Changes in natural head position in response to mandibular advancement

Area of Science:

• Orthodontics and Maxillofacial Surgery
• Craniofacial Anatomy
• Surgical Outcomes Research

Background:

• Mandibular hypoplasia presents challenges in facial aesthetics and function.
• Orthognathic surgery is a common treatment for correcting severe mandibular hypoplasia.
• Understanding the impact of surgical correction on natural head position (NHP) is crucial for treatment planning and outcome assessment.

Purpose of the Study:

• To investigate the changes in natural head position (NHP) following orthognathic surgery in patients with mandibular hypoplasia.
• To determine the relationship between alterations in NHP and changes in mandibular position after surgical correction.
• To evaluate if different surgical approaches (BSSO, genioplasty, Le Fort I) influence this relationship.

Main Methods:

• A cohort of 41 patients with mandibular hypoplasia undergoing orthognathic surgery were analyzed.
• Patients were categorized into three surgical groups: bilateral sagittal split osteotomy (BSSO) advancement, BSSO with genioplasty, and Le Fort I with BSSO advancement.
• Cone-beam computed tomography (CT) scans were used to measure craniocervical and craniomandibular angles, and distances to the frontal plane, preoperatively and six weeks postoperatively.

Main Results:

• All surgical groups demonstrated significant changes in both mandibular position (increased craniomandibular angle, decreased anterior-posterior distance) and NHP (increased craniocervical angle, decreased anterior-posterior distance).
• Statistical analysis revealed a significant correlation between the magnitude of change in mandibular position and the change in NHP across all patient groups.
• No significant differences were found between the surgical groups regarding the changes in NHP or its correlation with mandibular repositioning, indicating a consistent effect.

Conclusions:

• Orthognathic surgery for mandibular hypoplasia leads to predictable changes in both mandibular position and natural head position.
• The observed changes in natural head position are significantly correlated with the extent of mandibular repositioning achieved surgically.
• The specific surgical technique employed (e.g., addition of genioplasty or Le Fort I osteotomy) does not alter the fundamental relationship between mandibular movement and natural head position adjustments.