Day-one local fluid and serum antibiotic concentrations after vancomycin-gentamicin PMMA coating of tibial intramedullary nails: an observational series
DOI:
https://doi.org/10.68819/Keywords:
antibiotic-loaded bone cement, gentamicin, intramedullary nail, local drug delivery, polymethylmethacrylate, tibial fracture, vancomycinAbstract
Background: Antibiotic-loaded polymethylmethacrylate (PMMA) coatings provide a means of delivering antimicrobials near intramedullary implants. Human data relating the gentamicin quantity incorporated into the coating to local fluid and serum concentrations remain limited.
Methods: Thirty patients with vancomycin (2 g)-containing PMMA-coated tibial nails were evaluated according to incorporated gentamicin dose: 0.5 g (n=9), 1 g (n=14), or 2 g (n=7). Patient-level day-one fluid and serum antibiotic measurements, concomitant systemic antibiotics, recorded adverse events, and deep infection at six months were assessed. Group comparisons used Kruskal–Wallis tests; dose associations were assessed using Spearman correlation. The analysis was exploratory.
Results: Mean (SD) local fluid concentrations were 1172.7 (138.3) mg/L for vancomycin and 434.8 (241.0) mg/L for gentamicin. Gentamicin concentrations were 202.0 (22.5), 388.1 (57.0), and 827.2 (83.9) mg/L across increasing PMMA gentamicin doses (Kruskal–Wallis P<0.001; Spearman ρ=0.927). With vancomycin loading fixed, local vancomycin concentrations decreased across the same groups (ρ=−0.475; P=0.008). Mean serum measurements were 1.80 (0.35) µg/mL for vancomycin and 0.60 (0.15) µg/mL for gentamicin. Thirteen patients also received systemic gentamicin. Deep infection was recorded in two patients (2/30; 6.7%), both in the 0.5-g group (2/9 vs 0/21; Fisher P=0.083). One patient had recorded acute kidney injury; no ototoxicity or local allergic reaction was recorded.
Conclusions: Greater gentamicin loading was strongly associated with higher day-one local gentamicin concentrations, without an observed serum dose gradient. Local and serum measurements differed substantially. These findings describe early measured concentrations but do not establish sustained elution, comparative infection prevention, or absence of systemic toxicity.
