Week 2: Moving Skin Around

This week I experienced full days in the clinic, OR, and lab with each presenting a unique opportunity to learn. In the clinic, I saw patients coming in for consultation, post-op, and follow up appointments spanning the whole spectrum of surgery planning, recovery, and healing. It was interesting to see patients in the OR that I had met last week in clinic for per-operative appointments. One of the most interesting parts of this week was observing a skin graft procedure. I have learned so much in a short time in the OR and here is what I learned from watching a skin graft operation! 

        This procedure affects 2 part of the patients body: the donor site and the graft site. This operation involved moving a thin healthy section of skin from the thigh to a wounded area.  In this case the patient had already undergone one surgery in preparation for a skin graft because they had a open wound and a poor wound healing response due to other co-morbidities. The first surgery was the addition of a biomaterial layer to the wound. Integra, a collagen hydrogel, is a material that the body can infiltrate and vascularize. This layer is placed on to the wound days before the skin graft operation to allow any underlying healthy tissue and vessels to grow up and into the layer. The addition of integra creates a thinker layer of tissue and increases the chance the skin graft will take. 

          Skin grafts must be placed on highly vascualrized regions to keep the transplanted skin alive. The grafts come in two varieties: split thickness or full thickness. Split thickness grafts include the epidermis and a thin section of dermis whereas full thickness grafts include the epidermis and the entire dermis. In this procedure a split thickness graft was used that was  1/100 of an inch think or about 250 μm.  The properties of the skin graft are determined by the amount of collagen and elastin which control the contractile behavior. The grafts contract in two ways after they are removed from the donor site.  Primary contracture occurs immediately when the skin graft is removed from the donor site while secondary contracture occurs after the graft is put in its new place. In this case with a split thickness skin graft, there is little primary contracture but greater secondary contracture. 

Before the skin is taken from the donor site, epinephrine is injected to cause vaso-contraction and limit the bleeding. Next the surgeon uses a tool called a dermatome to remove the skin graft of the desired thickness.  Click here to see an schematic of the dermatome as it shaves off a thin layer of skin.  This leaves the donor site in a state similar to what to you would experience with a brush burn except that instead of pieces of skin being left in the carpet, sidewalk, or basketball court, the scraped off piece of skin is collected.

        After the skin graft is removed, it is flattened out and rolled through a mesher which is a device that pokes holes into the graft. Meshing the graft allows for fluid drainage, increased flexibility and potential to cover a larger area. The top reason skin grafts fail is because they collect fluid under the surface. To combat this the skin is meshed and force or suction is applied by a wound vac to draw off the excess fluid. I have seen several cases of wound vacuums and they consist of foam placed over the wound followed by the suctioning components, tubes, and dressings. The vacuum suction can be applied continuously or intermittently. Intermittently is slightly better for the wound and graft but this causes more pain because every time the vacuum is turned on, the increase in pressure tugs on the wound. Therefore it is more common to use continuous vacuum pressure to increase patient comfort. The forces applied by the vacuum also promote healing by stimulating angiogenesis, myofibroblast action, collagen production, granulation tissue formation. The skin graft can start to re-vascualrize in 24 hours. Angiogenesis can occur from both sides; vessels can sprout from both the wound bed and the skin graft. When the new vessels meet each other it is called inosculation (derived from the latin word for kissing). The healing process can proceed when the graft is vascularized and connected to the vasculature of the wound.

This week in lab I started working with my first tissue samples from the OR. Back in Ithaca I study obesity and its relationship to breast cancer so here it is great to have the opportunity to access and test human adipose samples making my studies more clinically relevant.  It is a completely different experience isolating samples form tissues composed of human skin and fat discarded during surgery then it is in mice. I dissected the samples, saved them, and am working on adapting protocols for decellularization of the adipose tissue. 

Figure 1: Adipose Tissue I am using for my research project

Meanwhile,  for my adventures in NYC I went to MOMA and got to see works of art such as Van Gogh's Starry Night and Monet's Water Lilies.  I had the chance to see the Statue of Liberty and Ellis Island which were beautiful as well. Weeknight activities include walks to Central Park and stops for ice cream!