Overview of Interpolated Flaps
If a person needs a surgery to replace a damaged area of skin, there are different ways to replace the skin that the surgeon might use. These are called local flaps, because the surgeon forms them using skin that is close to the damaged area. The four types of local flaps are sorted by how the surgeon moves the skin to place it over the damaged area. These types include simply moving it forward (advancement), spinning it around (rotation), switching it with the damaged skin (transposition), and moving it under or over the healthy skin that surrounds the damaged area (interpolation).
The last type, interpolation, is sometimes seen as different because the skin is moved over or under healthy skin to reach the damaged area. Because of this, these flaps might need a second surgery to properly place the flap. While needing a second surgery may seem like a disadvantage, the upside is that these flaps often have a good supply of blood and can move more skin than some other types.
The early versions of these interpolation methods, known as “waltzing” or “walking” flaps, were first used by famous surgeons during the World Wars. They need more than one surgery to complete, because the skin is moved to a distance that requires waiting for the skin to heal before moving it again to cover the damaged area. Despite their flexibility, these flaps are rarely used nowadays because the process takes a long time and there are other, quicker methods available.
Here are some examples of the flaps that are used now:
- Paramedian forehead flap
- Melolabial flap
- Postauricular flap
- Tarsoconjunctival flap
- Inferior turbinate flap
- Pericranial flap
- Facial artery musculomucosal flap
- Deltopectoral flap
- Supraclavicular artery island flap
- Pectoralis major myocutaneous flap
Some of these will be talked about in more detail below.
Anatomy and Physiology of Interpolated Flaps
Interpolated flaps, which are used in surgeries, often have a specialized blood supply. This is thanks to a major artery that runs alongside the flap, helping supply blood to it. Flaps from nearby areas have this type of blood supply, while flaps from the local area are often powered by smaller random vessels just under the skin. The specific area of tissue supplied by a single blood vessel is known as an angiosome, and there is typically only one in each flap.
For example, in the case of the paramedian forehead flap, it is usually designed to include the supratrochlear artery, which powers the entire flap. In contrast, the melolabial flap usually doesn’t contain a named vessel but has branches from the angular, nasal, and superior labial arteries. Some flaps have named vessels; still, these are often in the flap’s beginning portion and are powered by the subdermal plexus in the distal part, which is the farthest away from the center of the body. This can cause less reliability in the distal portion.
Due to this, some surgeons prefer to delay certain types of flaps, like the deltopectoral flap, by initially lifting the flap but then replacing it back to its original site. They then plan to transfer the flap 2 to 3 weeks later to increase blood flow and prevent any decrease in flap supply during surgery. This also helps open choke vessels within the flap, improving blood supply in the distal angiosome. By delaying the flap inset, the blood supply in the distal angiosome is enhanced, making it less vulnerable to a lack of blood (ischemia).
However, most other types of interpolated flaps are usually very reliable because of their specialized blood supplies. These flaps are still reliable unless the flap transfer involves twisting the blood supply to a point that the vessels may be blocked. Including a specialized blood supply within a flap offers another advantage. Normally, there are certain rules about the length of a flap relating to the width of its blood supply. These rules do not usually apply to interpolated flaps, letting the surgeon fix larger defects or those located farther from their flap donor sites.
Once the flap is lifted and inserted, the connecting blood vessel or pedicle is left in place to allow blood supply to flow from the recipient site to the flap. For most forehead, melolabial, and postauricular flaps, this connection is maintained for 3 weeks. Then, the pedicle can be divided. For deltopectoral flaps, it may take 4 to 6 weeks before the pedicle can be divided safely.
Why do People Need Interpolated Flaps
Interpolated flaps are a surgical technique used when the region around a wound doesn’t have enough natural skin to heal the area on its own or with a simple graft. This technique is particularly useful for deeper injuries, or ones that cover a large area.
For instance, a paramedian forehead flap might be used when there’s a larger deep wound located on the pointy end of the nose. This is because this technique can provide the necessary skin to cover such defects.
A melolabial interpolation flap can be used on the lower part of your nose, especially on the ala, which is the rounded part of your nostrils. This technique can be useful if one can’t use skin from the nearby areas or if full thickness skin grafts are not feasible.
The postauricular interpolation flap is useful for moderately large wounds located on the helix or antihelix – that’s the curved outer and inner edge of your ear. This technique might be necessary if single-stage flaps wouldn’t fully cover the wound or might cause additional deformity.
For reconstruction of the inner part of the nose, mucosal flaps, like the inferior turbinate and facial artery musculomucosal flap, are usually used. These surgical techniques are common in full-thickness nasal defects or septal perforations, which is a hole in the dividing wall inside your nose.
When treating large wounds on the face, head, or neck, and where other options are not feasible, deltopectoral flaps can be used. This technique involves using tissue from your shoulder and chest region. However, currently, the use of the supraclavicular artery island flap — which involves using tissue from the region above your collarbone — is more common.
In many cases, certain interpolated flaps, like the supraclavicular artery island flap, are beneficial for people who might not be fit to go under general anesthesia for a long period due to heart or lung health issues. These techniques are alternatives to free microvascular tissue transfer, which is a complex operation that involves the transfer of tissues along with their blood supply.
When a Person Should Avoid Interpolated Flaps
Sometimes, a technique called ‘interpolated flaps’ in surgery might not be recommended for certain patients. This includes those who are not willing to go through several stages of surgeries, or those who can’t avoid touching the surgical area due to cognitive limitations. A particular technique called ‘paramedian forehead flap’ is especially tricky because it involves a skin bridge that crosses the patient’s line of sight, which can lead to constant fiddling.
Skin that is currently infected should not be covered with a flap, nor should it be used to make a new one. And surgical flaps should not be used to close areas where cancer is still present, unless there is need of relief from symptoms. Doctors often avoid using skin that has been previously treated with radiation, or a site that has been operated on before, because the blood supply to these areas may be compromised. People who smoke might face additional complications because smoking can increase the risk of tissue death in the flap. However, surgeries involving these flaps can still be performed on smokers provided the flap is not excessively thin.
Surgeries that involve transferring flaps should be undertaken very cautiously in people who are on blood-thinning medications, or have clotting disorders. It is wise to consult with the doctor who prescribed the blood thinners before stopping these medications. Similarly, doctors who are planning to perform a surgery on people with clotting disorders should consult with other specialists before proceeding.
Equipment used for Interpolated Flaps
Interpolated flap surgery is a type of surgery that involves moving healthy skin from nearby areas to a wound to help it heal. This surgery tends to use the same tools as other similar surgeries, but sometimes a few extra items are needed.
Before the surgery, the following things might be used:
- Material to make a template (like non-stick bandage material, surgical cotton, foil suture wrapper, or anything else that can be used to draw out the shape of the flap). This can also be done with a clean method right on the surgical area.
- A local anesthetic, which is a medicine to numb the area where the surgery will be performed.
- A surgical scrub or solution to clean the skin before the operation.
During the surgery, the doctor might use:
- A scalpel (which is a small, sharp knife used in surgeries). The #15 size is mostly used but a smaller #12 size might be preferred in small spaces like inside the nose.
- Forceps, which are a type of tweezers used in surgeries.
- Special scissors to thin out the fat from the flap if needed.
- Small hooks to lift the skin.
- Suture, which is a fancy word for stitches. Both absorbable stitches (which dissolve on their own) and non-absorbable stitches (which are taken out later).
- Gauze, which is a thin, airy fabric used to cover wounds.
- An electrocautery device, which uses electricity to control bleeding during the surgery.
- A measuring tape or calipers to measure the size of the flap.
- A standard soft tissue or flap tray might be needed for larger flaps.
- A doppler ultrasound probe to identify blood vessels. Not all doctors use this, but some find it helpful.
After the surgery, the following might be used:
- Non-adherent petrolatum-soaked gauze as a dressing to put on the raw area of the tissue that was moved.
- Fluffed gauze or other absorbent materials for a bulky post-op dressing.
- Adhesive dressing material or elastic tape to secure the dressing in place.
Who is needed to perform Interpolated Flaps?
Usually, a specially trained doctor, known as a surgeon, together with an assistant, can move skin grafts from one part of the body to another. The assistant’s main role is to help control any bleeding and cut stitches. However, for larger skin grafts, you might need to be put to sleep with general anesthesia in an operating room. This would mean that an anesthesia provider, who is a specialist in putting people to sleep for surgeries, and a team of nurses would also need to be present.
Preparing for Interpolated Flaps
It can be helpful for patients and their families to explain the surgery process using images or drawings, especially when it comes to skin flap surgeries. Without visuals, it might be hard for patients to fully understand the procedure and what to expect after the surgery.
For patients who need reconstruction after skin cancer removal (Mohs surgery), doctors should show them what the area looks like before moving the skin flap. This helps patients understand how much work will be needed to repair the area. In some cases, patients may have small skin cancer spots and not realize that the surgery to remove them might be bigger than they expected. This can be a shock for patients if they find out after surgery that they will need multiple stages of reconstruction.
To help ease worries and show that it takes time to get the final result, doctors can show patients pictures of how the area healed over time in other patients. It’s also important for doctors to explain that there might be smaller follow-up procedures needed in the weeks or months after the first surgery to get the best results.
How is Interpolated Flaps performed
The Paramedian Forehead Flap (PFF) is a surgical technique that has been around since 700 BC and was first used in India. This approach involves the doctor using tissue from the forehead to fix large or deep issues on the nose. Sometimes, the technique is used alongside other procedures for broader defects. The tissue used in PFF is based on an artery located close to the eye. The area of the nose needing repair is analyzed before the application of PFF. The required length for the tissue from the forehead to the affected part of the nose is measured then marked. The medical professional then removes the tissue from the base of the forehead, moving it towards the affected area. The part of the flap that goes into the nasal defect is then secured with stitches.
PFF shouldn’t be used in patients who have a low hairline on their forehead, as they may end up with hair on their nose, and this would require removal through laser treatment or electrolysis afterward.
The Melolabial Flap technique is another surgical technique used since 600 BC in India. With this technique, the doctor uses skin from the cheek to repair problems in the lower part of the nose. A template is made of the area needing repair before the procedure. Measurements are taken to ensure the flap from the cheek will cover the defect without causing tension. The flap is secured to the nose, and the pedicle — the tissue connecting the flap to its original location — is removed after three weeks.
For defects of the ear, specifically the middle part, a procedure known as the Postauricular Flap technique is often used. It was first described in 1950 and involves the doctor using skin from behind your ear. This flap is rarely affected by vascular necrosis (tissue death due to lack of blood). When covering larger defects, a cartilage graft may be added to ensure that the ear maintains its natural shape.
Possible Complications of Interpolated Flaps
Skin surgery, including one called flap surgery, can cause complications. These issues can include infection, scarring, bleeding, damage to nearby areas, need for more procedures, and dissatisfaction with how the surgical area looks. After flap surgery, the surgical area (or ‘flap’) may die partially or completely, needing more reconstructive procedures. Each type of flap surgery can also create other unique complications, such as nose crusting from an inferior turbinate flap, shoulder scarring from a SCAIF, hairline shifting from a postauricular flap, or even hair transfer to the nose tip with a paramedian forehead flap.
After a surgery, bleeding is a common complication. Doctors should focus on controlling this during the surgery and preventing it after. This usually happens in the first 24 to 48 hours after surgery.
The paramedian forehead flap surgery is more prone to post-surgery bleeding, especially near the flap’s pop-up area around the forehead. Doctors can manage this by being careful and precise with electrocoagulation (a procedure that heats tissues) at the end of the surgery, using clot-inducing agents or skin graft on the flap’s base, using extra absorbent material near the flap’s base when dressing, and scheduling a postoperative visit within a few days for a bandage change, provided there is no excessive drainage.
Melolabial flaps don’t generally bleed heavily, but they tend to ooze right after the surgery. Any minor bleeding can be treated during a postoperative visit scheduled within a few days.
When auricular transposition flaps bleed, it can be very difficult to manage because they are located tightly behind the ear. So, preventing the bleeding is very crucial here. After ensuring there is no more bleeding at this end of the surgery, dressing the surgical site and pulling the ear towards the head can help take tension off the flap and reduce the risk of bleeding.
Inferior Turbinate Flaps are prone to drying out due to nasal airflow. To prevent this, placing a cotton ball soaked in petroleum jelly inside the nostril on the flap’s side is common. The patient should replace this daily, and also avoid blowing their nose which may cause more bleeding.
Deltopectoral and waltzing flaps may bleed from their wide, exposed bases. To minimize bleeding chances, tubing the flap’s base and carefully using electrocautery (a procedure that uses electricity to heat tissues) during surgery can be done.
What Else Should I Know About Interpolated Flaps?
A flap is a section of living tissue that is transferred from one part of the body to another. Interpolated flaps are used to fix injuries or surgical wounds on the body that cannot be easily repaired using local, nearby tissue. This can be an effective alternative to more complex and lengthy procedures that involve transferring tissue from one place to another using microsurgery, especially for patients who may not be in the best health to endure long periods under anesthesia.