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Scalp reconstruction

Surgical anatomy

Before performing scalp reconstruction, it is important to have detailed knowledge on the distinct anatomical features of the scalp. A mnemonic for its layers, from superficial to deep, is SCALP. The skin of the scalp is the thickest of the human body, measuring between 3 mm (vertex) to 8 mm (occiput) in thickness and contains approximately 100.000 hairs in individual patterns. Hair lines make scalp reconstruction more difficult than e.g. lateral chest defects because the hair patterns have to be respected to get a satisfying aesthetic result A frequently used credo in scalp surgery is 'replace tissue like tissue' to optimize esthetic results.

The subcutis consists of a layer of fat, contained in compartments formed by rigid fibrous septa. The rigidness of these septa make scalp bleeds so vigorous; their inelasticy prevents the bleeding vessels to collapse and retract under the skin to achieve haemostasis. Surgically important, all large blood vessels and nerves of the scalp are located in this layer .

The next layer is the galea aponeurotica, which is the aponeurosis of the frontal and the occipital muscles. This layer is poorly perfused by perforators arising from the cranium and in fact it acts like a barrier between the underlying bone and the overlying layers. This implies that if the scalp is cut beneath the galea aponeurotica, it can be lifted off the bone without any bleeding of importance

Loose connective tissue between the periostium and the aponeurosis makes these two rigid structures slide over each other and thus contributes to skin movement. The loose tissue lends itself to easy dissection, so undermining it means overlying layers can be moved in big flaps. Thus, if vascular and nervous anatomy is respected, the scalp can be lifted off the cranium with minimal bleeding, nerve damage, or chance of necrosis. This method was first described by Orticochea in 1967, but has been updated to make less scarring. ()

The fifth layer is the periostium of the scalp, also referred to as pericranium. It can be separated from the calvarium, except near the sutures. The calvarium consists of an inner and outer table, with spongy bone in between known as diploë .

Vascular supply

On both sides there are five large arteries which perfuse the scalp. From anterior to posterior these are the supratrochlear supraorbital and superficial temporal arteries which branch off the internal carotid artery, and the posterior auricular and occipital arteries which arise from the external carotid artery. Local flaps used for scalp reconstruction must contain at least one of these major arteries, which travel in the subcutaneous tissue, to maintain a reliable blood supply.

The scalp can be divided into four different vascular territories:

• Anterior: supratrochlear artery and supraorbital artery
• Lateral: superficial temporal artery
• Posterior: occipital artery
• Posterolateral: posterior auricular artery

  

  Arteries of the scalp

Veins of the scalp

Lymphatic system of the scalp

Nerves of the scalp

The veins anastomose frequently with each other and enter the diploic veins of the skull bones and the dural sinuses. The scalp veins accompany the arteries and have similar names:

• Supratrochlear vein and supraorbital vein
• Superficial temporal vein
• Posterior auricular vein
• Occipital vein

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.

Innervation

The scalp is innervated by two types of nerves: motor nerves and sensory nerves. The trigeminal nerve (CNV) is one of the important cranial nerves which innervates the scalp. From anterior to posterior the nerves are:

• Supratrochlear nerve and Supraorbital nerve
• Zygomaticotemporal nerve
• Auriculotemporal nerve
• Lesser occipital nerve
• Greater occipital nerve

Indications

Scalp reconstruction indications range from medical issues to cosmetics. Medical indications are defects, caused by surgical excision or trauma.emedicine.medscape.com/article/1828962-overview Congenital deformities of the skull may be corrected by surgery as well. Active infections are a contraindication for surgery, as they might cause bacteriaemia and have a negative influence on the healing process.

Dura mater reconstruction

Dural lesions should be closed to aviod CSF leakage. Also, it 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. Autograft vascularised patches are i.e. fascia lata and omentum majus. Other options are non-vascularised patches, such as allografts made from cadaveric dura mater, xenografts (tachosil, duragen, durepair) or synthetic grafts (Goretec, neuropatch). Vascularised patches are the first choice ìn irradiated regions.

Bone defects

Calvarial bone defects should be closed in order to protect the brain. The occipital and temporal regions bear the most pressure while sleeping. Midsagittal defects are of lower importance, as the allow only penetrating trauma.

Bone defects can result in complaints ranging from headaches to epilepsy-like seizures and aesthetic concerns. Morcellized bone can be used for small skull defects and the tabula externa or rib grafts are suitable for larger defects. Synthetic or metal plates can be used as well, but are contraindicated in patients who are to be irradiated or recently have had an infection or necrosis. Rib grafts in combination with the latissimus dorsi muscle can be used to cover large defects and provide stuctural support.

Soft tissue defects

If the periostium or underlying muscles (frontalis, occipitalis, temporalis) are intact, secondary closure by granulation can be an option. A quicker, esthetically more pleasing result are split skin grafts or full-thickness skin grafts.

When the periostium and the muscles are not intact, then the naked bone has to be covered with vascularised tissue. Only then the bone and periostium can heal.

Boven een kritische grens of bij ongunstige factoren (infectie, blootliggende sinus, dura of brein, status na RT, littekens van eerdere mislukte ingrepen, liquor lekkage) met een regionale of vrije lap

Reconstruction

Local reconstruction

If the defect does not exceed 3 cm in diameter, it can be closed primarily. If this is not possible without tension, the surrounding galea can be undermined to achieve greater mobility . Different kinds of plasties are possible: V-Y, Z, pinwheel flaps, Orticochea flaps, advancement flaps, rotation flaps.

Another option is secondary healing, but this is cosmetically inferior to primary closure in hair bearing areas, but the scar tissue makes the defect look smaller because of contraction. When the scalp cannot be closed primary and local reconstruction is needed because of hair lines, tissue expansion is possible.

Primary closure can cause deformation of esthetic units, such as the eyebrows. Secondary healing is a slow process, which makes it prone to infection. Tissue expansion gives good long term outcome, but is invalidating on the short term.

Regional reconstruction

When local reconstruction is not possible due to lack of local available tissue, regional reconstruction may be an option. This includes pedicled flaps as used by The Guinea Pig Club or tissue expansion of neighbouring areas. The Crane principle can be used as well, where the defect is closed with healthy tissue by means of rotation, the donor site gets closed by granulation and eventually those two areas are switched.

Free flap

Large defects that cannot be closed primarily and where either regional reconstruction nor granulation are not preferable, free flaps are the best solution. In scalp reconstruction

Complications

With every surgery, there are all kinds of complications. By scalp reconstructions, there can be problems on the recipient-side (such as total/ partial flap necrosis, wound infections or skin graft failure) and on the donor-side (such as wound infections or skin graft failure).

To avoid major bleedings or sensibility disorders, it is necessary to have sufficient knowledge about the anatomy of the scalp. It makes a great difference if the incision is made parallel to the bloodvessel or right through it. Because the scalp is so well vascularized, there is a high flow and scalp injuries can lead to ernestly bleedings. The cut vessels also have the potential to retract into the fat so it is difficult to stop the bleeder.

Patients with full-thickness scalp wounds should undergo some type of reconstructive surgery. Wounds occurring over allografts, bone grafts, and hardware should be covered with well-vascularized local or free flaps. In situations in which healing may be compromised, microsurgical reconstruction may be the best option, particularly when the creation of broadly based, tension-free local flaps is not feasible.

References

A.prkic (talk) 17:59, 8 October 2011 (UTC)