Radial Forearm Tissue Transfer 

Microvascular techniques have allowed surgeons to readily transfer tissue from one region of the body to another. 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 desirable because the vessels used for the anastomoses are usually found in the neck. The decision about which flap to use for head and neck reconstruction is based on the defect size, the type and amount of missing tissue, necessary pedicle length, and requirements for reinnervation.

When thin mobile skin that can be molded in 3 dimensions is required, the radial forearm flap is the criterion standard of donor sites. The reliable anatomy of the forearm makes harvest relatively easy and safe. The long pedicle allows anastomoses to be performed in either the ipsilateral or the contralateral neck. The flap may be harvested with the palmaris longus tendon, radial bone, and/or sensory nerves. The cephalic vein may be harvested as the sole venous outflow or as an optional accessory to the venae comitantes.^[1]

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, which is typically skin grafted. Techniques to improve the appearance of the donor site are still being developed. 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.

Unsurpassed reliability has made the radial forearm the preferred fasciocutaneous flap of 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. 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 the extirpative and reconstructive surgeons. Medical and radiation oncology consultations are obtained, when appropriate. A speech pathology evaluation is often performed as well. An Allen test is performed as part of a full history and physical examination. Any previous scars or surgery to the forearm is a relative contra indication.

Radiographic images are reviewed, and the surgery is discussed in detail with the patient. Assessment of patient support systems and their 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, 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 3-dimensional defects, 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.

Anatomic consistency of the forearm is one of the most attractive aspects of this 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, sometimes quite superficial (see the image below). Extra care and attention during the medial dissection helps to avoid transecting this pedicle.

The radial vessels lie laterally (thumb side) in the arm. The pedicle is found between the flexor carpi radialis (FCR) medially and the brachioradialis (BR) laterally. The cephalic vein lies superficially along the lateral arm. 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. Superficial branches of the radial nerve lie lateral to the brachioradialis tendon distally. This nerve provides sensation to the lateral digits. 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.^[2]

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; these patients are at risk of ischemia of the first finger and thumb if the radial artery is sacrificed.

An Allen test should be performed preoperatively 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 first 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 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. A quantitative Doppler study may also provide information if test results are uncertain. A questionable or positive Allen test result should lead 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 of the ipsilateral hand. If operative reports can be obtained and the vascular supply to the hand was not disrupted, the flap can be considered. 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.

The advent of other readily accessible flaps that provide similar tissue has made taking a radial forearm flap from the dominant arm a relative contraindication.

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 properties of the radial forearm flap 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 than an osteocutaneous forearm flap. Large defects of the tongue or of the orbit may necessitate more bulk and are better replaced with a rectus or latissimus flap.