Which intracranial plane can be used instead of the true horizontal plane?

Abstract

Purpose The aim of this study was to evaluate the reliability of the Frankfort horizontal (FH), sella-nasion horizontal (SN-h), optic, and orbitooccipital planes by assessing their variabilities relative to a true horizontal line (TrH) in Class 1, 2, and 3 patients. Materials and Methods Eighty-one pre-treatment lateral cephalometric radiographs (LCRs) (27 each from Class 1, Class 2, and Class 3 based on ANB (degrees) were taken in the natural head position (NHP). NHP was created using a laser level creating the true vertical line and the TrH perpendicular to the true vertical.The inclinations of the anatomic reference planes were compared with the TrH. Results The orbitooccipital and FH planes were closest to the TrH, with mean values of-0.55 +/- 3.26 and-0.60 +/- 3.67, respectively. The mean value for the SN-h was 3.33 +/- 4.40, whereas the mean value for the optic plane was 4.46 +/- 4.58. The ranges were high for all anatomic planes:-9.03 degrees to 8.22 degrees for the FH plane,-8.79 degrees to 6.49 degrees for the orbitooccipital plane,-9.87 degrees to 13.16 degrees for the SN-h, and-4.21 degrees to 16.43 degrees for the optic plane. No significant differences were found in relation to skeletal patterns (orbitooccipital plane; p=0.05, FH plane: p=0.115, SN-h; p=0.156, optic plane; p=0.063, respectively). Regarding sex, there was a significant difference in the optic plane in only Class 1 females (p=0.024). Conclusion The FH and orbitooccipital planes are not the same TrH, but they are the closest reference planes. Variations in reference planes affect diagnosis and therapy.