The missing rectus: a CT observation from blow-out fracture of the orbital floor.

A patient with a blow-out fracture of the right orbital floor presented with impediment of the inferior rectus muscle. Coronal CT disclosed a lateral hinged fragment from the orbital floor and herniation of intrabulbar content into the maxillary sinus. The inferior rectus muscle could not be identified intraorbitally in three sequential 3 mm coronal sections and it was concluded that the muscle was incarcerated, a presumption that was verified at surgery.