Quantitation of Zygomatic Complex Symmetry Using 3-Dimensional Computed Tomography

Purpose: 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. Materials and Methods: 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 Delta E and Delta W, 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 (Delta cE). Results: The Delta E value was lower than the Delta cE value (0.6 vs 1.75 mm; P < .001). None of the results for DE were larger than 2 mm, and 7 results (3.5%) for Delta W were larger than 2 mm. By comparison, 57 results (28.5%) for Delta cE were larger than 2 cm (P < .001). The intraclass correlation coefficient (ICC) indicated almost perfect agreement for inter- and intraexaminer reliabilities for Delta E (ICC, 0.82 to 0.86) and Delta W (ICC, 0.81 to 0.85) measurements, and moderate agreement for inter-and intraexaminer reliabilities was obtained for Delta cE (ICC, 0.61 to 0.68) measurements. Conclusion: This new method is practical and valuable in the clinical evaluation of ZMC symmetry. (C) 2014 American Association of Oral and Maxillofacial Surgeons