How to Raise an Ulnar Free Forearm Flap: Demonstration of the Surgical Technique with Adjuncts and Refinements

The forearm still represents a widely used donor site for harvesting free microvascular flaps for head and neck reconstruction. Although the time-honored radial forearm flap enables a reliable soft-tissue replacement for the orofacial region, including the possibility of harvesting an osteocutaneous flap, some concerns have recently arisen regarding the esthetic impairment of the donor site and especially the inconvenient hair growth in the reconstructed area once the flap is used for oropharyngeal lining.1 Alternatively, the ulnar free forearm flap (UFFF), initially described by Lovie et al,2 can be raised as a septocutaneous flap based on the septocutaneous perforators of the ulnar artery. It provides comparable advantages in view of reliability, thickness, size, and pedicle length.1 Although the USFF is only harvested as a septocutaneous transplant, it offers specific features such as an inconspicuous donor site and far less hirsute transplant than its radial counterpart. At last, it leaves fewer uncovered tendons of the flexor muscles after raising the flap, allowing enhanced healing of a full-thickness skin graft for reconstruction of the donor site skin.3 The ulnar artery is rarely dominant at the forearm level, and there is no hemodynamic reason to prefer the radial artery to the ulnar artery for any invasive endovascular maneuvers or artery graft harvest.4 Nevertheless, the decision regarding flap choice is made after the clinical Allen test. Still, the selection may also be influenced by hand dominance as well (right-handed or left-handed patient). If applicable, the general recommendation would be to harvest the flap based on a nondominant artery from the nondominant hand. Although the UFFF has frequently been described and reviewed, including harvest technique, outcome, and donor-site morbidity,3,5 it has never gained the same popularity as its radial pendant. This is mainly due to three aspects: first, the deep location of the ulnar artery and its comitant veins between the flexor carpi ulnaris and flexor digitorum superficialis, which aggravates the palpation of its pulsation. Second, is the spatial relationship to the underlying ulnar nerve, from which the vascular pedicle must be separated along a reasonable distance. Third, the absence of reliable superficial vein drainage, such as the cephalic vein on the radial side. Recent publications, however, challenged these claims, providing evidence on the preserved motor and sensory function and vascular perfusion of the hand.1 This video contribution aims to demonstrate the harvesting technique step-by-step and encourage surgeons to raise the UFFF routinely. SURGICAL TECHNIQUE AND STEPS Video 1 The ulnar artery runs deep between the flexor carpi ulnaris and flexor digitorum superficialis along a line drawn from the medial epicondyle of the humerus to the pisiform bone. The surface anatomy of the vascular pedicle starts about 1 cm below the antecubital fossa, following the junction of this line’s upper and middle thirds running distally along the line. Therefore, the flap is centered on the middle and lower thirds of this line, which is used as an axis for the flap. After the application of a tourniquet, a skin incision at the distal border of the flap is performed, and careful dissection begins between the flexor carpi ulnaris and flexor digitorum superficialis to expose the vascular pedicle and separate it from the underlying ulnar nerve. The ulnar artery and the two comitant veins are clamped, transected, and ligated. Afterward, subfascial dissection of the skin flap is performed on the radial aspect to elevate it from the flexor muscles. At this step, perforator vessels are visible within the septum. Retracting the flexor digitorum superficialis laterally, the vascular pedicle is visualized and can be dissected proximally. Now, the flexor carpi ulnaris is dissected toward the intermuscular septum. The median vein of the forearm is encountered at the proximal border of the flap. It can be used for alternative venous drainage of the flap or ligated. [See Video 1 (online), which displays marking the surface anatomy of the ulnar artery as a landmark for flap design and initial incision to expose the vascular pedicle distally.] {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 1","caption":"displays marking the surface anatomy of the ulnar artery as a landmark for flap design and initial incision to expose the vascular pedicle distally.","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_tlr4zm3p"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} Video 2 The ulnar nerve is dissected from the intermuscular septum on the radial aspect and separated from the vascular pedicle. Perforator vessels passing into the flexor digitorum superficialis are cauterized or ligated. After retraction of the flexor carpi ulnaris, the same technique is applied to dissect the ulnar nerve from the muscle on the ulnar aspect. The flap is dissected through the subfascial plane, and the deep fascia that encircles the palmaris longus is divided. Special attention should be paid to preserving the paratenons and not damaging the fasciocutaneous branches emerging from the intermuscular septum. [See Video 2 (online), which displays the distal dissection of the vascular pedicle, separating it from the underlying ulnar nerve within the boundaries of the skin flap.] {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 2","caption":"displays the distal dissection of the vascular pedicle, separating it from the underlying ulnar nerve within the boundaries of the skin flap.","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_v9o0fa34"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} Video 3 The vascular pedicle is separated from the underlying ulnar nerve. The dissection is now completed on the radial side, preserving the intermuscular septum. Larger perforator vessels are ligated, whereas smaller ones can be cauterized. As soon as this is performed under the skin flap, the vascular pedicled is followed proximally. In patients with excess skin, a full-thickness skin graft may be harvested in this region to cover the donor site. The resulting defect is now considered to modify the course and shape of the skin incision line between the two skin defects to create a lazy S-shape. The proximal donor site can be closed directly by undermining and approximating the wound edges, whereas the distal one is covered by the meshed full-thickness graft. [See Video 3 (online), which displays completing dissection of the vascular pedicle and harvest of the full-thickness skin graft proximally.] {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 3","caption":"displays completing dissection of the vascular pedicle and harvest of the full-thickness skin graft proximally.","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_x2zuqlxr"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} Video 4 After the full-thickness graft is harvested, the skin is incised between the two skin defect sites and extended into the antecubital fossa. Blunt finger dissection separates the flexor digitorum superficialis from the flexor carpi ulnaris, thus exposing the vascular pedicle, which runs deep to the pronator teres, the flexor carpi radialis, the palmaris longus, and the flexor digitorum superficialis at the upper third of its course in the forearm. The vascular pedicle is now followed into the antecubital fossa to obtain an appropriate pedicle length. Finally, the tourniquet is released to check the flap perfusion and perform hemostasis before ligating the vascular pedicle and definitive flap harvest. [See Video 4 (online), which displays the final dissection of the vascular pedicle and reperfusion of the UFFF.] The full-thickness skin graft is secured by a tie-over or vacuum assisted closure dressing, and the forearm is provided with an elastic bandage and immobilized for 10–14 days on a volar support splint in an intrinsic-plus position. {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 4","caption":"displays the final dissection of the vascular pedicle and reperfusion of the UFFF.","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_3urw857w"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} DISCLOSURE The author has no financial interest to declare in relation to the content of this article.