Transversal accuracy and stability of segmented Le Fort I osteotomy.

OBJECTIVES: To prospectively evaluate the transversal surgical accuracy and one-year stability of segmented Le Fort I osteotomy using a validated three-dimensional (3D) voxel-based assessment protocol. METHODS: In this prospective single-center study, patients undergoing two-piece or three-piece segmented Le Fort I osteotomy for transverse maxillary deficiency were included. Virtual surgical planning was performed using computer-aided design/ manufacturing (CAD/CAM) workflows. Cone-beam computed tomography (CBCT) scans were acquired preoperatively, one week, 6 months and one year postoperatively. The primary outcome was one-year dental transverse relapse, analyzed as a continuous variable. Skeletal transverse width was measured between the greater palatine foramina, and dental width between the maxillary first molars. Segment-specific surgical accuracy and postoperative stability of the lateral maxillary segments were quantified using a validated 3D voxel-based registration protocol across six degrees of freedom. Clinically relevant instability was defined as a transverse relapse of ≥2 mm. Multivariate regression analysis was used to identify predictors of relapse. RESULTS: Twenty-seven patients (14 two-piece, 13 three-piece) were included. Mean skeletal transverse expansion was 3.75 mm, whereas mean dental expansion was 1.55 mm. At one year, mean skeletal and dental relapse were 0.79 mm and 0.72 mm, respectively. Dental relapse (≥2 mm) occurred in 22.2% of patients, while skeletal relapse (≥2mm) was observed in 18.2%. Logistic regression demonstrated that greater planned dental expansion significantly increased the risk of dental relapse, with each additional millimeter increasing the odds by 28%. A data-derived Youden threshold of approximately 3.5 mm showed moderate discrimination (specificity 0.81; sensitivity 0.67) but requires external validation. Postoperative roll-related stability changes were associated with dental relapse. CONCLUSIONS: Segmented Le Fort I osteotomy provides predictable skeletal transverse expansion with acceptable one-year stability in this prospective cohort. Dental transverse expansion is more susceptible to relapse than skeletal widening, and greater planned dental expansion increased the risk of clinically relevant dental relapse. Segment-specific 3D assessment suggests that postoperative rotational control, particularly roll stability of the lateral segments, may be relevant for transverse stability.