Midsagittal Plane First: Building a Strong Facial Reference Frame for Computer-Aided Surgical Simulation.

Area of Science:

• Craniofacial anatomy and 3D imaging analysis.
• Orthodontic and surgical planning methodologies.

Background:

• Accurate facial reference frames are crucial for diagnosing and treating craniofacial asymmetries.
• The sequence of defining reference planes (midsagittal, axial, coronal) can impact frame appropriateness.

Purpose of the Study:

• To compare the appropriateness of facial reference frames constructed using two different plane definition sequences: axial-midsagittal-coronal versus midsagittal-axial-coronal.
• To investigate whether orbital or auricular dystopia influences the outcomes of these reference frame construction methods.

Main Methods:

• An ambispective cross-sectional study involving 54 subjects with facial asymmetry.
• Facial reference frames were constructed using two methods: axial plane first and midsagittal plane first.
• Evaluation by two blinded, board-certified orthodontists using a 3-point scale; statistical analysis with Wilcoxon signed rank tests.

Main Results:

• The midsagittal plane first method yielded statistically significantly more appropriate facial reference frames (P = .001).
• Appropriate frames were achieved in 40.7% of subjects using the midsagittal first method, compared to unspecified lower rates for axial first.
• The superiority of the midsagittal plane first method was consistent across subjects with and without orbital or auricular dystopia (P < .05).

Conclusions:

• The midsagittal plane first sequence offers an improvement over the axial plane first approach for constructing facial reference frames.
• Despite sequence improvements, clinicians must exercise careful judgment to ensure reference frame correctness for diagnosis and surgical planning.