Vỡ sàn ổ mắt dạng cửa sập ở trẻ em – tổn thương dễ bị bỏ sót Pediatric trapdoor orbital floor fraCTure – an easily missed injury

A trapdoor orbital floor fracture is a distinctive form of orbital trauma that occurs predominantly in children and young patients. Unlike many conventional orbital fractures, external signs may be minimal even when extraocular muscle or orbital soft tissue has become entrapped within the fracture line.

Because of this mismatch between the relatively normal external appearance and the potentially serious underlying injury, the condition is also commonly associated with the term white-eye blowout fracture.

This is a type of injury in which a careful examination and recognition of subtle clinical signs can completely change the treatment strategy.

When an orbital floor fracture appears not to require surgery

The patient was a young boy referred from another hospital with a diagnosis of right orbital floor fracture.

Patients with orbital fractures may present with pain, periorbital swelling, subconjunctival hemorrhage, restricted ocular movement, and diplopia. CT imaging may demonstrate disruption of the orbital wall, displacement of bone fragments, or herniation of orbital soft tissue.

However, not every orbital floor fracture requires surgical treatment. In cases without tissue entrapment, significant ocular motility disturbance, persistent diplopia, globe displacement, or substantial alteration of orbital volume, conservative management may be appropriate depending on the overall clinical situation.

In this patient, the initial findings were surprisingly subtle.

He experienced pain during examination but did not report obvious diplopia. Ocular motility appeared almost normal on routine assessment. CT demonstrated a fracture of the orbital floor, but the bony displacement was limited and the overall orbital volume appeared largely preserved.

Based on these findings alone, the injury could easily have been interpreted as an orbital floor fracture that did not require surgery.

Subtle findings that changed the diagnosis

On more detailed examination, however, the right eye showed a slight limitation of upward gaze compared with the left side. The difference was subtle and only briefly apparent, particularly because the young patient was not consistently cooperative during examination.

The history provided another important clue.

During the approximately six hours between the accident and hospital admission, the patient had experienced nausea, vomiting, and headache.

In a child with orbital trauma, these symptoms should raise concern for an oculocardiac reflex associated with entrapment of an extraocular muscle or orbital soft tissue.

CT provided an additional clue. Although the orbital floor fracture itself appeared relatively limited, the inferior rectus muscle was positioned close to the fracture line and appeared more rounded than its normal horizontally elongated configuration. This suggested downward traction on the muscle and surrounding orbital tissues.

Taken together—the mechanism of injury, subtle limitation of upward gaze, systemic symptoms, and CT findings—these features strongly suggested a trapdoor orbital floor fracture.

Why is a trapdoor fracture potentially dangerous?

In children and young patients, the orbital bones are relatively flexible and elastic.

Following trauma, a portion of the orbital floor may temporarily displace downward, allowing muscle and soft tissue to prolapse through the fracture. Because of the elasticity of the bone, the fragment may then spring back toward its original position, trapping the prolapsed tissues within the fracture.

For this reason, CT may show only a small fracture with little change in orbital volume. Externally, there may also be relatively little swelling or bruising.

Despite this apparently mild presentation, extraocular muscle and orbital soft tissue may be tightly entrapped and subjected to ischemic injury.

This is what distinguishes a trapdoor fracture from many conventional orbital floor fractures. When muscle or soft-tissue entrapment is suspected, particularly in association with ocular motility restriction or features of the oculocardiac reflex, urgent surgical release should be considered to minimize the risk of persistent muscle dysfunction and long-term diplopia.

Urgent surgical release

The patient underwent urgent surgery shortly after admission.

Before the incision was made, a forced duction test confirmed mechanical restriction of upward movement of the right eye, supporting the diagnosis of tissue entrapment.

After exposure of the orbital floor, the entrapped tissue was identified and completely released.

The orbital floor was then reconstructed with a titanium mesh. At the end of the procedure, the forced duction test was repeated and demonstrated free movement of the right globe.

A small fracture does not necessarily mean a minor injury

Trapdoor orbital floor fracture is an important example of how the degree of bony displacement on imaging does not always reflect the true severity of an orbital injury.

Particularly in children, minimal swelling, absence of obvious diplopia, and a subtle fracture on CT do not exclude clinically significant extraocular muscle entrapment.

Assessment of orbital trauma should therefore combine careful ocular motility examination, detailed evaluation of post-traumatic symptoms, and meticulous CT interpretation, rather than relying on fracture size alone.

During my training in maxillofacial trauma, I had the opportunity to study orbital wall fractures in depth and was specifically taught to recognize uncommon patterns such as this one. Knowledge that may initially seem purely academic can become critical when a subtle sign determines whether an injury is recognized and treated at the appropriate time.

My sincere thanks also go to the doctors at Hung Ha Hospital, who identified the orbital injury at the initial assessment and appropriately advised the family to bring the patient to Hanoi for further evaluation and treatment.