Wound closure

Techniques to close a surgical or traumatic wound include:

Primary closure
Skin flap
Skin graft
Secondary intention

Primary closure

Primary closure refers to direct apposition of wound edges.

Lesion is usually excised with an ellipse of surrounding skin to result in a flat scar.
The edges of the wound may be undermined (creating a plane at the level of the fat). This frees up the wound edges so that they can be stretched and brought together.
Sutures are then placed to close the wound and take the tension off as it heals.
It is often preferable to place two layers of sutures: one layer of dissolving sutures buried in the dermis; and then non-dissolving sutures under minimal tension to neatly oppose the epidermis.
For high tension wounds or wounds on fragile skin, special suture techniques may be used to spread tension along the wound edge.

Skin flap

Skin flap refers to a procedure where skin adjacent to the wound is moved to cover it. There are two main categories of flaps: sliding and lifting.

Sliding flaps include advancement, island pedicle and rotation flaps. In these flaps local tissue slides into the defect to be closed spreading the tension of the closure over a larger area and often allowing a change in direction of the tension vector.
Lifting flaps include transposition and interpolation flaps. These flaps are designed to lift adjacent tissue into the defect over the top of intact surrounding skin. Interpolation flaps are often performed in two stages (the flap is raised on a vascular pedicle and sutured into the defect and later, the pedicle is divided and inset into the defect). Classic examples of transposition flaps include the bilobed and rhombic flaps. The median forehead flap, melolabial and retroauricular flaps are common examples of interpolation flaps.

Skin graft

Skin graft refers to a procedure where skin is completely excised from another site, and sewn into the defect to patch the wound.

Full thickness skin graft: a piece of skin is excised down to the level of fat and therefore includes epidermis and the full thickness of dermis and adnexal structures such as hair follicles.
Split-thickness skin graft: skin is excised to level of superficial to mid dermis (ie more superficial and thinner than full thickness grafts).
Composite graft: contains full thickness skin and underlying tissue (e.g. cartilage).

Secondary intention healing

Secondary intention healing is where a wound is left open to heal by itself. Secondary intention healing may be preferred in the following situations.

Contaminated or infected wounds, as risk of infection is high if these wounds are sutured
If excessive swelling places tension on the wound
If there would be dead or empty space below the wound if it was sutured

These wounds take a lot longer to heal than sutured wounds. A wound around 2cm in size may take 4-6 weeks to heal.

Wounds healed by secondary intention often heal with a contracted scar, which may be larger and more noticeable than wounds which are sutured, however the final appearance can be superior to a sutured closure in certain situations. Best results occur if the wound is relatively superficial and in a concave site. Secondary intention is less desirable in the following situations.

Wounds larger than 3-4cm
Wounds located in skin creases (e.g. front of elbow, armpit) where contraction may result in reduced range of movement.
Convex surfaces.