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Kurtz S.M.,Exponent, Inc. | Ong K.L.,Exponent, Inc. | Lau E.,Exponent, Inc. | Bozic K.J.,University of California at San Francisco
Journal of Bone and Joint Surgery - American Volume | Year: 2014

Background: Few studies have explored the role of the National Health Expenditure and macroeconomics on the utilization of total joint replacement. The economic downturn has raised questions about the sustainability of growth for total joint replacement in the future. Previous projections of total joint replacement demand in the United States were based on data up to 2003 using a statistical methodology that neglected macroeconomic factors, such as the National Health Expenditure. Methods: Data from the Nationwide Inpatient Sample (1993 to 2010) were used with United States Census and National Health Expenditure data to quantify historical trends in total joint replacement rates, including the two economic downturns in the 2000s. Primary and revision hip and knee arthroplasty were identified using codes from the International Classification of Diseases, Ninth Revision, Clinical Modification. Projections in total joint replacement were estimated using a regression model incorporating the growth in population and rate of arthroplasties from 1993 to 2010 as a function of age, sex, race, and census region using the National Health Expenditure as the independent variable. The regression model was used in conjunction with government projections of National Health Expenditure from 2011 to 2021 to estimate future arthroplasty rates in subpopulations of the United States and to derive national estimates. Results: The growth trend for the incidence of joint arthroplasty, for the overall United States population as well as for the United States workforce, was insensitive to economic downturns. From2009 to 2010, the total number of procedures increased by 6.0% for primary total hip arthroplasty, 6.1% for primary total knee arthroplasty, 10.8% for revision total hip arthroplasty, and 13.5% for revision total knee arthroplasty. The National Health Expenditure model projections for primary hip replacement in 2020 were higher than a previously projected model, whereas the current model estimates for total knee arthroplasty were lower. Conclusions: Economic downturns in the 2000s did not substantially influence the national growth trends for hip and knee arthroplasty in the United States. These latest updated projections provide a basis for surgeons, hospitals, payers, and policy makers to plan for the future demand for total joint replacement surgery. Copyright © 2014 by The Journal of Bone and Joint Surgery, Incorporated.

Pound B.G.,Exponent, Inc.
Journal of Biomedical Materials Research - Part A | Year: 2014

The metallic materials used for implantable medical devices are predominantly stainless steels, Ti and its alloys, and Co-Cr alloys. The corrosion resistance of each of these materials is associated with a passive oxide film on its surface. Since corrosion resistance is crucial to implant performance, considerable effort has been focused on understanding the nature of the passive film present under physiological conditions. Surface analytical techniques and electrochemical impedance spectroscopy have been used in a number of studies to investigate the passive film formed on metallic biomaterials in simulated physiological solutions. This review focuses on the surface characteristics of these materials with regard to composition, thickness, and impedance of the passive films. Of particular interest are changes in the films with surface treatment and the nature of the films developed over time in the simulated solutions. © 2013 Wiley Periodicals, Inc.

Lovald S.,Exponent, Inc.
Journal of surgical orthopaedic advances | Year: 2014

The purpose of the current study is to identify patients who are at high risk for rehospitalization, revision, complications, and mortality after outpatient and short-stay total knee arthroplasty (TKA). The Medicare 5% limited data set sample was used to identify patients with a TKA procedure who were treated in an outpatient setting or who were discharged within 1 or 2 days in the hospital setting. Rehospitalization risk increased with higher Charlson score (i.e., poorer health status), older patients, inpatients (vs. outpatients), patients not receiving a femoral nerve block, earlier (vs. recent) year of surgery, and those with a recent history of heart failure. The findings of this study suggest that existing comorbidities, particularly heart failure, have the greatest effect on event risk after outpatient and short-stay TKA. The information obtained from this study should assist with patient selection for TKA performed on an outpatient basis.

The use of metallic materials for implantable medical devices has prompted numerous studies aimed at characterizing the corrosion susceptibility of these materials and understanding their electrochemical behavior in simulated and actual physiological liquids. This review focuses on the forms of corrosion that are of principal interest for Ti and its alloys in vivo: general corrosion, pitting corrosion, crevice corrosion, galvanic corrosion, and fretting corrosion. It also addresses environmentally assisted cracking in the form of hydrogen embrittlement. Of particular interest is the susceptibility of Ti and its alloys to the different forms of corrosion with regard to both solution chemistry, especially the effect of organic species, and surface characteristics such as oxide composition, surface inclusions, and wear/fretting.

Alexander D.D.,Exponent, Inc. | Cushing C.A.,Exponent, Inc.
Obesity Reviews | Year: 2011

Meat consumption and cancer has been evaluated in hundreds of epidemiologic studies over the past three decades; however, the possible role of this food group on carcinogenesis is equivocal. In this comprehensive review, the currently available epidemiologic prospective studies of red meat intake and colorectal cancer are summarized to provide a greater understanding of any potential relationships. Specifically, salient demographic, methodological and analytical information is synthesized across 35 prospective studies. Collectively, associations between red meat consumption and colorectal cancer are generally weak in magnitude, with most relative risks below 1.50 and not statistically significant, and there is a lack of a clear dose-response trend. Results are variable by anatomic tumour site (colon vs. rectum) and by gender, as the epidemiologic data are not indicative of a positive association among women while most associations are weakly elevated among men. Colinearity between red meat intake and other dietary factors (e.g. Western lifestyle, high intake of refined sugars and alcohol, low intake of fruits, vegetables and fibre) and behavioural factors (e.g. low physical activity, high smoking prevalence, high body mass index) limit the ability to analytically isolate the independent effects of red meat consumption. Because of these factors, the currently available epidemiologic evidence is not sufficient to support an independent positive association between red meat consumption and colorectal cancer. © 2010 The Authors. obesity reviews © 2010 International Association for the Study of Obesity.

Miller P.E.,Exponent, Inc. | Perez V.,Exponent, Inc.
American Journal of Clinical Nutrition | Year: 2014

Background: Replacement of caloric sweeteners with lower- or nocalorie alternatives may facilitate weight loss or weight maintenance by helping to reduce energy intake; however, past research examining low-calorie sweeteners (LCSs) and body weight has produced mixed results. Objective: The objective was to systematically review and quantitatively evaluate randomized controlled trials (RCTs) and prospective cohort studies, separately, that examined the relation between LCSs and body weight and composition. Design: A systematic literature search identified 15 RCTs and 9 prospective cohort studies that examined LCSs from foods or beverages or LCSs consumed as tabletop sweeteners. Meta-analyses generated weighted mean differences in body weight and composition values between the LCS and control groups among RCTs and weighted mean correlations for LCS intake and these parameters among prospective cohort studies. Results: In RCTs, LCSs modestly but significantly reduced all outcomes examined, including body weight (-0.80 kg; 95% CI: -1.17, -0.43), body mass index [BMI (in kg/m2): -0.24; 95% CI: -0.41, -0.07], fat mass (-1.10 kg; 95% CI: -1.77, -0.44), and waist circumference (-0.83 cm; 95% CI: -1.29, -0.37). Among prospective cohort studies, LCS intake was not associated with body weight or fat mass, but was significantly associated with slightly higher BMI (0.03; 95% CI: 0.01, 0.06). Conclusions: The current meta-analysis provides a rigorous evaluation of the scientific evidence on LCSs and body weight and composition. Findings from observational studies showed no association between LCS intake and body weight or fat mass and a small positive association with BMI; however, data from RCTs, which provide the highest quality of evidence for examining the potentially causal effects of LCS intake, indicate that substituting LCS options for their regular-calorie versions results in a modest weight loss and may be a useful dietary tool to improve compliance with weight loss or weight maintenance plans. © 2014 American Society for Nutrition.

Seven current contending cancer theories consider different sets of critical events as sufficient for tumorigenesis. These theories, most recently the microRNA dysregulation (MRD) theory, have overlapping attributes and extensive empirical support, but also some discrepancies, and some do not address both benign and malignant tumorigenesis. By definition, the most efficient tumorigenic pathways will dominate under conditions that selectively activate those pathways. The MRD theory provides a mechanistic basis to combine elements of the current theories into a new hypothesis that: (i) tumors arise most efficiently under stress that induces and sustains either protective or regenerative states of adaptive hyperplasia (AH) that normally are epigenetically maintained unless terminated; and (ii) if dysregulated by a somatic mutation that prevents normal termination, these two AH states can generate benign and malignant tumors, respectively. This hypothesis, but not multistage cancer theory, predicts that key participating AH-stem-cell populations expand markedly when triggered by stress, particularly chronic metabolic or oxidative stress, mechanical irritation, toxic exposure, wounding, inflammation, and/or infection. This hypothesis predicts that microRNA expression patterns in benign vs. malignant tumor tissue will correlate best with those governing protective vs. regenerative AH in that tissue, and that tumors arise most efficiently inmutagen-exposed stem cells that either happen to be in, or incidentally later become recruited into, an AH state. © 2012 Elsevier Ltd.

O'Reilly K.T.,Exponent, Inc.
Integrated environmental assessment and management | Year: 2014

A realistic understanding of contaminant sources is required to set appropriate control policy. Forensic chemical methods can be powerful tools in source characterization and identification, but they require a multiple-lines-of-evidence approach. Atmospheric receptor models, such as the US Environmental Protection Agency (USEPA)'s chemical mass balance (CMB), are increasingly being used to evaluate sources of pyrogenic polycyclic aromatic hydrocarbons (PAHs) in sediments. This paper describes the assumptions underlying receptor models and discusses challenges in complying with these assumptions in practice. Given the variability within, and the similarity among, pyrogenic PAH source types, model outputs are sensitive to specific inputs, and parsing among some source types may not be possible. Although still useful for identifying potential sources, the technical specialist applying these methods must describe both the results and their inherent uncertainties in a way that is understandable to nontechnical policy makers. The authors present an example case study concerning an investigation of a class of parking-lot sealers as a significant source of PAHs in urban sediment. Principal component analysis is used to evaluate published CMB model inputs and outputs. Targeted analyses of 2 areas where bans have been implemented are included. The results do not support the claim that parking-lot sealers are a significant source of PAHs in urban sediments. © 2013 SETAC.

O'Reilly K.,Exponent, Inc.
Environmental Pollution | Year: 2014

The claim made in the title of Witter et al. (2014) "Coal-tar-based sealcoated pavement: A major PAH source to urban stream sediments" is not supported by the data presented. The author's use of Pearson correlation coefficients is insufficient to indicate causation. The application of spatial analysis and principle component analysis did not include sealer specific inputs, so provides no basis for the claim. To test the hypothesis that sealers are a source of PAHs in the stream studied, EPA's Chemical Mass Balance (CMB) source evaluation model was applied to Witter's sediment data. CMB found an excellent fit (R2 > 0.999) between measured and modeled PAH concentrations when sealers were not included as a potential source. This finding does not support Witter et al. (2014) claim that sealers are a major source of PAHs. © 2013 Elsevier Ltd. All rights reserved.

News Article | February 15, 2017

MENLO PARK, Calif., Feb. 15, 2017 (GLOBE NEWSWIRE) -- Exponent, Inc. (NASDAQ:EXPO), today announced that members of the senior management team will present to the investment community and host one-on-one meetings at the following investor conference: Cantor Fitzgerald’s 4th Annual Internet & Technology Services Conference Date: Thursday, February 23, 2017 Time: 3:35 pm ET Format: Presentation and 1x1/Small Investor Group Meetings Location: Le Parker Meridien, New York, NY A webcast of the presentation will be accessible on the investor relations section of the Exponent website. An archived replay of the webcast will be available following the live event. Exponent is an engineering and scientific consulting firm providing solutions to complex problems. Exponent's multidisciplinary organization of scientists, physicians, engineers, and business consultants brings together more than 90 technical disciplines to address complicated issues facing industry and government today. The firm has been best known for analyzing accidents and failures to determine their causes, but in recent years it has become more active in assisting clients with human health, environmental and engineering issues associated with new products to help prevent problems in the future.

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