Objectives: This study measured the agreement/disagreement within several pairs of cephalometric measurements used by different clinicians to quantify essentially similar anatomical phenomena. In different "cephalometric analyses", for example, the relationship between the maxillary and mandibular apical bases is alternatively measured by the Wits Appraisal or by the angle ANB. Similarly the orientation of mandibular plane is alternatively measured relative to the SN line or the Frankfort plane.
Methods: End of treatment lateral skull x-ray images were retrospectively acquired and measured for a random sample of 111 orthodontic patients, treated in the practice of a single expert orthodontist(HP). Different conventional measurements for 5 clinically relevant anatomical phenomena were generated and compared. Each measurement was based on averaged landmark locations made independently by 3 calibrated judges. The paired measurements were correlated and the mutually explained variance was computed as r2 with the residual unexplained variance defined as 1-r2. The r2 value was accepted the proportion of agreement while 1-r2 was taken as a measure of disagreement.
Results: Representative findings are presented in tabular form (where MP= Mandibular Plane; FP=Frankfort Plane; SN=Sella Nasion; AP= Point A Pogonion, NA= Nasion Point A and "_" = "to".)
| Phenomenon Measured | Measure #1 | Measure #2 | r2 | 1-r2 |
| Mandibular Orientation | MP_FP Angle | MP_SN Ang | 0.69 | 0.31 |
| Apical Base Relationship | ANB Angle | Wits Appraisal | 0.58 | 0.42 |
| Mandibular Incisor Inclination | Incisor_MP Angle | L1_AP Ang | 0.40 | 0.60 |
| Maxillary Incisor Inclination | U1_NA Angle | U1_FP Ang | 0.01 | 0.99 |
| Mandibular Prognathism | SNP Angle | SNB Angle | 0.94 | 0.06 |
Conclusion: There is great variability in the agreement between pairs or sets of cephalometric measurements that are conventionally assumed to represent the same anatomical relationship. Before concordance is assumed, the relationship of each individual pair of measures needs to be tested.