水性是减少细菌黏附的有效方法。基于仿生学和有限元仿真技术,通过在吻合器钛钉表面加工方柱织构,建立织构表面的液滴铺展模型,利用商用CFD软件ANSYS Fluent研究织构宽度、间距和高度对接触角的影响规律,分析织构参数对钛钉表面疏水性能的影响。仿真结果表明,在给定的织构参数范围内,钛钉表面方柱织构有效提升了表面疏水性,织构宽度和间距对接触角影响显著,且接触角随宽度和间距的增加都呈先增大后减小的趋势,最佳疏水结构为宽度略小于间距,而高度对接触角的影响几乎可以忽略,随着高度增加疏水性略微增大。     

Effect of sodium hypochlorite on the cyclic fatigue resistance: A scanning electron microscopy evaluation

The main purpose of this study was to compare the cyclic fatigue resistances of the three different nickel–titanium files in 2.5% sodium hypochlorite solution and distilled water at physiologic intracanal temperature (35°C). Three NiTi files such as One Curve (OC) (Micro‐Mega, Besancon, France), OneShape (OS) (Micro‐Mega), and Protaper Next (PTN) X2 (Dentsply Sirona, Ballaigues, Switzerland) were tested for cyclic fatigue resistance inside artificial stainless steel canal block with curvature 60° and 5 mm radius. The block was fixed inside a hot water bath of distilled water or 2.5% sodium hypochlorite and the temperature was set at 35 ± 1°C. The number of cycles to fracture data were recorded and all the fracture surfaces of files were evaluated by using scanning electron microscopy. The number of cyclic to fracture data were analyzed statistically via Kruskal–Wallis and Mann–Whitney U tests. OC showed the highest cyclic fatigue resistance at distilled water while PTN X2 showed the lowest cyclic fatigue resistance at 2.5% sodium hypochlorite. When cycling fatigue test medium were changed from distilled water to sodium hypochlorite solution, the resistance of the files to cyclic fatigue were decreased. SEM analysis confirmed that all scanned samples were fractured due to cyclic fatigue. The OC rotary instruments have more cyclic resistance than OS and PTN X2. The sodium hypochlorite solution reduces the resistance of the rotary instruments.     

Design of spinous process hooks for flexible fixation of the lumbar spine

A prototype flexible fixation system for the lumbar spine was subjected to tensile testing to failure and cyclic tensile testing in order to determine any regions of weakness. The system consisted of a spinous process hook and two laminar hooks made of stainless steel (316L). Each laminar hook was attached to the spinous process hook by a loop of polyester braid secured by a crimped metal sleeve. In five tensile tests, the system failed by irreversible deformation of the spinous process hook at 2.5 +/- 0.3 kN (mean +/- standard deviation). In three cyclic tests, in which the applied tension varied sinusoidally between 0.04 and 0.4 kN at a frequency of 5 Hz, failure occurred after less than 400,000 loading cycles. This occurred as a result of fatigue crack initiation and propagation in the spinous process hook. A finite element model showed a stress concentration in the region where the crack occurred, which raised the applied stress above the tensile fatigue strength of this stainless steel. The spinous process hook was redesigned for manufacture in a titanium alloy (Ti-6AI-4V ELI) to minimize artefacts in magnetic resonance imaging. Further finite element models showed no unacceptable stress concentrations.     

全自动钉排涂胶机的设计

主要介绍用于建筑装璜业的钉排加工的自动涂胶机的结构设计。该涂胶机可以完成自动上料、双面刷胶、自动输送、切断的全部功能,是一个自动化程度较高的生产设备。该设备的应用可以提高生产效率、提高产品质量,减少污染,对于该行业生产水平的提高有很大的实际意义,也填补了该技术领域的缺欠。     

高温环境下编织-嵌槽型金属橡胶的疲劳特性分析

采用拉-压式组合试验工装,以位移控制的加载方式对编织-嵌槽型金属橡胶进行了疲劳试验,研究了常温（25 ℃）及高温（300 ℃）环境下编织-嵌槽型金属橡胶在不同加载振幅下的疲劳特性,并通过平均刚度、等效黏性阻尼系数及其损伤因子对构件的损伤演化过程进行了表征。结果表明：编织-嵌槽型金属橡胶构件的疲劳损伤形式表现为磨损、断丝以及塑性变形;构件在各种试验条件下的疲劳过程均可分为刚度强化期和刚度衰减期,而构件力学性能的衰减主要发生在刚度衰减期;温度的升高或振幅的增大均会显著增大构件的积累损伤,进而缩短其使用寿命。     

A case of Leukonychia with scanning electron microscope observation

Leukonychia is a medical term for white discoloration appearing on nails. The pathophysiologic mechanisms that cause white discoloration are not entirely clear. We processed a case of leukonychia with scanning electron microscope observation and found many crispy, obviously dissociated "layers" in the lower part of the white nail plate. The dissociated "layers" were composed of thick, loose, coarse keratin bundles intertwined with each other. We believe the dissociated "layers" are related to the clinically noted white discoloration appearing on the nails.     

基于颜色空间的尿毒症诊断研究

由于传统甲诊易受到外界客观因素以及医生主观因素的影响,提出了一套甲象客观采集与信息分析相结合的中医甲诊系统用于尿毒症患者甲象客观化研究。采集并分割了15例尿毒症患者甲象正面照和侧面照,探究维持性血液透析前后甲色变化以及血红蛋白值与各色彩空间数值之间的关系等问题。利用相关分析和多元回归分析等统计学手段,对尿毒症患者血红蛋白值与维持性血液透析前后色彩空间值的关系进行了分析。实验结果表明,尿毒症患者血红蛋白值与多个色彩通道数值有一定的相关性,透析前后多个通道有显著变化,并建立了相关的多元回归方程。     

Mechanics of the passive knee joint. Part 2: interaction between the ligaments and the articular surfaces in guiding the joint motion

The aim of this study was to examine how the interaction between ligament tensions and contact forces guides the knee joint through its specific pattern of passive motion. A computer model was built based on cadaver data. The passive motion and the ligament lengthening and force patterns predicted by the model were verified with data from the literature. The contribution of each ligament and contact force was measured in terms of the rotational moment that it produced about the tibial medial plateau and the anterior-posterior (AP) force that it exerted on the tibia. The high tension of the anterior cruciate ligament (ACL) and the geometric constraints of the anterior horns of the menisci were found to be key features that stabilized the knee at full extension. The mutual effect of the cruciates was found as the reason for the screw-home mechanism at early flexion. Past 300, the AP component of contact force on the convex geometry of the lateral tibial plateau and tension of the lateral collateral ligament (LCL) were identified as elements that control the joint motion. From 60 degrees to 90 degrees, reduction in the tension of the ACL was determined as a reason for continuation of the tibial anterior translation. From 90 degrees to 120 degrees, increase in the tension of the posterior cruciate ligament and the AP component of the contact force on the convex geometry of the lateral tibial plateau pushed the tibia more anteriorly. This anterior translation was limited by the constraining effects of the ACL tension and the AP component of the contact force on the medial meniscus. The important guiding role observed for the LCL suggests that it should not be overlooked in knee models.     

Load transfer in the proximal tibia following implantation with a unicompartmental knee replacement: a static snapshot

Unicompartmental knee replacement (UKR) is an appealing alternative to total knee replacement when the patient has isolated medial compartment osteoarthritis. A common observation post-operatively is radiolucency between the tibial tray wall and the bone. In addition, some patients complain of persistent pain over the proximal tibia antero-medially; this may be related to elevated bone strains in the tibia. Currently, there is no intentionally made mechanical bond between the vertical wall of an Oxford UKR and the adjacent bone; whether one exists or not will influence the load transmission in the proximal tibia and may affect the elevated tibia strain. The aim of this study was to investigate how introducing a mechanical tie between the tibial tray wall and the adjacent bone might alter the load carried into the tibia for both cemented and cementless UKRs. Strain energy density in the region of bone adjacent to the tray wall was considerably increased when a mechanical tie was introduced; this has the potential of reducing the likelihood of a radiolucency occurring in that region. Moreover, a mechanical tie had the effect of reducing proximal tibia strain, which may decrease the incidence of pain following implantation with a UKR.     

Mechanical anisotropy of the human knee articular cartilage in compression

Articular cartilage exhibits anisotropic mechanical properties when subjected to tension. However, mechanical anisotropy of mature cartilage in compression is poorly known. In this study, both confined and unconfined compression tests of cylindrical cartilage discs, taken from the adult human patello-femoral groove and cut either perpendicular (normal disc) or parallel (tangential disc) to the articular surface, were utilized to determine possible anisotropy in Young's modulus, E, aggregate modulus, Ha, Poisson's ratio, v and hydraulic permeability, k, of articular cartilage. The results indicated that Ha was significantly higher in the direction parallel to the articular surface as compared with the direction perpendicular to the surface (Ha = 1.237 +/- 0.486 MPa versus Ha = 0.845 +/- 0.383 MPa, p = 0.017, n = 10). The values of Poisson's ratio were similar, 0.158 +/- 0.148 for normal discs compared with 0.180 +/- 0.046 for tangential discs. Analysis using the linear biphasic model revealed that the decrease of permeability during the offset compression of 0-20 per cent was higher (p = 0.015, n = 10) in normal (from 25.5 x 10(-15) to 1.8 x 10(-15) m4/N s) than in tangential (from 12.3 x 10(-15) to 1.3 x 10(-15) m4/N s) discs. Based on the results, it is concluded that the mechanical characteristics of adult femoral groove articular cartilage are anisotropic also during compression. Anisotropy during compression may be essential for normal cartilage function. This property has to be considered when developing advanced theoretical models for cartilage biomechanics.     

Changes in nail keratin observed by Raman spectroscopy after Nd:YAG laser treatment

Lasers and photodynamic therapy have been considered a convergence treatment for onychomycosis, which is a fungal infection on the nail bed and nail plate. Laser therapies have shown satisfactory results without significant complications for onychomycosis; however, the mechanism of clearing remains unknown. In this work, we investigated changes in the chemical structure of nail keratin induced by Nd:YAG laser using Raman spectroscopy. Toe nails with onychomycosis were treated with 1064 nm Nd:YAG laser. After laser treatment, the disulfide band (490–590 cm^?1) of nail keratin was rarely observed or was reduced in intensity. The amide I band (1500–1700 cm^?1) also showed changes induced by the laser. The α‐helical (1652 cm^?1) structures dominated the β‐sheet (1673 cm^?1) in nontreated nail, but the opposite phenomenon was observed after laser treatment.     

压电驱动共振式高频疲劳试验机构的设计与实验

针对在小振幅、高频受力工况下微小与硬脆材料构件的疲劳检测,提出利用压电振子(PZT、PLZT或PMN)作为高频疲劳试验机构的驱动力源,并利用系统共振方法设计高频疲劳试验机构.首先,介绍压电共振式疲劳试验机构的工作原理,建立了动力学模型,获得了系统的动态特性.然后,设计和制作了样机.最后,利用样机测量了作用在试件上的动载荷.实验结果表明;改变输入交流电压幅值(100～250 V)和板弹簧厚度(1.1～0.6 mm),可施加在试件上的动载荷为24.7～99.2 N.本文制成的样机适用于测试动载荷在为24.7～99.2 N,且在小振幅、高频受力工况下试件的拉伸和弯曲疲劳性能.     

Evaluation of an energy-based fatigue approach considering mean stress effects

In this paper, an attempt is made to extend the total strain energy approach for predicting the fatigue life subjected to mean stress under uniaxial state. The effects of means stress on the fatigue failure of a ferritic stainless steel and high pressure tube steel are studied under strain-controlled low cycle fatigue condition. Based on the fatigue results from different strain ratios, modified total strain energy density approach is proposed to account for the mean stress effects. The proposed damage parameter provides convenient means of evaluating fatigue life with mean stress effects considering the fact that the definitions used for measuring strain energies are the same as in the fully-reversed cycling (R = ?1). A good agreement is observed between experimental life and predicted life using proposed approach. Two other mean stress models (Smith-Watson-Topper model and Morrow model) are also used to evaluate the low cycle fatigue data. Based on a simple statistical estimator, the proposed approach is compared with these models and is found realistic.     

Coatings for fretting prevention

The purpose of the program to study coatings to prevent fretting fatigue was to determine the optimum fretting fatigue resistant coatings for titanium/steel mating surfaces found in helicopter rotor hub assemblies. Here several problems have been encountered during component accelerated fatigue tests of the hub assembly where fatigue failures of the titanium hub initiated at areas of severe fretting. In order to address this problem a program was developed to evaluate candidate coatings in terms of their ability to reduce or eliminate fretting of Ti-6Al-4V when in contact with 17-4 PH steel.This paper describes the new fretting test apparatus, the results obtained thus far on screening selected coatings which might have potential for fretting protection and an evaluation of bend bar test specimen configurations designed to achieve fretting fatigue under conditions comparable to those experienced in the actual rotor hub assemblies.     

Unipolar and bipolar right atrial appendage electrodes: comparison of sensing characteristics

To optimize atrial sensing and reject far-field signals (i.e., ventricular potentials seen in the atrium), the atrial amplitudes of electrograms (EGMs) should be as high as possible and the ventricular amplitudes as low as possible. To compare clinical sensing results obtained with unipolar and bipolar electrodes, endocardial EGMs were recorded on a high-speed multichannel recorder with a paper speed of 200 mm/second and frequency cutoffs at 0.1 and 2,000 Hz. Forty acute unipolar and 18 acute bipolar electrodes (in different patients), three matched pairs of unipolar and bipolar electrodes, and seven coronary sinus electrodes were measured. Unipolar and bipolar right atrial appendage (RAA) electrode EGMs were compared for 1) amplitude of EGM, 2) slew rate (dv/dt); and 3) amplitude of the ventricular EGM as measured through the RAA electrode. Unipolar RAA EGMs were compared with unipolar coronary sinus EGMs. Three bipolar leads were measured as unipolar and bipolar simultaneously. Bipolar atrial EGMs had equal amplitudes (unipolar, 4.2 +/- 2.1 mV, versus bipolar, 5.9 +/- 2.5; NS), higher slew rates (unipolar, 2.6 +/- 1.6 V/second, versus bipolar, 4.4 +/- 2.1; P less than 0.005), and lower ventricular (far-field) amplitudes (unipolar, 1.1 +/- 1.1 mV, versus bipolar, 0.7 +/- 0.6; P less than 0.02) when compared with unipolar RAA electrodes. This observation was confirmed in the measurement of the matched pairs atrial/ventricular amplitude ratio (unipolar, 4.7 +/- 2.2, versus bipolar, 8.7 +/- 2.0; P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)     

一种超声深滚与滚光一体化抗疲劳制造技术

采用一种超声深滚与滚光一体化的抗疲劳制造技术对钛合金疲劳试件进行表面强化处理。对经处理和未经处理的疲劳试件进行旋转弯曲疲劳试验。对疲劳试验后的试件断口进行扫描电镜观察分析。结果表明,超声深滚强化可以大幅提高钛合金试件的疲劳强度。强化后的试件表面形成一个组织致密层,起到抑制疲劳裂纹萌生和扩展的作用。对疲劳条纹的对比分析表明,超声深滚处理后的试件断口疲劳条纹明显细密化。