Classification of Free Flaps

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The following types of free flaps have been described: The fascial or fasciocutaneous, the muscle or musculocutaneous and recently the perforator flaps and the special tissues, such as vascularized bone, nerve, tendon, intestine, omentum, etc.

Fascial flaps consist of a circumscribed area of fascia. If the overlying skin and subcutaneous tissue is included, the flap is called fasciocutaneous. The vascular supply, usually a named artery, flows directly to these flaps and does not perforate muscle. Fasciocutaneous flaps have the following advantages:

Underlying vascularized bone such as segments of metatarsal, radius, scapula, or calvarium may be transferred with dorsalis pedis, radial forearm, scapular and temporal flaps respectively.

Fasciocutaneous flaps tend to be less bulky than musculocutaneous flaps, a desirable characteristic for certain areas, as on the face, neck, hand and wrist, foot, etc.

Several fasciocutaneous flaps may include a sensory nerve supply, important for hand and weight bearing areas of the foot reconstruction. Fasciocutaneous flaps have the following disadvantages:

Donor sites may be visible and objectionable, particularly if a skin graft is required for their closure.

The vessel to the flap may be a large one (the radial artery for the radial forearm flap, for example) and its interruption may cause ischemic symptoms, or in the contrary it may be a small one, difficult to work with (deltoid flap). Fasciocutaneous flaps, unlike muscle flaps with skin grafted surfaces, change configuration with weight change.

Fasciocutaneous flaps usually do not provide the bulk that muscle flaps do, and so may not be suitable for filling sizeable defects. The most commonly used fasciocutaneous flaps are mentioned below:

The superficial temporal fascial flaps supplied by the temporal artery is useful for reconstruction of small defects on the face, for resurfacing the dorsum of the hand and occasionally for reconstruction about the foot and heel where bulk is unnecessary. It is usually taken without the overlying scalp which is then closed over the donor site. The underlying outer table of the calvarium may be taken with the fascia as a vascularized bone graft. The donor site is acceptable.

The scapular flap,6,71 based on the circumscapular branch of the subscapular artery provides a very large segment of skin and soft tissues. The donor site is most commonly closed directly. Vascularized bone, the lateral edge of the scapula, may be elevated with this flap.

The deltoid flap18 vascularized through the posterior humeral circumflex vessels, includes the sensory branch of the axillary nerve and it can be used to restore protective sensation at the recipient site. The donor site may be objectionable, particularly if it cannot be closed without skin grafting.

The lateral arm flap44 supplied by the terminal branch of the profunda branchii artery is popular for coverage of hand defects. It is also a sensory flap if the lower lateral cutaneous nerve of the arm, branch of the radial nerve, is sutured to a sensory recipient nerve. The donor site is as acceptable as any in the upper extremity.

The radial forearm flap ("Chinese flap")72 is based on the radial artery and the cephalic vein. A strut of the underlying radius may be taken with the flap. The ease of use, because of its large vessels, the relative thinness of the soft tissues and the possibility to restore sensation are its chief advantages. These advantages are offset by a very objectionable donor site unless direct closure is possible (skin expansion is occasionally indicated). The hairy skin in males is often undesirable and some circulatory impairment of the hand that necessarily results from the use of the radial artery. This may be severe or dangerous in the 20% of individuals in whom the superficial palmar arch is incomplete. A vein graft is required if the hand shows signs of vascular insufficiency. This flap is often used in head and neck, upper extremity and foot and ankle reconstruction.

The groin flap60 based on the superficial circumflex iliac vessels was the first flap used for free tissue transfer in the lower extremity. It has small vessels that show considerable variation and make this transfer unreliable. The donor site is acceptable, The groin flap is still used occasionally and may be useful in skilled microsurgical hands, but there are better choices available today. The dorsalis pedis flap54,59 based on the dorsalis pedis artery is useful for defects where a thin sensory flap is needed. In addition it can be used without dividing the pedicle to cover the malleoli or, by releasing the extensor reti-naculum, the anterior ankle and lower leg. The donor site tends to be troublesome (poor healing, poor take of skin grafts, inadequate protection of underlying structures). This flap should be used only under special circumstances. The first web space of the foot,55 based on the dorsalis pedis and the first dorsal metatarsal vessels, is excellent for sensate reconstruction of the hand and digits because of the similarity of the tissues. It is occasionally used for small defects about the foot.25

Muscle Flaps

Nearly any muscle will serve as a free flap if its vessel is large enough to permit microsurgical transfer. A type I vascular pattern (a single, large dominant vessel) is preferred. The transferred muscle should be easily spared and its use should result in only minimal functional impairment.

Muscle flaps used for free tissue transfer have the following advantages:

The donor site is usually both cosmetically and functionally acceptable. Endo-scopic dissection of the muscle may minimize even further the donor site scar. Skin grafted muscle flaps tend to be "self-contouring", that is, the denervated muscle loses its initial bulk and often takes the contour of the area where it is transferred. Cosmetic results tend to be good. Skin grafted muscle does not change in size as the patient gains or loses weight, as occurs with

fasciocutaneous, musculocutaneous and perforator flaps.

The rich circulation in muscle flaps permits their use in less than optimal recipient sites, (osteomyelitic defects, irradiated areas etc.).

Innervated transferred muscle can restore motor function (most applicable in the arm and in the face).53

It is possible to obtain long pedicles, particularly with the rectus abdominis and the latissimus dorsi muscles.

Muscle flaps may have the following disadvantages:

There is inevitable diminution of motor power of the functions served by the muscle. Practically this seems not to be of great importance. There is inevitably some loss of normal contour and support at the donor site. Again, clinically this is usually not particularly troublesome. In an attempt to completely eliminate these disadvantages the perforator flaps have been described. The perforating branches of the vascular pedicle are dissected through the muscle which is then left in place while the overlying skin and subcutaneous tissue are elevated along with the vascular pedicle and used as free tissue transfer.2,17,42,43,78

The following muscles are most commonly used for free flap transfer:

The latissimus dorsi muscle"5,1"1 is the single most useful muscle. Its large size allows coverage of almost any type of defect. Alternatively, the muscle can be split, the lateral portion of it can be transferred to cover small defects, leaving the medial portion and its innervation intact.21 The thoracodorsal branch of the subscapular vessel—the largest branch of the axillary artery—supplies the latissimus. The pedicle may be very long if the dissection includes the main subscapular vessels as far as the axillary artery. The donor site and its scar are acceptable. A drawback of the latissimus flap is that the patient sometimes must be turned on the operating table.

The rectus abdominis9,10 supplied by the large deep inferior epigastric vessels is a long muscle, if taken from its origin on the chest wall to its insertion on the symphysis pubis and it is most easily obtained in the supine position, while the preparation of the recipient site is carried out simultaneously. The donor site scar is that of any vertical abdominal incision and as such is acceptable. The single greatest drawback to its use is the occasional complication of abdominal wall weakness or herniation that can be avoided with careful wound closure.32 Reinforcement of the rectus fascia with synthetic mesh is sometimes indicated. Alternatively perforator flaps based on the deep inferior epigastric vessels can be dissected, sparing the rectus muscle completely and utilizing the skin and subcutaneous tissue of the lower abdomen (Fig. 7.3). The visible tendinous inscriptions are a minor disadvantage when the rectus muscle is used. These tend to fade as the muscle atrophies, but usually do persist to some extent.

The gracilis muscle28 is commonly used for covering small defects and for functional reconstruction of the face or the upper extremity. Although this muscle has a segmental blood supply there is one constant dominant branch

Fig. 7.3. A) Postmastectomy.

of the profundus femoris that arises 8-10 cm below its origin on the inferior pubic ramus. The pedicle, if followed back to the profundus femoris vessels, is about 6 cm long, but its vessels tend to be small. Because of its easy access and the inconspicuous donor site the use of this muscle is recommended. Other muscle or musculocutaneous flaps, the serratus anterior, the gluteus maximus, the tensor fascia lata, the pectoralis minor or the extensor digitorum brevis from the foot, have all been used successfully in special circumstances.

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