Method for accessing zygomatic-maxillary complex symmetry: Mirroring, transposing, and calculating Hausdorff distance.

Abstract

<h4>Background</h4>To provide an objective means of outcome assessment, we developed an innovative methodology to evaluate facial symmetry without defining an anatomical midsagittal plane. This study aimed to assess this novel methodology for evaluating zygomaticomaxillary complex (ZMC) symmetry.<h4>Methods</h4>Patients who underwent ZMC fracture reduction with available postoperative facial computerized tomography (CT) images were included in the study group. The control group comprised patients who underwent facial surgeries unrelated to ZMC fractures and had either pre- or postoperative facial CT images. Segmented 3D models reconstructed from CT images, including forehead and bilateral ZMCs, were mirrored, transposed, and analyzed using Hausdorff distance (HD) to quantify the maximum morphological and spatial deviation between the two sides. The 95th percentile HD values (HD95) were calculated to represent the top 95% of surface-to-surface distances between mirrored and contralateral ZMCs, serving as an objective measurement of symmetry.<h4>Results</h4>The study group included 21 patients (12 males, nine females), consisting of two with isolated ZMC arch fractures, 12 with ZMC complex fractures, and seven with ZMC fractures combined with orbital blow-out or Le Fort I fractures. The control group comprised 22 patients (13 males, nine females) without ZMC fractures, including six with mandible fractures, two with orbital floor blow-out fractures, 11 with parotid gland tumors, and three who had undergone rhinoplasty. The mean HD95 was significantly higher in the study group (3.48 ± 1.50 mm) compared with the control group (2.00 ± 0.76 mm) ( p = 0.0002).<h4>Conclusion</h4>This study demonstrated that the bilateral ZMC symmetry can be effectively and objectively assessed using a novel approach that combines mirroring, transposing, and HD analysis. This approach offers a quantitative tool that may enhance preoperative planning and postoperative evaluation.