The human body protects itself from the external environment by an outer layer of skin and sub-cutaneous tissue (fatty tissue). Skin consists of two layers; epidermis and dermis. The outer portion, epidermis, is composed of epithelium cells (20 to 30 cells deep) which protects the body from bacterial invasion. The inner portion, the dermis, gives skin its strength and vitality. Under the skin is sub cutaneous tissue (fatty tissue) that functions as padding and absorbs pressure preventing injuries to body organs and structures.
Since time began, the human body has had to deal with open wounds due to injuries or diseases. Pressure sores have been found on 5,000 year old mummies in Egypt. When an individual develops an open wound nature attempts to cover the wound to prevent infection by the growth and migration of epithelial cells (the first layer of skin)
This natural method is slow and explains why infection of the wound by germs or parasites is common. Wound management by physicians assist nature by the cleansing and removal of dead tissue from the wound, and by the application of appropriate local dressings onto the wound to create a moist environment. Even though natural healing is often gratefully accepted, the skin cover is fragile and thin (only a couple of cells thick) and liable to break down and form another ulcer. Unfortunately, there is also a limit as to how far cells can migrate!! Some wounds are not able to heal naturally!
Healing by Natural Methods
A wound that healed by natural methods in 8 weeks, during that time the wound was exposed to bacterial microorganisms, fortunately the wound did not get infected and healed. The covering is thin scar tissue of poor quality and cosmetic appearance.
In the 19th century physicians developed methods to remove healthy skin from one area of the body (donor site) and transplant this skin to cover an open non healing wound thereby decreasing the amount of time the wound is exposed to bacterial micro organisms. Such methods are known as skin grafting. Skin grafts involve the transfer of the epidermis (top layer of skin) and a measured portion of the dermis from a donor site to the open non healing wound. Skin grafts are about .020 inches thick and provide only superficial coverage of the wound. They do not replace deeper tissue layers such as subcutaneous tissue and are not able to provide the padding needed to protect bony prominences. Skin grafts are seldom used for pressure sores or diabetic foot ulcers.
Not all skin grafts take! Skin grafts will not take on exposed bone, tendon or an infected wound. Skin also has unique characteristics depending upon its location. It is important that the skin characteristics of the donor and recipient site match. For example you would not want the skin of the face transferred to the sole of your foot or vice versa
Typically the donor site from which the skin graft is harvested will heal naturally, which can take as long as 3 weeks. Wound management of the open wound to which the donor skin is grafted consists of constant dressing changes and can take as long as 2-3 weeks to heal during which time a hospital stay to ensure that the skin graft takes may be required.
While the skin grafts covering these non-healing wounds is quicker than natural methods, final healing is of poor quality and cosmetic appearance. The healing of the donor site results in thin scar tissue of poor quality and cosmetic appearance which can be particularly conspicuous for people of color. Skin grafts sacrifice the well being of the donor site for the needs of the wound site. These donor sites healed in 12 days.
The patient was hospitalized for 14 days
In the search for better quality skin coverage, the 1970's ushered in the era of tissue flaps for closure of wounds. Tissue flaps involve the transfer of skin and underlying structures, such as subcutaneous tissue (fatty tissue) and at times also fascia and muscle to close a defect. Tissue flaps involve detachment of the tissue from its original site, the transfer of the tissue flap to the wound by advancement or rotation and the suture of the tissue flap to cover the wound. In a free flap, the flap tissue is completely removed from the donor site and attached to the wound by micro vascular techniques; in the flap procedures mentioned above there is a base which remains attached and provides circulatory support for the flap.Tissue flaps are major operative procedures with associated risks.
A gluteus maximus rotation flap was performed to close this small ischial pressure sore.(Fig 1) A large incision is made (Fig 2) and the tissue is undermined and dissected free to elevate a flap of tissue. (Fig 3) This tissue flap is then advanced and rotated and the wound is sutured closed. (Fig 4). All flap procedures have the associated risks of major operations that are performed under general anesthesia. Depending upon the size and the location of the wound, a tissue flap may not be able to close the entire wound. A sutured tissue flap can also breakdown when it is sutured under tension or the wound becomes infected when contaminated material is encapsulated under the tissue flap.
The ideal closure of a chronic wound would be one that can quickly cover the wound with local-site, full thickness skin (epidermis and dermis) and also fills the wound cavity with subcutaneous tissue. The new Proxiderm procedure and device offers the physician a means for obtaining this goal by closing chronic wounds in days or a few weeks with better quality skin versus the months to years with traditional treatments.