Principles of Facial Reconstruction (eBook)

3   Scalp

Summary

This chapter focuses on the principles and anatomy that are pertinent and important with respect to reconstruction of scalp defects. Specific consideration is given to undermining and layered closure as well as the use of tissue expanders for larger defects.

Keywords: scalp, tissue expanders, rotation flap, layered closure, galea, advancement flap

The scalp is composed of five layers, recalled by the mnemonic SCALP: skin, sub cutaneous fat, galea aponeurosis, loose connective tissue, and pericranium. The galea is a strong, fibrous sheet with firm connections (via the occipitalis muscle) to the nuchal ridge posteriorly and the frontalis muscle anteriorly. The tight attachments existing between the scalp, skin and the galea significantly reduce tissue mobility in the subcutaneous planes.

Undermining in the subcutaneous plane is difficult due to extreme vascularity and it risks injury to the hair follicles. Scalp flaps are easily undermined just beneath the galea, because the space is occupied by loose connective tissue with few blood vessels. Even wide undermining at this level, however, leads to disappointingly small improvements in flap tension. Subpericranial elevation is also avascular, but it yields even less tissue laxity.

Blood supply is arranged in a radial pattern from the following five arteries: supratrochlear, supraorbital, superficial temporal, postauricular, and occipital. Abundant blood supply allows for the design of numerous small random pattern flaps. Large transposition flaps should incorporate one of the previously named arteries.

Hair emerges from the scalp at an angle. The direction in which the hair is angled varies with the scalp region. Scalp incisions should be beveled parallel to the hair follicles to preserve them (see Fig. 2.1). In areas where hair shaft direction varies, care is needed to align the incision correctly. In the pretrichal region, incisions should be beveled opposite the direction of hair follicles to allow hair regrowth through the incision.

Scalp wounds should be closed in two layers to prevent scar widening and loss of hair. Buried 2–0 or 3–0 permanent or long-lasting absorbable sutures are placed in the galea, using care to not injure hair follicles. The skin is closed with 4–0 or 5–0 monofilament sutures or staples. When the wound is under tension, galea sutures are placed ~1 cm back from the edges to prevent tissue tearing. In addition, galea-releasing incisions parallel to the blood supply of the flap, just through the galea, and spaced 1 to 2 cm apart will further decrease wound-closing tension.

Thick and inelastic, the scalp is resistant to such standard techniques as advancement and transposition flaps. Rotation flaps are the main reconstructive technique for scalp defects. Large defects are usually treated by tissue expansion, along with rotation or advancement flaps, as dictated by the location of the defect.

The scalp should be palpated to establish the directions of greatest mobility and the flaps designed accordingly. Scalp tissues that are closed under tension tend to stretch back up 30 to 50% of the distance closed. This problem can be reduced by using galea sutures at the time of closure.

In the typical scalp, defects <3 to 5 cm in size can be closed with either unilateral or bilateral rotation flaps (Fig. 3.1). Bilateral flaps are usually selected to distribute closing tension over as much area as possible. Unilateral flaps are used primarily for defects adjacent to the hairline. The length of the sides of the rotation flap (or flaps) is typically four to six times the defect diameter to allow adequate rotation. One can design either a single or double rotation flap of maximal length, then cut back only partially to determine the actual length required (Fig. 3.2). Wide undermining in the subgaleal layer must be performed to facilitate scalp movement. Hair provides camouflage for what may seem to be inordinately long incisions for relatively small defects. The defect site is closed first. Then the long limbs are closed, using the technique of halving to distribute tension. The two limbs of the bilateral rotation flaps do not have to be equal in length, and usually are not, unless the defect is located exactly in the center of the scalp. In the situation where bilateral rotation flaps are insufficient to close a defect, one or more additional flaps may be created to convert to a “pinwheel” flap design.

Small standing cones (“dog ears”) commonly form during flap closure and will usually resolve with healing. Large standing cones can be removed using the standard Burow technique. Rotation flaps used for repair after excision of benign areas (e.g., burn scars or nevi) can be designed, incised, and rotated over the lesion prior to its removal. If necessary, a partial excision can be performed and a second stage planned.

If complete closure is not possible and pericranium is present, the wound can be left to heal by secondary intention, or a skin graft can be placed to complete coverage. Split-thickness skin grafts (STSGs) can be placed directly on the pericranium or on the diploic space (after drilling to this surface) with excellent viability. Skin grafts placed on bare bone will frequently fail, resulting in an extended healing period and increased chances of osteomyelitis. Once healed, the skin graft can be serially excised, or tissue expansion can be employed to achieve complete scalp coverage.

Tissue expansion is the technique of choice for defects that cannot be closed with rotation flaps (Fig. 3.3). If possible, tissue expansion should be accomplished prior to removal of the primary lesion (Fig. 3.4).

If the lesion has been previously resected, then the defect can be allowed to heal by secondary intention or closed with an STSG until tissue expansion can be completed. In the case of a rectangular tissue expander, the expander base should be roughly 2.5 times the size of the defect to be closed. When using a round expander, the diameter of the expander should be 2.5 times the size of the defect. The expander shape should be chosen depending on what type of flap is to be used.

Although rotation flaps are most commonly used in scalp reconstruction, advancement flaps are sometimes preferred after tissue expansion because of the availability of the additional tissue. The shape and position of the tissue expander should be carefully planned to provide the appropriate amount of expanded tissue in the proper location. The preferred expander is placed between the galea and the pericranium, via the smallest incision that will accommodate it. The incision is placed at the junction of the defect and the normal skin, except in the case of the previously placed skin graft that is to be serially excised. In this case, the tissue expander is placed through an incision as far as possible from the skin graft to prevent dehiscence of the graft–skin junction. The injection portal is placed at least 6 cm from the balloon through the same incision. The skin and subcutaneous layers of the incision are closed with permanent sutures.

At the time of placement, 25 to 50 mL of saline should be placed in the expander to obliterate dead space and prevent hematoma formation. Expander inflation is started 2 weeks after the primary surgery and is executed on a weekly or twice-weekly basis. Each expansion session is continued until there is too much local discomfort to continue or until the tissue overlying the expander blanches. Saline is then withdrawn until the discomfort is tolerable or the blanching disappears. Expansion is continued until the circumference of the dome formed is two to three times that of the defect.

At the time of tissue expander removal, the initial incision is usually made at the junction of the defect and the normal skin on the side of the tissue expander. The flap is advanced into position prior to skin graft removal to ensure closure of the defect site. Further releasing incisions are made, as necessary. The capsule underlying the expanded tissue may be left in place or removed for better contour. The wound is then closed in layers.

Suggested Reading

Baker SR, Swanson NA. Tissue expansion of the head and neck: indications, technique, and complications. Arch Otolaryngol Head Neck Surg 1990;116(10):1147–1153

Bardach J. Scalp reconstruction using local flaps and free skin grafts. In: Local Flaps and Free Skin Grafts. St. Louis: Mosby Year Book; 1992:193–211

Jurkiewicz MJ, Hill HL. Open wounds of the scalp: an account of methods of repair. J Trauma 1981;21(9):769–778

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