Assessing electron beam sensitivity for SrTiO3 and La0.7Sr0.3MnO3 using electron energy loss spectroscopy

Thresholds for beam damage have been assessed for La0.7Sr0.3MnO3 and SrTiO3 as a function of electron probe current and exposure time at 80 and 200 kV acceleration voltage. The materials were exposed to an intense electron probe by aberration corrected scanning transmission electron microscopy (STEM) with simultaneous acquisition of electron energy loss spectroscopy (EELS) data. Electron beam damage was identified by changes of the core loss fine structure after quantification by a refined and improved model based approach. At 200 kV acceleration voltage, damage in SrTiO3 was identified by changes both in the EEL fine structure and by contrast changes in the STEM images. However, the changes in the STEM image contrast as introduced by minor damage can be difficult to detect under several common experimental conditions. No damage was observed in SrTiO3 at 80 kV acceleration voltage, independent of probe current and exposure time. In La0.7Sr0.3MnO3, beam damage was observed at both 80 and 200 kV acceleration voltages. This damage was observed by large changes in the EEL fine structure, but not by any detectable changes in the STEM images. The typical method to validate if damage has been introduced during acquisitions is to compare STEM images prior to and after spectroscopy. Quantifications in this work show that this method possibly can result in misinterpretation of beam damage as changes of material properties

Strategy for reliable strain measurement in InAs/GaAs materials from high-resolution Z-contrast STEM images

Geometric phase analysis (GPA), a fast and simple Fourier space method for strain analysis, can give useful information on accumulated strain and defect propagation in multiple layers of semiconductors, including quantum dot materials. In this work, GPA has been applied to high resolution Z-contrast scanning transmission electron microscopy (STEM) images. Strain maps determined from different g vectors of these images are compared to each other, in order to analyze and assess the GPA technique in terms of accuracy. The SmartAlign tool has been used to improve the STEM image quality getting more reliable results. Strain maps from template matching as a real space approach are compared with strain maps from GPA, and it is discussed that a real space analysis is a better approach than GPA for aberration corrected STEM images

Methods for Establishing Quality Weights for Life Years

Several valuation techniques are in use for quality adjusting life years in cost utility analysis. The paper gives an overview of the variability in results. A close inspection of a number of instruments with respect to their theme, instructions, decision framing and the phrasing of questions make many of the observed differences in results understandable. When judging the validity of the different techniques, three points should be kept in mind. One is that statements about validity should be made with respect to concrete versions rather than broad categories like "the rating scale", "time trade-off" etc. Another point is that a valuation technique that is valid in clinical decision analysis may not be valid in health program evaluation, and vice versa. The third point is that quality weights for life years are empirically more meaningful, in the sense that they are more amenable to empirical testing, if they are interpreted simply as preference weights rather than measures of amounts of well life in the utilitarian tradition. Time trade-off with a moderate time horizon is recommended in clinical decision analysis, while a combination of time trade-off and a variant of person trade-off is recommended in health program evaluation

An expanded multilocus sequence typing scheme for propionibacterium acnes : investigation of 'pathogenic', 'commensal' and antibiotic resistant strains

The Gram-positive bacterium Propionibacterium acnes is a member of the normal human skin microbiota and is associated with various infections and clinical conditions. There is tentative evidence to suggest that certain lineages may be associated with disease and others with health. We recently described a multilocus sequence typing scheme (MLST) for P. acnes based on seven housekeeping genes (http://pubmlst.org/pacnes). We now describe an expanded eight gene version based on six housekeeping genes and two ‘putative virulence’ genes (eMLST) that provides improved high resolution typing (91eSTs from 285 isolates), and generates phylogenies congruent with those based on whole genome analysis. When compared with the nine gene MLST scheme developed at the University of Bath, UK, and utilised by researchers at Aarhus University, Denmark, the eMLST method offers greater resolution. Using the scheme, we examined 208 isolates from disparate clinical sources, and 77 isolates from healthy skin. Acne was predominately associated with type IA1 clonal complexes CC1, CC3 and CC4; with eST1 and eST3 lineages being highly represented. In contrast, type IA2 strains were recovered at a rate similar to type IB and II organisms. Ophthalmic infections were predominately associated with type IA1 and IA2 strains, while type IB and II were more frequently recovered from soft tissue and retrieved medical devices. Strains with rRNA mutations conferring resistance to antibiotics used in acne treatment were dominated by eST3, with some evidence for intercontinental spread. In contrast, despite its high association with acne, only a small number of resistant CC1 eSTs were identified. A number of eSTs were only recovered from healthy skin, particularly eSTs representing CC72 (type II) and CC77 (type III). Collectively our data lends support to the view that pathogenic versus truly commensal lineages of P. acnes may exist. This is likely to have important therapeutic and diagnostic implications

No difference in risk of revision due to infection between clindamycin and cephalosporins as antibiotic prophylaxis in cemented primary total knee replacements: a report from the Norwegian Arthroplasty Register 2005–2020

Background and purpose: Systemic antibiotic prophylaxis with clindamycin, which is often used in penicillin- or cephalosporin-allergic patients’, has been associated with a higher risk of surgical revision for deep prosthetic joint infection (PJI) than cloxacillin in primary total knee replacement (TKR). We aimed to investigate whether clindamycin increases the risk of surgical revisions due to PJI compared with cephalosporins in primary cemented TKR. Patients and methods: Data from 59,081 TKRs in the Norwegian Arthroplasty Register (NAR) 2005–2020 was included. 2,655 (5%) received clindamycin and 56,426 (95%) received cephalosporins. Cox regression analyses were performed with adjustment for sex, age groups, diagnosis, and ASA score. Survival times were calculated using Kaplan–Meier estimates and compared using Cox regression with revision for PJI as endpoint. The cephalosporins cefalotin and cefazolin were also compared. Results: Of the TKRs included, 1.3% (n = 743) were revised for PJI. 96% (n = 713) had received cephalosporins and 4% (n = 30) clindamycin for perioperative prophylaxis. Comparing cephalosporins (reference) and clindamycin, at 3-month follow-up the adjusted hazard ratio rate (HRR) for PJI was 0.7 (95% confidence interval [CI] 0.4–1.4), at 1 year 0.9 (CI 0.6–1.5), and at 5 years 0.9 (CI 0.6–1.4). Analysis using propensity score matching showed similar results. Furthermore, comparing cefalotin (reference) and cefazolin, HRR was 1.0 (CI 0.8–1.4) at 3 months and 1.0 (CI 0.7–1.3) at 1-year follow-up. Conclusion: We found no difference in risk of revision for PJI when using clindamycin compared with cephalosporins in primary cemented TKRs. It appears safe to continue the use of clindamycin in penicillin- or cephalosporin-allergic patients.publishedVersio

Geographical variation in orthopedic procedures in Norway: Cross-sectional population-based study

Background: Standardized surgery rates for common orthopedic procedures vary across geographical areas in Norway. We explored whether area-level factors related to demand and supply in publicly funded healthcare are associated with geographical variation in surgery rates for six common orthopedic procedures. Methods: The present study is a cross-sectional population-based study of hospital referral areas in Norway. We included adult admissions for arthroscopy for degenerative knee disease, arthroplasty for osteoarthritis of the knee and hip, surgical treatment for hip fracture, and decompression with/without fusion for lumbar disk herniation and lumbar spinal stenosis in 2012–2016. Variation in age and sex standardized rates was estimated using extremal quotients, coefficients of variation, and systematic components of variation (SCV). Associations between surgery rates and the socioeconomic factors urbanity, unemployment, low-income, high level of education, mortality, and number of surgeons and hospitals were explored with linear regression analyses. Results: Knee arthroscopy showed highest level of variation (SCV 10.3) and decreased in numbers. Variation was considerable for spine surgery (SCV 3.8–4.9), moderate to low for arthroplasty procedures (SCV 0.8–2.6), and small for hip fracture surgery (SCV 0.2). Higher rates of knee arthroscopy were associated with more orthopedic surgeons (adjusted coefficient 24.8, 95% confidence interval (CI): 2.7–47.0), and less urban population (adjusted coefficient −13.3, 95% CI: −25.4 to −1.2). Higher spine surgery rates were associated with more hospitals (adjusted coefficient 22.4, 95% CI: 4.6–40.2), more urban population (adjusted coefficient 2.1, 95% CI: 0.4–3.8), and lower mortality (adjusted coefficient −192.6, 95% CI: −384.2 to −1.1). Rates for arthroplasty and hip fracture surgery were not associated with supply/demand factors included. Conclusions: Arthroscopy for degenerative knee disease decreased in line with guidelines, but showed high variation of surgery rates. Socioeconomic factors included in this study did not explain geographical variation in orthopedic surgery.publishedVersio

Cementing techniques for total knee arthroplasty in Norwegian hospitals; a questionnaire-based study

Background - Cementing technique in total knee arthroplasty (TKA) may influence implant survival. There is limited knowledge about the results with clinically used techniques. The aim of this study was to investigate cementing techniques for TKA in Norwegian hospitals, to compare widely used techniques to recommendations from the literature, and to investigate variation within hospitals. Methods - A questionnaire requesting information about cementing techniques were distributed to all Norwegian orthopedic surgeons performing TKAs regularly in 2020. Data was analyzed using descriptive statistical methods. Results - We acquired 121 responses out of 257 surgeons. They were from 45 out of 56 hospitals, and at least half of the TKA surgeons from 20 hospitals, constituting 79 surgeons. All responders used pulsatile lavage. Cement application to both the tibial plateau and stem (full cementation) was practiced by 61%. Application of cement to both implant and bone was done by 70% of surgeons. Techniques to improve cement penetration were used by 86%. Only 35% of surgeons aimed to get a cement mantle thickness between 3–5 mm. Flexing the knee joint to remove excess cement was done by 82%. We found that in 55% of 20 hospitals the surgeons did not agree on the use of common guidelines in their ward. Conclusions - The majority of the responders used recommended techniques from the literature when cementing TKA. At more than half of the eligible hospitals, surgeons disagreed about their hospitals’ use of common guidelines. Focusing on developing evidence-based guidelines would be beneficial for TKA-quality

Kaplan-Meier and Cox Regression Are Preferable for the Analysis of Time to Revision of Joint Arthroplasty: Thirty-One Years of Follow-up for Cemented and Uncemented THAs Inserted from 1987 to 2000 in the Norwegian Arthroplasty Register

Background: Previous studies have suggested that the probability function of 1 minus the Kaplan-Meier survivorship overestimates revision rates of implants and that patient death should be included in estimates as a competing risk factor. The present study aims to demonstrate that this line of thinking is incorrect and is a misunderstanding of both the Kaplan-Meier method and competing risks. Methods: This study demonstrated the differences, misunderstandings, and interpretations of classical, competing-risk, and illness-death models with use of data from the Norwegian Arthroplasty Register for 15,734 cemented and 7,867 uncemented total hip arthroplasties (THAs) performed from 1987 to 2000, with fixation as the exposure variable. Results: The mean age was higher for patients who underwent cemented (72 years) versus uncemented THA (53 years); as such, a greater proportion of patients who underwent cemented THA had died during the time of the study (47% compared with 29%). The risk of revision at 20 years was 18% for cemented and 42% for uncemented THAs. The cumulative incidence function at 20 years was 11% for cemented and 36% for uncemented THAs. The prevalence of revision at 20 years was 6% for cemented and 31% for uncemented THAs. Conclusions: Adding death as a competing risk will always attenuate the probability of revision and does not correct for dependency between patient death and THA revision. Adjustment for age and sex almost eliminated differences in risk estimates between the different regression models. In the analysis of time until revision of joint replacements, classical survival analyses are appropriate and should be advocated.publishedVersio