**4. Wound classification**

Surgical wounds are commonly classified according to the degree of contamination and breaching of the aerodigestive tract epithelium into four categories:

A. Clean

**Growth factor Abbreviation Main origins Effects** 

346 Wound Healing - New insights into Ancient Challenges

PDGF Platelets

FGF-1, -2 Macrophages

TGF-β Platelets

**Table 1.** Various growth factors involved in wound healing [10].

Mast cells T-lymphocytes Endothelial cells Fibroblasts

T-lymphocytes Macrophages Endothelial cells Keratinocytes Smooth muscle cells

Fibroblasts

TGF-α Activated macrophages T-lymphocytes Keratinocytes

> Macrophages Endothelial cells Smooth muscle cells Keratinocytes

EGF Activated macrophages Keratinocyte and fibroblast mitogen

HGF Mesenchymal cells Epithelial and endothelial cell proliferation

VEGF Mesenchymal cells Vascular permeability

Keratinocyte migration Granulation tissue formation

Hepatocyte motility

Endothelial cell proliferation

muscle cell chemotaxis

hyaluronan production

Fibroblast chemotaxis

Keratinocyte migration

Integrin expression regulation

proliferation

Angiogenesis Wound remodelling

Angiogenesis Wound contraction

TIMP synthesis Angiogenesis Fibroplasia

KGF Keratinocytes Keratinocyte migron and differentiation

Keratinocyte proliferation

Hepatocyte and epithelial cell proliferation Expression of anti-microbial peptides Expression of chemotactic cytokines

Granulocyte, macrophage, fibroblast and smooth

Granulocyte, macrophage and fibroblast activation Fibroblast, endothelial cell and smooth muscle cell

Matrix metalloproteinase, fibronectin and

Fibroblast and keratinocyte proliferation

Matrix (collagen fibres) deposition

and smooth muscle cell chemotaxis

Granulocyte, macrophage, lymphocyte, fibroblast

Matrix metalloproteinase production inhibition

Epidermal growth

Transforming growth

Hepatocyte growth

Vascular endothelial growth factor

Platelet-derived growth factor

Fibroblast growth factors 1 and 2

Transforming growth

Keratinocyte growth

factor-β

factor

factor

factor-α

factor

Uncontaminated wounds without breaching of the respiratory, gastrointestinal (GI) or genitourinary (GU) tract. Examples include mastectomy, neck dissection, thyroid surgery and hernia surgery. These wounds are commonly managed with primary closure.

### B. Clean-contaminated

Gastrointestinal, respiratory or Genitourinary tracts are entered in a controlled fashion. Usually no gross contamination or spillage should happen if proper precautions, i.e. minimising spillage, protecting the wound edges, etc., are taken. Examples of these types of wounds include cholecystectomy, Whipple operation, elective colonic or gastric surgery.

C. Contaminated

Any gross spillage of GI tract contents or major breach in the sterile technique either as causative agent or accidental can lead to contamination of wound. Perforated appendicitis, bile spillage, diverticular perforation or penetrating wounds come within this category. Although primary closure is still feasible in these wounds, thorough washout with copious amount of saline to remove as much contaminating agent, i.e. faeces or pus, as possible and prophylactic intra-operative antibiotics are advisable. Most randomised controlled trials (RCTs) prove the reduction in major sepsis though minor wound infection may still occur. In cases of gross contamination of abdominal cavity with faecal matter and when one is not sure of complete removal of contaminating agent it is better to leave the abdomen open and covered with wet packs for 48 hours and then re-checking the abdomen under general anaesthetic by removing the pack. If the abdominal cavity looks clean and there is no dead tissue or bowel then the closure can be attempted. These wounds are best closed in one layer with whole thickness sutures with either nylon or prolene as tension sutures.

## D. Dirty wounds

This refers to old traumatic wounds with necrotic tissue, ongoing infection or perforation and presence of known organisms in the wound prior to intervention. Primary closure is not advisable and debridement is essential. Examples include abscesses, perforated bowel and faecal peritonitis. In cases of gross contamination of abdominal cavity with faecal matter and when one is not sure of complete removal of contaminating agent it is better to leave the abdomen open and covered with wet packs for 48 hours and then re-checking the abdomen under general anaesthetic by removing the pack. If the abdominal cavity looks clean and there is no dead tissue or bowel then the closure can be attempted. These wounds are best closed in one layer with whole thickness suture with either nylon or prolene as tension sutures.

Techniques of wound closure:

A. Closure by primary intention

In this technique, approximation of wound edges and deeper tissue layers is meticulously carried out with appropriate sutures in layers. Skin is approximated by sub-cuticular sutures or staples. Sterstrips™ are used to relieve tension on suture line and to give more aesthetically pleasing and functional scar. Elimination of dead space minimises new tissue formation, and careful epidermal alignment minimises scar formation [11, 12].

B. Closure by secondary intention

This is considered an adequate alternative to primary intention closure, particularly in cases where major tissue loss or gross contamination is expected. It might include closure of deeper facial planes while leaving the skin open [13].
