Page 59 - Advanced concepts in orbital wall fractures

Discussion
The purpose of this study was to assess left-versus-right differences in
orbital volume and contour. Small variations in symmetry of the face
were expected17,18,24. Only when an asymmetry develops past a certain
threshold does it become noticeable and potentially aesthetically
disturbing25. Restoration of orbital contours is important for functional
and aesthetic reasons. Orbital asymmetry can cause eye movement C disorders and a disharmonious facial appearance26. The results of this 3 study verify the use of the contralateral unaffected orbital cavity as
guidance for further treatment. The authors found that the measured differences between the right and left orbital volumes and contours were clinically minor.
The left-versus-right differences in orbital volume were small in nearly all 100 patients. The mean absolute volume difference of 0.44 ± 0.31 mL represents less than 2 % of the total volume. In 96 % of patients, the left-versus-right difference was less than 1 mL. The literature states that a 2 to 3 mL increase in bony orbital volume can result in a clinically visible enophthalmos of 2 to 3 mm on average27,28. Given these small variations in volume, the unaffected contralateral bony orbit in healthy humans is considered an acceptable reference in orbital reconstruction.
Of 100 patients, only four showed a left-versus-right difference larger than 1 mL; the largest difference was 1.65 mL. These asymmetries of the facial bones were visible in the three-dimensional reconstruction of the CT scans. This was due to a smaller contour of the orbital rim or differences in the anteroposterior position of the orbital rim, resulting in a smaller pyramidal base of the orbital cavity. In such a case and when an orbital floor or medial wall fracture is present, the surgeon should be able to notice this pre-existing asymmetry. In this case, the mirroring method should be used with caution, paying more attention to the anatomy of the fractured side. If these larger asymmetries go unnoticed in surgical cases, they could be responsible for postoperative enophthalmos or exophthalmos.
Virtual mirroring
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