Congenital scalp/calvarial defects classification



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Delayed Closure of Sutures

  • Large metopic sutures and anterior fontanelle are seen in Aperts

    • spontaneous ossification of the widely patent metopic suture contiguous with an enlarged anterior fontanelle usually occurs within the first 2 years of life.

  • Cleidocranial dysplasia

    • AD, a generalized skeletal dysplasia.

    • frontal bossing

    • hypertelorism

    • hypoplasia or aplasia of the clavicles

    • short stature

    • supernumerary teeth

    • limb defects – excessive length of metacarpus (extra epiphyses) but short middle and distal phalanges especially of the second and fifth fingers

    • coronal synostosis with delayed closure of the anterior fontanelle and midline sutures


Amniotics bands

  • 1 in 1243 to 1 in 15,000 live births.

  • Up to 33 percent of cases show involvement of the craniofacial regio

  • suspect in clefts not topographically associated with embryonic fusion lines

  • most facial clefting occurs with the swallowing of bands during the fifth month of gestation.

  • If the central nervous system is involved, as with a major skull defect, the insult is usually associated with a rupture of the amnion within the first 6 weeksof life.

  • Clefting of the cranium may result in neural defects including meningocele, meningoencephalocele, and anencephaly.


Growing skull fracture

  • widely diastatic skull fracture associated with dural laceration and extrusion of cerebral tissue outside the calvaria beneath an unbroken scalp

  • Growing skull fractures can develop when dural and arachnoid tears remain unrepaired

  • herniated cerebral tissue within the fracture defect is the defining feature of growing skull fracture.

  • Expanding calvarial defects in patients reoperated for craniosynostosis have been reported - believed to be the result of unrecognized dural tears sustained during the initial operation

  • May be associated with progressive neurological symptoms if left untreated.

  • Prompt reduction of the cerebral hernia followed by dural repair will prevent a growing skull fracture




Reconstruction
Scalp defects
Non-surgical

  • common trend throughout the literature is advocacy for nonsurgical treatment. Success in treatment for aplasia cutis have been reported in case reports using:

  1. 1% silver sulfadiazine cream dressing

  2. bacitracin zinc ointment and circumferential dressings alone.

  3. Antibiotic ointments and Op-Site (Smith & Nephew, Largo, Fla.)

  • If nonsurgical management is undertaken, it is essential that the wound remains moist to prevent eschar formation over the membranous tissue

  • As an eschar begins to separate, the chance of a hemorrhagic event, whether minor or major, increases dramatically.


Surgical

  1. direct closure

    • suitable for Class IA defects

  2. SSG

    • Advantages include immediacy of coverage and possibility of greater surface area coverage than what might be achievable with local flaps.

    • May be a poor choice in patients with underlying bone defects:

      1. no case of bony ingrowth has been documented after wound closure using a skin graft.

      2. if bony reconstruction is attempted at a later time, the graft has to be separated from the brain and sagittal sinus, potentiating a massive intraoperative hemorrhage.

  3. rotational or transposition flaps from unaffected scalp

    • Class IB defects

    • Concerns regarding the reliability of such flaps have been raised. Some believe that an abnormal vascularity of the adjacent skin exists, as evidenced by the frequent presence of grossly dilated veins and that much of the adjacent skin was previously granulation tissue that epithelized in utero and therefore lacks an axial vascular pattern.

  4. tissue expansion

    • some advocate skin graft and delay the expansion until the child is older than 1 year of age to avoid skull deformity (even then is said to be reversible)



Calvarial defects

Nonoperative





  • Observation

    • infant dura has a critical osteoprogenitor function that dissipates with aging - when intact dura is present in a young child, clinical experience has documented the dura's capability of regenerating calvarial defects which is loss if replaced by adult dura

    • Because normal dura seems to be necessary for calvarial reossification, the probability of complete, spontaneous bone healing in children with open defects and exposed brain is low.

    • The likelihood that an open skull with abnormal dura will completely close, regardless of age, significantly decreases with increasing diameter of the defect.

    • Thus, frequent physical and, if warranted, radiographic evaluations are needed to determine the osteogenic biology of each individual patient.

    • If bone regeneration is not evident, bony reconstruction is warranted

Surgical


  • Indicated if

  1. exposed dura/sinus at risk of bleeding

  2. large defects not closing over time

  • autogenous versus alloplastic

  • Autologous options

      1. periosteal flap

        • transposition of Periosteum over the defect has been successful in closing calvarial defects

        • Periosteum has been demonstrated to have cell populations including osteoprogenitor cells, which are capable of bone formation

      2. Bone graft

        • axial skeletal bone grafts from either rib or ilium donor sites.

        • a split-rib cranioplasty has been described for total reconstruction of skull

        • reported disadvantage of an osseous cranioplasty is the variable amount of graft resorption, often as high as 40 percent.

        • In older patients, splitting of the inner and outer tables allows for increases up to 350 percent in the size of the originally harvested calvaria

        • autogenous calvaria can also be used for skull reconstruction by means of an expansion technique This procedure is one in which multiple interdigitating osteotomies are made so that the cranium can be expanded on itself. This allows for a more homogenous distribution of cranial bone over a larger surface area, with greater ease in the shaping and modeling of cranial bone. May be combined with lyophilized bone power

Alloplastic options



  • either alone or in conjunction with autogenous grafts.

  • ideal bone substitute would have the ability to regenerate and produce a mixture of cancellous and cortical bone, allow for revascularization, and grow with the patient

  1. Hydroxyapatite

        • the most widely used bone substitute.

        • It is the major mineral component of bone, and is porous, highly biocompatible, and resistant to biodegradation

        • Studies have shown hydroxyapatite to be osteoconductive rather than osteoinductive

        • Available forms include block, injectable, and granular hydroxyapatite cement. A newer product consists of tetracalcium phosphate and dicalcium phosphate dihydrate which, when combined, form a microporous hydroxyapatite

        • Disadvantages include a brittle nature and low tensile strength.

        • No apparent interference by the implant on craniofacial growth

  1. Acrylics (methylmethacrylate)

        • advantage of in situ modeling with a spatula when soft or a bur when hardened, allowing for a more precise match to the defect.

        • generates a significant hyperthermic reaction during polymerization that may lead to cerebral injury

        • Disadvantages include the lack of porosity, less biocompatibility than hydroxyapatite, a tendency to dislodge and/or fracture, and problems with late infection requiring implant removal.

      1. Medpor (porous polyethylene)

        • stereolithographic techniques for custom-made implants


Recommendations
Class II Defects

  • For defects between 2 and 5 cm (class IIB), an autogenous cranioplasty is performed. If the child is younger than 5 years of age, this is performed as an interdigitating calvarial expansion operation. If the child is older than 5 years, autogenous split-thickness calvarial grafts are used (provided that sufficient maturation of the diploic space and development of the trilaminar skull is documented on computed tomographic scan). If split-thickness calvarial grafting is not possible, interdigitating calvarial expansion with or without distant site autogenous bone grafting (rib or ilium) is used. The age at which surgical intervention is performed is selected on the basis of consideration of the balance between allowing for a period of osseous opportunity, to observe whether the defect will begin to close spontaneously, and the desirability of exploiting the osteogenic properties of the immature dura in areas that will become donor-site defects. Whether a cranial expansion or split-thickness calvarial cranioplasty is performed, the calvarial grafts are secured with biodegradable plates and screws.




  • For defects smaller than 2 cm (class IIA), nonoperative management is recommended, given the high rates of spontaneous defect ossification. A follow-up head computed tomographic scan is obtained at approximately 1 year of age to assess residual defect size.




  • Defects larger than 5 cm in diameter (class IIC) may be treated with either autogenous or alloplastic cranioplasty, depending on the percentage of involved skull. If more than 50 percent of normal calvaria is intact, an interdigitating cranial expansion is performed for osseous coverage. However, if less than 50 percent of the normal skull remains, there may not be enough available autologous calvaria for coverage. In this situation, a custom fabricated alloplastic implant cranioplasty is performed.


Class III Defects

  • in cases of exposed meninges and/or brain, delay can lead to significant morbidity and mortality given the documented incidence of bleeding and infection. As such, early, if not immediate, coverage is often require

  • If the defect size of both the scalp and the skull is less than 2 cm (class IIIA), the scalp defect is closed primarily. The osseous defect is managed nonsurgically and observed for spontaneous ossification

  • For defects of both the scalp and skull that are between 2 and 5 cm (class IIIB), treatment consists of scalp closure with either excision and primary closure or closure by rotation of a local flap. Treatment of the bony defects in this size range is based on age, with children younger than 5 years receiving an interdigitated cranial expansion and those older than 5 years receiving a split-thickness calvarial graft.

  • For defects of both the scalp and skull that are greater than 5 cm in diameter (class IIIC), the approach outlined above (class IIC) is applied. Early coverage of the brain is the first priority in this situation. We recommend coverage by rotating a composite scalp flap (skin, subcutaneous tissue, and galea) to cover the soft-tissue defect. The pericranium over the flap donor site is covered with a split-thickness skin graft. The calvarial reconstruction is then addressed with either an interdigitated calvarial expansion (for defects involving less than 50 percent of the calvaria) or a custom fabricated alloplastic cranioplasty implant (for defects involving greater than 50 percent of the calvaria), as described for the class II reconstructions. The reconstruction then is completed at approximately 1 year of age, with removal of the skin graft and resurfacing of the surgical defect with hair-bearing scalp or glabrous skin, as anatomically indicated, to eliminate unsightly scarring and alopecia.
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