A Straightforward Method of Predicting Enophthalmos in Blowout Fractures Using Enophthalmos Estimate Line

Abstract

Measuring the change in orbital volume may help to predict enophthalmos, but it is time consuming and difficult to apply. We devised a new and straightforward method with which to estimate the degree of enophthalmos. This retrospective cohort study was performed from January 2013 to December 2015. Patients who underwent initial computed tomography (CT) examination and surgical reconstruction in our hospital were selected. An imaginary line connecting the edges of the bony defects (defect line) was drawn on 2-dimensional CT images. The distance from the defect line to the farthest fracture segment or soft tissue was defined as the length of the enophthalmos estimate line. The length of this line was a predictor variable, and the degree of enophthalmos at 1week after the injury was an outcome variable. Age, gender, and type of injury are other variables that may affect the results. We statistically analyzed each variable using SPSS software (IBM, Armonk, NY). Of the patients, 22 had isolated inferior wall fractures, 14 had isolated medial wall fractures, and 17 had inferomedial wall fractures. There was high correlation between the length of the enophthalmos estimate line and the degree of enophthalmos in patients with isolated inferior fractures, medial wall fractures, and inferomedial wall fractures with internal orbital buttress fractures (Pearson correlation coefficient [r]= 0.783, r= 0.806, and r= 0.820, respectively). Approximately 2.0mm of enophthalmos was associated with 9.3- and 10.0-mm enophthalmos estimate lines in patients with isolated inferior wall fractures and medial wall fractures, respectively. The most important advantages of our method are its simplicity, convenience, and swiftness. Using only 2-dimensional CT images, we identified the correlation between the degree of orbital wall fracture and enophthalmos and calculated the predicted value of enophthalmos. This technique is expected to provide useful information to clinicians and patients to determine if an operation is needed.