71 Full Thickness Skin Graft
Full-thickness skin grafts are a commonly performed surgical procedure for the management of a certain subclass of soft tissue defects. The unique role of the human hand requires durable and sensate skin surfaces to accommodate for a variety of positions and fine motor tasks essential for the purposes of daily living. Most commonly, full-thickness skin grafts are utilized on the volar surface of the hand, as they have been shown to limit contracture and preserve motion. Given their lack of intrinsic blood supply, full-thickness skin grafts are limited to surfaces that have adequate vascular beds, and cannot be used on bone or tendon without intact paratenon. Unique challenges faced during full-thickness skin grafting include adequate selection of donor tissue, preparation of a viable wound bed, and avoidance of hematoma and limiting of shear forces in the postoperative period.
Skin grafting is a commonly performed surgical procedure that comprises a step on the reconstructive ladder, which is designed to address wounds that cannot be left to heal by secondary intention or closed primarily. The skin is an organ with a multitude of diverse functions, serving as a means of homeostasis, sensory input, and selectively permeable barrier. In general, the overall structure of the skin is conserved, with a thinner layer of epidermis covering the underlying thicker dermis, but specific subcomposition varies depending on anatomic region and intended function.
Skin grafts are predominately divided into two major types: split and full-thickness. Split-thickness skin grafts (STSGs) comprise the epidermis and a part of the dermis. These grafts are traditionally harvested with a dermatome; thus, allowing the donor site to heal secondarily and experience a greater degree of secondary graft contracture. Full-thickness skin grafts comprise the epidermis and the entire dermis, are traditionally harvested with a scalpel, require primary closure, and experience less secondary graft contracture.
The role of the human hand in carrying out vital life functions cannot be understated. With regard to the skin, there are several unique functions of the hand that must be accommodated, and it is useful to divide the hand into palmar and dorsal surfaces to recognize these diverse roles. The palmar skin comprises a thicker epidermis, and is devoid of hair and sebaceous glands, features designed to enhance grip and accommodate for pinching. Deeper dermal papillae and enhanced keratinization of the epidermis helps in accomplishing these roles. In addition, the palmar skin must be uniquely sensate, allowing for interaction with the environment and tactile feedback during fine motor tasks. This is accomplished by a high-density of specialized sensory appendages, such as Pacinian and Meissner’s corpuscles, that line the dermal papillae and provide valuable sensory feedback.
The skin on the dorsum of the hand is less specialized than that of the palmar surface, but must still be able to accommodate the multitude of positions and actions that the human hand performs on a daily basis. As such, it is more elastic than the palmar skin, and contains hair follicles, but is still adequately durable to protect the underlying tendons and muscles in movement, particularly during flexion.
71.2 Key Principles
There are several unique principles that should be followed when evaluating the need for a full-thickness skin graft. As a guideline, full-thickness skin grafts are used only when durable, sensate skin with limited contracture is a requirement. In general, adequate skin for full-thickness skin grafting is less readily available than for STSGs. Technically, full-thickness skin grafts require a more robust vascular bed, making graft take more difficult. Moreover, they are more prone to infection than splitthickness grafts.
With regard to the hand, full-thickness skin grafts are traditionally reserved for the volar surface of the hand. Glabrous donor sites contain a high-density of mechanoreceptors, and are devoid of hair, offering the best chance for a durable, sensate, and functional volar surface. Hair follicle transfer is an unwanted consequence of transferring nonglabrous skin and can result in a less aesthetic outcome.
Selection and preparation of an adequate wound bed is paramount in determining the success of full-thickness skin grafts. As skin grafts do not have their own blood supply, they are dependent upon the recipient site for survival. Initially, the graft is nourished by a transudate from the wound bed in a process called plasmacytic circulation. Within several days, capillary ingrowth will begin to nourish the graft, as vascularization begins to develop. This process is dependent on the maintenance of a healthy wound base, as hematoma or any barrier between the graft and bed will result in failure to take. For similar reasons, full-thickness skin grafts directly onto bone or tendon, without intact paratenon, are contraindicated. 1
The management of wound contracture is of particular importance with regard to managing soft tissue defects of the hand. In general, any violation of the dermis has the ability to undergo wound contracture in a process mediated by myofibroblast infiltration. The subsequent production of collagen fibrils results in wound edge contracture, which can result in potentially devastating losses of function with regard to volar surface injuries. A study by Rudolph evaluated myofibroblasts and wound contracture in an animal model. Microscopic and histologic findings suggest that full-thickness skin grafts function by speeding up the myofibroblast life cycle and therefore result in less wound contracture than STSG or granulation. 2 Overall, this translates into a more functional outcome with less need for subsequent reconstructive procedures.
Timing for skin grafting is a delicate balance between establishing a healthy, viable wound bed to maximize the potential for graft success and prompt timing to limit contracture. Traditionally, early debridement of the wound bed is performed and grafting is carried out within 2 to 3 days to maximize outcomes.