Determining the Risk of Septic Arthritis Following Intra-Articular Injection of Drugs Mixed At A Tertiary Care Center, 2012–2017

Abstract

BACKGROUND Intra-articular corticosteroid injections are commonly used for the outpatient treatment of osteoarticular pain. Practitioners may choose to administer additional medications such as anesthetics. While medications are compounded in the pharmacy following stringent environmental requirements, occasionally injections with additional components for immediate use are mixed at the point of care under less strict environmental conditions due to turnaround time requirement. We assessed if mixing multiple drugs in a single syringe in outpatient settings was associated with subsequent septic arthritis. METHODS We reviewed electronic pharmacy medication administration records of patients who received an intra-articular corticosteroid injection at a tertiary care center during 2012–2017. We extracted basic patient demographics. Exposure was defined as receiving more than one intra-articular medication during a single injection-encounter. The outcome was culture-confirmed septic arthritis defined as a?positive synovial fluid culture within 90?days following an intra-articular?injection. We present case counts, ranges, and frequencies. RESULTS 7,072 unique patients received an intra-articular injection. Mean age was 55?years (range: 9 – 104) and 41% were male. There were 13,089 distinct intra-articular injection-encounters. Of the unique encounters, 306 (2%) intra-articular injection involved only one medication; 12,080 (92%) received 2 medications; 596 (5%) received 3 medications; 104 (0.8%) received 4 medications; and 3?(0.02%) received 5 medications. There were no infections following single intra-articular medication injection-encounters. Two septic arthritis cases were identified in patients who received two intra-articular medications (triamcinolone and lidocaine 1%). The microorganisms were: Staphylococcus aureus and Enterobacter cloacae. CONCLUSIONS Intra-articular corticosteroid injection practices in outpatient settings are heterogeneous. Septic arthritis following intra-articular injection was infrequent. We were unable to associate septic arthritis with mixing intra-articular injectables outside the pharmacy.