Metal-on-Metal Hip Prostheses and Systemic Health: A Cross-Sectional Association Study 8 Years after Implantation

There is public concern over the long term systemic health effects of metal released from hip replacement prostheses that use large-diameter metal-on-metal bearings. However, to date there has been no systematic study to determine which organs may be at risk, or the magnitude of any effect. We undertook a detailed cross-sectional health screen at a mean of 8 years after surgery in 35 asymptomatic patients who had previously received a metal-on-metal hip resurfacing (MoMHR) versus 35 individually age and sex matched asymptomatic patients who had received a conventional hip replacement. Total body bone mineral density was 5% higher (mean difference 0.05 g/cm2 , P = 0.02) and bone turnover was 14% lower (TRAP 5b, mean difference 20.56IU/L, P = 0.006; osteocalcin, mean difference 23.08 ng/mL, P = 0.03) in the hip resurfacing versus conventional hip replacement group. Cardiac ejection fraction was 7% lower (mean absolute difference 25%, P = 0.04) and left ventricular end-diastolic diameter was 6% larger (mean difference 2.7 mm, P = 0.007) in the hip resurfacing group versus those patients who received a conventional hip replacement. The urinary fractional excretion of metal was low (cobalt 5%, chromium 1.5%) in patients with MoMHR, but creatinine clearance was normal. Diuretic prescription was associated with a 40% increase in the fractional excretion of chromium (mean difference 0.5%, P = 0.03). There was no evidence of difference in neuropsychological, renal tubular, hepatic or endocrine function between groups (P.0.05). Our findings of differences in bone and cardiac function between patient groups suggest that chronic exposure to low elevated metal concentrations in patients with well-functioning MoMHR prostheses may have systemic effects. Long-term epidemiological studies in patients with well-functioning metal on metal hip prostheses should include musculoskeletal and cardiac endpoints to quantitate the risk of clinical disease

The hydrothermal chemistry of Bismuth and the liquid Bismuth collector model.

Bismuth is an element used in a limited range of industrial, medical, cosmetic and other specialty applications. Because of a relatively low economic value, bismuth is rarely targeted directly in mining applications, since adequate supplies are obtained as a by-product of lead and copper production. With no compelling reason to investigate the variables that relate to the prospectivity of bismuth, there is relatively little known about the hydrothermal chemistry of Bi that may be applicable in geological environments such as those relative to ore deposit formation. However, understanding the hydrothermal geochemistry of Bi is important for understanding the Au-Bi association observed in many Au deposits, and its significance in terms of mineral exploration and mining, since Bi causes difficulties in Au metallurgy. Recently, a direct involvement of liquid bismuth in gold-partitioning reactions with aqueous fluids has been proposed as a mechanism responsible for the Au-Bi association. The aims of this thesis centre on three areas to advance the understanding of hydrothermal bismuth chemistry as it applies to the formation of gold deposits in particular, and those containing Bi more generally. Currently available thermodynamic data for Bi and Au compounds (metals, alloys, and minerals) and aqueous chemistry were compiled into a self-consistent thermodynamic database. Existing data for the system H-O-S-Bi-Cl-Na was fitted within the framework provided by the HCh software package, with the most novel development being the coupling of a non-random two liquids model for the Au-Bi melt with an aqueous phase described in terms of the Helgeson-Kirkham-Flowers (HKF) and Ryzhenko- Bryzgalin models. This provided a framework for exploring the interaction of gold-containing hydrothermal fluids and molten bismuth, providing estimates for the efficiency of the gold partitioning into liquid bismuth that is the central feature of the liquid bismuth collector model. The modelling predicted the ability of Bi-melt to scavenge Au from heavily undersaturated fluids, as well as Au:Bi ratios comparable to field observations. Experiments were conducted to simulate a hydrothermal ore forming environment and in particular test the ability of fluid-rock interaction to cause the precipitation of Bi-melt, and the ability of these melts to scavenge gold from solution. The flow-through experiments produced droplets of native bismuth via interaction with pyrrhotite. The textures are consistent with precipitation as a melt, and the droplets contained gold-rich inclusions in proportions consistent with Au-Bi melt phase relationships. An investigation of bismuth mineral solubility (bismuth oxide), using a combined spectroscopic (XANES/EXAFS) and solubility approach, provided thermodynamic data for the Bi(OH)₃(aq) species up to 609°C and 800 bar. For other group 15 metalloids (As, Sb) analogous complexes (As(OH)₃(aq),Sb(OH)₃(aq)) are the most important aqueous species under hydrothermal conditions and so this species was the first goal for a study into hydrothermal Bi chemistry. These experiments allowed the derivation of thermodynamic properties for the revised HKF equation of state for metal complexes and aqueous electrolytes – a commonly used framework for thermodynamic modelling of ore deposit formation. XANES spectroscopy confirms that the Bi(OH)₃(aq) complex carries a stereochemically active lone electron pair, and EXAFS data suggest that the geometry of the complex changes little over the temperature range 380-609 °C at 800 bar, with three oxygen neighbours at ~2.08 Å. The wealth of fundamental data collected in this study provides a much improved understanding of reactive transport of Bi and Au in hydrothermal systems, and allows a quantitative assessment of the role of Bi-melts in scavenging Au in gold deposits.Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 201

Structure and Thermal Stability of Bi(III) Oxy-Clusters in Aqueous Solutions

International audienceThe structure of Bi(III) clusters in aqueous concentrated acidic perchlorate solutions has been studied by means of X-ray absorption spectroscopy (XAS). The XAS data show that the polynuclear [Bi6O4(OH)4]6+ complex with a cage structure predominates at room temperature in acidic Bi-rich solutions. This complex breaks down to form mononuclear complexes with increasing temperature to 428 K. This behavior is consistent with theoretical predictions based on considerations of the electrostatic repulsion, which increases sharply as the dielectric constant of the solvent decreases with increasing temperature

The role of Te(IV) and Bi(III) chloride complexes in hydrothermal mass transfer: An X-ray absorption spectroscopic study

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