Prosthetic joint injections (PJIs) are most likely to occur within the initial 12 months following total knee arthroplasty (TKA), according to study results published in JAMA Network Open.
Researchers at the University of Pennsylvania conducted a retrospective cohort study to evaluate the incidence and risk factors of postoperative PJIs among patients who underwent TKA. Patient data were sourced from the Veterans Affairs (VA) Corporate Data Warehouse, including demographic characteristics, medical diagnoses, procedures, microbiological culture and laboratory results, and prescribed medications. Patients (N=79,367) were included if they underwent elective primary TKA between 1999 and 2019 and had received care at the VA for at least 1 year.
The primary endpoint was incident hospitalization for PJI. The incidence of PJIs (per 10,000 person-months) was compared between 3 postoperative periods, including early (≤3 months), delayed (>3 to ≤12 months), and late (<12 months) PJI occurrence. To determine PJI risk factors for each postoperative period, the researchers used a piecewise exponential parametric survival model fit through Poisson regression. Within each period, the frequencies of gram-positive, gram-negative, fungal, polymicrobial, and culture-negative PJIs were compared using chi-square testing.
Among the study population, the median patient age was 65 (IQR, 60-71) years, most were men (94.8%), and most were non-Hispanic White (73.5%).
The researchers noted a total of 1599 incident PJIs, of which 627 (39.2%) occurred in the early, 356 (22.2%) in the delayed, and 616 (38.5%) in the late postoperative period. The incidence of PJIs was higher in the early (incidence rate ratio [IRR], 26.8; 95% CI, 24.8-29.0) and delayed (IRR, 5.4; 95% CI, 4.9-6.0, respectively) periods than in the late period (IRR, 1.3; 95% CI, 1.201.4).
Overall, 164 PJIs were gram-negative and 710 were gram-positive. The most commonly isolated pathogen for gram-positive and gram-negative PJIs was Staphylococcus aureus and Enterobacter, respectively. In addition, the rate of gram-negative PJIs was higher in the early postoperative period than in the delayed and late periods combined (15.4% vs 8.5%, respectively; P <.001).
In all postoperative periods, significant risk factors for incident PJI included hepatitis C virus infection, peripheral artery disease, and autoimmune inflammatory arthritis. Significant risk factors were also noted for individual postoperative periods, including autoimmune inflammatory arthritis for early PJIs (adjusted IRR [aIRR], 2.3; 95% CI, 1.5-3.5), high BMI (≥40 kg/m2) for delayed PJIs (aIRR, 2.7; 95% CI, 1.5-4.9), and anemia for late PJIs (aIRR, 2.2; 95% CI, 1.5-3.1).
Study limitations include potentially misclassified PJI outcomes, the predominance of men, the lack of data on comorbidity severity, and the possibility of residual confounding.
According to the researchers, “[E]mpirical gram-negative antibiotic therapy should be considered along with the usual gram-positive coverage for early PJIs.”
Disclosures: Multiple study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.
Weinstein EJ, Stephens-Shields AJ, Newcomb CW, et al. Incidence, microbiological studies, and factors associated with prosthetic joint infection after total knee arthroplasty. JAMA Netw Open. 2023;6(10):e2340457. doi:10.1001/jamanetworkopen.2023.40457
This article originally appeared on Infectious Disease Advisor