Anatomical study of the infraorbital foramen: A basis for successful infraorbital nerve block

Detailed knowledge of variations of the infraorbital foramen (IOF) and the establishment of a constant reference point for needle insertion are important for safe and successful regional block and for avoiding iatrogenic injury to the nerve during surgery in the midfacial region. Infraorbital foramina from 133 sides of 67 dry intact adult skulls of undetermined gender were examined for variations in shape, number, location in relation to bony landmarks, and relationship to the maxillary teeth. The angles of needle insertion in the sagittal and Frankfurt planes were determined. The infraorbital foramina were located at an average distance of 6.33 ± 1.39 mm below the infraorbital margin, 25.69 ± 2.37 mm from the median plane, 15.19 ± 1.70 mm from the lateral margin of the piriform aperture, and 28.41 ± 2.82 mm above the maxillary alveolar border. The average angles of needle insertion through the IOF with the sagittal and Frankfurt planes were 21.14° ± 10.10° and 31.79° ± 7.68°, respectively. Multiple foramina were found in 21% of the hemi-skulls. The foramen was less than 2 mm in size in 23.31% of the hemi-skulls. The position of the IOF with respect to the maxillary teeth varied from the interval between the canine and first premolar to the first molar, but in half of the specimens it lay in line with the second maxillary premolar tooth. The observations made in this study should be useful for planning infraorbital nerve block or surgery around the IOF.