Classification of Flaps

Authors: Liv Schöllhammer, MD, Frederik Gulmark Hansen, med.stud. and Magnus Balslev Avnstorp, MD

To simplify the classifications we listed the most common classifications into three categories.

1. Vascular supply (type of blood supply to the flap)
2. The tissue to be transferred (tissue layers included in the flap)
3. The geometrical design of the flap.

Vascular supply

The vascular supply is essential and a deciding factor in flap design, because the skin flaps must receive adequate blood flow to survive. 

• Arterial flap: Flap based on specific artery. The flap may include several tissue layers. Can be further subclassified as axial-, perforator- or free flap
• Axial flap: Blood supply based on a named artery. Runs in the subcutaneous tissue superficial to muscle, i.e., the supratrochlear artery for the paramedian forehead flap.
• Perforator flap: Blood supply based on a named arteria perforating a muscle and reaching the overlying tissues, i.e., the deep inferior epigastric artery and venae which perforates through the rectus muscle for the DIEP flap.
• Free flap: The artery and vein is cut and the flap is moved to another anatomical region, connected/anastomosed using microsurgery to a new artery and vein at the recipient site. (ie. ALT flap to reconstruct tissue on lower leg).
• Random flap: Blood supply based on interconnecting subdermal plexuses derived from the deeper musculocutaneous arteries

Tissue to be Transferred

A flap can be classified according to the layers of tissue in the flap. The flap can consist of one type of tissue (e.g., skin, muscle, visceral) or several types of tissue (composite flaps). 

• Random Skin flap: The flap consists of the skin and a layer of subdermal tissue with blood supply depending on random subdermal plexuses. (ie. Nasolabial flap)
• Direct cutaneous arterial flap (An axial flap): The flap consists of the skin, subdermal plexuses and is based on a named subcutaneous artery running parallel to the skin (ie- paramedical forehead flap).
• Fasciocutaneous flap (An axial or a perforator flap): The flap contains skin, subdermal tissue and the fascia, making it a composite flap. 
• Musculocutaneous flap (An axial or a perforator flap): The flap contains skin, subdermal tissue and the muscle, making it a composite flap. It may be based on a single or several perforators.

The Geometrical design

The geometrical flap design includes flaps such as rotation-, transposition- and advancement flaps.
To read about the design, the practical use and to see cases of the specific flaps – please proceed to the chapters in the left hand menu.

Acknowledgements

Illustrators: Emma Tubæk Nielsen, med.stud.