Abstract: Objective: To investigate the changes in soft tissue morphology of the nasal base of patients with bony category Ⅲ by maxillary anterior displacement distance during orthognathic surgery. Methods: Twenty-four patients who underwent Le-Fort Ⅰ osteotomy anteriorly at the Stomatological Hospital affiliated to the School of Medicine of Nanjing University from February 2022 to February 2024 were collected. Spiral CT images were collected from 1 week preoperatively and more than 6 months postoperatively, and 3D reconstruction and alignment were performed by Mimics and 3-Matic software to delineate the paranasal and subnasal areas. The changes in the soft tissue line spacing, angulation, volume, and curvature in each subzone were measured. Results: The maxillary anterior displacement distance was (4.09±1.35) mm. (1) Paranasal region: the width of the nasal flank and nasal base increased by (2.50±0.99) mm and (3.37±1.42) mm; the protuberance of the right nasal flank and nasal base increased by (4.03±1.08) mm and (3.80±1.23) mm; the protuberance of the left nasal flank and nasal base increased by (3.86±1.46) mm and (3.46±1.03) mm; left and right cheek prominence increased by (2.41±0.97) mm and (2.28±0.93) mm; on the right side, the angle between the line from the point of the alar base to the infraorbital point and the coronal plane, the angle between the line from the point of the alar base to the subnasal point and the coronal plane, the angle between the line from the point of the alar base to the protuberant point of cheek and the orbital auricular plane increased by (6.69±2.47)°, (7.93±15.96)°, and (13.17±14.16)°; on the left side, the corresponding angles increased (6.01±1.92)°, (6.45±15.05)°, and (12.52±13.07)°, respectively; the volume of paranasal region in the right and left increased (1289.65±538.64) mm³ and (1297.78±589.29) mm³; the curvature of paranasal regions in the right and left increased by (0.08±0.05)/mm and (0.07±0.04)/mm; and the changes of curvature in the right and left paranasal regions were 0.24±0.12 and 0.23±0.09. (2) Subnasal region: subnasal length, subnasal protuberance, and soft tissue A-point protuberance increased (0.86±0.91) mm, (2.52±1.87) mm, and (3.68±1.49) mm; nasal length decreased (1.31±0.90) mm; supra-nasolabial angle increased (4.35±2.19)°, and facial protuberance angle decreased (9.26±4.35)°; subnasal region volume increased (1933.00±740.30) mm³; curvature of the subnasal region increased (0.11±0.09)/mm, and the rate of change was 0.38±0.20. Conclusion: After maxillary advancement, nasal alar increased, nasal length decreased, subnasal length increased, and soft tissue protrusion increased. The curvature change rates of the paranasal and subnasal areas were maintained at 0.2-0.3 and 0.4, respectively. The forward displacement operation can effectively improve the nasal basal depression.

Key words: orthognathic surgery, nasal base, soft tissue morphology