The operator is holding a Humby knife at a 45° angle while taking the STSG. A broad sterile wooden board puts pressure on and flattens the skin ahead of the knife
The most common donor site is the thigh. Wipe off any antibacterial solution that was used to prepare the site. Apply a sterile lubricant, such as mineral oil or Vaseline from a Vaseline gauze, to both the donor site and the instrument used to harvest the graft.
Technique
- 1.
Have an assistant flatten the donor site by placing tension on the skin with gauze or a wide flat object.
- 2.
Hold the Watson or Humby knife with the sharp edge at a 45° angle to the skin.
- 3.
With a back-and-forth motion, run the knife slowly over the tight skin.
- 4.
As the graft skin is being taken, look at the wound. If fat is seen, the graft is too thick. If no pinpoint areas of bleeding are seen (paprika sign), it may be too thin (Fig. 14.2).
- 5.
When enough graft has been harvested, cut the skin graft from the donor site with scissors (https://youtu.be/g_JD37smUGo).
The Paprika sign of small punctate bleeding vessels on the surface of an STSG donor site
Care of Donor Site
If local with epinephrine was not used at the start of graft harvest, apply a gauze wet with epinephrine solution (add 500 ml of saline to 1 ampule of 1:1000 epi) to the donor site to control bleeding. Treat the donor site like a superficial burn, covering it with an adherent plastic dressing or a single piece of Xeroform gauze. Remove the dressing at 24 h, leaving the Xeroform open to air. It will form an eschar that will separate over the next 2–3 weeks.
FTSG
Primary donor sites for FTSG are the mobile skin of the lower abdomen, inner upper arm, and the preauricular area where the donor site can be closed primarily. Cut through the full thickness of the skin, and when the graft is free, place the epidermis side down, draped over a gauze-covered finger, and using sharp, curved scissors remove the underlying fat. This is critical, as fat will impede vessel ingrowth and the graft will not take.
Preparation of the Skin Graft
Meshers are often unavailable. Many small cuts, made in a precise, concerted fashion will help expand the graft size. A wooden “cutting board” helps control the depth and size of the cuts
STSG being sewn in place. Suture first from the graft then to the wound edge to stabilize the graft and prevent it from displacing
Flaps
Wounds that require flap coverage are usually those with exposed bone or tendon or are in an area where a skin graft is not sturdy enough for long-term coverage, such as a pressure sore or open fracture. A flap is vascularized tissue, usually skin, fascia, muscle, or a combination. A local flap can be created if there is sufficient uninjured tissue around the wound that can be moved into the defect. When local tissue is not available, a distant flap must be created. Initially the circulation to the flap comes from the donor tissue with gradual ingrowth of vessels from the recipient wound bed. Use of distant flaps needs to take into consideration the position of the parts and comfort for the patient to prevent joint stiffness due to immobility.
General Principles
To optimize circulation and reliability of a skin flap, heed the 3:1 rule: the flap should not be longer than three times its width. Proximally based flaps are more reliable than those based on distal circulation. Delaying the flap—whereby the flap is incised and freed from all attachments except the pedicle and then loosely sutured back in place—will improve circulation by opening vessels within it. Wait 2–3 weeks to move the tissue into the defect. Close the flap defect with an STSG when a primary closure would result in undue tension.
Local Flaps
V-Y Advancement Skin Flap
A V-Y advancement skin flap is useful for covering ischial pressure sores and other wounds with lax surrounding tissues. They are commonly used for fingertip injuries when secondary healing is impractical. This flap counts on the deep tissue underlying the flap and the laxity of the surrounding tissues for its blood supply.
Procedure (Fig. 14.5)
- 1.
Determine the site where the surrounding skin laxity is greatest.
- 2.
Draw out the flap by marking the open part of the V at the widest edge of the wound, tapering gradually to a point.
- 3.
Incise the skin edges through the subcutaneous tissue down to, but not into, the underlying fascia and muscle. The flap remains attached to the deep tissues.
- 4.
Advance the flap into the wound defect.
- 5.
Close the defect at the narrow point of the V, creating the vertical or tail component of the Y.
- 6.
Suture the flap under no tension. It is better to have small gaps in the skin closure, which will eventually heal, than a tight closure, and have part of the flap necrose.
Line drawing of V-Y plasty flap for covering an ischial pressure sore. (Courtesy of Nadine Semer)
Gastrocnemius Muscle Flap
A gastrocnemius muscle flap can cover exposed bone or a fracture site involving the proximal 1/3 of the tibia or the knee. It is best to do this flap within the first couple of weeks after injury before chronic inflammation in the surrounding tissues makes it difficult to mobilize the muscle. The best strategy is to move muscle alone and place an STSG over it.
The gastrocnemius muscle is the most superficial muscle of the posterior compartment of the leg. It originates from the distal femur and joins the underlying soleus muscle forming the Achilles tendon. The blood supply is a single dominant vessel that enters the muscle proximally, near the posterior knee joint. The medial muscle is most often used because it is larger and has a better arc of rotation to reach the front of the tibia.
Procedure
- 1.
If available, use a tourniquet for the dissection.
- 2.
Remove all dead bone and other tissue. If in doubt, debride, dress, and return in 3–5 days.
- 3.
Extend the open wound onto the medial calf to visualize the underlying muscle. Try not to leave intact tight skin bridges that can compress and necrose the muscle as in (Fig. 14.6c).
- 4.
Separate the gastrocnemius muscle from the overlying skin and underlying soleus muscle. This can often be done with blunt dissection.
- 5.
In the back of the calf, the two heads of the muscle come together at the central raphe, identified by the presence of the sural nerve. Divide the muscle along the raphe, transferring 1/2 of the muscle, and divide the muscle distally from the Achilles tendon.
- 6.
Bring the muscle around to the defect. Release proximal attachments as needed for length. Usually the origin of the muscle does not require division, but if additional length is required for the muscle to rotate into the defect, divide the origin with care to protect its vascular supply.
- 7.
Once the muscle is freed, release the tourniquet and control bleeding.
- 8.
The muscle should look pink when the tourniquet is removed. If it remains dark or does not bleed, the vascular pedicle has been injured, and the muscle is unusable.
- 9.
Suture the muscle loosely to the wound edges. If it cannot completely cover the wound, cover the important structures for which the flap is being made. An STSG can cover the soft tissues now or at a second procedure in 4–5 days.
- 10.
Be sure the muscle is still pink after being sutured in place and is under no tension.
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