Adding depth to cephalometric analysis: Comparing two- And three-dimensional angular cephalometric measurements

Introduction: Lateral cephalometric radiographs (LCR) have been the standard tool used for cephalometric analysis in craniofacial surgery. Over the past decade, a three-dimensional (3D) revolution in cephalometric analysis and surgical planning has been underway. To date, research has not validated whether cephalometric measurements taken from two-dimensional (2D) and 3D data sources are equivalent and interchangeable. The authors sought to compare angular cephalometric measurements taken with 2D and 3D modalities. Methods: Sixty-two head CT scans (36 females, 26 males) with an average age of 63-20 years were studied. Twelve cephalometric angular measurements were taken from 3D reconstructed skulls using the software package Mimics 19.0 (Materialize; Leuven, Belgium). These same facial angles were measured from 2D lateral cephalograms reconstructed from the original CT scans using Dolphin 11.9. Measurements taken with both techniques were compared for agreement using a paired t test. Intra-class correlation coefficient assessment was used to determine interrater reliability. Statistical significance was set at P<0.05. Results: Five of the 12 angular measurements (SNA, SNB, MP-FH, U1-SN, and U1-L1) demonstrated statistically significant differences (P<0.05) between the 2D and 3D analyses. All of these differences were less than the standard deviations for the respective measure. Conclusion: The differences between angular cephalometric values obtained from 2D LCRs and 3D CT reconstructions are small. This supports the practices of using 2D and 3D cephalometric data interchangeably in most applications. Clinicians must be selective in which measures they employ to maximize accuracy and care must be taken when measuring dental inclination with lateral cephalograms.