There is clinical equipoise about the question of whether antibiotic prophylaxis should be
given for a short period or an extended period of time as reflected by inconsistencies in
major guidelines, current practices at Canadian centers, and as concluded in the three
systematic reviews. There also is clinical equipoise on whether the addition of vancomycin to
routine cefazolin prophylaxis can further reduce s-SSI rates. A short duration of combined
antimicrobial prophylaxis can reduce side effects of exposure to antimicrobials such as
infections with C. difficile or emergence of resistance, but may also reduce the incidence of
s-SSIs. The objective of the eventual full scale study is to determine whether adding
vancomycin to cefazolin can reduce SSIs as well as whether short-term prophylaxis is as
effective as long-term prophylaxis. The rationale to conduct the proposed pilot study is to
assess the feasibility to conduct this factorial cluster randomized cross-over trial, the
adherence to the study protocol at each pilot site, the length of time to fill out the case
report forms, and to get reliable estimates of event rates for sample size calculation for
the main study