Localization of infraorbital foramen and accessory infraorbital foramen with reference to facial bony landmarks: predictive method and its accuracy

The infraorbital nerve block is used for mid-facial anesthesia. We aim to determine the location of infraorbital foramen (IOF) and accessory infraorbital foramen (AIOF) with reference to anterior nasal spine (ANS) and the lowest point of zygomaticomaxillary junction (Z) and assess the accuracy of the predictive method. Two hundred and sixteen dry skulls were examined. A reference line was drawn from ANS to Z (line A) and its length was measured (distance A). The location of IOF was predicted by using the mean vertical distance from IOF to line A (line B) which was 15.14 +/- 1.99 mm and the mean ratio of the distance between ANS and the intersecting point of line B and line A (distance D) to distance A (D:A) which was 63.35%+/- 3.90%. Eighty-six AIOFs were found. Most of them located superomedial to IOF, except for 3 AIOFs which located in the inferolateral position. For localization the AIOF, the mean vertical distance was 19.34 +/- 3.36 mm and the mean ratio was 51.8%+/- 5.90%. No statistically significant difference of the predicted distances for both foramens was found between sex and sides. The accuracy of the predictive method was assessed in 15 embalmed cadavers. Predicted IOFs were 50% accurate and the mean distance error of the predicted IOF was 1.10 +/- 1.44 mm lateral and 0.59 +/- 1.39 mm inferior to the exact IOF. Therefore, this study provides an alternative method for localization of IOF and AIOF which could be useful in clinical settings.