Skin flap techniques

General technique

• Consider beforehand which structures are at risk and plan appropriately so the flap can be raised quickly.
• Err on the side of a larger flap rather than smaller
• Match the thickness of the flap to the defect, and definitely don't make it too thin - hard to fix
• Ensure reasonable haemostasis prior to closure - haematoma will kill the flap
• Use interrupted suture unless you are very confident with the type of flap
• The first suture approximates the donor site, then start at point of greatest tension, usually the leading edge of the flap
• Watch for blanching as you suture - sutures may need to be removed
• Prioritise avoiding tension rather than closing the wound - can leave part of it open rather than risk the whole flap

Bilobed flap

• Double transposition flap. First lobe fills the primary defect and second lobe fills the defect vacated by the first lobe.
• Distributes tension across a wider area.
• Technique
  • Mark prior to LA
    • Mark boundaries of excised lesion
    • First lobe directly superior - diameter 80-100% of the primary excision (in nasal excisions, needs to be 100%, as skin not very elastic)
    • Second lobe drawn immediately adjacent to first lobe, in the half past one o'clock position, 45 degrees off the vertical axis. This second lobe should have a 'hat' - to prevent standing cutaneous deformity.
  • Excision of primary lesion down to level of perichondrium (easier dissection and better perfusion)
  • Make rest of incisions
  • Wide undermining should be performed in a subdermal (if on nose - submuscular) plane
  • Close the tertiary defect, then the secondary defect, then the primary defect
• Complications
  • Trapdoor deformity - skin surface higher than the surrounding tissue. Occurs due to lymphatics and venous drainage is sometimes separated at the subdermal plane where the flap is rotated.

V-Y advancement island flap

• Excise lesion as circle, square or rectangle
• Flap will be a triangle 2-2.5x the length of the defeect
• Free the flap so it remains on the deep fascial pedicle, but dermis is incised ('island' flap)
• Advance the base of the flap to the far edge of the excision region
• Use three-point sutures at the two edges and the apex
• The stem of the Y should be about the same size as the original defect
• Suture the sides
• Thus the V island is converted to a Y-shaped scar

H double advancement flap

• This is useful on the forehead especially
• Excise the lesion as a square
• Extend the excision lines to about 1.5x the length of the defect
• Dissect two skin flaps from their subcutaneous tissue and advance them both to the midline

Rotation flap

• Mark excision as a circle
• Convert circle to an isosceles triangle, with width being 3x the lesion diameter
• Mark pivot point at apex of triangle
• Mark circumference
• Diameter should be at least 4-5x the size of the defect
• Rotation flap on the scalp can be in any direction, but you can try to design it so the scar will be at right angles to the fall of the hair, where it will be less noticeable
• On the scalp, cut down through skin and galea to get into the loose areolar plane between galea and periosteum. Expect bleeding from around the galea and subcutaneous layer, which is difficult to control with cautery. Control the major bleeders, but otherwise just operate quickly and start suturing.
• Full 180 degrees of mobilisation is generally necessary before it starts to move
• First suture is between the leading edge and the far side of the defect. There shouldn't be much tension - if there is, make a back cut, but make it as small as possible.
• If can't close -
  • make a back cut - moves the functional pivot point closer to the lesion, and will reduce closing tension, at the cost of worse blood supply
  • Undermine
  • Double rotation flap

Rhomboid (Limberg) flap

• Most useful where tension is in the wrong direction. Good for forehead, temple, scalp
• Since length:breadth <1, can be designed without regard for blood supply
• Ideally, internal angles of 60 and 120 degrees, but can vary this somewhat. Lengths of all four sides should be equal.
• A-G should continue the line of the short axis A-D, with both the same length
• B-G should be parallel to E-A
• Direction the skin comes from is determined by the availability of skin
• Ensure the donor site is able to be closed. If that is ok, the flap should be fine.
• If the closure is likely to be tight, can leave the little triangles of skin near point C and point D, as long as it doesn't compromise margins
• There is always a dog ear at E, which should generally be removed
• Undermining must go right to the base of the flap (E-B) or it won't mobilise enough
• Check haemostasis of donor site, underside of the flap and the defect prior to suturing
• Closure
  • Start with a suture to AB, allowing the flap to fall into the defect
  • Then close CD, the tightest point (if it won't close, may need more undermining, or closing the looser parts first to progressively pull the flap across)
  • Then close the rest

Keystone flap

• Island fasciocutaneous flap
• Good for use in leg where perforators and tissue will come from lateral to pre-tibial area - take advantage of perforators coming from the area of intermuscular septum

O to Z closure

• Double advancement flap, useful when tissue is available on two opposing sides of a circular defect
• The advancement flaps can be curvilinear or straight, depending on skin tension lines
• Can undermine the flaps for more reach but don't have to
• Commonly used on scalp
• The two opposing flaps can tolerate some asymmetry normally
• The formal technique is to mark out radiuses around the defect, with the lesion representing one radius. Start off with incisions reaching about 3 radiuses. If required, undermine at this point. If tension is still too high, increase in one-radius increments until tension is sufficiently reduced, up to an approximate maximum of 4 radiuses.
• It is often necessary to excise the points of the flaps, but this can be done at the end

Complications

• Arterial ischaemia
  • If the flap is healthy at the end of the procedure, it is unlikely to become ischaemic unless a haematoma develops
  • Some signs of ischaemia at end of case - review in two hours
    • White flaps go pink, blue flaps go black - largely, but not universally, true
    • Inspect entire flap, look for line of tension. If that is present, needs to be taken down and reworked. If not present, sutures need to be taken out that might be compromising supply. Reduce tension in any way possible - often by just removing sutures and placing less tension. If it still looks ischaemic after removing sutures, return it to its original position, which might improve things - the reconstruction may have failed but at least the defect won't be too large.
    • Prioritise covering vital structures and those areas of the wound that will not take a skin graft.
    • Final appearance is often surprisingly good even if sutures have to be taken out and part left to heal by secondary intention
• Venous insufficiency
  • Oedematous, brisk capillary return, bleeds briskly with pinprick
  • Consider leeches or bleeding out the flap with injection of heparin and allowing it to bleed, which may keep it alive for a few days until further connections form
• Haematoma
  • Generally causes pain, so the patient will re-present if this occurs
  • Prevents flaps from 'taking' in ways that are not fully explained by tension alone, so if detected, should be removed from under a flap. Usually, can take some sutures out and express the blood. May require operative haemostasis.
• Pain
  • Significant pain requiring more than paracetamol is unusual and may reflect haematoma
• Pincushioning
  • Mostly resolves with time
  • Regular frequent massage