Finding the Ledge: Sagittal Analysis of Bony Landmarks of the Orbit

Abstract

This study determined the average distances and angles between anatomic landmarks within the orbit, with an emphasis on localization of the orbital process of the palatine bone. This information will help the surgeon with treatment planning and surgical procedures. Four anatomic landmarks were identified retrospectively on computed tomograms of 100 adult Caucasian patients (50 men and 50 women): the top of the infraorbital margin superior to the infraorbital foramen (point A), the top of the orbital process of the palatine bone (point B), the anteriormost bony portion of the superior orbital fissure (point C), and the ventrolateral aspect of the bony entrance of the optic canal (point D). The distances between these points were measured, as were the angle between the medial wall of the orbit and a line connecting points A to D at the level of the optic nerve. The mean distances between the orbital rim (point A) and the orbital process of the palatine bone (point B) were 33.8mm in men and 32.7mm in women. Men had markedly larger bony orbits than women; however, women had a larger angle than men for the 2 orbits. Obtaining these measurements preoperatively can enable a safer and more predictable surgical approach to the orbit, which can help lower the risk of damaging important neighboring structures. A preformed reconstruction plate can be manufactured or a standard reconstruction plate can be customized according to these measurements; during reconstruction, they also can help adequately localize the posterior ledge, specifically the orbital process of the palatine bone. These 2 aspects could ensure a more precise reconstruction of the orbital floor.