Objectives: There have been conflicting reports regarding the effects of obesity on both surgical time and blood loss following anatomic shoulder arthroplasty. Varying categories of obesity has made comparison amongst existing studies difficult. Methods: A retrospective review of consecutive anatomic shoulder arthroplasty cases (aTSA) was undertaken. Demographic data, including age, gender, body mass index (BMI), age-adjusted Charleson Comorbidity Index (ACCI), operative time, hospital length of stay (LOS), and both POD#۱ and discharge visual analogue score (VAS) was collected. Intra-operative total blood volume loss (ITBVL) and need for transfusion was calculated. BMI was categorized as non-obese (<۳۰ kg/m۲), obese (۳۰-۴۰ kg/m۲) and morbidly obese (≥۴۰ kg/m۲). Unadjusted associations of BMI with operative time, ITBVL and LOS were examined using Spearman correlation coefficients. Regression analysis was used to identify factors associated with hospital LOS. Results: There were ۱۳۰ aTSA cases performed, including ۴۵ short stem and ۸۵ stemless implants, of which ۲۳ (۱۷.۷%) were morbidly obese, ۶۰ (۴۶.۲%) were obese and ۴۷ (۳۶.۱%) were non-obese. Median
operative time for the morbidly obese cohort was ۱۱۹.۵ minutes (IQR ۹۳.۰, ۱۴۲.۰) versus ۱۱۶.۵ minutes (IQR ۹۹.۵, ۱۳۴.۵) for the obese cohort versus ۱۲۵.۰ minutes (IQR, ۹۹.۰, ۱۴۶.۰) for the non-obese cohort. (P=۰.۶۱) The median ITBVL for the morbidly obese cohort was ۲۳۵.۸ ml (IQR ۱۴۴.۳, ۳۲۹.۷) versus ۲۲۰.۱ ml (IQR ۱۴۷.۷, ۲۶۲.۷) for the obese cohort versus ۲۱۶.۳ ml (IQR ۱۳۹.۷, ۳۱۵.۵) for the non-obese cohort. (P=۰.۷۲). BMI ≥۴۰kg/m۲ (IRR ۱.۳۲, P=۰.۰۳۸), age (IRR ۱.۰۱, P=۰.۰۲۶), and female gender (IRR ۱.۵۴, P<۰.۰۰۱) were predictive of increased LOS. There was no difference with regards to in-hospital medical complications (P=۰.۱۳), surgical complications (P=۱.۰), need for re-operation (P=۰.۶۶) and ۳۰-day return to the ER (P=۰.۰۶). Conclusion: Morbid obesity was not associated with increased surgical time, ITBVL and perioperative medical or surgical complications following aTSA, though it was predictive of increased hospital LOS. Level of evidence: III