Introduction
Loss of skin and subcutaneous fat over the elbow, forearm, and hand are common occurrences after trauma and oncologic excision. Sometimes, it is accompanied by loss of tendon, muscle, bone, and peripheral nerve with varying degrees of complexity. The coverage strategy depends on several criteria. The topography of the defect, associated injuries, postoperative rehabilitation needs, functional demand, work activity, and patient age all influence the decision. As always, the surgeon’s experience and technical skills must be considered.
General principles of method selections
Choice of different methods
The hand surgeon should be familiar with available techniques from skin grafting, local transpositions, and advancement flaps to local or remote pedicled flaps and microsurgical free flaps. A general principle is to use the reconstructive ladder to guide the choice of the methods ( Fig. 23.1 ), although in some institutes vascularized free tissue transfers are used to bypass the ladder. The use of local flaps requires complete knowledge of the regional vascularity of the arm and specialized dissection techniques. Local flaps should be considered first. , In experienced hands, however, reconstruction with a free flap can be the first choice, because a composite free flap allows for the reconstruction of several tissues at the same time. Also, the aim should be not to add damage to a damaged area, but unfortunately that cannot be a rule. Each patient and each tissue deficit are unique, and surgeons have their individual levels of expertise and preferences.
In all cases, the ideal reconstruction will respect the respective mechanical characteristics of the skin of the hand, wrist, forearm, and elbow regions both volarly and dorsally. When considering function, the coverage must take into account adjacent joints and the specifics for each anatomical region. The region of the elbow crease is characterized by thin and mobile adipose and skin that must not have any adhesions, which is why thin flaps that allow complete movement are preferred. ,
The use of perforator-based flaps will also be described, which is an evolution in the treatment of skin loss and can be either with an adipofascial pedicle or one mobilized on a perforator vessel (advancement, rotation, propeller). These skin-adipose flaps meet all the criteria required for upper limb coverage. They combine thinness and low donor-site morbidity and preserve the main arteries and muscles. ,
Single or staged reconstruction for complex multiple structural defects
If there are complex losses of skin along with tendons, bone, nerves, vessels, or joints, the goal often is to reconstruct everything in one operation and then begin early motion to avoid joint stiffness. If it is not possible to reconstruct everything at once due to severe contamination, extensive tissue loss and poor body conditions, etc, delayed treatment or staged treatment should be planned, using temporary spacers (silicone rods for tendons, antibiotic cement for the bone) when there is a need, which allow easier and more effective subsequent surgery. Patients with severe contamination in the trauma sites present a contraindication for complicated surgery such as tendon grafting or bony reconstruction. Reconstruction of tendon or bones in these patients should be planned after contamination or infection is under control. Flap coverage to restore skin coverage can be considered ahead of tendon and bone reconstruction. The treatment of bone, tendon, and neurovascular injuries is only feasible if the skin can be perfectly restored to protect the deeper repairs and reconstructions.
Skin coverage can be considered only after complete debridement of all contaminated, necrotic, and potentially necrotic tissue. The options for skin coverage, particularly the use of flaps, are diverse. , , , , , Below, we introduce the various reconstructive possibilities and indicate those preferred in different authors’ practices.
Treatment methods
Healing by self-regeneration
Healing by self-regeneration is commonly called healing by second intension, which is a confusing term. We prefer the term self-regeneration, which is the simplest and most common method of coverage and is preferred in superficial injuries without exposure of the deeper, critical tissues.
Self-regeneration of skin is the usual method chosen for treatment of small wounds. Proliferation from the edges of the lesion is progressive, and excellent results can be anticipated. A small skin defect in the palm can heal very well. Early motion is allowed, and there is no delay in starting hand therapy. Local debridement, cleansing, and freshening the skin edges, when necessary, allow for prompt epithelization to occur under nonadherent dressings change every 1 to 4 days.
The healing time varies between 2 and 5 weeks according to whether the skin defect is small or intermediate. This can result in a perfect aesthetic and functional result, better than a local or free flap. Granulation and epithelialization, however, take more time than a flap transfer and may require several clinical check-ups. ,
Even for superficial wounds up to 6 centimeters by 6 centimeters, such as loss of skin on the dorsal hand or forearm, self-regeneration can be complete in 1 to 2 months provided that the patient does dressing changes to keep the site clean. This works for patients with failed skin grafts and for those who chose not to have a skin graft. The regeneration takes longer for larger wounds but avoids the use of donor skin. Skin substitutes can be considered to cover the wound, keep it moist, and reduce the risk of infection.
Skin grafts
Skin grafts vary in thickness: thin split-thickness, thick split-thickness, and full thickness. Grafts can only be used if there is a well-vascularized recipient bed, perhaps prepared beforehand with subatmospheric pressure therapy (vacuum-assisted closure, or VAC). The thinner the graft, the easier it is to take root and revascularize, but it has the disadvantages of adherence to deeper tissues and the lack of sensitivity.
Full-thickness grafts provide stable good quality coverage with better sensitivity than thin grafts, but they do not shrink, which may or may not be an advantage. The graft must be secured on the recipient bed with a compressive dressing. For the hand or forearm, this could be a circumferential bandage, but a tie-over dressing is an alternative. Here, the graft is held in place with braided sutures tied over a compressive material, such as gauze, cotton, or foam. The tie-over dressing is removed after 2 to 3 weeks depending on the size of the graft. Smaller grafts may be uncovered after 2 weeks, but a large graft should be secured for 3 weeks.
Dermal substitutes
Dermal substitutes can be used for traumatic skin defect or donor site coverage after flap harvest instead of a skin graft and also for a wound after a burn. Coverage of such wounds with dermal substitutes creates a neoderm under these substitutes. The substitutes usually dissolve or fall off 2 or 3 weeks after being sutured to the skin edge. The skin-regeneration process under the skin substitutes is protected, and the quality of skin regeneration may be better.
The indications for their uses vary depending on the surgical team, but they have been used to successfully repair small or midsized superficial skin and subcutaneous defects and for defects left from harvesting a free or local flap to improve the aesthetics and function of the donor site. This measure improves the outcomes of the donor area for radial forearm and dorsalis pedis flaps. Dermal substitutes can certainly be used for treatment of wounds after burns; the resulting skin is flexible, scarless, and tough. The appearance is better than that of a mesh graft, and there is a low incidence of scar contraction.
For traumatic defects or after oncologic excisions, the skin substitutes may cover the defects in fingers with exposed tendons and/or bones and joints, creating a tendon gliding plane and/or a capsular formation that allows digital motion. Granulation tissue first forms over the tendons or bone, and then skin regenerates between the granulation tissues and skin substitute. The use of skin substitutes greatly reduces the need for a local flap transfer on small wounds.
For a larger wound in the hand or forearm, skin grafting can be performed if the skin substitute fails to completely regenerate the defect after 3 or 4 weeks, when the skin substitutes fall off.
Timing of tissue transfers
In the emergency room or in an emergency operating room, the wound should be debrided and washed thoroughly, and antibiotics are given to prevent infection. Local flap transfers can be performed in emergency settings, or a few days later, with the wound packed with gauze to allow for better surgical planning or if a hand surgeon is not available in the emergency sitting ( Box 23.1 ). The decision for emergency or delayed tissue transfer varies in different institutes.
Timming of Flap Transfers
Primary: Carried out when experienced surgeons are available and wounds are clean, or when there is a need of vascular reconstruction with a defect repair.
Delayed: If the surgeons are not available, or wounds are infected or severely contaminated. Vacuum-assisted closure (VAC) and skin substitutes can be used for primary coverage.
Late: If the tendon grafting is necessary and that is not done in primary or delayed stages.
The Use of Skin Substitutes and VAC
Skin substitutes: Used for a superficial wound that has skin loss with or without subcutaneous loss. For a small-sized wound, skin graft may not be necessary after its use. For a larger wound, skin graft is often still necessary, although the graft is smaller than when a skin substitute is not used.
VAC: Used for a deep wound. Can be used for an infected wound, helping control infection and making the wounds better prepared for tissue transfers. The use of VAC often narrows the defect size. The VAC can be used for a few weeks before delayed surgical repair.
Emergency flap transfer must be performed when the distal portion of the limb requires revascularization, in which circumstance, either a flow-through flap or a venous graft combined with a free flap can be used ( Box 23.1 ). If there is extensive tendon, nerve, or bone exposure, emergency reconstruction of these structures should also be considered but can be delayed in most cases.
An alternative approach is a delayed primary reconstruction, with the wound site covered with gauzes or, more often now, with VAC. Reconstruction is planned days later if gauzes are used to cover and there is no severe infection. VAC can be used for an infected wound or if the surgeons wish to narrow down the wound size. The delayed reconstruction can be carried out after weeks of use of VAC.
The use of VAC
For a large wound, VAC can be used to cover the wound after debridement. VAC serves to cover the wound and promotes tissue regeneration, possibly narrowing the wound ( Fig. 23.2 ) ( Box 23.1 ). With VAC coverage, the patient can be operated 1 to 4 weeks later with no increase in the risk of infection and with a smaller wound and the possibility of coverage with only skin graft in a wound that would have initially required flap coverage. VAC can be used for a clean wound or an infected wound. VAC is considered a good option for covering an infected wound and controlling infection before tissue transfers ( Box 23.1 ). VAC therapy often narrows the wound sizes, so simpler tissue transfers may be used. For example, skin graft may be used after VAC use in a wound where a flap transfer is initially needed. The drawback of VAC coverage for tissue regeneration is the longer treatment time and still the need for a flap transfer even after VAC application for weeks for a large wound.
For a superficial wound with loss of only the skin and subcutaneous, in the absence of infection or contamination, a skin substitute is used to stimulate wound healing ( Box 23.1 ), for which VAC is not necessary.
Flaps
Flaps are the most complete and effective solution for covering a middle to large size tissue defect. Their vascular autonomy allows them to survive. They allow for faster recovery and early timing for any needed secondary surgeries. A drawback of flaps is the donor site morbidity. Therefore, all options are to be considered before flap transfers ( Box 23.2 ).
- 1.
Local flaps are considered first, with rotational or advancement flaps considered as a primary option for a simple or small defect.
- 2.
Self-regeneration is possible for smaller defects, which is a valid option. Skin substitutes can be used to cover the defect for better self-regeneration. This option can be used together with local flaps. Vacuum-assisted closure is used to make the wound cleaner and stimulate tissue regeneration for wound closure or before flap transfers.
- 3.
For a large defect, a pedicled flap transfer or a free flap transfer is used. The surgeons decide which is to be used according to experience and preference.
- 4.
A variety of flaps are available. The anterolateral thigh flap and superficial circumflex iliac artery perforator/groin flap are among the most commonly used free flap transfer to the hand and upper extremity.
- 5.
A number of perforator flaps in the upper extremity are available for a pedicled transfer or free tissue transfer to the hand.
- 6.
Venous flaps can be used for dorsal hand and proximal finger defect coverage.
- 7.
A flow-through flap can be used for the defect with a lengthy arterial defect.
It is necessary to distinguish and classify skin flaps according to their vascular supply . Random flaps have no named vascular structures supplying them. Axial flaps follow the course and territory of a well-defined arteriovenous pedicle . Septal flaps have a vascular pedicle lying in an intermuscular septum (e.g., radial, posterior interosseous) . Perforator flaps depend on a perforator vessel coming from a main arterial axis and destined for the skin ( Fig. 23.3 ).
Conjoined flaps, that is, the combination of two perforator flaps based on a larger mother vessel, can be used. Furthermore, chimeric flaps , that is, compound flaps of multiple flap territories, each with an independent vascular supply without interconnection except being linked by a common source or “mother” vessel, can be harvested to allow versatile design and application of the perforator flaps ( Fig. 23.4 ).
Flaps can also be differentiated by the proximity of the donor region. Local flaps come from the same area as the loss of substance, whereas microsurgical free flaps bring varying tissues to the defect. Combinations include skin and subcutaneous fat; fascia; fat and fascia; fat, fascia, and skin; muscle; and bone and skin. For coverage, skin flaps or fascia or muscle flaps grafted with skin are usually used ( Box 23.2 ). We will describe briefly local and free flaps that are used for the coverage of the elbow, forearm, and hand to give some practical examples.
Flap from the thorax
Latissimus dorsi flap.
The latissimus dorsi myocutaneous flap is highly useful for the reconstructive surgeon. The flap, supplied by the thoracodorsal vessels, provides broad soft-tissue coverage with minimal donor site morbidity. The flap can be used as a pedicled flap for arm and elbow coverage or as functional muscle transfer (for elbow flexion) or as a free flap (rarely needed in the reconstruction of hand and forearm, but it is available for large tissue losses).
The thoracodorsal artery most commonly branches from the subscapular artery, or it may branch from the axillary artery. It averages 8 cm in length. The entire muscle or the anterior portion of it, including a skin paddle, may be harvested up to the size of 12 to 35 cm and can be tunneled into the arm from the axilla. Because this flap must be rotated on its pedicle and passed subcutaneously to reach the elbow, vascular compromise can result if the pedicle is twisted, stretched, or compressed.
This flap can be harvested as a thoracodorsal artery perforator flap and transferred as a free flap to many parts the body or can be used locally in the shoulder/axilla and arm region.
Local flaps from the forearm
Radial forearm flap or “chinese” flap.
It is a fasciocutaneous and septocutaneous flap located in the anterior aspect of the forearm. The advantages of using it are its reliability due to the constant anatomy of its pedicle, its size, which can correspond to almost the entire anterior aspect of the forearm, its thinness, its wide arc of rotation, its acceptable aesthetic sequelae, and the possibility of making it a composite flap (bone, tendon). Its main drawback is the sacrifice of a major arterial axis. The flap can be raised with direct flow to cover elbow substance loss or as a free flap or with retrograde flow (using the palmar arch connection with the ulnar artery) ( Fig. 23.5 ).
The Allen test evaluating the patency of the anastomosis between the two forearm arteries in the palm should always be performed before surgery to confirm that circulation to the hand will be maintained without the radial artery.
Ulnar forearm flap.
The same principle of harvesting the radial forearm flap can be used for the ulnar forearm flap. In some cases, it is important to switch to the ulnar forearm flap when that artery is smaller than the radial artery or when there are no anastomoses from the two main arteries in the palm. It can also cover the elbow as a direct flow flap, particularly if the ulnar artery is already not working at the wrist level ( Fig. 23.6 ). Also, it can be used as a free flap.
Becker dorsoulnar flap.
Proposed by Becker, , the vascularization of this flap depends on the distal branches of the ulnar artery and, more specifically, the dorsoulnar artery ( Fig. 23.7 ). It is a cutaneous or adipofascial flap located on the medial and distal forearm ( Fig. 23.8 ). It has the advantage of not sacrificing a major artery. However, its pedicle is relatively short but can be lengthened by passing the flap deep to the flexor carpi ulnaris (FCU) ( Fig. 23.9 ).
The ulnar artery perforator flap is most commonly used as a pedicled flap for coverage of defects of the ulnar hand and wrist, both dorsal and volar, typically up to 10 × 5 cm in size. Alternatively, it can be harvested as a free flap.
The dorsal branch of the ulnar artery arises from the ulnar artery 2 to 5 cm proximal to the pisiform ( Fig. 23.7 ). The dorsal branch of the ulnar artery has a diameter of 1.0 to 1.3 mm. It travels from the volar distal forearm from radial to ulnar, under the FCU and gives off three branches. The distal branch, the pisiform artery, supplies the pisiform. The middle branch divides into ascending and descending branches over the dorsoulnar forearm to supply the forearm and hand, respectively. The ascending branch travels proximally to the medial epicondyle. The descending branch joins the dorsal carpal arch over the dorsal hand. An ulnar artery perforator flap is based on the ascending branch of the dorsal branch of the ulnar artery and its two vena comitantes.
The proximal branch enters the FCU 4 to 6 cm proximal to the pisiform. Flaps with widths up to 6 cm can be closed primarily over the ulnar forearm. Wider flaps require coverage with a split-thickness skin graft. The flap is indicated for volar defects in the hand where the posterior interosseous artery flap cannot reach to cover ulnar side of the hand or wrist.
Posterior interosseous flap.
This flap is vascularized by retrograde flow from the anterior interosseous artery through an anastomosis with the posterior interosseous artery. The posterior interosseous artery runs in the septum between the fifth and sixth extensor compartments ( Fig. 23.10 ). This flap is a fasciocutaneous and septocutaneous flap located in the dorsal forearm. Its arc of rotation is wide and can reach the dorsum of the hand ( Fig. 23.11 ). The skin paddle may be wide if the harvest site is not closed primarily. Venous drainage is counter-current, and this often causes congestion. A disadvantage of this flap is that the donor area is on the more visible side of the forearm. The donor site should be preferentially closed primarily if possible. To avoid problems of venous congestion, ample adipofascial tissue should be harvested within the pedicle. Also, the posterior interosseous artery flap can be used as a direct flow flap for coverage in the elbow region.
Lateral arm flap.
This flap is vascularized by the posterior terminal branch (posterior radial collateral artery) of the deep humeral artery (profunda brachii). The anterior branch accompanies the radial nerve to anastomosis distally with the anterior radial recurrent artery. Mobilized from the lateral side of the arm, it can be a fasciocutaneous or a septocutaneous flap. This flap does not sacrifice a major arterial axis and can be harvested with a piece of bone. This can be used locally, as a distally based flap for the elbow region, or as a free flap for the thumb or the hand ( Fig. 23.12 ). As a free flap, it has the advantage of being on the same limb as the recipient site. Sometimes, the flap is very thick and not the best for hand reconstruction.
Brachioradialis muscle flap.
The muscle has an overall length of 30 to 35 cm, of which 20 to 22 cm is muscle and the remainder is tendon. The width of the muscle is 3.5 cm, and its thickness varies between 1 and 2.5 cm. The brachioradialis may provide up to 9 by 10 cm square coverage in the antecubital fossa, so it can easily cover forearm neurovascular structures and areas of soft-tissue loss. It is possible to spread the muscle and obtain an extra third of width. The major pedicle arises from either the radial (40%), radial recurrent (40%), or brachial artery (20%). The muscular branch of the radial recurrent artery is about 3 cm long with a diameter of 2 mm. It exits from the radial artery at the medial border of the muscle about 10 cm from its origin. In addition, the radial artery gives off a maximum of three minor muscle branches (length 1.5 cm, diameter 1 cm) at variable positions.
A pedicled brachioradialis muscle flap has been described as an option for the reconstruction of posterolateral elbow wounds. The brachioradialis lies within the radial and brachial angiosomes and receives its blood supply from the radial recurrent artery, the radial artery, and the brachial artery. The dominant artery supplying the brachioradialis muscle is variable. When using this muscle for posterior elbow coverage, both the radial recurrent artery and the radial arterial branches to the muscle need to be maintained to provide adequate perfusion to the flap.
Flexor carpi ulnaris muscle flap.
The muscle of the FCU has a consistent blood supply from the ulnar artery and posterior recurrent ulnar artery, which facilitates the use of this muscle flap for coverage of the olecranon. This turnover flap is based on the most proximal primary pedicle, which arises on average 6 cm from the tip of the olecranon.
Anconeus muscle flap.
A pedicled anconeus muscle flap is another source for coverage of periarticular elbow wounds, although the extent of coverage is limited by its pedicle length. It is useful for small defects over the olecranon or the radiocapitellar joint, and its harvest results in a minimal loss of function related to terminal extension and supination of the forearm. , The arterial supply to the anconeus includes the recurrent posterior interosseus artery, the medial collateral artery, and a posterior branch of the radial collateral artery. When harvested on the medial collateral artery, which lies along the deep surface of the anconeus and anastomoses with the recurrent posterior interosseus artery, the muscle flap can cover an area up to 7 by 7 centimeters over the posterior olecranon and the radiocapitellar joint. The recurrent posterior interosseus artery, which is the main arterial pedicle to the anconeus, is short and can limit mobilization of the flap to cover the posterior elbow.
Perforator flaps from upper extremity
Perforator flaps: Definition.
Perforator flaps are adipocutaneous or fascioadipocutaneous flaps whose vascularization depends on one or more cutaneous arteries called perforator arteries, which originate from deep vascular trunks (e.g., humeral, radial, ulnar artery) ( Fig. 23.3 ). These flaps are increasingly used in reparative surgery of the skin of the upper limb.
Approximately 45 upper limb perforator arteries are described, and these can be used to nourish flaps. The true perforator arteries are supposed to perforate a muscle and exit onto the skin. However, there is a tendency, especially in the upper limb, for any vessel that perforates the fascia and reaches the skin to be called a perforator, thereby expanding the concept.
The use of perforator flaps has allowed for preservation of muscle function in those areas where the artery perforates the muscle an intramuscular dissection. An example is anterolateral thigh (ALT) flap, which can be used either pedicled or free.
Pedicled perforator flaps from upper extremity.
In the upper limb, pedicled perforator flaps are very useful to cover loss of substance with small to moderate exposure of internal structures in any anatomical region. , The main advantage is low morbidity at the donor site without sacrificing a major vascular axis. Moreover, by using neighboring tissue, a like-for-like replacement is performed with great time savings. In many cases, the donor site can be closed primarily.
Normally, the perforator arteries have a known distribution, but in order to know exactly where they are and whether they are reliable, a Doppler or echo Doppler examination is performed preoperatively for proposed donor sites in the lower limb or trunk. This makes the surgery easier and faster. In the upper limb, this identification is difficult due to the shortness of the vessels, and we rely on anatomical studies that define the territories where direct cutaneous arteries are most frequently found.
Boucher has described all these areas into an excellent atlas, which is very useful for identifying perforator arteries of the upper limb. An exploratory incision is made along one edge of the flap design and the deep fascia is reached; the dissection follows a supra- or subfascial plane until the artery that reaches the skin is identified, at which point it is followed proximally to the major vessel, taking care not to damage the concomitant veins. The design is usually spiral-shaped or if it employs advancement rather than rotation, it may be triangular in shape.
Anatomy of perforator vessels for raising perforator flaps in the forearm.
The radial, ulnar, anterior interosseous artery, posterior interosseous arteries give perforator arteries which blood supply the skin. They are mainly direct or septocutaneous perforators, and just a few are musculocutaneous. The most important musculocutaneous perforator is the one emerging from the radial recurrent artery, which passes through the brachioradialis muscle. Of great importance is the fact that a network of linking vessels exists between perforators of all the main vessels. This network is found between the deep fascia and dermis, which means that the flaps can also be harvested suprafascially.
The radial artery gives a few larger musculocutaneous and septocutaneous perforators in the proximal two-thirds of the forearm and more numerous smaller septocutaneous perforators in the distal third, the most important of them emerging between 2 and 7 cm proximal to the radial styloid. These distal perforators have external diameters of 0.3 to 0.9 mm and emerge between the brachioradialis and FCU tendons. In the proximal two-thirds of the forearm, the perforators’ branches run and anastomose longitudinally, whereas in the distal third they run and anastomose transversally with perforators from the ulnar artery. The most important perforator is the inferior cubital artery, which emerges from the radial recurrent artery or from the radial artery and which vascularizes an area extending up to 10 cm distal from the apex of the antecubital fossa. The territory of the radial artery extends transversally between the projection of the palmaris longus and the lateral edge of extensor digitorum communis tendons and longitudinally up to 5 to 8 cm distal to the epicondylar line of the elbow. When the inferior cubital artery emerges from the radial artery, the territory of the radial artery can extend proximally.
The main perforators of the ulnar artery emerge in the distal two-thirds of the forearm. Most of them arise about 8 cm proximal to the pisiform through the FCU and flexor digitorum superficialis. The territory of the ulnar artery extends to the posterior border of the ulna. Like the radial artery, the perforators of the ulnar artery run and anastomose longitudinally in the proximal part and transversally, with perforators from the radial artery, in the distal part of the forearm.
The skin over the distal part of extensor pollicis brevis and abductor pollicis longus on the lateral border of the distal forearm is blood supplied by the anterior interosseous artery (AIOA). There are three main perforators, the most important emerging at the proximal border of the pronator quadratus and supplying the skin over the distal two-thirds of the dorsal aspect of the forearm.
The skin over the dorsal aspect of the proximal third of the forearm, between the FCU and extensor carpi ulnaris (ECU) muscles, is vascularized through perforators from the posterior interosseous artery (PIOA). The PIOA also vascularizes the skin of the distal two-thirds of the dorsal aspect of the forearm through perforators that reach the skin between the ECU and extensor digiti minimi proprius tendons. Over the wrist and immediately proximal, the PIOA perforators anastomose with AIOA, the distal carpal arch, and the ulnar artery.
The venous drainage of the forearm flaps is realized through the concomitant small veins that accompany the perforator arteries. There are 1 to 2 such veins for each perforator artery, and they form a very rich venous plexus draining into both the superficial and deep main veins.
According to the angiosome/perforasome principles, the perforators vascularize not only the skin, but also all the structures under the skin, which allows for the possibility of harvesting composite local perforator flaps.
Keystone flaps: A variant of perforator flaps.
Keystone flaps represent a variant of local perforator flap, which actually are multiperforator flaps ( Fig. 23.13 ). They have a curvilinear trapezoidal form and are harvested from the area immediately adjacent to the defect and maintain an orientation in the axis of the dermatome. Their main advantage is that they do not require visualization and dissection of perforators. The flap should be designed long enough to get bilateral V-Y closure of the donor site. Generally, the ratio between the width of the defect and of the flap is 1:1, but it is better if the width of the flap is a little larger. First, two lines are drawn at 90 degrees from either end of the defect, which will meet the curvilinear line of the future flap.
Flaps from other parts of the body
McGregor inguinal flap – superficial circumflex iliac artery perforator (SCIP) flap.
This flap is based on the superficial circumflex iliac artery. The donor area is the inguinal region and flank. The advantages of this flap are its large area (10 cm × 25 cm), its reliability, and possible direct closure of the donor area. Its disadvantages are its sometimes considerable thickness, its nonsensitive nature, and its short vascular pedicle. If harvested above the superficial fascia in the superficial circumflex iliac artery perforator flap fashion, the thickness can be reduced a lot and become a very thin SCIP flap.
This flap is commonly used as a free flap, called a free inguinal flap, which can be based on the superficial circumflex iliac artery (SCIA) described initially by McGregor and Morgan , ( Fig. 23.14 ). It has a short pedicle and small-caliber vessels. Its thickness usually requires several secondary removals of adipose tissue. However, its aesthetic sequelae are minor in the case of an easily concealed recipient area. With the advent of perforator flaps, the perforator-based SCIA flap (SCIP flap) was described by Koshima et al for covering local or distant tissue loss ( Fig. 23.15 ). The results of these clinical investigations suggest that a single SCIA perforator is sufficient to vascularize a large portion of very thin tissue, surpassing the advantages of the McGregor flap.
