Wang Y, et al. - From 2006 to 2014 discharge records from the Nationwide Inpatient Sample, and study population and inpatient complications by International Classification of Diseases, 9th Revision, Clinical Modification diagnosis/procedure codes were identified by experts to determine the impact of bariatric surgery (efficient in losing weight and decreasing comorbidities associated with obesity) on the outcome of arthroplasty in a large population. A rising trend was exhibited by the patients in proportion of morbid obesity in both total knee arthroplasty (TKA) and total hip arthroplasty (THA), while after 2007, proportion of bariatric surgery in morbidly obese TKA and THA patients persisted to be the same. Fewer pulmonary embolism, more blood transfusion and anemia, shorter length of stay in bariatric surgery group were noted in for THA subjects. Bariatric surgery group exhibited a lower risk of pulmonary embolism, respiratory complications, death and shorter length of stay for TKA patients, however, bariatric surgery group presented with a higher risk of blood transfusion and anemia. Hence, evidences that bariatric surgery before to arthroplasty, especially THA, seemed to diminish rates of pulmonary complications and length of stay, were concluded. However, anemia and blood transfusion appeared to be more often in subjects with prior bariatric surgery.