Orbital Volume Change Resulted from Packing in Ethmoidal Sinus for Correction of Isolated Medial Orbital Fractures

ABSTRACT

PURPOSE: Endoscopic transnasal correction of the medial orbital fractures cannot be enable to confirm the reduction degree of orbital volume without imaging modalities. We have intended through this study to make a quantative analysis of preoperative orbital volume increment and the reduction degree of that after ethmoidal sinus packing by using CT scan. METHODS: In this retrospective study, 22 patients were selected to evaluate the postoperative volume reduction, who took 2 CT scans which are pre- and postoperative under the same protocol. The postoperative CT scan was carried out in about 5 days after the operation with the packing inserted into ethmoidal sinus. The length of bony defect on each section was measured by PACS program and the area of defect was calculated by summing lengths on each section multiplied by the thickness of the section. When the outline of orbit on the slice is drawn manually with a cursor, PACS program measures the area automatically. Orbital volume was calculated from the sum of the area multiplied by the section thickness. RESULTS: The mean dimension of fractured walls was 2.86 +/-0.99 cm2. The mean orbital volume of the unaffected orbits was 22.89 +/-2.15 cm3 and that of the affected orbits was 25.62 +/-2.82 cm3. The mean orbital volume increment of the affected orbits was 2.73 +/-1.13 cm3. After surgery, the mean orbital volume of the unaffected orbits was 22.46 +/-2.73 cm3 and the mean orbital volume decrease on the surgical side was 2.98 +/-1.07 cm3. The estimated correction rate was 118.30%. CONCLUSION: The orbital volume increment in fractured orbit showed linear correlation with the dimension of fractured area. The orbital volume changes after ethmoidal sinus packing also showed linear correlation with orbital volume increment in fractured orbit. This study showed the regressive linear correlation between the increment of orbital volume and the correction rate. To evaluate the maintenance of reduction state, we think that the further study should be done for comparative analysis of orbital volume change after removal of packing.