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Prediction of Enophthalmos by Computer-Based Volume Measurement of Orbital

Fractures in a Korean Population

Ahn HB, et. al. Ophthalmic Plastic and Reconstructive Surgery. 2008 ；24 ： 36–9.

Presenter: Che-Hao Chuang

Professor: Dr. Yen-Ting Chen

Date: 2009/12/08

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Outline

IntroductionProblems and RationalePurpose

Materials and MethodsResultsDiscussionsConclusionsFuture worksReference

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IntroductionProblems and Rationale

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Problems and Rationale (1/7)

Orbital blow-out fractures are frequent due to popularity of motorcycle traffic accident.

Orbital blow-out fracture: 眼窩骨折

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Problems and Rationale (2/7)

An orbital fracture due to trauma can induce complications:

EnophthalmosOcular motility limitationDiplopiaOrbital emphysemaInjury to the inferior orbital nerveVision loss

Enophthalmos: 眼球內陷 Ocular motility limitation: 眼睛的能動性限制 Diplopia: 複視 Orbital emphysema: 眼窩氣腫

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Problems and Rationale (3/7)

Recognized sequelae of orbital blow-out fracture include:

Diplopia Enophthalmos

sequelae: 後遺症

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Problems and Rationale (4/7)

Pathology Two images of a single

object

Displace Horizontally Vertically Diagonally

1. Monocular diplopia

2. Binocular diplopiaDiagram of Diplopia

Monocular diplopia: 單眼複視 Binocular diplopia: 雙眼複視

Diplopia (Double vision)

From:http://www.clinico.com.tw/eye1/eye12/eye126/I126l.htm

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Problems and Rationale (5/7)

EnophthalmosPathology:

The displacement backward of eyeball The difference of eyes retraction is more than

2mm (3 to 4mm or more).Congenital: Primary enophthalmos

Facial asymmetry & DysplasiaPostnatal: Secondary enophthalmos

Origin: caused by the reduction of orbital contents or increase of volume of orbit cavity

From: http://blog.udn.com/jnwu/2937626

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Problems and Rationale (6/7)

The most common fracture sites:Orbital floorMedial wall

An assessment of the fracture in the orbit and the ethmoidal sinus:CTClinical findings

Medial wall

Orbital floor

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Problems and Rationale (7/7)

The underlying cause of enophthalmos:A discrepancy between the volume of the orbital

soft tissue and the bony orbital cavity

Displacement of the orbital tissue from the bony orbit:Entrapped tissueFat necrosisPosterior soft-tissue fibrosis

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IntroductionPurpose

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Purpose (1/2)

Enophthalmos > 2.0 mm

Surgical intervention

During the acute posttrauma periodIt is difficult to predict the degree of enophthalmos

accurately.It may be underestimated.

Orbital edema

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Purpose (2/2)

Using computer-based measurement EnophthalmosVolume of an orbital wall fracture

It may be beneficial in predicting indications for surgery.

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Materials and Methods

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Materials and Methods (1/6)

Sample of research: Thirty-five Korean patients with orbital blowout

fractures who were not treated with surgery.

Exclude criteria:Bilateral orbital wall fractureLateral wall and roof fractureInadequate CTAge less than 18 yearsSurgical repair of the fracture

Lateral wall: 外側壁

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Materials and Methods (2/6)

In 35 patients 25 patients

A fracture in the medial wall of the orbit 2 patients

A fracture in the inferior wall 8 patients

A combined fracture in the medial wall and inferior wall

CT scanning system: SOMATOM Sensation 16

Image processing systemRapidia: CT or MRI 3D image

Medial wall

Inferior wall

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Materials and Methods (3/6)

3mm

Measurement of the fracture area and volume (A–F)

Vol = A x 3 mmUnit:

3 mm: Section thickness

3mm

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Materials and Methods (4/6)

Pearson correlation coefficient (r)Consecutive correlation

between two variables-1 ≦ r ≦ 1, r > 0, positive correlation

r < 0, negative correlation

r = 0, no correlationFracture volume and late

enophthalmos

Linear regression analysisThe relationship between

Two consecutive variables

The prediction of late enophthalmos

Statistical softwareSPSS

Statistical analysis

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Materials and Methods (5/6)

Experimental cycle of Ophthalmic examination: First day One week One month Three months later

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Materials and Methods (6/6)

Examination:1. Visual acuity

2. Slit lamp examination

3. Pupillary reflex test

4. Goldmann diplopia test by perimetery

5. Extraocular motility measurement

6. Hertel ophthalmometry to measure enophthalmos

Slit lamp: 裂隙燈 Extraocular motility: 眼外能動性

Pupillary reflex: 瞳孔反射 Hertel ophthalmometry: 赫特爾突眼計

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Results

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Results (1/7)

The patient's gender classification Men: 28 of 35 patientsWomen: 7 of 35 patients

The patient‘s age classificationMean age: 37.06 yearsLess than 50 years: 31 of 35 patients

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Results (2/7)

Age and gender distribution

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Results (3/7)

Fracture volume and enophthalmos

0 - 1.0 (ml) 54.3%

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Results (4/7)

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Results (5/7)

Mathematical formula of linear regression analysis:

E = enophthalmos (mm)

V = fractured site volume (ml)

SEE = standard error of estimate

It was used to calculate the expected degree of late enophthalmos.

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Results (6/7)

Volume of the orbital fractureLess than 1 ml 0.91 mm2 ml 1.74 mm

Depth of enophthalmos2 mm 2.30 ml0.84 mm for every 1.0 ml increase in volume

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Results (7/7)

Amount of late enophthalmos predicted from the fracture volume

Enophthalmos of 2 mm or more was predicted with an orbital fracture volume of 2.30 ml.

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Discussions

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Discussions (1/5)

Why use CT?Many studies have mentioned

E.X. Gilbard et al.

Best means of observing the bone structure and soft tissues of the orbit.

It’s great help in predicting the prognosis of a patient with a fracture in the orbital floor.

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Discussions (2/5)

Interrelated studiesTo predict enophthalmos after an orbital fracture,

per ml increase in the orbital volume.Raskin et al. 0.47 mm (per ml)Whitehouse et al. 0.77 mm (per ml)Ploder et al. 0.81 mm (per ml)Fan et al. 0.89 mm (per ml)

However, less studies that focused on orbital fracture patients without surgical treatment.

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Discussions (3/5)

Attentive itemCompared with the orbital volume of the normal eye

A tilted head positioning during CT scanning

Normally, the volume between the right and left orbit may differ by approximately 7% to 8%.

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Discussions (4/5)

In the present studyMeasuring the volume of the orbital fracture

site.Source: the consecutive coronal CTRapidia software

2D 3DArea and volume

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Discussions (5/5)

Predicted benefitsDecrease mistake

Surgical repair is not always necessary in the treatment of orbital fractures.

Underestimation of the amount of late enophthalmos

It won’t delay with surgery.

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Conclusions

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Conclusions (1/1)

A significant correlationThe fracture site volume and the degree of late

enophthalmos.

Predicting overall enophthalmos and provide useful information to surgeons.

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Future works

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Future works (1/1)

Proof of orbital symmetryFind out the relevant parametersIncrease the number of sampleStatistical verification

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Reference

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Reference (1/1)

Ahn HB, et. al. Prediction of Enophthalmos by Computer-Based Volume Measurement of Orbital Fractures in a Korean Population. Ophthalmic Plastic and Reconstructive Surgery. 2008 ； 24 ： 36–9.

From:http://www.clinico.com.tw/eye1/eye12/eye126/I126l.htm

From:http://blog.udn.com/jnwu/2937626

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Thank you for your attention