Variation in natural head position and establishing corrected head position

Area of Science:

• Cephalometric analysis
• Anthropometry
• Orthodontics

Background:

• Corrected head position (CHP) is crucial for orthodontic diagnosis, orthognathic surgery, and anatomical studies.
• The traditional Frankfurt horizontal (FH) plane for simulating CHP shows significant individual variability.
• Understanding natural head position (NHP) reproducibility is key to improving cephalometric accuracy.

Purpose of the Study:

• To investigate the relationships between natural head position (NHP) and various cephalometric planes.
• To evaluate the reproducibility of NHP over time in a longitudinal sample.
• To identify alternative cephalometric planes for more consistent determination of corrected head position (CHP).

Main Methods:

• Analysis of natural head position (NHP) cephalograms from Aboriginal Australians and two orthodontic practice samples.
• Longitudinal assessment of NHP reproducibility over approximately 8 years in the Aboriginal Australian cohort.
• Comparison of angulations between NHP, stable basicranial line (SBL), neutral horizontal axis (NHA), Frankfurt horizontal (FH), palatal plane (P plane), and Krogman-Walker plane (KW plane) relative to the true horizontal (HOR).

Main Results:

• NHP reproducibility showed an absolute mean difference of 2.9°, with a range of -7.9° to 8.2° and a standard deviation of 3.6°.
• Selected cephalometric planes (SBL, NHA, FH, P plane, KW plane) exhibited near parallelism.
• Mean angulations of these planes from the true horizontal (HOR) ranged from -4.6° to 2.4°.

Conclusions:

• Natural head position (NHP) is not consistently reproducible at the individual level.
• The combined use of stable basicranial line (SBL), palatal plane (P plane), and Krogman-Walker plane (KW plane) can lead to a more consistent corrected head position (CHP).
• These findings suggest improved methods for cephalometric analysis in orthodontics and surgical planning.