Frontal Orientation in Orthognathic Surgery and Determination of a “Surgical Vertical Target Line”

This study explores the use of the bipupillary line (BPL) as a true horizontal line (THL) for frontal orientation in orthognathic surgery (OGS), addressing the need for a reliable vertical reference, or "surgical vertical target line" (SVTL), in patients with dentofacial deformities. In a retrospective analysis of 50 consecutive patients (25 male, 25 female; mean age 27 y, range 18-52) at a specialized center in Buenos Aires, Argentina, we standardized frontal orientation using the BPL and determined the SVTL based on its alignment with anatomic midline points, including the intercanthal point (Ic), subnasal point (Sn), philtrum (Ph), upper dental midline (UDM), and soft tissue pogonion (SPo). The SVTL was most frequently aligned with the subnasal point (86%), compared with 44% for the intercanthal point and 42% for the philtrum. The selection of the SVTL was individualized for each patient to best suit the patient's face. Notably, parallelism between the BPL and bicommissural line (BCL) was observed in only 38% of cases, with divergence in 62%. Patients with a tilted BCL exhibited a significantly higher prevalence of clinical mandibular lateral deviation (CMLD) (90.3% versus 36.8%, P<0.01). Discrepancies between the SVTL and bony pogonion (BPo) on CBCT revealed that deviations ≥2 mm were clinically detectable in all cases, while those <2 mm were imperceptible in 83.3% of cases (P<0.01). On the basis of these findings, we propose a classification for mandibular lateral deviation: subclinical (<2 mm), slight (2-<4 mm), moderate (4-<8 mm), and severe (≥8 mm). The BPL-based frontal orientation and SVTL protocol offer a simple, reproducible approach that enhances diagnostic accuracy and supports precise surgical planning in OGS.