Why Wound Classification Matters
Surgical wounds are classified at the end of every procedure to standardize infection risk assessment, guide antibiotic decisions, and support national surgical site infection (SSI) surveillance data. The circulator typically documents the classification based on intraoperative findings and communicates it during the surgical count/documentation process.
Class I - Clean
| Criteria | Detail |
|---|
| Definition | Uninfected wound with no inflammation; respiratory, GI, GU, and biliary tracts are not entered |
| Examples | Elective hernia repair, breast biopsy, joint replacement (no infection present) |
| Infection risk | Approximately 1-5% |
| Closure | Primary closure; closed drainage if needed |
Class II - Clean-Contaminated
| Criteria | Detail |
|---|
| Definition | Respiratory, GI, GU, or biliary tract entered under controlled conditions with no unusual contamination |
| Examples | Elective cholecystectomy, appendectomy without rupture, elective bowel resection with adequate preparation |
| Infection risk | Approximately 5-10% |
Class III - Contaminated
| Criteria | Detail |
|---|
| Definition | Open, fresh accidental wounds; major break in sterile technique; gross spillage from GI tract; entry into acutely inflamed tissue without pus |
| Examples | Penetrating trauma less than 4 hours old, gross GI spillage during bowel surgery, entering the GU tract with infected urine |
| Infection risk | Approximately 10-20% |
Class IV - Dirty/Infected
| Criteria | Detail |
|---|
| Definition | Old traumatic wounds with retained devitalized tissue; existing clinical infection; perforated viscera present before the procedure |
| Examples | Perforated bowel with peritonitis, abscess drainage, penetrating trauma more than 4 hours old |
| Infection risk | Approximately 20-40% or higher |
| Closure | Often left open (delayed primary closure or healing by secondary intention) |
Wound Healing Terminology
- Primary intention - wound edges are approximated and closed at the time of surgery; minimal scarring, fastest healing.
- Secondary intention - wound is left open to heal by granulation, contraction, and epithelialization; used for infected or heavily contaminated wounds.
- Tertiary intention (delayed primary closure) - wound is intentionally left open for several days to allow inflammation/infection to resolve, then closed surgically.
Key Exam Points
- Classification is assigned based on conditions found during surgery, not the preoperative diagnosis alone.
- Higher wound class generally correlates with higher likelihood of postoperative antibiotic therapy and delayed or secondary closure.
- A ruptured appendix converts an otherwise Class II case into Class III or IV depending on contamination and infection present.
- Wound classification is one of several factors (along with ASA class and procedure duration) used in SSI risk-adjusted surveillance models such as the NHSN risk index.