Soft tissue wounds in the scalp are a common occurrence after trauma or resection of a malignancy. The reconstructive surgeon should strive to use the simplest reconstructive technique while optimizing aesthetic outcomes. In general, large defects with infection, previous irradiation (or require postoperative radiation), or with calvarial defects usually require reconstruction with vascularized tissue (ie, microvascular free tissue transfer). Smaller defects greater than 3 cm that are not amenable to primary closure can be treated with local flap reconstruction. In all cases, the reconstruction method will need be tailored to the patient’s health status, desires, and aesthetic considerations.
Key points
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Knowledge of the scalp soft tissue layers and neurovasculature are integral in understanding anatomic limitations/considerations and reconstruction planning.
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The goal of scalp reconstruction is to provide durable soft tissue coverage that restores normal contours and appearance of hair-bearing areas.
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The reconstruction modality is determined by wound location, size, depth, presence of calvarial defects, previous or planned radiation, chronic infections, prior surgeries, and need for oncologic surveillance.
Introduction
Scalp defects secondary to trauma and oncologic resections pose challenges to reconstructive surgeons not only due to the size, depth, location, and configuration of the wound but also because of hair pattern and presence of concomitant injuries (eg, cranial fractures, closed head injuries), prior surgeries, and/or previous radiation therapy. , In traumatic scalp wounds, the mechanism of injuries can vary from falls and assaults to burns and hair entrapment in industrial machines. Similarly, the extent of scalp injuries can vary from simple lacerations to complex avulsions or defects. In addition to soft tissues, calvarial defects from oncologic resections may also be present, and these defects are usually readily visible and can be disfiguring, which can cause social and psychological stress, thereby negatively affecting quality of life.
One of the first documented experiences in the management of scalp injuries was in the late 1600s by Augustin Belloste. Since that time, the management and the means for reconstruction of scalp injuries have progressed significantly to address both appropriate soft tissue coverage and also optimizing aesthetic results. However, despite these advancements, methods for scalp reconstruction can still be imperfect and provide suboptimal results, which is largely driven by anatomic factors and difficulty replicating and/or replacing hair-bearing areas. Thus careful preoperative planning and discussions must be had with the patient to counsel on both complications such as soft tissue necrosis, scar complications, alopecia, and skin pigmentation and/or texture changes, in addition to the expectations for aesthetic outcomes. The surgeon’s surgical armamentarium should be well equipped with up-to-date management strategies and surgical techniques for different types of scalp defects. The purpose of this review is to discuss different surgical strategies to address various scalp defects.
Anatomy
Soft Tissues
The scalp consists of 5 distinct tissue layers and is commonly remembered by the mnemonic: SCALP ( S kin, sub C utaneous layer, A poneurotic (galea) layer, L oose areolar tissue, P ericranium) ( Fig. 1 ). The outermost layer is the skin (ie, epidermis and dermis), which is generally thicker than most other areas of skin. The thickness ranges from 3 to 8 mm and will depend on the density of hair: the densest areas have the thickest skin, and the less dense or alopecic areas have the thinnest. Hair follicles, sebaceous glands, and sweat glands are found in this layer. The second layer is the subcutaneous layer where the extensive complex network of blood vessels, lymphatics, and nerves reside. There are also fibrous septa that partition the fat into small compartments. The aponeurotic layer (eg, galea aponeurotica) is also referred to as the epicranial aponeurosis. The galea is a durable fibrous aponeurosis that is resistant to stretching and is densely adherent to the subcutaneous tissues. This fibrous layer spans between the insertions of the frontalis and occipitalis muscles, and laterally toward the temporal fascia, and is considered the “strength layer.” The fourth layer is the loose areolar tissue layer, which is also known as the subgaleal compartment or innominate fascia. As the name implies, this layer is composed of filmy loose areolar tissue and is mostly avascular; however, emissary veins are contained within this layer. This layer is important because not only does it provide scalp mobility but it is amenable to surgical dissection without disrupting blood flow to the skin, thus allowing for large flaps to be safely raised. The last layer is the pericranium, which is similar to the galea in structure; however, it is very thin and located directly over the skull. ,
Vascular Anatomy
The primary blood supply for the scalp is derived from both internal and external carotid arteries and travels within the subcutaneous layer ( Fig. 2 ). The blood supply can be described as a centripetally distributed system where larger vessels are found in the periphery and then branch medially and centrally leading to an extensive collateralized vascular system. These arteries are found in the deep layers of the dermis and are adherent to the dermis. The scalp has been traditionally divided into 4 distinct vascular territories: the anterior, lateral, posterior, and posterolateral territory. The anterior territory is supplied by the supraorbital and supratrochlear arteries. The lateral territory is the largest of the territories and is supplied by the superficial temporal artery. The posterior territory is divided by the nuchal line into a cephalad and caudal portion. The cephalad area is supplied by the occipital arteries, and the caudal area is supplied by perforating branches from the trapezius and splenius capitis muscles. The posterolateral territory is the smallest territory and is supplied by the posterior auricular artery.
Nerve Anatomy
The sensory innervation of the scalp also has a centripetal distribution and is located within the subcutaneous layer (see Fig. 2 ). The sensation in the anterior and lateral scalp is provided by branches of the trigeminal nerve (supraorbital, zygomaticotemporal, and auriculotemporal nerves). Posteriorly, sensation is provided by branches of the second and third cervical spinal nerves (greater occipital, lesser occipital, and third occipital nerves). ,
Aesthetic Units
Although there are defined anatomic areas of the scalp, which are the occipital, vertex, parietal, and temporal areas, the distribution of hair-bearing scalp is highly variable within the population despite the consistent underlying soft tissue layers especially among men. Despite the variable areas of hair distribution, the scalp is considered to be a singular aesthetic unit. However, when planning for scalp reconstruction, the scalp should be differentiated into the hair-bearing scalp and the non–hair-bearing scalp to optimize aesthetic outcomes.
Reconstruction principles
Tissue Selection
The goal of soft tissue reconstruction is to provide coverage that is similar in appearance and function, which is encapsulated by the adage: “replace like with like.” Thus, the scalp would be the ideal tissue for reconstructing its own defects. However, the scalp is limited by the distinct set of tissue layers, relative immobility, and the hair-bearing pattern of the area. For these reasons, reconstructing large defects by using the surrounding scalp is often not possible, especially in a single procedure. If nonscalp soft tissues are used for reconstruction, then this may in turn lead to alopecic areas and/or distortion of the normal hairline. Although there may be competing desires from the patient to focus on the aesthetic outcome during their initial reconstruction, the immediate goal should be to provide adequate durable coverage first. Aesthetic outcomes to restore normalcy are important but may only be achieved in staged procedures such as hair transplantation or tissue expansion.
Wound Characteristics and Cause
The underlying cause and characteristics of the scalp wound will help guide the reconstruction strategy. The wound evaluation should include the location, size, and depth (ie, involving pericranium, calvarium, dura, etc.) and what adjacent structures may be involved (eg, hairline, eyebrows, etc.). In addition, the quality of the surrounding tissue should also be evaluated. Generally, small- to medium-sized shallow defects with an intact calvarium that have not been previously irradiated, operated on, or are chronically infected are amenable to local flaps. Larger, deeper defects with the presence of these factors are more prone to wound complications and would be better served with vascularized pedicled flaps or free-flap reconstructions. ,
Patient Preference/Goals
Ultimately the reconstruction plan will depend on patient’s reconstructive needs, preferences, and comorbidities. In counseling the patient, all of these factors should be taken into account and guide the conversation about different options. For example, reconstruction for a patient undergoing a palliative tumor resection will differ from a young healthy trauma patient with an otherwise disfiguring scalp defect. As it is with the rest of medicine, patient care must be individualized and tailored to each patient’s needs and circumstances.
Reconstruction techniques
Primary Closure
The preferred and simplest technique in wound management is primary closure: its simplicity and the approximation of similar tissues will achieve the most natural aesthetic results. Specifically, primary closure in the scalp allows the approximation of hair-bearing areas to minimize irregular alopecic areas and allow for restoration of normal anatomy. However, primary closure is often possible in defects smaller than 3 cm and in tissues that have not been chronically infected, operated on, or have had previous radiation therapy, and often wide undermining is necessary. Traumatic scalp lacerations are excellent situations in which primary closure can be pursued. Avulsions without significant tissue loss are also candidates for primary closure after debridement of devitalized tissues due to the complex collateralized vascular system of the scalp. Defects resulting from oncologic resection and/or radiation are generally suboptimal candidates for primary closure, given the larger size and surrounding fibrosis.
Approximating the fibrous galea layer helps with offsetting the tension superficially and limits postoperative alopecia. If the galea mobilization is not adequate despite wide undermining, galeal-releasing incisions can be performed perpendicular to the line of wound tension. However, caution must be used so as not to cause iatrogenic injury to the vasculature that lies directly superficial to the galea. , If the galea is violated, then closure should be performed in layers when possible.
Delayed primary closure is possible with the use of continuous external tissue expanders such as DermaClose (SYNOVIS Micro Companies Alliance, Birmingham, AL). The device, which is applied directly onto the scalp, expands the skin on the subcutaneous planes around the wound in the span of 1 to 2 weeks until the edges are brought close enough together for primary closure ( Fig. 3 ).
Secondary Intention
Secondary intention is the oldest technique of wound healing, recorded in Mesopotamian clay tablets from 2500 BC . Secondary intention involves an open wound (with healthy, viable tissue base) to heal from the bottom to top by the formation of granulation tissue. It has become an increasingly prevalent option for treatment of large traumatic wounds since the advent of the vacuum-assisted closure (VAC) device. Traditionally, this technique has often been reserved for patients who may be high-risk surgical candidates or patients with grossly contaminated wounds that are at high risk of infection , ; however, secondary intention offers certain advantages over other methods of wound closure—minimal to no additional incisions or operative procedures, no additional anesthesia, no need for tissue harvest from a donor site, and reliable wound healing in a properly managed wound.
Although the healing process may take weeks to months, the overall success rate has been found to be greater than 80% among a variety of postsurgical wounds. Secondary intention can be used anywhere on the scalp and has been shown to be an effective means of wound healing with an added benefit of better postoperative tumor surveillance in the oncologic resection population. , The healed area will be alopecic; however, because of wound contraction the size of the alopecic area will be smaller. When discussing healing by secondary intention with patients, additional considerations should also be given to the physical and psychological ramifications of this technique, particularly among young patients for whom the open wound is more debilitating and who are more prone to thickened scars due to less skin laxity. ,
Skin Grafts
Skin grafts are a useful reconstructive option for certain scalp defects. In contrast to secondary intention, skin grafts are an expedient and simple method that forgoes the need for long-term wound care at the expense of skin graft harvesting and operative risks. In lesions that are too large for primary closure, skin grafts serve as either a definitive or a temporary measure provided there is an adequate wound bed. , However, split-thickness skin grafts often result in suboptimal cosmetic results due to differences in pigmentation, texture, and thickness from the surrounding tissues. The grafted surface is usually shiny, immobile, prone to ulceration, and alopecic. , For this reason, parietal, temporal, and occipital wound sites are more amenable to skin grafting, as these areas are better camouflaged by surrounding hair. In theory, full-thickness skin grafts are more akin to the appearance and texture of normal skin and offer better protection from trauma and radiation with reduced hypopigmentation and secondary contraction. ,
A major limiting factor in skin grafting is the availability of vascularized healing bed. Exposed muscle (eg, temporalis) provides a healthy foundation, and the pericranium alone is also sufficient for graft incorporation. In cases where the pericranium is absent, particularly in oncologic resections, the surgeon can create a healing bed by drilling into or removing most of the calvarial cortex to expose the bleeding diploic space and allow for the formation of granulation tissue (usually with series of VAC dressing changes) for delayed grafting. The use of commercially available regenerative medicine products (eg, collagen/chondroitin matrix, amniotic allograft membrane, fetal bovine dermal/urinary bladder matrix, etc.) have provided more treatment options for the reconstructive surgeons for wound healing/preparation for skin grafting. Skin grafting should be avoided in radiated areas or where radiation is planned, as successful skin grafting requires well-vascularized wound surface. ,
Local Flaps
Local flaps provide excellent reconstruction options for wounds not amenable to primary closure. They have similar texture, appearance, and ability to bear hair, which in turn helps optimize aesthetic results. When evaluating for local flaps, several key factors must be considered to properly tailor the flap to the patient’s needs. These factors can be broadly categorized into defect, patient, and flap factors.
Defect factors include location and wound characteristics such as size, exposed structures, cause, and prior radiation treatment. , Local flap reconstruction in large defects, which is often described as an area greater than 50 cm 2 , have been associated with significantly higher risk of flap-related complications; however, the suggested upper limit for defect size vary between studies. , In addition, Steiner and colleagues reported that there is an increased likelihood that concomitant skin grafting will be necessary to cover the donor defect, as the size of the defect grows beyond 39.2 cm 2 . Other factors that would make local flap reconstruction a suboptimal choice would be the presence of bony defects, previous surgical interventions or radiation therapy, and/or plans for adjuvant radiation. Reconstructive surgeons should be an integral part of multidisciplinary discussions for patients undergoing oncologic resection because the reconstructive options may need to be tailored based on plans for adjuvant chemotherapy or radiation.
Patient factors to be considered are health/functional status to determine the operative candidacy, skin quality, and smoking status. Irradiated tissues or chronically scarred tissues are suboptimal for local flap reconstruction, as they confer a high risk of flap complications, in which case free-flap reconstruction should be pursued. In addition, older patients may have a higher chance of success due to skin loosening over time, which would provide more laxity for local flaps. Smokers are at increased risk for complications when undergoing scalp reconstruction, thus tobacco cessation should be pursued before elective reconstruction. ,
Flap factors to be considered are the vascular supply for the flap. Given the extensive collateralized vasculature of the scalp, local flaps usually do not have significant perfusion issues and often do not need to be constructed based on a specific named artery. Larger flaps can be designed based on the advantages of an axial-based perfusion. In small series, local scalp flaps created with a named artery via preoperative ultrasound identification have demonstrated favorable aesthetic contouring and hairline formation. Local flap reconstruction techniques in scalp defects use the principles of advancement, transposition, and rotation. Advancement and transposition techniques are limited by the flexibility of the galea and the thick poorly distensible nature of the scalp skin. Rotational flaps are well suited for scalp reconstruction; however, longer flap lengths are typically required to compensate for the curvature of the skull. , Several well-described local flap techniques make use of either one or more of these principles such as the O-Z closure, V-Y advancement flap, Juri flaps, Orticochea flaps, and the pinwheel technique ( Fig. 4 ). , Choice of technique will ultimately vary by patient and surgeon preference, but the underlying principles will remain the same: provide safe durable coverage with the best aesthetic result.
