The radial forearm consists of thin, pliable skin that can be molded in three dimensions and transferred as a sensate flap, making it ideal for most head and neck reconstructions.
Loss of tissue resulting from cancer ablation or debridement of infected tissues or secondary to trauma provides the reconstructive surgeon with various challenges. Regional flaps such as the pectoralis major and deltopectoral flaps have been used by reconstructive surgeons since the early 1900s. These flaps are still useful for head and neck reconstruction in select cases; however advances in reconstructive techniques have led to a shift favoring free tissue transfer (see the image below). Microvascular techniques have allowed surgeons to readily transfer tissue from one region of the body to another. In the ideal situation, one must replace tissue lost with tissue that has similar characteristics. In the head and neck, tumor extirpation may result in loss of the thin mucosal covering of the oral cavity, pharynx, or larynx.
Reconstruction of such defects requires transposition of thin, pliable, and, preferably, sensate tissue to optimize function. A long vascular pedicle is beneficial because the vessels used for the anastomoses are usually found in the neck. The decision about which flap to use is based on the defect size, the type and amount of missing tissue, necessary pedicle length, and requirements for reinnervation.
The reliable anatomy of the forearm makes flap harvest relatively easy and safe. The long pedicle allows anastomoses to be performed on either the ipsilateral or the contralateral neck. The flap may also be harvested with the palmaris longus tendon, radial bone, and/or sensory nerves, making it extremely versatile. The cephalic vein may be harvested as the sole venous outflow or as an optional accessory to the venae comitantes. (See the images below.) 
History of the Procedure
The microvascular radial forearm flap was first described in the Chinese literature in the early 1980s. The Chinese flap became known for its reliable anatomy, pliable skin, ease of elevation, and long pedicle. The biggest drawback was the relatively unsightly donor site appearance. Multiple techniques to improve the appearance of the donor site have been published, but to date there is no consensus on the ideal technique. Functional and cosmetic outcomes appear similar with split- or full-thickness grafting or with acellular dermis covered with a thin split-thickness graft.
The development of an osteocutaneous flap, which included a segment of the radius, increased the utility of the radial forearm flap. As originally described, however, the harvested bone weakened the remaining radius and was associated with a 25% fracture rate. Modifications of harvest technique and prophylactically plating the radius have virtually eliminated this problem and expanded the reconstructive versatility of this flap. Very little other long-term morbidity has been associated with this flap.
Ease of harvest, versatility, and unsurpassed reliability have made the radial forearm flap the fasciocutaneous flap of choice for head-and-neck reconstructive surgeons. It has many uses, ranging from reconstruction of skin and scalp defects to repair of composite intraoral defects. A fascial flap may be harvested to repair skull base defects, and partial or total pharyngectomy defects can be repaired with the flap tubed or sewn as a patch to the remaining pharynx. It is the best source of healthy, vascularized skin without the bulk of a myocutaneous flap for reconstructive surgeons trained in microvascular techniques.
Transfer of tissue from the forearm to the head and neck can be performed effectively with microvascular techniques. Various defects can be successfully repaired with this flap.
The patient is preoperatively evaluated by both the extirpative and reconstructive surgeons. Medical and radiation oncology consultations are obtained, when appropriate. A speech pathology evaluation is often performed as well, if indicated. An Allen test is an integral part of the physical examination and must be performed on all patients considered to be candidates for a radial forearm free tissue transfer. Any previous scars or surgery to the forearm is a relative contraindication.
Radiographic images are reviewed, and the surgery is discussed in detail with the patient. Assessment of patient support systems and the patient's educational and social status is useful.
Deciding which flap would offer the best functional and cosmetic outcome is based on multiple factors, including defect size (diameter, depth, bulk), location, and missing components (eg, skin, muscle, bone). Patient factors, such as contraindications to a particular flap, systemic diseases, and overall health must also be considered. Potential donor site morbidity as related to each patient must be considered. Training of the surgeon is, of course, paramount in the decision-making process.
The tissue from the forearm harvested as a radial forearm flap allows various head and neck defects to be reconstructed with a vascularized, thin, pliable piece of fascia and skin. This is advantageous in patients with complicated three-dimensional defects (as seen below), circumferential pharyngeal defects, and oral or scalp defects, especially those who have undergone prior irradiation. Small defects involving bone may be reconstructed by harvesting vascularized radius. Caution is necessary because of the possibility of radial fractures following bone harvest, but the likelihood of such fractures is minimized by harvesting the bone in a keel shape (beveling the proximal and distal cuts) and prophylactically having the bone plated postharvest by an orthopedic surgeon.
As in any procedure, intimate knowledge of the anatomy is key. The anatomic consistency of the forearm is one of the most attractive aspects of the radial forearm flap. The volar aspect of the forearm contains 2 major arteries (radial and ulnar) with their accompanying venae comitantes. The ulnar artery and its venae comitantes lie along the medial aspect of the arm. Although it is usually deep and protected during dissection, the ulnar vessels are sometimes quite superficial (see the image below).  Extra care and attention during the medial dissection help to avoid transecting this pedicle, which would compromise circulation to the hand.
The radial vessels lie laterally (thumb side) in the arm. The pedicle is found in the lateral intermuscular septum, between the flexor carpi radialis (FCR) medially and the brachioradialis (BR) laterally. There are two venae comitantes that run parallel to the radial artery in the intermuscular septum which usually join into one vein in the proximal third of the forearm. The cephalic vein lies superficially along the lateral arm. This vein can be harvested with the flap or left in the arm if venous drainage from the venae comitantes is sufficient.
Medial and lateral antebrachial cutaneous (MABC and LABC) nerves supply the skin of the forearm. With elevation of the flap, they are identified and isolated proximally. The LABC lies in proximity to the cephalic vein. This nerve provides sensation to the lateral digits. Superficial branches of the radial nerve lie lateral to the BR tendon distally. Pay attention when elevating a radial forearm flap to preserve the integrity of this important nerve.
The palmaris longus, absent in 5-15% of patients, is a tendon that may be harvested with the flap. It lies medial to the FCR. It can be used to provide support for lip or midface reconstruction as a vascularized sling. 
The most important contraindication for harvesting a radial forearm flap is related to the vascular supply of the hand. The deep and superficial palmar arches, arising from the radial and ulnar arteries respectively, normally anastomose to provide the blood supply to the hand and digits. A small number of individuals have a superficial arch that does not join with the deep arch; if the radial artery is sacrificed, these patients are at risk of ischemia of the first finger and thumb, an unacceptable morbidity for this procedure.
An Allen test should be performed preoperatively in all patients to assess ulnar collateral flow in the thenar region (see the image below). This is performed by manually occluding both the radial and ulnar arteries simultaneously. The patient clenches his/her hand, causing the palm to blanch, and then opens it to a relaxed position. If the fingers are extended straight out, they may blanch from overextension, which may lead to a false-positive result.
The ulnar artery is released, and return of color is evaluated, especially in the region of the thenar eminence. If flow is questionable or if the patient is pale and flow is difficult to assess, a Doppler device may be placed in the thenar region and the test repeated. The return of a pulse should be audible with release of the ulnar artery.
Pulse oximetry may also be used by placing the oximeter on the thumb. When the radial and ulnar arteries are occluded, the signal should be lost; if, when the ulnar artery is released, the signal returns, the test is negative and one can proceed with the surgery. A quantitative Doppler study, although more time consuming and expensive, may also provide information if the test results are uncertain.
A questionable or positive Allen test result should prompt the surgeon to select a different flap. Approximately 3-5% of the population manifests such a finding.
Another relative contraindication to a radial forearm flap is a history of surgery on the ipsilateral hand. If operative reports can be obtained and the vascular supply to the hand is found to have not been disrupted, the flap can be considered. The presence of an ipsilateral arteriovenous (AV) shunt in a patient with persistent renal failure is an absolute contraindication to a forearm flap; the presence of a contralateral AV shunt is a relative contraindication to surgery.
Although the radial forearm flap remains an excellent supply of fascia and skin, alternatives do exist. In the setting of contraindications to a radial forearm flap, the surgeon should consider these alternatives. An ulnar fasciocutaneous flap shares many of the radial forearm flap's properties, although it cannot be designed as an osteocutaneous flap.
Other available fasciocutaneous free flaps include scapula, lateral thigh, and lateral arm flaps. Although well suited to most skin or mucosal and fascial defects in the head and neck, all flaps must be tailored to the specific patient. A fibula or iliac crest flap is probably a better choice for large bone defects or in patients who desire osseointegrated implants for dental restoration. Large defects of the tongue or of the orbit may necessitate more bulk and are better replaced with a rectus or latissimus flap.