Neurosurgery

Fig. 26.7. Illustration demonstrating frontal-orbital advancement, with 180° rotation of the frontal bone flaps and fixation of the orbital bar, with resorbable plates in the area of bone graft.

advocate performing it before 6 months of age, in order to avoid compensatory changes in the skull, while others advocate between 6 and 12 months of age, in order to accomplish more effective fixation and avoid high re-operation rates. If, however, there is evidence of increased intracranial pressure or pansynostosis, sutural release is mandated in the neonatal period as soon as possible.

Mid-facial advancement may be performed alone through an extracranial LeFort III osteotomy or simultaneously with a frontal bone advancement as a monobloc unit. The timing of these procedures depends upon the facial morphology that results after primary fronto-orbital advancement. If the exophthal-mos is severe or nasal obstruction is present, then a LeFort III advancement can be performed in early childhood (4-6 years of age). In most instances, it is performed in mid-childhood (7-14 years of age). If the supraorbital position is not acceptable with exorbitism or there is hypertelorism, then a monobloc or a staged fronto-orbital advancement performed in the early childhood years (4-6 years of age) followed by a LeFort III osteotomy in the mid-childhood years may be performed.

The fixation of osseous segments in monobloc and LeFort III procedures originally utilized wires and then rigid metallic plate fixation. These methods carried the risk of migration or extrusion of the fixation device as the child grew. Presently, distraction osteogenesis is performed, which utilizes a temporarily placed metallic fixation device that is activated daily (Fig. 26.8). This avoids the need for harvesting bone grafts and improves post-operative stability by slowly expanding the soft tissues, which reduces the potential for relapse. These devices will most likely be completely resorbable in the future, obviating the need to remove the device in a subsequent surgery, following an adequate consolidation phase.

The monobloc fronto-facial advancement can be used to correct severe orbital/mid-facial retrusion (Fig. 26.9). This procedure, however, carries the risks of prolonged surgery and higher infection rates, especially when performed with a midline osteotomy (bipartition) due to an opening between the nasal cavity and cranial vault. As a result, the monobloc is con-traindicated in those patients with a shunt or with frontal sinus development. The advantage of a bipartition, which can be performed in a

Fig. 26.8. Illustration demonstrating LeFort III advancement of mid-face, which can be fixated with either resorbable plates and bone grafts in advanced position or can be advanced over several weeks, with internal metallic distractor (also demonstrated).
Fig. 26.9. Illustration demonstrating monobloc advancement of mid-face and frontal bone, performed through an intracranial approach.

LeFort III as well, is that it allows for correction of hypertelorism and maxillary restriction simultaneously. Some believe that the risk of infection and its inability to address the occlusion are reasons to stage fronto-orbital advancement and a LeFort III advancement in early and mid-childhood, respectively, or to perform them simultaneously.

The LeFort III procedure utilizes a transverse osteotomy at the nasal root below the level of the cranial base, in order to avoid the risks of a monobloc. The level of the cranial base can be assessed pre-operatively by a coronal-cut CT scan. If the cranial base is low, leading to the risk of osteotomizing into the cranial base, then an intracranial approach through a fronto-orbital craniotomy will allow for visualization of the cranial base during this transverse osteotomy. The intracranial approach also provides access to the lateral and superior orbital walls for osteotomies, if necessary. As mentioned earlier, a bipartition may be performed in a LeFort III procedure as well.

The occlusal relationship cannot be precisely controlled with the monobloc or LeFort III procedures. In addition, the patients are usually in a mixed dentition, with additional growth of the jaws remaining at the time of these procedures. As a result, orthognathic surgery, including a LeFort I and often a mandibular osteotomy, is performed during adolescence after skeletal maturity is complete. This is performed in conjunction with pre-surgical orthopedics/orthodontics for precise occlusal alignment. It may require segmental osteotomies to correct transverse and/or vertical disproportions, as well as residual cleft palate abnormalities, if present.

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