Evaluation of computer-based area and volume measurement from coronal computed tomography scans in isolated blowout fractures of the orbital floor.

Purpose: In this retrospective study, we evaluated isolated blowout fractures of the orbital floor by region-of-interest measurements from coronal computed tomography (CT) scans and their relationship to ophthalmologic findings.

Patients And Methods: Fracture area and volume of displaced tissue of blowout fractures in 38 patients were measured from coronal CT scans. Measurement was performed by identifying distances (for area calculation) of the fracture and identifying areas (for volume calculation) of the displaced tissue in each CT slice. The calculated data were then compared with the amount of enophthalmos, presence of diplopia, and limitation of ocular motility.

Results: Orbital floor area (mean +/- SD) was 5.72 +/- 1.07 cm(2); fracture area, 2.63 +/- 1.20 cm(2); and the volume of displaced tissue, 1.15 +/- 0.91 mL. The average proportion of the fracture within the orbital floor was 45.3 +/- 17.6%. Fracture area and volume of displaced tissue were significantly positively correlated with enophthalmos and diplopia and not correlated with the limitation of ocular motility. For enophthalmos of 2 mm or greater, mean fracture area (mean +/- SD) was 4.08 +/- 1.09 cm(2) and volume of displaced tissue was 1.89 +/- 1.19 mL; for less than 2-mm enophthalmos, 1.98 +/- 0.83 cm(2) and 0.83 +/- 0.58 mL, respectively. Enophthalmos of 2 mm can be expected with 3.38 cm(2) of fracture area and 1.62 mL of displaced tissue.

Conclusions: Region-of-interest measurement from coronal CT scan has an application in the assessment of patients with pure blowout fractures of the orbital floor and adds useful information in posttraumatic evaluation of orbital fractures.