Quantitation of zygomatic complex symmetry using 3-dimensional computed tomography

To improve the clinical evaluation of the symmetry of the zygomatic complex (ZMC), the authors developed a new method to measure the eminence and width of the ZMC using 3-dimensional (3D) computed tomography (CT). The accuracy and reproducibility of the ZMC symmetry evaluation using this method were investigated.

Spiral CT was carried out in 50 volunteers with visually symmetric faces. Based on an exact craniofacial midsagittal plane, a 3D coordinate system was constructed and used to measure the eminence and width of the ZMC. Absolute differences between the bilateral eminences and widths were calculated as ΔE and ΔW, respectively. The ZMC eminence also was measured based on traditional methods using anatomic landmarks, and the bilateral absolute difference was calculated to serve as a control (ΔcE).

The ΔE value was lower than the ΔcE value (0.6 vs 1.75 mm; P < .001). None of the results for ΔE were larger than 2 mm, and 7 results (3.5%) for ΔW were larger than 2 mm. By comparison, 57 results (28.5%) for ΔcE were larger than 2 cm (P < .001). The intraclass correlation coefficient (ICC) indicated almost perfect agreement for inter- and intraexaminer reliabilities for ΔE (ICC, 0.82 to 0.86) and ΔW (ICC, 0.81 to 0.85) measurements, and moderate agreement for inter- and intraexaminer reliabilities was obtained for ΔcE (ICC, 0.61 to 0.68) measurements.

This new method is practical and valuable in the clinical evaluation of ZMC symmetry.