The Vital Role of Pre-operative Imaging in Supraclavicular Artery Island Flap Design for Head and Neck Reconstruction

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The Vital Role of Pre-operative Imaging in Supraclavicular Artery Island Flap Design for Head and Neck Reconstruction

The supraclavicular artery island (SAI) flap has emerged as a versatile option for reconstructing head and neck defects, particularly in patients with limited donor-site availability or contraindications to free flaps. Despite its advantages, the flap’s reliability remains debated due to complications such as distal necrosis. This article synthesizes critical insights from a recent scholarly exchange between two research groups, emphasizing the indispensable role of pre-operative imaging in optimizing SAI flap design, reducing complications, and enhancing surgical outcomes.

Anatomical Basis and Clinical Applications of the SAI Flap

The SAI flap is a fasciocutaneous pedicled flap based on the supraclavicular artery (SCA), a branch of the transverse cervical artery (TCA). The SCA typically originates at the junction of the middle and lateral thirds of the clavicle, coursing superficially toward the deltoid region. Its vascular territory covers the supraclavicular fossa and lateral shoulder, allowing harvest of a skin paddle up to 24 cm in length. The flap’s popularity stems from its thin, pliable tissue, proximity to head and neck defects, and preservation of major neck structures.

Clinically, the SAI flap has been applied to reconstruct oral cavity, pharyngeal, cutaneous, and skull base defects. A review of 528 SAI flaps revealed a 24.6% minor complication rate, with distal flap necrosis being the most common issue. These complications highlight the need for meticulous pre-operative planning to assess vascular anatomy and ensure adequate perfusion.

Challenges in SAI Flap Reliability: Distal Necrosis and Anatomical Variability

1. Anatomical Variability of the Supraclavicular Artery
The SCA exhibits significant anatomical variability. Studies report its diameter at the origin ranges from 0.5 mm to 1.9 mm. Smaller-caliber arteries (<1 mm) correlate with diminished perfusion, particularly in the distal flap. For example, cadaveric CTA studies demonstrated that SCA diameters of 0.7 mm perfused only 50% of the skin paddle, leaving the distal region vulnerable to ischemia.

2. Excessive Flap Length
While the SAI flap can extend beyond the SCA’s anatomical territory via interperforator and subdermal plexus flow, clinical evidence suggests a safe maximum length of 22–24 cm. Overextension risks necrosis, as perfusion pressure diminishes distally. Chan et al. proposed that flap length should align with the SCA’s total anatomical length (48–92 mm), though this remains unvalidated in vivo.

3. Inadequate Pre-operative Assessment
Failure to map the SCA’s angiosome pre-operatively often leads to poor flap design. Traditional methods like handheld Doppler (HHD) are error-prone, with false positives/negatives in 15–20% of cases. HHD also fails to quantify perfusion capacity or identify branching patterns, critical for avoiding distal ischemia.

Pre-operative Imaging Modalities for SAI Flap Design

1. Handheld Doppler (HHD)
HHD is a low-cost, non-invasive tool for detecting arterial signals. While useful for initial mapping, it cannot delineate the full angiosome or assess vessel caliber. Granzow et al. noted that viable flap tissue may extend 5 cm beyond the last audible Doppler signal, suggesting HHD underestimates perfusion potential.

2. Computed Tomographic Angiography (CTA)
CTA provides high-resolution images of the SCA’s origin, course, and branching. It is particularly valuable for patients with prior neck surgery or radiation, where vessel integrity is suspect. However, CTA cannot dynamically assess perfusion and involves radiation exposure, limiting routine use.

3. Indocyanine Green (ICG) Fluorescence Angiography
ICG angiography offers real-time visualization of microcirculation, aiding intra-operative decisions. Systems like the SPY-Elite can identify hypoperfused regions, enabling immediate flap trimming. While promising, its role in SAI flap design requires further validation.

4. Color Doppler Ultrasonography (CDU)
CDU combines anatomical and hemodynamic assessment, measuring vessel diameter, peak systolic velocity (PSV), and flow direction. In a clinical example, CDU identified an SCA with a 1.4 mm diameter and PSV of 15 cm/s, enabling safe harvest of a 21 cm flap. The distal margin was set 3 cm beyond the last detectable Doppler signal, avoiding necrosis. CDU’s limitations include operator dependence and time-intensive scanning.

Technical Refinements: The “Point-Line Anterograde Dissection” Approach

Zhou et al. introduced the “point-line anterograde dissection” technique to enhance reliability:

  1. Identification of the “Point”: The SCA origin is traced proximally to the TCA under direct vision, establishing the “turning point” for flap rotation. Skeletonizing the TCA’s cervical segment improves mobility and reduces lymphatic complications.
  2. Anterograde Dissection: The SCA is dissected 1–2 cm distally, and an “extension line” is drawn along its axis to guide flap design. This ensures the flap remains within the SCA’s angiosome.
  3. Flap Tailoring: The distal margin is limited to 3 cm beyond the last visualized SCA branch, balancing defect coverage and perfusion.

This approach contrasts with methods using the supraclavicular fossa as the pivot point, which may require longer pedicles and increase ischemia risk. By anchoring the flap to the TCA’s origin, Zhou et al. reported no distal necrosis in their case series.

Clinical Case Demonstrations

Case 1 (Wu et al.):
A patient with mandibular osteoradionecrosis underwent SAI flap reconstruction after CDU mapping. The SCA (1.4 mm diameter, 10.5 cm post-clavicular length) supported a 7 × 21 cm flap without necrosis. Post-operative follow-up confirmed viable tissue at 6 months.

Case 2 (Zhou et al.):
A through-and-through hypopharyngeal defect was repaired using bilateral SAI flaps. The “point-line” method ensured both flaps (dimensions not specified) survived fully, with no complications at 10 days or 6 months.

Consensus and Future Directions

Both groups agree that pre-operative imaging is critical for SAI flap success. Key recommendations include:

  • Routine CDU or CTA: To assess SCA diameter, length, and branching.
  • Angiosome-Driven Design: Limit flap length to 22–24 cm, with margins ≤3 cm beyond imaging-confirmed perfusion.
  • Intra-operative ICG: To validate perfusion before insetting.

Future research should standardize imaging protocols and correlate SCA anatomy with flap outcomes. Innovations in 3D angiography and dynamic perfusion modeling could further refine flap design.

doi.org/10.1097/CM9.0000000000001358

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