2D- and 3D-based measurements of orbital floor fractures from CT scans

Objective: Two methods for area and volume calculation of the orbit were evaluated following blow-out fractures of the orbital floor using computed tomography (CT) scans. Material and Methods: Isolated blow-out fractures of the orbital floor in human cadavers were simulated by fracturing the orbital floor and placing a defined volume of silicone within each defect. The area of fracture and the volume of silicone simulating herniated periorbital tissue were evaluated in 16 orbits by the use of a three-dimensional (3D) CT-based software package (Analyze®; Mayo Clinic, Rochester, MN, USA) and software based on two-dimensional (2D) coronal CT scans. Both methods were compared with direct anatomical measurements and evaluated with Lin's concordance coefficient (ρ_c). Results: Between-method concordance of area and volume calculation were ρ_c=0.962, and 0.872 for the 3D-CT-based method, and 0.981 and 0.952 for the 2D-CT method, respectively. The time allocated for measurement was significantly longer for the 3D-CT than for the 2D-CT method (p<0.001). Conclusion: Calculations of blow-out fractures of the orbital floor by 3D-CT and 2D-CT method are accurate for assessing the area of fracture and the volume of herniated tissue. Lesser processing time and simple usage favour the 2D-CT-based calculation method.