A Link Between the Tribology and Corrosive Degradation of Metal-on-Metal THRs

The degradation of Metal-on-Metal (MoM) Total Hip Replacements (THRs) is a complex mix of tribological, corrosive phenomena and their synergistic processes. Previous links between the corrosion of these devices and their sliding conditions over a cycle have been observed in simulator studies instrumented with a three-electrode electrochemical cell. This study further quantifies that link; demonstrating clear repeating periodicity in the anodic current transients of a 28 mm diameter MoM bearing under a standard ISO-14242 walking profile. A simplified 2D model and an expression of the Hamrock-Dowson equation was utilised to estimate the Theoretical Minimum Film Thickness (hmin) over a cycle, which was shown to match closely to the measured anodic current in both shape and magnitude

The Effect of Protein Structure and Concentration on Tribocorrosion and Film Formation on CoCrMo Alloys

The formation of tribochemical reaction layers, better known as tribofilms, on cobalt-chromium-molybdenum (CoCrMo) alloys commonly used in orthopaedic applications has been hypothesized to reduce degradation owing to wear and corrosion. However, the mechanisms and pathways influencing tribofilm formation remain largely unknown. This study aims to develop a clearer understanding of the role of protein structures and its concentration on tribocorrosion and surface tribofilms formed on CoCrMo alloys during boundary regime sliding. A reciprocating tribometer with a three-electrode electrochemical cell was employed to simulate and monitor the tribocorrosion of CoCrMo in situ. As-received Foetal Bovine Serum (as-FBS) and pre-heated FBS at 70 °C for 1 h (de-FBS) were diluted with saline (0.9% NaCl) at different concentrations (25% and 75% v/v) and utilized as electrolytes during the tribocorrosion tests. The result shows that the denatured protein structure in electrolyte tends to reduce the volume losses due to wear and corrosion on the CoCrMo samples with an appreciation of the protein tribofilms. On the other hand, an increased protein concentration increased the total volume loss due to corrosive processes. A novel finding revealed in this study is that the tribocorrosion mechanism of the CoCrMo surface is dependent on the protein structure, concentration and sliding duration due to the change in surface condition

Adverse loading effects on tribocorrosive degradation of 28 mm metal-on-metal hip replacement bearings

Following the high clinical failure rates of metal-on-metal total hip replacements much work has been undertaken to investigate their poor performance. So called adverse loading scenarios such as acetabular inclination and microseparation have been attributed to indicators for failure of the implants. The ISO hip simulation standards (ISO 14242:1) still rely on gravimetric and ex situ analysis, considering only the total wear during articulation. Live in situ sensing can provide valuable insight into the degradation mechanisms of metallic interfaces under such scenarios. Clinical 28 mm diameter metal-on-metal components were articulated in a full-ISO hip simulator. The bearings were subjected to increasing angles of acetabular inclination and retroversion over short-term periods of articulation. Corrosive degradation was monitored during sliding by means of an in situ three-electrode cell. Changing acetabular inclination from 30° to 50° resulted in greater cathodic shifts in OCP upon the initiation of sliding; from −50 mV to as much as −150 mV. Under anodic polarisation (0 mV vs. Ag/AgCl) the resultant currents at the initiation of sliding also increased significantly with inclination; from approximately 4–10 µA to over 120 µA. Increased retroversion of 20° also resulted in increased anodic currents of 55–60 µA. Changing the nature of articulation demonstrated increased corrosive material loss compared to a standard ISO 14242 profile. The sole use of gravimetric assessment to determine a wear rate for hip replacement bearings under simulation can therefore neglect important degradation mechanisms, such as tribocorrosive loss in devices with metal sliding interfaces

Fabrication of cartilage-inspired hydrogel/entangled polymer–elastomer structures possessing poro-elastic properties

The ability to replicate the load-bearing properties of articular cartilage is attractive for many engineering applications, particularly bearings where low friction, low wear, and high durability are required. Hydrogels are widely used materials spanning many diverse applications owing to their lubricity and unique mechanical/chemical properties. The poor mechanical characteristics of conventional hydrogels, especially their compressive behavior, limit their application in load-bearing applications despite their favorable properties such as poro/viscoelasticity and lubricity. This paper demonstrates a cartilage-inspired approach to produce a structure that benefits from water-swelling resistant and ultrafast recovery behavior of elastomers as well as the stress-relaxation and energy dissipation properties of hydrogels. A method is presented in this work to fabricate interconnected macro-porous elastomers based on sintering poly(methyl methacrylate) beads. The porous elastomer imparted structural support and resilience to its composite with an infused-grafted hydrogel. At 30% strain and depending upon the strain rate, the composite exhibited a load-bearing behavior that was 14–19 times greater than that of pristine hydrogel and approximately 3 times greater than that of the porous elastomer. The equilibrium elastic modulus of the composite was 452 kPa at a strain range of 10%–30%, which was close to the values reported for the modulus of cartilage tested with similar experimental parameters defined in this study. The dissipated energy for the composite at strain rates of 1 and 10–3 s–1 was enhanced by 25-, 25-, 5-, and 15-fold as compared to that for the pristine hydrogel and the porous elastomer, respectively. The cyclic loading tests at two strain rates showed that the composite immediately recovers its load-bearing properties with the maximum load recovery staying above 95% of its initial values throughout the testing. The permeability of the structures was measured experimentally, and the results showed a decrease of permeability by 3 orders of magnitude following hydrogel grafting

Practice development plans to improve the primary care management of acute asthma: randomised controlled trial

Background: Our professional development plan aimed to improve the primary care management of acute asthma, which is known to be suboptimal. Methods: We invited 59 general practices in Grampian, Scotland to participate. Consenting practices were randomised to early and delayed intervention groups. Practices undertook audits of their management of all acute attacks (excluding children under 5 years) occurring in the 3 months preceding baseline, 6-months and 12-months study time-points. The educational programme [including feedback of audit results, attendance at a multidisciplinary interactive workshop, and formulation of development plan by practice teams] was delivered to the early group at baseline and to the delayed group at 6 months. Primary outcome measure was recording of peak flow compared to best/predicted at 6 months. Analyses are presented both with, and without adjustment for clustering. Results: 23 consenting practices were randomised: 11 to early intervention. Baseline practice demography was similar. Six early intervention practices withdraw before completing the baseline audit. There was no significant improvement in our primary outcome measure (the proportion with peak flow compared to best/predicted) at either the 6 or 12 month time points after adjustment for baseline and practice effects. However, the between group difference in the adjusted combined assessment score, whilst non-significant at 6 months (Early: 2.48 (SE 0.43) vs. Delayed 2.26 (SE 0.33) p = 0.69) reached significance at 12 m (Early:3.60 (SE 0.35) vs. Delayed 2.30 (SE 0.28) p = 0.02). Conclusion: We demonstrated no significant benefit at the a priori 6-month assessment point, though improvement in the objective assessment of attacks was shown after 12 months. Our practice development programme, incorporating audit, feedback and a workshop, successfully engaged the healthcare team of participating practices, though future randomised trials of educational interventions need to recognise that effecting change in primary care practices takes time. Monitoring of the assessment of acute attacks proved to be a feasible and responsive indicator of quality care

Bond between microwave cured repair and concrete substrate

The bond strength between a concrete substrate and repair patch is critical to its durability. This paper investigates the effect of microwave curing the freshly applied repair, for 45 min at 132 Watts, on the 28 day bond strength between substrate concrete and different commercial repair materials. The repairs were applied at different ambient temperatures of 20, 10, 2 and −5 °C. Tensile split tests on repaired cube specimens were performed to determine the interfacial bond strength. The ability of microwave curing to prevent the detrimental effects of freezing at early age on the bond and compressive strength of repair patches is investigated. Experimental results show that microwave curing prevents loss of long term (28 day) repair/substrate bond strength of repair materials applied at freezing temperatures (−5 °C), relative to the repairs applied at higher temperatures (2–20 °C), except one lightweight repair formulation. In comparison, the control samples (non-microwave cured) of repairs applied at −5 °C suffered severe loss of bond strength and compressive strength due to early age freezing. In addition, no adverse effects on the bond strength and a small reduction of 6.75% in the 28 day compressive strength are observed in the early age microwave cured repairs applied at ambient temperatures of 2–20 °C. The repair/substrate bond strength is independent of the compressive strength of the repair material at all temperatures of repair application. Microwave curing can accelerate the concrete repair process and facilitate construction activity in cold weather

Improving Information on Maternal Medication Use by Linking Prescription Data to Congenital Anomaly Registers: A EUROmediCAT Study

Research on associations between medication use during pregnancy and congenital anomalies is significative for assessing the safe use of a medicine in pregnancy. Congenital anomaly (CA) registries do not have optimal information on medicine exposure, in contrast to prescription databases. Linkage of prescription databases to the CA registries is a potentially effective method of obtaining accurate information on medicine use in pregnancies and the risk of congenital anomalies. We linked data from primary care and prescription databases to five European Surveillance of Congenital Anomalies (EUROCAT) CA registries. The linkage was evaluated by looking at linkage rate, characteristics of linked and non-linked cases, first trimester exposure rates for six groups of medicines according to the prescription data and information on medication use registered in the CA databases, and agreement of exposure. Of the 52,619 cases registered in the CA databases, 26,552 could be linked. The linkage rate varied between registries over time and by type of birth. The first trimester exposure rates and the agreements between the databases varied for the different medicine groups. Information on anti-epileptic drugs and insulins and analogue medicine use recorded by CA registries was of good quality. For selective serotonin reuptake inhibitors, anti-asthmatics, antibacterials for systemic use, and gonadotropins and other ovulation stimulants, the recorded information was less complete. Linkage of primary care or prescription databases to CA registries improved the quality of information on maternal use of medicines in pregnancy, especially for medicine groups that are less fully registered in CA registries

The study protocol of a cluster-randomised controlled trial of family-mediated personalised activities for nursing home residents with dementia

<p>Abstract</p> <p>Background</p> <p>Following admission to a nursing home, the feelings of depression and burden that family carers may experience do not necessarily diminish. Additionally, they may experience feelings of guilt and grief for the loss of a previously close relationship. At the same time, individuals with dementia may develop symptoms of depression and agitation (BPSD) that may be related to changes in family relationships, social interaction and stimulation. Until now, interventions to alleviate carer stress and BPSD have treated carers and relatives separately rather than focusing on maintaining or enhancing their relationships. One-to-one structured activities have been shown to reduce BPSD and also improve the caring experience, but barriers such as a lack of resources impede the implementation of activities in aged care facilities. The current study will investigate the effect of individualised activities based on the Montessori methodology administered by family carers in residential care.</p> <p>Methods/Design</p> <p>We will conduct a cluster-randomised trial to train family carers in conducting personalised one-to-one activities based on the Montessori methodology with their relatives. Montessori activities derive from the principles espoused by Maria Montessori and subsequent educational theorists to promote engagement in learning, namely task breakdown, guided repetition, progression in difficulty from simple to complex, and the careful matching of demands to levels of competence. Persons with dementia living in aged care facilities and frequently visiting family carers will be included in the study. Consented, willing participants will be randomly assigned by facility to a treatment condition using the Montessori approach or a control waiting list condition. We hypothesise that family carers conducting Montessori-based activities will experience improvements in quality of visits and overall relationship with the resident as well as higher self-rated mastery, fewer depressive symptoms, and a better quality of life than carers in the waiting list condition.</p> <p>Discussion</p> <p>We hypothesise that training family carers to deliver personalised activities to their relatives in a residential setting will make visits more satisfying and may consequently improve the quality of life for carers and their relatives. These beneficial effects might also reduce nursing staff burden and thus impact positively on residential facilities.</p> <p>Trial Registration</p> <p>Australian New Zealand Clinical Trials Registry - <a href="http://www.anzctr.org.au/ACTRN12611000998943.aspx">ACTRN12611000998943</a></p

Cost-Effectiveness of a Telephone-Delivered Intervention for Physical Activity and Diet

Background: Given escalating rates of chronic disease, broad-reach and cost-effective interventions to increase physical activity and improve dietary intake are needed. The cost-effectiveness of a Telephone Counselling intervention to improve physical activity and diet, targeting adults with established chronic diseases in a low socio-economic area of a major Australian city was examined. Methodology/Principal Findings: A cost-effectiveness modelling study using data collected between February 2005 and November 2007 from a cluster-randomised trial that compared Telephone Counselling with a “Usual Care” (brief intervention) alternative. Economic outcomes were assessed using a state-transition Markov model, which predicted the progress of participants through five health states relating to physical activity and dietary improvement, for ten years after recruitment. The costs and health benefits of Telephone Counselling, Usual Care and an existing practice (Real Control) group were compared. Telephone Counselling compared to Usual Care was not cost-effective ($78,489 per quality adjusted life year gained). However, the Usual Care group did not represent existing practice and is not a useful comparator for decision making. Comparing Telephone Counselling outcomes to existing practice (Real Control), the intervention was found to be cost-effective ($29,375 per quality adjusted life year gained). Usual Care (brief intervention) compared to existing practice (Real Control) was also cost-effective ($12,153 per quality adjusted life year gained). Conclusions/Significance: This modelling study shows that a decision to adopt a Telephone Counselling program over existing practice (Real Control) is likely to be cost-effective. Choosing the ‘Usual Care’ brief intervention over existing practice (Real Control) shows a lower cost per quality adjusted life year, but the lack of supporting evidence for efficacy or sustainability is an important consideration for decision makers. The economics of behavioural approaches to improving health must be made explicit if decision makers are to be convinced that allocating resources toward such programs is worthwhile