Fionna Mowat

Projections of Primary and Revision Hip and Knee Arthroplasty in the United States from 2005 to 2030

BACKGROUND Over the past decade, there has been an increase in the number of revision total hip and knee arthroplasties performed in the United States. The purpose of this study was to formulate projections for the number of primary and revision total hip and knee arthroplasties that will be performed in the United States through 2030. METHODS The Nationwide Inpatient Sample (1990 to 2003) was used in conjunction with United States Census Bureau data to quantify primary and revision arthroplasty rates as a function of age, gender, race and/or ethnicity, and census region. Projections were performed with use of Poisson regression on historical procedure rates in combination with population projections from 2005 to 2030. RESULTS By 2030, the demand for primary total hip arthroplasties is estimated to grow by 174% to 572,000. The demand for primary total knee arthroplasties is projected to grow by 673% to 3.48 million procedures. The demand for hip revision procedures is projected to double by the year 2026, while the demand for knee revisions is expected to double by 2015. Although hip revisions are currently more frequently performed than knee revisions, the demand for knee revisions is expected to surpass the demand for hip revisions after 2007. Overall, total hip and total knee revisions are projected to grow by 137% and 601%, respectively, between 2005 and 2030. CONCLUSIONS These large projected increases in demand for total hip and knee arthroplasties provide a quantitative basis for future policy decisions related to the numbers of orthopaedic surgeons needed to perform these procedures and the deployment of appropriate resources to serve this need.

Prevalence of primary and revision total hip and knee arthroplasty in the United States from 1990 through 2002.

BACKGROUND The purpose of this study was to quantify the procedural rate and revision burden of total hip and knee arthroplasty in the United States and to determine if the age or gender-based procedural rates and overall revision burden are changing over time. METHODS The National Hospital Discharge Survey (NHDS) for 1990 through 2002 was used in conjunction with United States Census data to quantify the rates of primary and revision arthroplasty as a function of age and gender within the United States with use of methodology published by the American Academy of Orthopaedic Surgeons. Poisson regression analysis was used to evaluate the procedural rate and to determine year-to-year trends in primary and revision arthroplasty rates as a function of both age and gender. RESULTS Both the number and the rate of total hip and knee arthroplasties (particularly knee arthroplasties) increased steadily between 1990 and 2002. Over the thirteen years, the rate of primary total hip arthroplasties per 100,000 persons increased by approximately 50%, whereas the corresponding rate of primary total knee arthroplasties almost tripled. The rate of revision total hip arthroplasties increased by 3.7 procedures per 100,000 persons per decade, and that of revision total knee arthroplasties, by 5.4 procedures per 100,000 persons per decade. However, the mean revision burden of 17.5% for total hip arthroplasty was more than twice that for total knee arthroplasty (8.2%), and this did not change substantially over time. CONCLUSIONS The number and prevalence of primary hip and knee replacements increased substantially in the United States between 1990 and 2002, but the trend was considerably more pronounced for primary total knee arthroplasty. CLINICAL RELEVANCE The reported prevalence trends have important ramifications with regard to the number of joint replacements expected to be performed by orthopaedic surgeons in the future. Because the revision burden has been relatively constant over time, we can expect that a greater number of primary replacements will result in a greater number of revisions unless some limiting mechanism can be successfully implemented to reduce the future revision burden.

Future clinical and economic impact of revision total hip and knee arthroplasty

A recent analysis of historical procedure data indicated that the prevalence of primary and revision total hip and total knee arthroplasty increased steadily between 1990 and 20021. A massive demand for primary and revision surgeries is also expected in the next two decades2. Similarly, the overall incidence of deep infection also has increased substantially between 1990 and 2003 for both total hip arthroplasty and total knee arthroplasty3. In 2003, approximately 1.2% of the total hip arthroplasties performed in the United States were associated with deep infection, which was similar to the rate seen for total knee arthroplasties3. Deep infection is a catastrophic complication of both total hip and total knee arthroplasty, and it also represents a tremendous economic burden4,5. The implications for a growing incidence of infections, coupled with accelerating demand for arthroplasty, remain unexplored. Long-term survival of total hip arthroplasty and total knee arthroplasty implants has been investigated by Scandinavian arthroplasty registries6-8. However, in the United States, national hip and knee registries have not been established9,10. Medicare claims data have been used effectively in longitudinal analysis of mortality and morbidity following joint replacement11, but the feasibility of using this data as a registry substitute is unclear. Along with the projected increase in the utilization of total hip arthroplasty and total knee arthroplasty2, retrospective studies have shown increasing disparity between Medicare reimbursement and hospital charges, with higher charges for revision than for primary procedures12-14. The economic consequences of the projected demand for total hip arthroplasty and total knee arthroplasty are still unknown. The goals of our study were to (1) quantify the future number of infections at the site of arthroplasties done …

Survival after liver resection in metastatic colorectal cancer: review and meta-analysis of prognostic factors

Background Hepatic metastases develop in approximately 50% of colorectal cancer (CRC) cases. We performed a review and meta-analysis to evaluate survival after resection of CRC liver metastases (CLMs) and estimated the summary effect for seven prognostic factors. Methods Studies published between 1999 and 2010, indexed on Medline, that reported survival after resection of CLMs, were reviewed. Meta-relative risks for survival by prognostic factor were calculated, stratified by study size and annual clinic volume. Cumulative meta-analysis results by annual clinic volume were plotted. Results Five- and 10-year survival ranged from 16% to 74% (median 38%) and 9% to 69% (median 26%), respectively, based on 60 studies. The overall summary median survival time was 3.6 (range: 1.7–7.3) years. Meta-relative risks (95% confidence intervals) by prognostic factor were: node positive primary, 1.6 (1.5–1.7); carcinoembryonic antigen level, 1.9 (1.1–3.2); extrahepatic disease, 1.9 (1.5–2.4); poor tumor grade, 1.9 (1.3–2.7); positive margin, 2.0 (1.7–2.5); >1 liver metastases, 1.6 (1.4–1.8); and >3 cm tumor diameter, 1.5 (1.3–1.8). Cumulative meta-analyses by annual clinic volume suggested improved survival with increasing volume. Conclusion The overall median survival following CLM liver resection was 3.6 years. All seven investigated prognostic factors showed a modest but significant predictive relationship with survival, and certain prognostic factors may prove useful in determining optimal therapeutic options. Due to the increasing complexity of surgical interventions for CLM and the inclusion of patients with higher disease burdens, future studies should consider the potential for selection and referral bias on survival.

Economic burden of revision hip and knee arthroplasty in Medicare enrollees

The economic burden to Medicare due to revision arthroplasty procedures has not yet been studied systematically. The economic burden of revisions was calculated as annual reimbursements for revision arthroplasties relative to the sum total reimbursements of primary and revision arthroplasties. We evaluated this revision burden for total hip and knee arthroplasties through investigation of trends in charges and reimbursements in the Medicare population (Parts A and B claims from 1997-2003), while taking into account age and gender effects. Mean annual economic revision burdens were 18.8% (range, 17.4-20.2%) and 8.2% (range, 7.5-9.2%) for total hip arthroplasties and total knee arthroplasties, respectively. Procedural charges increased while reimbursements decreased over the study period, with higher charges observed for revisions than primary arthroplasties. Reimbursements per procedure were 62% to 68% less than associated charges for primary and revision total hip and knee arthroplasties. The effect of age and gender on reimbursements varied by procedure type. Unless some limiting mechanism is implemented to reduce the incidence of revision surgeries, the diverging trends in reimbursements and charges for total hip and knee arthroplasties indicate that the economic impact to the Medicare population and healthcare system will continue to increase.Level of Evidence: Prognostic study, level II-1 (retrospective study). See Guidelines for Authors for a complete description of levels of evidence.

Epidemiology of immune thrombocytopenic purpura in the General Practice Research Database.

The epidemiology of immune thrombocytopenic purpura (ITP) is not well‐characterised in the general population. This study described the incidence and survival of ITP using the UK population‐based General Practice Research Database (GPRD). ITP patients first diagnosed in 1990–2005 were identified in the GPRD. Overall incidence rates (per 100 000 person‐years) and rates by age, sex, and calendar periods were calculated. Survival analysis was conducted using the Kaplan‐Meier and proportional hazard methods. A total of 1145 incident ITP patients were identified. The crude incidence was 3·9 (95% confidence interval [CI]: 3·7–4·1). Overall average incidence was statistically significantly higher in women (4·4, 95% CI: 4·1–4·7) compared to men (3·4; 95% CI: 3·1–3·7). Among men, incidence was bimodal with peaks among ages under 18 and between 75–84 years. The hazard ratio for death among ITP patients was 1·6 (95% CI: 1·3–1·9) compared to age‐ and sex‐matched comparisons. During follow‐up 139 cases died, of whom 75 had a computerised plausible cause of death. Death was related to bleeding in 13% and infection in 19% of these 75. In conclusion, ITP incidence varies with age and is higher in women than men. This potentially serious medical condition is associated with increased mortality in the UK.

Primary and Revision Arthroplasty Surgery Caseloads in the United States from 1990 to 2004

We analyzed the temporal changes in the caseload of primary and revision hip and knee arthroplasty surgeons in the United States between 1990 and 2004. The Nationwide Inpatient Sample was used to identify arthroplasty procedures and the surgeons who performed them. Annual caseloads were analyzed for each procedure; 47% +/- 2% and 39% +/- 2% of hip and knee surgeons performed revisions nationwide. Average revision caseloads increased slightly over time at a rate of 1.2 and 1.4 cases per surgeon per decade for total hip arthroplasty (THA) and total knee arthroplasty (TKA), respectively. The caseload of primary THA and TKA increased by 1.4 and 1.7 cases per surgeon per decade. The caseload for the top 5% of primary THA and TKA surgeons increased from 25 to 45 and 33 to 86, respectively, during this period compared with the median caseload, which increased from 4 to 5 (hip) and 5 to 10 (knee). The revision caseload of surgeons has increased over time, particularly for surgeons with the highest caseloads.

An international assessment of ovarian cancer incidence and mortality

OBJECTIVE To assess and characterize the temporal variation in ovarian cancer incidence and mortality by age within countries in the Americas, Europe, Asia, and Oceania. METHODS/MATERIALS Data from the National Cancer Institutes Surveillance, Epidemiology, and End Results Program in the United States (U.S.) were used to assess ovarian cancer incidence rates (1998-2008) and mortality rates, (1988-2007 for 12-month survival, 1988-2006 for 24-month survival, and 1988-2003 for 60-month survival), stratified by age at diagnosis. Data from GLOBOCAN were used to calculate country-specific incidence rates for 2010 and 2020 and case-fatality rates for 2010. RESULTS A statistically significant decrease in Annual Percent Change (APC) of ovarian cancer incidence was observed in the U.S. for all women (-1.03%), among women who were diagnosed at <65 years of age (-1.09%) and among women who were diagnosed at ≥65 years of age (-0.95%). There was a statistically significant increase in the observed APC for survival at 12-months (0.19%), 24-months (0.58%), and 60-months (0.72%) for all women; however, 5-year survival for advanced stage (III or IV) disease was low at less than 50% for women <65 years and less than 30% for women ≥65 years. Global results showed a wide range in ovarian cancer incidence rates, with China exhibiting the lowest rates and the Russian Federation and the United Kingdom exhibiting the highest rates. CONCLUSIONS Ovarian cancer survival has shown modest improvement from a statistical perspective in the U.S. However, it is difficult to ascertain how clinically relevant these improvements are at the population or patient level.

State-of-the-Science Review: Does Manganese Exposure During Welding Pose a Neurological Risk?

Recent studies report that exposure to manganese (Mn), an essential component of welding electrodes and some steels, results in neurotoxicity and/or Parkinsons disease (PD) in welders. This “state-of-the-science” review presents a critical analysis of the published studies that were conducted on a variety of Mn-exposed occupational cohorts during the last 100 yr, as well as the regulatory history of Mn and welding fumes. Welders often perform a variety of different tasks with varying degrees of duration and ventilation, and hence, to accurately assess Mn exposures that occurred in occupational settings, some specific information on the historical work patterns of welders is desirable. This review includes a discussion of the types of exposures that occur during the welding process—for which limited information relating airborne Mn levels with specific welding activities exists—and the human health studies evaluating neurological effects in welders and other Mn-exposed cohorts, including miners, millers, and battery workers. Findings and implications of studies specifically conducted to evaluate neurobehavioral effects and the prevalence of PD in welders are also discussed. Existing exposure data indicate that, in general, Mn exposures in welders are less than those associated with the reports of clinical neurotoxicity (e.g., “manganism”) in miners and smelter workers. It was also found that although manganism was observed in highly exposed workers, the scant exposure-response data available for welders do not support a conclusion that welding is associated with clinical neurotoxicity. The available data might support the development of reasonable “worst-case” exposure estimates for most welding activities, and suggest that exposure simulation studies would significantly refine such estimates. Our review ends with a discussion of the data gaps and areas for future research.

Human health risk and exposure assessment of chromium (VI) in tap water.

Hexavalent chromium [Cr(VI)] has been detected in groundwater across the United States due to industrial and military operations, including plating, painting, cooling-tower water, and chromate production. Because inhalation of Cr(VI) can cause lung cancer in some persons exposed to a sufficient airborne concentration, questions have been raised about the possible hazards associated with exposure to Cr(VI) in tap water via ingestion, inhalation, and dermal contact. Although ingested Cr(VI) is generally known to be converted to Cr(III) in the stomach following ingestion, prior to the mid-1980s a quantitative analysis of the reduction capacity of the human stomach had not been conducted. Thus, risk assessments of the human health hazard posed by contaminated drinking water contained some degree of uncertainty. This article presents the results of nine studies, including seven dose reconstruction or simulation studies involving human volunteers, that quantitatively characterize the absorbed dose of Cr(VI) following contact with tap water via all routes of exposure. The methodology used here illustrates an approach that permits one to understand, within a very narrow range, the possible intake of Cr(VI) and the associated health risks for situations where little is known about historical concentrations of Cr(VI). Using red blood cell uptake and sequestration of chromium as an in vivo metric of Cr(VI) absorption, the primary conclusions of these studies were that: (1) oral exposure to concentrations of Cr(VI) in water up to 10 mg/L (ppm) does not overwhelm the reductive capacity of the stomach and blood, (2) the inhaled dose of Cr(VI) associated with showering at concentrations up to 10 mg/L is so small as to pose a de minimis cancer hazard, and (3) dermal exposures to Cr(VI) in water at concentrations as high as 22 mg/L do not overwhelm the reductive capacity of the skin or blood. Because Cr(VI) in water appears yellow at approximately 1-2 mg/L, the studies represent conditions beyond the worst-case scenario for voluntary human exposure. Based on a physiologically based pharmacokinetic model for chromium derived from published studies, coupled with the dose reconstruction studies presented in this article, the available information clearly indicates that (1) Cr(VI) ingested in tap water at concentrations below 2 mg/L is rapidly reduced to Cr(III), and (2) even trace amounts of Cr(VI) are not systemically circulated. This assessment indicates that exposure to Cr(VI) in tap water via all plausible routes of exposure, at concentrations well in excess of the current U.S. Environmental Protection Agency (EPA) maximum contaminant level of 100 w g/L (ppb), and perhaps those as high as several parts per million, should not pose an acute or chronic health hazard to humans. These conclusions are consistent with those recently reached by a panel of experts convened by the State of California.