Effects of head positioning on cephalometric measurements

The goal of the present work was to evaluate different head positions for their effects on cephalometric analysis.

Cephalograms were obtained from a skull phantom adjusted to various degrees of inclination (0°, 2°, 4°, 6°, 8°, 10°), lateral tilting (0°, 2°, 4°, 6°, 8°, 10°), and rotation (0°, 3°, 6°, 9°, 12°, 15°, and 21°). All these combinations resulted in a total of 210 digital cephalograms for assessment. On-screen analysis of these images by an orthodontist was completed within a few days.

Lateral tilting and rotation revealed considerably stronger effects on the values measured than inclination. Starting at 2° of tilting or 3° of rotation, numerous parameters yielded deviations of ≥ 2° or 2 mm from the baseline values. Increasing degrees of rotation showed more pronounced value changes than increasing degrees of lateral tilting. Skeletal and dental parameters whose landmarks are mainly located in the median plane were less susceptible than parameters whose reference points had to be averaged. Values of parameters located in the median plane were less affected by rotation when combined with higher degrees of initial lateral tilting (> 6°) than with lower ones.

The usefulness of cephalometric data becomes limited once the head is rotated by 3° or laterally tilted by 2°. Values obtained in the median plane are more stable than those obtained in peripheral locations. Various degrees of inclination applied to the skull phantom with its solid structures had no measurable effects. Accurate head positioning is an essential prerequisite for obtaining meaningful results from cephalograms based on reproducibly identifiable landmarks.