Scalp reconstruction
Scalp reconstruction is a surgical procedure for people with scalp defects. Scalp defects may be partial or full thickness and can be congenital or acquired. Because not all layers of the scalp are elastic and the scalp has a convex shape, the use of primary closure is limited. Sometimes the easiest way of closing the wound may not be the ideal or best way. The choice for a reconstruction depends on multiple factors, such as the defect itself, the patient characteristics and surgeon preference.
History
Indications
Surgical anatomy
The five layers of the scalp, from superficial to deep, can be easily memorized by using the mnemonic SCALP. The Skin of the scalp is the thickest of the human body, measuring up to 8 mm in thickness and contains approximately 100.000 hairs. Hair lines make scalp reconstruction difficult because the hair lines have to be respected to get a satisfying aesthetic result. The subCutis is a layer of fat, enclosed in compartments formed by rigid fibrous septa. Their inelasticy prevents bleeding vessels to collapse and retract under the skin to achieve haemostasis. All large blood vessels and nerves of the scalp are located in this layer. The next layer is the galea Aponeurotica, which separates the underlying bone and the overlying layers. The large blood vessels and nerves of the scalp don’t pierce this layer. Loose connective tissue between the periostium and the aponeurosis makes these two rigid structures easily slide over each other and contributes to skin movement. Thus, if vascular and nervous anatomy is respected, the skin, sucutaneous tissue and galea aponeurotica can be lifted off the skull with minimal bleeding, nerve damage, or chance of necrosis. This method was first described by Orticochea in 1967, but has been updated to minimize scarring. The fifth layer is the Periosteum of the skull, also referred to as pericranium. It can be separated from the skull, except near the sutures. The skull consists of an inner and outer table, with spongy bone in between known as diploë.
Vascular supply
On both sides of the scalp there are five large arteries which perfuse the scalp. Local flaps used for scalp reconstruction must contain at least one of these major arteries, to maintain a reliable blood supply. The scalp can be divided into four different vascular territories:
Lymphatic system
The frontal part of the scalp is drained to the parotid, submandibular, and deep cervical lymph nodes. The posterior part is drained to the posterior auricular and occipital lymph nodes. Malignancies of the scalp can metastasize to these lymph nodes. Brain tumors, however, tend to metastasize haematogenously.
Innervation
The scalp is innervated by motor nerves and sensory nerves. The trigeminal nerve (CNV) is one of the important cranial sensory nerves which innervates the scalp. From anterior to posterior front to back the nerves are:
Non-skin reconstruction
Dura mater reconstruction
Dural lesions should be closed to aviod CSF leakage. Also, a defect acts like a porte d'entree for micro-organisms that can cause meningitis. If fibrin glue or primary closure is not possible, patches have to be used. These are made from cadaveric dura mater, xenografts (tachosil, duragen, durepair), or synthetic grafts materials (PTFE, neuropatch). However, (vascularised) autografts (fascia lata, muscle or omentum majus) are preferred in irradiated or severely infected defects.
Bone defects
Skull defects should be closed in order to protect the brain. The occipital and temporal regions bear the most pressure while sleeping and therefore need to be reconstructed. Frontal bone defects cause a contour defect, therefore, aesthetic considerations are often taken into account to reconstruct this area. Midsagittal defects are of lower importance, as they allow only penetrating trauma. When the reconstruction cannot be performed immediately, wearing a helmet is advised. Skull deformities can result in high intracranial pressure which can cause complaints ranging from headaches to epilepsy-like seizures. Small defects can be filled with morcellized bone, which will consolidate in some weeks. Because of the anatomy of the skull, the external table can be split off the internal table and then be moved over the defect. Rib grafts (whether or not accompanied with the latissimus dorsi muscle) are suitable for larger defects and can bear pressure, but do not cover the whole defect. Implants can be used as well, but are not preferred in patients who are to be irradiated or recently have had an infection or necrosis, because of the increased risk of infection and extrusion. These implants can be factory-made out of metal (titanium), synthetic materials (PMMA, PEEK) or synthetic body-own material (Hydroxylapatite). On the pictures a reconstruction using a titanium plate is shown. The skull contour has been restored.
Soft tissue defects
Skin reconstruction
Local reconstruction
Regional reconstruction
If local reconstruction is not possible due to lack of local tissue, regional reconstruction is the next rung on the reconstructive ladder. This includes pedicled flaps as the trapezius or supraclavicular flap or tissue expansion of nearby regions. Alternatively, the Crane principle, as described by Millard in 1969, can be used. A healthy part is used to resurface the defect and when this flap takes, the skin is returned to its original site leaving the subcutaneous tissue on the defect, which then needs a split skin graft.
Skin grafts
If only skin is missing and underlying galea, muscle or connective tissue are intact, a skin graft can be used. A skin graft needs healthy, vascularised tissue beneath it to take, otherwise it will become necrotic.
Free flap
Free flaps are usually the best solution for reconstruction of large defects that cannot be closed locally and that have unfavourable wound conditions as severe infection, exposed sinuses, dura or brain tissue, CSF leakage or radiation damage. This method is the most complex of the reconstructive ladder. In scalp reconstruction free flaps have a great benefit because they are completely detached from their original location ("donor site") before transferal to the scalp which makes the inset easier compared to pedicled flaps. Another advantage is that free flaps provide a more robust vascular supply to the wound compared to pedicled flaps, controlling infection and radiation induced damage. In addition, muscle or myocutaneous free flaps provide additional bulk that obliterates empty spaces (e.g. exposed sinuses) and covers dura mater defects more than all other options, reducing postoperative wound infections and CSF leakages. Disadvantages are the complexity of the operation, leading to prolonged operation times, the need for specialised personnel, and the chance for total flap necrosis due to microvascular complications. Another challenge with the use of free flaps is to achieve an aesthetically pleasing result with good color and contour match, especially if the defect is deep.
Outcome
Aesthetic and functional
Temporal and forehead defects offer a more difficult aesthetic challenge and are best covered with a thin flap, so the aesthetic unit appears equal. Although the forehead is not an highly important aesthetic unit, color mismatch and bulkiness will draw attention quickly. Free flap reconstruction of the forehead can be bulky and color match is variable and depends on the ethnic and genetic background. Some people are not satisfied with the outcome and may experience psychological problems such as low self-confidence or even depression. Sometimes a second operation is needed to improve skin color. Overgrafting the skin with skin grafts from the scalp can improve color match.
Complications
Post-operative complications can be devided into donor-site and recipient-site problems. Donor-site complications include wound infection, hematoma, and seroma. Recipient-site complications are (total or partial) flap necrosis, wound infection, dehiscence, hematoma or skin graft failure. To avoid major bleedings or sensibility disorders, the anatomy of the scalp has to be respected. It makes a great difference if the incision is made parallel to the bloodvessel or right through it. Because of the high flow, scalp injuries can lead to serious bleedings. The cut vessels have the potential to retract into the fat so it is difficult to stop the bleeder.
References
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