Construction and validity of a midsagittal plane based on the symmetry of a 3-dimensional model of the relevant cranial base.

INTRODUCTION

The midsagittal plane (MSP) is the foundation for 3-dimensional (3D) cephalometric analyses. This article aimed to provide a protocol to construct a reliable and accurate MSP for 3D cephalometric craniofacial analysis.

METHODS

Cone-beam computed tomography data of 16 adult patients without obvious bilateral asymmetry were collected. The model of the anterior cranial base and sphenoid bone was constructed, and the candidate MSP was determined on the basis of the symmetry of this model. Intraclass correlation coefficients were used to assess intra- and interexaminer reliability of the candidate MSP. To investigate the accuracy of this candidate MSP, we constructed a true plane of symmetry of craniomaxillofacial structure and a control plane on the basis of 3 cranial midline points. We then compared these with the candidate MSP.

RESULTS

This candidate MSP resembled the true plane of symmetry with all the mean absolute errors <1 mm, and all the absolute errors for the candidate MSP were significantly smaller than the control plane (P ≤0.002). The relative intra- and interexaminer reliability for this candidate MSP was almost perfect (intraclass correlation coefficients >0.9).

CONCLUSIONS

The candidate MSP constructed using this method was thought to be reliable and accurate for 3D cephalometric analysis in patients without obvious cranial asymmetry.