Ottesen T, Hsiang WR, Malpani R, et al. - This study was attempted to examine the spectrum of categories for BMI with 30-day perioperative adverse events after primary total shoulder arthroplasty (TSA) to better assess where along the BMI spectrum patients are at risk for complications. Between 2005 and 2016, researchers selected patients undergoing elective TSA from the National Surgical Quality Improvement Program databases. They conducted risk-adjusted multivariate regressions, controlling for demographic variables and overall health. A total of 15,717 patients were included in the study. Compared with normal BMI patients, only underweight TSA patients were observed to have higher rates of 30-day perioperative adverse events, unlike any overweight/obese category including the super morbidly obese. Underweight TSA patients were therefore distinguished as an at-risk subpopulation of TSA patients who had not previously been described. The outcomes demonstrated that physicians and healthcare systems should give additional consideration to this fragile cohort because they often already do for those at the other end of the BMI spectrum.