Do vertical soft-tissue and actual bony landmarks correlate in Le Fort I orthognathic surgery?

Publication date: Available online 27 November 2018

Source: Journal of Oral and Maxillofacial Surgery

Author(s): Cynthia Tsay, Rajendra Sawh-Martinez, Anamika Veeramani, Derek Steinbacher

Abstract

Purpose

Vertical changes in LeFort I orthognathic surgery are critical to the overall aesthetic result. 3D planning enables vertical measurements from the rendered CT scan, but intraoperative points are ascribed partially from soft tissues landmarks. This study compares intraoperative soft tissue vertical measurements with pre- and postoperative CT-based values, and attempts to validate intraoperative soft tissue landmarks for vertical positioning.

Methods

In this retrospective, single cohort study, we examined orthognathic procedures performed by a single surgeon at our institution. Patients were excluded if measurements and/or pre- and postoperative CT scans were lacking. Demographic information and soft tissue perioperative data were tabulated. Clinical vertical measurements included: left medial canthus to central incisor, left medial canthus to left canine, and right medial canthus to right canine. Bone measurements were calculated using pre- and postoperative CBCT scans for the same clinical landmarks. Statistical analysis including paired Student's t-test was performed using SPSS.

Results

42 patients were identified with a mean age of 23 years, and 57% were female. The change in pre- and postoperative measures was analyzed. There was no significant difference between the absolute value pre-and postoperatively between the two modalities (p<0.2, 0.1, 0.1) but a significant difference between bony and soft-tissue measurements (p<0.01). Subset analysis showed differences in postoperative values between class II and III cases.

Conclusion

Our results demonstrate a non-linear but predictable relationship between intraoperative soft tissue (medial canthi-maxillary dentition) and CT-measured bony vertical measurements. Understanding this relationship enables effective use of intraoperative measures to reproducibly achieve the desired bony vertical position, while allowing adjustments to be made in order to optimize aesthetics.

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