Evaluation of mandibular hypoplasia in patients with hemifacial microsomia: a comparison between panoramic radiography and three-dimensional computed tomography.

OBJECTIVE

To compare the accuracy of three-dimensional computed tomography (3D-CT) and panoramic radiography in the evaluation of mandibular hypoplasia in patients with hemifacial microsomia (HFM).

DESIGN

Retrospective study of imaging data.

Setting

Images selected from the archives of the University of Tokyo Hospital.

SUBJECTS: Twenty patients with unilateral HFM who had undergone both panoramic radiography and 3D-CT in the same period.

METHOD: Mandibular deformities were classified according to the Pruzansky classification; eight patients had Grade I deformity and 12 patients had Grade II deformity. Ramus heights were measured on both panoramic radiographs and 3D-CT.

MAIN OUTCOME MEASURES: Magnification in panoramic radiographs and extent of mandibular asymmetry as estimated by the affected/unaffected side ratio based on two methods were examined. The Pearson product-moment correlation coefficient was used to estimate correlations between parameters.

RESULTS

The magnification of ramus heights on panoramic radiographs showed large variations in Grade II patients. The affected/unaffected side ratio estimated by the two methods showed a strong correlation in Grade I patients (correlation coefficient 0.99; p < .0001). Conversely, a weak correlation was seen in Grade II patients (correlation coefficient 0.77; p  =  .0036), and affected/unaffected side ratios from panoramic radiographs were both over- and underestimated.

CONCLUSIONS

The accuracy of evaluation using panoramic radiography was fairly reliable in Grade I patients. Conversely, accuracy was poor in Grade II patients, and evaluation using 3D-CT seems preferable. The combination of two methods with careful consideration is recommended for clinical applications.