A Method for Locating the Summit of Zygoma and Radiographic Measurement of Zygoma in Patients With Hemifacial Microsomia

BACKGROUND: To explore a method for locating the summit of zygoma (SOZ) for patients with hemifacial microsomia and to analyze the asymmetry of the zygomatic bone in patients with hemifacial microsomia. METHODS: A retrospective study was conducted with consecutive patients diagnosed with hemifacial microsomia. A cylinder perpendicular to the horizontal plane was established, with its axis passing through the midpoint of the sella turcica, on 3D-reconstructed images. By adjusting the cylinder's radius, the SOZ was identified as the point where the zygomatic bone protrudes slightly above the cylinder's surface. Radiologic measurements were conducted in hemifacial microsomia patients using 6 indicators (SOZ-O, SOZ-X, SOZ-Y, SOZ-FP, zy-Y, and zy-FP). Radiographic data were recorded and analyzed to reveal the differences between the bilateral zygoma. RESULTS: A total of 84 patients were included, with an average age of 16.1 years or younger. The paired t test of bilateral measurements revealed statistically significant differences in 6 indicators (SOZ-O, SOZ-X, SOZ-Y, SOZ-FP, zy-Y, and zy-FP). The results show that 95.29% of the patients exhibit minor malar bone protrusion on the affected side, while 88.24% demonstrate SOZ more cephalic on the affected side. CONCLUSION: The SOZ locating method used in this study demonstrated excellent accuracy and reproducibility for patients with hemifacial microsomia. Most patients exhibited a smaller zygomatic bone on the affected side compared with the normal side, with the affected side showing cephalic zygomatic prominence and narrower facial width. However, there were exceptions in which the affected side showed greater protrusion than the normal side. LEVEL OF EVIDENCE: Level IV.