Showing papers by "Exponent published in 2015"

Comparative Epidemiology of Revision Arthroplasty: Failed THA Poses Greater Clinical and Economic Burdens Than Failed TKA.

Abstract: Background Revision THA and TKA are growing and important clinical and economic challenges. Healthcare systems tend to combine revision joint replacement procedures into a single service line, and differences between revision THA and revision TKA remain incompletely characterized. These differences carry implications for guiding care and resource allocation. We therefore evaluated epidemiologic trends associated with revision THAs and TKAs.

Quantifying the Burden of Revision Total Joint Arthroplasty for Periprosthetic Infection

Abstract: Periprosthetic joint infection (PJI) represents substantial clinical and economic burdens. This study evaluated patient and procedure characteristics and resource utilization associated with revision arthroplasty for PJI. The Nationwide Inpatient Sample (Q4 2005-2010) was analyzed for 235,857 revision THA (RTHA) and 301,718 revision TKA (RTKA) procedures. PJI was the most common indication for RTKA, and the third most common reason for RTHA. PJI was most commonly associated with major severity of illness (SOI) in RTHA, and with moderate SOI in RTKA. RTHA and RTKA for PJI had the longest length of stay. Costs were higher for RTHA/RTKA for PJI than for any other diagnosis except periprosthetic fracture. Epidemiologic differences exist in the rank, severity and populations for RTHA and RTKA for PJI.

Database and Registry Research in Orthopaedic Surgery: Part I: Claims-Based Data.

Abstract: The use of large-scale national databases for observational research in orthopaedic surgery has grown substantially in the last decade, and the data sets can be grossly categorized as either administrative claims or clinical registries. Administrative claims data comprise the billing records associated with the delivery of health-care services. Orthopaedic researchers have used both government and private claims to describe temporal trends, geographic variation, disparities, complications, outcomes, and resource utilization associated with both musculoskeletal disease and treatment. Medicare claims comprise one of the most robust data sets used to perform orthopaedic research, with >45 million beneficiaries. The U.S. government, through the Centers for Medicare & Medicaid Services, often uses these data to drive changes in health policy. Private claims data used in orthopaedic research often comprise more heterogeneous patient demographic samples, but allow longitudinal analysis similar to that offered by Medicare claims. Discharge databases, such as the U.S. National Inpatient Sample, provide a wide national sampling of inpatient hospital stays from all payers and allow analysis of associated adverse events and resource utilization. Administrative claims data benefit from the high patient numbers obtained through a majority of hospitals. Using claims, it is possible to follow patients longitudinally throughout encounters irrespective of the location of the institution delivering health care. Some disadvantages include lack of precision of ICD-9 (International Classification of Diseases, Ninth Revision) coding schemes. Much of these data are expensive to purchase, complicated to organize, and labor-intensive to manipulate--often requiring trained specialists for analysis. Given the changing health-care environment, it is likely that databases will provide valuable information that has the potential to influence clinical practice improvement and health policy for years to come.

Analysis of heritability and shared heritability based on genome-wide association studies for thirteen cancer types

Abstract: Background: Studies of related individuals have consistently demonstrated notable familial aggregation of cancer. We aim to estimate the heritability and genetic correlation attributable to the add ...

Direct in vivo inflammatory cell-induced corrosion of CoCrMo alloy orthopedic implant surfaces

Abstract: Cobalt-chromium-molybdenum (CoCrMo) alloy, used for over five decades in orthopedic implants, may corrode and release wear debris into the body during use These degradation products may stimulate immune and inflammatory responses in vivo We report here on evidence of direct inflammatory cell-induced corrosion of human implanted and retrieved CoCrMo implant surfaces Corrosion morphology on CoCrMo implant surfaces, in unique and characteristic patterns, and the presence of cellular remnants and biological materials intimately entwined with the corrosion indicates direct cellular attack under the cell membrane region of adhered and/or migrating inflammatory cells Evidence supports a Fenton-like reaction mechanism driving corrosion in which reactive oxygen species are the major driver of corrosion Using in vitro tests, large increases in corrosion susceptibility of CoCrMo were seen (40-100 fold) when immersed in phosphate buffered saline solutions modified with hydrogen peroxide and hydrochloric acid to represent the chemistry under inflammatory cells This discovery raises significant new questions about the clinical consequences of such corrosion interactions, the role of patient inflammatory reactions, and the detailed mechanisms at play

Modelling of cracks developed in lithium-ion cells under mechanical loading

Abstract: This research reports on an experimental and numerical study of material failure in the electrode assemblies (i.e. “jelly roll” and/or “electrode stack”) of lithium-ion batteries after local mechanical loading. Deformed cylindrical and pouch cells (i.e. lithium-ion polymer cells) were subjected to X-ray computed tomography (CT scanning) to detect location, size, and orientation of cracks that developed in the electrode assemblies at onset of short-circuit. An experimental program was completed to acquire properties of electrode–separator micro components of electrode assemblies in tension. This data was used for calibration of an anisotropic material model. Finite element models were developed for both cell types and a maximum strain criteria was used for element failure and deletion at short circuit. The models developed here predict the location of cracks in both pouch and cylindrical cells. The finite element models corroborated the CT scan regarding location and orientation of cracks formed in the electrode assemblies. In both pouch and cylindrical cells, cracks were found to initiate perpendicular to the transverse direction of the separator.

Database and Registry Research in Orthopaedic Surgery: Part 2: Clinical Registry Data.

Abstract: The use of large-scale national databases for observational research in orthopaedic surgery has grown substantially in the last decade, and the data sets can be categorized as either administrative claims or clinical registries. Clinical registries contain secondary data on patients with a specific diagnosis or procedure. The data are typically used for patient outcome surveillance to improve patient safety and health-care quality. Registries used in orthopaedic research exist at the regional, national, and international levels, and many were designed to specifically collect outcomes relevant to orthopaedics, such as short-term surgical complications, longer-term outcomes (implant survival or reoperations), and patient-reported outcomes. Although heterogeneous, clinical registries-in contrast to claims data-typically have a more robust list of variables, with relatively precise prospective data input, management infrastructure, and reporting systems. Some weaknesses of clinical registries include a smaller number of patients, inconstant follow-up duration, and use of sampling methods that may limit generalizability. Within the U.S., national joint registry adoption has lagged international joint registries. Given the changing health-care environment, it is likely that clinical registries will provide valuable information that has the potential to influence clinical practice improvement and health-care policy in the future.

Morbidity and Mortality After Vertebral Fractures: Comparison of Vertebral Augmentation and Nonoperative Management in the Medicare Population.

Abstract: STUDY DESIGN Vertebral compression fracture (VCF) patients in the 100% US Medicare data set (2005-2009). OBJECTIVE To compare the mortality and morbidity risks for VCF patients undergoing conservative treatment (nonoperated), balloon kyphoplasty (BKP), and vertebroplasty (VP). SUMMARY OF BACKGROUND DATA Studies have reported lower mortality risk for BKP or VP cohorts than nonoperated cohorts, but it is uncertain whether there are any differences in morbidity risks. METHODS Survival and morbidity was estimated by the Kaplan-Meier method, and the differences in outcomes were assessed by Cox regression between BKP, VP, and nonoperated cohorts. A propensity matching analysis was used to account for potential bias. RESULTS A total of 1,038,956 VCF patients were identified, including 141,343 BKP patients and 75,364 VP patients. The nonoperated cohort was found to have a 55% higher adjusted risk of mortality (P < 0.001) than the BKP cohort and 25% higher adjusted risk of mortality (P < 0.001) than the VP cohort. The BKP cohort was also found to have a 19% lower adjusted risk of mortality (P < 0.001) than the VP cohort. The findings were similar for mortality with pneumonia diagnosed in the 90 days before death and also after propensity matching, as well as for subgroups of osteoporotic VCF patients, including those who survived at least 1 year and those with no cancer diagnosis. With propensity matching, the nonoperated cohort had significantly higher adjusted risks of pneumonia, myocardial infarction/cardiac complications, DVT, and urinary tract infection than the BKP cohort but lower adjusted risks of subsequent augmentation/fusion, subsequent augmentation, and pulmonary/respiratory complications. The BKP cohort also had significantly lower risks of morbidity than the VP cohort, except for deep venous thrombosis (DVT), infection, and myocardial infarction/cardiac complications, which were similar between both cohorts. CONCLUSION VCF patients in the Medicare population who received vertebral augmentation therapies, specifically BKP and VP, experienced lower mortality and overall morbidity than VCF patients who received conservative management. LEVEL OF EVIDENCE 3.

Recent developments in multiplexing techniques for immunohistochemistry.

Abstract: Methods to detect immunolabeled molecules at increasingly higher resolutions, even when present at low levels, are revolutionizing immunohistochemistry (IHC). These technologies can be valuable for the management and examination of rare patient tissue specimens, and for improved accuracy of early disease detection. The purpose of this article is to highlight recent multiplexing methods that are candidates for more prevalent use in clinical research and potential translation to the clinic. Multiplex IHC methods, which permit identification of at least 3 and up to 30 discrete antigens, have been divided into whole-section staining and spatially-patterned staining categories. Associated signal enhancement technologies that can enhance performance and throughput of multiplex IHC assays are also discussed. Each multiplex IHC technique, detailed herein, is associated with several advantages as well as tradeoffs that must be taken into consideration for proper evaluation and use of the methods.

World Health Organization estimates of the global and regional disease burden of four foodborne chemical toxins, 2010: a data synthesis.

Abstract: Background Chemical exposures have been associated with a variety of health effects; however, little is known about the global disease burden from foodborne chemicals. Food can be a major pathway for the general population's exposure to chemicals, and for some chemicals, it accounts for almost 100% of exposure. Methods and Findings Groups of foodborne chemicals, both natural and anthropogenic, were evaluated for their ability to contribute to the burden of disease. The results of the analyses on four chemicals are presented here - cyanide in cassava, peanut allergen, aflatoxin, and dioxin. Systematic reviews of the literature were conducted to develop age- and sex-specific disease incidence and mortality estimates due to these chemicals. From these estimates, the numbers of cases, deaths and disability adjusted life years (DALYs) were calculated. For these four chemicals combined, the total number of illnesses, deaths, and DALYs in 2010 is estimated to be 339,000 (95% uncertainty interval [UI]: 186,000-1,239,000); 20,000 (95% UI: 8,000-52,000); and 1,012,000 (95% UI: 562,000-2,822,000), respectively. Both cyanide in cassava and aflatoxin are associated with diseases with high case-fatality ratios. Virtually all human exposure to these four chemicals is through the food supply. Conclusion Chemicals in the food supply, as evidenced by the results for only four chemicals, can have a significant impact on the global burden of disease. The case-fatality rates for these four chemicals range from low (e.g., peanut allergen) to extremely high (aflatoxin and liver cancer). The effects associated with these four chemicals are neurologic (cyanide in cassava), cancer (aflatoxin), allergic response (peanut allergen), endocrine (dioxin), and reproductive (dioxin).

Prevalence and Costs of Rehabilitation and Physical Therapy After Primary TJA.

Abstract: This study evaluated the trends in discharge patterns and the prevalence and cost of post-discharge PT. The 5% Medicare database (1997-2010) was used to identify 50,886 primary THA and 107,675 TKA patients. More than 50% of patients were discharged from hospital to an inpatient facility. There were an increase in discharges to skilled nursing units and a reduced rate to rehabilitation facilities. In contrast to hospital, surgeon reimbursement, and implant costs, the average annual PT cost per patient rose through the study period. Approximately 25% of PT costs were used on less common modalities. PT costs more than $648 million a year. With the increased pressure to control costs for primary TJA, these patterns may change unless PT effectiveness can be demonstrated.

The economic significance of orthopaedic infections.

Abstract: Musculoskeletal infections are a leading cause of patient morbidity and rising healthcare expenditures. The incidence of musculoskeletal infections, including soft-tissue infections, periprosthetic joint infection, and osteomyelitis, is increasing. Cases involving both drug-resistant bacterial strains and periprosthetic joint infection in total hip and total knee arthroplasty are particularly costly and represent a growing economic burden for the American healthcare system. With the institution of the Affordable Care Act, there has been an increasing drive in the United States toward rewarding healthcare organizations for their quality of care, bundling episodes of care, and capitating approaches to managing populations. In current reimbursement models, complications following the index event, including infection, are not typically reimbursed, placing the burden of caring for infections on the physician, hospital, or accountable care organization. Without the ability to risk-stratify patient outcomes based on patient comorbidities that are associated with a higher incidence of musculoskeletal infection, healthcare organizations are disincentivized to care for moderate- to high-risk patients. Reducing the cost of treating musculoskeletal infection also depends on incentivizing innovations in infection prevention.

Integrating health and safety in the workplace: how closely aligning health and safety strategies can yield measurable benefits

Abstract: Objective To better understand how integrating health and safety strategies in the workplace has evolved and establish a replicable, scalable framework for advancing the concept with a system of health and safety metrics, modeled after the Dow Jones Sustainability Index. Methods Seven leading national and international programs aimed at creating a culture of health and safety in the workplace were compared and contrasted. Results A list of forty variables was selected, making it clear there is a wide variety of approaches to integration of health and safety in the workplace. Conclusion Depending on how well developed the culture of health and safety is within a company, there are unique routes to operationalize and institutionalize the integration of health and safety strategies to achieve measurable benefits to enhance the overall health and well-being of workers, their families, and the community.

Seismic Response of a Damage-Resistant Recentering Posttensioned-HYFRC Bridge Column

Abstract: This paper presents the shake-table tests of a damage-resistant posttensioned bridge column designed to rock at the interface with its foundation. It compares the response to that of a conventional bridge column detailed to conform with current California seismic design criteria. The lower portion of the rocking column was built using hybrid fiber-reinforced concrete (HYFRC) and was armored with headed rebars; these features enhanced the compression damage resistance at the column base. Unbonded rebars that crossed the rocking plane provided hysteretic energy dissipation. Both columns were subjected to a sequence of scaled historical triaxial earthquake ground motions including near-fault pulse-like motions. The conventional column formed a flexural plastic hinge with extensive spalling. It accumulated a 6.8% residual drift ratio after a sequence of seven ground motions, which caused a peak drift ratio of 10.8%. The posttensioned-HYFRC column sustained only light damage and accumulated only a 0.4%...

Dislocation Rates Following Primary Total Hip Arthroplasty Have Plateaued in the Medicare Population

Abstract: The purpose of this study was to determine if the use of larger femoral head diameters, in combination with recent practice including enhanced soft tissue choices and various operative exposure choices has led to any further decline in dislocation rates. 51,901 patients undergoing primary THA were identified from 5% Medicare Part B (physician/carrier) claims between January 1, 1997 and December 31, 2011. Dislocation rate at 6 months following THA was 2.84% over the study period (1997-2011). From 2005 to 2011, dislocation rates following primary THA have plateaued in the United States at approximately 2%. This suggests that the full benefits using large femoral head sizes are now realized. For further improvement in dislocation rates, a greater emphasis will be required on patient selection, surgical technique and component alignment.

The complexity of biomechanics causing primary blast-induced traumatic brain injury: a review of potential mechanisms

Abstract: Primary blast-induced traumatic brain injury (bTBI) is a prevalent battlefield injury in recent conflicts, yet biomechanical mechanisms of bTBI remain unclear. Elucidating specific biomechanical mechanisms is essential to developing animal models for testing candidate therapies and for improving protective equipment. Three hypothetical mechanisms of primary bTBI have received the most attention. Because translational and rotational head accelerations are primary contributors to TBI from non-penetrating blunt force head trauma, the acceleration hypothesis suggests that blast-induced head accelerations may cause bTBI. The hypothesis of direct cranial transmission suggests that a pressure transient traverses the skull into the brain and directly injures brain tissue. The thoracic hypothesis of bTBI suggests that some combination of a pressure transient reaching the brain via the thorax and a vagally mediated reflex result in bTBI. These three mechanisms may not be mutually exclusive, and quantifying exposure thresholds (for blasts of a given duration) is essential for determining which mechanisms may be contributing for a level of blast exposure. Progress has been hindered by experimental designs, which do not effectively expose animal models to a single mechanism and by over-reliance on poorly validated computational models. The path forward should be predictive validation of computational models by quantitative confirmation with blast experiments in animal models, human cadavers, and biofidelic human surrogates over a range of relevant blast magnitudes and durations coupled with experimental designs, which isolate a single injury mechanism.

Metal-on-conventional Polyethylene Total Hip Arthroplasty Bearing Surfaces Have a Higher Risk of Revision Than Metal-on-highly Crosslinked Polyethylene: Results From a US Registry

Abstract: Background Although studies have reported lower radiological wear in highly crosslinked polyethylene (HXLPE) versus conventional polyethylene in total hip arthroplasty (THA), there is limited clinical evidence on the risk of revision of these polyethylene THA bearing surfaces.

Early twentieth-century warming linked to tropical Pacific wind strength

Abstract: Global temperatures rose quickly between 1910 and 1940. A reconstruction based on corals suggests that the Pacific trade winds were weak during this period of rapid warming, but strengthened as warming slowed in the following decades.

A review of epidemiologic studies of low-level exposures to organophosphorus insecticides in non-occupational populations.

Abstract: This paper systematically reviews epidemiologic studies related to low-level non-occupational exposures to organophosphorus (OP) insecticides. Many of the studies evaluate levels of maternal OP metabolites and subsequent health outcomes in offspring. The studies focused primarily on birth outcomes (e.g., infant body weight or head circumference) and neurodevelopmental (e.g., mental and psychomotor) testing results. The evidence from these studies was reviewed under the Bradford Hill guidelines. Most of the studies assessing exposure based on urinary levels of OP insecticide metabolites used only one or two measurements during pregnancy. The potential for exposure misclassification with this method is largely due to (1) preformed metabolites that are ingested with food, (2) the short elimination half-life of OP insecticides, and (3) lack of specificity to particular OP insecticides for many of the metabolites. For birth outcomes, the majority of reported results are not statistically significant, and the associations are inconsistent within and across studies. There is more within-study consistency for some of the neurodevelopmental testing results, although few associations were examined across several studies. These associations are generally weak, have been replicated only to a limited extent, and require further confirmation before they can be considered established. The OP insecticide levels measured in the epidemiologic studies are too low to cause biologically meaningful acetylcholinesterase inhibition, the most widely used metric for OP insecticide toxicity. Overall, the available evidence does not establish that low-level exposures to OP insecticides cause adverse birth outcomes or neurodevelopmental problems in humans.

A Low-Rank Matrix Approach for the Analysis of Large Amounts of Power System Synchrophasor Data

Abstract: With the installation of many new multi-channel phasor measurement units (PMUs), utilities and power grid operators are collecting an unprecedented amount of high-sampling rate bus frequency, bus voltage phasor, and line current phasor data with accurate time stamps. The data owners are interested in efficient algorithms to process and extract as much information as possible from such data for real-time and off-line analysis. Traditional data analysis typically analyze one channel of PMU data at a time, and then combine the results from the individual analysis to arrive at some conclusions. In this paper, a spatial-temporal framework for efficient processing of blocks of PMU data is proposed. A key property of these PMU data matrices is that they are low rank. Using this property, various data management issues such as data compression, missing data recovery, data substitution detection, and disturbance triggering and location can be processing using singular-value based algorithms and convex programming. These functions are illustrated using some historical data from the Central New York power system.

Relationships between p53 status, apoptosis and induction of micronuclei in different human and mouse cell lines in vitro: Implications for improving existing assays.

Abstract: Accumulated evidence has shown that in vitro mammalian cell genotoxicity assays produce high frequencies of “misleading” positive results, i.e. predicted hazard is not confirmed in in vivo and/or carcinogenicity studies [1], raising the question of relevance to human risk assessment. A recent study of micronucleus (MN) induction [2] showed that commonly used p53-deficient rodent cell lines (CHL, CHO and V79) gave a higher frequency of “misleading” positive results with 9 non-DNA reactive, Ames-negative and in vivo negative chemicals [3] than human p53-competent cells (blood lymphocytes, TK6 and HepG2 cell lines). This raised the question of whether these differences were due to p53 status or species origin. This present study compared human versus mouse and p53-competent versus p53-mutated function. The same 9 chemicals were tested for induction of MN in mouse lymphoma L5178Y (mutated p53), human TK6 (functional p53) and WIL2-NS (TK6 related, with mutated p53) cells. Six chemicals provided clear positive increases in MN frequency in at least one cell type. L5178Y cells yielded clear positive responses with more chemicals than either TK6 or WIL2-NS, indicating origin rather than p53 functionality was most relevant. Apoptosis induction (measured via caspase-3/7) was also investigated with clear differences in the timing and extent of apoptosis induction between mouse and human cells noted. With curcumin in TK6 cells, induction of caspase-3/7 activity coincided with MN induction, whereas for L5178Y cells, MN induction occurred in the absence of increased caspase activity. By contrast, with MMS in TK6 cells, MN induction preceded increased caspase-3/7 activity. These data suggest that MN induction by “misleading positive” genotoxins in p53-competent human cell lines may result from apoptosis, whereas in p53-defective rodent cells such as L5178Y, MN induction may be independent of apoptosis.

Review of cobalt toxicokinetics following oral dosing: Implications for health risk assessments and metal-on-metal hip implant patients

Abstract: Cobalt (Co) can stimulate erythropoietin production in individuals at doses exceeding 25 mg CoCl2/day. Co has also been shown to exert effects on the thyroid gland, heart and nervous system at sufficient doses. The biological activity of Co is dictated by the concentration of free (unbound) ionic Co(2+). Blood concentrations, as well as, urinary excretion rates of Co are reliable biomarkers for systemic Co exposure. A recent series of human volunteer Co-supplement studies simultaneously measured Co blood and urine concentrations, as well as, Co speciation in serum, and a number of biochemical and clinical parameters. It was found in these studies that peak Co whole blood concentration as high as 117 μg/L were not associated with changes in hematological parameters such as increased red blood cell (RBC) count, hemoglobin (Hgb) or hematocrit (Hct) levels, nor with changes in cardiac, neurological or, thyroid function. Using a Co biokinetic model, the estimated Co systemic tissue concentrations (e.g., liver, kidney, and heart) following 90-days of Co-dietary supplementation with ∼1 mg Co/day were found to be similar to estimated tissue concentrations in implant patients after 10 years of exposure at continuous steady state Co blood concentration of ∼10 μg/L. This study is the first to present modeled Co tissue concentrations at various doses following sub-chronic and chronic exposure. The modeled steady state tissue Co concentrations in combination with the data on adverse health effects in humans should help in the characterization of potential hazards associated with increased blood Co concentrations due to exposure to dietary supplements or cobalt-chromium (Co-Cr) containing implants.

New biomaterials for orthopedic implants

Abstract: License. The full terms of the License are available at http://creativecommons.org/licenses/by-nc/3.0/. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. Permissions beyond the scope of the License are administered by Dove Medical Press Limited. Information on how to request permission may be found at: http://www.dovepress.com/permissions.php Orthopedic Research and Reviews 2015:7 107–130 Orthopedic Research and Reviews Dovepress