Genotoxic effects of particles of surgical cobalt chrome alloy on human cells of different age in vitro

Among Gerontogens, Heavy Metals Are a Class of Their Own: A Review of the Evidence for Cellular Senescence

Advancements in modern medicine have improved the quality of life across the globe and increased the average lifespan of our population by multiple decades. Current estimates predict by 2030, 12% of the global population will reach a geriatric age and live another 3-4 decades. This swelling geriatric population will place critical stress on healthcare infrastructures due to accompanying increases in age-related diseases and comorbidities. While much research focused on long-lived individuals seeks to answer questions regarding how to age healthier, there is a deficit in research investigating what aspects of our lives accelerate or exacerbate aging. In particular, heavy metals are recognized as a significant threat to human health with links to a plethora of age-related diseases, and have widespread human exposures from occupational, medical, or environmental settings. We believe heavy metals ought to be classified as a class of gerontogens (i.e., chemicals that accelerate biological aging in cells and tissues). Gerontogens may be best studied through their effects on the "Hallmarks of Aging", nine physiological hallmarks demonstrated to occur in aged cells, tissues, and bodies. Evidence suggests that cellular senescence-a permanent growth arrest in cells-is one of the most pertinent hallmarks of aging and is a useful indicator of aging in tissues. Here, we discuss the roles of heavy metals in brain aging. We briefly discuss brain aging in general, then expand upon observations for heavy metals contributing to age-related neurodegenerative disorders. We particularly emphasize the roles and observations of cellular senescence in neurodegenerative diseases. Finally, we discuss the observations for heavy metals inducing cellular senescence. The glaring lack of knowledge about gerontogens and gerontogenic mechanisms necessitates greater research in the field, especially in the context of the global aging crisis.

Harris Hip Score and SF-36 following metal-on-metal total hip arthroplasty and hip resurfacing - a randomized controlled trial with 5-years follow up including 75 patients

Background

The metal-on-metal large-diameter-head (MoM-LDH) hip replacements increased in popularity during the start of the twenty-first century. Subsequently reports raised concerns regarding adverse reactions due to elevated chromium (Cr) and cobalt (Co) concentrations as well as high rates of other complications and revisions.

The purpose was to compare Harris Hip Score and SF-36 at 5-years follow up following MoM-LDH total hip arthroplasty (MoM-LDH-THA) or MoM hip resurfacing (MoM-HR).

Methods

The study was conducted between November 2006 to January 2012 in a tertiary health care center in Denmark. Patients with primary or secondary osteoarthritis were randomly assigned to receive a Magnum (MoM-LDH-THA) or a Recap (MoM-HR) prosthesis. Randomization was computer generated and allocation was concealed in an opaque envelope. Neither patients nor care provider were blinded. Primary outcome was Harris Hip Score at 5-years follow up.

Results

Seventy-five were included and allocated to the MoM-LDH-THA (n = 39) and MoM-HR (n = 36) group. The study was prematurely stopped due to numerous reports of adverse events in patients with MoM hip replacements. Thirty-three in the MoM-LDH-THA and 25 in the MoM-HR group were available for primary outcome analysis.

Median Harris Hip Score was 100 (IQR: 98–100) for MoM-LDH-THA and 100 (IQR: 93–100) for MoM-HR (p = 0.486). SF-36 score was high in both groups with no significant difference between groups.

Conclusion

Harris Hip Score and SF-36 score was excellent in both groups with no significant difference at 5-years follow up. Our findings suggest that there is no clinical important difference between the two prostheses implanted 5 years after implantation.

Trial registration

ClinicalTrials.gov, NCT04585022, Registered 23 September 2020 – Retrospectively registered.

This study was not prospectively registered in a clinical trial database since it was not an entirely implemented standard procedure in the international orthopedic society when the study was planned.

Toxicity risks of occupational exposure in 3D printing and bioprinting industries: A systematic review

3-Dimensional (3D) printing and bioprinting are the new technologies. In 3D printing, synthetic polymers such as acrylonitrile, butadiene, and styrene, polylactic acid, nylon, and some metals are used as feedstocks. During 3D printing, volatile organic compounds (VOCs) and nanoparticles can be released. In the bioprinting process, natural polymers are most commonly used. All of these materials have direct and indirect toxic effects in exposed people. Therefore, the aim of this study was to provide a comprehensive review of toxicity risks due to occupational exposure to pollutants in the 3D printing and bioprinting industries. The Cochrane review method was used as a guideline for systematic review. Articles were searched in the databases including PubMed, Scopus, Web of Science, and Google Scholar. This systematic review showed that VOCs and ultra-fine particles are often released in fused deposition modeling and selective laser sintering, respectively. Asthma, chronic obstructive pulmonary disease, allergic rhinitis, and DNA damage were observed in occupational exposure to synthetic polymers. Metal nanoparticles can induce adverse health effects on the respiratory and nervous systems. This study emphasized the need to further study the toxicity of 3D printing and bioprinting-induced air pollutants. Also, consideration of safety and health principles is necessary in 3D printing and bioprinting workplaces.

The effect of nanoparticles of cobalt-chromium on human aortic endothelial cells in vitro

Despite advances in stent technology for vascular interventions, in-stent restenosis (ISR) remains a main complication. The corrosion of cobalt-chromium (CoCr) alloy coronary stents has been identified to be associated with ISR, whereas its role in ISR has not been elucidated. In the current work, CoCr nanoparticles, simulated corrosion products of CoCr alloy, were used to investigate their effect on the endothelial cells. It has been demonstrated that the cell viability declines and the cell membrane is damaged, indicating the cytotoxicity of CoCr nanoparticles. The expression of GRP78, CHOP, and cleaved-caspase12 proteins has increased when exposed to CoCr nanoparticles, suggesting that CoCr nanoparticles induced cell apoptosis through endoplasmic reticulum (ER) stress-mediated apoptotic pathway. An increased release of adhesion and inflammatory mediators was also induced by CoCr nanoparticles, including ICAM-1, VCAM-1, IL-1β, IL-6, and TNF-α. Our results demonstrated that CoCr nanoparticles could trigger apoptosis, adhesion, and inflammation. These findings indicated potential damaging effects of CoCr nanoparticles on the vascular endothelium, which suggested corrosion of CoCr alloy may promote the progression and development of ISR.

Pseudotumors in Total Joint Arthroplasty

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The true incidence of pseudotumors in association with total joint arthroplasty is underestimated.

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Pseudotumors occur with metal-on-metal, metal-on-polyethylene, and metal-on-ceramic articulations.

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Metal ion levels should not be the only factor in decision-making regarding revision surgery.

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Revision surgery is only indicated in symptomatic patients with clinical and radiographic findings and elevated metal ion levels.

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Revision to a non-metal articulation is strongly suggested.

Chemical and in vitro bioanalytical assessment of drinking water quality in Manhiça, Mozambique

BACKGROUND

The chemical quality of drinking water is widely unknown in low-income countries.

OBJECTIVE

We conducted an exploratory study in Manhiça district (Mozambique) to evaluate drinking water quality using chemical analyses and cell-based assays.

METHODS

We measured nitrate, fluoride, metals, pesticides, disinfection by-products, and industrial organochlorinated chemicals, and conducted the bioassays Ames test for mutagenicity, micronuclei assay (MN-FACS), ER-CALUX, and antiAR-CALUX in 20 water samples from protected and unprotected sources.

RESULTS

Nitrate was present in all samples (median 7.5 mg/L). Manganese, cobalt, chromium, aluminium, and barium were present in 90-100% of the samples, with median values of 32, 0.6, 2.0, 61, 250 μg/l, respectively. Manganese was above 50 μg/l (EU guideline) in eight samples. Arsenic, lead, nickel, iron, and selenium median values were below the quantification limit. Antimony, cadmium, copper, mercury, zinc and silver were not present. Trihalomethanes, haloacetic acids, haloacetonitriles and haloketones were present in 5-28% samples at levels ≤4.6 μg/l. DDT, dieldrin, diuron, and pirimiphos-methyl were quantified in 2, 3, 3, and 1 sample, respectively (range 12-60 ng/L). Fluoride was present in one sample (0.11 mg/l). Trichloroethene and tetrachloroethene were not present. Samples were negative in the in vitro assays.

SIGNIFICANCE

Results suggest low exposure to chemicals, mutagenicity, genotoxicity and endocrine disruption through drinking water in Manhiça population. High concentration of manganese in some samples warrants confirmatory studies, given the potential link to impaired neurodevelopment.

Genotoxic properties of materials used for endoprostheses: Experimental and human data

Approximately 2 million endoprostheses are implanted annually and metal ions as well as particles are released into the body from the materials which are used. This review describes the results of studies concerning genotoxic damage caused by artificial joints. DNA damage leads to various adverse long-term health effects in humans including cancer. Experiments with mammalian cells showed that metal ions and particles from orthopedic materials cause DNA damage. Induction of chromosomal aberrations (CA) was found in several in vitro experiments and in studies with rodents with metals from orthopedic materials. Human studies focused mainly on induction of CA (7 studies). Only few investigations (4) concerned sister chromatid exchanges, oxidative DNA damage (2) and micronucleus formation (1). CA are a reliable biomarker for increased cancer risks in humans) and were increased in all studies in patients with artificial joints. No firm conclusion can be drawn at present if the effects in humans are due to oxidative stress and if dissolved metal ions or release particles play a role. Our findings indicate that patients with artificial joints may have increased cancer risks due to damage of the genetic material. Future studies should be performed to identify safe materials and to study the molecular mechanisms in detail.

Subcellular Performance of Nanoparticles in Cancer Therapy

With the advent of nanotechnology, various modes of traditional treatment strategies have been transformed extensively owing to the advantageous morphological, physiochemical, and functional attributes of nano-sized materials, which are of particular interest in diverse biomedical applications, such as diagnostics, sensing, imaging, and drug delivery. Despite their success in delivering therapeutic agents, several traditional nanocarriers often end up with deprived selectivity and undesired therapeutic outcome, which significantly limit their clinical applicability. Further advancements in terms of improved selectivity to exhibit desired therapeutic outcome toward ablating cancer cells have been predominantly made focusing on the precise entry of nanoparticles into tumor cells via targeting ligands, and subsequent delivery of therapeutic cargo in response to specific biological or external stimuli. However, there is enough room intracellularly, where diverse small-sized nanomaterials can accumulate and significantly exert potentially specific mechanisms of antitumor effects toward activation of precise cancer cell death pathways that can be explored. In this review, we aim to summarize the intracellular pathways of nanoparticles, highlighting the principles and state of their destructive effects in the subcellular structures as well as the current limitations of conventional therapeutic approaches. Next, we give an overview of subcellular performances and the fate of internalized nanoparticles under various organelle circumstances, particularly endosome or lysosome, mitochondria, nucleus, endoplasmic reticulum, and Golgi apparatus, by comprehensively emphasizing the unique mechanisms with a series of interesting reports. Moreover, intracellular transformation of the internalized nanoparticles, prominent outcome and potential affluence of these interdependent subcellular components in cancer therapy are emphasized. Finally, we conclude with perspectives with a focus on the contemporary challenges in their clinical applicability.

Are dual mobility cups associated with increased metal ions in the blood? Clinical study of nickel and chromium levels with 29 months' follow-up

INTRODUCTION

Dual mobility cups have become the implant of choice for older patients with a high risk of dislocation. However, to our knowledge, no study has explored the possibility of metal ion production with these implants that incorporate a polyethylene-on-metal bearing. This led us to conduct a prospective study to determine whether use of a dual mobility cup is accompanied by increased levels of nickel and chromium in the blood.

HYPOTHESIS

Use of a dual mobility cup is accompanied by an increase of nickel and chromium levels in the blood.

METHODS

Between 2012 and 2015, 16 consecutive patients were enrolled in the study. They underwent primary hip arthroplasty with a ceramic Biolox™ head (CeramTec, Plochingen, Germany), Corail™ titanium alloy stem (DePuy Synthes, Saint Priest, France) and a Novae™ dual mobility cup (SERF, Décines-Charpieu, France) consisting of 19% chromium (Cr) and 13-15% nickel (Ni). Patients who had other potential sources of nickel or chromium in their body (joint implants, dental implants, etc.) were excluded. The blood levels (μg/L) of nickel and chromium were measured preoperatively and at 2 years' follow-up by an independent laboratory (Biomnis) using inductively coupled plasma mass spectrometry. The upper limits set by the laboratory were<0.87μg/L for chromium and<1.0μg/L for nickel. AP and lateral X-rays of the pelvis were taken preoperatively and at each postoperative follow-up visit to look for signs of loosening. The Postel-Merle-d'Aubigné (PMA) score was determined preoperatively and at each postoperative follow-up visit. Surgical revision procedures for any cause were also documented.

RESULTS

The mean follow-up was 29 months [13-39]. Preoperatively, blood nickel ion levels were measured in 7 patients; they were below 1μg/L in 6 patients (86%) and at 1.5μg/L in 1 patient (14%). The mean preoperative chromium ion levels (n=7) was 0.2μg/L [0-0.8μg/L]. Postoperatively, all 16 enrolled patients had their blood ion levels checked at a mean follow-up of 29 months. The nickel ion levels averaged 1.69±1.49 [0.2-5.6] (with 4/16 having>2μg/L and 12/16>1μg/L) and the chromium ion levels averaged 0.5±0.11 [0.4-0.7] (with no patients>0.7μg/L). There were no signs of loosening or osteolysis on the follow-up radiographs. The mean PMA score at 2 years was 17.8 [17,18].

CONCLUSION

We found that dual mobility cups generate increased nickel but not chromium ions in the blood. The levels measured are comparable to those for other orthopedic implants such as spine implants. The clinical consequences of these increased levels are not known. Nevertheless, there were no clinical or radiological signs of loosening, although the follow-up was only 2 years.

LEVEL OF EVIDENCE

IV, Cohort study.

Differential toxicity of processed and non-processed states of CoCrMo degradation products generated from a hip simulator on neural cells

Physico-chemical characteristics of the CoCrMo degradation products have played an important role in cytotoxicity and clinical complications on the orthopedic patients who have metal implants. Previous studies have limited reflection on the physicochemical characteristics of the degradation products generated in vivo, which are very different from individual metal particles and/or ions obtained from different commercial sources. In this study, we aimed to understand the differences in toxicity induced by the degradation products in as-synthesized form as well as those obtained after post-processing. The degradation products were generated using a hip-simulator by maintaining physiological conditions closer to in vivo and separated into two batches, one with processing by washing and drying called processed degradation products (PDP) and another batch as 'as-synthesized' degradation product (DP). We studied the dose-dependent toxicity response by neural cells derived from induced pluripotent stem cells. The results of the study show that as-synthesized DPs are more toxic to neural cells even at lower concentrations studied with evident low TC50 (1-5 μg/ml) concentrations compared to PDP (25 μg/ml). Flow cytometric analysis showed a significant (p<.01) increase in uptake of the particles after 24 h and corresponding ROS production in DP-treated cells. RT-PCR analysis of oxidative specific gene expression showed, elevated mRNA levels of NADPH oxidase-1, nuclear transcription factor, superoxide dismutase-2 and glutaredoxin-2 in DP-treated cells after 6 h. The results of the study provided a clear evidence of the differential response of neural cells on the degradation products as a function of concentrations and their chemical nature.

Cobalt and its compounds: update on genotoxic and carcinogenic activities

This article summarizes recent experimental and epidemiological data on the genotoxic and carcinogenic activities of cobalt compounds. Emphasis is on the respiratory system, but endogenous exposure from Co-containing alloys used in endoprostheses, and limited data on nanomaterials and oral exposures are also considered. Two groups of cobalt compounds are differentiated on the basis of their mechanisms of toxicity: (1) those essentially involving the solubilization of Co(II) ions, and (2) metallic materials for which both surface corrosion and release of Co(II) ions act in concert. For both groups, identified genotoxic and carcinogenic mechanisms are non-stochastic and thus expected to exhibit a threshold. Cobalt compounds should, therefore, be considered as genotoxic carcinogens with a practical threshold. Accumulating evidence indicates that chronic inhalation of cobalt compounds can induce respiratory tumors locally. No evidence of systemic carcinogenicity upon inhalation, oral or endogenous exposure is available. The scarce data available for Co-based nanosized materials does not allow deriving a specific mode of action or assessment for these species.

Cobalt and Titanium nanoparticles influence on human osteoblast mitochondrial activity and biophysical properties of their cytoskeleton

We investigated the biophysical effects (cell elasticity and spring constant) caused on Saos-2 human osteoblast-like cells by nanosized metal (Co and Ti) wear debris, as well as the adhesive characteristics of cells after exposure to the metal nanoparticles. Cell mitochondrial activity was investigated using the MTT assays; along with LDH assay, metal uptake, cell apoptosis and mineralisation output (alizarin red assay) of the cells. Osteoblasts mitochondrial activity was not affected by Ti nanoparticles at concentrations up to 1 mg/ml and by Cobalt nanoparticles at concentrations < 0.5 mg/ml; however elasticity and spring constant were significantly modified by the exposure to nanoparticles of these metals in agreement with the alteration of cell conformation (shape), as result of the exposure to simulated wear debris, demonstrated by fluorescence images after actin staining.

Systemic and local toxicity of metal debris released from hip prostheses: A review of experimental approaches

Despite the technological improvements in orthopedic joint replacement implants, wear and corrosion products associated with the metal components of these implants may result in adverse local tissue and perhaps systemic reactions and toxicities. The current review encompasses a literature review of the local and systemic toxicity studies concerning the effect of CoCrMo wear debris released from wear and corrosion of orthopedic implants and prostheses. Release of metallic debris is mainly in the form of micro- and nano-particles, ions of different valences, and oxides composed of Co and Cr. Though these substances alter human biology, their direct effects of these substances on specific tissue types remain poorly understood. This may partially be the consequence of the multivariate research methodologies employed, leading to inconsistent reports. This review proposes the importance of developing new and more appropriate in-vitro methodologies to study the cellular responses and toxicity mediated by joint replacement wear debris in-vivo.

An evaluation of the potential consequences of drilling titanium and tantalum implants during surgery - a pilot study

Background

The aim of the study was to evaluate the potential consequences of drilling titanium alloy (Ti) and tantalum (Ta) implants.

Methods

During an in vitro study, four holes were made in each of two spatially porous trabecular implants: one Ta and the other Ti alloy (Ti-6Al-7Nb). The weight and the volume of particles produced during the drilling were then measured using a Radwag XA 110/2X (USA) laboratory balance.

Results

The loss of mass of the Ti and Ta implants was respectively 1.26 g and 2.48 g, and the volume of free particles was respectively 280 mm³ and 149 mm³. The particles were recovered after each stage. Despite the use of 5 μm filters, around 0.6% of the total implant mass from both implants was not recovered after drilling (roughly 2% of the mass of the particles created).

Conclusion

It is technically difficult to make holes in Ti and Ta implants using standard surgical tools, and the process creates a significant amount of metal particles which cannot be removed, despite intensive flushing. This may have a potentially adverse influence on the survival of the implant and result in negative systemic consequences.

Equal Primary Fixation of Resurfacing Stem, but Inferior Cup Fixation With Anterolateral vs Posterior Surgical Approach. A 2-Year Blinded Randomized Radiostereometric and Dual-energy X-Ray Absorptiometry Study of Metal-on-Metal Hip Resurfacing Arthroplasty

BACKGROUND

The anterolateral (AntLat) surgical approach may spare the blood supply to the femoral head and improve the accuracy of cup positioning in metal-on-metal hip resurfacing arthroplasty. Thereby, potentially lessen complications such as avascular head necrosis, femoral neck narrowing and fracture, improve implant fixation, and lessen periprosthetic bone mineral density (BMD) loss.

METHODS

Between November 2008 and January 2012, a randomized clinical trial was performed at Aarhus University Hospital. A total of 49 patients (28 males) were allocated to metal-on-metal hip resurfacing arthroplasty by the AntLat (n = 25) or the posterior (Post; n = 24) surgical approach. Patients were followed with radiostereometric analysis, measurements of periprosthetic BMD, clinical outcome scores of Harris hip score and visual analogue scale, serum metal ions, and conventional radiographs.

RESULTS

At 3 months, cups in the AntLat group had higher total translations of mean 1.00 ± 0.70 mm vs mean 0.64 ± 0.45 mm in the post group (P = .04), and higher total rotations of mean 2.44° ± 1.36° vs mean 1.39° ± 1.17° in the Post group (P = .002). All migrations of cup and stem were similar at 1 and 2 years postoperative (P > .07). At 1 year, periprosthetic BMD since postoperative at the medial side of the stem was reduced to mean 98.45% ± 8.57% in the AntLat group, and increased to mean 105.57% ± 11.07% in the Post group (P = .02), but measurements were comparable at 2 years (P = .05).

CONCLUSION

Cups inserted by the AntLat approach migrated more until 3 months postoperative. This illustrates a less good primary cup fixation with the AntLat approach; however, all cups were well-fixed after 3 months' follow-up indicating a good secondary fixation.

Development of malignant lymphoma after metal-on-metal hip replacement: a case report and review of the literature

A number of previous studies have reported a potential risk of malignancy, particularly hematological malignancy, developing in patients receiving a metal-on-metal (MoM) hip replacement. We report a case of malignant lymphoma that arose in a patient who had an MoM hip arthroplasty complicated by development of a pseudotumour. The tumour was a B cell follicular lymphoma that involved lymph nodes and bone. Metal ions are known to have a genotoxic effect on lymphoid cells. Although epidemiological studies have not established that there is an increased risk of lymphoma associated with MoM implants, only a relatively short time period has elapsed since re-introduction of this type of implant and long-term follow-up of patients with MoM implants is indicated.

Nanotoxicity: emerging concerns regarding nanomaterial safety and occupational hard metal (WC-Co) nanoparticle exposure

As the number of commercial and consumer products containing engineered nanomaterials (ENMs) continually rises, the increased use and production of these ENMs presents an important toxicological concern. Although ENMs offer a number of advantages over traditional materials, their extremely small size and associated characteristics may also greatly enhance their toxic potentials. ENM exposure can occur in various consumer and industrial settings through inhalation, ingestion, or dermal routes. Although the importance of accurate ENM characterization, effective dosage metrics, and selection of appropriate cell or animal-based models are universally agreed upon as important factors in ENM research, at present, there is no “standardized” approach used to assess ENM toxicity in the research community. Of particular interest is occupational exposure to tungsten carbide cobalt (WC-Co) “dusts,” composed of nano- and micro-sized particles, in hard metal manufacturing facilities and mining and drilling industries. Inhalation of WC-Co dust is known to cause “hard metal lung disease” and an increased risk of lung cancer; however, the mechanisms underlying WC-Co toxicity, the inflammatory disease state and progression to cancer are poorly understood. Herein, a discussion of ENM toxicity is followed by a review of the known literature regarding the effects of WC-Co particle exposure. The risk of WC-Co exposure in occupational settings and the updates of in vitro and in vivo studies of both micro- and nano-WC-Co particles are discussed.

The biological response to orthopaedic implants for joint replacement: Part I: Metals

Joint replacement is a commonly performed, highly successful orthopaedic procedure, for which surgeons have a large choice of different materials and implant designs. The materials used for joint replacement must be both biologically acceptable to minimize adverse local tissue reactions, and robust enough to support weight bearing during common activities of daily living. Modern joint replacements are made from metals and their alloys, polymers, ceramics, and composites. This review focuses on the biological response to the different biomaterials used for joint replacement. In general, modern materials for joint replacement are well tolerated by the body as long as they are in bulk (rather than in particulate or ionic) form, are mechanically stable and noninfected. If the latter conditions are not met, the prosthesis will be associated with an acute/chronic inflammatory reaction, peri-prosthetic osteolysis, loosening and failure. This article (Part 1 of 2) is dedicated to the use of metallic devices in orthopaedic surgery including the associated biological response to metallic byproducts is a review of the basic science literature regarding this topic. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2162-2173, 2017.

No association between pseudotumors, high serum metal-ion levels and metal hypersensitivity in large-head metal-on-metal total hip arthroplasty at 5-7-year follow-up

OBJECTIVE

The relationship between metal wear debris, pseudotumor formation and metal hypersensitivity is complex and not completely understood. The purpose of this study was to assess the prevalence of pseudotumor formation in a consecutive series of metal-on-metal (MoM) total hip arthroplasty (THA) and to investigate its relationship to serum metal-ion levels and hypersensitivity to metal.

METHODS

Forty-one patients (31 males), mean age 52 (28-68) years, with a total of 49 large-head MoM THA participated in a 5-7-year follow-up study. Patients underwent ultrasonography, serum metal-ion concentrations were measured, metal allergy and atopic dermatitis were evaluated, and the questionnaires of the Oxford Hip Score (OHS), Harris Hip Score (HHS) and the Short-Form Health Survey (SF-36) were completed.

RESULTS

Pseudotumors were found in eight patients, but they were asymptomatic and their serum metal-ion levels were similar to those observed in patients with no pseudotumors (p > 0.36). The capsule-stem distance of mean 8.6 mm (SD 3.82, 95% CI: 5.40-11.79) was wider (p = 0.02) in patients with pseudotumours than in patients without pseudotumors of mean 5.6 mm (SD 2.89, 95% CI: 4.68-6.58). Positive patch test reactions were seen in three patients. Higher serum metal-ion levels of chromium and cobalt were significantly correlated with steeper cup inclination and smaller femoral head sizes, and were associated with female gender (p < 0.04).

CONCLUSION

We found no association between pseudotumor formation, serum metal-ion levels, metal patch test reactivity, and atopic dermatitis. However, clinicians should be aware of asymptomatic pseudotumors, and we advise further exploration into the mechanisms involved in the pathogenesis of pseudotumors.

Selected aspects of the action of cobalt ions in the human body

Cobalt is widespread in the natural environment and can be formed as an effect of anthropogenic activity. This element is used in numerous industrial applications and nuclear power plants. Cobalt is an essential trace element for the human body and can occur in organic and inorganic forms. The organic form is a necessary component of vitamin B₁₂ and plays a very important role in forming amino acids and some proteins in nerve cells, and in creating neurotransmitters that are indispensable for correct functioning of the organism. Its excess or deficiency will influence it unfavourably. Salts of cobalt have been applied in medicine in the treatment of anaemia, as well as in sport as an attractive alternative to traditional blood doping. Inorganic forms of cobalt present in ion form, are toxic to the human body, and the longer they are stored in the body, the more changes they cause in cells. Cobalt gets into the body in several ways: firstly, with food; secondly by the respiratory system; thirdly, by the skin; and finally, as a component of biomaterials. Cobalt and its alloys are fundamental components in orthopaedic implants and have been used for about 40 years. The corrosion of metal is the main problem in the construction of implants. These released metal ions may cause type IV inflammatory and hypersensitivity reactions, and alternations in bone modelling that lead to aseptic loosening and implant failure. The ions of cobalt released from the surface of the implant are absorbed by present macrophages, which are involved in many of the processes associated with phagocytose orthopaedic biomaterials particles and release pro-inflammatory mediators such as interleukin-1 (IL-1), interleukin-6 (IL-6), tumour necrosis factor α (TNF-α), and prostaglandin.

Toxicology of wear particles of cobalt-chromium alloy metal-on-metal hip implants Part II: Importance of physicochemical properties and dose in animal and in vitro studies as a basis for risk assessment

The objective of the Part II analysis was to evaluate animal and in vitro toxicology studies of CoCr particles with respect to their physicochemistry and dose relevance to metal-on-metal (MoM) implant patients as derived from Part I. In the various toxicology studies, physicochemical characteristics were infrequently considered and administered doses were orders of magnitude higher than what occurs in patients. Co was consistently shown to rapidly release from CoCr particles for distribution and elimination from the body. CoCr micron sized particles appear more biopersistent in vivo resulting in inflammatory responses that are not seen with similar mass concentrations of nanoparticles. We conclude, that in an attempt to obtain data for a complete risk assessment, future studies need to focus on physicochemical characteristics of nano and micron sized particles and on doses and dose metrics relevant to those generated in patients or in properly conducted hip simulator studies.

Effect of surgical experience on imageless computer-assisted femoral component positioning in hip resurfacing--a preclinical study

Background

The clinical outcome of hip resurfacing (HR) as a demanding surgical technique associated with a substantial learning curve depends on the position of the femoral component. The aim of the study was to investigate the effects of the level of surgical experience on computer-assisted imageless navigation concerning precision of femoral component positioning, notching, and oversizing rate, as well as operative time.

Methods

Three surgeons with different levels of experience in both HR and computer-assisted surgery (CAS) prepared the femoral heads of 54 synthetic femurs using the Durom^TM Hip Resurfacing (Zimmer, Warsaw, IN, USA) system. Each surgeon prepared a total of 18 proximal femurs using the Navitrack® system (ORTHOsoft Inc., Montreal, Canada) or the conventional free-hand Durom^TM K-wire positioning jig. The differences between planned and postoperative stem shaft angle (SSA) and anteversion angle in standardized x-rays were measured and the operative time, not including the time for calibrating the CAS-system, was documented. Notching was evaluated by the three surgeons in a randomized manner. Oversizing was determined by the difference of the preoperative determined cap and the cap size advised by the CAS-system.

Results

CAS significantly reduced the overall mean deviation between planned and postoperative SSA in comparison with the conventional procedure (mean ± SD, 1 ± 1.7° vs. 7.4 ± 4.4°, P <0.01) regardless of the surgeon’s level of experience. The incidence of either varus or valgus SSA deviations exceeding 5° were 1/27 for CAS and 15/27 for the conventional method, respectively (P <0.001), corresponding to a reduction by 97%. Using CAS, the rate of notching was reduced by 100%.

Conclusions

The accuracy of femoral HR component orientation is significantly increased by use of CAS regardless of the surgeon’s level of experience in our preclinical study. Thus, imageless computer-assisted navigation can be a valuable tool to improve implant positioning in HR for surgeons at any stage of their learning curve.

Whole blood metal ion measurement reproducibility between different laboratories

Monitoring patients' metal ion blood concentrations can be useful in cases of problematic metal on metal hip implants. Our objective was to evaluate the reproducibility of metal ion level values measured by two different laboratories. Whole blood samples were collected in 46 patients with metal on metal hip arthroplasty. For each patients, two whole blood samples were collected and analyzed by two laboratories. Laboratory 1 had higher results than laboratory 2. There was a clinically significant absolute difference between the two laboratories, above the predetermined threshold, 35% of Cr samples and 38% of Co samples. All laboratories do not use the same technologies for their measurements. Therefore, decision to revise a metal on metal hip arthroplasty should rely on metal ion trends and have to be done in the same laboratory.

No association between serum metal ions and implant fixation in large-head metal-on-metal total hip arthroplasty

BACKGROUND

The mechanism of failure of metal-on-metal (MoM) total hip arthroplasty (THA) has been related to a high rate of metal wear debris, which is partly generated from the head-trunnion interface. However, it is not known whether implant fixation is affected by metal wear debris.

PATIENTS AND METHODS

49 cases of MoM THA in 41 patients (10 women) with a mean age of 52 (28-68) years were followed with stereoradiographs after surgery and at 1, 2, and 5 years to analyze implant migration by radiostereometric analysis (RSA). Patients also participated in a 5- to 7-year follow-up with measurement of serum metal ions, questionnaires (Oxford hip score (OHS) and Harris hip score (HHS)), and measurement of cup and stem positions and systemic bone mineral density.

RESULTS

At 1-2 years, mean total translation (TT) was 0.04 mm (95% CI: -0.07 to 0.14; p = 0.5) for the stems; at 2-5 years, mean TT was 0.13 mm (95% CI: -0.25 to -0.01; p = 0.03), but within the precision limit of the method. For the cups, there was no statistically significant TT or total rotation (TR) at 1-2 and 2-5 years. At 2-5 years, we found 4 cups and 5 stems with TT migrations exceeding the precision limit of the method. There was an association between cup migration and total OHS < 40 (4 patients, 4 hips; p = 0.04), but there were no statistically significant associations between cup or stem migration and T-scores < -1 (n = 10), cup and stem positions, or elevated serum metal ion levels (> 7µg/L (4 patients, 6 hips)).

INTERPRETATION

Most cups and stems were well-fixed at 1-5 years. However, at 2-5 years, 4 cups and 5 stems had TT migrations above the precision limits, but these patients had serum metal ion levels similar to those of patients without measurable migrations, and they were pain-free. Patients with serum metal ion levels > 7 µg/L had migrations similar to those in patients with serum metal ion levels < 7 µg/L. Metal wear debris does not appear to influence the fixation of hip components in large-head MoM articulations at medium-term follow-up.

Wear Debris Characterization and Corresponding Biological Response: Artificial Hip and Knee Joints

Wear debris, of deferent sizes, shapes and quantities, generated in artificial hip and knees is largely confined to the bone and joint interface. This debris interacts with periprosthetic tissue and may cause aseptic loosening. The purpose of this review is to summarize and collate findings of the recent demonstrations on debris characterization and their biological response that influences the occurrence in implant migration. A systematic review of peer-reviewed literature is performed, based on inclusion and exclusion criteria addressing mainly debris isolation, characterization, and biologic responses. Results show that debris characterization largely depends on their appropriate and accurate isolation protocol. The particles are found to be non-uniform in size and non-homogeneously distributed into the periprosthetic tissues. In addition, the sizes, shapes, and volumes of the particles are influenced by the types of joints, bearing geometry, material combination, and lubricant. Phagocytosis of wear debris is size dependent; high doses of submicron-sized particles induce significant level of secretion of bone resorbing factors. However, articles on wear debris from engineered surfaces (patterned and coated) are lacking. The findings suggest considering debris morphology as an important parameter to evaluate joint simulator and newly developed implant materials.

Habitat monitoring and genotoxicity in Ucides cordatus (Crustacea: Ucididae), as tools to manage a mangrove reserve in southeastern Brazil

In Brazil, the state of São Paulo contains both preserved areas (Juréia-Itatins Ecological Station) and extremely impacted ones (Cubatão Municipality). This study evaluated the concentrations of five metals (Cu, Cd, Cr, Pb, and Hg) in two mangroves with different levels of anthropogenic impact and the apparent genotoxicity to Ucides cordatus. Water and sediment samples were obtained, and metal concentrations were determined with an atomic absorption spectrophotometer. The genotoxic impact was quantified based on the number of micronucleated cells per 1,000 analyzed (MN‰), using hemolymph slides stained with Giemsa. Metal concentrations in water were below the detection limit, except for lead, although no significant difference was observed between the areas (P > 0.05). Sediment from Cubatão had higher concentrations of Cd, Pb, Cr, and Cu than sediment from Juréia-Itatins (P < 0.05), but no significant differences in metal concentrations were detected among depth strata of the sediment (P > 0.05). Crabs from Cubatão had a 2.6 times higher mean frequency of micronucleated cells (5.2 ± 1.8 MN‰) than those from Juréia-Itatins (2.0 ± 1.0 MN‰; P < 0.0001). The more-polluted conditions found in the mangrove sediments of Cubatão were reflected in the micronucleus assay, demonstrating their genotoxic effect; however, genetic damage should be attributed to a synergistic effect with other kinds of pollutants previously recorded in different environments of Cubatão. U. cordatus proved to be an excellent bioindicator of mangrove pollution. This study established, for the first time, the normal frequency of MN‰ in a population of this species within an ecological station.

The effects on bone cells of metal ions released from orthopaedic implants. A review

The increasing use of orthopedic implants and, in particular, of hip and knee joint replacements for young and active patients, has stimulated interest and concern regarding the chronic, long-term effects of the materials used. This review focuses on the current knowledge of the adverse biologic reactions to metal particles released from orthopaedic implants in vivo and in vitro. More specifically, the purpose of this article is to provide an overview of the current literature about the adverse effects of metal particles on bone cells and peri-implant bone.

European multidisciplinary consensus statement on the use and monitoring of metal-on-metal bearings for total hip replacement and hip resurfacing

INTRODUCTION

There is an ongoing debate about the optimal use of metal-on-metal (MoM) bearings in total hip replacement, since there are uncertainties about local and systemic adverse effects due to wear and corrosion of these bearings. Despite various national recommendations, efforts to achieve international harmonization of specific evidence-based recommendations for best practice are still lacking.

HYPOTHESIS

An international consensus study group should be able to develop recommendations on the use and monitoring of MoM bearings, preferably at the European level, through a multidisciplinary approach, by integrating the perspectives of various stakeholders.

MATERIALS AND METHODS

Twenty-one experts representing three stakeholder groups and eight countries participated in this European consensus study, which consisted of a consensus meeting, subsequent structured discussion, and consensus voting.

RESULTS

The current statement defines first of all benefits, local and systemic risks, as well as uncertain issues related to MoM bearings. Safety assessment after implantation of MoM comprises all patients. A closer follow-up is recommended for large head MoM (≥36mm) and resurfacing. In these implants basic follow-up should consist of x-rays and metal ion measurement of cobalt in whole blood, performed with GF-AAS or ICP-MS. Clinical and/or radiographic abnormality as well as elevated ion levels needs additional imaging (ultrasound, CT-scan and/or MARS-MRI). Cobalt values less than 2 μg/L are probably devoid of clinical concern, the threshold value for clinical concern is expected to be within the range of 2-7 μg/L.

DISCUSSION

This is the first multinational, interdisciplinary, and multiprofessional approach for developing a recommendation for the use and monitoring of MoM bearings in total hip replacement. The current recommendations are in partial agreement with previous statements regarding the extent of follow-up and imaging techniques. They however differ from previous communications regarding measurement of metal ions and especially the investigated medium, technique, and eventual threshold levels.

LEVEL OF EVIDENCE

Level V, expert opinion/agreement conference.

Transplacental passage of metal ions in women with hip resurfacing: no teratogenic effects observed

Over recent years, hip resurfacing has been performed in young, active patients, including women in their child bearing years. Current work investigating the transplacental passage of metal ions (cobalt and chromium) suggests significant passage of ions across the placenta in mothers with metal on metal hip resurfacing. In vitro studies show that cobalt and chromium can create DNA and chromosome damage in human cells. The consequences of this ion transfer on the child during fetal development and thereafter have not been fully quantified. We report on 3 patients with metal on metal hip resurfacings who had the prosthesis in situ during pregnancy. Our data show that umbilical cord blood chromium levels are under a quarter of the maternal serum levels. Cord blood cobalt levels are approximately half that of maternal blood. All 3 children are healthy. Although there was transplacental passage of ions, there was no significant effect on the child in these cases. We did not show any teratogenic effect of metal ions on the child, and this is consistent with the reported literature.

Clinical usefulness of blood metal measurements to assess the failure of metal-on-metal hip implants

In April 2010, a Medicines and Healthcare Products Regulatory Agency safety alert concerning all metal-on-metal (MOM) hip replacements recommended measuring chromium and cobalt concentrations when managing patients with painful prostheses. The need for this review is illustrated by the recent surge in requests for these blood tests from orthopaedic surgeons following this alert. The aim is to provide guidance to laboratories in assessing these requests and advising clinicians on interpretation. First, we summarize the basic terminology regarding the types of hip replacements, with emphasis on the MOM type. Second, we describe the clinical concerns over implant-derived wear debris in the local tissues and distant sites. Analytical aspects of the measurement of the relevant metal ions and what factors affect the levels measured are discussed. The application of inductively coupled plasma mass spectrometry techniques to the measurement of these metals is considered in detail. The biological effects of metal wear products are summarized with local toxicity and systemic biological effects considered, including carcinogenicity, genotoxicity and systemic toxicity. Clinical cases are used to illustrate pertinent points.

Molecular and immune toxicity of CoCr nanoparticles in MoM hip arthroplasty

Theoretical, desirable features of second-generation metal-on-metal (MoM) hip prostheses have led to their widespread use. However, the bearing surfaces, consisting of complex cobalt-chromium alloys, are subject to wear and the release of cobalt and chromium (CoCr) nanoparticles. These nanoparticles can reduce cellular viability, induce DNA damage, lead to chromosomal aberrations, and possibly stimulate increased metal hypersensitivity. Clinically, the effects can be both local (soft-tissue reactions) and systemic (arthroprosthetic cobaltism). This review assesses the literature concerning the in vitro and in vivo cytotoxic, genotoxic, and immunotoxic effects of CoCr wear particles, which is increasingly important in view of the large number of MoM arthroplasties performed.

New insights into wear and biological effects of metal-on-metal bearings

BACKGROUND

Despite the renewed interest in metal-on-metal implants in the past two decades, the underlying wear mechanisms and biological effects are still not fully understood.

METHODS

This paper first reviews the tribology of metal-on-metal bearings, bringing new insights into the interaction of wear and corrosion, and putting the characteristics and the potential origin of wear particles in perspective with the proposed wear mechanisms. It then summarizes the current knowledge on the biological effects of particles and metal ions in relation to these wear mechanisms.

RESULTS

Tribochemical reactions play an important role in the wear of metal-on-metal joints. The generated tribomaterial, which progressively forms by mechanical mixing of the uppermost nanocrystalline zone of the metal surface with proteins from the synovial fluid, governs the wear rate and influences the corrosive behavior of the bearing. Nanometer-sized wear particles may initially originate from the passivation layer covering the implant surface and then detach from this tribolayer. The inflammatory response observed surrounding metal-on-metal implants appears to be lower than that around metal-on-polyethylene implants. However, metallic byproducts, which can complex with proteins, may lead to a T lymphocyte-mediated hypersensitivity response.

CONCLUSIONS

The tribolayer appears to have beneficial effects on the wear rate. Much information has been gained on wear particle characteristics, but the exact mechanisms of particle detachment remain to be further elucidated. Excessive wear along with a hypersensitivity response may be at the origin of the early adverse tissue reactions that have been recently reported in some patients with metal-on-metal implants.

Senescence in cells in aseptic loosening after total hip replacement

Particle-induced osteolysis is a major cause of aseptic loosening after total joint replacement. The purpose of the current study was to evaluate cellular senescence of macrophages and giant cells in patients with aseptic hip loosening by determination of SA-β-Gal (SA-β-galactosidase), a reliable and frequently used indicator of cellular senescence. The level of senescence in capsule and interface membranes was significantly higher in patients with aseptic loosening in comparison to specimens from patients without aseptic loosening. Using Spearman's rank correlation, we found that the expression of SA-β-Gal in giant cells (p=0.002) and macrophages (p=0.050) in the interface membranes correlates significantly with the degree of polyethylene debris. We speculate that the induction of DNA damage by wear particles is responsible for premature senescence. Consequently, we conclude that the form of senescence observed in this study is a "stress-induced senescence".

Thinking about the role (largely ignored) of heavy metals in cancer prevention: hexavalent chromium and melanoma as a case in point

Ultraviolet (UV) light exposure accounts for only 40-50% of the attributable risk for cutaneous melanoma (CM); also classical UV-induced lesions are rare in melanomas (especially among CM with NRAS or BRAF mutations). It is therefore likely that an additional environmental factor exists as familial and genetic factors play a role in less than 5%. A large amount of (largely forgotten) epidemiologic data indicates that heavy metal exposure is strongly associated with the development of CM. Also, epidemiologic studies of patients with joint replacement indicate a marked subsequent time-related increase in melanoma in patients with metal-on-metal hip arthroplasties. In these patients chromium and cobalt levels rise to 10x normal and stay elevated at levels two- to threefold normal for at least 10 years. Chromium is widely used in industry for its anticorrosive and steel-strengthening properties and is widespread in everyday materials. Our hypothesis is therefore that chromium, alone or in conjunction with UV, plays a major role in the pathogenesis of CM. We have incubated human neonatal melanocytes for more than 10 weeks in the presence of a wide range and concentrations of metals without effect except by hexavalent chromium Cr(VI)and to a lesser degree Co²(+). After prolonged culture, chromium-incubated cells produced foci and when replated secondary colonies formed. We have just begun to study this phenomenon in more detail and studies without and with different wavelengths of UV will be explored. Of interest is that aneuploidy (a universal chromosomal change in cutaneous melanoma) in lymphocytes in patients with hip-on-hip metal prostheses has been demonstrated by others.

Effects of metal-on-metal wear on the host immune system and infection in hip arthroplasty

BACKGROUND AND PURPOSE

Joint replacement with metal-on-metal (MOM) bearings have gained popularity in the last decades in young and active patients. However, the possible effects of MOM wear debris and its corrosion products are still the subject of debate. Alongside the potential disadvantages such as toxicity, the influences of metal particles and metal ions on infection risk are unclear.

METHODS

We reviewed the available literature on the influence of degradation products of MOM bearings in total hip arthroplasties on infection risk.

RESULTS

Wear products were found to influence the risk of infection by hampering the immune system, by inhibiting or accelerating bacterial growth, and by a possible antibiotic resistance and heavy metal co-selection mechanism.

INTERPRETATION

Whether or not the combined effects of MOM wear products make MOM bearings less or more prone to infection requires investigation in the near future.

The genotoxicity of physiological concentrations of chromium (Cr(III) and Cr(VI)) and cobalt (Co(II)): an in vitro study

Humans are exposed to chromium and cobalt in industry, from the environment and after joint replacement surgery from the CoCr alloy in the implant. In this study we have investigated whether Cr(III), Cr(VI), Co(II) and Cr in combination with Co could induce chromosome aberrations in human fibroblasts in vitro at the same concentrations that have been found in the peripheral blood of exposed humans. We used 24 colour M-FISH as a sensitive way to detect translocations and aneuploidy and examined the effects of a 24-h exposure and its consequences up to 30 days after the exposure in order to record genomic instability and/or repair. At these physiological doses the metals induced predominantly numerical rather than structural aberrations. Co was the least reactive and Cr(VI) especially in combination with Co the most. All metals at the highest physiological doses caused simple (gain or loss of 3 or less chromosomes) and complex (more than 49 chromosomes) aneuploidy. All metals at the lowest physiological dose caused a significant increase of total aberrations. Cr(VI) was much more effective than Cr(III) in causing chromosome fragments, which were only induced at the highest doses. There was a slow resolution of aneuploidy with time after exposure. This involved a reduction in the proportion of aneuploid cells and a reduction of the number of chromosomes within cells showing complex aneuploidy. We conclude that these metal ions can cause chromosome aberrations at physiological concentrations and that their main effect is aneugenic.

A retrospective comparative study of mortality and causes of death among patients with metal-on-metal and metal-on-polyethylene total hip prostheses in primary osteoarthritis after a long-term follow-up

Background

All patients with total hip arthroplasty (THA), especially those with metal-on-metal (MM) THA, are exposed to metallic particles and ions, which may cause total or site-specific mortality. We analyzed the causes of total and site-specific mortality among a cohort of patients with MM and with metal-on-polyethylene (MP) THA after a long follow-up time.

Methods

Standardized mortality ratios (SMR) of total and site-specific causes of death were calculated for 579 patients with MM (McKee-Farrar) and 1585 patients with MP (Brunswik, Lubinus) THA for primary osteoarthritis.

Results

Mean follow-up time was 17.9 years for patients with MM and 16.7 years for patients with MP. Overall SMR was 0.95 for the MM cohort and 0.90 for the MP cohort, as compared to the normal population. Both cohorts showed significantly decreased mortality for the first decade postoperatively, equal mortality over the next 10 years, and significantly increased mortality after 20 years. Patients with MM THA had higher cancer mortality (SMR 1.01) than those with MP THA (SMR 0.66) during the first 20 years postoperatively, but not thereafter.

Conclusion

Both MM and MP prostheses are safe based on total and site-specific mortality of recipients during the first 20 postoperative years in comparison with the general population.

Nanoparticles can cause DNA damage across a cellular barrier

The increasing use of nanoparticles in medicine has raised concerns over their ability to gain access to privileged sites in the body. Here, we show that cobalt-chromium nanoparticles (29.5 +/- 6.3 nm in diameter) can damage human fibroblast cells across an intact cellular barrier without having to cross the barrier. The damage is mediated by a novel mechanism involving transmission of purine nucleotides (such as ATP) and intercellular signalling within the barrier through connexin gap junctions or hemichannels and pannexin channels. The outcome, which includes DNA damage without significant cell death, is different from that observed in cells subjected to direct exposure to nanoparticles. Our results suggest the importance of indirect effects when evaluating the safety of nanoparticles. The potential damage to tissues located behind cellular barriers needs to be considered when using nanoparticles for targeting diseased states.

ERCC1 expression in aseptic loosening after total hip replacement

Particle-induced osteolysis is a major cause of aseptic loosening after total joint replacement. The purpose of the current study was to evaluate the DNA damage repair capacity of macrophages in patients with aseptic hip loosening by determination of ERCC1. Moreover, we wanted to elucidate if the potency of the DNA-repair mechanisms correlates with the survival of joint implants. For this purpose we compared the immunohistochemical ERCC1 expression in capsules and interface membranes of patients with loosening of a hip replacement in the first 10 years after implantation with those in patients with late loosening. In analogy with ERCC1 studies on cancer in humans we calculated the semi-quantitative H-score by multiplying the staining intensity with the proportion score of positive stained macrophages. The level of ERCC1 reaction in the specimens taken from patients with early aseptic loosening (mean H-score 0.57) was clearly lower in comparison with those from patients undergoing exchange hip arthroplasty later than 10 years after surgery (mean H-score 2.24). We determined an H-score for ERCC1 expression of 1 as a cutoff point giving a sensitivity and specificity of 100% for identification of early aseptic loosening after less than 10 years. In summary, lower levels of ERCC1 were found in patients with early aseptic loosening compared to patients with aseptic loosening later than 10 years.

Age-related impairments of mobility associated with cobalt and other heavy metals: data from NHANES 1999-2004

Exposure to heavy metals promotes oxidative stress and damage to cellular components, and may accelerate age-related disease and disability. Physical mobility is a validated biomarker of age-related disability and is predictive of hospitalization and mortality. Our study examined associations between selected heavy metals and impaired lower limb mobility in a representative older human population. Data for 1615 adults aged >or=60 yr from the National Health and Nutrition Examination Survey (NHANES) 1999 to 2004 were used to identify associations between urinary concentrations of 10 metals with self-reported and measured significant walking impairments. Models were adjusted for confounding factors, including smoking. In models adjusted for age, gender, and ethnicity, elevated levels of cadmium, cobalt, and uranium were associated with impairment of the ability to walk a quarter mile. In fully adjusted models, cobalt was the only metal that remained associated: the odds ratio (OR) for reporting walking problems with a 1-unit increase in logged cobalt concentration (mug/L) was 1.43 (95% CI 1.12 to 1.84). Cobalt was also the only metal associated with a significant increased measured time to walk a 20-ft course. In analyses of disease categories to explain the mobility finding, cobalt was associated with physician diagnosed arthritis (1-unit increase OR = 1.22 (95% CI 1.00 to 1.49). Low-level cobalt exposure, assessed through urinary concentrations of this essential heavy metal, may be a risk factor for age-related physical impairments. Independent replication is needed to confirm this association.