The anterolateral thigh flap is widely used in reconstructive surgery because it can provide a substantial volume of skin and soft tissue with relatively low donor-site morbidity. However, the location and course of the perforating vessels supplying the flap can vary considerably between patients. Accurate preoperative mapping can help surgeons select suitable perforators, position the flap and reduce uncertainty during flap elevation. A new study compared indocyanine green angiography (ICGA) with colour Doppler ultrasonography (CDU) for locating perforators before anterolateral thigh-flap reconstruction.
Comparing ICGA with Colour Doppler
The investigators retrospectively analysed 56 reconstructions undertaken between January and July 2024. Perforators identified using ICGA and CDU were compared with those found during surgery.
ICGA demonstrated better performance across all the principal diagnostic measures:
| Performance measure | ICGA | Colour Doppler |
| Sensitivity | 92.50% | 84.90% |
| Specificity | 82.00% | 80.00% |
| Positive predictive value | 93.90% | 84.70% |
| Negative predictive value | 90.20% | 79.20% |
| Overall accuracy | 92.20% | 82.30% |
These findings indicate that ICGA identified a greater proportion of the perforators confirmed during surgery and was more reliable in distinguishing areas with and without a perforator.
Although overall detection performance was better with ICGA, there was no significant difference between the two methods in the accuracy of the exact perforator location.
Flap Thickness Affected ICGA Accuracy
Flap thickness was identified as an independent predictor of ICGA accuracy, with performance declining when tissue thickness exceeded 2.35 cm.
This is clinically relevant because increasing tissue depth can reduce the strength of the near-infrared fluorescence signal detected at the surface. The 2.35 cm cut-off was derived from this single retrospective cohort and will require validation before it can be considered a general clinical threshold.
For colour Doppler, the timing of the examination relative to surgery was identified as a factor affecting accuracy.
Perforator Distribution May Guide Planning
The study also examined where perforators were most commonly located. Septocutaneous perforators were most frequent in the proximal zone, where they represented 61.2% of perforators. These vessels may be favourable because their course can make dissection more straightforward than that of perforators passing through muscle.
The study’s defined “hot zone” had the greatest concentration of perforators, providing potentially useful guidance on where preoperative mapping could be focused.
What Does This Mean for Clinical Practice?
The findings support a potential role for ICGA in helping surgeons to:
- identify clinically relevant perforators;
- distinguish perforator-positive and perforator-negative areas;
- support flap positioning and design;
- identify areas with a higher concentration of perforators; and
- reduce uncertainty before flap elevation.
ICGA and colour Doppler provide different types of information and may be complementary. ICGA offers visualisation of superficial perfusion and perforator emergence, while ultrasound can provide information about vessel depth, diameter, flow and anatomical course. Ultrasound may therefore remain particularly important in patients with thicker flaps. The study was retrospective, included 56 reconstructions and evaluated localisation performance rather than postoperative outcomes. Nevertheless, it provides further evidence that ICG angiography may support personalised planning in reconstructive surgery, while also identifying tissue thickness as an important consideration when interpreting fluorescence findings.
Reference
Localizing Perforators of the Anterolateral Thigh Flap: Color Doppler Ultrasonography Vs Indocyanine Green Angiography. https://pubmed.ncbi.nlm.nih.gov/42592532/
