Ulnar Artery Perforator Flap
Kevin C. Chung
The ulnar artery perforator flap was first described by Becker as a pedicled flap based on the dorsal branch of the ulnar artery (FIG 1).1 The mobility of this flap is limited by its short pedicle.
The ulnar artery perforator flap is most commonly used as a pedicled flap. Alternatively, it can be harvested as a free flap.
A major advantage of perforator flaps is the preservation of the major vessels of the forearm; the ulnar and radial arteries are not sacrificed.
The ulnar artery perforator flap can be used for coverage of defects of the ulnar hand and wrist, both dorsal and volar, typically up to 10 × 5 cm in size.1
Larger flaps, up to 20 × 9 cm, can be harvested, but venous congestion can result.3
Supercharging a larger flap by anastomosing a subcutaneous flap vein to a nearby vein of the dorsal hand can improve venous outflow.4
The flap can be raised as a fasciocutaneous or adipofascial flap.
The hand is supplied by the radial and ulnar arteries that branch from the brachial artery over the antecubital fossa, 1 cm distal to the elbow joint. The ulnar artery travels distally beneath the flexor carpi ulnaris (FCU), volar to the flexor digitorum profundus. Perforators from the ulnar artery travel to the overlying fascia and skin between the FCU and the flexor digitorum superficialis. The superficial and deep palmar arches are located in the palm, formed by the radial and ulnar arteries.
Sacrifice of the radial or ulnar artery for flap elevation risks hand ischemia if the patient does not have an intact palmar arch. Perforator flaps may be safely used in these cases.
The ulnar artery gives off seven ± two perforators to the skin over the ulnar forearm with a diameter of 0.5 mm or greater.5
The pedicle length for propeller or free flaps based on these perforators is 3.3 mm on average, ranging from 2.5 to 4.0 mm.5
About 69% of the perforators of the ulnar artery are musculocutaneous, traveling through the FCU or flexor digitorum superficialis to reach the skin.5
The remaining perforators are septocutaneous.
The ulnar artery perforator flap can be designed as a propeller flap based on the dorsal branch of the ulnar artery. It can be harvested up to 15 cm in length, to the mid-forearm, depending on the location of the perforator.
Greater pedicle length can be obtained when the flap is based on the ascending branch of the dorsal branch of the ulnar artery.
The dorsal branch of the ulnar artery arises from the ulnar artery 2 to 5 cm proximal to the pisiform.6
Infrequently, in 2 of 26 cadaver dissections, the dorsal branch arises from the anterior interosseous artery rather than from the ulnar artery.7
The dorsal branch of the ulnar artery has a diameter of 1.0 to 1.3 mm.2 It travels from the volar distal forearm from radial to ulnar, under the FCU, to give off three branches:
The proximal branch enters the FCU 4 to 6 cm proximal to the pisiform.
The distal branch supplies the pisiform. It is called the pisiform artery.
The middle branch divides into an ascending and a descending branch 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 can be designed based on the ascending branch of the dorsal branch of the ulnar artery and its two vena comitantes.2
The ulnar artery perforator flap can be designed from the palmaris longus tendon volarly to the extensor digitorum communis tendon of the fourth finger dorsally.8
The ulnar artery perforator flap is approximately 3 mm thick, providing thin soft tissue coverage.5
The ulnar artery perforator flap is designed along the flap axis between the medial epicondyle and the pisiform (FIG 3). Proximally, the perforators are larger and more consistent and primary donor-site closure is easier.
When used as a free flap, the ulnar artery perforator flap is typically designed over the proximal forearm.
The dorsal sensory branch of the ulnar nerve passes beneath the FCU 5 to 8 cm proximal to the pisiform to travel to the dorsal forearm. It is protected during dissection of the dorsal branch of the ulnar artery.
Flaps widths up to 6 cm can be closed primarily over the ulnar forearm. Wider flaps require closure with a split-thickness skin graft (STSG).
Bone defects of the small finger metacarpal can be reconstructed by harvesting vascularized cortical bone of the ulna with the ulnar artery perforator flap.9
Bone is harvested from the ulna 10 to 15 cm proximal to the pisiform between the FCU and extensor carpi ulnaris (FIG 4).
FIG 3 • To design an ulnar artery perforator flap, the medial epicondyle, pisiform, and FCU are marked. Next, the axis of the ulnar artery perforator flap is marked from the medial epicondyle to the pisiform. Ulnar artery perforators are identified along this line using a Doppler ultrasound. The flap is designed to include as mainly audible perforators as possible.
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