Last Updated: September 27, 2018
A clear understanding of the basic principles of wound healing, scalp vascular anatomy, atraumatic tissue handling, closure, and reconstruction techniques are necessary for planning scalp incisions.
The process of wound healing can be divided into inflammatory, proliferative, and maturation phases. Polymorphonuclear leukocytes migrate first, followed by macrophages and mononuclear leukocytes. The protective epidermal layer is replenished within 48 hours of wound closure as the marginal basal cells migrate to cover the defect within the incision line.
Fibroblasts migrate for about 4 to 5 days and deposit disorganized collagen. The closed wound regains about 20% of its original tensile strength after 3 weeks, and about 60-70% by 6 weeks, and 80% by one year. Radiation inhibits the ability of fibroblasts to migrate and deposit collagen.
Based on the above mechanisms, it is therefore important to cut the skin perpendicular to its surface and avoid oblique incisions or scything of the adjacent dermis. During closure, the suture needle should enter perpendicular to the surface of the skin with the sutures placed at an equal distance and depth from the edges of the incision. These maneuvers prevent inversion of the skin edges and an unequal surface, which would inhibit efficient and effective epithelialization. “Unequal bites” lead to poor healing and cosmetically undesirable scars.
Careful approximation of the wound edges is also important for re-epithelialization. During wound closure, the sutures should be placed under gentle tension to approximate the incision edges and avoid their over-inversion. Significant tension on the sutures leads to strangulation of the wound edges and results in tissue ischemia that inhibits wound healing.
Planning the Incision
The most important factor in minimizing wound healing complications and breakdown is thoughtful planning of the first incision. Malignant tumors often undergo radiation and chemotherapy, and this places the wound at risk of dehiscence and subsequent infection.
Benign tumors may require repeat operations for recurrence, and the outline of the incision during the initial operation can affect the healing outcome of the incision during subsequent reoperations. The recurrence may be along the edges of the initial resection cavity or slightly beyond them; an initial linear incision provides the most flexible strategy to extend the initial incision if needed for subsequent operations.
Several principles are crucial in planning scalp incisions and promoting timely wound healing. The most appropriate incision outline should:
- provide ample vascular support to the incision site for efficient healing (the width of the flap should be wider than its height);
- mobilize a scalp flap that interferes minimally with the intradural operative trajectory;
- anticipate the possible need for salvage opportunities to support wound healing if breakdown and infection occur; and
- appear cosmetically acceptable.
In general, linear incisions parallel to the routes of major feeding arteries (i.e. superficial temporal and occipital arteries) are well-vascularized (transect least number of branching arteries) and offer numerous options for salvage maneuvers to promote wound healing in the event of wound breakdown. U-incisions are less likely to offer these advantages and are more time consuming to open and close.
Scalp incisions can play an important role in reaching the desirable operative trajectory. For example, a poorly planned incision can mobilize a thick suboccipital muscle in the wrong direction to dramatically increase the working distance of the surgeon through the retromastoid corridor.
The need to remove the patient’s hair to decrease the risk of postoperative infection is controversial, and there is no Class I evidence that supports the need to shave the patient’s entire head before surgery. I advocate clipping the hair instead of shaving, and I clip a strip of hair around the incision.
The following images demonstrate the patterns of scalp incisions for first time or repeat operations.
The following photographs demonstrate other variations of supratentorial cranial incisions and their associated patient positions.
I use multifilament braided sutures (Vicryl 3-0, Ethicon, Cincinnati, OH) to approximate the galea. This suture is absorbed by hydrolysis in 50-70 days. I use clear Monocryl 3-0 sutures (a synthetic absorbable suture by Ethicon) with a simple continuous (running) technique to close the skin layer. The half-life of this suture is 7-14 days. This suture avoids the need for staple removal and is also ideal for pediatric cases. For patients with infected wounds and traumatic cases with open lacerations, I avoid multifilament sutures and use monofilament sutures to approximate the galea and skin.
Embolization of scalp vessels during treatment of meningiomas or superficial arteriovenous fistulas can compromise vascular support to the scalp. Moreover, prior radiation treatments can lead to serious complications during wound healing. Such circumstances require the involvement of our plastic surgery colleagues and alternative incisions and reconstruction techniques to ensure vascularized pedicles for scalp flaps. For example, if the superficial temporal artery is absent, a reverse U-shaped incision should be avoided when completing a subtemporal craniotomy; linear alternatives would allow preservation of supplementary feeding vessels from the supraorbital/supratrochlear and posterior auricular/occipital arteries.
Ideally, the incision should not be directly over the osteotomies and hardware to avoid the risk of wound breakdown directly over the bone flap and foreign bodies.
Pearls and Pitfalls
- Linear incisions heal more effectively and provide more flexibility for alternative incisions during repeat operations.
- The base of the flap should be wider than its height and major scalp arteries should be spared during incision planning.
- During wound closure, the sutures should be placed under gentle tension in order to approximate the edges of the incision and avoid over-inversion of these edges, minimizing ischemic complications caused by strangulation of tissues.
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