Flaps

More complex defects and avascular defects require flap cover. Flaps can consist of skin only, or be complex compos­ites of skin, muscle, bone or other tissues. As their complexity increases so do their power and ability to reconstruct more complex defects. Flaps can be classified according to the geometry of their transfer such as rotation, advancement or transposition. A more useful classification is provided by their vascular basis. The vascular supply of a flap is known as its vascular pedicle; some flaps have more than one 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. Where the skin is divided all the way around a flap it is called an island flap.

2Flaps from the cheek and forehead were used in India as early as 1000 ec for nasal reconstruction. Tagliacozzi in 1597 published his method using flaps from the arm. Multitudes of flaps were utilised in the nineteenth century. Tansini in 1896 described the latissimus dorsi flap for breast reconstruction. The significance of the vascular basis of these flaps was not appreciated during the development of modern plastic surgery after World War land World War II.

The development of flap surgery

Flaps have been used since ancient times, often to repair complex defects2. In the first half of the twentieth century, however, the only flaps that were considered possible were skin flaps consisting of rectangular portions of skin and subcutaneous tissue with length to breath ratio of 2 to 1.5:1. Such flaps were of limited arc of transfer and their use to reconstruct distant defects involved multistage surgery. Bipedicled flaps were tubed to form tubed pedicle flaps that were attached to an arm carrier and then transferred in several stages using multiple delays to a recipient site. It was possible to perform complex reconstructions using these methods, but each stage risked vascular compromise and flap loss, and donor site scarring was considerable. This all took a long time and such flaps, when the transfer was completed, depended on the local vascularity of the recipient site and did not bring in an independent blood supply of their own. Modern flap practice has developed since the discovery of the vascular anatomy of potential flap territories and the vascular patterns of skin blood supply.

Random pattern flaps

The 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. Many geometric designs are possible. A particularly useful pattern is a rhomboid flap (Fig. 13.4a—d). 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. A Z­plasty or a combination of Z-plasties can lengthen a contracture, change the direction of a scar, alter tension, reposition specialised structures and improve the appearance of a scar (Fig. 13.5). It involves the transposition of triangular flaps. The maximum lengthening is achieved by using 600 angles of flap design. Lengthening depends on laxity at right angles to the contracture since it occurs at the expense of shortening in a perpendicular direction.

  Axial pattern flaps

Skin flaps with a known direct superficial vascular pedicle passing along their long axis are known as axial pattern flaps. These defy previously accepted length-to-breadth ratios that applied to random pattern flaps and thereby long flaps can reliably be designed with longer axes of rotation3. The forehead flap, the deltopectoral flap and groin flap all share this vascular pattern.

  31n a series of experiments in the I 960s raising flaps in pigs, Milton discovered that flaps made under similar conditions survive to the same length regardless of width. He realised that the most important factor was including a dominant vessel in the pedicle. He further discovered that islanded flaps with a segmental vessel in their base survived to a greater length than random skin flaps. Thus, he predicted the flap revolution that was about to occur.

FasciocutaneoUS flaps

In many parts of the body blood vessels pass along the deep fascia or, in association with intermusdular septae, pass perforating vessels to supply the overlying skin. These flaps are raised along with the vascular pedicle by dissecting along the relevant fascial plane. Long vascular pedicles can be created, often with quite large vessels at their base. Fasciocutaneous flaps can be transferred loco-regionally, or the vascular pedicle divided, the flap transferred to a distant site and the flap revascularised by microsurgical anastomosis to recipient vessels adjacent to the defect. This technique of free tissue transfer has further extended the versatility of flap reconstruction. Fasciocutaneous flaps can be skin only or can include associated tissue to provide vascularised bone or nerve. Examples include the radial forearm flap, the scapular flap and the lateral arm flap (Fig. 13.6a—c). Almost any perforating blood vessel can be used as the vascular basis for a flap if carefully identified and dissected out. These so-called perforator flaps are the latest extension of flap design.

Muscle and musculocutaneous flaps

Muscles have predictable patterns of vascular anatomy that permit the elevation of a muscle on one or more of its vascular pedicles for use as a muscle flap, either locally or as a free tissue transfer. Many muscles also have perforating vessels passing from their substance into the overlying skin enabling musculocutaneous flaps to be designed. Musculocutaneous flaps based on the latissimus dorsi and rectus abdominis muscles are particularly useful in breast reconstruction (Fig. 13.7a and b). These same muscles are widely used as free muscle flaps to repair defects in the lower limb associated with open tibial fractures (Fig. 13.8a—c). 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. Such techniques are applied to the rehabilitation of brachial plexus injury, anal incontinence and facial palsy.