Reliability of Submentovertex Projection in Assigning a Reference Cranial Midline for the Assessment of Condylar Asymmetry- A cross-sectional study

Introduction: The aim of the study was to compare the validity and reliability of two different methods for localization of the cranial midline through a cephalometric analysis of mandibular condylar asymmetry in a representative adult population. The hypothesis that the most reliable landmark for identifying transverse craniofacial asymmetry on SMV is spinosum foramina was tested. Materials and Method: This cross-sectional study was performed by analyzing the SMV radiograms of 70 patients. Two different cephalometric analyses were chosen to trace the basicranium midline. The first considers the craniostat ear rods as initial landmarks and the second analysis uses the spinosum foramina (SF) as main landmarks to identify the axis of symmetry. Quantification of the condylar asymmetry was performed using eight parameters and their symmetrical ratio (Symmetry ratio (SR) =Left parameter/Right parameter). Results: Statistical analysis of the results showed substantial equivalence and reliability of both tracing methods used. This reliability results from the fact that the left/right discrepancy for midline MP & MSP is not statistically significant. The extent of asymmetry falls within physiologic limit [2-3mm for left/right discrepancy from midsagittal plane is normal limit]. Conclusion: Submentovertex radiograms can provide assistance in diagnosing condylar asymmetries and planning the most appropriate treatment. The results of this study failed to validate our hypothesis indicating that the midline traced with spinosum foramina as landmark approximates the ideal midsagittal more closely. However another study with bigger sample size should be conducted before refuting or accepting this hypothesis.