Editor’s note: The following content was originally scheduled for the AAOS Now Daily Edition, which publishes each year onsite at the AAOS Annual Meeting, but this year’s meeting in March was canceled due to COVID-19. Despite the cancellation, members can access virtual content from the Annual Meeting by visiting the Academy’s Annual Meeting Virtual Experience webpage at aaos.org/VirtualAAOS2020.
A study evaluated the risk of acute infection among patients who received intra-articular corticosteroid injection into a preexisting total knee arthroplasty (TKA). According to the researchers, patients who received an injection had a significantly greater risk of periprosthetic joint infection (PJI) versus patients who did not receive an injection. The findings of the study were presented by Nicole D. Quinlan, MD, MS, as part of the Annual Meeting Virtual Experience.
“It is widely accepted that PJI risks increase significantly if corticosteroid injections are performed preoperatively within three months of the procedure; however, the risk of infection is much less widely studied when these injections are performed postoperatively,” Dr. Quinlan told AAOS Now. “Most single-institution studies provide conflicting data, and no large-scale study exists. A previous study published by Kew et al., in 2019 investigated the risks of periprosthetic infection following corticosteroid injection after total shoulder arthroplasty and found an increased risk of infection if the injection was performed within one month of the arthroplasty procedure. We sought to find out if similar increased risks existed with postoperative injection following TKA as well.”
The study authors queried the Humana dataset for TKA patients treated between 2007 and 2017. Patients who received an ipsilateral knee corticosteroid injection in the postoperative period were matched 2:1 to noninjection controls. Between-group comparisons were made for infection diagnoses six months to one year following an injection and an ipsilateral procedure for infection at any postoperative time point.
Final analysis included 166,946 TKAs, of which 5,628 patients (3.4 percent) received a postoperative corticosteroid injection. At all measured time points, patients who received injections in the same knee were significantly more likely to sustain periprosthetic infection compared to noninjection controls.
“When compared to a matched control cohort, patients who had a postoperative steroid injection were found to have a significantly increased rate of PJI at both six months (1.9 percent versus 1.1 percent; P < 0.0001) and one year (2.4 percent versus 1.4 percent; P < 0.0001) following the injection,” Dr. Quinlan shared. “At all time points studied, patients who underwent postoperative injection had a significantly higher rate of ipsilateral procedures for periprosthetic infection (1.8 percent versus 0.4 percent; P < 0.0001). Finally, the incidence of postoperative injections being performed increased steadily over the study period—from approximately 1 percent in 2007 to around 5 percent in 2017” (Fig. 1).
The increased infection risk for injection patients was in line with what the researchers hypothesized, although Dr. Quinlan said they were “somewhat surprised” that the overall rate of postoperative injections has increased overtime, considering the accumulating data associating the practice with infections.
Dr. Quinlan recommended that physicians use caution when giving existing TKA patients a corticosteroid injection. She also said that patients should be educated on the risks and have an understanding of the significant consequences associated with infection.
The study is limited by its retrospective design, so the authors could not establish infection etiology. Additionally, the dataset may not be representative of the whole population. Lastly, the researchers were unable to control for confounding factors.
“Further evaluation with a prospective study to evaluate the risk of infection with postoperative injection is needed to further elucidate our findings,” said Dr. Quinlan. “Further exploration into determining the driving factors for the increased incidence of postoperative injection of TKA over time would also be interesting. Finally, further studies to determine patient risk factors for developing an infection following a postoperative injection would be clinically relevant data.”
Dr. Quinlan’s coauthors of “Risk of Periprosthetic Infection Following Intra-Articular Corticosteroid Injections After Total Knee Arthroplasty” are Zoe Roecker, BS; James A. Browne, MD; and Brian C. Werner, MD.
Kaitlyn D’Onofrio is the associate editor for AAOS Now. She can be reached at email@example.com.
- Kew ME, Cancienne JM, Christensen JE, et al: The timing of corticosteroid injections after arthroscopic shoulder procedures affects postoperative infection risk. Am J Sports Med 2019;47:915-21.