Residency · Residency · Plastic Surgery

Workhorse Free Flaps: Anterolateral Thigh and Radial Forearm

Overview

The anterolateral thigh (ALT) and radial forearm free flaps are two of the most commonly used free flaps in reconstructive surgery. They are considered "workhorse" flaps because of their versatility, reliable anatomy, ease of harvest, and acceptable donor site morbidity. Both are critical tools for head and neck reconstruction and extremity reconstruction. ---

Anterolateral Thigh (ALT) Free Flap

Vascular Anatomy

Based on perforators from the descending branch of the lateral circumflex femoral artery (LCFA). The LCFA arises from the profunda femoris (most commonly) or directly from the common femoral artery. Perforators to the skin are found along a line from the ASIS to the superolateral patella (midpoint is the typical perforator location). Perforator types: Musculocutaneous (most common, ~80%): perforators pass through the vastus lateralis muscle. Septocutaneous (~20%): perforators travel in the intermuscular septum between the rectus femoris and vastus lateralis. Pedicle length: 8-16 cm (long pedicle is a major advantage). Artery diameter: 2-3 mm; vein: 2-4 mm (comfortable size for anastomosis).

Flap Composition Options

Fasciocutaneous: skin and fascia (most common). Adipofascial: de-epithelialized for buried reconstruction. Myocutaneous: includes a portion of vastus lateralis for bulk or muscle coverage. Chimeric: skin paddle + separate muscle component on independent perforators from the same source vessel. Sensate flap: lateral femoral cutaneous nerve can be included.

Dimensions

Skin paddle: up to 25 x 35 cm; typically 8-15 cm wide. Primary closure possible if width < 8 cm; split-thickness skin graft for wider paddles. Can be thinned (suprafascial or primary thinning) for thin, pliable reconstruction.

Flap Harvest Technique

1. Mark the line from ASIS to superolateral patella; midpoint is the reference for perforator location
2. Handheld Doppler or preoperative CTA to identify perforators
3. Incise medially first (exploratory incision) through skin, subcutaneous tissue, and fascia lata
4. Identify the intermuscular septum between rectus femoris and vastus lateralis
5. Identify perforators -- choose the dominant perforator(s)
6. For musculocutaneous perforators: dissect through the vastus lateralis muscle along the perforator back to the descending branch of the LCFA (tedious but critical step)
7. For septocutaneous perforators: dissection is easier (follow the septum to the source vessel)
8. Ligate side branches to the vastus lateralis as needed for pedicle length 9. Complete the skin paddle incision, elevate the flap on the pedicle

Applications

Head and neck: oral cavity, oropharynx, hypopharynx, scalp, midface reconstruction. Extremity: soft tissue coverage of tibia, foot, upper extremity. Trunk: chest wall, perineal reconstruction. Folded flap: can be folded to provide lining and coverage (oral reconstruction).

Donor Site

Primary closure if < 8 cm width; STSG for wider defects. Low morbidity: minimal functional deficit (vastus lateralis partially denervated in musculocutaneous perforator harvest). Hidden location (thigh); acceptable cosmesis.

<image>Surgical anatomy illustration of the anterolateral thigh flap. The main view shows the lateral thigh with the skin paddle marked around the ASIS-to-patella midpoint reference line. The deep dissection reveals the descending branch of the lateral circumflex femoral artery running between the rectus femoris and vastus lateralis muscles. Both musculocutaneous perforators (passing through the vastus lateralis) and septocutaneous perforators (running in the intermuscular septum) are shown with their paths to the skin paddle. The motor nerve to the vastus lateralis is identified and preserved. Inset shows the vascular pedicle origin from the profunda femoris artery.</image>

Radial Forearm Free Flap (RFFF)

Vascular Anatomy

Based on the radial artery and its venae comitantes. Radial artery runs between the brachioradialis and flexor carpi radialis. Perforators from the radial artery supply the overlying skin through fascial septae. Cephalic vein can be included as an additional (or primary) venous outflow. Pedicle length: 15-20 cm (longest of any free flap). Artery diameter: 2.5-3.5 mm; vein: 2-4 mm.

Flap Composition

Fasciocutaneous: thin, pliable skin (most common configuration). Osteocutaneous: includes a segment of the radius (up to 40% of circumference for mandible reconstruction -- rarely used now due to fracture risk). Adipofascial: de-epithelialized; useful for contour correction. Sensate flap: lateral and medial antebrachial cutaneous nerves can be included. Palmaris longus tendon: can be included for dynamic reconstruction.

Preoperative Assessment

Allen test (mandatory): confirm ulnar artery adequacy to perfuse the hand after radial artery harvest. Modified Allen test: compress both arteries, have patient pump fist, release the ulnar artery -- hand should pink up within 5-7 seconds. If equivocal: Doppler assessment or pulse oximetry on the thumb during radial artery occlusion. Contraindication: inadequate ulnar artery perfusion (abnormal Allen test).

Dimensions

Skin paddle: up to 15 x 30 cm (can harvest most of the volar forearm). Flap is naturally thin (3-5 mm in non-obese patients). Ideal when thin, pliable tissue is needed.

Flap Harvest Technique

1. Confirm Allen test; mark the skin paddle over the volar forearm
2. Tourniquet is optional (facilitates identification but can cause spasm)
3. Incise the ulnar border of the flap first; identify and preserve the ulnar artery
4. Elevate from ulnar to radial, deep to the antebrachial fascia
5. Identify and ligate perforators from the ulnar artery to the flexor muscles
6. Dissect the radial artery and venae comitantes from the floor (pronator quadratus, FPL, FDS tendons)
7. Include the cephalic vein if needed
8. Include the lateral antebrachial cutaneous nerve for a sensate flap 9. Divide the pedicle proximally or distally depending on reach requirements

Applications

Head and neck: oral cavity (tongue, floor of mouth), pharynx, lips. Gold standard for intraoral soft tissue reconstruction (thin, pliable, long pedicle). Sensate flap for tongue reconstruction (improves speech and swallowing). Radial forearm osteocutaneous flap: small mandibular defects (lateral segment); less commonly used since fibula flap became the standard.

Donor Site

Major disadvantage: conspicuous donor site on the volar forearm (cosmetically poor). STSG required for closure (primary closure rarely possible). Exposed tendons (flexor tendons visible under the graft) -- cosmetically and functionally concerning. Suprafascial dissection (leaving the paratenon intact) improves graft take and appearance.

Sacrifice of the radial artery -- hand perfusion depends entirely on the ulnar artery and palmar arch. Possible complications: graft failure (especially over paratenon-stripped tendons), wrist stiffness, decreased grip strength (transient).

<image>Surgical anatomy illustration of the radial forearm free flap harvest. The main view shows the volar forearm with the skin paddle outlined, the radial artery running between the brachioradialis and FCR with its fascioseptocutaneous perforators supplying the overlying skin, the cephalic vein on the radial aspect, and the lateral antebrachial cutaneous nerve. The deep dissection shows the relationship of the radial artery to the flexor tendons (FPL, FDS) and pronator quadratus. An inset demonstrates the Allen test technique with compression of the radial artery and assessment of hand perfusion via the ulnar artery.</image>

Comparison: ALT vs. Radial Forearm

Clinical Pearls

The ALT flap has largely replaced the radial forearm flap as the first-choice workhorse for head and neck reconstruction due to superior donor site morbidity and comparable versatility. When a thin, pliable flap is needed (especially for intraoral reconstruction), the radial forearm remains the gold standard -- its thinness and long pedicle are unmatched. The Allen test is mandatory before radial forearm flap harvest -- a positive test (inadequate ulnar perfusion) is an absolute contraindication. ALT perforators are musculocutaneous in approximately 80% of cases -- dissection through the vastus lateralis is technically demanding and is the most time-consuming step of the harvest.

If no suitable perforators are found during ALT harvest, convert to: anteromedial thigh (AMT) flap, tensor fasciae latae flap, or rectus femoris flap from the same incision. Preoperative CTA is increasingly used to map perforator anatomy for ALT flaps, reducing intraoperative surprises and guiding skin paddle design. The ALT can be harvested as a chimeric flap with a separate muscle component (vastus lateralis) for complex three-dimensional defects requiring both coverage and dead space obliteration. The radial forearm donor site is the main drawback of this flap -- counsel patients about the visible scar and STSG appearance on the forearm; suprafascial dissection improves outcomes. ---.

References

• Song YG, Chen GZ, Song YL. The free thigh flap: a new free flap concept based on the septocutaneous artery. Br J Plast Surg. 1984;37(2):149-159.
• Wei FC, Jain V, Celik N, et al. Have we found an ideal soft-tissue flap? An experience with 672 anterolateral thigh flaps. Plast Reconstr Surg. 2002;109(7):2219-2226.
• Soutar DS, Scheker LR, Tanner NS, McGregor IA. The radial forearm flap: a versatile method for intra-oral reconstruction. Br J Plast Surg. 1983;36(1):1-8.
• Kimata Y, Uchiyama K, Ebihara S, et al. Anterolateral thigh flap donor-site complications and morbidity. Plast Reconstr Surg. 2000;106(3):584-589.
• Pho RWH, Levack B, Satku K, et al. Free flap transfer with radial forearm flap. Plast Reconstr Surg. 1988;81(1):21-28.
• Saint-Cyr M, Wong C, Schaverien M, et al. The perforasome theory: vascular anatomy and clinical implications. Plast Reconstr Surg. 2009;124(5):1529-1544.

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