Since its introduction in 1984,1 the anterolateral thigh (ALT) flap has proven to be very popular and is a workhorse for flaps for reconstruction of soft tissue defects throughout the body.2–4 It is based on perforators from the descending branch of the lateral femoral circumflex artery, which allow it to be pliable and thin. Dissection of these perforators is generally the most challenging portion of raising the ALT flap due to their variability and location.
The most common method of finding the perforators has been the conventional handheld Doppler sonography using a pencil-type Doppler probe. The disadvantage has been that there is often poor concordance between the location of the perforator found clinically and the position found by the Doppler.5–7 This is because the perforator often takes an oblique course from the fascia to the skin. Also, these perforators may be musculocutaneous, not septocutaneous which can make for a more tedious dissection. The Doppler is unable to differentiate between these 2 courses to the skin. Other preoperative imaging has been used such as computed tomography angiography (CTA) or magnetic resonance angiography (MRA) but these tend to be very expensive or more invasive.6
We attempted to find a means of preoperative imaging which would be minimally invasive, inexpensive, but still show the perforator course in 3 dimensions for the greatest chance of success before raising the flap preoperatively. Color duplex sonography has been used in the past to aid preoperative mapping for perforator flap dissections.7–13 The purpose of the present study was to evaluate the value of preoperative color duplex sonography imaging for planning and performing free ALT flaps by assessing both potential thigh donor sites.
MATERIALS AND METHODS
Between July 2009 and December 2012, 19 patients had ALT flaps performed by a single surgeon (the senior author) and were retrospectively studied. The study was approved by our institutional review board. There were 17 men and 2 women with ethnicities including 16 white, 2 African American, and 1 Asian patient (Table 1). Color duplex sonography was performed before raising these flaps either in the preoperative area or in the operating room. This was performed by a vascular technologist in less than 20 minutes under the guidance of the surgeon.
The most common ALT flap markings were made by drawing a line from the anterior superior iliac spine to the superior lateral border of the patella. The flap was then marked by centering it on the midpoint between these points. Both the left and the right thighs were then examined over the marked out flap. All perforators on both thighs were then assessed for diameter, depth from the skin, flow, and whether the perforator had a septocutaneous or musculocutaneous course using duplex sonography. If the perforator was musculocutaneous, the length of the intramuscular course of each perforator was also assessed. In addition, the sensitivity of identified perforators between duplex sonography findings and intraoperative observations was also calculated.
All major perforators that were imaged by duplex sonography were identified during subsequent flap elevation (Fig. 1A,B). The sensitivity of the preoperative evaluation for perforator(s) in all ALT flaps by duplex sonography was 100%.
Each thigh was then evaluated to find the perforators that had the greatest diameter and flow, a septocutaneous or intramuscular course, or the most superficial intramuscular course if they had an intramuscular course. Also by looking at the course of the perforators, the easiest dissection with the least amount of intramuscular course or a complete septocutaneous course was then chosen.
All flaps were successfully elevated based on 1 or 2 identified perforators. There was no unexpected operative plan changes as the perforators that were determined to be the preoperative targets were all used for the vascular supply for the flap. All the flaps that were raised using this technique survived and were successfully transferred to the desired reconstructed area after microvascular anastomosis. None of the flaps were taken back to the operating room for arterial or venous insufficiency of the pedicle (Table 1).
A 60-year-old man presented with history of a motorcycle crash and a tibia and fibula fracture. He was treated by the orthopedic surgery service with an intramedullary nail. He subsequently developed infection of this hardware, had the hardware removed, but continued to have a medial wound of the distal third of the right lower extremity with exposed bone. He was evaluated by our service and determined to need an ALT free flap reconstruction. Both thighs were evaluated preoperatively using color duplex ultrasound. It was determined to use the left thigh based on larger perforators which were more superficial (Fig. 2A,B). The ALT flap measuring 20 × 8 cm was raised on 2 perforators and inset without complication. The patient went on to have a well-healed wound.
The most challenging and variable portion of raising an ALT free flap is the perforator dissection. Using a handheld Doppler preoperatively will help to assess the location of the perforators, but it has limitations. Specifically, a handheld Doppler can only evaluate perforators to a depth of 20 mm,5 which may be challenging in an obese patient with thick subcutaneous tissue. Also, handheld Doppler does not give any information regarding the diameter or flow of the perforator. It has been shown that there is only a 40% concordance rate between preoperative perforators and those found intraoperatively.8 Also, between 25% and 50% of ALT perforators are more than 1 cm away from Doppler signal.5 This is because of the oblique course of the subcutaneous portion of the perforator.
Color duplex ultrasonography has been shown to have a greater detail and accuracy when evaluating perforating vessels. In our study, we used this imaging modality on each thigh to evaluate which thigh would give us the greatest chance of success based on finding the largest perforators with the highest flow. Also, by choosing the side with an easier dissection based on whether the perforators were septocutaneous or musculocutaneous, would potentially decrease operative time. In this study, all the major perforators were found and the ALT flaps were based on these perforators. The surgeon was able to visualize the perforators along with the vascular technologist. Thus, the 3-dimensional course could be seen before raising the flap which is particularly helpful in perforators which run obliquely from the fascia to the skin paddle. By having a better understanding of the location of the perforators, in comparison to handheld Doppler, this allowed the surgeons to dissect closer to the preoperative marking without concern for injuring the vessel. This could help improve the speed of the surgery.
Using color duplex ultrasonography as part of preoperative planning for an ALT flap provides detailed information about the perforators which will assist not only in accurately locating the perforators during the dissection but also help the surgeon to choose the flap from either right or left thigh. This is because the information on the size and location of these perforators as well as their potential intramuscular course can be provided before the flap dissection. The side of the thigh with a larger perforator, better blood flow, and less intramuscular course could be selected for the relative ease of flap dissection with higher probability of success. In general, a handheld Doppler that is routinely used in the operating room and preferred by many surgeons cannot provide this information. Therefore, the value of color duplex ultrasonography for planning and performing an ALT flap or other perforator flaps should be acknowledged.
Other imaging modalities have also been used for preoperative evaluation of the ALT flap including MRA, CTA, and digital subtraction angiography. Compared to color duplex ultrasonography, digital subtraction angiography is more invasive, necessitates a radiation dose, and the use of contrast producing a 2-dimensional image.14,15 The disadvantage of CTA is it requires radiation as well as an iodinated contrast medium.16,17 Although MRA does not require radiation or iodine contrast medium, it is very expensive and will only detect perforators larger than 1.0 mm.18,19
There are a few disadvantages of this technique, although there are some considerations. First, a smaller hospital may not have access to color duplex sonography and it requires a trained technologist to perform. At our center, it did require some planning when first performing this technique to get the vascular technologist to the preoperative area where they did not frequently image patients. Once the system was set in place, this became a routine and was not an issue. Also, it does not provide a 3-dimensional image to refer to during the case such as more expensive and invasive examinations, for example, MRA and CTA, but we feel this does not outweigh the downsides of these techniques.
The color duplex scan can be a useful imaging modality for planning and performing free ALT flap. It enables surgeons to improve efficiency in the operating room and overall outcomes, as well as shortens the learning curve for less experienced surgeons when first performing these variable perforator flaps. The close working relationship between the vascular technologist and the surgeon may be the key to its success.
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