Overview of Free Tissue Transfer of the Lateral Thigh and Anterolateral Thigh
The anterolateral thigh (or ALT) flap is a medical technique that was first introduced by a doctor named Song in 1984. Since then, it has become a widely used method in reconstructive microsurgery, which is a type of surgery that involves repairing or replacing damaged tissues and blood vessels. ALT flap technique is really versatile, meaning it can be adapted for many different uses.
Some great things about this flap technique include: it has a long ‘vascular pedicle’ (which is basically the main blood vessel that supplies the flap), it allows surgeons to work with large skin areas without causing more harm to the donor site (where skin is taken from), and it can be adapted to make it sensitive to touch. It can be used to manage gaps in blood vessels in the limbs, it can be folded for use as a double skin paddle (which is a kind of graft), and it can also be used as a ‘chimeric’ flap (a kind of graft that uses tissue from two different places) to repair combined soft tissue injury in almost any part of the body.
A two-team approach allows one team to remove the flap at the same time as another team prepares the area where the flap will be placed. The ALT flap can also be used for reconstructing the breast if skin from the lower abdomen is not available because of earlier scars or surgeries.
Harvesting, or removing, the ALT flap is relatively straightforward as long as certain guidelines are followed. The flap has a reliable blood supply, despite some variability in its ‘perforator anatomy’ (the exact layout of its small blood vessels).
Anatomy and Physiology of Free Tissue Transfer of the Lateral Thigh and Anterolateral Thigh
The anterolateral thigh flap is a type of surgical procedure, where a piece of tissue from the front and outer side of the thigh is moved to another part of the body. This flap of tissue is generally fed by blood vessels that come from the femoral artery in your thigh. These blood vessels are also known as ‘perforators’ because they pierce through the muscle to reach the skin.
Interestingly, earlier studies suggested that these perforators mainly traveled along the lines between muscles (septocutaneous perforators). However, more recent research has shown that the perforators that go through the muscle (musculocutaneous perforators) are actually the main source of blood to this flap.
The area of the thigh that can be used to create this flap extends from the front top hip bone down to the outer side of the knee. It also stretches from the inner edge of the large muscle on the front of the thigh to the border of the hip bone.
Now, the femoral artery gives rise to the lateral circumflex femoral artery, which further divides into three- ascending, transverse, and descending branches. It’s the descending branch that runs along the inner edge of a large outer thigh muscle, supplying blood to the front and outer thigh skin.
Moreover, this flap provides a relatively long tube-like structure (known as a pedicle) that the tissue is attached to. This pedicle contains the blood vessels that keep this flap alive after it’s moved to a new place in the body. The thigh flap can also include a nerve, which allows for feeling, or a piece of muscle, to make it functional.
Additionally, there is another thigh flap, called the lateral thigh flap, used for specific surgical reconstructions, like repairing pressure sores on the hip. This flap is supplied with blood mainly by the other two branches (ascending and transverse) of the lateral circumflex femoral artery. This flap can also be based on the same perforators as the anterolateral thigh flap and can be used for repairing areas in the groin or abdominal wall.
Why do People Need Free Tissue Transfer of the Lateral Thigh and Anterolateral Thigh
The ALT flap (Anterolateral Thigh Flap) is a procedure that uses skin and tissue from the thigh to repair different parts of the body. It’s a versatile method used in many different situations, including:
1. Head and Neck Reconstruction: Doctors use the ALT flap to repair areas in the head and neck after the removal of tumors. It can sneak into small areas or fill in larger defects, especially in people with a higher body mass index. It can even be used to rebuild the esophagus (the tube that connects your throat to your stomach) by folding it to create a new “tube”.[1][7][8][9]
2. Secondary Burn Reconstruction: If someone has extensive scarring due to burns, doctors use the ALT flap to replace the scar tissue and help prevent it from coming back.[10]
3. Breast Reconstruction: The ALT flap can be used to reconstruct breasts using skin from the thigh if the skin from the lower abdomen isn’t available because of previous scars or surgeries. It can also be used if the initial breast reconstruction fails.[11][12]
4. Abdominal Wall Reconstruction: The ALT flap can help rebuild the lower part of the belly using the thigh’s skin and tissue. For larger defects, doctors may use the ALT flap using various components like skin, tissue, and even muscle.[13][14]
5. Upper and Lower Extremity (arm and leg) Reconstruction: This procedure can help rebuild the area around the knee and the lower part of the leg and foot. It can even help restore blood flow in a leg lacking proper blood supply. Apart from this, it can also be used for extensive repairs to the upper arm or for aiding the movement of tendons.[15][16][17]
6. Perineum and Penile Reconstruction: Doctors use the ALT flap to rebuild the perineum (the area between the anus and the genitals) and the penis. This technique can also be used in gender reassignment surgery (female to male) for creating a penis.[18][19]
When a Person Should Avoid Free Tissue Transfer of the Lateral Thigh and Anterolateral Thigh
There aren’t any definite reasons why a doctor would not use an anterolateral flap, which is a piece of skin and tissue used to cover up a wound or replace lost skin.
There are, however, certain conditions that a person might have that can make it less suitable or more risky for this procedure, including:
- Being severely overweight
- Having a major disease in the arteries that can reduce blood flow, making it difficult for the flap to receive ample blood supply
- Having previous damage or scarring on the skin of the thigh where the flap is typically taken from
- Having other severe medical conditions which can make a long surgical procedure unsafe.
Equipment used for Free Tissue Transfer of the Lateral Thigh and Anterolateral Thigh
To conduct a procedure known as “flap harvest,” which is often performed in reconstructive surgery, surgeons need a specific set of tools. These are similar to the tools used in many surgeries where tissue is moved from one area to another (known technically as free flap microsurgical cases).
Before the surgery, the surgeons use a clean plastic sheet (or drape) to map out the area that needs repair. They also use a hand-held Doppler device, which helps locate the blood flow in your body. Skin markers are used to make notes on your body for the surgery.
During the surgery, surgeons wear magnifying glasses (or loupes) to see the area they’re working on more clearly. They also use a surgical microscope with high-quality optics to accurately connect small blood vessels, a process known as microsurgical anastomosis.
The instruments used in this surgery include regular plastic surgery instruments – skin hooks to pull back the skin, self-restraining retractors to hold tissue out of the way, Adson and Debakey forceps (kind of tweezers) for careful handling of tissue, sharp tenotomy scissors, vessel clips, skin dermatome for removing a thin layer of skin, and mesher device. Microsurgical tools like jeweler forceps, a Castroviejo needle holder, vessel dilator forceps, small scissors, and microvascular clamps for controlling the blood flow are used, along with very thin sutures (stitch thread) for sewing things together.
To keep the blood vessels from narrowing (vasospasm), the surgeons will use saline solution mixed with a blood thinner medication called Heparin, Lidocaine solution (a local anesthetic) and papaverine solution. After the surgery, materials needed are plaster of Paris slabs (to immobilize the treated area), burn gauze, soft bandages and wool, stretchy bandages, and sterile and antiseptic dressings to protect the wound from infection.
Who is needed to perform Free Tissue Transfer of the Lateral Thigh and Anterolateral Thigh?
In some cases, it can be practical to have two teams participate in the creation of tissue patches, also known as ALT flaps. For example, if these flaps are being made for use on a lower limb, the main doctor may be in charge of creating the flap while a less experienced doctor or colleague gets the receiving site ready. This includes revealing the blood vessels so they can be connected microscopically to those in the flap. The use of this two-team method means that two scrub nurses (those who help with surgery in a sterile environment) and one circulating nurse (who ensures everything outside the sterile field runs smoothly) are needed. If a tourniquet (a device for stopping blood flow) is used, the circulating nurse will need to keep an eye on when it’s switched on and off and how long it’s been used.
An anesthetist (person who gives the anesthesia) and an anesthesia technician (the assistant to the anesthetist) are also needed for this procedure. After the operation, the patient will need to have the tissue flap checked daily for signs of health and proper connection for about a week. This checking will be done by nurses who have been trained specifically to monitor the condition of relocated tissue patches.
Preparing for Free Tissue Transfer of the Lateral Thigh and Anterolateral Thigh
The process of getting a tissue flap from the thigh (flap harvest) usually happens under general anesthesia, which means you’re completely asleep. You’re lying on your back during this. Before the operation, the surgeon checks your thigh’s skin thickness with a simple pinch test. This gives them an idea of how they’ll close the thigh after removing the flap. They may need to take a thin layer of skin from your other thigh, or they’ll be able to pull together the skin already there. For patients with problems in their blood vessels (peripheral vascular disease), a special type of X-ray known as a CT angiogram can be used to check the blood flow to the limb and see where suitable blood vessels are.
Prior to starting the procedure, any hair on both thighs will be trimmed. It’s crucial that your foot and leg remain straight and pointing towards the ceiling. They must not rotate at any point because that’s essential to correctly obtaining the flap.
Before the operation starts, the surgeon makes some marks on the skin. They do this by drawing a line from the front part of the hip bone to the outer edge of the knee cap, highlighting where one muscle turns into another. This line serves as a guide during the procedure. Halfway along this line, they draw a small circle. This helps them locate the important blood vessels required for the flap. They use a handheld device to find and mark these blood vessels. The surgeon then plans the size and position of the flap according to the size of the area that needs it. The flap’s position can be in the center or slightly to the side, the latter providing a longer blood vessel supply. After that, they clean the surgical site and drape it with sterile covers for the operation.
The flap is brought out and marked in a way to make it easier to close the thigh afterward naturally. But, if a large flap is needed, they can take flaps up to 35 cm x 25 cm based on a single blood vessel. In this case, closure of the thigh will likely require grafting skin from elsewhere.
How is Free Tissue Transfer of the Lateral Thigh and Anterolateral Thigh performed
The ALT flap is a method doctors use to repair tissue damage. It can be obtained in various ways, based on what you need. A thin flap using skin and just beneath the skin tissue can be used or a thicker flap made of skin, underlying tissue and muscle can be collected. It can also be obtained from just the layer of tissue below the skin. In other cases, it can combine different tissues, each with their blood supply.
The process of getting the flap starts with making an opening on the inside border of the flap and gently opening up the tissue until we reach the tissue layer covering the muscles. This area is where the supplying vessels for the flap may occur. If not, we look for supply vessels that arise from the vastus lateralis, a muscle in the thigh. All possible supply vessels are identified and the best ones are chosen to supply the flap.
Once the best supply vessels are identified, we gently move the surrounding muscle to expose the deeper vessels. These vessels are then carefully dissected. At this stage, various small branches will be encountered and will need to be tied off. The dissection proceeds until the selected supply vessels are traced back to their main source. Sometimes a bit of muscle can be included with the flap, avoiding the time-consuming step of isolating the supply vessels. An important thing to remember during the opening up of these tissue planes is the main nerve supplying the thigh muscles, the lateral femoral cutaneous nerve, which needs to be preserved if we are not harvesting a sensory flap.
If you need a thin flap, such as for the back of the foot, hand defects, and neck defects, we can thin down the tissue from within, ensuring that we do not compromise the blood vessels. The thinning down must be done carefully to ensure we leave enough tissue around the blood supply to prevent injury and compromise of the flap. This depends on maintaining a good blood supply from the vessels we have chosen as the main supply.
Once this is done, the blood supply to the flap is divided and the time is noted. The flap can then be moved to the defect, temporarily fixed in place and then the small vessels supplying the flap are connected to those at the site where the flap is being moved using fine thread. After this, we need to ensure that the blood is flowing well through these vessels and that the flap is healthy.
Once the flap has been confirmed as healthy, it is permanently fixed in place. Drains are inserted underneath the flap to prevent build-up of fluid and the area is then dressed. The area where the flap was obtained can be closed directly, or if this would be too tight, a split-thickness skin graft can be used.
If the supply vessels to the ALT flap are absent or not good quality, there are four alternative options: the exploration of the muscle and blood vessels on the outer side of the thigh, the exploration of vessels on the medial side of the thigh, the elevation of a muscle flap from the outer thigh muscle, or looking for alternative donor sites.
Possible Complications of Free Tissue Transfer of the Lateral Thigh and Anterolateral Thigh
One of the biggest concerns after a type of surgery called a free flap transfer, is that the relocated tissue (flap) might not survive. Therefore, it’s really crucial to monitor the flap after surgery. There are several reasons why a flap may fail:
* Not enough blood flow through the veins or arteries – veins being the most common problem (eight or nine times out of ten)
* Clotting of blood (thrombosis)
* Blood getting stuck and not flowing properly (venous congestion)
* Twisting of the ‘stalk’ that connects the flap to the main body (the pedicle)
* Squeezing or pressing on the pedicle
* Too much tension at the edges of the flap, which could lead to loss of tissue around the edges.
There are also other problems that could happen after the surgery:
* The color of the flap might not match the color of the skin where it was attached
* The flap might be too bulky, which could lead to fat cells dying (fat necrosis)
* A swelling filled with blood (hematoma)
* A swelling filled with clear fluid (seroma)
* Infections
* The wound might take a while to heal
* The wound could split open (wound dehiscence)
* The site where the flap was taken from might have thick, raised scars (hypertrophic scarring)
* The skin graft, which is skin taken from a different part of the body to cover the donor site, might not ‘take’ or attach properly
* There could be a loss of feeling in the thigh where the skin graft was taken from.
What Else Should I Know About Free Tissue Transfer of the Lateral Thigh and Anterolateral Thigh?
The process of moving an “anterolateral thigh flap”(a piece of skin and underlying tissue from the thigh) to another part of the body is a common and highly successful procedure in reconstructive surgery. It’s successful more than 95% of the time, and is used for repairing various body parts from head to toe.
The reasons why doctors often choose this method are:
- It’s relatively easy to do since the thigh’s structure is usually predictable
- The thigh has a large and long blood vessel that can supply the transplanted tissue
- They can modify the flap according to the requirement of the place where it’s moved. They can make it thinner or use a technique called ‘chimeric flaps’ if needed, this means they use tissue types from the same area but with different blood supply.
- It’s possible to use this flap in a way that allows the patient to still have feeling in that area
- Using tissue from the thigh doesn’t usually cause any major problems at the place the tissue is taken from
- Moving this flap can be done in a way that reduces the time the patient spends in surgery, because two medical teams can work at the same time – one harvesting the flap and the other preparing the recipient site.
So overall, this technique has proven to be very beneficial in the world of reconstructive surgery.
