Color Doppler Allen's Test before Harvesting a Radial Forearm Free Flap—To Do or Not to Do?

Dear Editor,

There are many reasons to write a letter to the editor. We hope that this one will help disseminate our concept regarding the fundamentals of reconstructive surgery and subject it to critical evaluation, thereby allowing for its refinement and further assessment in future studies.

The radial forearm flap (RFF) is widely regarded as the “workhorse” of reconstructive surgery, particularly in the head and neck region. Because harvesting of this flap involves the sacrifice of the radial artery (RA), Allen's test is routinely performed to reduce the risk of hand ischemia.

The hand is mainly perfused by two palmar arches: The superficial—formed predominantly by the ulnar artery, and the deep arch, primarily supplied by the RA. These two arches communicate, forming a dual loop that provides a redundant blood supply to the digits.

However, cadaveric studies have demonstrated numerous anatomical variations. If the superficial arch does not supply the most distal digits (i.e., the thumb and index finger) and lacks communication with the deep palmar arch, harvesting of the RFF may lead to ischemia, primarily affecting the first and second fingers. To date, only a few cases of acute ischemia have been described. Nevertheless, chronic hand ischemia remains a potentially underrecognized and underappreciated issue.[1]

According to current studies, whether Allen's test is sufficient to rule out ischemic complications following RA occlusion remains controversial. For instance, the RADAR study suggests that Allen's test alone may not provide a robust enough justification.[2] Moreover, a 2017 meta-analysis found an interobserver agreement rate of only 71.5%, which raises additional concerns regarding the test's overall reliability as well as coherence.[3]

For this reason, the authors have not performed the “classical” Allen's test for approximately 2 years. Instead, we used our simplified Ultrasonographic Color Doppler Allen's Test (UCDAT), finding it much more reliable. Our procedure for this assessment is as follows. First, we locate the first palmar metacarpal artery on color Doppler ultrasound—commonly known as the princeps pollicis artery. Then, we compress the RA for 10 seconds and monitor blood flow in the artery of interest ([Video 1]). If the flow disappears completely, we consider the test result negative. Any presence of blood flow is considered a positive result.

Video 1 Simplified Ultrasonographic Color Doppler Allen's Test.

To date, we have performed UCDAT on 46 patients. In three (7%), the result was negative, which prompted us to change the reconstructive plan and refrain from RFF harvest. In these patients, CT angiography of the upper extremity was performed ([Fig. 1]) to investigate potential vascular abnormalities ([Table 1]).

Fig. 1 CT angiography of the left upper extremity in a patient with a positive UCDAT. (A) Cross-sectional image at the level of the elbow joint. Yellow arrow, brachial artery. (B) Cross-sectional image at mid-forearm. Red arrow, radial artery; green arrow, anterior interosseous artery; absence of contrast enhancement in the ulnar artery (yellow circle). (C) Cross-sectional image of the distal forearm. Red arrow, radial artery; absence of contrast enhancement in the ulnar artery (yellow circle). UCDAT, Ultrasonographic Color Doppler Allen's Test.

Table 1 Brief summary of patients with positive Ultrasonographic Color Doppler Allen's Test

Patient no.	Sex/Age	Results of CT angiography	Allen's test	Alternative flap applied
1 ([Fig. 1])	Male/66	The ulnar artery did not exhibit contrast enhancement	Inconclusive	Lateral arm flap
2	Male/65	The ulnar artery was occluded, with extensive atherosclerotic plaques	Positive	Anterolateral thigh flap
3 ([Video 1])	Female/55	No abnormalities were detected in the vessels of the forearm and hand.	Inconclusive	Superficial circumflex iliac artery flap

The conventional Allen's test was performed following the color Doppler examination.

We are aware that using color Doppler ultrasound to assess the limb before harvesting an RFF is not a novel concept; there are several publications on this topic. Some address the issue rather vaguely, merely stating that the assessment was performed by a vascular surgeon, without providing any details regarding the procedure.[4] In other studies, the described method for performing the ultrasonographic Allen's test was highly complex and challenging to execute for surgeons unfamiliar with ultrasonography.[5] The technique we have presented is extremely simple and can be readily adopted by reconstructive surgeons. Given the growing popularity of ultrasound in plastic surgery, we believe that even physicians with limited ultrasonographic experience can perform UCDAT independently. This approach enables a more stringent patient selection process before harvesting the RFF.

To highlight the practical value: Would you, as a reconstructive microsurgeon, harvest an RFF if color Doppler ultrasound showed no flow in the princeps pollicis artery following RA compression (as demonstrated in [Video 1])?

Publikationsverlauf

Eingereicht: 13. April 2025

Angenommen: 01. Juni 2025

Accepted Manuscript online:
11. Juni 2025

Artikel online veröffentlicht:
22. Juli 2025

• References

• 1 Heller F, Wei W, Wei FC. Chronic arterial insufficiency of the hand with fingertip necrosis 1 year after harvesting a radial forearm free flap. Plast Reconstr Surg 2004; 114 (03) 728-731
• 2 Valgimigli M, Campo G, Penzo C, Tebaldi M, Biscaglia S, Ferrari R. RADAR Investigators. Transradial coronary catheterization and intervention across the whole spectrum of Allen test results. J Am Coll Cardiol 2014; 63 (18) 1833-1841
• 3 Romeu-Bordas Ó, Ballesteros-Peña S. Validez y fiabilidad del test modificado de Allen: una revisión sistemática y metanálisis. [Reliability and validity of the modified Allen test: a systematic review and metanalysis]. Emergencias (Madr) 2017; 29 (02) 126-135
• 4 Tousidonis M, Escobar JIS, Caicoya SO. et al. Preoperative Doppler ultrasonography Allen test for radial forearm free flap in oral cancer reconstruction: Implications in clinical practice. J Clin Med 2021; 10 (15) 3328
• 5 Habib J, Baetz L, Satiani B. Assessment of collateral circulation to the hand prior to radial artery harvest. Vasc Med 2012; 17 (05) 352-361