Computed tomographic angiography versus handheld Doppler in perforator detection for anterolateral thigh flaps: a prospective randomized comparative study

Article information

Arch Hand Microsurg. 2025;30(2):127-135

Publication date (electronic) : 2025 May 30

doi : https://doi.org/10.12790/ahm.25.0001

Wael Mohamed Ayad, Tarek Zayed, Mohamed Osama Ouf, Mahmoud Ibrahim Elshamy, Mahmoud Abdulnabi Abdullatif

Department of Plastic and Reconstructive Surgery, Faculty of Medicine, Al-Azhar University, Cairo, Egypt

Corresponding author: Mahmoud Abdulnabi Abdullatif Department of Plastic and Reconstructive Surgery, Faculty of Medicine, Al-Azhar University, 1 El Mokhayam El Daem St., Nasr City, Cairo 11884, Egypt Tel: +20-2-24012931 E-mail: Mah.abdullatif87@gmail.com

Received 2025 January 5; Revised 2025 February 23; Accepted 2025 March 19.

Abstract

Introduction

The anterolateral thigh (ALT) flap was first described by Song et al. [1] in 1984 as a flap based on septocutaneous vessels running in between the rectus femoris and vastus lateralis muscles. Soon it gained popularity due to many characteristics such as quick harvesting with minimal donor site morbidity, and being harvested as a myocutaneous, fasciocutaneous, suprafascial, and chimeric flap. However, one of the biggest drawbacks of this flap is its anatomic variation making an unpredictable intraoperative challenge [2]. In 1988, Xu et al. [3] described a common location of perforators within a circle with a radius of 3 cm, the center of which is the midpoint of a line linking the anterior superior iliac spine (ASIS) and the superolateral border of the patella; however, few described its inconsistencies.

Due to a relatively increased flap failure and partial necrosis, imaging and proper preoperative mapping have evolved. Handheld Doppler (HHD) is a dependable, portable, easy-to-use and interpret, intraoperative device for perforator detection but has poor accuracy. Its principle is used through the Doppler effect, which involves the change in frequency of sound waves as they bounce off moving objects—in this case, red blood cells. The device transmits sound waves and measures the frequency shift in the returning waves, which correlates to the velocity of blood flow. However, its main drawbacks are operator-dependent, limited resolution, and insufficiently detailed anatomy. On the other hand, computed tomographic angiography (CTA) is a noninvasive, operator-independent superior to HHD in detecting perforators. While several studies have compared these modalities globally, their utility in the Egyptian population, characterized by potential anatomical and demographic variations, remains unexplored. This study aims to fill that gap by evaluating the sensitivity, specificity, and accuracy of CTA versus HHD in preoperative perforator detection for ALT flap surgery.

Methods

1. Study design and patient selection

This study was conducted on 20 patients requiring an ALT free flap from April 2023 to November 2024. Patients with severe comorbidity (e.g., peripheral vascular disease, diabetes mellitus) that affects the vascular wall, severe chronic illness, allergy to contrast, severe limb infections, and previous scars have been excluded. Patients were randomized into two groups. Group A (10 patients) received CTA while group B (10 patients) did not. An HHD (8 MHz; Huntleigh Healthcare, Cardiff, UK) was used in the preoperative setting on all patients by a single surgeon blinded to the results of preoperative mapping with CTA.

In the supine position, a line was drawn connecting the ASIS, and the superolateral patellar border representing the septum between the vastus lateralis and the rectus muscle. Three different zones are assessed as the location of detected perforators either by CTA or HHD. First is the area covered by a 5-cm radius from the midpoint of the ASIS–patella (AP) line (zone A). The other two zones are 5 cm proximal and distal to this (zones B and C), respectively. The same assessor with the ‘x’ symbol marked significant signals received with HHD.

Computed tomography (CT) with angiographic technique was performed using GE Optima 128 slices CT scanners (GE Healthcare, Milwaukee, WI, USA), with a slice thickness of 1.5 mm. During the scanning, the patients were positioned identically to their actual placement on the operating table, as body position may significantly influence the perfusion of perforators when CTA is performed. Perforators preoperatively mapped with CTA are marked with a ‘O’ symbol from the AP line. Then, both groups were compared with intraoperative findings (Fig. 1).

Fig. 1.

Anterolateral thigh free flap marking. “X” denotes the Doppler signal, and “•” denotes the preoperative perforator localization using computed tomographic angiography.

4. Clinical cases

Three representative clinical cases were included to demonstrate the application of the ALT flap technique: Case 1: a 14-year-old child with a post-burn contracted neck who underwent an ALT free flap procedure for neck release (Fig. 2); Case 2: a 19-year-old adult with a similar post-burn neck contracture, also treated with an ALT free flap (Fig. 3); Case 3: a 37-year-old patient with a soft tissue defect in the left foot following trauma, which was reconstructed using a rectus femoris muscle flap (Fig. 4).

Fig. 2.

Case 1. A 14-year-old child with a post-burn contracted neck. (A) Computed tomographic angiography showing an axial slice, with the perforator location marked using an arrow. (B) Visualization of three perforators arising from the descending branch of the lateral circumflex femoral artery with a blue background. (C) Preoperative view showing the contracted neck, highlighting the deformity due to the post-burn contracture. (D) Intraoperative view after anastomosis (surgical connection) and inset of the tissue, showing the result of the procedure to release the contracture.

Fig. 3.

Case 2. A 19-year-old adult with a post-burn contracted neck. (A) Computed tomographic angiography showing an axial slice, with the perforator location marked using an arrow. (B) A perforator arising from the descending branch of the lateral circumflex femoral artery is demonstrated. (C) A preoperative image shows the degree of neck contracture, showing limited mobility or scarring, which is often a primary concern for patients with burn injuries. (D) An early postoperative view shows the outcome following reconstructive surgery or release of the burn contracture.

Fig. 4.

Case 3. A 37-year-old patient who experienced an injury with a soft tissue defect in the left foot. (A) An X-ray reveals a fracture of the calcaneus bone with fixation. (B) A soft tissue defect with a necrotic bed. (C) The soft tissue defect was covered using a rectus femoris muscle flap. This flap was chosen after preoperative computed tomographic angiography mapping, which revealed an absence of anterolateral thigh perforators. (D) Postoperative view showing good coverage and contour.

Results

A total of 20 patients over 1 year who underwent free ALT flap coverage at Al-Azhar University Hospital were allocated randomly into two groups.

1. Patient demographics

The mean age of patients in group A was 30.2±15.33 years, and that in group B was 47.4±16.23 years (p=0.025). The mean body mass indexes (BMIs, kg/m²) were 28.1±2.26 in group A and 27.71±2.73 in group B (p=0.752). Flap thickness (mm) in group A was 6.2±1.1, while in group B, it was 5.0±1.3 (p=0.03) (Table 1).

Table 1.

Demographic characteristics of the study groups

3. Perforator characteristics

Source

The source vessel was DB-LCFA in 13 patients (five in group A and eight in group B), the transverse branch of the lateral circumflex femoral artery in three patients (one in group A and two in group B), and the oblique branch of the lateral circumflex femoral artery in two patients (group A). There were absent perforators in two patients (group A) reconstructed with rectus femoris muscle flap (Table 2).

Table 2.

Perforator sources in the study groups

Number

In this study, a perforator over 1 mm was considered to be sizable from the three zones mentioned. CTA detected 14 from 17 perforators in group A while HHD detected 12 of 18 in group B.

Concordance of computed tomographic angiography versus Doppler for perforator localization

A discrepancy of more than 1 cm between preoperative localization and intraoperative findings generally represents discordance. CTA had 100% concordance while HHD had 40% concordance.

Operative time

The mean average of operative time was 4.75±0.5 hours for group A and 5.6±0.8 hours for group B (p=0.02) (Table 3).

Table 3.

Operative time in the study groups

Sensitivity, specificity, and accuracy of Doppler versus multidetector computed tomographic angiography in localization

CTA’s sensitivity and specificity were 86.0% and 98.0%, respectively, compared to HHD’s 81.0% and 86.5%. CTA’s accuracy in perforator identification was 92.0%, compared to HHD’s 83.5% (Tables 4, 5).

Table 4.

Segmental distribution of perforators with sensitivity, specificity, and accuracy of CTA in group A

Table 5.

Segmental distribution of perforators with sensitivity, specificity, and accuracy of HHD in group B

Discussion

Due to reported failures and partial necrosis of the ALT flap, Imaging has evolved for better detection of perforator locations and courses [4]. Numerous imaging modalities exist including color Doppler, digital subtraction angiography, and magnetic resonance imaging. However, CTA is considered the most consistent [5].

In recent years, microsurgeons have increasingly incorporated ultrasound into the preoperative evaluation of the ALT flap. Ultrasound, particularly Doppler ultrasound, plays a critical role in identifying the vascular anatomy and assessing the viability of the flap’s blood supply. By providing real-time imaging of the perforators and their flow characteristics, ultrasound offers valuable insights into the location and size of the perforating vessels. This helps in planning the flap’s harvest, potentially improving the precision of the procedure and reducing the risk of complications.

Additionally, ultrasound serves as a noninvasive, cost-effective tool for evaluating the soft tissue structures around the ALT flap, offering an advantage over other imaging modalities. Its ability to detect variations in blood flow can guide the surgeon in selecting the most suitable perforators for the flap, thus enhancing the chances of a successful reconstruction. As such, ultrasound has proven to be a reliable and efficient addition to the preoperative assessment, providing surgeons with essential information to optimize outcomes in ALT flap surgeries.

Our study demonstrates that CTA offers superior sensitivity, specificity, and accuracy compared to HHD in preoperative perforator mapping for ALT flap surgery. These findings align with previous studies highlight the benefits of CTA in detailed vascular visualization and improved surgical planning.

While simple and cost-effective, HHD is limited by operator dependency and a higher rate of false positives. In contrast, CTA provides three-dimensional imaging, enabling precise localization of perforators and reducing intraoperative exploration time. This advantage is particularly significant in anatomically variable regions, where accurate mapping can mitigate surgical risks.

The clinical implications of these findings are substantial. Enhanced preoperative planning with CTA can lead to more efficient surgeries, reduced operative time, and potentially lower complication rates. Although the cost and need for contrast administration may limit CTA’s routine use, its benefits in complex cases or in settings with anatomical variability are undeniable.

In this study, we provide a detailed comparison of perforator numbers, sources, and diagnostic techniques (CTA versus HHD) in locating perforators for ALT flap surgery.

Perforator number and type: The average number of perforators in the three zones per limb was 20% subcutaneous (SC) and 70% musculocutaneous (MC). 10% of patients had no detectable perforators. The distribution is similar to the study by Kimata et al. [6], which found 81.9% MC perforators and 18.9% SC perforators, with 5% having no perforators. The rectus femoris flap can serve as a reliable alternative when ALT perforators are absent or unsuitable for use. It is a good option for muscle-based soft tissue reconstruction, particularly in the thigh, groin, or lower abdominal regions. Although functional loss may occur at the donor site, the flap offers adequate bulk, reliable perfusion, and versatility, making it an important option for surgeons to consider in reconstructive cases where the ALT flap cannot be used.

Perforator source: The study found no significant difference between CTA and intraoperative findings in determining the source of perforators, validating the efficacy of CTA. In two patients, a perforator arose from the oblique branch of the DB-LCFA, which is consistent with Wong et al.’s [2] findings on the anatomical origin of the oblique branch.

Sensitivity, specificity, and accuracy of Doppler vs. CTA: Yu and Youssef [7] and Jadhav et al. [8] indicated that Doppler was overly sensitive, poorly specific, and inaccurate in perforator localization. In this study, Doppler had a sensitivity of 81% and a specificity of 86.5%.

CTA: The current study showed that CTA had a sensitivity of 86.0% and specificity of 98.0%, outperforming Doppler in the accurate localization of perforators. This aligns with findings from Lin et al. [9]. and Jadhav et al. [8], who reported sensitivities of 74%–85% and specificities of 90%–97% for CTA. Previous studies such as Cheng et al. [10]. found that HHD had a sensitivity of 89.7% and specificity of 18.2%, with an accuracy of 80.5%. The study concluded that while HHD is a simple and easy method, it is not always accurate for perforator localization. The diagnostic odds ratio for HHD in detecting ALT perforators was 1.942, indicating its limitations in precise mapping. Similarly, Moore et al. [11]. conducted a systematic review analyzing 23 studies and found that CTA sensitivity was 90.4%, with accuracy in perforator course identification of 96.9%. Findings from Kim et al. [12] further support the reliability of CTA in preoperative perforator imaging. Their study found that CTA could predict perforator localization during ALT flap elevation, with perforator depth measured by CTA showing a significant correlation with Doppler-identified locations. Almost all perforators (20 out of 21 cases) were identified within a radius equivalent to the CTA-assessed perforator depth, demonstrating that a combination of CTA and Doppler can effectively and safely localize perforators.

CTA is generally considered the gold standard for evaluating the vascular supply of ALT flaps, offering higher sensitivity, specificity, and accuracy compared to Doppler ultrasound. Doppler ultrasound, while highly useful and accessible, may have slightly lower sensitivity and specificity and depend more on the operator’s skill. However, it remains a highly valuable tool for quick, noninvasive assessments, especially in less complex cases. In clinical practice, Doppler ultrasound is often used as a first-line tool due to its noninvasive nature, but CTA is employed for more detailed and complex evaluations when precise vascular mapping is required.

BMI and flap thickness: We have noticed that flap thickness affects Doppler’s accuracy. The primary challenge when using HHD on thick flaps is the limitation in detecting blood flow through dense tissue. The thicker the flap, the more difficult it may be to obtain a clear signal, as the Doppler sound waves may not penetrate deeply enough into the tissue. Doppler devices typically detect blood flow by emitting sound waves, which bounce off moving red blood cells and return as a signal. In thick tissues, the signal may be attenuated or distorted, leading to inaccurate readings or an inability to detect the flow properly.

Operative time: CTA significantly reduced the mean harvesting time (p=0.049), which is consistent with findings from Jadhav et al. [8] (p=0.046), suggesting that preoperative CTA planning helps streamline surgical procedures. Reducing operative time can be attributed to reduced actual dissection, minimized continuous exploration, and limited need for managing unexpected issues (e.g., bleeding, incorrect vessel identification), which contributes to a shorter operative time and potentially safer surgical course.

Complications: There were no significant differences in flap survival or donor site complications between patients who underwent CTA and those who did not, indicating that CTA did not negatively impact postoperative outcomes.

Conclusion

CTA demonstrates superior sensitivity, specificity, and accuracy compared to HHD in preoperative perforator detection for ALT flap surgery. The enhanced imaging capabilities of CTA facilitate precise perforator localization, reducing intraoperative uncertainty and the risk of complications. These benefits can lead to improved surgical outcomes, including more efficient flap harvest, reduced operative times, and potentially higher flap survival rates. Given these advantages, CTA could be considered a valuable standard tool in preoperative planning for ALT flap surgeries, especially in cases where anatomical variation poses a significant challenge. However, the number of samples in this study is small, and further research with larger sample sizes is recommended to confirm these findings and assess the cost-effectiveness of routine CTA use.

Article information Continued