1. The proximal segment is successfully split from the distal mandible (i.e., no “bad” split) on each side (right and left).

2. The distal mandible is placed in the preferred occlusion and tightly held in intermaxillary fixation (IMF). Unless the natural occlusion between the upper and lower teeth is precise (i.e., without centric relation–centric occlusion slides), the IMF should be maintained with the use of an accurate prefabricated acrylic splint.

3. Each proximal segment is positioned with the condyle seated in the terminal hinge position. Each proximal segment is then secured to the distal segment with the use of either passively placed bicortical screws or monocortical screws and plates. This is accomplished without torquing or overseating the proximal segment. The following conditions should be present:

4. With the release of IMF, the mandible is put through the range of motion to confirm the adequate stability of the skeletal fixation across the ramus osteotomy site on each side.

5. The occlusion is then checked for any centric relation–centric occlusion discrepancies or other causes of malocclusion. If a discrepancy is seen, each proximal segment must be released of its fixation and then again repositioned until the planned, stable, and reproducible occlusion is achieved (i.e., Steps 1 through 5 are repeated, as needed).

Condylar Resorption after Orthognathic Surgery

Although it is rare, idiopathic condylar resorption may present after orthognathic surgery (maxillary or mandibular osteotomies), routine orthodontic treatment, or routine dental procedures; it may also occur spontaneously and not in association with any specific form of treatment (see Chapter 36).^{12,117,118,143,144,148,159,202,212,237,278,327} Condylar resorption is usually bilateral, symmetric, and seen in young females who are between 15 and 35 years old. Although no agreed upon etiology has been delineated for idiopathic condylar resorption, hormonal and autoimmune causes are suspected (see Chapter 36). Unilateral condylar resorption in association with compressive forces may also be seen after the excessive use of elastics in an attempt to overcome residual malocclusion. The clinical setting may involve heavy elastic use either as part of an orthodontic camouflage approach to avoid surgery (Fig. 17-5) or after orthognathic procedures that did not achieve the desired occlusion. In either case, heavy compressive forces on the condyle may result in temporomandibular joint symptoms followed by condylar resorption with a loss of condylar (posterior facial) height.

Continued Growth of the Mandible after Orthognathic Surgery

Under normal conditions, the mandible is the last bone in the craniofacial skeleton to complete growth. In general, mandibular growth should be complete between the ages of 14 and 16 years in girls and between the ages of 16 and 18 years in boys. Chronologic and skeletal age will vary from individual to individual, and mandibular growth in men may continue beyond the age of 18 years, but this is uncommon. Jaw growth in girls is usually complete within 2 years after the onset of regular menses. The completion of jaw growth may be assessed in the following ways: 1) via the growth-plate analysis of a hand and wrist radiograph 2) via the analysis of a quantitative condylar head bone scan in comparison to a lumbar vertebra (L2) 3) via the analysis of the mandibular length with the use of serial lateral cephalometric radiographs 4) via the analysis of cervical vertebral maturation with the use of serial lateral cephalometric radiographs 5) via the assessment of serial dental models in centric relation or 6) via the assessment of serial occlusal photographs taken in centric relation.*

Mandibular growth in individuals with micrognathia is generally complete at an earlier age than it is among normal “average” mandibular growers. Alternatively, the cessation of lower jaw growth in individuals with true mandibular excess may occur later than it does in average individuals (Figs. 17-6 and 17-7) (see Chapter 20); this is especially true for individuals with asymmetric mandibular excess growth anomalies (see Chapter 22). Alternatively, the individual with a typical Class II long face growth pattern (i.e., vertical maxillary excess combined with mandibular deficiency) can be assumed to have a normal mandibular growth vector without a tendency for late development (see Chapter 21). I believe that, if the long face patient’s chronic nasal obstruction problem is simultaneously managed at the time of orthognathic surgery (i.e., septoplasty, inferior turbinate reduction, the widening of a tight nasal aperture, and the lowering of the nasal floor), further pathologic vertical growth is also likely to be arrested (see Chapter 10).

Ramus Remodeling and Malunion after Sagittal Split Ramus Osteotomy

With the use of rigid internal fixation (e.g., bicortical screws or plates and screws), the remodeling and malunion of the ramus osteotomy site is believed to be an uncommon cause of relapse.109,115,179,206,236,248,302,324 Although infrequent, infection that has led to sequestration (e.g., of the buccal shelf of the proximal segment) and malunion has been reported. In most clinical settings, there is little evidence to support the concept of late relapse at the ramus osteotomy site after satisfactory initial healing has occurred (by approximately 5 weeks). However, limited bone contact or inadequate fixation of the bony segments may cause initial fibrous union followed by malunion and resulting malocclusion. This would be documented as morphologic change in the mandibular angle (i.e., clockwise rotation of the distal segment) in the presence of unchanged condylar morphology (i.e., no ongoing erosion of the condylar head). There would also be measurable change in either the mandibular length (i.e., as measured from the condyle to the pogonion) or the sella–nasion–B-point angle documented during the analysis of the serial cephalometric radiographs after surgery.

Proffit and colleagues do make a case for ramus remodeling with relapse after mandibular set-back when managing a Class III skeletal pattern.²⁴⁸ These authors believe that, when the orthognathic procedure for the management of a Class III skeletal pattern is a mandibular set-back only versus a two-jaw surgery (i.e., with the primary movement being maxillary advancement in combination with only minor mandibular adjustment), then relapse at the ramus osteotomy site is a common occurrence. In a recent clinical study, Proffit and colleagues confirmed that—despite improvements in surgical fixation techniques (i.e., rigid fixation versus intraosseous wires and IMF)—when mandibular set-back only procedures are carried out for a Class III malocclusion, skeletal instability is often significant. They confirmed better long-term skeletal and occlusal stability when two-jaw surgery is performed for the management of Class III skeletal patterns (i.e., maxillary advancement with limited mandibular set-back).²⁵¹

1. After Le Fort I down-fracture osteotomy, full mobilization of the maxilla and the segments (if segmentation has been carried out) is accomplished before the placement of fixation.

2. An accurate prefabricated acrylic splint is secured to the maxillary occlusal surfaces. The splint stabilizes the new maxillary arch form (i.e., the arch width and the curve of Spee) when segmental osteotomies are carried out.

3. After the securing of the splint to the maxillary dentition, IMF is applied to establish the new horizontal position of the maxilla; the dental midline (yaw orientation); the preferred maxillary plane orientation (pitch orientation); and any cant correction (roll orientation) required.

4. With the condyles seated in the terminal hinge position and IMF established via the prefabricated splint, the maxillomandibular complex is rotated until the desired vertical position of the maxilla is achieved.

5. There must be adequate bone contact across the osteotomy site after the maxilla is stabilized with plate and screw fixation into the desired position. If not, an interpositional graft of sufficient quality should be placed and secured (see Chapters 15 and 18). Without adequate bone contact across the osteotomy site, fibrous union may occur (see Chapter 16). Another possibility is that of initial bony union with relapse (i.e., malunion) occurring as full healing proceeds during the 6 to 12 months after surgery, thereby resulting in late malocclusion.

6. Adequate plate and screw stabilization of the maxilla generally requires the placement of titanium fixation at each pyriform rim and each zygomatic buttress (see Fig. 15-26). When interpositional grafts are required, additional titanium fixation is placed from the superior maxilla and extended across the graft to the dentate segment (see Fig. 15-29, A, B, and C). Additional plate and screw fixation may also be placed horizontally across any interdental osteotomies, if needed.

7. With release of the IMF, the occlusion is checked as the mandible is rotated (opened and closed) with the condyles seated in the terminal hinge position. The occlusion must evenly contact and fit passively into the splint. If not, the plate and screw fixation across the Le Fort I osteotomy is released. Any bony interference is then identified and removed. The maxilla is again repositioned and the fixation reapplied (i.e., repeat Steps 4 through 7) until the planned occlusion is achieved and confirmed.

1. Inadequate skeletal mobilization. When significant widening of the posterior maxilla is required, bilateral (rather than unilateral) parasagittal osteotomies will assist with the tension-free placement of the segments into the splint (see Chapter 15).

2. Inadequate splint strength. The use of a non-flexible splint (e.g., a reinforced U-shaped acrylic splint, transpalatal support) is essential to maintain the arch width during initial healing (see Chapter 13).

3. Inadequate soft-tissue mobilization. After the completion of segmental osteotomies, the stretching of the palatal soft tissues through the down-fracture (i.e., the use of a spreader forceps) improves the tension-free placement of the segments into the splint.

4. Inadequate postsurgical care. After the splint is removed (i.e., 5 weeks after surgery), the seamless transfer of responsibility from the surgeon to the orthodontist for ongoing maxillary arch form maintenance is essential. The effective use of orthodontic mechanics is generally needed for at least 6 months to retain the arch form. (This is described later in this chapter.)