Influence of the ischaemic tourniquet in antibiotic prophylaxis in total knee replacement

There is level iv evidence that the preoperative administration of antibiotics helps in the prevention of prosthetic infection. There is controversy on whether the ischemia applied during surgery may affect the minimum inhibitory concentration of the antibiotic in the peri-prosthetic tissues. The aim of this study is to review this phenomenon through the determination of antibiotic concentration in the synovial tissue.

A prospective observational clinical study was conducted on 32 patients undergoing total knee replacement. Cefonicid 2g was administered as prophylaxis, with a tourniquet used for all patients. The antibiotic concentration was quantified by high performance liquid chromatography in samples of synovial tissue collected at the beginning and at the end of the intervention.

The mean concentration of antibiotic was 23.16 μg/g (95% CI 19.19 to 27.13) in the samples at the beginning of the intervention and 15.45 μg/g (95% CI 13.20 to 17.69) in the final samples, being higher than the minimum inhibitory concentration of cefonicid, set at 8 μg/g. These results were statistically significant for both concentrations (P<.00001).

The antibiotic concentration throughout the standard total knee prosthesis surgery performed with tourniquet gradually decreases throughout the intervention. The concentration determined at the end of the intervention was higher than the minimum inhibitory concentration required for the antibiotic studied. In conclusion, the use of a tourniquet does not increase the risk of infection.