Surgery: Skin Grafts and Flaps

Skin Grafts and Flaps

• Skin grafts and skin flaps are two surgical techniques used to close defects that cannot be closed by primary or secondary intention.
• The key difference between a graft and a flap is the blood supply:
  • Skin grafts receive blood supply from the recipient site through the vascular bed.
  • Skin flaps bring their blood supply from the donor site.

Skin Grafts

• Skin grafts have no blood supply and depend on the vascularized bed where they are placed.
• Used for extensive skin damage, such as deep burns, large skin excision procedures, or poorly healing ulcerating lesions.
• Considerations for choosing a donor site:
  • Amount of skin required
  • Color and texture of the donor skin
  • Hair growth required at the recipient site
• Two types of skin grafts:
  • Split-skin thickness skin graft (SSG): Does not contain the whole dermis.
  • Full-thickness skin graft (FTSG): Contains the whole dermis (including hair follicles).

Skin Graft Failure

• Skin grafts must heal by developing a new blood supply.
• Failure can occur due to:
  • Haematoma or seroma formation under the graft
  • Infection (commonly Streptococcus spp.)
  • Shearing forces
  • Unsuitable bed
  • Technical error
• Signs of graft failure:
  • Pallor or discoloration at the graft site
  • Evidence of localized infection
  • Systemic features (malaise, lethargy)
  • Full-thickness necrosis (occurs 1-2 weeks after grafting)

Skin Flaps

• Skin flaps are tissue transferred from a donor site to recipient site along with its corresponding blood supply.
• Provide better cosmetic results than skin grafting, with a reduced chance of failure.
• Classification:
  • By tissue type: Cutaneous flap, fasciocutaneous flap, musculocutaneous flap, or muscle flaps.
  • By blood supply: Axial flap, random flap, pedicled (or perforator) flap.
  • By location: Local, regional, or free flaps.

Types of Flaps

• Local flaps:
  • Harvested from a contiguous site
  • Used for facial defects, fingertip injuries, or defects on the limb
  • Further classified into:
    • Advancement flap: The skin is moved directly forward.
    • Rotation flap: The skin is rotated around a pivot point to cover an adjacent defect.
    • Transposition flap: Moves laterally in relation to the pedicle to cover an adjacent defect.
• Regional (or pedicled) flaps:
  • Harvested from the same anatomical region but not directly adjacent.
  • Attached skin (or pedicle) is tunneled under the intact tissue or laid over intact skin forming a skin bridge.
• Free (or distant) flaps:
  • Harvested from a different anatomical region entirely.
  • Tissue and named fasciocutaneous artery are separated from the donor site before being reattached at the recipient site using microsurgical techniques.

Flap Failure

• Extrinsic factors:
  • Haematomas under the flaps
  • Wound infection
  • Systemic hypotension
  • Tension of the flaps
  • Cigarette smoking
• Intrinsic factors:
  • Inadequate arterial inflow
  • Inadequate venous drainage
  • Arterio-venous shunting.