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

BackgroundThe 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.MethodsA 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.ResultsThe 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.ConclusionsThere 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.