So, now the wound is clean and covered with healthy granulation tissue and is ready for skin grafting.
Donor site: The thigh is the most common split thickness skin graft (STSG) donor site because the area is easy to access and has a relatively large surface area allowing more than one strip to be harvested for large wounds.
Harvesting the graft: Harvesting a STSG requires some type of knife to cut a thin layer of skin. Whether using an electric/compressed air powered dermatome or a hand powered knife, it is critical to get the thickness correct. Too thick- and the donor site becomes a full thickness wound, which is difficult to heal. Too thin- and the graft will not have the important dermal elements critical for healing. In general, 0.012-0.014 inches (0.3-0.4 mm) is the proper thickness of a STSG.
Although most devices do have a way to set the thickness, often the calibration is imperfect. To get the correct thickness: the beveled end of a #10 blade should fit in the opening as demonstrated in this photo.
Clean off any soap that has been applied to the donor site and apply some type of sterile lubricant- mineral oil or rub the area with Vaseline gauze to the donor site and the knife. Have an assistant help stretch the skin on the thigh as the graft is harvested. No matter what device you have, angle it ~30-45 degrees as you gradually progress across the area.
This is the donor site after the graft is taken. Note the uniform pinpoint bleeding which shows that the thickness is correct- with dermal elements still on the thigh and no fat showing (if the entire dermis is removed you have taken a full thickness graft).
Covering the wound
After cleansing the wound, place the skin graft on top. Remember to put the dermis side down- next to the wound. The dermis side is shiny, the epidermis usually has a duller appearance. This graft was meshed with a machine, but it’s easy to cut slits in the graft with a knife or very sharp pointy scissors. Meshing the graft prevents fluid (blood or serum) collection underneath the graft, which can interfere with graft “take”. Sew or staple the graft in place and cover with a bulky dressing. Suturing the dressing in place is useful to stabilize the graft and prevent shearing, which will tear the microscopic vascular connections that must form between the wound and the graft.
Immediate Post-op care:
Graft site: Keep graft site/leg elevated at all times to prevent swelling in the surrounding tissues. Leave the dressing in place for 5-7 days. If you notice a sweet odor from the dressing, remove it sooner- this can be a sign of bacterial overgrowth.
Donor site options:
- Cover the donor site with an adhesive plastic dressing such as opsite/tegaderm. This technique is the most comfortable for patients. And it can stay in place until the area has re-epithelialized (healed). Sometimes serum will collect underneath the plastic. This is easily treated by piercing the plastic with an 18gauge needle and aspirating the fluid. Then cover the pinpoint hole with another small piece of opsite. Or,
- Apply a layer of vaseline gauze to the donor site and leave it there as it dries in place. Do not change it daily (which is very painful). It will gradually separate as the underlying area heals. Or,
- Treat it like a superficial burn and apply antibiotic ointment to the area daily.
Here is graft after the first dressing change (5 days postop).
It looks great- is “stuck” to the wound and has a pink hue from vascular ingrowth. The graft is still immature and can be sheared off if not treated carefully. Application of vaseline gauze or antibiotic ointment (or other non-stick modality) is a good dressing for the next week of so and the dressing does not need to be done daily. To prevent swelling in the area, keep the graft site elevated for at least another 2 weeks. Gentle compression helps too- gently wrap with ace wrap for example, but be sure this is not applied too tightly.
The graft at 3 weeks.
Apply gentle moisturizer to the graft daily.
Now, allow the patient to start to dangling the leg, starting with only a few minutes/hour and gradually increase the time the leg is dependent over the next few weeks. Depending on the severity of the initial injury, swelling when the leg is dependent may be a lifelong challenge for the patient. So some type of support/compression garment may be required long-term.
Corresponding chapters for further information:
Ch 12: Skin grafts