Orbital Floor Fracture with Entrapment: A Common Cause of Clinical & Radiographic Error

Abstract

 

Purpose:

 

A common misconception is that the inferior rectus (IR) must be trapped in an orbital floor fracture (OFF) to give entrapment. Rather, entrapment occurs when any orbital tissue is trapped due to the septa coursing the orbit and in intimate relation to the IR (Fig 1). Patients with entrapment may have painful supraduction, nausea/vomiting, or oculocardiac reflex signs such as bradycardia. We study how often OFF with entrapment is missed by clinicians, and the resulting sequelae.

 

Methods:

 

Records of 9 patients with OFF and entrapment were reviewed.

 

Results:

 

6 males and 3 females had a median age of 16 years (range 7-27, Table 1). The mean duration from trauma to evaluation was 4 days (0.25-13). 4 cases were evaluated by an ophthalmology resident, with 2 (50%) correctly diagnosed and 2 (50%) in whom entrapment was missed. Entrapment was correctly described on the CT radiology report in 1 case (13%), and missed in 7 cases (87%), while case #2 was evaluated prior to the advent of CT. 4 cases had IR entrapment (44%), while 5 (56%) had orbital fat entrapment.

 

Conclusions:

 

When evaluating a patient with an OFF it is vital to assess the possibility of entrapment as this is an emergency, and delay in diagnosis may lead to persistent diplopia, bradycardia, or death. Clues that aid in diagnosis include nausea/vomiting, bradycardia, painful & limited supraduction, restriction on forced ductions, and trapdoor fractures entrapping orbital tissues on coronal CT (especially in children). A key imaging concept is that entrapment occurs when any orbital tissue is trapped in the fracture. Radiologists missed entrapment in this study in most cases, and clinicians must maintain a high degree of suspicion when warranted.  

 

 

Keywords: extraocular muscles: structure • imaging/image analysis: clinical • trauma