Intra-articular injection of vancomycin after arthrotomy closure following gentamicin-impregnated bone cementation in primary total knee arthroplasty provides a high intra-articular concentration while avoiding systemic toxicity: a prospective study.

Background: This study aimed to elucidate the safety and intra-articular elution profiles of vancomycin and gentamicin bone cement in patients undergoing primary total knee arthroplasty (TKA), with a focus on serum safety thresholds and therapeutic efficacy.

Methods: Consecutive patients who underwent unilateral primary TKA were prospectively enrolled. The implants were fixed using gentamicin-impregnated bone cement, and after arthrotomy closure, 1000 mg of vancomycin suspended in 25 mL of normal saline was directly injected into the joint. Peripheral venous blood and drain fluid samples were collected 2, 8, and 24 h postoperatively. The serum and intra-articular concentrations of vancomycin and gentamicin were analyzed using liquid chromatography-tandem mass spectrometry within 24 h.

Results: Clinical data reflecting renal and liver function were recorded preoperatively, and at 24 and 72 h postoperatively. A total of 100 patients were included. At 2, 8, and 24 h postoperatively, the serum vancomycin concentration was 7.0 ± 2.0, 5.7 ± 1.8, and 3.6 ± 1.4 µg/mL, respectively, while the intra-articular concentration was 468.5 (interquartile range [IQR] 286.0 to 774.8), 139.5 (IQR 52.0 to 295.3), and 34.4 (IQR 22.2 to 56.8) µg/mL, respectively; 33.2 (IQR 19.5 to 80.5) mg vancomycin was lost in drainage fluid at 24 h postoperatively. For gentamicin, the overall intra-articular concentration was 70.4 (IQR 35.4 to 109.2), 33.8 (IQR 17.8 to 73.9), and 21.1 (IQR 12.2 to 36.0) µg/mL at 2, 8, and 24 h postoperatively, respectively, with an undetectable serum concentration. No cases of acute renal injury, liver injury, ototoxicity, or anaphylaxis were observed.

Conclusions: Intra-articular injection of 1000 mg vancomycin after arthrotomy closure combined with gentamicin-impregnated bone cement provided a therapeutic intra-articular concentration while avoiding systemic toxicity over the initial 24 h after primary TKA. Therefore, intra-articular vancomycin administration may offer a safer alternative to intravenous antibiotics, reducing systemic toxicity; however, further large-scale studies are necessary.

Trial Registration: ClinicalTrials. Gov (registration number: NCT05338021).