Correct Answer: C. Blow out fracture
A blowout fracture is an orbital floor fracture caused by blunt trauma to the eye, where the orbital contents herniate through the fracture site into the maxillary sinus below. The classic clinical triad—diplopia, epistaxis, and restricted eye movements—directly reflects this pathophysiology. Diplopia occurs due to enophthalmos (posterior displacement of the globe) and vertical diplopia from entrapment of the inferior rectus muscle in the fracture line, causing restricted upward gaze. Epistaxis results from mucosal tearing in the maxillary sinus during the fracture. The restricted eye movements, particularly limitation of upward gaze, are pathognomonic and occur because the inferior rectus becomes trapped or scarred in the fracture defect. On CT imaging, you will see a "hanging drop" sign—herniation of orbital fat and inferior rectus muscle into the maxillary sinus through the floor defect. This is the most common orbital fracture in trauma cases. Management depends on severity: small fractures with minimal enophthalmos and no muscle entrapment are observed; symptomatic cases with significant enophthalmos (>3 mm) or acute muscle entrapment require surgical repair via transantral or endoscopic approach within 2 weeks to prevent permanent diplopia.
Why the other options are wrong
A. Fracture maxilla — Maxillary fractures (Le-Fort types) present with midface instability, malocclusion, and facial swelling rather than isolated orbital signs. While maxillary fractures may involve the orbital floor secondarily, they are characterized by bilateral facial trauma and involve the nasomaxillary complex. The clinical presentation here—isolated diplopia with restricted upward gaze—is too focal for a primary maxillary fracture, which would show broader midface involvement on imaging. B. Fracture zygomatic — Zygomatic fractures cause malar flattening, infraorbital nerve paresthesia, and trismus (from masseter muscle involvement), not the vertical diplopia and upward gaze restriction seen here. While zygomatic fractures can involve the lateral orbital wall and cause enophthalmos, they do not typically trap the inferior rectus muscle. The restricted upward gaze is the discriminating sign pointing to inferior rectus entrapment, which is specific to orbital floor fractures. D. Le-fort fracture — Le-Fort fractures are bilateral midface fractures involving the nasomaxillary-pterygoid complex, presenting with floating maxilla, severe facial swelling, and malocclusion. They do not cause the isolated orbital floor defect that produces inferior rectus entrapment. The clinical triad of diplopia with upward gaze restriction is too specific for orbital floor involvement to be explained by a Le-Fort pattern, which would show more extensive midface trauma on imaging.
High-Yield Facts
- Blowout fracture = orbital floor fracture with herniation of orbital contents into maxillary sinus; most common orbital fracture after trauma.
- Vertical diplopia + restricted upward gaze = inferior rectus muscle entrapment in fracture line; pathognomonic for blowout fracture.
- 'Hanging drop' sign on CT = herniated orbital fat and inferior rectus muscle prolapsing through floor defect into maxillary sinus.
- Enophthalmos >3 mm or acute muscle entrapment = surgical indication; repair within 2 weeks prevents permanent diplopia.
- Epistaxis in orbital trauma = mucosal tearing in maxillary sinus during floor fracture; not seen in zygomatic or maxillary fractures in isolation.
Mnemonics
BLOWOUT = Orbital FLOOR fracture Blunt trauma → Loor fracture → Orbital contents herniate → Wupward gaze restricted (inferior rectus trapped) → Ophthalmoplegia → Upward gaze loss → T = Trapped muscle. Remember: 'blowout' = contents blow OUT through the floor INTO the sinus below. FRED mnemonic for orbital fractures Floor (blowout) = vertical diplopia + upward gaze restriction; Rim = lateral wall fracture; Ethmoid = medial wall fracture; Dome = roof fracture. Use this to differentiate which orbital wall is fractured based on gaze restriction pattern.
NBE Trap
NBE pairs maxillary fracture with orbital involvement to trap students who confuse the broader midface trauma pattern of Le-Fort/maxillary fractures with the focal orbital floor defect of blowout fractures. The key discriminator is isolated inferior rectus entrapment causing vertical diplopia with upward gaze restriction—this is pathognomonic for blowout fracture, not maxillary fracture.</trap> <parameter name="textbookRef">Bailey & Love Ch. 42 (Orbit); Harrison Ch. 428 (Neuro-ophthalmology); Robbins Ch. 29 (Eye pathology)
Clinical Pearl
In Indian emergency departments, blowout fractures are commonly missed because clinicians focus on epistaxis and assume maxillary fracture. The key bedside test is the "upgaze test"**—ask the patient to look up; if they cannot and report vertical diplopia, suspect inferior rectus entrapment and order orbital CT immediately. Early recognition within 2 weeks allows endoscopic repair, preventing permanent diplopia that can be socially disabling in Indian patients.