What is a skin graft?
Roberta Torricelli
The skin is the largest organ in our body, with a total area of (2m2) it is about 16% of our total body weight! It consists of a number of layers each of which has precise anatomical and histological features as well as different functions. The most superficial layer is known as the epidermis (epi means above), it consists predominantly of keratinocytes, they are the main cells involved in regeneration of the skin and give us our waterproof barrier to the world. However, other cells and structures can be found in this layer, including melanocytes (pigment cells), sensory cells and nerve endings, sweat glands and hair follicles, as well as plenty of immune cells such as macrophages. The layer below the epidermis is the dermis, this is the thickest layer and is made up of fibrous and elastic tissue to provide strength and flexibility to the skin. This layer is also full of nerves and blood vessels.
Due to its rich cellular environment, the skin holds a fundamental role in a number of bodily functions, including temperature regulation, immune defence, UV protection and sensation. Damage to the skin, especially when extensive, can therefore represent a significant threat to our body balance, which explains why our skin is very good at regenerating itself. However, in some cases injury and infection can exhaust this regenerative capacity leading to the skin failure to repair on its own, even in the presence of stitches. It is under these circumstances that skin grafts are applied.
Skin grafting is a surgical procedure that involves applying “extra” skin to the exposed area of injury, such as a deep or large burn. The most common procedure involves obtaining skin directly from the patient from a different area of the body, this is known as an autograft (auto means self). The surgery is usually performed with the patient under general anaesthesia, therefore asleep and pain-free. Healthy skin is then taken from the “donor site”, often a hidden area such as the buttock or the inner thigh, and transferred onto the injury site. Most autograft surgery are “split-thickness” skin grafts; this means that the epidermis and only a small section of the dermis will be retrieved from the harvest site. However, should the injury be deeper and more serious, a “full-thickness graft”, so epidermis and full dermis, can also be obtained from our chest wall, back or abdominal wall.
As for every procedure, skin grafting also carries some risks, the most commonly observed ones are bleeding, slow healing and infection. Equally, skin harvested from a different body region might not have the same properties of the skin found at the site of injury. It might therefore appear uneven, report poorer sensation and appear discoloured. For this reason, current research is looking into growing skin grafts directly from a sample of skin of the patient. Hopefully this technique will allow for better healing and an overall better functional outcomes.
Finally, other options of skin grafting exist, although they can come with a greater risk of rejection or slower healing and are therefore only used under specific circumstances. For example, it is possible to harvest a graft from another donor, this is known as an allograft (allo means different), this is normally done when it could be difficult to obtain skin from elsewhere in the patient. In other cases, a xenograft (xeno means alien), skin obtained from an animal donor, such as pigs, can also be used. Synthetic skin substitutes are also available, and they can replace both the epidermis and the dermis.