Maxilla-first versus mandible-first in two-jaw orthognathic surgery: Determining factors and outcomes.

Abstract

The choice between maxilla-first and mandible-first in the double-splint method for orthognathic surgery (OGS) remains controversial. There is little comprehensive analysis regarding the factors that affect sequence selection, subsequent accuracy and stability outcomes. This retrospective study was conducted on patients with jaw deformities who underwent OGS at our center (2020-2024). Inclusion criteria were preoperative simulation using 3dimensional software and either maxilla-first or mandible-first procedures. Exclusion criteria were single-jaw surgery and incomplete data. Data pertaining to patients' anatomical characteristics and surgical plans were collected. Statistical analysis was performed to identify factors influencing the choice of sequencing. Preoperative plans and cephalometric comparisons of the immediate and long-term postoperative stages were used to evaluate accuracy and stability. A total of 308 pat ients were included, with 232 undergoing maxilla-first sequence and 76 mandible-first sequences. Mandible-first sequences were determined by factors such as: vertical maxillary lengthening procedure (OR; 42.03), obstructive sleep apnea (OR; 25.7), counterclockwise pitch rotation (OR; 13.74), cleft (OR; 5.89), segmental LeFort I (OR; 3.21), and asymmetry (OR; 2.58). In the subgroup analysis, the degree of intermediate mandibular autorotation on Virtual surgical planning (VSP) was correlated with the planned pitch rotation. However, this was significantly reduced when the surgical sequence was reversed. Sagittal movement of the maxilla was more accurate with the maxilla-first sequence. Stability was similar for both sequencing approaches. Surgical sequence selection was influenced by a combination of anatomical and planning factors. VSP played an important role in sequence determination. Both sequences achieved acceptable accuracy and stability.