Treatment Failure Among Infected Periprosthetic Patients at a Highly Specialized Revision TKA Referral Practice

Deep infection is a serious and costly complication of total knee arthroplasty (TKA), which can increase patient morbidity and compromise functional outcome and satisfaction. Two-stage revision with an interval of parental antibiotics has been shown to be the most successful treatment in eradicating deep infection following TKA. We report a large series by a single surgeon with a highly specialized revision TKA referral practice. We identified 84 patients treated by a two-stage revision. We defined “successful two-stage revision” as negative intraoperative cultures and no further infection-related procedure. We defined “eradication of infection” on the basis of negative cultures and clinical diagnosis. After a mean follow up of 25 months, eradication of the infection was documented in 90.5% of the patients; some had undergone further surgical intervention after the index two-stage procedure. Successful two-stage revision (e.g. no I&D, fusion, amputation) was documented only in 63.5% of the patients. We also observed a trend between presence of resistant staphylococcus (MRSA) (p=0.05) as well as pre-revision surgical procedures (p=0.08) and a lower likelihood of successfully two-stage revision. Factors affecting the high failure rate included multiple surgeries prior to the two-stage revision done at our institution, and high prevalence of MRSA present among failed cases. The relatively high rate of failure to achieve a successful two-stage revision observed in our series may be attributed to the highly specialized referral practice. Thus increasing the prevalence of patients with previous failed attempts at infection eradication and delayed care as well as more fragile and immune compromised hosts

Treatment Failure Among Infected Periprosthetic Total Hip Arthroplasty Patients

Two-stage revision has been shown to be the most successful treatment in eradicating deep infection following total hiparthroplasty. We identified 62 patients treated by a two-stage revision. We defined “successful revision” as negative intraoperative cultures and no further infection-related procedure. We defined “eradication of infection” on the basis of negative cultures and clinical diagnosis at least one year after 2nd stage procedure. After a mean follow up of 2.7 years, eradication of the infection was documented in 91.1%, and a successful two-stage revision in 85.7% of patients. We observed no association between higher pre-reimplantation levels of ESR and C-reactive protein and lower likelihood of successful two-stage revision. We found an association between a history of another previous infected prosthetic joint and a failed 2nd stage procedure. Failure to achieve eradication of infection and successful two-stage revision occurs infrequently. Patients with prior history of a previous prosthetic joint infection are at higher risk of failure

Ozone air quality and radiative forcing consequences of changes in ozone precursor emissions

Changes in emissions of ozone (O3) precursors affect both air quality and climate. We first examine the sensitivity of surface O3 concentrations (O3srf) and net radiative forcing of climate (RFnet) to reductions in emissions of four precursors – nitrogen oxides (NOx), non-methane volatile organic compounds, carbon monoxide, and methane (CH4). We show that long-term CH4-induced changes in O3, known to be important for climate, are also relevant for air quality; for example, NOx reductions increase CH4, causing a long-term O3 increase that partially counteracts the direct O3 decrease. Second, we assess the radiative forcing resulting from actions to improve O3 air quality by calculating the ratio of ΔRFnet to changes in metrics of O3srf. Decreases in CH4 emissions cause the greatest RFnet decrease per unit reduction in O3srf, while NOx reductions increase RFnet. Of the available means to improve O3 air quality, therefore, CH4 abatement best reduces climate forcing

Synthesis and Assessment Product

This report focuses on the Climate Projections Based on Emissions Scenarios. The influence of greenhouse gases and particle pollution on our present and future climate has been widely examined. While both long-lived (e.g., carbon dioxide) and short-lived (e.g., soot) gases and particles affect the climate, other projections of future climate, such as the IPCC reports focus largely on the long-lived gases. This U.S. Climate Change Science Program Synthesis and Assessment Product provides a different emphasis. The authors examine the effect of long-lived greenhouse gases on the global climate based on updated emissions scenarios produced by another CCSP Synthesis and Assessment Product (SAP 2.1a). In these scenarios, atmospheric concentrations of the long-lived greenhouse gases leveled off, or stabilized, at predetermined levels by the end of the twenty-first century (unlike in the IPCC scenarios). However, the projected future temperature changes fall within the same range as those projected for the latest IPCC report. The authors confirm the robust future warming signature and other associated changes in the climate

Radiative Flux and Forcing Parameterization Error in Aerosol-Free Clear Skies

This article reports on the accuracy in aerosol- and cloud-free conditions of the radiation parameterizations used in climate models. Accuracy is assessed relative to observationally validated reference models for fluxes under present-day conditions and forcing (flux changes) from quadrupled concentrations of carbon dioxide. Agreement among reference models is typically within 1 W/m2, while parameterized calculations are roughly half as accurate in the longwave and even less accurate, and more variable, in the shortwave. Absorption of shortwave radiation is underestimated by most parameterizations in the present day and has relatively large errors in forcing. Error in present-day conditions is essentially unrelated to error in forcing calculations. Recent revisions to parameterizations have reduced error in most cases. A dependence on atmospheric conditions, including integrated water vapor, means that global estimates of parameterization error relevant for the radiative forcing of climate change will require much more ambitious calculations

Characterizing the tropospheric ozone response to methane emission controls and the benefits to climate and air quality

Reducing methane (CH4) emissions is an attractive option for jointly addressing climate and ozone (O3) air quality goals. With multidecadal full-chemistry transient simulations in the MOZART-2 tropospheric chemistry model, we show that tropospheric O3 responds approximately linearly to changes in CH4 emissions over a range of anthropogenic emissions from 0–430 Tg CH4 a−1 (0.11–0.16 Tg tropospheric O3 or ∼11–15 ppt global mean surface O3 decrease per Tg a−1 CH4 reduced). We find that neither the air quality nor climate benefits depend strongly on the location of the CH4 emission reductions, implying that the lowest cost emission controls can be targeted. With a series of future (2005–2030) transient simulations, we demonstrate that cost-effective CH4 controls would offset the positive climate forcing from CH4 and O3 that would otherwise occur (from increases in NOx and CH4 emissions in the baseline scenario) and improve O3 air quality. We estimate that anthropogenic CH4 contributes 0.7 Wm−2 to climate forcing and ∼4 ppb to surface O3 in 2030 under the baseline scenario. Although the response of surface O3 to CH4 is relatively uniform spatially compared to that from other O3 precursors, it is strongest in regions where surface air mixes frequently with the free troposphere and where the local O3 formation regime is NOx-saturated. In the model, CH4 oxidation within the boundary layer (below ∼2.5 km) contributes more to surface O3 than CH4 oxidation in the free troposphere. In NOx-saturated regions, the surface O3 sensitivity to CH4 can be twice that of the global mean, with >70% of this sensitivity resulting from boundary layer oxidation of CH4. Accurately representing the NOx distribution is thus crucial for quantifying the O3 sensitivity to CH4

Leaf colour as a signal of chemical defence to insect herbivores in wild cabbage (Brassica Oleracea)

Leaf colour has been proposed to signal levels of host defence to insect herbivores, but we lack data on herbivory, leaf colour and levels of defence for wild host populations necessary to test this hypothesis. Such a test requires measurements of leaf spectra as they would be sensed by herbivore visual systems, as well as simultaneous measurements of chemical defences and herbivore responses to leaf colour in natural host-herbivore populations. In a large-scale field survey of wild cabbage (Brassica oleracea) populations, we show that variation in leaf colour and brightness, measured according to herbivore spectral sensitivities, predicts both levels of chemical defences (glucosinolates) and abundance of specialist lepidopteran (Pieris rapae) and hemipteran (Brevicoryne brassicae) herbivores. In subsequent experiments, P. rapae larvae achieved faster growth and greater pupal mass when feeding on plants with bluer leaves, which contained lower levels of aliphatic glucosinolates. Glucosinolate-mediated effects on larval performance may thus contribute to the association between P. rapae herbivory and leaf colour observed in the field. However, preference tests found no evidence that adult butterflies selected host plants based on leaf coloration. In the field, B. brassicae abundance varied with leaf brightness but greenhouse experiments were unable to identify any effects of brightness on aphid preference or performance. Our findings suggest that although leaf colour reflects both levels of host defences and herbivore abundance in the field, the ability of herbivores to respond to colour signals may be limited, even in species where performance is correlated with leaf colour