How to revise and utilise the cephalogram for craniofacial dysostosis—Modification of the porion and the McNamara line

SummaryMcNamara line analysis is often utilised in orthognathic surgery and is particularly useful in that it can easily express the extent of maxillo-mandibular deformity quantitatively. However, in craniofacial dysostosis (CFD), the location of the porion (PR) is sometimes displaced inferiorly. The McNamara line depends on the Frankfurt horizontal plane (FH plane), and hence, its deviation is often extremely distorted in CFD.The objective of this study was to enable more correct reflection of deformities of CFD patients on lateral cephalogram analysis. The lateral cephalograms of 152 Asian individuals were involved. ∠basion(BA).orbitale(Or).PR, ∠BA. nasion(NA).PR, and the distance from BA to PR on the BA-NA plane were measured and each standard range was established. Using these ranges, modified PR (mPR) is supposed to lie within a fairly small area.Second, we utilised mPR in the practice of McNamara line analysis in CFD patients. In both cases in the present study, it was confirmed that modified McNamara line analysis can express the deformities more precisely than conventinal analysis, as far as the maxillo-mandibular relationship is concerned. However, particularly in Case 2, both the cranio-maxillary and cranio-mandibular relationships were not entirely consistent with the lateral profile appearance even on modified McNamara line analysis.