Cone beam computed tomographic evaluation of infraorbital canal protrusion into the maxillary sinus and its importance for endoscopic surgery

Abstract Objective: The aim of this retrospective study is to investigate the prevalence of Infraorbital Canal Protrusion (ICP) degree into the maxillary sinus and its relationship with variations in adjacent structures on Cone Beam Computed Tomography (CBCT) images. Methods: 350 CBCT images (700 Infraorbital Canal [IC]) were evaluated retrospectively. ICP was divided into 3 subtypes according to the protrusion degree. The correlation between IC types and variations in adjacent anatomical structures (Haller cell, middle nasal concha pneumatization, maxillary sinus mucosal thickening and septa) was evaluated. The distance between Infraorbital Canal and Cnine Root (IC-CR) was also measured. For type 3, measurements were performed on IC as the length of the bony septum from the IC to the Mxillary Sinus Wall (IC-MSW), the distance from the inferior orbital rim, where the IC begins to protrude into the maxillary sinus (IOR-ICP), the vertical distance from the IC to the Maxillary Sinus Roof (IC-MSR) and Floor (IC-MSF). Results: The prevalence of type 1, 2 and 3 was 62.9%, 29.1%, and 8% respectively. IC-CR was 10.2, 10.7 and 11.4 mm in type 1, 2 and 3, respectively. IC-MSW, IOR-ICP, IC-MSRand floor IC-MSF was 3.8, 10.9, 7.4 and 27.7mm, respectively. On the right and left side, statistically significant correlation was found between IC types and the presence of the Haller cell and sinus septa. But there was no significant correlation between IC types and middle concha pneumatization. Conclusion: Accurate diagnosis of ICP is very important in preventing infraorbital nerve damage in surgical procedures to be performed in the maxillary region. The results of this study could be a guide for surgical planning in this region. Level of evidence: Retrospective study.摘要 目的：本回顾性研究旨在通过锥形束计算机断层扫描（Cone Beam Computed Tomography, CBCT）图像，探究眶下管上颌窦突出（Infraorbital Canal Protrusion, ICP）的发生率及其与邻近结构变异的关联。方法：回顾性评估350例CBCT图像（共700侧眶下管（Infraorbital Canal, IC））。根据突出程度将ICP分为3种亚型，并分析IC分型与邻近解剖结构变异（包括哈勒气房（Haller cell）、中鼻甲气化（middle nasal concha pneumatization）、上颌窦黏膜增厚（maxillary sinus mucosal thickening）及窦腔分隔）的相关性；同时测量眶下管与尖牙根之间的距离（IC-CR）。对于3型ICP，额外测量以下指标：眶下管至上颌窦壁（Maxillary Sinus Wall）的骨性隔长度（IC-MSW）、眶下管开始突入上颌窦处的眶下缘距离（IOR-ICP）、眶下管至上颌窦顶（Maxillary Sinus Roof）的垂直距离（IC-MSR）以及至上颌窦底（Maxillary Sinus Floor）的垂直距离（IC-MSF）。结果：1型、2型及3型ICP的发生率分别为62.9%、29.1%及8.0%。1型、2型、3型IC的IC-CR距离分别为10.2mm、10.7mm及11.4mm。3型ICP的IC-MSW、IOR-ICP、IC-MSR及IC-MSF分别为3.8mm、10.9mm、7.4mm及27.7mm。左右侧IC分型与哈勒气房、上颌窦分隔的存在均存在统计学意义上的相关性，但IC分型与中鼻甲气化无显著关联。结论：准确诊断ICP对于上颌区域手术中避免眶下神经损伤至关重要，本研究结果可为该区域的手术规划提供参考依据。证据等级：回顾性研究。