Scalp Reconstruction With Free Flaps

Finny George

Evan Matros

DEFINITION

Free tissue transfer using microsurgical techniques is considered the highest rung on the reconstructive ladder and is generally reserved for complex and/or large wounds.
Free flaps should also be considered in situations in which tissue with robust blood supply is needed to optimize healing such as in patients with prior radiotherapy treatment or underlying cranioplasty.
Unlike adjacent tissue transfer in the form of a scalp flap, any free flap will introduce non-hair-bearing tissue into the region.

ANATOMY¹

The principal blood supply to the scalp is through the supraorbital, supratrochlear, superficial temporal, occipital, and posterior auricular vessels.
The most commonly used recipient vessels for free tissue transfer to the scalp are the superficial temporal vessels.
Alternatively, the occipital vessels are large in size and have been described.
If regional vessels are unavailable, a vein graft may be necessary to reach the neck vessels.

PATHOGENESIS

Defects of the scalp often result from trauma, malignancy, or congenital disease. Occasionally, chronic wounds develop after radiation therapy.
Full-thickness defects exposing the brain are especially problematic because of the risk of cerebrospinal fluid leak and infection.
Calvarial reconstruction with devascularized bone flaps or foreign material also increases the risk of infection and wound healing complications.

FIG 1 • This patient had been treated with excision, Medpor cranioplasty, and adjuvant radiation for squamous cell cancer on the scalp. A. Hardware exposure necessitated definitive flap reconstruction. B. Previous rotation flaps and skin grafts can be seen.

PATIENT HISTORY AND PHYSICAL FINDINGS

Pertinent history must include information on
- Circumstances surrounding injury
- Prior treatment or operations, including failed treatments and presence of hardware or implants
- History of radiation or chemotherapy, immunosuppression, or connective tissue disorders
- History of smoking, alcohol abuse, weight loss, diabetes, or bleeding disorders
Physical examination should gather enough knowledge to prepare an accurate preoperative plan.
- Look for prior incisions or evidence of radiation damage to determine patency of recipient vessels (FIG 1).
- Previous coronal incisions may extend into the preauricular area, causing damage to the superficial temporal artery and vein.

IMAGING

Diagnostic studies are typically not needed.
In the setting of prior surgery, however, one can evaluate potential recipient vessels with Doppler studies or angiography.

SURGICAL MANAGEMENT

Preoperative Planning

Prior operative reports should be reviewed.
Risks specific to this operation should be discussed with the patient:
- Partial or complete flap loss
- Alopecia
- Need for further or revisionary surgery in addition to donor-site morbidity
The patient must be aware that he or she will require a potentially lengthy operation and hospital stay.
Patients must be informed that flap compromise requires urgent re-exploration, possibly the use of anticoagulants, transfusions, and the need for vein grafting from different portions of the body.
Long procedures in the decubitus or prone position are at risk for development of pressure sores even despite proper positioning and padding.
Preoperative antibiotics are administered.
Temporary markings should be placed with ideal lighting and exposure to delineate areas of laxity, hair growth patterns, and prior surgical incisions.
A Doppler probe can be used to identify arterial supply of the remaining scalp flap and recipient vessels.
In addition, during the planning phase, consider the following:
- The estimated pedicle length necessary to reach the defect.
- Backup plans for recipient vessels should be anticipated in case of size discrepancy or other potential issues. This may include the use of vein grafts.
In choosing a free flap, considerations should include thickness of tissues to be replaced, surface area for coverage, desire for full-thickness skin-to-skin closure (as opposed to a skin graft, which may take an extended period to epithelialize).² A variety of flaps are available (Table 1).

Table 1 Free Flap Graft Sources

Pros	Cons
Anterolateral thigh
Thin and pliable in patients with suitable body habitus Supine position for harvest Primary donor-site closure possible for smaller defects Potential for two-team surgery Chimeric flaps can provide both skin and muscle coverage if necessary. Vascularized fascia can be harvested with the flap and inset below the native skin flap, providing a “second layer” closure. This is helpful in patients with radiation-damaged scalp skin that may result in delayed healing with a simple skin-to-skin closure.	Large thigh donor-site defects may require skin grafting. Unpredictable pedicle length
Latissimus dorsi
Broad muscle with large surface area. The flap can be placed beneath the remaining scalp skin in patients with a history of irradiation. This “two-layer” repair decreases the risk of wound complications that may arise from dehiscence of the flap to the native scalp skin that may occur when skin-to-skin closure is obtained with skin flaps. This flap is considered by many as the optimal choice for large scalp defects because of its surface area.³ Long, large-caliber pedicle Can be harvested with serratus anterior muscle for even greater surface area Can be harvested as a myocutaneous flap to provide durable coverage in the posterior scalp for total scalp reconstruction	Lateral repositioning Lengthy scar with high incidence of donor-site seroma formation May require scalp skin grafting, thus limiting potential for hair reconstruction
Rectus abdominis myocutaneous flaps (vertical or transverse rectus flaps)
Large skin paddle Long, large-caliber pedicle Potential for two-team surgery	Donor-site hernia Can be too thick relative to the scalp, making insetting difficult Limited potential for “two-layer” closure Ischemic complications in large flaps that extend across the midline