The Forearm Flap – Indications, Appropriate Selection, Complications and Functional Outcome

A correct indication and specific knowledege in planning and harvesting free transplants are needed to minimize morbidity and maximize quality of life (QOL). Since the introduction of microvascular surgery in the 1970s, continuous surgical efforts and research were made to optimize the techniques. Consequently, there exist distinct technical modifications and alternatives that give the surgeon the possibility of adequate technique and flap-design selection dependent on the patient and situation. In the 1990s, the free forearm flap became the most utilised technique for free tissue transfer in the head and neck, with success rates of over 90% (Soutar & McGreagor, 1986, Swanson et al., 1990). The forearm flap was described by Yang and colleagues in 1981 for the first time and has become one of the most used transplants for reconstruction in the head and neck and a widely used transplant for other indications as well. Various complications and functional impairments at the donor site have been reported so far which are presented together with techniques to minimize them, and together with the characteristics, indications and design options of this flap.


Introduction
A correct indication and specific knowledege in planning and harvesting free transplants are needed to minimize morbidity and maximize quality of life (QOL). Since the introduction of microvascular surgery in the 1970s, continuous surgical efforts and research were made to optimize the techniques. Consequently, there exist distinct technical modifications and alternatives that give the surgeon the possibility of adequate technique and flap-design selection dependent on the patient and situation. In the 1990s, the free forearm flap became the most utilised technique for free tissue transfer in the head and neck, with success rates of over 90% (Soutar & McGreagor, 1986. The forearm flap was described by Yang and colleagues in 1981 for the first time and has become one of the most used transplants for reconstruction in the head and neck and a widely used transplant for other indications as well. Various complications and functional impairments at the donor site have been reported so far which are presented together with techniques to minimize them, and together with the characteristics, indications and design options of this flap.

Historical description
In 1978, Yang Guofan und Gao Yuzhi harvested a fasciocutaneous radial free flap in the Shenyang Military Hospital for the first time. This transplant got the nickname 'Chinese flap' and became the standard transplant for many indications. In 1981, they described a study of 60 patients with a single transplant loss only. Mühlbauer et al. (1982) were the first who reported upon this transplant outside of China. Stock and contributors raised an innervated flap in 1981 and in 1983, Biemer and Stock utilised an osteocutaneous pedicled transplant for thumb reconstruction. Lovie reported upon an ulnar-based forearm flap in 1984 that was classified as alternative to avoid vascular complications at the donor site by   (Figure 1). Soutar (1983) proposed the forearm flap for reconstruction of the oral cavity, and thereafter the flap became the most utilised technique for intraoral reconstruction. Partecke et al. described a fat fascia only transplant in 1986 which results in a cosmetic appealing scar line. The defect at the recipient site was covered with a splitthickness graft. Finally, tendons and muscles were included in the transplant as well www.intechopen.com Maxillofacial Surgery 30 (Cavanagh et al., 1991). To improve the donor site morbidity, Webster and Robinson (1995) as well as S.C. Chang et al. (1996) described a suprafascial raised forearm flap in the 1990s but there were no differences demonstrable concerning the sensory outcome. Wolff and colleagues (1995) described a prefabricated fascial-split-thickness flap, and Rath and contributors (1997) widened the technical varieties by introducing a prelaminated fasciomucosal flap that was raised after six weeks. Interesting are the work of Costa and colleagues (1993) who used silicon moulds, silicone tubes and split-thickness grafts to reconstruct mouth, nose or ear, and the work of Pribaz und Fine (1994) who provided auricular cartilage into the flap to reconstruct the nose. Besides titanium mesh together with a free forearm flap can be used for reconstruction in the head and neck (Hashikawa et al., 2006;Kubo et al., 2009

Important anatomical variations
Important anatomical variations in regards with the free forearm flap transfer were reported, and should be described briefly. The raised forearm flap area should not extend beyond the antecubital fossa and the radial or ulnar borders to avoid complications and sensory impairment. Yang et al. (1981) described a forearm flap of 35x15 cm, but the dimensions of the forearm transplant are limited by the bifurcation of the forearm arteries at the level of the antecubital fossa.
Both, the radial and the ulnar artery participate in the blood supply of the palmar arches but show in only 27-35% equal supply to the hand and fingers (Coleman & Anson, 1961;Jaschintski, 1897).
In 4, 31 % (McCormack, 1953), the radial artery possesses an unusual course: a dorsal course in the distal third (Otsuka & Terauchi, 1991), a deep course beneath the pronator teres muscle (Small & Millar, 1985) and a superficial course on the brachioradialis muscle (Saski et al., 1999). These variations are explained by the origination of the radial artery from the anterior interosseous artery and the superficial brachial artery, respectively. In those cases a precise examination of the forearm vessels and its dominance is necessary preoperatively. Mc Cormack (1953) described in a study with 750 bodies, the origination of the radial artery from the axillary artery in 2.13%, in 5.7% a superficial brachial artery that courses medial to the biceps muscle, in single cases a superficial radial artery and in 4.43% a median artery. Besides, McCormack found www.intechopen.com The Forearm Flap -Indications, Appropriate Selection, Complications and Functional Outcome 33 an origination of the ulnar artery from the axillary artery in 0.93%. A median artery originates from the brachial artery and runs through the two bellies of the pronator teres muscle. A superficial ulnar artery is found in about 2-9% (Devansh MS, 1996;McCormack,1953;Weathersby 1956). It runs on the flexor muscles but beneath the palmaris longus muscle and the flexor carpi ulnaris muscle. The last muscle can be absent in these cases. Radial or ulnar artery dominace can be a hint for presence of a superficial ulnar artery or median artery, which can be used for elevation instead of the dominat artery (Bell et al., 2011;Davidson et al., 2009).
The venous drainage of the forearm is guaranteed equally by the subcutaneous veins and the venae commitantes. Consequently, the subcutaneous veins can be preserved or serve for a vein graft. A transplant based on the deep venous system shows advantages in older patients (Weinzweig et al., 1994) and avoids the risk provided by veins venipunctured a few days or weeks ago (Hallock, 1986) and facilitates the prevention of cutaneous nerve damage. The superficial venous system shows high variety in size, dominance and course. Numerous anastomoses exist between the superficial veins, the deep veins and the deep and superficial venous system.

Characteristics
The distinct qualities made the forearm flap to the workhorse in head and neck reconstruction. It is possible to place the flap more proximal or distal without risking the vitality of the flap. The forearm flap provides constant anatomy, is simple and rapid to harvest, possesses many kinds of alternatives in supplying arteries, veins and nerves and shows good vascularisation that results in high vitality and tolerance to radiotherapy (I.A. McGregor & F.M. Soutar & Tanner, 1986). In this regards, this flap excels by its long and large-caliber vascular pedicle and nerves permitting a contralateral anastomosis and the by-passing of vascular defects, even after a neck dissection. The relative large diameter of 2 mm protects from thrombosis and the vessels show seldom sclerotic changes. But de Bree et al. reported a sclerotic impaired radial artery which precluded an anastomosis . The flap is thin explaining its pliability, contourability, consistent volume and surface over time. Together with the possibility of harvesting innervated flaps and the relative few hair growth, these are the main reasons for satisfactory aesthetic and intraoral results. Ahcan et al. (2000) described high sensory potency compared to other flaps. The hair growth on the forearm shows some variety, whereas the ulnar side possesses less hair growth in general. To optimize the aesthetic outcome, skin color, texture, hair growth and skin thickness should be evaluated.
The ulnar artery is a little bit shorter than the radial artery. Advantages consist in a less exposed skin area, in a defect that is easier to close, less hair growth and less risk of nerve damage or numb areas. Becker und Gilbert (1988) described a flap based on the dorsal ulnar artery, which originates from the ulnar artery 2-4 cm proximal to the os pisiforme and has a diameter of 0.8-1.2 mm. This variation can be utilised for a fasciocutaneous pedicled flap of 10x5 cm in size, but has a relative short vessel length. The advantages and disadvantages of the forearm flap are summarized in Table 2.
advantages disadvantages constant anatomy discontent of the cosmetic outcome of this exposed area is possible several altenatives in arteries, veins and nerves necessity of a preoperative doppler sonography to guarantee the blood supply to the hand excellent vascularisation: the lenghth of the artery is 10-18 cm, the diameter about 2 mm, almost no sclerotic changes;→important at surgically difficult recipient sites color differences between the skin of the forearm and the face flap thickness may be varied by flap placement more distal or proximal a longer, more pretentious and exhausting operation compared to a local defect closure simple and rapid to harvest proximal as well as distal scar tissue fixation between the recipient site and the transplant may occur thin→no airway obstruction pliability, contourability: folding in sandwich technique is possible consistent volume and surface over time skin with high sensory (protecting) potency tolerance to radiation therapy infections like osteomyelitis or a osteoradionecrosis often show primary wound healing because of excellent vascularisation several skin islands can be raised at the perforators Table 2. Advantages and disadvantages of the forearm flap

Indications
The forearm serves for a free flap transplant and a pedicled flap as well. Because of the above mentioned advantages and in Table 1 summarized qualtities and characteristics, the forearm flap represents the first therapy option for various kinds of surgical indications with a high overall success rate (Table 3. Complications at the recipient site). It is a highly utilised flap at pretentious recipient sites like the oral cavity, the palate, after a trauma or a tumor resection. The forearm flap replaced the pectoralis major transplant in tongue reconstruction, especially for the oral part of the tongue . The forearm flap particularly serves for the reconstruction of superficial defects. It is used for jaw reconstruction or penile and urethral reconstruction and for coverage of pretibial defects as well, as it is a thin transplant (Biemer, 1988; T.S. Chang and Hwang, 1984). An innervated radial forearm flap is raised with the lateral antebrachial cutaneous nerve and an ulnar forearm flap with the medial antebrachial cutaneous nerve. Innervated flaps could show a faster and increased sensory recovery (Santamaria et al., 1998). Nerve fibers with normal ultrastructure can be found at the recipient site immunohistochemically, in contrast to Waller degeneration and nerve fiber loss in non-innervated flaps (Katou et al., 1995).  and Dubner et al. (1992) could show that innervated transplants result in an increased sensory capacity of the flap, even improved to the surrounding tissue. The flap should not be raised, if one palmar arch is absent, if there exists an absolute artery dominance or if one forearm artery is missing. Bone should not be included, if it shows osteoporotic changes.

Complications, function loss at the donor site and techniques to minimize
Correct planning and elevation prsupposed, there will be no clinically relevant limitatations in strength, motion and hemodynamics in the forearm and hand after free forearm flap transfer. Sensory and cosmetic outcome is perceived as non-disturbing . The complication rates and the rates of function loss at the donor site are summarized in Table 4.
To optimize the functional and aesthetic outcome at the donor site, different techniques and tests can be applied. A preoperative Doppler sonography is suggested before raising the forearm flap . Cases of acute ischemia of the hand were described, although a preoperative assessment with the Allen's test was performed. An absence of a forearm vessel, one palmar arch (in about 4,5%) (Partecke & Buck-Gramcko, 1984), or an absolute dominance of one vessel can lead to an inadequate blood supply of the forearm and hand. Only in those cases, vascular diseases or young patients (Kropfl et al., 1995), a vein graft seems to be profitable . Heller et al. (2004) described a patient with finger necrosis months after the operation, caused by an absent deep palmar arch, and the subsequent reconstruction of the radial artery. Circia-Llorens et al. (1999) could prove that the remaining forearm vessels, especially the anterior interosseous artery, show an increase in diameter and flow. It could be shown that this vessel forms an anastomosis with the vessel stump of the harvested artery.
Complications at the donor site total patients with complications 14-33% 16   Wound healing problems can result in impaired functional outcome. A limited wrist and finger motion and decresed muscle strength can result from graft necrosis, exposed tendons, and subsequent adherent scar formation (Kröpfl et al.). A careful coverage of the tendons with flexor muscles guarantees a plain wound for the split-thickness graft. The paratenon should be preserved, the flap can be placed more proximally and the arm should be immobilized in extension to achieve an optimal wound healing. If muscle or bone is included in the flap, the wound healing is delayed and the risk of wound healing problems is increased. Vacuumtechnique (Argenta & Morykwas, 1997) can assist wound healing in complicated cases. A short-time hyperalimentation should be considered in tumor patients as well.
A careful preparation, together with an oblique incision to avoid dead space, especially when thick subcutaneous tissue is present, avoid hematoma and seroma formation and leads to an improved healing of the split-thickness graft.
The fracture rate after an osteocutaneous ulnar or radial transplant varies between 8 and 43% but can be decreased by physiotherapy, harvesting not more than one third of the bone, performing a "boat-shaped" osteotomy, that decreases the stress concentration effect by 5% (Meland et al., 1992), and immobilizing the arm in extension for 6-8 weeks (Partecke & Buck-Gramcko, 1984). A control radiography should be performed before and after the operation.
All different kinds of objective (quantitative, qualitative, dissociated) and subjective sensory impairment were described subsequently to the free forearm flap transfer. But in general, the patient states that he is not affected in his daily activities. Table 5 summarizes the frequencies of disturbed sensory modalities and qualities after free forearm flap transfer.
www.intechopen.com  Initially, sensory disturbances can be found in 17-75% but decrease during the next months. Hypersensitiveness, paresthesias and dysesthesias can signal sensory regeneration. However, hyperesthesia and neuralgia could signal nerve section, but decrease in the following months, too. Together with pain due to neuroma formation or causalgia, they are difficult to treat, what underlines the importance of careful preparation and good vascularisation to prevent perineural scar formation and assist nerve regeneration.  described four neuromas in a group of 86 patients making a surgical neuroma excision necessary . The nerve endings should be covered with muscle and not come into contact with the split-thickness skin graft. Although it is not possible to preserve the cutaneous nerves in each case, e.g. the lateral antebrachial cutaneous nerve or the superficial radial nerve, an ulnar-based flap and the limitated dimension to the radial or ulnar border can improve sensory outcome .
It is not surprising that women are more pretentious with regard to the aesthetic outcome at the forearm. Alternatives for achieving the optimal cosmetic result are dicussed in Table 1 and the following paragraph.  described in their group of 267 patients after closing the defect with split-thickness graft, reduced pigmentation in 43.4%, increased pigmentation in 15%, level differences > 0.1 cm in 46.8%, but in only 12% >0.4 cm, an unstable scar in 10.5% and an adherence of the defect in 18.7%. Adequate compression, first with dressings and later with compression stockings, and the application of 2 mm metal plates can assist the wound healing.

Closure of the donor site
The most utilised technique to close the defect at the donor site is the coverage with 0.2-0.6 mm split-thickness skin grafts. Lutz and colleagues described a success rate of 98% compared with 84% in full skin grafts . However, if the wound is not plain, e.g. above a tendon, opposite results can be found as well. Other studies showed a complete loss of the split-thickness skin graft in 8 ) -16% , a partial loss in 16-35% (Bardsley et al., 1990;, and a loss of splitthickness skin grafts in suprafascial elevated flaps in 0-4% (Avery et al., 2001, Chang et al., 1996. Patients are more content with full skin grafts than with splitthickness grafts: 92% to 57% . Defects up to 4x8 cm in size can be closed with a V-Y transposition flap (Elliot et al., 1996). Enough skin should be disposable to avoid limitations in wrist extension, chronic lymphatic edema, sensory disturbance of the forearm or necrosis. Another alternative of closure is skin expansion that can be primary (Bardsley et al., 1990;Herndl & Mühlbauer, 1986) or secondary. Because of wound healing problems in about 30%, Hallock (1988) recommends for the secondary skin expansion a coverage with split-thickness skin graft , in the first instance. After six weeks, it is possible to begin the expansion. A secondary shrinking and a thinning out of the subcutaneous tissue needs to be considered. The skin area of the harvested transplant should never be expanded as a shrinking at the recipient site would be the consequence. The flap preparation should begin from the region opposite to the expanded area to avoid shrinking during the operation. However, a disturbance of the microcirculation with venous congestion might still occur. Dehiscence after expansion was described in up to 40% , but other studies showed complication rates of less than 10% .

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The Forearm Flap -Indications, Appropriate Selection, Complications and Functional Outcome 39

Conclusion
Microvascular surgery often presents the only possibility to reach satisfactory functional, and cosmetic outcomes and to achieve acceptable quality of life for reconstruction in the head and neck. Due to distinct charactersitics the forearm flap is one of the most used transplants for reconstruction in the head and neck and a widely used transplant for other indications as well. Correct planning and elevation presupposed the flap success rates average at least 90% with no relevant limitations in strength, motion and hemodynanics in the forearm or hand and non-disturbing sensory and cosmetic outcome at the donor site. Table 3 Complications at the recipient site Table 4 Frequencies of complications and function loss at the donor site Table 5 Frequencies of sensory impairment at the donor site after fasciocutaneous forarm flap transfer