The impact of pathogen sensitivity to antibiotics loaded in cement on the number of revisions and costs in the treatment of periprosthetic knee infection.

Objective: This study aims to evaluate the impact of the pathogen's sensitivity to the loaded antibiotics on infection resolution, the number of revisions, and the associated costs in patients undergoing revision total knee arthroplasty (rTKA) due to PJI.

Material And Methods: We reviewed the treatment and follow-up processes of 61 patients who underwent rTKA for late-stage PJI following primary total knee arthroplasty in our clinic. The study included 11 patients in the resistant group and 50 in the sensitive group in line with the power analysis results. Patients' demographic characteristics and comorbidities were recorded. All patients received dual antibiotic-loaded cement. Microbiological examinations of patients were analyzed, and the number of revision surgeries each patient underwent was determined. We analyzed all surgeries related to infection treatment, including open irrigation, debridement, polyethylene exchange, implant extractions, antibiotic-loaded cement spacer placements, spacer changes, and debridements, and the implantation of revision prostheses, including tumor prostheses. The total number of surgeries each patient underwent was recorded. We also reviewed hospital system records of total protocol costs during patient admissions.

Results: Of 61 patients undergoing revision total knee arthroplasty (rTKA) for periprosthetic joint infection, 11 had antibiotic-resistant infections and 50 had antibiotic-sensitive infections. The groups had similar demographics. Polymicrobial infections were more frequent in the resistant group (p = 0.017), with all resistant cases showing gentamicin resistance and two showing teicoplanin resistance. The resistant group required more surgeries (average 3.91 ± 2.7 vs. 2.34 ± 1.3, p = 0.043) compared to the sensitive group, with teicoplanin resistance doubling revision surgeries (p = 0.005). Costs were similar between groups, averaging $6536.96. Gram-negative infections led to more revisions (p = 0.013). Polymicrobial infections did not significantly affect the number of surgeries or costs compared to single strain infections.

Conclusions: Our study demonstrates that in rTKA surgeries using dual antibiotic-loaded bone cement, infections caused by antibiotic-resistant microorganisms are more challenging and time-consuming to treat. This underscores the necessity of exploring new methods to enhance local efficacy by loading cement with antibiotics based on specific pathogen culture and sensitivity results, while also providing clinical evidence of the effectiveness of current treatment methods against sensitive microorganisms.

Level Of Evidence: Level 3 (a retrospective cohort study).