Schwarzkopf R, et al. - The payments, timing, and location of unplanned readmissions with Center for Medicare and Medicaid Services (CMS)-defined surgical complications were compared to those readmissions without CMS-defined surgical complications. Using Medicare administrative claims, researchers identified CMS-defined surgical complications in 27.1% (n=6,307) of total hip arthroplasty (THA; N=23,231) patients and 16.4% (n=7,173) of total knee arthroplasty(TKA; N=43,655) patients with unplanned 90-day readmissions. Following THA and TKA, readmissions associated with CMS-defined surgical complications more frequently occurred at the hospital of index surgery, within 30 days of discharge, and had cost higher than readmissions without CMS-defined surgical complications, yet only one in five readmissions were attributed to the CMS-defined surgical complications. This implies delayed readmissions for a large proportion, at other hospitals, potentially unknown to discharging surgeons, for reasons not captured by CMS’s complication measure.