Our study findings indicate significant anatomical variations in the pterygomaxillary suture between the sexes and the facial side.
A comprehensive understanding of PMS morphology is required for precise and safe pterygomaxillary disjunction, as this could vary across sexes, ages, and sides; however, few studies have been reported. Previous imaging has reported varying thicknesses and angles relative to the sagittal plane at the level of the posterior nasal spine of the PMS obtained with CBCT [8]. In an Israeli study, PMS morphology was similar on both sides in both males and females, with significantly greater PMS thickness in males. Age-related changes in PMS morphology are not expected in individuals older than 18 in both sexes [1]. Our study describes diverse PMS morphologies across sexes, age groups, and sides to facilitate a safe pterygomaxillary disjunction procedure.
Previous investigations have found a correlation between pterygoid plate fracture type and thickness of the pterygomaxillary junction [7]. Furthermore, a study investigating eight patients’ pterygomaxillary junction via CT scans reported an average distance of 7.4 ± 1.6 mm from the greater palatine foramen to the most concave point of the pterygomaxillary junction [9]. In the present study, the thickness of the pterygomaxillary junction was greater in males than in females, at 7.76 ± 1.7 mm and 6.96 ± 1.46 mm, respectively. No significant differences in age were observed between the right and left sides. Thus, these findings can be an approximate guide for surgeons to determine the depth of osteotome application for PMS separation across sexes. Additionally, the bone density of the maxilla was statistically lower in females than in males [10]. Consequently, the force and depth of chisel invasion may be larger and deeper in males during PMS separation.
The recommended blade width of the pterygoid osteotomes is 10 mm to separate the pterygomaxillary junction completely [11]. This width is closely associated with the pterygomaxillary junction height. In Middle Eastern populations, heights were greater in males than in females, corresponding to the posteroanterior maxillary lengths and posterior facial height [12]. However, in the present study, the height of the PMJ was found to be greater in females than in males, measuring 8.9 ± 2.0 and 8.02 ± 2.21 mm, respectively. No significant differences were observed between the sides and age groups. This information guides the selection of different widths of osteotomes across the sexes. Pterygomaxillary disjunction in females may require the use of wider osteotomes in the Taiwanese population. In addition, chisels with crank-shaped and long shanks have been reported to be superior in such maneuvers, allowing for direct force transmission without obstruction from the oral commissure [13].
Three angles (120.90°, 133.92°, and 149.77°) are recommended for curved osteotomes to prevent complications [11]. The osteotomes should be tilted perpendicular to the sagittal plane to avoid additional stress on the cranial base [14]. In our study, PMS angulation had a statistically significant difference, with the right side being larger than the left, regardless of sex or age. This difference could be attributed to the dominant growth potential on the right side of the face, leading to asymmetry in the bilateral posteroanterior maxillary length, which subsequently affects PMS angulation [15]. Many studies have found transverse asymmetries in the maxilla in both sexes, with unilateral mastication being the most frequent occurrence, resulting in greater expansion [16]. A previous study reported that most patients preferred chewing on the right side (78.3%) and were right-sided [17]. Thus, it can be concluded that masticatory preference may be similar to hand laterality, probably due to the dominant hemisphere of the brain [18], and that asymmetric development in certain brain regions may contribute to the development of asymmetric facial regions [19]. Regarding the maxillary sinus volume, no significant differences were observed between the right and left sides across age groups and sexes [20, 21]. Therefore, it can be assumed that the sharp edges of the osteotomes should be placed at larger angles between the PMS direction and the inferior portion of the vomer bone on the right side rather than on the left side to achieve optimal separation.
Our study has some limitations. First, the data of all participants were collected from a single medical center in Taiwan, which may have contributed to bias. Second, due to the retrospective design, we could not classify the patients into the three Angle’s classifications of malocclusion using only computed tomography. Hence, we cannot compare the differences among Angle’s classes I, II, and III.