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Aims High body mass index (BMI) is associated with increased rates of complications in primary total hip arthroplasty (THA), but less is known about its impact on cost. The effects of low BMI on outcomes and cost are less understood. This study evaluated the relationship between BMI, inpatient costs, complications, readmissions, and utilization of post-acute services. Methods A retrospective database analysis of 40,913 primary THAs performed between January 2013 and December 2017 in 29 hospitals was conducted. Operating time, length of stay (LOS), complication rate, 30-day readmission rate, inpatient cost, and utilization of post-acute services were measured and compared in relation to patient BMI. Results Mean operating time increased with BMI and for BMI > 50 kg/m2 was approximately twice that of BMI 10 kg/m2 to 15 kg/m2. Mean inpatient cost did not vary significantly with BMI. Mean total reimbursement was lowest for the lowest BMI cohort and increased with BMI. Mean LOS was greatest at the extremes of BMI (4.0 days for BMI 10 kg/m2 to 15 kg/m2; 3.75 days for BMI > 50 kg/m2) and twice that of normal BMI. Mean complication rates were greatest in the lowest BMI cohort (16% for BMI 10 kg/m2 to 15 kg/m2) and five times the mean rate of complications in the normal BMI cohorts. Furthermore, 30-day readmissions were greatest in the highest BMI cohort (10% for BMI > 50 kg/m2) and five times the rate for normal BMI patients. Conclusion LOS, complications, and 30-day readmissions all increase at the extremes of BMI and appear to be greater than those of patients with normal BMI. The lowest BMI patients had the lowest payment for inpatient stay yet were at considerable risk for complications and readmission. Patients with extreme BMI should be counselled about their increased risk of complications for THA and nutritional status/obesity optimized preoperatively if possible. Cite this article: Bone Joint J 2020;102-B(7 Supple B):62–70.

Rarely are scientific phenomena isolated to a single discipline such as biology, chemistry, physics, Earth science, or others. Rather, these phenomena span multiple disciplines and often require bringing together content and understandings from multiple disciplines to engage with or explain the target phenomena. This study uses a model-based explanations framework to explore high school students’ abilities to integrate science content from the disciplines of chemistry and Earth science within the context of generating models to explain a local phenomenonthe urban heat island effect. Students experienced a multiweek instructional unit as part of a larger integrated curriculum that brings together chemistry and Earth science content and features local phenomena to engage students in the scientific practice of modeling. Quantitative and qualitative findings from this study demonstrate students’ emerging proficiency with integrating science content, practices, and crosscutting concepts to explain a phenomenon. Students’ model-based explanations tended to include phenomenon-relevant components (e.g., physical features of the phenomenon) and sequences (e.g., cause–effect relationships), but tended to include relatively fewer explanatory mechanisms. Implications related to the utility of modeling as a practice-based venue for integrating content from diverse science disciplines are also discussed.

Complex cardiac procedures often require blood transfusion because of surgical bleeding or coagulopathy. Thrombelastography (TEG) was introduced in our institution to direct transfusion management in cardiothoracic surgery. The goal of this study was to quantify the effect of TEG on transfusion rates peri- and postoperatively. All patients who underwent complex cardiac surgery, defined as open multiple valve repair/replacement, coronary artery bypass grafting with open valve repair/replacement, or aortic root/arch repair before and after implementation of TEG were identified and retrospectively analyzed. Minimally invasive cases were excluded. Patient characteristics and blood use were compared with t test and chi-square test. A generalized linear model including patient characteristics, preoperative and postoperative lab values, and autotransfusion volume was used to determine the impact of TEG on perioperative, postoperative, and total blood use. In total, 681 patients were identified, 370 in the pre-TEG period and 311 patients post-TEG. Patient demographics were not significantly different between periods. Mean units of red blood cells, plasma, and cryoprecipitate were significantly reduced after TEG was implemented (all, p < .0001); use of platelets was reduced but did not reach significance. Mean units of all blood products in the perioperative period and over the entire stay were reduced by approximately 40% (both, p < .0001). Total proportion of patients exposed to transfusion was significantly lower after introduction of TEG (p < .01). Controlling for related factors on multivariate analysis, such as preoperative laboratory values and autotransfusion volume, use of TEG was associated with significant reduction in perioperative and overall blood product transfusion. TEG-directed management of blood product administration during complex cardiac surgeries significantly reduced the units of blood products received perioperatively but not blood usage more than 24 hours after surgery. Overall, fewer patients were exposed to allogenic blood. The use of TEG to guide blood product administration significantly impacted transfusion therapy and associated costs.