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Table 2 Publications concerning landmark identification

From: Validity of 2D lateral cephalometry in orthodontics: a systematic review

Authors (year) Aim of the study Observers Subjects Design of the study Statistical method Results according to authors Level of evidence
Baumrind and Frantz [21] Quantification of errors in landmark identification 5 observers 20 lateral skull radiographs Observer identified 16 cephalometric landmarks on a transparent plastic template Mean, standard deviation and standard errors Least reliable landmarks: gonion and lower incisor apex Moderate
Effects of errors on angular and linear measurements
Kvam and Krogstad [27] Evaluation of measurements in lateral cephalograms. 18 observers 3 lateral skull radiographs Hand cephalometric analysis made by each participant, 8 angles measured Mean and standard deviation 16 out of 24 angular measurements: less variability in post-graduates than students Low
Assess influence of knowledge and impact of angular errors In 7 measurements, no difference was observed
Post-graduates' tracings used for diagnostic purposes
Standard deviation of students greater than post-graduates
Haynes and Chau [22] Evaluation of landmark identification on Delaire analysis 2 observers 28 lateral skull radiographs Establish a co-ordinate system for measurement on tracings Mean deviation Intra-observer: NS differences between values of T1 and T2 tracings Moderate
Comparison with data of conventional cephalometry Radiographs were traced twice by each observer (3 to 4 weeks) Inter-observer: differences between the averaged mean values on tracings were NS for either x or y co-ordinates
Ahlqvist et al. [26] Study the magnitude of projection errors on measurements in cephalometry 1 observer A patient was modelled Computer software designed to allow movement of model on the 3 axes. The magnitude of errors was studied by a diagram Measurement errors studied by a diagram with the relative length of distances between modelled landmarks Less than 1% error on length measurements if head is rotated up to 5° Low
Study the effects of incorrect patient position on linear measurements Head rotated more than 5° the error is increased
Houston et al. [23] Evaluate errors at various stages of measurements in cephalometric radiograph 4 observers 24 lateral cephalograms 2 radiographs of the same patient Analysis of variance Error variance is small (radiograph and tracing) when compared with the variance among groups Moderate
Radiographs traced on acetate sheet by each observer at T1/T2 (1-week interval) SNA has a higher tracing variance than SNB due to the difficulty to identify point A
Kamoen et al. [24] Determine errors involved in landmark identification and its consequence to treatment results 4 observers 50 lateral cephalograms Items studied: (1) accuracy of digitiser, (2) intra- and inter-observer digitising errors and (3) intra- and inter-observer tracing errors (1) Levene's test for homogeneity of variances, (2) one-way ANOVA and (3) Levene's test for homogeneity (1) NS variances of co-ordinates for landmark at different positions on the digitiser. (2) NS intra- and inter-observer differences in digitisation. (3) S differences in landmarks and in the same landmark on different cephalograms and between observers Moderate
Tng et al. [25] Evaluate the validity of dental and skeletal landmarks. Effect on angles and distances. 1 observer 2 lateral cephalograms of 30 dry skulls Steel balls placed in 15 dental and skeletal landmarks Mean and standard deviation 7 out of 10 skeletal and 5 dental landmarks were NS (p < 0.05) Moderate
Two radiographs taken with and without the markers and digitised. Measurements compared 4 angles (SNA-SN/MnP, MxP/MnP and LI/MnP) and 3 distances (N-Me, MxP-Me and Lie to APg) were invalid (p < 0.05)
Major errors in angles with dental landmarks
Bourriau et al. [5] Analyse the influence of film-object distance and type of receptor on landmark identification 53 orthodontists 4 lateral cephalograms of the same patient 19 cephalometric landmarks on each film Mean NS difference between 2 imaging receptors neither between 2 cephalograms achieved by 2 equipments (p > 0.99) Low
2 radiographs performed at an equipment with a 4-m arm and 2 in a 1.50-m arm equipment with 2 different imaging receptors (digital and indirect digital) Results obtained by cephalometric analysis was judged: ‘very important’ for 20.5%, ‘important’ for 70%, ‘less important’ for 8% and ‘accessory’ for 1 participant
  1. NS, non-significant; S, significant.