Antibiotics the day of surgery will be a dose of ampicillin IV (2g) and gentamicin IV (5mg/kg) within 120 minutes of surgery start time. Patients with penicillin allergy will receive vancomycin IV (1g) instead of ampicillin and patients with gentamicin/aminoglycoside allergy will receive ceftriaxone IV (2g) instead of gentamicin. Postoperative antibiotics in the absence of sepsis (see definition of sepsis below) will be <24 hours of IV antibiotics.