The selection of a free flap is dependent on the following assessment of the recipient site: size and depth; mechanism of injury; exposed structures; structures needing reconstruction; contamination; the color and texture of the tissues surrounding the defect; and the need to restore sensation [8,17]. It is important to realize that following radical de-bridement the wound is often much larger and deeper than anticipated, and the microvascular anastomoses must be placed well out of the zone of injury. It is therefore desirable to choose a flap with a large and reliable cutaneous territory and a long vascular pedicle of large caliber, with the liberal use of vein grafts where required.
It is important to minimize morbidity at the donor site. The vast array of free flaps available in the armamentarium of the reconstructive surgeon allows the donor site to be chosen based on the skin color, texture, and the components missing from the recipient site. Composite flaps can be harvested with different tissue components raised on different perforators of the same source artery. For example, the anterolateral thigh flap enables multiple components to be raised on different perforators from the lateral femoral circumflex artery, including skin, deep fascia, the vastus lateralis, rectus femoris and tensor fascia lata muscles, and iliac crest, enabling the accurate reconstruction of complex three-dimensional mul-ticomponent defects . Ultimately the choice of flap is determined on both an individual patient basis and according to surgeon preference.
Fasciocutaneous flaps are indicated for the coverage of shallow wounds and can restore contour and provide an excellent gliding surface for tendons and joints. The ability to easily and quickly reelevate fasciocutaneous flaps is a definite advantage when staged reconstruction of bone, nerve, or tendon is anticipated later.
The lateral arm flap is based on the posterior radial collateral artery and its venae commitantes (see Fig. 3). Its potential flap territory includes the distal half of the lateral arm and the proximal third of the dorsolateral forearm, and it is an extremely versatile flap for medium-sized defects. It can be harvested as a composite flap, incorporating a segment of up to 10 cm in length of the humerus or a segment of vascularized triceps tendon for tendon reconstruction (Fig. 4) . It can also be harvested as a pure fascial flap for dorsal hand coverage when ultra-thin flap coverage is required. Sensate reconstruction can be performed using the posterior cutaneous nerve. Donor sites of up to 8 cm in width can be closed primarily. (Figs. 5 and 6).
These flaps incorporate a large and reliable cutaneous vascular territory with a long pedicle. The scapular flap is based on the transverse cutaneous scapular branch, and the parascapular flap on the vertical parascapular branch of the circumflex scapular artery after it traverses the triangular space. The circumflex scapular artery is a branch of the subscapular artery, which originates from the axillary artery. Both flaps can be harvested with a vascularized segment of bone from the lateral border of the scapula. The flaps result in a relatively inconspicuous donor site that can always be closed primarily. When large wounds require extensive coverage such as a complete forearm avulsion injury, the scapular/para-scapular flap can be combined with a latissimus dorsi flap and serratus flap based on the common subscapular vascular system (Fig. 7).
The radial forearm is a workhorse flap in microsurgical reconstruction. Its advantages are a long pedicle of large caliber, a thin flap that can resurface shallow defects, and the ability to harvest it as a composite flap with vascularized palmaris tendon, a segment of radius, antebra-chial cutaneous nerve, or brachioradialis muscle . The major disadvantage of this flap is the aesthetic and functional donor site morbidity. This, however, can be reduced by a number of strategies, including suprafascial flap harvest and full thickness skin grafting of the donor site . Vascularity of a suprafascially harvested radial forearm flap compared with a subfascially harvested radial forearm flap has been found to be almost identical in our 20 forearm anatomical cadaver dissections so far (Fig. 8).
Anterolateral thigh flap
The anterolateral thigh flap is based on the descending branch of the lateral femoral circumflex artery, with a perforator almost always found at the midpoint of a line between the anterior superior iliac spine and the superolateral aspect of the patella. The pedicle can be up to 15 cm in length, enabling anastomosis well out of the zone of injury (Figs. 9-11). Primary closure can be achieved if the flap width does not exceed 8 cm;
we have safely harvested flaps in excess of 30 cm in length safely on only one perforator (Fig. 12). A sensate flap can be achieved using the lateral femoral cutaneous nerve. There is also potential for thinning the flap in the primary or secondary setting to improve flap contour (Fig. 13). Advantages of the anterolateral thigh flap, including a large and reliable adipocutaneous territory, minimal donor site morbidity, long vascular pedicle, and the potential to be harvested as a thin and
sensate flap, are reasons why we currently favor this flap as our first choice for resurfacing shallow defects of the upper extremity.
This flap is based on a perforator from the descending branch of the thoracodorsal artery. The cutaneous vascular territory is very large and reliable, with minimal donor site morbidity without seroma formation. In thin patients the flap can be used for resurfacing of shallow defects without the need for thinning, otherwise the flap can be reliably thinned between the deep and superficial adipose layers at the level of the superficial fascia. If the perforator is very small, a cuff of latissimus dorsi muscle can be included to avoid traumatizing the perforator during the intramuscular dissection. The flap can be combined with part of the latissimus dorsi or serratus muscles, the serratus fascia, or a segment of scapula for composite reconstruction [28,29].
When a soft tissue defect is combined with a bony defect, the free fibular flap can be harvested as an osteocutaneous flap based on cutaneous perforators from the peroneal artery (Fig. 14). The flap is vascularized by the peroneal artery and venae commitantes, and can also be harvested with a cuff of soleus muscle for dead space filling. Skin, fibula bone, and soleus muscle can all be harvested separately based on independent perforators from the peroneal artery to facilitate freedom of reconstruction. (peroneal artery perforator flap).
Other fasciocutaneous flaps include a hemi-pulp flap from the great toe when critical sensory restoration of the thumb is required (Fig. 15). Ar-terialized venous flaps harvested from the forearm or dorsal foot can also be very useful for both resurfacing and revascularizing the digits (Fig. 16). The free groin flap is vascularized by the superficial circumflex iliac artery and offers an expendable and hidden donor site. This flap can be very useful when the donor site scar is of particular concern (Fig. 17).
Fascial flaps can provide extremely thin coverage for resurfacing dorsal hand or digital defects. Their disadvantage is that skin grafting is required and therefore graft contracture occurs, which can be particularly problematic over joints.
The temporoparietal fascia flap (TPF) is flap is formed from the superior extension of the superficial musculo-aponeurotic system, and is based on the superficial temporal artery and vein. The donor site is well hidden in the hairline. This flap is useful for resurfacing of shallow defects of the dorsum of the hand and forearm as well as providing a gliding surface for tendons. The size of a TPF flap is smaller than the serratus fascia flap, and injury to the auriculotemporal nerve must be avoided.
Serratus fascia flap
This flap is based on the serratus branch from the thoracodorsal artery and vein. It is thin and pliable, and a large flap can potentially be harvested for extensive surface resurfacing.
Muscle flaps combined with a split thickness skin graft are especially indicated for the reconstruction of complex three-dimensional defects where the filling of dead space is required. They are also indicated for heavily contaminated wounds and chronically infected wounds.
The latissimus dorsi flap has long been a workhorse flap in upper extremity reconstruction and is based on the thoracodorsal vessels, providing a reliable flap with a long pedicle. It may be harvested as a muscle-only flap or as a musculocutaneous
predictable branching pattern of the thoracodorsal artery into a descending and transverse branch allow splitting of the latissimus dorsi muscle for reconstruction of smaller defects, while reducing donor site morbidity by preserving the thoraco-dorsal nerve . The flap is useful for filling dead space in complex three-dimensional defects. The disadvantage is that sensory reinnervation is not possible.
The rectus abdominis flap is also useful for reconstruction of complex defects (Fig. 19). It is based on the deep inferior epigastric artery and vein, and may be harvested as a muscle flap or as a musculocutaneous flap. The orientation of the skin paddle may be transverse, vertical, or oblique, and the pedicle length can be increased by intramuscular dissection. A sensate flap can be created by neurorraphy of a segmental intercostal nerve. Donor site morbidity can be reduced by using a muscle-sparing technique, or by raising the flap based on a deep inferior epigastric artery perforator or the superficial inferior epigastric artery.
flap. The flap may be combined with the serratus muscle or the scapular or parascapular flap to increase the size of the flap (Fig. 18), or harvested with a portion of vascularized rib. The
Serratus muscle flap
The serratus muscle flap is based on the serratus branch of the thoracodorsal artery. The inferior three slips of the serratus muscle can be
harvested to provide a thin flap that is suitable for resurfacing small and shallow defects. Skin grafting of the flap is required.
The gracilis flap is based on the medial circumflex artery and vein, and can be harvested as a muscle-only or musculocutaneous flap for coverage of small to medium-sized defects. The pedicle length is typically 6 to 8 cm, and the flap can also be used for functional reconstruction of the forearm to restore finger flexion or extension.
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