Patients with obesity have a higher risk of periprosthetic joint infection and more frequent polymicrobial infections after knee arthroplasty: A nationwide register‐based study from Denmark
Saber M. Aljuboori, Espen Jimenez‐Solem, Henrik Calum, Robin Christensen, Søren OvergaardAbstract
Purpose
To compare the 2‐year incidence of (1) revision due to periprosthetic joint infection (PJI) and (2) all‐cause revision after primary knee arthroplasty (KA) in patients with/without obesity and to compare the microbial profiles in early (≤ 90 days) and late (91–730 days) PJI.
Methods
A nationwide, register‐based cohort of patients undergoing primary total or unicompartmental KA for osteoarthritis in Denmark (2011–2023). Patients were stratified by body mass index (BMI), with obesity defined as BMI ≥ 30 kg/m 2 . Cox proportional hazards models estimated hazard ratios (HRs) with corresponding two‐sided 95% confidence intervals (95% CIs) for PJI and all‐cause revision within 2 years. Analyses included crude and propensity score‐adjusted models based on health and socioeconomic data. Microbial profiles were compared using absolute risk difference (ARD) with 95% CIs in the early and late post‐operative periods.
Results
Among 111,117 eligible patients, 41,306 had obesity (mean BMI: 34.6) and 59,993 did not (mean BMI: 26.1). Patients with obesity were slightly younger and had higher use of glucose‐lowering medication. Patients with obesity had a higher risk of PJI revision than those without obesity (482 [1.2%] vs. 559 [0.9%]; crude HR: 1.25 [1.11–1.42], and propensity‐adjusted HR: 1.30, 95% CI: 1.14–1.48). The adjusted risk of all‐cause revision was comparable (1494 [3.6%] vs. 1893 [3.2%]; HR: 1.05, 95% CI: 0.98–1.13). Within 90 days, patients with obesity had more polymicrobial infections (62 [18.5%] vs. 43 [11.3%]; ARD: 7.2%, 95% CI: 2.0%–12.5%) and more non‐staphylococcal gram‐positive organisms (69 [21%] vs. 54 [14%]; ARD: 6.3%, 95% CI: 0.8%–12%). Staphylococcus aureus was the most frequent pathogen in both groups (127 [38%] vs. 136 [36%]; ARD: 2.0%, 95% CI: −5.1% to 9.1%).
Conclusions
Obesity was associated with an increased 2‐year risk of PJI after KA; however, the risk of all‐cause revision was comparable to that in patients without obesity. Within 90 days, patients with obesity exhibited a higher incidence of polymicrobial infections and non‐staphylococcal gram‐positive organisms.
Level of Evidence
Level II, prognostic studies—investigating natural history and evaluating the effect of a patient characteristic.