Nowadays, maxillary Le Fort I osteotomy is a safe and routinely performed procedure. The conventional approach is characterized by a vestibular incision extending from molar-to-molar, associated with a pterygomaxillary disjunction performed with a curved chisel. Adequate mobilization of the maxilla during Le Fort I osteotomy requires an effective separation of the maxillary tuberosity from the pterygoid plates of the sphenoid bone. However, as initially described by Precious (1991) and later by Hernandez-Alfaro (2013), a true pterygomaxillary osteotomy is not necessary to achieve successful disjunction. Furthermore, Hernandez-Alfaro combined his technique of pterygomaxillary disjunction, the so-called "Twist technique", to a minimally invasive protocol, performing the complete Le Fort I osteotomy through a 20 to 30 mm long horizontal vestibular incision. Although promising, the technique remains highly sensitive from a technical standpoint, and its true accuracy has not been comprehensively evaluated.

The purpose of this study is to present and validate a minimally invasive approach towards Le Fort I osteotomy, using a modified pterygomaxillary (PTM) disjunction technique. The primary outcome is to evaluate the accuracy of the technique using rigid voxel-based registration of the 3D virtual treatment planning and the 4 weeks postoperative CBCT images. Secondary outcomes include the surgical time necessary to complete the procedure and the presence of intraoperative and early postoperative complications.

Inclusion Criteria:

• Patients of all ages
• Patients of all genders
• A Le Fort I osteotomy is planned, as part of a bimaxillary orthognathic procedure
• The surgery is planned with 3D Virtual Treatment Planning (Maxilim v. 2.3.0.3.0.)
• The planning is transferred with 3D CAD/CAM tooth-borne splint and vertical internal bony reference landmarks
• The maxilla is repositioned first during the surgery (maxilla first sequence)

Exclusion Criteria:

• Patients not eligible according to abovementioned criteria
• Simultaneous extraction of impacted teeth 18 and/or 28
• Previous maxillary orthognathic surgery
• Previous Surgical Assisted Rapid Palatal Expansion (SARPE)
• Syndromic condition, including cleft lip and palate
• Segmental Le Fort I osteotomy
• Adjuvant Zygomatic osteotomy
• Maxillary impaction higher than 3 mm
• Maxillary advancement greater than 5 mm

All consenting patients requiring a bimaxillary orthognathic procedure as part of their orthodontic-surgical treatment plan, and satisfying the inclusion and exclusion criteria.