Do Vertical Soft Tissue and Actual Bony Landmarks Correlate in Le Fort I Orthognathic Surgery?

Abstract

Vertical changes in Le Fort I orthognathic surgery are critical to the overall esthetic result. Three-dimensional planning enables vertical measurements from the rendered computed tomographic (CT) scan, but intraoperative points are ascribed partially from soft tissues landmarks. This study compared intraoperative soft tissue vertical measurements with pre- and postoperative CT-based values and attempted to validate intraoperative soft tissue landmarks for vertical positioning. In this retrospective single-cohort study, the authors examined orthognathic procedures performed by a single surgeon at their institution. Patients were excluded if measurements or pre- and postoperative CT scans were lacking. Demographic information and soft tissue perioperative data were tabulated. Clinical vertical measurements included the left medial canthus to the central incisor, the left medial canthus to the left canine, and the right medial canthus to the right canine. Bone measurements were calculated using pre- and postoperative cone-beam CT scans for the same clinical landmarks. Statistical analysis, including paired Student t test, was performed using SPSS. Forty-two patients were identified (mean age, 23yr; 57% female). The change in pre- and postoperative measurements was analyzed. There was no significant difference in the absolute value pre- and postoperatively between the 2 modalities (P<.2, .1, .1), but there was a significant difference between bony and soft tissue measurements (P<.01). Subset analysis showed differences in postoperative values between Class II and III cases. These results show a nonlinear but predictable relation between intraoperative soft tissue (medial canthi and maxillary dentition) and CT-measured bony vertical measurements. Understanding this relation enables effective use of intraoperative measurements to reproducibly achieve the desired bony vertical position and allows adjustments to be made to optimize esthetics.