Renal safety of intraoperative local vancomycin powder application in orthopedic surgery: a retrospective analysis

Introduction: Topical vancomycin powder is increasingly used in orthopedic surgery to prevent surgical site infections (SSIs). While its efficacy is well established, data on systemic safety - particularly renal effects - are limited. Given vancomycin's known nephrotoxicity when administered systemically, we evaluated whether local intraoperative application affects short-term renal function. Methods: This retrospective single-center cohort included 50 adults who underwent orthopedic surgery with the application of intraoperative topical vancomycin powder (January-July 2024). Serum creatinine (SCr) and estimated glomerular filtration rate (eGFR) were measured preoperatively and at two routine postoperative time points. The primary endpoint was acute kidney injury (AKI) per KDIGO serum creatinine criteria; secondary endpoints were within-patient changes in SCr and eGFR. Prespecified subgroups were nephrotoxic concomitant medication (yes/no), application site (epifascial/subfascial), vancomycin dose ( $<$ 1000 vs. $\ge$ 1000 mg), and indication (aseptic/septic). Analyses used Wilcoxon signed-rank and Fisher's exact tests. Results: The most common applied dose was 1000 mg (48 %; median 1000 mg; range 500-4000). Postoperative labs were obtained at median day 1 and day 3. AKI occurred in $2/50$ patients (4 %), both stage 1; no stage 2-3 events were observed. Both AKI cases had concomitant exposure to potentially nephrotoxic medication; however, AKI incidence did not statistically differ across prespecified subgroups (nephrotoxic co-medication, application plane, dose category, indication; all $p>0.05$ ). Paired analyses showed minimal within-patient change in renal indices: eGFR exhibited no central shift from baseline at either time point, and serum creatinine showed no systematic postoperative increase. Conclusions: Local intraoperative vancomycin powder application was not associated with short-term renal impairment. These findings support its renal safety in orthopedic surgery. Prospective trials with pharmacokinetic monitoring are warranted to confirm long-term safety. Level of evidence: IV (retrospective case series).