The Effectiveness of MRI in Blow Out Fracture

ABSTRACT

The blowout fracture needs early diagnosis and active treatment if the fracture site, the degree of injury and herniation of orbital soft tissue are identified. It is more important than diagnosis itself that doctors identify the combined injury of orbital structures such as fat herniation and entrapment of the extraocular muscle with radiologic methods. Computed tomography(CT) is the standard method in the diagnosis of blowout fracture today, but with this method herniated orbital fat or extraocular muscle is not well differentiated from hematoma in case of the minimal blowout fracture. MRI(magnetic resonance image) was taken for further evaluation of extraocular muscle and orbital fat in 20 patients(16 males, 4 females) among 58 patients who were suspected or diagnosed as blowout fracture on simple X-ray or CT view. Fractured sites were located on the medial wall in 4 patients, orbital floor in 6 patients. 10 patients suffered from the blowout fracture on more than 2 walls. In 18 of total 20 patients, the herniation of orbital fat or extraocular muscle was identified on MRI view. In 2 patients whose orbital soft tissue was not herniated, the fracture was observed on CT view but not observed on MRI view. In case of suspicious hematoma or herniation of orbital soft tissue within maxillary sinus, CT view could not identify the hematoma or herniation of orbital soft tissue, but oblique sagittal MRI view could identify the herniation of inferior rectus muscle and differentiation of the herniation of orbital soft tissue from hematoma within maxillary sinus on T1 and T2-weighted images. In 7 patients who were difficult to decide the operative indication on CT view, MRI identified herniation and entrapment of extraocular muscle. MRI is especially useful when you differentiate hematoma from herniated orbital fat or extraocular muscle in case of minimal blowout fracture. MRI is useful in deciding the operative method and evaluating the soft tissue involvement in case of blowout fracture.