Computer-assisted surgical planning congenital differences & anomalies: Syndromic craniosynostosis – (subcranial) Le Fort III and Le Fort III/I

Introduction

Various conditions, congenital and acquired, can limit midface growth resulting in midface hypoplasia. Midface hypoplasia may be a result of developmental maxillary dysplasia, skeletal and dental class III malocclusion, and hard palate narrowing. This can lead to airway obstruction, mastication and speech difficulties, and an altered aesthetic facial cascade. ^, Affected conditions include, but are not limited to, patients with cleft lip and palate, congenital skeletal dysplasia, and patients who suffer from craniofacial dysostosis. ^, ^, Treatment of midface hypoplasia mainly consists of restoring occlusion and optimizing the maxillary position. This can often be achieved at the Le Fort I level alone with maxillary advancement plus/minus rotation of the Le Fort I segment. The treatment of the global midface hypoplasia dysmorphology depends on the extent of hypoplasia and/or deficiency of individual structures of the midface. Therefore, a detailed and thoughtful analysis of the brow position, orbit, periorbital structures, occlusion, and airway is crucial to decide the best treatment option. If the patient has concurrent maxillofacial asymmetries from residual cranial vault dysplasia along with midface deficiency, additional surgical management for these conditions include monobloc, monobloc facial bipartition, box osteotomies, or a Le Fort III osteotomy with or without distraction. ^,

The majority of this chapter will focus on treatment of global midface hypoplasia and the use of subcranial Le Fort III and Le Fort III/I procedures, as these interventions may benefit from the use of computer-assisted design and computer-assisted manufacturing (CAD/CAM).

Clinical considerations

Evaluations

By analyzing the relative positions of the brow, orbits, periorbital structures, airway and occlusion, one can determine which structures may need corrective surgical intervention. The severity and presentation of these structures can vary greatly based on the etiology. Patients may not be bothered by or realize what structures are anomalous. They typically just want to “look better” and have their “teeth work better.” Therefore, there should be a detailed discussion of the patient’s and surgeon’s goals with this type of operation. Any surgery at the Le Fort III level requires a coronal incision, which can be stigmatizing to patients; consequently, patients will often select for a less optimal aesthetic outcome than undergo a Le Fort III surgery. Less invasive surgeries and camouflage surgeries, such as a high Le Fort I or a modified Le Fort II, are then often performed to achieve similar results. ^,

Le Fort III advancement

The indications for Le Fort III advancement are global midface hypoplasia with hypoplasia in the infraorbital region, airway obstruction secondary to midface retrusion, and skeletal and dental malocclusion. ^, An isolated Le Fort III surgery is best suited for a patient at skeletal maturity and that requires a small advancement. ^, More stable movements and better outcomes are rendered in patients that require approximately 5 mm of advancement or less at the inferior orbits due the degree of soft tissue constraints. If 6 mm or more of movement is required, a Le Fort III distraction is performed during the patient’s growth and development followed by a Le Fort I osteotomy procedure performed at the completion of skeletal growth to address malocclusion. As our practice continues to develop, fewer patients seem to benefit from a Le Fort III advancement alone. More often, a Le Fort III distraction or simultaneous Le Fort III/I is required.

Le Fort III distraction

Le Fort III distractions provide optimal management in children with global midface hypoplasia who require significant advancement ≥6 mm at the inferior orbital rims. This is commonly performed in a growing child to help correct functional impairments, such as orbital exorbitism, to improve airway obstruction, and to decrease the degree of a patient’s syndromic appearance. Given that the hardware is removed after completion of the operation, any subsequent midface surgery or orthognathic surgery can be performed. It should be noted that after an initial Le Fort III distraction, the pterygoids have been separated, which may limit future facial growth, ^, and it may be more challenging to redo these osteotomies. However, depending on the degree of the surgeon’s experience, these operations can consistently be reproduced. Although it has been described, we do not utilize CAD/CAM for distraction procedures as the vector and length of distraction may vary from preoperative plan. Custom-designed footplates, based on CAD/CAM, may be beneficial in specific patients with extremely anomalous anatomy.

Le Fort III/I

In patients with global midface hypoplasia and class III skeletal and dental malocclusion, a Le Fort III/I procedure can optimize orbital rim positioning while also addressing occlusal adjustments. The Le Fort III/I procedure is especially useful in patients with significant difference in degree of midface hypoplasia between the orbital and dentoalveolar regions. Furthermore, by moving the midface and maxilla simultaneously, less movement is required for each bony segment to reach proper alignment, and the total movement is additive. ^, The escalator effect of these movements helps create a more aesthetically pleasing cascade. It should be noted that this procedure is best carried out on patients of skeletal maturity to deter recurrence, relapse, and need for revisional surgery. ^, CAD/CAM allows surgeons to move the Le Fort III segment forward and then individually rotate or move the Le Fort I segment to restore functional occlusion as seen in our patient example and video ( ).

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