# Safety of locally applied antibiotics in orthopaedic trauma surgery: descriptive results from a prospective cohort study

## TL;DR

This study shows that using antibiotics locally in orthopedic surgery is safe for kidney function, with low systemic absorption.

## Contribution

The study provides empirical evidence on the safety of local antibiotic application in orthopedic trauma surgery regarding nephrotoxicity.

## Key findings

- Gentamicin levels exceeded the LLOQ in 17% of surgeries but remained below toxic thresholds.
- Vancomycin levels did not surpass the LLOQ in any measurements.
- Antibiotic carrier type may influence systemic absorption and local release.

## Abstract

Antibiotic therapy holds an integral role in the prevention and treatment of fracture-related infection (FRI). Because local concentrations after systemic administration are limited by the potential for side effects, the local application of antibiotics serves as a valuable adjunct. One concern with the local administration of high amounts of aminoglycosides and vancomycin is the absorption into the systemic circulation, leading to detrimental effects on renal function. In this study, serum antibiotic concentration and renal function were measured in patients treated for open fractures or FRI using local antibiotics at 6, 24 and 48 h postoperatively. Afterwards, laboratory analyses were continued daily until the concentration dropped beneath the lower limit of quantification (LLOQ) (0.22 mg L−1 for gentamicin, 0.70 mg L−1 for vancomycin). Gentamicin concentration, vancomycin concentration and glomerular filtration rate were measured 272, 60 and 277 times in 52 patients after 82 surgeries, respectively. The LLOQ for gentamicin was exceeded in 14 surgeries (17 %, median concentration 0.3 mg L−1). The highest measured antibiotic level was 1.0 mg L−1, well below the generally accepted toxic trough level of 2.0 mg L−1. Although the total quantity of antibiotics delivered via beads was less than that provided by an antibiotic spacer, the use of beads more frequently yielded measurements exceeding the established threshold. None of the vancomycin measurements surpassed the LLOQ. The results of this study suggest that the current clinical use of locally applied antibiotics in orthopaedic trauma surgery is safe in the context of nephrotoxicity. The type of antibiotic carrier might affect local release and subsequent systemic absorption, which must be considered.