Near-Infrared Laser-Assisted Indocyanine Green Imaging for Optimizing the Design of the Anterolateral Thigh Flap

METHODS

Fifteen patients with head and neck cancer were reconstructed with ALT flaps using laser-assisted ICG perforator perfusion zone mapping. Patient demographics, defect characteristics, reconstructive techniques, and clinical outcomes were assessed. We retrospectively reviewed prospectively entered data from the computerized database in the Department of Plastic Surgery at the MD Anderson Cancer Center for all patients included in the study. This study was approved by the Institutional review board at The University of Texas MD Anderson Cancer Center.

For each patient, a line was drawn from the anterior superior iliac spine to the lateral border of the patella and the laser was centered over the midpoint as previously described.⁵ An X-Y system of one-centimeter hatch marks, centered on the midpoint, was drawn onto the leg using a marking pen (Fig 1). Indocyanine green (12.5 mg) was injected intravenously and live fluorescence patterns were recorded using near-infrared laser angiography.

Figure 1. Donor leg displaying ABC perforator system with onlay XY grid.

Optimal perforator perfusion zones were chosen using real-time imaging and SPY-Q analysis software. A template of the residual oncologic defect was made using an Esmarch dressing (Fig 2). Using the template, the skin paddle was centered over optimal perforator perfusion zones (Fig 3). All flaps were elevated in standard fashion (Fig 4). Handheld Doppler was not used to identify perforator signals preoperatively in aiding with the design of the flap.

Figure 2. Donor leg displaying ABC perforator system with recipient site specifications drawn onto a template.

Figure 3. Intraoperative SPY Q analysis photo displaying zones of maximal perfusion corresponding points drawn on the XY grid system.

Figure 4. Elevation of the ALT flap over the zones of maximal perfusion. ALT indicates anterolateral thigh.

RESULTS

Fifteen patients underwent free ALT tissue transfers for head and neck cancer reconstruction. (Figs 5 and 6) Intraoperative imaging using ICG assisted in placement of the ALT skin paddle over 1 or 2 optimal perforators for each flap were recorded and analyzed (Video 1). In this series, there were no complications related to the administration of ICG fluorescent dye. There was one flap loss secondary to venous thrombosis requiring debridement. All ALT donor sites were able to be closed primarily, with no other reconstructive measures such as skin grafting required.

Figure 5. Inset of the ALT flap over large head and neck defect.

Figure 6. Resultant photograph showing reconstruction of the tongue and check with free ALT flap. ALT indicates anterolateral thigh.

DISCUSSION

The ALT flap is both reliable and versatile, with relatively low donor-site morbidity.⁶ Because of perforator variability, capture of the axially based perforasome can be difficult if the skin paddle is not centered correctly.⁷ In addition, anatomic variations and perforator variability can lead to lengthy and arduous dissections, which may compromise flap perfusion and predispose to flap loss.⁸ Laser-assisted angiography can aid in optimizing flap design while decreasing donor site morbidity by incorporating maximal flap perfusion patterns in a real-time setting.

Other accepted preoperative design methodologies have their own limitations. A handheld unidirectional Doppler probe, while highly sensitive, frequently locates small perforators that may be insufficient to support a flap.⁹ In addition, sensitivity may also vary significantly with differential skin thickness.^5,10 Computed tomographic angiography provides information as to the largest perforator to a specific area, but it does not provide dynamic information as to the actual perforator perfusion zones. In addition, there is a radiation and contrast load when using this assessment tool.

Laser-assisted angiography with SPY-Q analysis gives live localization of the flap's dominant perforator perfusion zones while quantifying the relative tissue perfusion for immediate skin paddle design. Using the SPY-Q analysis program, we were able to identify the dominant perforator perfusion zone on which to center our skin paddles. Our grid system further augments the ease of pinpointing these perfusion zones because one can objectively find this zone on the analysis image and correlate it directly within the grid located on the patient's donor thigh.

Dominant perforators may not travel directly to the dermis as shown in experimental studies of primary ALT flap thinning.¹¹ Although dermal perfusion has been shown to correlate with actual perforators in a swine model, they may not directly map the perforators, which may be more noticeable in larger thighs where perforators may take indirect paths before reaching the subdermal plexus.¹² Our method does not identify if a multipaddle ALT can be raised because the perforators are not directly visualized; however, this can be utilized after flap elevation to assess viability of multiple paddles prior to separation.

Our intraoperative angiographic analysis not only optimizes the planning and dissection of the ALT flap but also can provide valuable information about the viability of a prospective flap. Thus, if the perforators are not visible on one thigh, the operation can be aborted and the contralateral thigh may be used. This could potentially avoid unnecessary flap dissection. In the rare instance that neither flap is available for coverage, the operation can be aborted and other reconstructive options can be pursued.

The ALT flap can be raised successfully without using laser-assisted angiography but this can be at the expense of potentially harvesting a much larger skin paddle than required. By making the anterior incision more medially, the surgeon will increase the odds of capturing the septal musculocutaneous perforators. However, this will increase the likelihood of a difficult closure. We believe ICG analysis may be especially useful for less experienced surgeons in their flap design. We contend that the analysis provides valuable data about perforator perfusion zones and should be considered when designing the skin paddle. A larger experience using this technique will determine whether flap viability is actually improved by this method.

CONCLUSIONS

Laser-assisted ICG angiography using SPY-Q analysis software provides robust, intraoperative, objective data to optimize ALT skin paddle design while potentially minimizing patient morbidity. Our grid system augments the ability to pinpoint the best zone of perforator perfusion. This imaging system has the potential to revolutionize and simplify the intraoperative design of perforator flaps.