The Evaluation of the Pterygomaxillary Separation Pattern in Le Fort I Osteotomy Using Cone Beam Computed Tomography.

Pterygomaxillary separation (PMS) is an important step in Le Fort I osteotomy procedure, without which complete mobilization of the maxilla cannot be achieved. The aim of this study was to evaluate PMS patterns and their relationship with the anatomic measurements in Le Fort I osteotomy. In this prospective observational study cone beam computed tomography (CBCT) was used to measure the anatomic variables of the pterygomaxillary junction (PMJ) region including thickness, width, the distance between the most concave point at the lateral surface of PMJ and the greater palatine foramen (C-GPF), and the angle preoperatively, and the separation patterns postoperatively divided into the clean-cut type, maxillary sinus type, and the pterygoid fracture type. Twenty-seven patients (54 sides) were included in this study. Nineteen females (70.4%) and 8 males (29.6%) with a mean (standard deviation) of 22.1 (5.5) years. The mean PMJ thickness, width, C-GPF, and angle were 5.6 mm, 8.6 mm, 6.55 mm, and 91.5 degrees, respectively. The most common PMS pattern was the clean-cut type (38/54, 70.4%), followed by the pterygoid plate fracture type (10/54, 18.5%), and the maxillary sinus type (6/54, 11.1%). There were non-significant relationships between the anatomic variables of PMJ and PMS patterns (thickness P =0.179, width P =0.234, C-GPF P =0.174, and angle P =0.792). There were non-significant relationships between PMS patterns and age, sex, and skeletal classification of the patients ( P = 0.941, 0.211, and 0.519, respectively).