Author: Elizabeth Faulkner, King's College London, Final year (MBBS)
A basic knowledge of the wound closure techniques at a plastic surgeon’s disposal is a good starting point for students preparing for a plastic surgery placement.
Primary and secondary intention
A wound can heal either by primary or secondary intention. Both primary and secondary intention undergo the Four Stages of Wound Healing:
- First few hours
- Vasoconstriction, platelet plug and clot formation
- 24-72 hours
- Neutrophil infiltration and monocytes differentiate to macrophages
- 1-3 weeks
- Fibroblast proliferation, collagen production and angiogenesis
- +3 weeks
- Collagen fibrils become organised (cross-linked)
- The wounds’ dermal edges are re-approximated and held together e.g. with sutures, staples, steri-strips or surgical glue
- Delayed primary intention (sometimes referred to as tertiary intention) may be used if the wound is contaminated. Closure is usually delayed until day 4, when macrophages have formed a granuloma around any foreign material
- The wound edges are not re-approximated
- Thus, the wound heals from its base upwards. This requires the formation of granulation tissue across the wound bed, followed by the action of myofibroblasts to contact the wound edges
- Healing by secondary intention can result in a more visible scar
Skin grafts are layers of epidermis plus some or all of the dermis removed from one area of the body to cover a wound, burn or excision site located elsewhere on the body. Grafts depend on re- and neovascularisation from the wound bed.
Graft ‘take’ depends on:
- Graft adherence (via fibrin attachment)
- Revascularisation, which requires a well-vascularised wound bed. Thus, grafts are very rarely used to directly cover bone, cartilage or tendons
There are two main types of skin graft, split-thickness and full-thickness:
- The epidermis plus a variable amount of dermis is removed
- The graft is harvested with a Humby knife / power driven dermatome and the donor site heals spontaneously by epithelization
- Used for larger defects
- Split thickness grafts are more readily taken up by the host site, due to easier re- and neovascularise than full thickness grafts, however the trade-off is a poorer cosmetic and functional result.
- The epidermis and all of the dermis is removed
- The graft is harvested with a scalpel. The donor site is closed primarily or, if too large for primary closure, using a split thickness graft from another donor site.
- Used for smaller defects
- Full thickness grafts produce better cosmetic and functional results, as overall the graft contracts less than a split thickness graft. As a result, full thickness grafts tend to be preferred for sites such as the hands and face
- Full thickness grafts also have the benefit of better sensory return and that hair follicle transfer is possible
Unlike grafts, skin flaps contain their own blood supply. They can be sourced locally to the wound or distantly from it.
Flaps are typically classified in three ways. By:
Tissue composition of the flap
- Cutaneous, fasciocutaneous, muscle, myocutaneous, osteomyocutaneous
Donor site location
- The tissue is raised adjacently to the wound
- Local flaps are then further classified by their design (advancement, rotation, transposition)
- The tissue is raised from a nearby but not adjacent site, with the flap’s blood supply being retained e.g. via a pedicle
Free flap / free tissue transfer
- The tissue is raised from a distant location and not pedicled
- This requires the vessels the flap takes with it to be re-anastomosed using microvascular technique
- Free flaps are typically used for larger defects
- Random flap: Rely on blood supply from random cutaneous vessels
- Axial flap: Blood supply from named perforator arteries
The skill to know which techniques to employ in any given case is fundamental to the successful practice of plastic surgery. Indeed, it is the last surgical speciality defined, not by anatomical location, but the surgical techniques carried out.
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