Orthognathic Surgery Workup

Updated: Oct 05, 2016
  • Author: Pravin K Patel, MD; Chief Editor: Jorge I de la Torre, MD, FACS  more...
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Workup

Imaging Studies

Clinical photographs are essential for documentation and to allow for photometric analysis. Use soft-tissue landmarks to obtain angular and linear measurements that can help define the problem quantitatively. Standardize frontal and profile photographs. A clear acetate ruler can be placed next to the patient when the photographs are obtained for reference measurement for magnification; otherwise, a proportionate-type analysis without reliance on absolute values can be used. Images with the lips at repose and during animation (smiling) are obtained; the degree of dental display is noted for each.

Skeletal evaluation typically includes radiographic evaluation with ortho–Panorex and cephalometric x-rays.

  • Ortho–Panorex x-rays provide an overview of the stage of dental development, the mandibular anatomy, and gross pathology. Specific films such as occlusal and periapical views can be obtained to further assess the dentition, supporting bone, and interdental spaces.
  • Cephalometric x-rays provide for standardized skull and/or facial views that allow for comparison over time to assess growth in an individual and for comparison of that individual against standardized population norms.
    • Skeletal views can be obtained in lateral and frontal views.
    • Lateral cephalometric x-ray allows for assessment of the elements of the dentofacial skeleton from a sagittal perspective. See the image below.
      Analysis of the dentofacial skeleton is based on i Analysis of the dentofacial skeleton is based on identifiable radiographic landmarks on a lateral cephalometric x-ray.
    • With lateral cephalometric x-ray, the maxilla can be related to the mandible and each related to their position in the skull base. Simultaneously, the soft-tissue profile can be related to the facial skeleton. See the image below.
      Lateral cephalometric analysis of the facial skele Lateral cephalometric analysis of the facial skeleton based on Steiner analysis. The positions of the maxilla and mandible each are related spatially to the anterior cranial base and to each other. Note that normative values of the facial elements depend on a normal anterior cranial base inclination and length, which typically are altered in craniofacial conditions.
    • Lateral cephalometric x-ray also allows the dentition to be related to each other, and each can be related to its own skeletal base, the maxilla, and the mandible. See the image below.
      Lateral cephalometric analysis of the dentition wi Lateral cephalometric analysis of the dentition within the skeletal framework.
    • Frontal cephalometric x-ray allows for assessment of the degree of facial asymmetry.
    • Obtain quantitative measurements based on key anatomic landmarks (cephalometric analysis). Numerous cephalometric analyses exist, each emphasizing particular skeletal and dental elements. Common analyses include Steiner, Ricketts, and Delaire and are beyond the scope of this overview. For the surgeon, the analysis must be clinically workable, simple to use, and directly relatable to the skeletal elements that can be repositioned. While the analysis is invaluable, do not focus the treatment plan solely on correcting cephalometric abnormalities.

Additional radiographs include the following:

  • Periapical films are obtained to determine if sufficient space exists for interdental osteotomies.
  • On occasion, hand wrist films are useful to help determine skeletal age based on the known timing of sequential closure of the epiphyseal growth plates. However, typically facial skeletal maturity is determined by comparison of serial lateral cephalometric films obtained at 6-month intervals.
  • Three-dimensional computerized tomography (3DCT) is increasingly being used for surgical evaluation and planning in academic settings. Preoperative planning using 3DCT offers multiple potential advantages, including the ability to easily consider multiple different surgical approaches to a problem and the ability to characterize degree and direction of skeletal movement at any point over the osteotomized segment (as opposed to only the occlusal level). With advancing technology, such 3D visualization of the patient's anatomic deformity is likely to replace today's conventional 2D cephalometric analysis.
  • In cleft orthognathic surgery, plain film radiographs (occlusal and periapical) and CT are helpful in preoperatively determining the adequacy of bone across a previously bone-grafted alveolar cleft.
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Other Tests

Dental models

  • Surgical movement of maxilla and mandible inherently alter the maxillary-mandibular dental occlusion, and as such, careful analysis of the dental models with the orthodontist is essential. The maxillary dental and mandibular dental casts can be studied individually and hand manipulated with each other to assess how the arches are coordinated.
  • Assessment of the models includes space analysis and arch length, transverse width discrepancies, position of the individual tooth within its own arch, and the relationship of the maxillary dentition to the mandibular dentition.
  • Establish the diagnosis from a working problem list generated from the clinical and photographic evaluation, cephalometric analysis, and study dental models.
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