# Characterization of Pterygomaxillary Suture Morphology: A CBCT Study
## 4 Discussion
Clinically, this measurement, based on the Israeli population, implies that when a curved osteotome with a cutting edge of about 15 mm is used to separate the PMS in a Le Fort I osteotomy, the mean safety margin from the pterygomaxillary fissure is 1.5 mm. However, it should be remembered that anatomical variations exist regarding the PMS height and that an individual CBCT evaluation is critical prior to the surgical procedure. Regarding the PMS thickness, we found that in our sample the mean thickness was 1.0 \(\pm\) 0.13 mm and 0.9 \(\pm\) 0.17 mm in males and females, respectively. Although the biological difference between the sexes seems to be minimal, this difference was found to be statistically significant. Previous studies evaluated the thickness using a different method [8,17]; however, some sex-related differences were also found. [PERSON] et al. [25] found an association between PMS thickness and unwanted fractures in the pterygoid process. It was suggested that the force applied from the osteotome is easily dissipated when a thin pterygomaxillary junction is present, which may lead to an unwanted pterygoid plate fracture. Thus, the PMS thickness should serve as an approximate estimate for the surgeon regarding the amount of force that should be applied to the osteotome during PMS separation. The ideal fracture line begins laterally to the PMS and progresses radially along the PMS between the maxilla and the pterygoid process. Knowing the angle between the sagittal plane and the PMS can help the oral and maxillofacial surgeon to determine at which angulation to place an osteotome for PMS separation and thus possibly minimize the incidence of unwanted fracture lines. In our study, we found that the PMS angulation, measured at the greatest thickness of the suture, was about 58 \(\pm\) 4.6\({}^{\circ}\) for both males and females, regardless of the measured side (right and left) and the patient's age. Therefore, it is reasonable to assume that the sharp edge of the osteotome used to separate the suture should be placed at this angle in order to create ideal separation (Figure 6). Figure 5: Simulation of the osteotome position during PMS separation on the dry skull, lateral view. (**A**) Dry skull from the lateral view. Dotted line represents PMS height. (**B**) Osteotome placed on the PMS height of the dry skull. The cutting edge of the osteotome is about 1.5 mm less than the mean PMS height (16.5 mm, white arrow). Using 12 cadavers, [PERSON] [26] compared frequency that a pterygoid plate fracture occurred when a regular osteetome (50 degrees) and a large-angle osteetome (80 degrees) were used during Le Fort I osteotomy. His findings suggest that although the incidence of pterygoid plate fracture was lower using a large angle osteetome, there was a greater risk of unwanted palatinal bone separation. The mean PMS angulation in an Israeli population was found to be 58 degrees; however, this angle may differ between patients due to anatomical variations. Owing to the \"blind\" approach of PMS separation, it is difficult to identify the instrument's angle relative to the sagittal plane in the operating room. Therefore, we suggest estimating the PMS size and the position measurements using the patients' CBCT as well as practicing the PMS angle on a printed 3D model prior to performing the surgical procedure.