Regional Prophylactic Vancomycin With Restricted Tourniquet Time in Primary Total Knee Replacement

Patients are assigned to one of two groups by chance (like a coin toss):

GROUP A - Will receive 15mg/kg based on actual body weight (maximum of 2g) of vancomycin via the systemic route at a rate of 15mg/kg as per hospital guidelines. Systemic IV vancomycin is given via a forearm vein, given over an infusion timed to finish immediately prior to surgery.

GROUP B - Will have the limb exsanguinated and an above knee tourniquet inflated to 300 mmHg. Immediately following tourniquet inflation, Group B will receive 500mg of vancomycin, via an EZ-IO intraosseous cannula. The vancomycin would be administered in 150ml of saline solution. The intraosseous cannula would be placed into the epiphysis of the proximal tibia. The tourniquet will be left inflated for 10 minutes following completion of the IORA injection then deflated.

Both Groups will receive weight-based dose of systemic cefazolin ( or alternative antibiotic if allergic to cefazolin 15 minutes prior to inflation of tourniquet. This ensures all patients in the study receive effective antibiotic prophylaxis regardless of randomization. Both groups of patients would then undergo routine prep and draping For both groups, Total knee replacement would then be carried out as normal and the tourniquet will be inflated for cementation of the implants.

TISSUE SAMPLES Ten (10) tissue samples will be taken from each patient, 6 'fat' samples and 4 'bone' samples. Each sample is very small, around the size of a pinhead. Bone samples will be taken from the femur only to ensure no direct contamination from the site of injection (tibia) In addition, drain samples will be taken from the intra-articular drain site to measure vancomycin concentration the morning following surgery.