In a blowout fracture, which sign indicates orbital fat herniation into the maxillary sinus on plain radiographs?

• A. Open bomb-bay door sign
• B. Tear drop sign
• C. Moon sign
• D. Halo sign

Answer: (B)

In a blowout fracture, a key clue is the herniation of orbital fat through the fractured orbital floor into the maxillary sinus. On plain radiographs, this fat prolapse can appear as a teardrop-shaped density projecting into the sinus—the tear drop sign. This finding directly shows fat encroaching into the sinus through the orbital floor defect, which supports the diagnosis of an orbital floor blowout and helps explain symptoms like diplopia from inferior rectus entrapment. The other named signs do not depict this fat prolapse into the maxillary sinus, so they are not the characteristic radiographic marker for this injury.