Localization Chulalongkorn University of the infraorbital foramen and the accessory infraorbital foramen with reference to facial bony landmarks: the predicting method and its accuracy.

Abstract

The infraorbital nerve block is commonly used for mid-facial anesthesia. Therefore, the location of infraorbital foramen (IOF) and accessory infraorbital foramen (AIOF) where the nerve exits through is important. Although, many studies tried to identify the location of IOF and AIOF using bony and soft tissue landmarks, the results varied in each study. Objectives To determine the location of IOF and AIOF with reference to the line between anterior nasal spine (ANS) and the lowest point of the zygomaticomaxillary junction (Z) which is defined as line A, describe anatomical relationship between IOF and AIOF, and assess an accuracy of the proposed predicting method. Methods A total of 216 skulls were examined. Live images were analyzed under the stereoscopic microscope. For localization of IOF, the vertical distance from IOF to line A (B) and the mean ratio of the distance between ANS and the intersecting point of the vertical line from IOF with line A (D) to distance A were analyzed. If AIOF was identified, all distances were measured similar to IOF. To assess an accuracy of the predicting method, 15 cadavers were studied by measuring the distance error between the predicted and the real foramen. Results There were 86 AIOFs. Most of them located superomedial to IOF except for 3 AIOFs which located in the inferolateral position. The location of IOF was predicted by using the vertical line B which was 15.14 ± 1.99 mm and the mean ratio of distance D to distance A (D:A) which was 63.35 ± 3.9%. For localization of AIOF, the mean vertical distance was 19.34 ± 3.36 mm and the mean ratio was 51.8 ± 5.9%. No statistically significant difference was found between sex and sides. In cadavers, the mean distance error of the predicted IOF was 1.10 ± 1.44 mm lateral and 0.59 ± 1.39 mm inferior to the real IOF and there were 50% of the predicted IOFs that accurately located within the real IOF. Therefore, this study provides an alternative method for localization of IOF and AIOF which could be useful in clinical settings.