Surgical wounds are created during medical procedures and include incisions made with a scalpel, punctures for a laparoscope or arthroscope, or excisional wounds fashioned for a biopsy.¹ There are 4 classifications of surgical wounds, often determined as part of, and included in, a preprocedural process, to better understand risk for surgical site infection. If the surgical and postoperative courses proceed without adverse events, the surgeon may close the surgical wound primarily with sutures or staples, and the wound will ideally resolve during recovery through the expected stages of tissue healing. However, wound care professionals understand that there are many contributing circumstances that determine any wound’s trajectory, and surgical wounds are no exception.¹

How Can Clinicians Classify Surgical Wounds?

The Centers for Disease Control and Prevention (CDC) created the following Surgical Wound Classification (SWC), often used as part of a preprocedural surveillance program to prevent surgical site infections (SSI)^1-3:

• Class 1/Clean: These wounds are usually closed primarily, are not infected, and do not involve significant inflammation. If a drain is necessary, the drain system must be considered closed. These wounds do not involve areas prone to high levels of microorganism colonization, such as the respiratory, alimentary, genital, or urinary tracts.^1,3 Risk for infection is usually less than 2%.³ An example of a Class 1 surgical wound is excision of a soft tissue mass on the arm with complete primary closure.
• Class 2/Clean-Contaminated: These types of surgical wounds may involve areas such as the respiratory, alimentary, genital, or urinary tracts, however, they do not typically have risk of unusual or unexpected contamination. Instead, these wounds are monitored under planned and controlled conditions.^1,3 Infection risk in this class is typically less than 10%.³ An example of a Class 2 surgical wound is creation of an ostomy without adverse event.
• Class 3/Contaminated: This class includes fresh, open wounds with an assumed level of contamination due to circumstances. These can also result from an error in sterile technique, accidental creation of a wound, or a leakage of gastrointestinal materials in the wound area. Additionally, incisions that result in acute inflammation (without purulence) are considered class 3 wounds.^1,3 The range of infection risk for class 3 surgical wounds is 13-20%, however those with gastrointestinal involvement possibly higher.³ An example of a Class 3 surgical wound would be surgery for an open, traumatic fracture.
• Class 4/Dirty-Infected: Class 4 wounds demonstrate devitalized tissue, and they most commonly result from microorganisms present in perforated viscera or in the operative field.^1,3 Contamination may already be present at the time of surgery that later results in postoperative infection.³ Risk for infection is around 40%.³ An example of a Class 4 surgical wound is one created for incision and drainage of a deep-space diabetic foot infection.

During the procedure, usually a preoperative assessment or “time out,” a clinician will determine the present level of contamination, and thus the SWC. Each organization’s exact algorithm may vary slightly, but the personnel (many times the surgeon, circulating nurse, or a combination of team members) will lead the identification and documentation of this assessment.¹ If events transpire intraoperatively that change this classification, this event should also be documented.

What Guidance Does the Surgical Wound Classification Provide?

The SWC supports the use of pre- and postoperative antibiotics depending on specific factors. For instance, dirty-Infected or Contaminated procedures do not usually necessitate preoperative antibiotic prophylaxis, since they likely require specific postoperative antibiotic therapy.⁴ Additionally, the surgeon may wish to hold preoperative antibiotics when indicated to aid in a more accurate deep wound or tissue culture.

Preoperatively, clean-contaminated procedures may warrant, at minimum, prophylactic coverage for Staphylococci, and possibly other organisms depending on the anatomic area in question.⁴ Pending facility protocol and patient factors, this prophylaxis could include weight-adjusted dosing of cefazolin or vancomycin, with the addition of metronidazole, ertapenem, or cefoxitin.⁴ In the operating room, additional prophylactic antimicrobial doses should not be administered after the surgical incision is closed in clean and clean-contaminated procedures, even in the presence of a drain.⁵

Understanding the risk stratification for each type of surgical wound may allow the surgical and postoperative team to make choices that align with SSI prevention tailored to their respective wound class. For instance, a clean, primarily closed surgical wound from a lower-risk procedure is less likely to necessitate specialized intervention. However, a contaminated or dirty surgical wound may spur the team to evaluate available choices that fit the particular case’s risk profile. Are antimicrobial dressings indicated? Might more frequent dressing changes be necessary?

Clinical Cautions to Keep in Mind

The main issue of concern with the current surgical wound classification scheme is that it has low inter-rater reliability among health care providers.² Additionally, this wound classification scheme has been shown to not work as effectively in neonatal surgical wounds. Clinicians should keep in mind that different tissue types and surgical approaches may warrant different viewpoints on the classification.⁶ Geographic, biologic, psychologic, and socioeconomic factors also play a role, as does the surgical site’s typical microbial community.⁶

Conclusion

The clinical significance of proper surgical wound classification lies in its ability to help predict the likelihood of SSIs, postoperative complications, and reoperation.⁶ Correctly classified surgical wounds also can potentially aid in assessing morbidity, mortality, and quality of life stratification.⁶ Patients receiving tissue grafts may also benefit from this classification scheme, as it can help evaluate the degree of bacterial contamination at the time of grafting and, by extension, the ability of that graft to heal correctly.⁶

Overall, the surgical wound classification alone should not guide perioperative or postoperative decisions, but could provide a valuable metric, in conjunction with multiple other factors, in determining risk of SSI and the optimal mitigation steps.

References

1. Centers for Disease Control and Prevention. National Healthcare Safety Network. Surgical Site Infection Event (SSI). Published January 2023. Accessed June 29, 2023.: https://www.cdc.gov/nhsn/pdfs/pscmanual/9pscssicurrent.pdf.
2. Onyekwelu I, Yakkanti R, Protzer L, Pinkston CM, Tucker C, Seligson D. Surgical Wound Classification and Surgical Site Infections in the Orthopaedic Patient. J Am Acad Orthop Surg Glob Res Rev. 2017:1(3):e022. doi: 10.5435/JAAOSGlobal-D-17-00022.
3. American College of Surgeons. Wound Home Skills Kit: Surgical Wounds. Accessed June 29, 2023. https://www.facs.org/media/zr5dimjk/wound_surgical.pdf.
4. Zabaglo M, Sharman T. Postoperative Wound Infection. In: StatPearls [Internet]. StatPearls Publishing; Updated September 19, 2022. Accessed January 2023. https://www.ncbi.nlm.nih.gov/books/NBK560533/
5. Berríos-Torres SI, Umscheid CA, Bratzler DW, et al. Centers for Disease Control and Prevention Guideline for the Prevention of Surgical Site Infection, 2017. JAMA Surg. 2017;152(8):784–791. doi:10.1001/jamasurg.2017.0904
6. Herman TF. Wound Classification. In: StatPearls [Internet]. StatPearls Publishing; Published April 24, 2023. Accessed June 29, 2023. https://www.statpearls.com/ArticleLibrary/viewarticle/34508.

Further Reading

Gorvetzian JW, Epler KE, Schrader S, et al. Operating room staff and surgeon documentation curriculum improves wound classification accuracy. Heliyon. 2018:4(8):e00728. doi: 10.1016/j.heliyon.2018.e00728.

Kamel C, McGahan L, Mierzwinski-Urban M, et al. Preoperative Skin Antiseptic Preparations and Application Techniques for Preventing Surgical Site Infections: A Systematic Review of the Clinical Evidence and Guidelines [Internet]. Ottawa (ON): Canadian Agency for Drugs and Technologies in Health; 2011. Accessed June 29, 2023.https://www.ncbi.nlm.nih.gov/books/NBK174534/.