Role of medial orbital wall morphologic properties in orbital blow-out fractures.

PURPOSE This study compares medial orbital wall supporting structures in patients with isolated inferior and medial wall fractures. METHODS The morphologic properties in all consecutive patients with periocular trauma who underwent orbital computed tomography (CT) scans from January 2004 to March 2006 were reviewed. On CT scans, the size of the fracture, the number of ethmoid air cell septa, and the length and height of the lamina papyracea were measured. RESULTS In 118 patients without orbital wall fracture, there were no bilateral differences in the measured structures. We took measurements from the opposite site in patients with fractures in whom it was difficult to visualize the structures at the fractured site. Seventy patients with medial wall fractures and 37 with inferior wall fractures showed no differences in sex, side of impact, etiology of the trauma, association with intraocular injuries, fracture size, anterior and posterior height, anteroposterior length, or the area of the lamina papyracea. In contrast, the number of ethmoid air cell septa was significantly lower (3.09+/-0.86 vs. 3.62+/-0.79, P=0.002) and the lamina papyracea area supported per ethmoid air cell septum was significantly higher (137.55+/-40.11 mm(2) vs. 119.64+/-38.14 mm(2), P=0.028) in patients with medial wall fractures than in those with inferior wall fractures. CONCLUSIONS Patients with fewer ethmoid air cell septa and a larger lamina papyracea area per septum are more likely to develop medial wall fractures than inferior wall fractures.