Theoretical Basis for Virtual Skull Orientation According to Three-Dimensional Frankfort Horizontal Plane for...

Area of Science:

• Medical Imaging
• Surgical Simulation
• Orthodontics

Background:

• Computer-aided surgical simulation (CASS) is crucial for planning dentofacial deformity correction.
• Accurate orientation of virtual skull models is a key step in CASS.
• The 3-dimensional Frankfort horizontal plane (3D FHP) is a critical reference plane.

Purpose of the Study:

• To explore the coplanarity of the 3D FHP in virtual skull models.
• To evaluate the 3D FHP as a method for orienting virtual skull models for CASS.
• To compare 3D FHP orientation with natural head position (NHP) orientation.

Main Methods:

• 122 cone-beam computed-tomogram (CBCT) scans were oriented to a 3D FHP using specific anatomical landmarks (right porion, right orbitale, left orbitale).
• Distances between the 3D FHP and left porion were measured.
• 18 CBCT scans with fiducial markers were oriented to NHP, and distances from left porion to a true horizontal plane were measured.
• Concordance reliability measures were calculated to compare 3D FHP and NHP orientations.

Main Results:

• The average distance of the left porion to the 3D FHP was -0.107 mm (SD = 1.148 mm).
• The average distance of the left porion in NHP to the horizontal plane was 0.846 mm (SD = 2.611 mm).
• Concordance reliability calculations indicated little consistency between 3D FHP and NHP orientation methods (P = 0.838).

Conclusions:

• The study data suggests coincidence between the left porion and the 3D FHP.
• Orienting virtual skull models using the 3D FHP is a quick and easy method for CASS.
• Further in vivo studies are recommended to evaluate this method's clinical efficacy.