Overview of Split-Thickness Skin Grafts
Skin grafting is a method where skin tissue is moved from one area of the body to another. This practice is commonly used to help large wounds heal. The idea is to take skin from a part of the body that can recover and move it to an area where it’s needed. Once the skin graft has been fully incorporated, it aids the wound by protecting it from the outside environment, harmful microbes, temperature changes, and excess water loss, much like normal skin does.
There are two types of skin grafts – split-thickness skin grafts (STSG) and full-thickness skin grafts (FTSG). STSG includes the top layer of the skin (epidermis) and a part of the second layer (dermis). On the other hand, FTSG involves the entire dermis along with the epidermis. Skin grafts don’t have their own blood supply, so they depend on the wound area to be well-supplied with blood for the graft to grow into. STSGs can be sourced from various body parts, most commonly from the side of the thigh or the trunk, which are areas that are not easily visible and have large surfaces for easy harvesting. They are also classified based on their thickness into thin, intermediate, or thick STSGs.
Because STSG donor sites still have parts of the dermis left, they can regrow new skin in about 2-3 weeks. This means the same sites can be used again for another skin graft after they have healed, making STSGs extremely useful for treating large wounds or burns where there are limited donor sites.
There are certain benefits and drawbacks to STSGs when compared to FTSGs. Here are a few factors to consider:
- Graft Take: Thicker skin grafts require a healthier wound bed for them to take hold due to their higher metabolic activity. It’s best to avoid grafting thick skin onto unhealthy wound sites such as chronic ulcers.
- Contracture: All skin grafts exhibit primary and secondary contracture. Primary contracture is the immediate shrinking of the graft due to the elastic fibres in the dermis, which is higher in FTSGs as they have more dermis. Secondary contracture is the ongoing shrinking of the graft over time, which is higher in STSGs. For aesthetic reasons, STSGs should not be placed near sensitive areas like the face, eyelids, and mouth, which could be deformed due to contractures.
- Donor Site Healing: The donor site for STSGs is capable of growing new skin and can be used multiple times due to the preservation of the dermis, and in particular the hair follicles. Thin STSGs heal the fastest with the least discomfort. On the other hand, FTSG donor sites require direct closure as they involve removal of the entire thickness of the skin.
- Aesthetic Match: Ideally, the skin graft should match the recipient area in color, texture, and overall look. FTSGs generally provide a better color match, while STSGs can be discolored. Also, the process of creating a grid-like pattern, or ‘meshing’, on STSGs affects how they look.
- Durability: The thickness of the dermis in the graft is important for the strength and resistance of the skin. For example, thick STSGs or FTSG are often chosen for areas of the body that take a lot of strain like the soles of the feet, palms of the hands, and joints, while thin STSGs may not hold up to such pressure.
Some downsides to STSGs could include a poor appearance in relation to the surrounding skin, risk of injury, reduced sensation at the recipient site, need for anesthesia and surgery (compared to natural healing), and a lengthy healing period for both the donor and recipient sites.
Anatomy and Physiology of Split-Thickness Skin Grafts
A split-thickness skin graft is a type of skin transplant that involves the transplanting of top two layers of skin, known as the epidermis and a part of the dermis. The epidermis is the outermost layer of the skin, and it provides crucial barrier protection for your body. It’s mostly made up of cells called keratinocytes but also includes melanocytes and other specialist cells. Below the epidermis is the dermis, which is a bit like skin’s supportive layer. It’s made up of fibers and helps maintain the skin’s strength and flexibility.
Moving on to the actual process of skin grafting, it’s important to know that these grafts don’t have their own independent blood supply. They rely on the area of skin they are attached to for nutrients and blood. The process typically unfolds in three stages:
The first stage is known as imbibition, where the skin graft absorbs oxygen and nutrients from the new area of skin, surviving on what it can take in until it forms its own blood vessels. At this point, the graft might look pale or white. This phase can last up to four days.
Secondly, there’s the inosculation stage. This is when the blood vessels from the graft and the new skin begin to join up, helping the graft establish a fresh blood supply. The graft often looks pink during this phase, which usually begins 48 hours after the graft is applied.
Lastly, the process of revascularization occurs. There is ongoing research about how this exactly happens, but it’s essentially the point where the graft develops its own fully functioning blood vessels, allowing it to survive independently. This typically happens between five to seven days after the graft is applied.
While a skin graft is healing, it’s usually held securely in place to help growth take place. Once the graft is fully integrated into the body and the healing process is complete, the new skin takes on a more normal appearance – although this process can take more than a year and skin may remain uneven in some spots. This is especially true for mesh skin grafts, which use a net-like pattern to help cover larger areas and let fluid drain away, preventing complications.
Why do People Need Split-Thickness Skin Grafts
When a person has a wound that needs to be healed, surgeons use what’s called the ‘reconstructive ladder’. The goal is to find the quickest and simplest way to close the wound, while also aiming for the best possible appearance after healing.
One technique that is often used is called a split-thickness skin graft. This is done when the simpler methods of wound healing won’t work. These simpler methods may include healing on its own, stitching the wound closed, or using a technique called negative pressure wound therapy which helps to speed up the healing process.
To do a split-thickness skin graft, the surgeon needs an available area of healthy skin from the body (the donor site) and a wound area that has good blood flow and is free of infection (recipient site). Skin grafts are often used to cover areas where the skin is very deeply damaged or missing entirely. They can also be used to cover muscles. Skin grafts can survive on any wound area with blood flow, even ones covering tendons, cartilage, or bone, as long as certain thin layers of tissue in those areas are intact.
In cases where these thin tissue layers are not present, the skin graft won’t work. Split-thickness skin grafts are mainly used in cases of acute skin loss, such as burn wounds, traumatic wounds, and infections. They can also be used for chronic skin loss, like leg ulcers, and as a support to other procedures, like to cover a muscle flap.
When a Person Should Avoid Split-Thickness Skin Grafts
There are certain situations where treating a wound may be absolutely not possible or recommended:
If a wound is currently infected, continuously bleeding, or in an area with known cancer, it can’t be treated the usual way. Also, if a wound exposes bone, tendon, nerve, or blood vessel without an appropriate covering layer, the usual wound treatment methods may not be suitable.
There could be other situations where normal wound treatment isn’t advisable. For instance, if a wound is over a joint or an important body marking where healing could reduce movement or change appearance, such as the wrist, elbow, or eyelid. Also, if a wound has previously been exposed to radiation, regular treatment might not work as effectively.
Lastly, doctors or nurses will take into account individual patient factors like smoking, the use of blood-thinning medication, bleeding disorders, prolonged use of steroids, or malnutrition. They will assess these on a case-by-case basis before deciding on the best treatment.
Equipment used for Split-Thickness Skin Grafts
Getting a Skin Graft
The skin grafting process begins with harvesting, or collecting, a split-thickness skin graft. This involves taking a thin layer of your skin from another part of your body to use in the graft. This is done with different kinds of surgical tools. They can use a common surgical knife, a special oscillating knife, or most often, a machine called a dermatome that runs on either air or electricity. This machine can collect skin grafts in a consistent manner and can be adjusted to get grafts of different thicknesses and sizes.
After the skin graft is collected, it goes through a process called meshing. They can simply make small holes in the graft with a surgical tool, or use a manual hand-powered machine, often used by surgeons. This machine makes multiple cuts at regular intervals. The skin graft is then placed into the machine and hand-cranked through. Meshing a skin graft allows the graft to be stretched, covering a bigger area. The larger the meshing ratio is, the larger area the skin graft can cover. However, it might also lengthen the healing time because of the larger area to be covered with new skin. The holes in between the skin graft act as drainage for any fluid, preventing it from building up and causing graft failure.
Other tools are also used, like mineral oil which is used to make the machine slide better on the skin graft donor site. A sponge soaked in epinephrine (a medication that narrows blood vessels) is placed where the skin graft was taken from to minimize blood loss. Special forceps, a surgical tool used for grasping and holding things, are used to take the skin graft from the dermatome.
The harvested skin graft is then secured, or fixed, to the recipient site, which is the area where the skin graft is needed. This can be done using skin staples, which are faster to apply than stitches but need to be removed after the graft has healed or stitches that naturally dissolve after some time and do not need removal. Certain types of medical glue can also be used.
A dressing is then applied over the skin graft. For smaller grafts, a type of gauze soaked in petroleum, cotton balls, and non-dissolvable stitches can be used. For larger grafts, the same petroleum-soaked gauze and additional common gauze can be used. The covering should not be left open to air. The area where the graft was taken from is dressed with the same petroleum-soaked gauze and clear adhesive, then covered with different kinds of dressing materials and wrapped. Another option is using an anti-microbial foam dressing.
Who is needed to perform Split-Thickness Skin Grafts?
A doctor who specializes in surgery and a helping hand can collect thin slices of skin for a procedure known as a skin graft. Skin grafting is a type of surgery where skin is moved from one area of the body to another. This surgery is quite common and is usually done to cover areas where skin has been lost, such as in severe burns, or wounds. The skin is usually taken from an area that is hidden or does not have hair, like the side of the thigh. This procedure is relatively safe, but like any operation, there can be complications, which are minimized by following the doctor’s instructions.
Preparing for Split-Thickness Skin Grafts
One important step before a skin graft surgery is the process of informed consent. This is when the doctor explains to the patient what to expect after the surgery, how long it will take for the area where the skin will be taken from (the donor site) and the area where the skin will be placed (the recipient site) to heal, and the overall concept of skin grafting.
Another key step in preparation for the surgery is making sure the area where the skin graft will be placed is clean and ready to accept the graft. This area, known as the wound bed, must be properly cleaned through a process called debridement. Debridement can be done in several ways, including using a scalpel, a special tool called a Norsen debrider, a zip-like device called a dermatome, or a water surgery device, until the base of the wound is showing healthy bleeding tissue. It’s also important to make sure the edges of the wound are clean and that there’s no dead tissue or pus present. If the wound base isn’t clean, the skin graft won’t be able to properly heal.
Choosing the right donor site, or the area where the skin will be taken from, is also crucial. The choice depends on several factors, including how much skin is needed for the graft, the position of the patient during the surgery, how easy it is to take skin from that area, and how it will look after the surgery. Often, doctors choose areas that are flat and wide, like the thighs or back, because they provide a lot of skin and are relatively easy to work with. Hospitals often choose areas that will usually be covered by clothing for aesthetic reasons. The skin on the back and thighs is usually thicker than other parts of the body, so the doctor might adjust the thickness of the skin graft accordingly. If the patient has large wounds or burns, the choice of donor site might be limited by where there is still healthy skin.
How is Split-Thickness Skin Grafts performed
Harvesting a split-thickness skin graft involves taking a slice of skin from one area of the body (the donor site) and placing it onto another area that needs skin (the recipient bed). This technique often uses an air-powered tool called a dermatome. The process begins with preparing the recipient bed.
First, the doctor will need to clean the recipient bed. This involves removing any unhealthy tissue until only healthy bleeding tissue remains at the base of the wound. The edges of the wound may also need to be refreshed.
Next, the doctor will measure the recipient’s wound bed. The size of the wound will determine the size of the skin graft that needs to be harvested.
The dermatome, which is the tool used to remove the skin graft, is then connected to an air-source. The device is then briefly turned on to make sure it’s working properly. A fresh blade is inserted into the dermatome and the desired width is chosen.
Based on the width of the guard (a component of the dermatome), the doctor will determine the length of the graft needed. Using a surgical marker, they will then mark this length on the donor site. A substance like mineral oil is used to make the process of removing the graft with the dermatome easier.
The doctor, along with the help of an assistant, will then tighten or hold the skin at the donor site. The dermatome is turned on and brought into contact with the skin at a 45-degree angle. After making skin contact, the angle of the dermatome is lessened to be parallel with the skin. As the dermatome is smoothly pushed forward with steady pressure, the graft is removed.
The skin graft is then detached from the donor site using a scalpel or scissors, and the graft is placed in normal saline (a salt water solution) until ready to be used. An epinephrine-soaked item might be applied to the donor site to minimize blood loss.
If needed, the skin graft can be meshed (cut into a mesh pattern). This can be done with a scalpel or a skin graft mesher (another kind of tool). The graft is then carefully moved to the recipient bed, making sure that the correct side (the dermis, which is brighter and always curls down) is facing the correct way. If it’s not placed correctly, the graft won’t take.
The graft is then secured with skin staples or sutures and covered with a special dressing or vacuum device to help it heal. The donor site is also dressed up to promote healing.
Possible Complications of Split-Thickness Skin Grafts
If you’ve had a skin graft, where a piece of your skin is moved to cover a wound, it’s important to understand the potential complications that might happen.
In the short term, any build-up of fluid between the piece of skin that was moved (the skin graft) and the wound can cause problems. This build-up could be things like excess fluid (seroma), a type of blood clot (hematoma), or an infection. Injuries from shearing or pulling can also interrupt the healing process. Sometimes, the graft might not completely take or adhere to the wound area, which can affect the healing process.
In the long term, it’s common to experience things like wound tightness (contracture) and differences in the skin’s appearance, like changes in color or texture between the graft and the original skin.
The success rate of a skin graft is usually around 70-90%. This means that, most of the time, the graft adheres to the wound and helps it heal. However, there are some factors that can make a skin graft less likely to be successful. These include having a large area of burned skin (over 35%), being older than 55 years old, or having diabetes.
What Else Should I Know About Split-Thickness Skin Grafts?
Split-thickness skin grafts are a type of surgery where a thin layer of skin is removed from one part of the body and moved to an area of the body where skin has been damaged or lost. This new skin typically sticks to the new area properly about 5 to 7 days after the surgery. The bandages put on during the surgery are kept on for the same amount of time to help the new skin heal correctly without being disturbed.
Between 5 to 7 days after the surgery, the bandages are removed and the new skin is checked. It should look pink at this point, which is a good sign that the new skin is reconnecting with the blood supply. For the next week to two weeks, the dressings should be changed every 1 to 3 days. This can be done with different types of bandages and can be done by the patient, a nurse at home, or at a wound clinic.
About 2 to 3 weeks after the surgery, the new skin should be fully attached and covered with fresh skin cells, so the patient can start showering and bathing again. Also, the frequent bandage changes can be stopped. To help the new skin keep healing, lotion can be applied.
