Accuracy of Condylar Position in Orthognathic Surgery Cases Treated with Virtual Surgical Planning: An Exploratory Study

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  • March 20, 2019
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  • Wan, Ying
    • Affiliation: School of Dentistry, Department of Orthodontics
Abstract
  • Objectives: To assess the pre- and short-term post-operative positions of the mandibular condyle in bimaxillary orthognathic surgery cases prepared using Virtual Surgical Planning (VSP). Additional aims are to evaluate the relationship between surgical characteristics and condylar positional changes, as well as to quantify the difference between actual surgical outcome and planned virtual outcome. Methods: 15 consecutively operated subjects with Bilateral Sagittal Split Osteotomies (BSSO) prepared with VSP and 10 subjects with conventional surgery planning were selected from a private practice database retrospectively. 3D models generated from CBCT scans obtained pre-surgically (T1), post-surgically (T2), and from the VSP predictions were then oriented to Frankfurt horizontal, superimposed, and registered on the anterior cranial base through a voxel-based method. Anatomic landmarks on the condyles, maxilla, and mandible were manually selected on T1, T2, and VSP models using SlicerCMF (open-source software). Displacement of corresponding landmarks on T1, T2, and VSP models was measured in both 3D distance and in its component vectors in the transverse, vertical, and anteroposterior axes. Results: Study groups were well matched for demographic and surgical characteristics except for the type of surgery performed in addition to the BSSO. No significant difference was found between the VSP and conventional group in the magnitude of translation or rotation of the condyles following surgery. Mandibular shape was the only surgical characteristic found to correlate with condylar yaw (P=0.045, Rz = 0.035). VSP surgical outcomes differed significantly at all measured landmarks and in all dimensions from predicted outcomes. Conclusion: Virtual surgical planning does not prevent changes to condylar position as a result of surgery. The magnitude of condylar torque following surgery was largely unexplained by surgical factors such as mandibular shape, mandibular plane, magnitude of mandibular movement, and rotation of mandibular plane. Actual surgical results differed significantly from VSP-predicted outcomes.
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  • In Copyright
Advisor
  • Blakey, George
  • Jackson, Tate
  • Nguyen, Tung
Degree
  • Master of Science
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2017
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