gms | German Medical Science

Objectives: Vancomycin soaking of the anterior cruciate ligament (ACL) graft drastically reduces the rate of postoperative septic knee arthritis after ACL reconstruction and is on its way to becoming gold standard. However, the systemic effects and elution characteristics of vancomycin from tendons in vivo remain unclear. Therefore, the aim of the study was to examine the serum vancomycin levels over 48 h after ACL reconstruction. We hypothesized that low doses of vancomycin would be detectable in peripherally drawn blood samples following implantation of the soaked graft, with peak serum levels measured within the first hour after tourniquet release.

Methods: A prospective study was conducted with a total of 17 patients undergoing ACL reconstruction using hamstring or quadriceps tendon autografts soaked in 5 mg/ml vancomycin. All patients received 2 g of cefazolin as intravenous perioperative antibiotic prophylaxis. A total of seven blood samples were taken per patient. One before the surgery, the second after the administration of cefazolin, the third 10 min after opening the tourniquet, and one each 1 h, 6–8 h, 24 h and 48 h later. Time between vancomycin soaking and transplantation was measured. The samples were analyzed for the concentration of vancomycin using tandem mass spectrometry (MS/MS) and high-performance liquid chromatography (HPLC). Spearman rho correlation coefficients were used to identify relationships between the parameters. A p-value of < .05 was considered statistically significant.

Results and conclusion: The study included 16 patients (12 men and 4 women; 37.5 ± 9.1 years). There was one drop-out due to hemolyzed blood samples. The mean graft diameter was 8.46 ± 0.72 mm, and mean Body Mass Index (BMI) was 26.1 ± 4.1. Vancomycin concentrations of 0.0039 ± 0.0096 µg/ml were measured immediately after tourniquet release. The highest mean vancomycin concentration of 0.0142 ± 0.0188 µg/ml was measured after 24 h. After 48 h a concentration of 0.0077 ± 0.0144 could still be detected. The maximum serum concentration of vancomycin in all samples was 0.704 µg/ml, determined in a sample taken 6–8 h after graft implantation. No significant correlation was found between serum vancomycin concentration and BMI, graft diameter, age or time between soaking and transplantation.

Vancomycin is detectable in peripheral blood samples following ACL reconstruction with soaking of the graft in a 5 mg/ml solution. However, the detected concentrations are significantly lower than the therapeutic serum concentrations of 15 µg/ml. The highest mean concentrations were reached after 24 hours. Given a half-life of 6–12 hours, this provides strong evidence that the soaked graft continues to release vancomycin to the surrounding tissue after implantation. This sponge effect may contribute to the efficacy of vancomycin-soaked grafts in the prophylaxis of postoperative infections.