Higher Cefazolin Concentrations with Intraosseous Regional Prophylaxis in TKA

BACKGROUND: Prophylactic antibiotics reduce the risk of deep infection after primary TKA. However, conventional systemic dosing may not provide adequate tissue concentrations against more resistant organisms such as coagulase-negative staphylococci. Regional intravenous administration of antibiotics after tourniquet inflation achieves far higher tissue concentrations but requires foot vein cannulation. The intraosseous route may offer a rapid and reliable method of regional administration. QUESTIONS/PURPOSES: We compared tissue concentrations of cefazolin achieved with systemic versus regional intraosseous administration. METHODS: Twenty-two patients undergoing primary TKA were randomized into two groups. Group 1 received 1 g cefazolin systemically 10 minutes before tourniquet inflation. Group 2 received 1 g cefazolin intraosseously in 200 mL of normal saline through a tibial cannula after tourniquet inflation and before skin incision. Subcutaneous fat and femoral bone samples were taken at set intervals during the procedure and antibiotic concentrations measured using a validated technique involving high-performance liquid chromatography. RESULTS: The overall mean tissue concentration of cefazolin in subcutaneous fat was 186 ug/g in the intraosseous group and 11 ug/g in the systemic group. The mean tissue concentration in bone was 130 ug/g in the intraosseous group and 11 ug/g in the systemic group. These differences were consistent across all sample time points throughout the procedure. CONCLUSIONS: Intraosseous regional administration can achieve concentrations of antibiotic in tissue an order of magnitude higher than systemic administration. Further work is required to determine if this translates into increased efficacy in preventing infection, particularly against coagulase-negative staphylococci.