Muscle shape as a predictor of traumatic enophthalmos.

The literature on enophthalmos is reviewed to understand its etiology and its prevention following orbital fractures. Specifically, the importance of muscle shape changes in predicting enophthalmos is discussed. The indications for surgical repair of orbital blowout fractures are well established. However, 7 to 10% of patients still develop enophthalmos despite these criteria. Because late repair of enophthalmos is associated with poor esthetic and functional results, the sensitivity and specificity of the current indications need to be further improved. Increased orbital volumes after fracture together with soft tissue displacement and herniation are the two most important factors causing enophthalmos. The loss of both bone and periorbita as supporting structures is seen on coronal computed tomography scan as changes in shape of the extraocular muscles. In floor fractures, the inferior rectus changes from an ellipse to a more rounded shape. The same is true for the medial rectus in medial wall fractures. It is the degree of rounding measured as a ratio of height to width that has been shown to be predictive of enophthalmos. Therefore, because rounding signifies loss of bone and soft tissue support, it may be a more important indication for surgical intervention than fracture size alone.