Effects of Applying Powdered Prophylactics Verses Intravenous Antibiotics Only on Post-operative Infection Rate

1. Subjects will be divided into three groups based on the procedure used for the application of antibiotics

2. No local antibiotics (control group): In this group, individuals will be subjected to peri-operative intravenous* antibiotics only

3. Gram positive antibiotic: In this group, gram positive (powdered vancomycin)+ will be applied to the site of surgery, before closure of the wound, along with peri-operative intravenous antibiotics*

4. Gram positive and gram negative: In this group, gram positive (powdered vancomycin) will be instilled on the site of surgery, before closing the wound, and gram negative antibiotic (gentamycin mixed with bone cement)+ will be used, along with peri-operative intravenous antibiotics* (only in cases of implant fixation).

• Intravenous antibiotic dosage: 1 pre-operative dose of Cefuroxime 1.5 gm and 2 post-operative doses of Cefuroxime 750 mg.

• Vancomycin and Gentamycin dosage: 500 mg of vancomycin powder will be used and in group 'c' gentamycin mixed with bone cement will be used along with vancomycin powder.

2. Sample size: Based on, finding at least 4% difference between the proportions of infections found in control (generally 5%, 4% in case of joint replacement) and case groups (1%) (proportions were assumed from literature and our institute records), a sample size of minimum 285 in each group (424 for joint replacement cases) will be considered for the observation to be significant at an alpha level of 0.05. This will give the study a minimum power of 80%.

Spine cases: Control = 143, Gram-P = 143; Trauma cases: Control = 143, Gram-P = 143; Joint replacement cases: Control = 424, Gram-P = 424, Gram-P+Gram-N = 424; Total = 1844; Where Control - Cases with intravenous antibiotic dose; Gram-P - Cases with intravenous antibiotic + local antibiotic (Vancomycin, acts against gram positive bacteria); Gram-N - Cases with intravenous antibiotic + local antibiotic (Vancomycin, acts against gram positive bacteria) + local Gentamycin cement (acts against gram negative bacteria). 3. Procedure: Sampling will be based on stratified procedure. The total sample will be divided into categories based on the type of surgery, which are spine, trauma and joint replacement. Subjects within each category will be randomly selected for the three antibiotic treatments. For this study, we will use computer software to generate restricted randomization to achieve balance between groups in size. Within this restricted randomization, single block random size will be used to ensure randomization within each group.