and Israel Iglesias1
(1)
Department of Plastic Surgery, University Hospital Montepríncipe, Madrid, Spain
34.1 Introduction
34.2 Graft Survival
34.3.1 Recipient Site
34.3.3 Graft Shearing
34.3.4 Infection
34.3.5 Poor Systemic Conditions
34.3.6 Technical Errors
34.4 Graft Rescue
34.1 Introduction
Skin grafts are used in a variety of clinical situations. The essential indication for the application of a skin graft is wound closure. Skin grafts are usually the initial treatment of choice for many open wounds that cannot be closed primarily. Skin grafts are generally avoided in the management of more complex wounds. Anfractuous wounds; exposed bones, tendons, nerves, or vessels; and deep pressure ulcers normally require the use of flaps for stable wound coverage. Skin grafts have limited success in wounds with a compromised blood supply, such as irradiated wounds or ischemic ulcers.
Skin grafts can include either a portion of dermis (split-thickness graft) or the entire dermis (full-thickness graft). Split-thickness grafts can tolerate less vascularization of the recipient site but have a greater amount of contraction. The donor site generally heals spontaneously, through epithelialization from cells of hair follicles and sweat glands. Large areas of split-thickness grafts can be taken to cover big defects such as in large surface area burns. Full-thickness grafts require a better vascular bed for survival but undergo less contracture. Thus if the recipient site is not well vascularized, full-thickness grafts have a greater chance to become necrotic. Full-thickness graft donor sites must be closed primarily. Thus full-thickness grafts are only used to close small wounds, especially in the face because of better color matching and less contraction.
A skin graft is essentially a skin transplantation. The graft is completely severed from its blood supply, drainage system, and sensory innervation. The graft is placed onto a vascular bed so that it will become vascularized and sensate. So the survival of the graft completely depends on the recipient site. A skin graft becomes partial or totally necrotic when it fails to be vascularized from the recipient site. Necrosis of the transplanted skin is a complication of the procedure and can be related to the grafting technique, to the conditions of the recipient site, or to both of them.
34.2 Graft Survival
The process of graft survival has not been completely understood although it is accepted that it includes two phases: serum imbibition and revascularization.
Serum imbibition describes a well-understood series of events. After a graft is harvested, the graft vessels go into spasm, evacuating any old blood and serum. Once laid onto the recipient site, the graft passively absorbs the underlying serum. The graft becomes edematous and can increase in mass by as much as 30 %. Metabolism in the graft converts to anaerobic metabolism and the pH in the graft falls to 6.8. Metabolism waste products from anaerobic metabolism may stimulate the revascularization process. The graft remains edematous and in anaerobic metabolism for approximately 48 h until revascularization occurs and the graft is able to unload its waste products.
Throughout the phase of serum imbibition, endothelial ingrowth from the host into the graft is occurring. Thus, vascular flow through the graft can be established as quickly as possible. Serum imbibition phase and revascularization phase can be thought of as overlapping rather than as mutually exclusive.
The phenomena occurring during the revascularization phase have been a matter of research for more than one century. In 1874, Thiersch proposed the theory of inosculation. This theory states that the cut vessels from the host bed line up with the cut ends of the vessels of the graft and form anastomoses. The process begins immediately, and vascular connections have been demonstrated as early as 22 h after grafting. At the beginning of the twentieth century, some authors proposed another theory. These works indicated that the original vasculature in the skin graft degenerates. Endothelial cells and capillary buds from the host invade the graft, restoring blood flow. Again, the process begins immediately, and as early as 9 h after grafting, inflammatory cells can be seen invading the graft. By the fourth postoperative day, flow through the graft has been reestablished. More recently, a third theory, first proposed by Henry, has evolved to describe skin graft revascularization. This theory states that the original vasculature of the graft does indeed degenerate. However, the acellular basal lamina persists, providing a conduit for the ingrowth of the new vascular tree from the host bed. Histologic studies have identified acellular patent vascular channels in the skin graft 48 h after grafting, which later become endothelialized from the invading host capillary buds.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
