The effects of differences in landmark identification on the cephalometric measurements in traditional versus digitized cephalometry

The aim of this study was to explore the effects of differences in landmark identification on the values of cephalometric measurements on digitized cephalograms in comparison with those obtained from original radiographs. Ten cephalometric radiographs were randomly selected from orthodontic patients' records. Seven orthodontic residents identified 19 cephalometric landmarks on the original radiographs and digitized images. Twenty-seven cephalometric measurements were computed with a customized computer-aided program. To assess the concordance between cephalometric measurements derived from landmarks identified on the original radiographs and those from digitized counterparts, the values of 27 cephalometric measurements were compared to quantify the absolute value of measurement difference and the interobserver errors between these two methods. We found that the differences of all cephalometric measurements between original radiographs and their digitized counterparts were statistically significant. The differences in 21 of the 27 cephalometric items were less than two units of measurement (mm or degree), which is generally within one standard deviation of norm values in conventional cephalometric analysis. Moreover, statistically significant differences of interobserver errors between the two methods were noted only for seven of the 27 cephalometric items. In conclusion, the measurement differences between the original cephalograms and the digitized images are statistically significant but clinically acceptable. The interobserver errors for cephalometric measurements on our digitized cephalometric images are generally comparable with those on the original radiographs. The results of our study substantiated the benefits of digital cephalometry in terms of the reliability of cephalometric analysis.