Recently, the use of metal-on-metal articulations in total hip arthroplasty (THA) has led to an increase in adverse events owing to local soft-tissue reactions from metal ions and wear debris. While ...the majority of these implants perform well, it has been increasingly recognised that a small proportion of patients may develop complications secondary to systemic cobalt toxicity when these implants fail. However, distinguishing true toxicity from benign elevations in cobalt ion levels can be challenging. The purpose of this two part series is to review the use of cobalt alloys in THA and to highlight the following related topics of interest: mechanisms of cobalt ion release and their measurement, definitions of pathological cobalt ion levels, and the pathophysiology, risk factors and treatment of cobalt toxicity. Historically, these metal-on-metal arthroplasties are composed of a chromium-cobalt articulation. The release of cobalt is due to the mechanical and oxidative stresses placed on the prosthetic joint. It exerts its pathological effects through direct cellular toxicity. This manuscript will highlight the pathophysiology of cobalt toxicity in patients with metal-on-metal hip arthroplasties.
Patients with new or evolving hip symptoms with a prior history of THA warrant orthopaedic surgical evaluation. Increased awareness of the range of systemic symptoms associated with cobalt toxicity, coupled with prompt orthopaedic intervention, may forestall the development of further complications.
Symptomatic cobalt toxicity from a failed total hip replacement is a rare but devastating complication. It has been reported following revision of fractured ceramic components, as well as in patients ...with failed metal-on-metal articulations. Potential clinical findings include fatigue, weakness, hypothyroidism, cardiomyopathy, polycythaemia, visual and hearing impairment, cognitive dysfunction, and neuropathy. We report a case of an otherwise healthy 46-year-old patient, who developed progressively worsening symptoms of cobalt toxicity beginning approximately six months following synovectomy and revision of a fractured ceramic-on-ceramic total hip replacement to a metal-on-polyethylene bearing. The whole blood cobalt levels peaked at 6521 µg/l. The patient died from cobalt-induced cardiomyopathy. Implant retrieval analysis confirmed a loss of 28.3 g mass of the cobalt-chromium femoral head as a result of severe abrasive wear by ceramic particles embedded in the revision polyethylene liner. Autopsy findings were consistent with heavy metal-induced cardiomyopathy.We recommend using new ceramics at revision to minimise the risk of wear-related cobalt toxicity following breakage of ceramic components.
As adverse events related to metal on metal hip arthroplasty have been better understood, there has been increased interest in toxicity related to the high circulating levels of cobalt ions. However, ...distinguishing true toxicity from benign elevations in cobalt levels can be challenging. The purpose of this review is to examine the use of cobalt alloys in total hip arthroplasty, to review the methods of measuring circulating cobalt levels, to define a level of cobalt which is considered pathological and to review the pathophysiology, risk factors and treatment of cobalt toxicity. To the best of our knowledge, there are 18 published cases where cobalt metal ion toxicity has been attributed to the use of cobalt-chromium alloys in hip arthroplasty. Of these cases, the great majority reported systemic toxic reactions at serum cobalt levels more than 100 μg/L. This review highlights some of the clinical features of cobalt toxicity, with the goal that early awareness may decrease the risk factors for the development of cobalt toxicity and/or reduce its severity.
Severe adverse events can arise from the release of cobalt from metal-on-metal arthroplasties, and as such, orthopaedic surgeons should not only be aware of the presenting problems, but also have the knowledge to treat appropriately.
Wrinkle defects can be formed during the production of wind turbine blades consisting of composite monolithic and sandwich laminates. Earlier studies have shown that the in-plane compressive strength ...of a sandwich panel with wrinkle defects may decrease dramatically. This study focuses on the failure modes of sandwich specimens consisting of thick GFRP face sheets with a wrinkle defect and a balsa wood core subjected to in-plane compression loading. Three distinct modes of failure were found, and the strain distributions leading up to these failures were established by use of digital image correlation (DIC). Finite element analyses were subsequently conducted to model the response of the test specimens prior to failure, and generally a very good agreement was found with the DIC measurements, although slight differences between the predicted and measured strain fields were observed in the local strain values around the wrinkle defect. The Northwestern University (NU) failure criterion was applied to predict failure initiation, and a good correlation with the experimental observations was achieved.
Background
Large amounts of fluids are daily prescribed to hospitalised patients across different medical specialities. Unfortunately, inappropriate fluid administration commonly causes iatrogenic ...hyponatraemia with associated increase in morbidity and mortality.
Methods/results
Fundamental for prevention of hospital‐acquired hyponatraemia is an understanding of what determines plasma sodium concentration (P‐Na+) in the individual patient. P‐Na+ is determined by balances of water and cations according to Edelman. This paper discusses the mechanisms influencing water and cation balances. In the hospitalised patient, non‐osmotic antidiuretic hormone secretion is frequent and results in a reduced renal electrolyte‐free water clearance (EFWC). This condition puts the patient at risk of hyponatraemia upon infusion of fluids that are hypotonic such as 5% glucose, Darrow‐glucose, NaKglucose and 0.45% NaCl in 5% glucose. It is suggested that individualised fluid therapy includes the following: Firstly, bolus therapy with Ringer‐acetate/Ringer‐lactate/0.9% NaCl in the hypovolaemic patient to minimise the risk of fluid under‐/overload. Secondly, P‐Na+ should be monitored together with the balances influencing P‐Na+. This may include EFWC in patients at additional risk of hyponatraemia. In patients with potentially reduced intracranial compliance (e.g. meningitis, intracranial bleeding, cerebral contusion and brain oedema), even a small decrease in P‐Na+ induced by slightly hypotonic fluids like Ringer‐acetate/Ringer‐lactate can increase the intracranial pressure dramatically. Consequently, 0.9 % NaCl is recommended as first‐line fluid for such patients.
Conclusions
The occurrence of hospital‐acquired hyponatraemia may be reduced by prescribing fluids, type and amount, with the same dedication as shown for other drugs.
Hyponatremia with cerebral symptoms is a medical emergency in which treatment delay may prove fatal. However, controversy prevails over which treatment is the best. This paper presents a practical ...and unified approach based on a literature study of the physiology of plasma Na+, the brain's response and clinical and experimental studies. Experimental and clinical studies were thoroughly reviewed. The literature was identified through MESH and free text search in the databases PubMed, Embase and Cochrane, and references in the literature. Cerebral water homeostasis is pivotal in hyponatremia. Prompt, repeated boluses of 2 ml/kg 3% saline constitute a rational treatment of symptomatic hyponatremia. After the initial correction, concern is mainly with avoiding overcorrection and osmotic demyelination. Plasma Na+ is determined by the external balances of water and cations. The water balance must therefore be carefully monitored to counter the dramatic increase in plasma Na+ that may result from brisk diuresis. Definitive treatment of hyponatremia should be directed toward its etiology. This can be challenging and the clinical application of traditional classifications based on hydration is difficult. Therefore, a practical approach is proposed based on the mechanisms of impaired urine dilution. Conclusions: The conflict between previously opposing standpoints is gradually giving way to an emerging consensus: Prompt bolus treatment of symptomatic hyponatremia with hypertonic saline. After the initial treatment, overcorrection must be avoided. Definitive treatment should be directed toward the nature of the underlying disorder. An approach based on the mechanism governing the impaired urine dilution has been proposed.
•A scenario-based damage assessment technique is proposed.•Within the scenario frame work the technique is able to locate and quantify structural alterations.•The article features an investigation of ...the available modal information for successful application.•The technique is demonstrate on experimental test cases based on 1200 modal tests.
In this paper a vibration-based damage localization and quantification method, based on natural frequencies and mode shapes, is presented. The proposed technique is inspired by a damage assessment methodology based solely on the sensitivity of mass-normalized experimental determined mode shapes. The present method differs by being based on modal data extracted by means of Operational Modal Analysis (OMA) combined with a reasonable Finite Element (FE) representation of the test structure and implemented in a scenario-based framework. Besides a review of the basic methodology this paper addresses fundamental theoretical as well as practical considerations which are crucial to the applicability of a given vibration-based damage assessment configuration. Lastly, the technique is demonstrated on an experimental test case using automated OMA. Both the numerical study as well as the experimental test case presented in this paper are restricted to perturbations concerning mass change.
Abstract
Background
Health literacy has been used to explain the social inequalities in ischemic heart disease that exists globally. However, most conceptualizations of health literacy employ an ...isolated focus on the patient's cognitive abilities without considering the social context. By using the cultural health capital framework, this paper aims at exploring how differences in social dispositions influence the interaction between doctors and ischemic heart patients with low health literacy and low socioeconomic status.
Methods
The paper is based on 30 qualitative interviews with Danish ischemic heart patients with low health literacy and low socioeconomic status and supplementary, contextual observations. The data collection was nationwide and carried out between October 2018 and August 2019.
Results
The findings showed that the patients and the doctors derived from different social spheres, which meant that they had developed dissimilar habitus and therefore used different explanatory models to understand and articulate the patient's problem. The doctors were primarily oriented towards the biomedical understanding of the malfunctioning of the body and therefore less aware of the patients' psychosocial illness experience. For the patients, these contradictions resulted in feelings of not being acknowledged, lack of trust in the healthcare system and disruption of treatment.
Conclusions
The findings suggest that to understand barriers for treatment of socially disadvantaged ischemic heart patients it is not only relevant to look at the patient's individual cognitive abilities but also to explore class-based contradictions in explanatory models between the patients and doctors.
Key messages
Health literacy should be understood as something embedded in the interplay between social structures and interpersonal dynamics. Contradictions in explanatory models may help explain barriers for treatment of socially disadvantaged ischemic heart patients.
