Surgical site infection classes
I Clean wound–75% of all surgery; nontraumatic wound; noninflamed; no break in technique; no entry into the GI, GU, respiratory tracts, or oropharynx; infection rate < 5%, usually ±1%
II Clean-contaminated wound; minimal break in surgical technique; infection rate < 10%
III Contaminated wound: open, fresh, traumatic wound from relatively clean source, or major break in surgical technique; infection rate < 20%
IV Dirty and/or infected wound with devitalized and/or necrotic tissue; infection rate 30–40%