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Author(s): Lynette E. Franklin, APRN, ACNS-BC, CWOCN-AP, CFCN

Any disruption in the skin and underlying structures is considered a wound. Humans typically heal along a “programmed” cascade when there is an acute injury. The extent and type of damage—as well as other intrinsic factors, such as patient circulation, nutrition, and hydration—influence the rate of wound repair. Wounds can heal, or close, through a series of phases. The closure of the wound also dictates how it will heal. There are 4 types of wound closures: primary, secondary, tertiary intention, and epithelization.

Primary intention

Wounds that heal through primary intention usually don't involve the loss of tissue. These wounds are closed with sutures or staples at the time of surgery, closing all layers of tissue. Examples include surgical wounds, superficial traumatic wounds, and first-degree sunburn.

Clean incisionEarly sutureHairline scar

Wound has well-approximated edges.Clean edges can be pulled together neatly.Because there's no loss of tissue and little risk of infection, these wounds usually heal in 4 to 14 days and result in minimal scarring.

Secondary intention

A wound that involves some degree of tissue loss heals by secondary intention. These full-thickness wounds fill in from the bottom with granulation tissue and then epithelize and scar. Pressure ulcers, burns, dehisced surgical wounds, and traumatic injuries are examples of this type of wound. These wounds take longer to heal, result in scarring, and have a higher rate of complications than do wounds that heal by primary intention.

Gaping irregular woundGranulationEpithelium growth over scar

Edges can't be easily approximated.Wound fills with granulation tissue.A scar forms, and reepithelialization occurs, primarily from the wound edges.

Tertiary intention

Wounds are sometimes left open for several days to allow edema or infection to resolve or for exudate to drain. These wounds heal by tertiary intention, also known as delayed primary closure. After the problem resolves, these wounds are closed with sutures or some other type of skin closure.

Open woundIncreased granulationLate suturing with wide scar

Wound is intentionally kept open (typically for 3 to 5 days) to allow edema or infection to resolve or to permit removal of exudate.Wound fills with granulation tissue.Wound is sutured late, and a wide scar results.

Epithelization

In this final process of wound healing, epithelial cells migrate across the wound bed. For partial-thickness wounds, those involving only the top layers of the skin (superficial dermis and epidermis), this is the primary method of healing. For example, with a knee abrasion, wound contracture and filling in with granulation tissue will not occur.