CC
A 16-year-old male presents for combined surgical and orthodontic correction of his facial asymmetry and apertognathia. He describes his chief complaint as an inability to bring his anterior dentition into occlusion, which makes eating difficult. He is also concerned about his facial asymmetry and weak-appearing chin.
When orthognathic surgery is considered, it is important always to assess the patient’s chief complaint as it relates to function and esthetics to ensure that any planned surgical intervention adequately addresses the patient’s concerns and to fully inform the patient about any anticipated changes in facial appearance as a result of the surgery.
HPI
The patient has a significant past medical history of bilateral retinoblastoma, which was treated at 5 months of age by enucleation of the left globe and radiotherapy of the right orbit. Significant facial asymmetry caused by radiotherapy-induced growth disturbance is readily evident. The patient had been in orthodontic therapy for 15 months before this consultation. He is primarily concerned about masticatory dysfunction. His deformity consists of anterior open bite (AOB) and facial asymmetry with diminished right periorbital volume and enophthalmos. His first premolar teeth have been removed in preparation for the surgery. He is missing teeth #1 and #32, and teeth #16 and #17 remain impacted.
PMHX/PSHS/medications/allergies/SH/FH
Bilateral retinoblastoma, with the left globe treated by enucleation and the right eye with radiotherapy at 5 months of age. No history of recurrence. At present, the patient denies any regular use of medications and has no drug allergies.
Examination
General. No acute distress, well nourished, and appropriate mental capacity.
Head. Growth status complete. Orbital prosthesis present in left orbit. The right periorbital region is diminished in volume, with the presence of enophthalmos and decreased projection of the right zygomatic buttress and arch.
Further maxillofacial examination proceeded as follows.
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Skeletal aspects
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Significant facial asymmetry is present.
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Midpoints
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The upper dental midline is 5 mm to the patient’s right.
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The lower dental midline is 2 mm to the patient’s right.
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The chin point is 4 mm to the patient’s right.
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Vertical: The occlusal plane is canted upward to the patient’s right.
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Profile: convex
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Chin: retrusive. Signs of mentalis strain are evident (indicative of muscular activity to assist with lip closure or competency).
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Nose: large
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Nasolabial angle: obtuse (normal is 100 degrees ± 10 degrees)
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Throat length: short
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Lips
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The upper lip is in normal anteroposterior position.
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The lower lip is protrusive.
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Incompetent, open 11 mm.
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The upper lip is thin.
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The lower lip is thick and protrusive.
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Dentition
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AOB malocclusion with contact only on posterior first and second molars bilaterally. Complete orthodontic appliances are in place.
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Upper incisor to lip line at repose is 5 mm.
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Upper incisor to lip line smiling is 11 mm with 0 mm of gingival display.
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Lower incisor show to lip line at repose is 3 mm of exposed.
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Lower incisor show to lip line at smiling is 10 mm exposed.
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No centric relation or centric occlusion discrepancy noted.
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No macroglossia noted.
Imaging
Although this chapter focuses on the use of three-dimensional (3D), computer-assisted surgical simulation software in conjunction with a preoperative computed tomography (CT) scan, panoramic and cephalometric radiographs continue to be used by some clinicians to assist in preoperative surgical planning. Practitioners may choose to obtain these radiographs separately; however, they are easily generated from CT or cone-beam CT (CBCT) data set manipulation via a number of software programs.
For the current patient, recent panoramic and cephalometric radiographs ( Fig. 64.1 A and B) were available at the time of consultation and revealed impacted teeth #16 and #17, in addition to considerable facial asymmetry. The vertical ramus height of the mandible was measured as 1 cm shorter on the right than on the left (disruption of the growth center of the mandible secondary to radiotherapy or to altered growth of the functional matrix of the face on the right side), and cephalometrics revealed obvious apertognathia, as noted on clinical examination ( Fig. 64.1 C). CT imaging was obtained after the initial consultation, which correlated with the radiographic findings and provided additional information regarding the hypoplastic nature of the right facial skeleton and its contributions to the facial asymmetry. The CT imaging protocol used for virtual surgical planning (VSP) is extremely important, and the surgeon must adhere to it closely for accuracy of procedures and splint fabrication.
Labs
The patient’s current medical status and planned surgical interventions did not require preoperative laboratory assessment, although some patients may require specific labs based on their medical history.
Assessment
Marked facial asymmetry secondary to radiation therapy for retinoblastoma, occlusal dysfunction as a result of underlying hypoplastic right mandibular body, AOB, and significant occlusal cant.
Correction of this type of asymmetric deformity requires combined surgical and orthodontic treatments. Complete correction of the asymmetry also likely requires other surgical intervention to augment or modify the underlying skeletal anatomy or adjunctive soft tissue procedures to improve local deficiencies. Definitive correction of the soft tissue structures of the face is likely best done in a staged fashion after the underlying bony foundational reconstruction is complete and has had some time to heal. Surgical intervention requires osteotomies of both the maxilla and mandible, preceded by precise preoperative planning, to achieve both functional and improved esthetic correction.
Surgical planning has historically used two-dimensional radiographs and mounted model surgery to simulate the planned surgical movements. Acrylic surgical splints (intermediate or final) were then fabricated to assist with positioning of the jaws intraoperatively. This technique has a history of documented success. The current use of CT and VSP software in a preoperative workup provides precision and detail of movements in three dimensions not previously available. This technology has been readily available since 2010 and continues to be further refined, thereby continually enhancing outcomes. By evaluating maxillary and mandibular movements in relation to the entire facial skeleton in a virtual 3D model, the surgeon can make more accurate decisions and predictions, and precise splints can then be printed for the case, thereby eliminating the need for any traditional model surgery.
Treatment
Isolated cases of apertognathia historically have been treated with a Le Fort I osteotomy involving posterior impaction and some maxillary advancement. Alternatively, isolated mandibular surgery consisting of bilateral sagittal split ramus osteotomies and counterclockwise rotation of the mandible to close the AOB is possible, assuming rigid fixation is used. The current patient has a combination of apertognathia and significant facial asymmetry, which makes any attempts at isolated treatment of the maxilla and mandible futile. Facial asymmetry cases require a great deal of preoperative planning to ensure that the deformity is corrected appropriately.
Virtual surgical planning software, marketed and used by various modeling companies, can assist the surgeon in making important, complex decisions. The planning software is complicated to learn and is time-consuming as well. These cases are typically planned in conjunction with an engineer who is facile with the manipulation of the software. This combined with the surgeon’s expertise allows for rapid virtual planning of the case and predictable results. To use such planning, the surgeon must obtain specific preliminary records. This includes:
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Clinical assessment measurements (i.e., midline discrepancies, facial asymmetries, tooth-to-lip position)
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Clinical photographs (frontal, lateral, repose, smiling, and occlusal images)
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CT or CBCT scan with the patient in centric relation (seated condyles)
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Intraoral scans (e.g., iTero, 3-Shape) of the dental arches independently and with the patient in centric occlusion to demonstrate the preoperative bite registration
These records are then uploaded to the modeling company along with a tentative plan for the surgical procedure which would include the anticipated procedures and movements. A web-based meeting is then arranged to plan the surgical case in detail with the engineer. This meeting allows the surgeon and the modeling team to make precise movements of the maxillomandibular complex by visualizing bony osteotomies, condylar position, and overlaps and gaps between bony segments. Changes in roll, pitch, and yaw of the segments can be adjusted, thereby creating the most favorable and stable osseous position of all segments. Such capabilities are particularly invaluable in facial asymmetry cases.
In the current patient, a Le Fort I osteotomy and bilateral sagittal split ramus osteotomy were used to correct the apertognathia and facial asymmetry ( Fig. 64.2 A). The Le Fort procedure was performed first; an intermediate splint was used to level the maxillary occlusal plane and align the dental midline with the facial midline. The maxilla was impacted 7.3 mm posteriorly and 3.5 mm anteriorly, with 6.1 mm of impaction on the left and 0.9 mm on the right. After rigid fixation of the maxilla, bilateral sagittal split ramus osteotomies were performed, bringing the dentition into final occlusion using the final splint. This case demonstrates the quality and precision of movements afforded by the use of preoperative planning software. As shown in Fig. 64.2 B, the maxillary dental midline is coincident with the facial midline; however, the maxillary yaw is shifted significantly to the patient’s left. Fig. 64.2 C illustrates the yaw correction of the maxilla, which places the maxilla in the most ideal yaw, pitch, and roll position. After the maxillary movements have been planned, the mandible is brought into the final occlusion based on the preoperative intraoral scans provided to the modeling company. Visualization of the mandibular osteotomies and the gaps naturally created by the asymmetric movements of the mandible are easily reviewed and examined ( Fig. 64.2 D). As noted, the overlapping aspects of the proximal and distal segments are less than ideal ( Fig. 64.2 E), and fixation in this position would require a great deal of adjustment to the proximal segment or result in flaring of the right mandibular condyle. However, with the maxilla and mandible locked in final occlusion, mild adjustments are made to the yaw of the entire maxillomandibular complex, allowing for a more favorable overlap of the mandibular proximal and distal segments ( Fig. 64.2 F). Clearly, selected areas of bony reduction or modification or the placement of bone shims in certain areas may be necessary to allow for ideal positioning of the proximal and distal segments of the mandible in cases such as this. Postoperative panoramic and lateral cephalometric radiographs reveal stable fixation and the correction of skeletal asymmetries, in addition to the enhanced chin position as predicted by the use of VSP technology ( Fig. 64.3 ). Presently, most surgeons would obtain a postoperative CT or CBCT to assess outcomes and forgo standard radiograph assessment.
