Evaluation of cortical bone thickness at the nasomaxillary and zygomaticomaxillary buttresses using cone-beam computed tomography imaging for Le Fort I osteotomy

Abstract

Background/purpose: Studies have indicated that 50%-55% of the population have malocclusion, and approximately 5%-10% require orthognathic surgery to correct this condition. Optimal placement of plates and screws significantly affects the success rate of the surgery and postoperative stability. This study evaluates the cortical thickness of the maxillary bone in the nasomaxillary and zygomaticomaxillary buttress regions in Taiwanese patients based on cone-beam computed tomography (CBCT) images.

Materials and methods: 128 Patients undergoing Le Fort I osteotomy were selected for this study. Their CBCT images were input into medical imaging software to simulate the placement of titanium screws and plates. The cortical bone thickness at these positions was measured to assess the thickness in the nasomaxillary buttress (surrounding the nasal opening) and the zygomaticomaxillary buttress (surrounding the maxillary zygomatic process). Associations of these thicknesses with gender, age, and screw position were analyzed.

Results: In the nasomaxillary region, cortical bone was thicker on the upper and lower vertical regions, with men generally having thicker bone. The zygomaticomaxillary region had increased thickness near the zygomatic end and distal region. Younger adults had significantly greater bone thickness in certain areas than those over 30 years.

Conclusion: The nasomaxillary region's upper and lower vertical regions and the zygomatic end in the zygomaticomaxillary region provide optimal screw placement sites. Bone thickness differences by gender and age suggest occlusal force and age-related bone resorption as influencing factors.

Keywords: Le Fort I osteotomy; Maxillary bone thickness; Nasomaxillary buttress; Orthognathic surgery; Zygomaticomaxillary buttress.

Figure 1

(a) Simulation displaying the positioning of bone screws on the reconstructed three-dimensional cranial model of the patient. (b) Placement of inverted Y-shaped bone plates in the nasomaxillary region (A–H) and L-shaped bone plates in the zygomaticomaxillary region (I–N).

Figure 2

(a) [Nasomaxillary region] Identify the vertical line perpendicular to the bone surface. (b) [Nasomaxillary region] Measure cortical bone thickness along the identified vertical line. (c) [Zygomaticomaxillary region] Identify the vertical line perpendicular to the bone surface. (d) [Zygomaticomaxillary region] Measure cortical bone thickness along the identified vertical line.