The Assessment of Cephalometric Measurements at Various Degrees of Skull Orientation in the Sagittal Axis

Hypothesis: There is no significant difference in cephalometric measurements when the skull is rotated at different degrees along the sagittal axis vs when the skull is oriented ideally at zero degrees. Objective: Identify potential measurement errors on lateral cephalometric radiographs due to head rotation along the sagittal axis and assess for variability between different degrees of rotation. Methods: Existing iCAT CBCT images of 24 de-identified dry human skulls were used in this study. Lateral cephalometric images were extracted from CBCT images at 11 different skull positions, 0° to ±15°, in 3° intervals, using prospective projection. Lateral cephalograms were traced and analyzed for variability between different angles of rotation. Results: The following rotations from zero had statistically significant mean differences: +3°-SNB; +6°-SNB, NMe; +9°-SNA, SNB, ArGoMe, NMe, SGo; +12°-SNA, SNB, ArGoMe, SNMP, NMe; +15°-SNA, SNB, ANB, FMA, U1SN, SGn-FH ArGoMe, SNMP, GoMe, NMe, SGo; -3°-SNA, SNB; -6°-SNB, FMA, U1SN, NMe; -9°-SNB, FMA, U1SN, SN, NMe, SGo; -12°-FMA, SGnFH, SNMP, SN, GoMe, NMe, SGo; -15°-FMA, SGnFH, SNMP, GoMe, ANSPNS, NMe, SGo. SNB showed statistically significant mean differences in each positive distance, p<0.05. Linear horizontal measurements SN, ANSPNS, and angular measurements NAApo, L1MP and U1PP, did not show statistically significant mean differences in any of the positive distances, p>0.05. Angular measurements ANB, NAApo, ArGoMe, L1MP, and U1PP did not indicate statistically significant mean differences in any of the negative distances, p>0.05. Angular variables NAApo, L1MP, and U1PP did not indicate statistically significant mean differences in any of the distances from zero, p> 0.05. ±3° showed statistically significant mean differences, p<0.05, only on the angular variables SNB (positive and negative) and SNA (negative). Conclusions: Cephalometric measurement errors increased as skull rotation increased from 0° to ±15°. NAApo, L1MP, and U1PP were the most reliable measurements and had minimal change. Funding: N/A IRB/ACC protocol: 2018-0914