These authors queried a national insurance database to evaluate the association of preoperative intra-articular shoulder injection before shoulder arthroscopy and arthroplasty with the incidence of postoperative infection for surgeries performed between 2005 and 2012. Control cohorts were created for each study group by matching patients who underwent the same procedure without a preoperative injection to the study cohorts based on age, gender, obesity, diabetes and smoking.
Three shoulder arthroscopy cohorts were created: shoulders having arthroscopy within 3 months of ipsilateral shoulder injection, shoulders having arthroscopy between 3 and 12 months after ipsilateral shoulder injection, and matched control arthroscopy without prior injection.
Three similar shoulder arthroplasty cohorts were created.
Infection rates within 3 and 6 months postoperatively were assessed using ICD-9 and CPT codes.
The incidence of infection after shoulder arthroscopy at 3 months (0.7%, OR 2.2, P < 0.0001) and 6 months (1.1%, OR 1.6, P = 0.003) was significantly higher in patients who underwent injection within the 3 months prior to arthroscopy compared to matched controls [Table 1A-B].
The incidence of infection after shoulder arthroplasty at 3 months (3.0%, OR 2.0, P = 0.007) and 6 months (4.6%, OR 2.0, P = 0.001) was significantly higher in patients who underwent injection within the 3 months prior to arthroplasty compared to matched controls [Table 2A-B].
There was no significant difference in infection rates in patients who underwent shoulder arthroscopy or arthroplasty between 3–12 months after injection compared to controls.
Comment: Patients often ask about having an injection to address their symptoms before proceeding with surgery. The data presented here suggest that injections within three months of surgery increase the risk of subsequent infection.
Because of the nature of the data base, we do not know details, such as what was injected, which organisms were responsible for the infections, and how serious the infections were. Nevertheless, we now have useful information that we can share with our patients who are asking for injections.
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