The timing of elective shoulder surgery after shoulder injection affects postoperative infection risk in Medicare patients

Background: The goal of this study was to employ a national database to evaluate the association of preoperative injection before shoulder arthroscopy and arthroplasty with the incidence of postoperative infection. Methods: A national database of Medicare patients was queried for patients who underwent shoulder arthroscopy or arthroplasty after ipsilateral shoulder injection. Three arthroscopy cohorts were created: arthroscopy within 3 months of injection (n = 3625), arthroscopy between 3 and 12 months after injection (n = 7069), and matched control arthroscopy without prior injection (n = 186,678). Three arthroplasty cohorts were created: arthroplasty within 3 months of injection (n = 636), arthroplasty between 3 and 12 months after injection (n = 1573), and matched control arthroplasty (n = 6211). Infection rates within 3 and 6 months postoperatively were assessed. Results: The incidence of infection after arthroscopy at 3 months (0.7%; odds ratio [OR], 2.2; P <.0001) and 6 months (1.1%; OR, 1.6; P =.003) was significantly higher in patients who underwent injection within 3 months before arthroscopy compared with controls. The incidence of infection after arthroplasty at 3 months (3.0%; OR, 2.0; P =.007) and 6 months (4.6%; OR, 2.0; P =.001) was significantly higher in patients who underwent injection within 3 months before arthroplasty compared with controls. Conclusions: There was a significant increase in postoperative infection in Medicare patients who underwent injection within 3 months before shoulder arthroscopy and arthroplasty. This association was not noted when shoulder arthroscopy or arthroplasty occurred > 3 months after injection. (C) 2016 Journal of Shoulder and Elbow Surgery Board of Trustees.