Page 52 - Advanced concepts in orbital wall fractures
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Chapter 3
In orbital wall reconstruction, mirroring tools are often used with the assumption that the orbital cavities are an identical mirror image in volume and contour. This is one of the pillars of treatment planning. However, there is limited evidence on the extent to which contralateral orbital volumes and contours are identical. The purpose of this study was to assess the level of asymmetry in human unaffected orbits. The authors hypothesised that only minor asymmetry would exist in contralateral orbital cavities, which would support the rationale for using the mirroring technique. The specific aims of the study were to identify differences in volume and contour of the left and right bony orbits.
Materials and methods
Study design and sample
The authors designed and implemented a cross-sectional study to address the research question. The local ethics committee considered this study not subject to consent and the study was performed in accordance with the Declaration of Helsinki. A consecutive sample of patients was derived from a database of the Department of Radiology at the Academic Medical Centre (Amsterdam, the Netherlands). The study population was composed of adults who had undergone computed tomography (CT) examination of the brain without contrast in 2014 and 2015 for reasons other than orbital or sinus fracture or pathology. Scans were excluded when there were movement artefacts or when the facial skeleton was not completely visualised. The acquired CT scans (Siemens Sensation 64, Siemens Healthcare, Forchheim, Germany; Philips Brilliance 64, Philips Medical System, Best, the Netherlands) had a 0.75- to 1.0-mm slice thickness (512×512 matrix), 1.0-mm slice increment, 120 kV, 380 mAs, 0° gantry tilt, hard-tissue convolution kernel of H60s, and a window of W1600 and L400.
Study variables
The predictor variable was the orbital cavity. The left orbital cavity was compared with the right orbital cavity. The primary outcome variables were orbital volume and the contour of the orbital cavity. The other variables were age and gender.
