Cone-beam computed tomography imaging analysis of anatomical landmarks and variations with surgical relevance in the Craniofacial Region

Abstract

Being familiar with pertinent anatomical landmarks and their variations before craniofacial surgical procedures is paramount to preventing and reducing perioperative complications. Currently, many of these anatomical landmarks and variations in presurgical planning have only been described using conventional radiography or computed tomography (CT). With the increasing application of cone-beam computed tomography (CBCT) in the craniofacial region, it is imperative to further evaluate these structures using this technique. Therefore, a series of studies that utilized CBCT were conducted to identify and evaluate the selected anatomical landmarks and variations in order to establish reproducible protocols that will be useful to head and neck radiologists, oral and maxillofacial surgeons, and otorhinolaryngologists.

First, a systematic review and meta-analysis on the prevalence and morphometry of anatomical variations of the mental nerve paths exiting the mandible was performed. Next, an exploratory study on the diagnostic accuracy of CBCT in the assessment of anatomical variations around the mental foramen (accessory mental foramina) was conducted using different CBCT devices and imaging modalities. Then, an analysis of CBCT scans to obtain linear and angular measurements that may ensure safety in Le Fort I osteotomy with tuberosity cut was done. Lastly, a CBCT imaging analysis of the prevalence of different ethmoid sinus variants and their associations with pathologies of the ethmoid and maxillary sinuses to improve the preoperative evaluation of sinus-related surgeries such as implant placement and functional endoscopic sinus surgeries in the Southern Chinese population was presented.

The systematic review and meta-analysis showed that the prevalence and morphometry of the mental nerve paths exiting the mandible varied tremendously among different populations, and minimal safety margins of 5 mm anterior and 8 mm inferior to the mental foramen may be more applicable on average among patients of different ethnicities. Also, the diagnostic study concluded that different CBCT devices exhibited good overall diagnostic accuracy for the detection of accessory mental foramina using different imaging modalities. The CBCT analysis for the safety of the Le Fort I osteotomy mainly recommended placing the osteotome along the buccal midpoint of the maxillary third molar or 4.4 mm distal to the second molar at an angle of 76.56° to the midsagittal plane or 92.31° to the buccal cortical plane. Then the last study reported a high prevalence of the ethmoid sinus variations in a Southern Chinese population with agger nasi cell and Onodi cell occurring more frequently. Also in this study, the presence of ethmoid sinus variations did not have a significant association with the occurrence of pathologies in the ethmoid sinus or maxillary sinus.

In conclusion, standardized cone-beam computed tomography analysis of surgical landmarks and variations is required for adequate preoperative evaluation. This study series has established reference standards for imaging and image analysis. This will prove useful in the presurgical evaluation of specific anatomical landmarks and variations in the mandible, maxilla, and ethmoid sinuses during dental implant placement, correction of maxillary anomalies using Le Fort I osteotomy, and functional endoscopic sinus surgery.