Search

Erik Bülow,1,2 Ute Hahn,3,4 Ina Trolle Andersen,3 Ola Rolfson,1,2 Alma B Pedersen,3,5 Nils P Hailer6 1The Swedish Arthroplasty Register, Centre of Registers Västra Götaland, Gothenburg, Sweden; 2Department of Orthopaedics, Institute of Clinical Sciences, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; 3Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark; 4Department of Mathematics, Aarhus University, Aarhus, Denmark; 5Department of Clinical Medicine, Aarhus University, Aarhus, Denmark; 6Department of Surgical Sciences/Orthopaedics, Uppsala University Hospital, Uppsala, SwedenCorrespondence: Erik Bülow, The Swedish Arthroplasty Register, Centre of Registers Västra Götaland, Gothenburg, SE-413 45, Sweden, Tel +46 70 08 234 28, Email erik.bulow@gu.sePurpose: To develop a parsimonious risk prediction model for periprosthetic joint infection (PJI) within 90 days after total hip arthroplasty (THA).Patients and Methods: We used logistic LASSO regression with bootstrap ranking to develop a risk prediction model for PJI within 90 days based on a Swedish cohort of 88,830 patients with elective THA 2008– 2015. The model was externally validated on a Danish cohort with 18,854 patients.Results: Incidence of PJI was 2.45% in Sweden and 2.17% in Denmark. A model with the underlying diagnosis for THA, body mass index (BMI), American Society for Anesthesiologists (ASA) class, sex, age, and the presence of five defined comorbidities had an area under the curve (AUC) of 0.68 (95% CI: 0.66 to 0.69) in Sweden and 0.66 (95% CI: 0.64 to 0.69) in Denmark. This was superior to traditional models based on ASA class, Charlson, Elixhauser, or the Rx Risk V comorbidity indices. Internal calibration was good for predicted probabilities up to 10%.Conclusion: A new PJI prediction model based on easily accessible data available before THA was developed and externally validated. The model had superior discriminatory ability compared to ASA class alone or more complex comorbidity indices and had good calibration. We provide a web-based calculator (https://erikbulow.shinyapps.io/thamortpred/) to facilitate shared decision making by patients and surgeons.Keywords: prediction model, total hip arthroplasty, orthopaedics, clinical decision-making tool, web calculator, external validation

This study investigates frost susceptibility of sub-base gravel determined by the ASTM D5918-13 standard as a conservative estimate of the frost heave risk of fill in overfilled arch bridges, particularly in Pearl-Chain Bridges. Frost heave of granular materials has been of great research interest from the end of the 1920s until the present day. Most new literature relates to empirical results that are several decades old. This is also the case for Danish tender specifications according to which the frost susceptibility of a sub-base gravel is solely assessed from its fines content. However, no actual frost tests have been carried out to verify this assumption. In the present study, the frost susceptibility of four different Danish gravel materials is categorised from their heave rate. We test two Danish sub-base gravel materials, with particle size distributions of 0-8 mm and 0-31.5 mm, respectively, and also two modified sub-base gravel materials with increased and reduced fines contents. The fines content of the gravel materials is analysed by laser diffraction, and compared with two common frost susceptibility criteria, Casagrande’s and Schaible’s, and with Danish tender specifications. Even though the two sub-base gravel materials are expected to be frost safe, 0-31.5 mm sub-base gravel shows medium frost susceptibility, whereas 0-8 mm sub-base gravel shows negligible frost susceptibility. The gravel materials with increased and reduced fines content are categorised as having low to medium frost susceptibility and low frost susceptibility, respectively. The permeability of the gravel materials is determined, and the permeability coefficient of 0-31.5 mm sub-base gravel is five times greater than that of 0-8 mm sub-base gravel. The results suggest that the criterion used to classify the frost susceptibility of Danish sub-base gravel materials based solely on their fines content is insufficient, and that the permeability coefficient should also be considered. [ABSTRACT FROM AUTHOR]