J Korean Assoc Oral Maxillofac Surg.  2015 Jun;41(3):156-164. 10.5125/jkaoms.2015.41.3.156.

Stability of unilateral sagittal split ramus osteotomy for correction of facial asymmetry: long-term case series and literature review

• Lee SG
• Kang YH
• Byun JH
• Kim UK
• Kim JR
• Park BW

• KMID: 1797847
• DOI: http://doi.org/10.5125/jkaoms.2015.41.3.156

Abstract

Bilateral sagittal split ramus osteotomy is considered a standard technique in mandibular orthognathic surgeries to reduce unexpected bilateral stress in the temporomandibular joints. Unilateral sagittal split ramus osteotomy (USSO) was recently introduced to correct facial asymmetry caused by asymmetric mandibular prognathism and has shown favorable outcomes. If unilateral surgery could guarantee long-term postoperative stability as well as favorable results, operation time and the incidence of postoperative complications could be reduced compared to those in bilateral surgery. This report highlights three consecutive cases with long-term follow-up in which USSO was used to correct asymmetric mandibular prognathism. Long-term postoperative changes in the condylar contour and ramus and condylar head length were analyzed using routine radiography and computed tomography. In addition, prior USSO studies were reviewed to outline clear criteria for applying this technique. In conclusion, patients showing functional-type asymmetry with predicted unilateral mandibular movement of less than 7 mm can be considered suitable candidates for USSO-based correction of asymmetric mandibular prognathism with or without maxillary arch surgeries.

Keyword

Unilateral sagittal split ramus osteotomy; Functional facial asymmetry; Laterognathism; Temporomandibular joint

MeSH Terms

Facial Asymmetry*
Follow-Up Studies
Head
Humans
Incidence
Orthognathic Surgery
Osteotomy, Sagittal Split Ramus*
Postoperative Complications
Prognathism
Radiography
Temporomandibular Joint

Figure

• 

  Fig. 1 Measurement of the ramal height (RH), condylar height (CH), and mandibular width (MW). A. On panoramic radiography, RH and CH were measured preoperatively and 2 years postoperatively, as previously described by Habets et al.6 and Kilic et al.8. B. On posteroanterior cephalometric radiography, the MW (bigonial width) and RH were measured simultaneously, as described by Snodell et al.7. (P1, P2: the most lateral points of the ramus, P3: intersection point of line A and line B, Line A: ramus tangent, Line B: perpendicular line from line A to the superior part of the condylar image).

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  Fig. 2 Preoperative and postoperative clinical examination and radiography in case 1. A, B. Preoperative facial photography and cephalometry shows facial asymmetry with rightward chin deviation, but both condyles are symmetrical in size and thickness. C. Preoperative intraoral photography indicates unilateral posterior crossbite on the right side and a narrow palatal arch. D. Intraoperative photography shows the unilateral surgically-assisted rapid palatal expansion, with osteotomy only at the mid-palatal suture and the left side of the anterior maxillary wall (arrows). E-G. Two years after unilateral sagittal split ramus osteotomy (left side, 6-mm setback) and postoperative orthodontic treatment, the patient had symmetrical chin morphology and balanced occlusion.

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  Fig. 3 Preoperative and 2-year postoperative panoramic radiography of present cases. The osteotomy sites and remaining miniplates are indicated by arrows. On postoperative panoramic radiography, all cases show symmetric mandibular condylar size and ramus height, and no evidence of condylar resorption after unilateral sagittal split ramus osteotomy.

• 

  Fig. 4 Clinical and cephalometric radiography of case 2. A, B. Preoperative facial photography and cephalometry shows a protruded mandible and leftward chin deviation, both the condyles and the ramus height are uniform. C. Intraoral preoperative photography reveals unilateral posterior crossbite on the left side, missing right lower posterior teeth, and extrusion of the opposing upper teeth. D-F. After performing unilateral mandibular setback (7 mm) with unilateral sagittal split ramus osteotomy on the right side and postoperative orthodontic treatment, the patient achieved facial symmetry and stable occlusion.

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  Fig. 5 Computed tomography to evaluate condylar contour at the non-osteotomized site more than 3 years after unilateral sagittal split ramus osteotomy. There was no evidence of cortical bone destruction.

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  Fig. 6 Clinical photography and radiography of case 3. A-C. The patient shows asymmetric mandibular prognathism, left unilateral crossbite, loss of multiple bilateral lower posterior teeth, and extrusion of opposing teeth. D-F. Postoperative orthodontic treatment after right unilateral sagittal split ramus osteotomy (6-mm setback) and unilateral posterior maxillary segmental osteotomy, the patient obtained symmetrical facial morphology and balanced occlusion.

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