ROLE OF CT SCAN IN DIAGNOSING

SOFT TISSUE ENTRAPMENT IN ORBITAL FLOOR

FRACTURE

4th Journal club meeting 27-1-2009

Ophthalmology DepartmentKAUH

Mahmood J Showail

ORBITAL FLOOR FRACTURE  Fractures of the floor of the orbit,

sometimes known as "blowout fractures" typically occur when a small round object, such as a baseball, strikes the eye.

Mechanism of injury :

Increased intraocular pressure as the result posterior displacement of the globe(hydraulic theory)

A direct blow to the infraorbital rim

The most commonly fractured wall of the orbit is the floor *

* Lee HJ, Jilani M, Frohman L, Baker S. CT of orbital trauma. Emerg Radiol 2004;10:168 –72.

Among children, the floor of the orbit is more flexible. Consequently, it may fracture in a linear pattern that snaps back to create a "trap-door" fracture*.

In adults, the floor of the orbit is thinner and more likely to shatter when exposed to force*

* Jatla, KK, Enzenauer, RW. Orbital fractures: a review of current literature. Curr Surg 2004; 61:25.

Many clinicians advocate conservative management for most cases and reserve operative intervention for cases of entrapment with diplopia large fracture size with subsequent

enophthalmos.

A coronal computed tomogram demonstrates a fracture in the floor of the right orbit (black arrow). Entrapped orbital contents can be seen in the maxillary sinus (white arrow).

Extraocular muscle entrapment associated with an orbital floor fracture

The photograph demonstrates limitation of left upward gaze due to entrapment of the inferior rectus muscle.

  CT scan with coronal section is

particularly usfeul in evaluating the extent of the fracture .

It is used to determine the nature of maxillary soft tissue densities which may represent prolapsed orbital fat, extra-ocular muscles or heamatoma .

CT scans are ideal for imaging bones and therefore are good for evaluating the presence or absence of fractures;

however, they may not accurately image orbital soft tissue contents that may herniate into fracture sites.

BUTHOW ACCURATE IS

THE CT SCAN IN DETECTING SOFT

TISSUE ENTRAPMENT??

 

AND, IS THERE ANY DIFFERENCE IN THE

CONCORDANCE BETWEEN

RADIOLOGICAL AND INTRAOPERATIVE

FINDING IN PEDIATRIC AND ADULT POPULATION??

UNDERESTIMATION OF SOFT TISSUE ENTRAPMENTBY COMPUTED TOMOGRAPHY IN ORBITAL FLOOR FRACTURES IN THE PEDIATRIC POPULATION

Keshini C. Parbhu, MD, KoriAnne E. Galler, MD, Chun Li, PhD, Louise A. Mawn, MD

* American Academy of Ophthalmology 2008

PURPOSE: To compare the timing, radiologic, and

clinical indications for surgical management of orbital floor fractures in the pediatric and adult populations.

Design: Retrospective observational case series.

Participants: 24 pediatric and 31 adult patients who underwent primary repair of an orbital floor fracture.

The records of all patients presenting to the oculoplastics service for primary repair of orbital floor fracture over an 8-year period were reviewed.

METHODS

RESULTS: Pediatric orbital floor fractures were

repaired an average of 3 weeks earlier than adult fractures.

The most common clinical indication for surgery was entrapment in the pediatric group versus enophthalmia in the adult group.

The clinical indications cited for surgical intervention wereEntrapmentenophthalmia (2 mm) large fracture size > 50%

Clininal indications for surgery

Coronal CT scan of an adult patient with a 50% right orbital floor fracture. Soft tissue can be seen herniating through the floor defect

Coronal CT scan of a pediatric patient with a trapdoor fracture of the right orbital floor. The inferior rectus muscle is pulled toward the fracture site, and distinct lucency of orbital fat can be noted against the opacification from blood in the maxillary sinus.

CONT. RESULTS There was a significant underestimation

of entrapment reported on computed tomography (CT) in the pediatric group when compared with the clinical indications and intraoperative findings.

Conversely, there was good concordance between radiologic and intraoperative findings in the adult group.

P value

Concordance Rate (%)

IntraoperativeEntrapment

Radiologic Entrapment

Population

0.08 50 21 9 Paediatric Total 24 pt

0.0002

87 8 7 AdultTotal 31 pt

CONCLUSIONS: Pediatric orbital floor fractures are often of

the trapdoor type, which require earlier surgical intervention.

Entrapment and incarceration of orbital soft tissue contents as imaged by CT can be missed by radiologists. ( Our study demonstrates the poor concordance between radiologic and intraoperative evidence for entrapment in the pediatric population).

RECOMMENDATION It is important for the clinician to review

all radiologic studies and to perform a thorough ophthalmologic evaluation to correlate it with the radiological picture .

MRI is superior to CT scan in detection of soft tissue entrapment “in peadiatric or adult age group “.

THANK YOU