Effectiveness of silver alloy-coated silicone urinary catheters in patients with acute traumatic cervical spinal cord injury: Results of a quality improvement initiative.

Patients with acute traumatic cervical spinal cord injury (ATCSCI) have an increased risk of catheter-associated urinary tract infection (CAUTI). The effectiveness of silver alloy-coated silicone urinary catheters (SACC) in preventing CAUTI in ATCSCI is unknown and was the objective of this study. We performed a quality improvement initiative in an attempt to reduce CAUTI in patients undergoing spine surgery at a single quaternary center. Prior to July 2015, all patients received a latex indwelling catheter (LIC). All patients with ATCSCI with limited hand function (AIS A,B, or C) received a SACC. Incidence of CAUTI, microbiology, duration of infection, antibiotic susceptibility, and catheter-associated adverse events were recorded prospectively. We studied 3081 consecutive patients over the three years, of whom 302 (9.8%) had ATCSCI; 63% of ATCSCI patients were ASIA Impairment Scale (AIS) A or B. The overall rate of CAUTI was 19% (585/3081), and was 38% (116/302) in patients with ATCSCI. Of 178 ATCSCI patients with LIC, 100 (56%) developed a CAUTI compared with 28 of 124 (23%) patients with SACC (p < 0.05). Poly-microbial and gram-positive infection was more common in LIC than in SACC (p < 0.05). Median duration of infection was 9 days in SACC group and 12 days in LIC group (p = 0.08). Resistance to trimethoprim (p < 0.001) and ciprofloxacin (p < 0.05) were more common in LIC group. There was no difference in catheter-associated adverse events or length of stay between the groups. This quality improvement initiative illustrates the effectiveness of antiseptic silver alloy-coated silicone urinary catheters in patients with ATCSCI. In our population, the use of SACC reduces the incidence and the complexity of CAUTI.

Optimization design of a novel X-type six-high rolling mill based on maximum roll system stiffness.

The present investigation devices a novel X-type six-high (X-6h) mill. In addition, parametric models of different roll layouts such as the four-high (4-h), I-type six-high (I-6h), and X-6h mills are established. Three-dimensional (3D) finite element (FE) contact analysis for a strip rolling process is conducted when the mills are subjected to a constant vertical load of 65 kN. Through comparative analysis of von Mises stress, contact stress and elastic deformation displacement in three roll layouts, the rigidity characteristic of each is obtained, and it is found that the proposed X-6h mill has the largest roll gap stiffness. The influence of different roll diameter ratios on the roll gap stiffness of the roll system is investigated, based on which an optimization design model is built. Further, by taking into account the roll gap stiffness of the roll system as the optimization objective, the optimum diameter ratios of backup roll (BUR) to work roll (WR) of the X-6h rolling mill is achieved via the genetic algorithm (GA) optimization method, obtaining the optimum structural parameters of BUR and WR as well. The reliability of the proposed design is verified by manufacturing a prototype mill which produced magnesium alloy and aluminum alloy strips of high quality.

Mechanical behavior of a titanium alloy scaffold mimicking trabecular structure.

BACKGROUND: Additively manufactured porous metallic structures have recently received great attention for bone implant applications. The morphological characteristics and mechanical behavior of 3D printed titanium alloy trabecular structure will affect the effects of artificial prosthesis replacement. However, the mechanical behavior of titanium alloy trabecular structure at present clinical usage still is lack of in-depth study from design to manufacture as well as from structure to mechanical function. METHODS: A unit cell of titanium alloy was designed to mimick trabecular structure. The controlled microarchitecture refers to a repeating array of unit-cells, composed of titanium alloy, which make up the scaffold structure. Five kinds of unit cell mimicking trabecular structure with different pore sizes and porosity were obtained by modifying the strut sizes of the cell and scaling the cell as a whole. The titanium alloy trabecular structure was fabricated by 3D printing based on Electron Beam Melting (EBM). The paper characterized the difference between the designs and fabrication of trabecular structures, as well as mechanical properties and the progressive collapse behavior and failure mechanism of the scaffold. RESULTS: The actual porosities of the EBM-produced bone trabeculae are lower than the designed, and the load capacity of a bearing is related to the porosity of the structure. The larger the porosity of the structure, the smaller the stiffness and the worse the load capacity is. The fracture interface of the trabecular structure under compression is at an angle of 45o with respect to the compressive axis direction, which conforms to Tresca yield criterion. The trabeculae-mimicked unit cell is anisotropy. Under quasi-static loading, loading speed has no effect on mechanical performance of bone trabecular specimens. There is no difference of the mechanical performance at various orientations and sites in metallic workspace. The elastic modulus of the scaffold decreases by 96%-93% and strength reduction 96%-91%, compared with titanium alloy dense metals structure. The apparent elastic modulus of the unit-cell-repeated scaffold is 0.39-0.618 GPa, which is close to that of natural bone and stress shielding can be reduced. CONCLUSION: We have systematically studied the structural design, fabrication and mechanical behavior of a 3D printed titanium alloy scaffold mimicking trabecula bone. This study will be benefit of the application of prostheses with proper structures and functions.

Generating Lap Joints Via Friction Stir Spot Welding on DP780 Steel.

Friction stir spot welding (FSSW), a derivative of friction stir welding (FSW), is a solid-state welding technique that was developed in 1991. An industry application was found in the automotive industry in 2003 for the aluminum alloy that was used in the rear doors of automobiles. Friction stir spot welding is mostly used in Al alloys to create lap joints. The benefits of friction stir spot welding include a nearly 80% melting temperature that lowers the thermal deformation welds without splashing compared to resistance spot welding. Friction stir spot welding includes 3 steps: plunging, stirring, and retraction. In the present study, other materials including high strength steel are also used in the friction stir welding method to create joints. DP780, whose traditional welding process involves the use of resistance spot welding, is one of several high strength steel materials used in the automotive industry. In this paper, DP780 was used for friction stir spot welding, and its microstructure and microhardness were measured. The microstructure data showed that there was a fusion zone with fine grain and a heat effect zone with island martensite. The microhardness results indicated that the center zone exhibited a greater degree of hardness compared with the base metal. All data indicated that the friction stir spot welding used in dual phase steel 780 can create a good lap joint. In the future, friction stir spot welding can be used in high-strength steel welding applied in industrial manufacturing processes.

Low Environmental Temperature Influences the Fatigue Resistance of Nickel-titanium Files.

INTRODUCTION: The purpose of this study was to evaluate the effect of different temperatures (0°C, 10°C, 22°C, 37°C, and 60°C) on the cyclic fatigue life of nickel-titanium (NiTi) files using a new fatigue test model in zirconium oxide. METHODS: Three superelastic NiTi files (EndoSequence [Brasseler USA, Savannah, GA], ProFile [Dentsply Tulsa Dental Specialties, Tulsa, OK], and K3 [SybronEndo, Orange, CA]), and 3 heat-treated (K3XF [SybronEndo], Vortex [Dentsply Tulsa Dental Specialties], and HyFlex CM [Coltene-Whaledent, Allstetten, Switzerland]) NiTi files, all size 25/.04, were subjected to cyclic fatigue tests inside a novel, artificial ceramic canal with a curvature of 60° and a 5-mm radius. The model was immersed in water at 5 different preset temperatures. The number of cycles to failure (NCF) was recorded, and the fracture surface of the fragments was examined by a scanning electron microscope. The data were analyzed using 2-way analysis of variance with the significance level at 0.05. RESULTS: When the temperature was reduced from 60°C to 0°C, the NCF significantly increased from over 2 to 10 times for the NiTi file groups (P < .01). K3XF had the highest fatigue resistance of all files at 0°C (P < .05). Vortex files had the highest NCF at 10°C-60°C. The NCF of heat-treated files was significantly higher than superelastic NiTi files at 10°C and 20°C (P < .05). There was no significant difference in the NCF of HyFlex CM at 0°C and 22°C. There was little difference in the fractographic appearance among different temperatures, except that the fraction area occupied by the dimple region of some instruments at 0°C was slightly smaller than at 60°C. CONCLUSIONS: Cooling down to low temperatures may be an interesting strategy to improve the fatigue resistance of rotary NiTi files.

Design, characterisation and in vivo testing of a new, adjustable stiffness, external fixator for the rat femur.

Very little is known about the influence of the mechanical environment on the healing of large segmental defects. This partly reflects the lack of standardised, well characterised technologies to enable such studies. Here we report the design, construction and characterisation of a novel external fixator for use in conjunction with rat femoral defects. This device not only imposes a predetermined axial stiffness on the lesion, but also enables the stiffness to be changed during the healing process. The main frame of the fixator consists of polyethylethylketone with titanium alloy mounting pins. The stiffness of the fixator is determined by interchangeable connection elements of different thicknesses. Fixators were shown to stabilise 5 mm femoral defects in rats in vivo for at least 8 weeks during unrestricted cage activity. No distortion or infections, including pin infections, were noted. The healing process was simulated in vitro by inserting into a 5 mm femoral defect, materials whose Young's moduli approximated those of the different tissues present in regenerating bone. These studies confirmed that, although the external fixator is the major determinant of axial stiffness during the early phase of healing, the regenerate within the lesion subsequently dominates this property. There is much clinical interest in altering the mechanics of the defect to enhance bone healing. Our data suggest that, if alteration of the mechanical environment is to be used to modulate the healing of large segmental defects, this needs to be performed before the tissue properties become dominant.

Titanium alloys as fixation device material for cranioplasty and its safety in electroconvulsive therapy.

Here, we report the case of a patient successfully treated by a series of electroconvulsive therapy (ECT) who had implanted skull fixation devices made of titanium alloy. The patient was a 57-year-old man with bipolar I disorder. He was hospitalized for the treatment of manic symptoms of bipolar I disorder with pharmacotherapy and ECT. He sustained a fall and hit his head hard on the ground. Acute subdural hematoma developed, and emergent surgery to remove the hematoma was carried out. Cranioplasty was performed using fixation devices made of titanium alloy (Ti 6Al-4V). In order to control his manic symptoms, a series of ECT was readministered from 1 week after surgery. No adverse effects occurred. Devices must be investigated and chosen very carefully for permanent implantation, especially in patients during a course of ECT.

Tissue reaction to implants of different metals: a study using guide wires in cannulated screws.

Cannulated screws, along with guide wires, are typically used for surgical fracture treatment in cancellous bone. Breakage or bending deformation of the guide wire is a clinical concern. Mechanically superior guide wires made of Co-Cr alloys such as MP35N and L605 may reduce the occurrence of mechanical failures when used in combination with conventional (316L stainless steel) cannulated screws. However the possibility of galvanic or crevice corrosion and adverse tissue reaction, exists when using dissimilar materials, particularly in the event that a guide wire breaks, and remains in situ. Therefore, we designed an experiment to determine the tissue reaction to such an in vivo environment. Implant devices were designed to replicate a clinical situation where dissimilar metals can form a galvanic couple. Histological and SEM analyses were used to evaluate tissue response and corrosion of the implants. In this experiment, no adverse in vivo effects were detected from the use of dissimilar materials in a model of a broken guide wire in a cannulated screw.

Production of low-background CuSn6-bronze for the CRESST dark-matter-search experiment.

One of the most intriguing open questions in modern particle physics is the nature of the dark matter in our universe. As hypothetical weakly interacting massive particles (WIMPs) do interact with ordinary matter extremely rarely, their observation requires a very low-background detector environment regarding radioactivity as well as an advanced detector technique that allows for active discrimination of the still present radioactive contaminations. The CRESST experiment uses detectors operating at milli-Kelvin temperature. Energy deposition in the detectors is recorded via the simultaneous measurement of a phonon-mediated signal and scintillation emitted by the CaWO(4) crystal targets. The entire setup is made of carefully selected materials. In this note we report on the development of ultra-pure bronze (CuSn(6)) wire in small quantities for springs and clamps that are currently being used in the CRESST II setup.

Stress corrosion cracking of an aluminum alloy used in external fixation devices.

Treatment for compound and/or comminuted fractures is frequently accomplished via external fixation. To achieve stability, the compositions of external fixators generally include aluminum alloy components due to their high strength-to-weight ratios. These alloys are particularly susceptible to corrosion in chloride environments. There have been several clinical cases of fixator failure in which corrosion was cited as a potential mechanism. The aim of this study was to evaluate the effects of physiological environments on the corrosion susceptibility of aluminum 7075-T6, since it is used in orthopedic external fixation devices. Electrochemical corrosion curves and alternate immersion stress corrosion cracking tests indicated aluminum 7075-T6 is susceptible to corrosive attack when placed in physiological environments. Pit initiated stress corrosion cracking was the primary form of alloy corrosion, and subsequent fracture, in this study. Anodization of the alloy provided a protective layer, but also caused a decrease in passivity ranges. These data suggest that once the anodization layer is disrupted, accelerated corrosion processes occur.

Evidence of recycling of lead battery waste into highly leaded jewelry.

Inexpensive highly leaded jewelry, much of it imported from China, remains widely available in the United States. The source materials for these items are unknown. Due to the low cost of much of this trinket jewelry, it seems likely that scrap materials may be used in their manufacture. Thirty-nine jewelry items previously determined to contain 90% or more lead by weight were analyzed for antimony content. The average antimony content of these thirty-nine items was 3.0%. The range of antimony content in the samples was from 0.3% to 6.2% antimony by weight, with twenty-seven of the samples in the range of 2-4% antimony by weight. By comparison, battery lead standard reference material obtained from the US National Institute of Standards and Technology contains 2.95% antimony by weight. While the evidence is circumstantial, the similarity in composition of these samples to battery lead is striking and supports the hypothesis that some battery lead is being recycled into highly leaded jewelry items. These results suggest that the recycling of this waste in China needs to be investigated, as the use of lead battery waste as a source material for children's jewelry poses a clear threat to children's health.

[Shape-memory polymers for biomedical engineering applications].

The latest progress in shape-memory polymer for biomedical engineering applications was summarized in this paper. The mechanism responsible for shape memory effect was analyzed in reference to the polymer structure. Also introduced and reviewed were the characteristics of some shape-memory polymers (polyurethane polycaprolactone and polylactide) and their applications in medical engineering.

[X-ray fluorescence spectrometric determination of high rhenium content in rhenium-tungsten alloys used in traveling wave tube].

The matrix effect, spectral overlap and background were investigated for X-ray fluorescence (XRF) spectrometric determination of rhenium content according to the analysis requirement of rhenium-tungsten alloys, a key material used in traveling wave tube. The reason for causing the calibration curve nonlinear was explained theoretically when binary ratio technique of XRF was used. Both theoretical and experimental results show that linear calibration curve can be obtained if the curve is plotted by Re% vs. Re Lalpha X-ray intensity instead of binary ratio technique. The method is rapid and accurate and the results obtained in this work are in good agreement with those of chemical analysis. The method has been successfully applied to product quality control.

Mechanical properties of cast Ti-Hf alloys.

This study examined the mechanical properties of a series of Ti-Hf alloys. Titanium alloys with 10 to 40 mass % Hf were made with titanium and hafnium sponge in an argon-arc melting furnace. Specimens cast into magnesia-based investment molds were tested for yield strength, tensile strength, percentage elongation, and modulus of elasticity. Vickers microhardness was determined at 25 to 600 microm from the cast surface. X-ray diffractometry was also performed. Commercially pure Ti (CP Ti) and pure Ti prepared from titanium sponge were used as controls. The data (n = 5) were analyzed with a one-way ANOVA and the Student-Newman-Keuls test (alpha = 0.05). The diffraction peaks of all the metals matched those for alpha Ti; no beta phase peaks were found. Alloys with Hf > or = 25% had significantly (p < 0.05) higher yield and tensile strength compared to the CP Ti and pure Ti. There were no significant differences (p > 0.05) in elongation among all the Ti-Hf alloys and CP Ti, whereas the elongation of alloys with Hf > or = 30% was significantly (p < 0.05) lower than that of the pure Ti. The cast Ti-Hf alloys tested can be considered viable alternatives to CP Ti because they were stronger than CP Ti and had similar elongation.

A 3-year clinical evaluation of a gallium restorative alloy.

Several alternative materials have been suggested to take the place of amalgam, because of the environmental toxic effects of its mercury component. One such material is gallium-based alloy restoratives. The aim of this in vivo study was to compare the long-term clinical performance of a commercial gallium alloy with an admixed high copper amalgam alloy. For this purpose, 32 gallium and 32 amalgam restorations were placed in molar teeth in 14 human subjects. All the selected patients had at least two molar teeth that required restoration. In this way both restoratives were used in the same oral cavity. The restorations were examined at baseline, 6 months, 1, 2 and 3 years. At baseline, six teeth restored with gallium alloy showed post-operative sensitivity, whereas none of the amalgams were sensitive. At the end of 3 years, only a few amalgam restorations showed slight surface tarnish and marginal integrity loss. None of them needed replacement. Of the 32 gallium restorations placed, five had to be removed because of sensitivity, corrosion and tooth fracture. Also dramatic surface roughness and corrosion were noticed in 12 gallium restoration. According to the results of this clinical study, gallium-based restoratives should not be used before their physical properties are improved.

Toothbrushing causes elemental release from dental casting alloys over extended intervals.

The release of elements from dental alloys has been linked to alloy biocompatibility. Much of the research measuring elemental release has been done in vitro under passive conditions. The current study supplements a previous report that measured elemental release from dental alloys during and after the equivalent of 1 week of toothbrushing. In the current study, toothbrushing times were extended to the equivalent of 2 years, and elemental release was measured during and after brushing, with and without toothpaste. The results showed that for the major classes of dental alloys, brushing alone caused no significant elemental release during the brushing, and only minor increases after brushing. Brushing with toothpaste caused significant increases in elemental release for all elements of all alloys, but the largest increases were for the two nickel-based alloys. Nickel released during brushing with toothpaste reached 600-800 microg/cm(2) of alloy surface. Both beryllium-containing and non-beryllium-containing nickel-based alloys behaved similarly, refuting claims that non-beryllium alloys are superior in this regard. Thus, brushing with toothpaste under these extended in vitro conditions appears to increase the biological liabilities from elemental release for all alloys, but primarily for nickel-based alloys.

Surface conditions of Nitinol wires, tubing, and as-cast alloys. The effect of chemical etching, aging in boiling water, and heat treatment.

The surface conditions of Nitinol wires and tubing were evaluated with the use of X-ray photoelectron spectroscopy, high-resolution Auger spectroscopy, electron backscattering, and scanning-electron microscopy. Samples were studied in the as-received state as well as after chemical etching, aging in boiling water, and heat treatment, and compared to a mechanically polished 600-grit-finish Nitinol surface treated similarly. General regularities in surface behavior induced by the examined surface treatments are similar for wires, tubing, and studied as-cast alloy, though certain differences in surface Ni concentration were observed. Nitinol wires and tubing from various suppliers demonstrated great variability in Ni surface concentration (0.5-15 at.%) and Ti/Ni ratio (0.4-35). The wires in the as-received state, with the exception of those with a black oxide originating in the processing procedure, revealed nickel and titanium on the surface in both elemental and oxidized states, indicating a nonpassive surface. Shape-setting heat treatment at 500 degrees C for 15 min resulted in tremendous increase in the surface Ni concentration and complete Ni oxidation. Preliminary chemical etching and boiling in water successfully prevented surface enrichment in Ni, initially resulting from heat treatment. A stoichiometric uniformly amorphous TiO(2) oxide generated during chemical etching and aging in boiling water was reconstructed at 700 degrees C, revealing rutile structure.

Scanning electron microscopy analysis of corrosion degradation on tinplate substrates.

The degradation of electrolytic tinplate used in food containers was analysed and evaluated, using scanning electron microscopy and electrochemical measurements of microcorrosion and ion dissolution by atomic absorption to prevent food contamination caused by metal traces and to increase the durability of such tinplates.

Effect of surface treatment of NiTi alloy on its corrosion behavior in Hanks' solution.

The effect of surface modification of NiTi shape memory alloy on its corrosion behavior in Hanks' solution was determined. The near-equi-atomic super elastic NiTi (Ni 55.8 wt %) alloy used for this study was provided by Memry USA. The surfaces of heat-treated samples were modified by mechanical polishing (MP), electropolishing (EP), and electropolishing followed by chemical passivation (CP). As-heat-treated samples with straw-colored oxide finishes (SCO) and blue-colored oxide finishes (BO) also were included in the study. Surface analysis was performed using auger electron spectroscopy (AES), atomic force microscopy (AFM), and contact angle measurements (CAM). It was shown that surface roughness increased in the order CP < EP < SCO < BO < MP. The nickel release within the five groups of NiTi samples, as determined by atomic absorption spectrophotometry, reduced in time over the measured period. The level of Ni ions released over a 25-day immersion period was highest in the SCO sample (0.002 microg/day). This Ni level is negligible compared with the daily intake of Ni in an ordinary diet. The auger electron spectroscopy (AES) analyses indicated that before immersion in Hanks' physiologic solution, the main surface composition of all the samples was titanium and nickel, with a small amount of oxygen, carbon, and sulphur as contaminants. And the surface oxide thickness of the different samples increased in the order CP < EP < MP < BO < SCO. On the other hand, for the electrodes treated under the same conditions, the mean breakdown potential value decreased in the order BO > MP > CP > EP > SCO while the corrosion current density and rate increased in the order CP < SCO < EP < BO < MP.

An economic model to assess the cost and benefits of the routine use of silver alloy coated urinary catheters to reduce the risk of urinary tract infections in catheterized patients.

Prevalence studies generally find nosocomial urinary tract infections to be the most common type of nosocomial infection, accounting for between 21% and 45% of all HAIs. The main risk factor appears to be the presence of a urinary catheter, with an estimated 80% of these infections being associated with their use. This paper describes a model which quantifies the extent of the burden of these infections in terms of the number of patients affected and the costs incurred by the hospital sector; and identifies the potential benefits of the routine use of silver alloy coated catheters, as a means of reducing the incidence of this type of infection. An illustrative model of the annual costs and benefits associated with the routine use of this intervention in adult, non-day case patients admitted to the medical and surgical specialties of NHS hospitals throughout England is presented. The results suggest that a 14.6% reduction in the incidence of urinary tract infections in catheterized medical patients, and a 11.4% reduction in catheterized surgical patients, would cover the cost of the intervention. Any further reduction in incidence would result in net positive benefits.