Location of the accessory infraorbital foramen with reference to external landmarks and its clinical implications.

The aim of this study was to define the location of the accessory infraorbital foramen (AIOF) with reference to accessible external landmarks in order to facilitate orbital and oculoplastic surgical procedures in the maxillofacial region. Forty-four hemifaces from 25 cadavers were dissected. The lateral canthus, subnasal point, and lacrimal caruncle were used as anatomic reference points. The AIOF was observed in 8 of the 44 hemifaces (18.2%) and was situated at a mean distance of 7.2 mm superomedial to the IOF. The horizontal distance from the lacrimal caruncle to the AIOF was 0.3 mm. In all cases the AIOF was situated at a point that was no more than 8 mm from the intersection point of a vertical line passing through the lacrimal caruncle and an oblique line joining the lateral canthus and the subnasal point. Surgeons anesthetizing or performing surgical procedures in the maxillofacial region should be aware of the frequency of the AIOF (18.2%) and its location (on the superomedial side of the IOF). We propose that injecting at the intersection point of a vertical line passing through the lacrimal caruncle and an oblique line joining the lateral canthus and the subnasal point would successfully block the accessory branch of the infraorbital nerve. Likewise, surgeons operating in this region should be aware of the location of the AIOF in order to avoid inadvertent iatrogenic injury to a duplicated infraorbital nerve.