This study quantitatively evaluates and compares the three-dimensional (3D), 6-degrees-of-freedom (6-DOF) skeletal stability of Le Fort I osteotomies using a minimally invasive 2-plate fixation versus the conventional 4-plate approach. Utilizing a retrospective cohort design, 42 adult patients with severe skeletal Class III malocclusion were analyzed: a 4-plate control group (n=22) and a 2-plate test group (n=20). Spatial changes were measured via voxel-based cone-beam computed tomography (CBCT) superimposition at preoperative, immediate postoperative, 6-month, and 1-year intervals. A 3D semi-automated registration protocol was employed to quantify translational (X, Y, Z axes) and rotational (pitch, roll, yaw) alterations. Results indicated that baseline characteristics and initial surgical displacements were statistically equivalent between cohorts. Longitudinally, from one day to one year postoperatively, both fixation modalities demonstrated robust structural stability. All translational relapses remained below 1.0 mm; specifically, transverse drift (X-axis) was restricted to 0.31 mm in the 4-plate group and 0.37 mm in the 2-plate group. Rotational adaptations were uniformly limited to less than 1.0° across all axes, with no significant intergroup differences identified at the final assessment (p > 0.561). In conclusion, reducing rigid internal fixation from four to two plates at the zygomaticomaxillary buttresses provides equivalent 6-DOF spatial stability to the conventional method. This approach offers a reliable, minimally invasive alternative for monobloc Le Fort I osteotomies without increasing the risk of transverse or rotational relapse.
