CT assessment of orbital volume in late post-traumatic enophthalmos

The potential of CT to facilitate preoperative planning of reconstructive maxillofacial surgery by orbital volume quantification was analysed in 11 patients with traumatic enophthalmos as a late sequela of zygomatic fractures. We carried out biplanar CT examination of the orbits, and calculated total orbital and fat volumes for the healthy and enophthalmic sides. Displacement of the orbital floor and lateral wall was present in 11 and 7 cases respectively. Indentation of the medial wall was noted in 9 cases. Quantitative evaluation of the orbital cavity revealed a significant increase (P < 0.0188) in total volume on the enophthalmic side, the difference between the two sides ranging from 9.2% to 36.4%, mean 17.9%. The degree of enophthalmos, measured radiologically as 2.5-5 mm, correlated with the increase in orbital cavity volume (P = 0.000076). Enophthalmos was 2.5-3 mm in 7 cases (63.6%) and 3.5-5 mm in 4 (36.4%). This corresponded with a mean increase in orbital volume of 3.4 ml (12.3%) and 7.1 ml (27.8%) respectively. Fat atrophy was not an aetiological factor in the production of post-traumatic enophthalmos.