The Lateral Arm Flap
The lateral arm flap is a useful fasciocutaneous flap based on the posterior radial collateral artery (PRCA). It was first described by Song et al1 in 1982 as a free flap and popularized by Katsaros.2 It has a constant arterial anatomy, and it can be used as both a pedicled and a free flap. The vascularity of the hand is unaffected by raising this flap, since it is based on a nondominant artery, which enables its use from the same limb in trauma cases.
The lateral arm flap can be used for coverage of defects of the volar and dorsal carpus and hand.
It can be used as a composite osteoseptocutaneous flap for immediate thumb reconstruction with or without vascularized tendon.
It has been described for reconstruction of segmental bone and soft-tissue defects of the forearm.
Previous surgery or penetrating trauma to the arm or a history of fracture of the distal humerus represent potential causes of injury to the PRCA that preclude use of this flap.
General contraindications to free tissue transfer apply, include bleeding disorders or a hypercoagulable state.
Marked upper arm edema precludes use of a pedicled flap.
No special imaging is required, because the PRCA is a constant vessel that is identified with a Doppler probe intraoperatively.
The lateral arm is perfused by the PRCA, one of the terminal branches of the profunda brachii. The average vessel diameter in one series was 1.5 mm for the artery (range: 1.0–2.5 mm) and 2.5 mm for the vein (range 1.0–3.0 mm) ( Fig. 43.1a,b ).
It has a large fascial component located anterior and posterior to the lateral intermuscular septum, which itself lies between the triceps posteriorly and the brachialis and brachioradialis muscles anteriorly. In one anatomical study, at least one vessel entered the proximal 5 cm and one vessel entered the distal 5 cm of a harvested strip of triceps tendon.
The PRCA provides at least four fascial branches taking off from 1 to 15 cm proximal to the lateral epicondyle, the largest of which is located at an average of 9.7 cm superior to the lateral epicondyle. Fascial flaps of up to 12 × 9 cm may be used.
The PRCA consistently divides into two terminal branches: an anterior and a posterior division. The anterior division is the nutrient vessel of the flap. This artery extends distal to the lateral epicondyle of the elbow onto the lateral aspect of the proximal forearm, which is the basis for raising an extended fasciocutaneous flap from the proximal forearm.
A distally planned lateral arm flap capitalizes on an anastomotic network between the posterior collateral radial artery and the recurrent radial artery, which allows the skin paddle to be safety located over the epicondylar region or over the proximal forearm from 6 to 10 cm distal to the lateral epicondyle. This modification increases the pedicle length from 11 to 17 cm and limits the amount of subcutaneous fat.
One or two branches of the posterior collateral artery consistently supply the bone between 2 and 7 cm proximal to the lateral epicondyle, which lends itself to the design of an osteocutaneous flap.
The patient is placed supine with the arm abducted on an arm board, with an upper arm tourniquet. General anesthesia or brachial block is usual.
The flap is centered over a line joining the deltoid insertion with the lateral epicondyle, which is the course of the lateral intermuscular septum, which contains the PRCA ( Fig. 43.2 ).
The flap can be as large as 9 × 32 cm.
The posterior radial collateral artery is identified with a Doppler probe. The incision starts posteriorly and extends down to the triceps fascia. The fascia is dissected off the triceps and sewn to the skin.
The dissection proceeds to the lateral intermuscular septum, which is included in the flap. The most difficult area is at the proximal aspect of the skin paddle, where multiple perforators to the triceps and brachioradialis muscles must be ligated. Achieving appropriate exposure for the proximal dissection of the pedicle dissection can also be limited if the lateral head of the triceps muscle is not completely detached.
Once incised, portions of the flap distal to the epicondyle are raised directly off the antebrachial fascia. Above the level of the epicondyle, the muscular fascia of the lateral head of the triceps is incised lateral to the triceps tendon.
The dissection proceeds directly on the lateral head of the triceps toward the intermuscular septum. Similarly, the anterior dissection proceeds deep to the fascia directly over the brachialis and the brachioradialis muscles.
The radial nerve is identified between the brachialis and brachioradialis muscles. As the dissection proceeds superiorly, the vascular pedicle is separated from the radial nerve in the radial groove.
The posterior cutaneous nerve of the arm and posterior cutaneous nerve of the forearm are both identified as they leave the radial nerve to enter the flap skin or the intermuscular septum, respectively. Frequently, the posterior cutaneous nerve of the arm pierces the triceps, and a small portion of triceps must be divided to obtain maximum length on the nerve.
The flap is then raised by dividing the PRCA and taking the septum along with the radial recurrent artery and venae comitantes up to the lateral epicondyle ( Fig. 43.3 ). The vessels can be harvested at a proximal point where there is a single predominant vein. If two venae comitantes of equal diameter are present, only one venous anastomosis is theoretically necessary because of multiple venous interconnections ( Fig. 43.4 ).
Once the flap is harvested, the skin paddle is inset and the microvascular anastomoses are then performed ( Fig. 43.5a.g ).
The donor site can be closed primarily in most cases if the width of the skin paddle is less than 5 cm or even up to 8 cm with lax skin. If a wider flap is needed, a skin graft is placed directly over the muscle after the triceps and brachialis muscles are sutured over the radial nerve.
A bulky splint is applied, holding the wrist in neutral, and with a drain for the initial 1.2 days. The patient is admitted for flap monitoring and arm elevation. The use of anticoagulation is at the surgeons’ discretion.
The flap is bulky and may require debulking. The donor-site scar can be prominent.
The usual vascular pedicle is relatively short (2.6 cm).
Variations in vascular anatomy have been reported. The most common anomaly is duplication of the PRCA, which can lead to flap failure if unrecognized.
Immediate complications following free flap transfer include failure of the arterial or venous anastomosis with flap loss.
Raising the flap usually involves transection of the PCNF, which results in an area of numbness over the lateral aspect of the elbow and dorsolateral forearm. In a series by Katsaros and colleagues, the average sensory deficit was found to be 90 cm2 (13 × 7 cm).
A radial nerve neuropraxia can occur.
The risk of supracondylar fracture of the distal humerus following vascularized bone harvest has prompted some authors to stabilize the bone defect with a prophylactic locking compression condyle plate (LCP).
Reconstructions of extensor tendon defects with vascularized triceps tendon have disappointing excursion.