Effects of renal function on the intraosseous concentration and inhibitory effect of prophylactic cefazolin in knee arthroplasty.

OBJECTIVE To compare intraosseous concentrations and inhibitory effects on the growth of Staphylococcus aureus following intravenous administration of 1 or 2 g of the prophylactic cefazolin between patients with decreased renal function vs. intact renal function undergoing total knee arthroplasty. PATIENTS AND METHODS Ten patients (13 knees) with primary knee osteoarthritis were divided into two groups by creatinine clearance (CrCl) level (intact renal function: CrCl ≥75 mg/mL (four knees); decreased renal function: CrCl <75 mg/mL (nine knees)). Subchondral bone samples (proximal tibia and distal femur) were obtained during the procedure and were analyzed for the intraosseous concentration of cefazolin and the inhibitory effects on the growth of S. aureus using high-performance liquid chromatography and agar disc diffusion bioassays. RESULTS Different levels of renal function showed no significant associations with mean intraosseous concentration and mean inhibitory effects at the proximal tibia and distal femur in patients administered 1 g cefazolin (p>0.05). For patients administered 2 g cefazolin, mean intraosseous concentration in the decreased renal function group was significantly higher at the proximal tibia (p=0.049) and also higher (but not reaching statistical significance) at the distal femur (p=0.073) compared with the intact renal function group. Mean inhibitory effects in the decreased renal function group were significantly lower than the intact renal function group at the proximal tibia (p=0.003) and distal femur (p=0.003). CONCLUSIONS Deceased renal function played a role in the increased intraosseous concentration and decreased inhibitory effects in the groups receiving 2 g cefazolin. An excessive intraosseous concentration showed a negative influence on inhibitory effects on the growth of Staphylococcus aureus.