Flap surgery is a type of plastic and reconstructive surgery which involved flap, a unit of tissue] transfer from one site (donor site) to another (recipient site) while maintaining its own blood supply.
A graft is a transfer of tissue without its own blood supply. This feature differentiates the two terms.
Thus the graft survival depends on the establishment of circulation by growth of blood vessels at the recipient site but the flap carries its own blood supply.
Thus a flap is a portion of tissue that can be dissected, elevated, and inset into a nonanatomic position as a consequence of its vascular supply and outflow.
Flaps can be as simple as random pattern skin flap based on a subdermal plexus to a fascio-osteocutaneous free flap supplied by a known arterial perforator.
Sushruta Samita described nasal reconstruction using a cheek flap as early as 600 BC. The origins of forehead rhinoplasty may be traced back to approximately 1440 AD in India.
The term flap originated in the 16th century from the Dutch word flappe, meaning something that hung broad and loose, fastened only by one side.
Subsequent surgical flap evolution occurred in phases especially during the First and Second World Wars.
Perforator flaps or the flaps supplied by small vessels came into vogue during 1990s.
The discovery of the vascular anatomy of potential flap territories and the vascular patterns of skin blood supply has led to better understanding and use of the flaps which is practiced today.
Classification of Flaps
Classification according to blood supply
This classifies the flaps into random pattern and pedicle flaps. The vascular supply of a flap is known as its vascular pedicle. The term pedicle is also used to describe the base or attachment of a flap, which may also contain skin and other tissues as well as the vascular pedicle.
Some flaps have more than one vascular pedicle.
Where the skin is divided all the way around a flap it is called an island flap.
Random pattern flaps
There vascular basis of random pattern flaps is the subdermal plexus of blood vessels. These flaps are widely used for local repair of adjacent defects, particularly on the face.
The Z-plasty is a local flap technique that can be employed in a variety of situations, in particular treatment of contractures and scar revision. It involves the transposition of triangular flaps.
Axial pattern flaps
These are flaps with with a known direct superficial vascular pedicle passing along their long axis. Examples are
- Single vascular pedicle – Tensor fascia lata
- Dominant pedicle(s) and minor pedicle – Gracilis
- Two dominant pedicles – Gluteus maximus
- Segmental vascular pedicles – Sartorius
- One dominant pedicle and secondary segmental pedicles – Latissimus dorsi
Classification according to tissue to be transferred
Flaps may be composed of just one type of tissue or several different types of tissue.
Examples of single type of tissue include skin (cutaneous), fascia, muscle, bone, and visceral (eg, colon, small intestine, omentum) flaps.
Composite flaps include fasciocutaneous, containing fascia and skin (eg, radial forearm flap), myocutaneous (containing skin, subcutaneous tissue and muscleeg, transverse rectus abdominis muscle [TRAM] flap), osseocutaneous (eg, fibula flap), tendocutaneous (eg, dorsalis pedis flap), and sensory/innervated flaps (eg, dorsalis pedis flap with deep peroneal nerve).
In many parts of the body blood vessels pass along the deep fascia or, in association with intermusdularseptae, pass perforating vessels to supply the overlying skin. These flaps are raised along with the vascular pedicle by dissecting along the relevant fascial plane.
Fasciocutaneous flaps can be transferred loco-regionally, or used as pedicle flap.
Muscle and musculocutaneous flaps
Many muscles also have perforating vessels passing from their substance into the overlying skin. This enables musculocutaneous flaps to be designed. Musculocutaneous flaps based on the latissimus dorsi and rectus abdominis muscles are particularly useful in breast reconstruction.
Gluteus maximus and tensor fascia lata flaps are used for pressure-sore closure. Muscle flaps can be used as functional transfers where their nerve supply is left intact or reestablished at the recipient site as in rehabilitation of brachial plexus injury, anal incontinence and facial palsy.
Classification by Location of Donor Site
A flap is called local flap when the tissue may be transferred from an area adjacent to the defect. It may be described based on its geometric design or as it is advanced or both.
Pivotal (geometric) flaps include rotation, transposition, and interpolation.
Advancement flaps include single pedicle, bipedicle, and V-Y.
Local flaps are created by freeing a layer of tissue and then stretching the freed layer to fill a defect.
Regional or interpolation flaps are not immediately adjacent to the defect. Instead, the freed tissue “island” is moved over or underneath normal tissue to reach the defect to be filled, with the blood supply still connected to the donor site via a pedicle.
This pedicle can be removed later on after new blood supply has formed
Distant flap is when the tissue is transferred from an noncontiguous anatomic site (ie, from a different part of the body.
Distant flaps may be either with pedicle or transferred free.
Free flaps are physically detached from their native blood supply and then reattached to vessels at the recipient site by a microsurgical anastomosis.
It is more commonly known as free tissue transfer.
Thus a free flap has the blood supply cut and then reattached microsurgically to a new blood supply at the recipient site.
Free Tissue Transfer
Free tissue transfer is defined as the vascular dissection and detachment of an isolated and specific region of the body (eg, skin, fat, muscle, bone) and transfer of said tissue to another region , with anastomosis of the divided artery and vein to a separate artery and vein located at the site of the defect.
This anastomosis ensureres the perfusion and drainage, and ultimately the survival, of the flap.
The numerous advantages of this technique include
- Stable wound coverage
- Improved aesthetic and functional outcomes
- Minimal donor site morbidity
Free tissue transfer currently is used for the reconstruction of complex defects and disorders throughout the body.
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