How to Enhance the Accuracy of the Allen’s Test with Indocyanine Green Fluorescence Video-Angiography

Free flaps are routinely used in head and neck surgery for reconstruction after major ablative procedures. Among these, radial forearm free flap (RFFF) still represents a workhorse. Regarding its harvesting, donor site complications are described, with acute hand ischemia as the most feared one. To evaluate residual hand perfusion through the ulnar axis, several methods are commonly used in clinical practice, such as the modified Allen’s test (MAT) and Doppler ultrasound. Nevertheless, contradictory results are not uncommon. Indocyanine green (ICG) fluorescence video-angiography (ICG-VA) is a technique recently introduced in flap surgery to evaluate tissue perfusion, which may be employed during RFFF harvesting to enhance the accuracy of the traditional tests.

To assess the dual blood supply in the donor site prior to harvesting a RFFF, we performed MAT, Doppler ultrasound, and ICG-VA in a patient suffering from oropharyngeal cancer who underwent major ablative and reconstructive surgery. The technique is described in the Video.

Clinical MAT was judged as “positive,” highlighting an adequate dual blood supply to the hand, and the upper limb Doppler ultrasound showed a normal blood flow. Similarly, also ICG-VA pointed out a good hand perfusion pattern with a thenar-to-hypothenar ICG ratio of over 25%. Thus, we proceeded with RFFF harvesting without evidence of ischemic complications at the donor site in the postoperative course.

ICG-VA represents a safe and useful procedure to reduce donor site morbidity during RFFF harvesting, enhancing the sensitivity of the clinical MAT, and potentially detecting its (rare) false positive results.