The layers of the scalp are easily remembered by the mnemonic SCALP:
S (skin) is the thickest in the body, measuring between 3-8 mm,
C (subcutaneous tissue)- The vessels, lymphatics, and nerves course through the subcutaneous layer just superficial to the galea.
A (aponeurotic layer) --The galeal aponeurosis, the strength layer of the scalp, is contiguous with the paired frontalis muscles anteriorly, the paired occipitalis muscles posteriorly, and the temporoparietal fascia laterally,
L (loose areolar tissue) is also known as the subgaleal fascia, the innominate fascia, and the subaponeurotic plane. The loose areolar tissue of this plane allow for scalp mobility. Scalp avulsions routinely occur through this layer, leaviing pericranium intact.
P (pericranium) is tightly adherent to the skull and should be left intact in scalp reconstruction to allow for "back-grafting" of the donor site or for a means of alternative recontruction in the event of a failed local tissue transfer.
- Primary Closure--For small defects this is often the best option. Defects less than 3 cm in diameter can be closed primarily, but this varies depending on location. If primary closure is selected, any defect in the galea should be closed first with buried resorbable sutures, and skin edges should be reapproximated using suture or staples.
- Skin Grafting and Tissue Expansion--Placing split-thickness skin grafts can provide a quick and effective means of defect closure. Skin grafts require an adequately vascularized wound bed and are not successful if applied directly to exposed bone. Intact pericranium is typically sufficient to support a skin graft. Tissue expansion usually provides ample tissue with preservation of scalp sensation, color, thickness, and hair; however, it ultimately requires a minimum of 2 operative procedures. Patients should understand beforehand that this requires a commitment of at least 1-2 months
- Local Flaps--Local flaps are the workhorses of small to midsized scalp reconstructions. These flaps consist of skin, subcutaneous tissue, and galea, although occasionally small superficial defects may be adequately reconstructed using a flap elevated in the subcutaneous plane. Any local flap is best raised over named arterial systems. Raising a large flap and then covering the donor site with a skin graft is probably safest. One should avoid suture lines in areas where prosthetic material might be exposed.
- Free-tissue transfers--Before the advent of free-tissue transfers, closure of scalp defects covering more than 15-20% of the scalp was essentially impossible with a single procedure. Free flaps provide for single-procedure closure of large defects or complicated wounds involving scalp and bone. They can also provide improved wound healing in the setting of radiation or infection. However, they are time-consuming and expensive, and they all involve at least some donor site morbidity. Therefore, they should be reserved for appropriate situations when local flaps, skin grafting, or healing by secondary intent is not an option.
- Vacuum assisted Closure Device (VAC)--A vacuum assisted closure device has been used for large defects over the dura to promote the growth of granulation tissue. This tissue is then covered with a skin graft. The device works by applying uniform subatmospheric pressure to the wound, allowing it to develop a better blood supply, decreased bacterial counts, and robust granulation tissue.
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