Mandibular micrognathia and vertical maxillary excess correction with combination LeFort I and inverted L osteotomies

A 34-year-old woman with mandibular micrognathia, vertical maxillary excess, and an open bite characterized by a “bird-face” deformity was treated with orthodontics combined with LeFort I and bilateral inverted L osteotomies. The total treatment time was 16 months. Her occlusion and facial appearance were significantly improved by a surgical-orthodontic plan. This case report presents the discussion of a unique and complex orthognathic surgical case and the myriad of orthodontic and surgical considerations that it involved.

Highlights

  • The patient had Class II malocclusion with mandibular micrognathia and diminutive condyles (Discrepancy Index score: 63).

  • The patient fit the phenotype of “bird-face” deformity.

  • The patient required the less known inverted L osteotomies to increase posterior face height and correct Class II malocclusion.

  • The patient was in braces for 16 months.

  • Her occlusion, smile esthetics, and profile were greatly improved (American Board of Orthodontics Cast-Radiograph Evaluation: 13).

“Bird-face” deformity (Vogelgesicht) has been used to describe a dentofacial abnormality that is characterized by a Class II skeletal malocclusion with severe mandibular retrognathism, short posterior facial height, diminutive condyle-ramus complex, microgenia, and a steep mandibular plane angle with or without an anterior open bite. The exact etiology of this dentoskeletal deformity is often unknown but can be caused by idiopathic arthritis, reactive arthritis, condylar trauma, craniofacial microsomia, craniofacial dysostosis, idiopathic condylar resorption, or mandibular hypoplasia resulting in an underdeveloped vertical height of the posterior condyle-ramus complex with concomitant dentofacial changes. ,

Patients with a phenotypical bird-face deformity present challenges to the orthodontist and the surgeon beyond the typical Class II surgical treatment plan. Their mandibles are underdeveloped in all dimensions and often exhibit diminutive condyles and short posterior rami. This can lead to compensatory changes in development such as excessive downward growth of the maxilla and a narrow transverse dimension. This facial abnormality presents with severe overjet, a steep mandibular plane, and long lower facial third with the maxillary anterior segment continuing to passively move inferiorly, creating a vertical maxillary excess owing to a lack of opposing tooth contacts. ,

A patient presenting with a bird-face deformity requires significant advancement of the mandible and lengthening of the posterior face; therefore, the conventional bilateral split ramus osteotomy (BSSO) is unable to properly correct this skeletal deformity. This case report presents a protocol that includes orthodontic and surgical treatment with LeFort I and the lesser-known bilateral inverted L osteotomy to correct the patient’s severe Class II malocclusion, well characterized by the bird-face deformity. A functional and esthetic result was achieved.

Diagnosis and etiology

A 34-year-old woman was self-referred for an orthodontic evaluation. Her chief complaint was that her “lower jaw was too far back.” She had previously received orthodontic treatment in her late adolescence, but when she was ready for the orthognathic surgery, her family could not afford it. The patient was always aware that she would need surgery to correct her jaw relationship, but she waited until she could personally pay for the surgery. The patient presented to the orthodontic clinic with a phenotypical bird-face deformity ( Fig 1 ). Clinically, she demonstrated (1) dolichocephalic facial type, (2) convex soft-tissue profile, (3) mandibular micrognathia, (4) long lower anterior facial height, (5) vertical maxillary excess, (6) obtuse nasolabial angle, (7) short chin throat length, and (8) lip incompetence with a reverse resting lip line.

Fig 1
Pretreatment facial and intraoral composite.

Intraorally, she had a beyond full-step Class II malocclusion bilaterally at the molar and canine ( Fig 2 ). Her overjet was 20.7 mm with an open bite of 0.8 mm. She had mild crowding in the maxillary arch and moderate crowding in the mandibular arch with a mild curve of Spee. Compared with her facial midline, her maxillary midline was centered, whereas her mandibular midline was 0.5 mm to the right. Further diagnosis revealed a slight Bolton discrepancy with an anterior ratio of 82% and an overall ratio of 95% (norms 77.2% and 91.3%, respectively). This was most likely the result of mandibular excess both in the anterior and premolar areas. When smiling, the patient showed a high smile line with excessive gingival display, revealing 4 mm of contiguous gingival display. The patient also presented with a reverse resting lip line in which her upper lip measured from subnasale to stomion was shorter than her commissure height ( Fig 3 ). This led to an upward and reverse curvature to her upper lip. In our patient’s case, this reverse resting lip line and her vertical maxillary excess resulted in significant lip incompetence. It is also important to note that she presented with an absolute maxillary transverse discrepancy, which was expressed when the dental casts were advanced to a Class I relationship. This was likely because of the posterior maxilla occluding with the narrower portion of her mandibular arch, owing to the anteroposterior discrepancy.

Fig 2
Pretreatment models.

Fig 3
Normal lip length at rest. Sn , subnasale; Ls , labialis superior; St , stomion.

A clinical examination of the anatomy of her head and neck revealed that she had slight myofascial pain of her right and left masseteric musculature on palpation. Further assessment revealed no joint pain, popping, or clicking in either temporomandibular joint (TMJ). The irregular and diminutive shape of her condyles was seen on her 3-dimensional (3D) cone-beam computed tomography (CBCT) slices ( Fig 4 ). This necessitated further TMJ testing to ensure there would be a stable surgical outcome. Her oral maxillofacial surgeon ordered bone scintigraphy of her TMJs using a technetium diphosphonate (99 mTc) bone scan to ensure there was no active bony remodeling (condyle or fossa) present. Bone scintigraphy has the advantage of showing active bony changes where traditional radiography can only capture the present bony architecture. , , Results from bone scintigraphy using 99 mTc does not guarantee a stable TMJ; therefore, the process should be used as a supplemental index when looking for degenerative joint disease. This type of imaging should be combined with other radiographic and clinical findings to assure the correct clinical diagnosis. The patient’s bone scan was negative, demonstrating no active bony remodeling. Her symptomology was considered muscular in origin because of the constant need to protrude her mandible for it to function. The radiology report combined with our clinical examination deemed that the joints were stable for surgery. Although the scintigraphy and the clinical assessment were favorable, the patient was informed that she could still be at risk for joint remodeling or idiopathic condylar resorption because of her anatomic characteristics.

Fig 4
Pretreatment TMJ slices from the CBCT.

A panoramic radiograph showed no caries or other pathologies, but it also revealed several amalgam restorations on her posterior teeth and that all her third molars had been extracted ( Fig 5 ).

Fig 5
Pretreatment lateral cephalogram, tracing, and panoramic radiograph.

The lateral cephalometric analysis indicated a skeletal Class II pattern (ANB, 14.3°; Wits appraisal, 10.2 mm) with a hyperdivergent skeletal pattern (SN-MP, 52.6°). Her maxillary and mandibular incisors were within the normal range (U1-SN, 102.1°; IMPA, 87.2°) ( Fig 5 ; Table ), and her American Board of Orthodontics Discrepancy Index score was 63 ( Fig 6 ).

Table
Cephalometric measurements
Measurement Norm Pretreatment Posttreatment
SNA (°) 82.0 82.2 80.5
SNB (°) 80.0 67.5 75.5
ANB (°) 2.0 14.7 5.0
Mp-SN (°) 32.0 51.1 41.6
FMA (°) 25.0 42.5 26.0
SN-U1 (°) 104.0 102.1 92.4
U1-NA (mm) 4.0 0.7 2.5
IMPA (°) 90.0 87.2 102.4
L1-NB (mm) 4.0 7.0 7.9
Upper lip (mm) −4.0 −1.4 −8.5
Lower lip (mm) −2.0 −3.5 −6.7

Fig 6
ABO Discrepancy Index score. ABO , American Board of Orthodontics.

Treatment objectives

The following treatment objectives were established:

  • 1.

    Advance the mandible.

  • 2.

    Decrease the vertical maxillary excess.

  • 3.

    Establish Class I molar and canine relationship.

  • 4.

    Establish normal overbite and overjet.

  • 5.

    Relieve crowding.

  • 5.

    Improve facial profile and smile esthetics.

Treatment alternatives

Orthognathic surgery was definitely necessary on the basis of the patient’s clinical history, chief complaint, and the clinical findings. The phenotypical bird-face deformity was well characterized in this patient’s clinical presentation.

The most ideal surgical option would have been bilateral inverted L osteotomies (mandible first) to advance the mandible and lengthen the posterior ramus-condyle complex using iliac crest bone grafts to fill the osteotomy gap. This would be followed by a 3-piece LeFort I with differential impaction to expand her posterior segments, impact her anterior segment, and allow a counterclockwise rotation of her maxillary occlusal plane, which would allow greater horizontal advancement of her mandible. This treatment plan would correct the vertical maxillary excess, transverse discrepancy, and the excessive maxillary incisor display. In addition, it could be accompanied by a lip lengthening procedure, advancement genioplasty, and elective rhinoplasty to improve overall facial balance. This treatment plan was not selected because of the surgeon’s preferred surgical technique and because the patient was only interested in correcting her jaw disharmony.

The surgeon preferred an alternate plan that used a single piece LeFort I because of the patient’s relatively small maxillomandibular transverse discrepancy and to simplify the already complex surgery, which would only be further complicated by a 3-piece LeFort I. The transverse discrepancy would therefore need to be corrected orthodontically. After autorotation of her mandible from the impaction of the maxilla, bilateral inverted L osteotomies would be completed to advance her mandible and correct her short posterior face height using iliac crest bone grafts. An accompanying advancement genioplasty would improve the position of her soft-tissue pogonion. A computer-aided surgical simulation using NemoFAB software (Nemotec, Madrid, Spain) would be used to simulate the movements of the bony segments and to visualize the results ( Fig 7 ). This simulation would then be used to discuss the skeletal movements to be accomplished on the model block surgery with the surgeon. The surgeon’s expertise and experience with model block surgery has yielded excellent results in the past. The model block surgery would be used to fabricate the interim and final surgical splints. The patient, the oral maxillofacial surgeon, and the orthodontist selected this option.

Fig 7
Virtual treatment objectives and model block surgery setup.

Other possible options included a similar 2-jaw surgery with a prosthetic joint and condylar replacement. However, the patient and the surgeon did not choose this option owing to the relatively young age of the patient and the eventual need for multiple surgeries to replace the prosthesis over the patient’s life span. Joint replacement was deemed a last resort but still a viable option, if the patient’s natural joints fail at any time. Another approach could have been mandibular distraction osteogenesis followed by a revision surgery, if needed. Although the literature supports combination maxillary and inverted L osteotomy surgery for patients who present with a bird-face deformity, a traditional BSSO with LeFort I (single or 3 piece) impaction could also have been used. Theoretically, this option would have yielded less advancement of pogonion.

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May 12, 2020 | Posted by in Orthodontics | Comments Off on Mandibular micrognathia and vertical maxillary excess correction with combination LeFort I and inverted L osteotomies
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