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Orbital Fractures: Role of Imaging
Orbital Fractures: Role of Imaging Ferdinando Caranci, MD,* Domenico Cicala, MD,* Salvatore Cappabianca, MD,† Francesco Briganti, MD,* Luca Brunese, MD,‡ and Paolo Fonio, MD§ The orbit may be injured directly or indirectly. Blunt and penetrating trauma occurs with equal frequency. Soft tissue swelling often obscures direct clinical evaluation of the globe, limits ocular motion, and may limit clinical assessment of vision. Plain film radiographs of the orbits and sinuses are rarely used for diagnosis in orbital trauma. Computed tomography is considered the imaging modality of choice in this circumstance, as it is deemed to be the most accurate method in detecting fractures. The protocol is based on obtaining thin-section axial scans and multiplanar reformatted images, both are useful tools to guide treatment. Orbital fractures are not considered an ophthalmologic emergency unless there is visual impairment or globe injury. Surgical repair is indicated for patients who have persistent diplopia or cosmetic concerns (enophthalmos) and generaly is not performed until swelling subsides 7-10 days after injury. Semin Ultrasound CT MRI 33:385-391 © 2012 Elsevier Inc. All rights reserved.
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rbital fractures have a widely variable presentation and clinical severity. The anatomic complexity of the orbital and intraorbital structures also creates confusion. Orbital fractures differ from all other facial fractures in that surgery does not typically attempt to achieve bone healing but instead aims to reconstruct the defective area of the fractured wall, restoring the original shape of the orbit.1 Thus, delaying the operation for varying periods is feasible and often recommended. Resolution of orbital swelling or hemorrhage, and reduction of their influence on the clinical course, facilitates accurate diagnosis and strengthens the indications for surgery.1-4 Ophthalmologic counseling is crucial,2,5 but physical examination might be difficult because of the altered condition of the wounded eye; moreover, the patient may be unable to cooperate.6 In these cases, the diagnosis is limited to radiologic examination, which provides guidance for the maxillofacial surgeon. Therefore, the radiologist’s role is crucial in the early detection of the findings that can result in esthetic deformities and functional deficiencies. Medicolegal issues must not be overlooked.
*Department of Diagnostic Radiology and Radiotherapy, Federico II University of Naples, Naples, Italy. †Institute of Radiology, Second University of Naples, Naples, Italy. ‡Department of Health Science, Chair of Radiology, University of Molise, Campobasso, Italy. §Institute of Radiology, University of Turin, Turin, Italy. Address reprint requests to Ferdinando Caranci, MD, Department of Diagnostic Radiology and Radiotherapy, Federico II University of Naples, Via Boccaccio 2, 80123 Naples, Italy. E-mail: [email protected]
0887-2171/$-see front matter © 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1053/j.sult.2012.06.007
Radiographic examination of the orbits is rarely performed; ultrasonography can be very useful for evaluating the globe and its contents, but it is contraindicated if a ruptured globe is suspected.6 Computed tomography (CT) is considered the imaging modality of choice in evaluating orbital trauma, and it is the most accurate method in detecting fractures.2,6,7,8 Protocols include thin-section axial CT scans as well as multiplanar reformatted images. Both are useful tools to guide treatment.6,9,10 In addition to its primary role in the evaluation of the fractures, CT may also provide information for the detection of soft-tissue injuries. Magnetic resonance imaging (MRI) may be difficult to be perform in emergent conditions and is contraindicated if there is the possibility that a metallic intraorbital foreign body is present.6 Therefore, it is not recommended in the initial evaluation of the trauma, although MRI ultimately can provide useful detailed information.
Imaging of the Orbital Fractures Orbital fractures can be isolated but are more commonly associated with other midface fractures, such as posterior propagation of naso-orbito-ethmoid fractures (medial orbital wall) and zygomaticomaxillary complex fractures (orbital floor, lateral orbital wall). Fractures of the orbital skeleton may also occur in Le Fort II complex (medial wall and floor) and Le Fort III complex (medial wall, posterior orbital floor, lateral wall).11 Detailed knowledge of the anatomy of the orbit is required, including bone laminae and recesses. Supraorbital and infraorbital foramina should not be misinterpreted as fractures. Blow out fractures are the most common. They are caused by 385
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Figure 1 Blow out fracture of the orbital floor. Coronal nonenhanced-reformatted computed tomography (CT) image. Left orbital floor fracture without evidence of entrapment of the inferior rectus muscle, which remains flattened in cross-sectional appearance, indicating integrity of the fascial support of the globe.
increased intraorbital pressure because of direct orbital blunt injury, which causes a break of the orbital walls at their weakest point.2,11 These fractures are differentiated into pure or impure type depending on the involvement of the orbital rim. Blow in fractures are less frequent; they result from direct injury to the paranasal sinus region with centrifugal displacement of bone fragments.11
Orbital Floor Fractures The orbital floor and medial wall are relatively thin; therefore, they are more vulnerable and frequent sites of frac-
Figure 2 Blow out fracture of the orbital floor. Coronal nonenhanced-reformatted CT image. Left orbital floor fracture, with the inferior rectus attracted inferiorly toward the maxillary sinus; the cross-sectional appearance of the muscle has changed from flattened to ovoid, indicating entrapment because of disruption of the fascial support.
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Figure 3 Medial wall fracture. Axial nonenhanced CT image. The right lamina papyracea has collapsed toward the midline, causing an increase of the orbital volume (without enophthalmos); the ipsilateral medial rectus maintains the typical flattened profile without herniation into the fracture site. Lateral orbital wall fractures are present bilaterally.
ture.2 In these cases, there is a strong potential for diplopia because of entrapment of inferior and medial rectus muscles. To plan adequate medical and surgical treatment, CT scanning is required to evaluate the shape and position of these muscles.1,11 In case of orbital floor fracture, it is mandatory to evaluate the shape and position of the inferior rectus muscle and of orbital adipose tissue on coronal and sagittal CT reconstructions. The study can provide information regarding entrapment of the inferior rectus muscle and the fascial sling of the globe, directly correlating with diplopia and vertical restriction. On cross-section images, if the inferior rectus remains flattened and in the correct position (Fig. 1), the fascial sling is likely intact and the surgeon will encounter minimal entrapped periorbital tissue. If the inferior rectus has a rounded shape and is inferiorly displaced, the fascial sling is likely compromised, leading to periorbita and muscle prolapse through the orbital floor defect (Fig. 2).11 Infraorbital groove (nerve) involvement often occurs in orbital floor fractures with consequent sensory dysfunction.2,5 A large wall defect can be associated with increase of the orbital volume resulting in enophthalmos.1,2 Entrapment of the inferior rectus in children may be easily missed or underestimated. The flexible pediatric bone springs back into place after injury covering the traumatic defect like a “trapdoor.” This results in a normal appearance at CT except for the infraorbital entrapped muscle. Such entrapment can be the only feature of a previous floor fracture.11 This fracture requires prompt detection by the radiologist and urgent treatment within 24-72 hours to minimize the possibility of permanent motility problems.2,4,11-13
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Medial Orbital Wall Fractures Medial wall fractures are strongly associated with diplopia because of the entrapment of the medial rectus muscle with extraocular horizontal motility restriction, resulting in a pseudo-Duane retraction syndrome.2,11 Axial CT scans show loss of the normal posterior-medial bulge (lamina papyracea) of the orbit with secondary increase in orbital volume and enophthalmos. Both blow in and blow out patterns can result in muscle entrapment (Fig. 3).11 It is important to evaluate the extension of associated fractures of the naso-orbito-ethmoid complex involving the region of frontal process of the maxilla and the lacrimal fossa, where the medial canthal tendon attaches.2,11,14 CT scans can provide information about damage to the attachments of the medial canthi, alerting the surgeon to the need for a medial canthoplasty. Accurate fixation of bone fragment is sometimes required to restore the canthal anatomy: if the tendon insertion is not returned to its correct position, these fractures can result in permanent deformity characterized by telecanthus and globe malposition. The imaging specialist must also evaluate images for nasofrontal duct disruption, which may predispose the patient to future mucocele formation.2,11
External Wall and Orbital Apex Fractures Figure 4 Zygomaticomaxillary complex fracture. (A) Axial nonenhanced CT image, (B) coronal reformatted CT image. Nondisplaced fracture of the left zygoma, without angulation of the lateral orbital wall at the zygomaticosphenoid suture or changes in orbital volume.
External wall and orbital apex fractures result from direct lateral injury and may be an extension of a zygomaticomaxillary fractures.11 Radiologic description should include the degree of angulation of the lateral orbital wall (Fig. 4) and location of bone fragments (Fig. 5) (and should also describe the relationship with the optic nerve. In severe zygomaticomaxillary complex fractures with loss of anatomical integrity, the orbital defect may appear minimal and be underestimated.11 It is important to visualize the zygomatic defect and anatomic position to appreciate
Figure 5 Lateral wall fracture. (A) Axial nonenhanced CT image, (B) 3-dimensional–reconstructed image. Trimalar fracture involving the lateral orbit, with impingement of the lateral rectus by small bony fragments. (Color version of figure is available online.)
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388 the true loss of bone support. Orbital apex fractures may be associated with compression of the intracanalicular segment of optic nerve with subsequent loss of vision.11 Although rare, orbital apex fracture may indicate a surgical emergency if there is radiologic and clinical evidence of optic nerve impingement. Any clinical or radiologic finding indicating potential damage to the globe or the optic nerve, such as a retrobulbar hematoma or impinging bone fragment, should be immediately communicated to the surgeon especially if associated with decreasing vision.11,15
Orbital Roof Fractures Although common in the pediatric population, isolated orbital roof fractures are rarely found in adults.11 Direct blunt trauma of the superior orbital rim can result in isolated detached bone fragment that moves caudally in the orbit causing exophthalmos (blow in fracture). Minor dislocations are not generally an indication for repair (Figs 6 and 7). However, orbital roof fractures can be associated with pneumocephalus, intracranial hematoma, cerebrospinal fluid (CSF) leaks, and violation of the dura, necessitating early neurosurgical consultation.2,11
Intraorbital Trauma Anterior Chamber and Lens Injuries Bleeding into anterior chamber (hyphema) is detectable with physical examination (fluid-blood level) and results from disruption of blood vessels in the iris or ciliary body. This could be visualized by CT as increased attenuation in the anterior chamber.5 Reduction of anteroposterior diameter of the anterior chamber is an indirect finding of corneal laceration. This can result in prolapse of the iris into the anterior chamber to close the defect. Anterior subluxation of the lens, although rare, could be a false finding: therefore, the radiologist needs to evaluate the original position of the lens.5,16 Subluxation or traumatic luxation of the lens occurs secondary to deformation of the globe with dislocation and attraction of its constituents stretching zonular attachment of the lens. Partial or total laceration of the suspensory apparatus of the lens results, respectively, in a subluxation or in a complete luxation of the lens. Posterior luxation is more common because the iris hampers anterior luxation.5,17 The diagnosis of the dislocated lens, mostly caused by trauma (⬎50%), is generally made at the ophthalmologic examination and easily confirmed at CT. The reader should be aware that bilateral spontaneous dislocation of the lens occurs with systemic collagenopathies (Marfan syndrome, Ehlers–Danlos syndrome) and homocystinuria.18
Rupture of the Globe
Figure 6 Orbital roof fracture. (A) Axial nonenhanced CT image, (B) coronal-reformatted CT image. Depressed comminuted fracture of the right frontal sinus table that involves the right orbital roof.
Rupture of the globe is a major cause of blindness and must be ruled out in any patient who has suffered orbital trauma. Ruptures occur most commonly at the insertion of the intraocular muscles where the sclera is thinnest.19 CT has a 75% efficiency in the assessment of the rupture, which could be also visualized by clinical examination.20 CT findings suggestive of an open-globe injury include change in the globe contour with loss of volume (“flat-tire” sign), scleral discontinuity, pneumobulb, and presence of foreign bodies. An indirect sign of globe rupture is the posterior displacement of the lens into the vitreous humor, secondary to the loss of substance, with the expansion of the anterior chamber; in this case, the lens remains attached to the zonular fibers with no luxation.21 Hematoma and posttraumatic edema may cause deformation of the globe. This is important to recognize because it is a generally transient and reversible.1,2 The reader should be aware that congenital (eg, coloboma) or acquired (eg, staphyloma) deformities of the globe may lead to an erroneous diagnosis of traumatic deformation.5 Other causes of misinterpretation include intraocular air and endocular foreign bodies. The presence of endocular gas may result from a previous treatment of retinal detachment with injection of perfluoropropane into the vitreous. Similarly, the presence of synthetic material and a hyperdense scleral band may mimic foreign bodies.5,22 To avoid mistakes, the radiologist should recognize these conditions by comparison with previous examination and an adequate clinical evaluation.
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Figure 7 Orbital roof fracture. 3-dimensional–reconstructed images. Fracture of the right frontal bone extending to the orbital roof fracture with minimal bone displacement; right trimalar comminuted (complex) fracture and right parasymphyseal comminuted fracture of the mandible are associated. (Color version of figure is available online.)
Ocular Detachments Orbital trauma may result in lacerations of the 3 layers of the globe, leading to fluid collections detectable on CT examination. Retinal detachment occurs when the retina is separated from the choroid; it may also follow a traumatic laceration of the retina with collection of vitreous into the subretinal space. These collections assume a typical V-form with the posterior apex at the optic disk, to which the retina is firmly adhered, and the anterior extremities at the ora serrata.23,24 The presence of this finding in pediatric age may raise concern for possible nonaccidental trauma. Choroid detachment is due to a collection of fluid into the virtual suprachoroidal space, between the choroid and the sclera, typically creating biconvex-lens shape.23,25 Ocular hypotony (reduction of endocular pressure) may result from a traumatic perforation, and worsens with a choroid detachment. Diminished endocular pressure results in decreased pressure in the suprachoroidal space and accumulation of transudate, leading to a choroid detachment. Hemorrhage occurs if the detachment is associated with tearing of blood vessels. Posttraumatic hemorrhages may also occur within the vitreous (hemovitreous) or in the space between the vitreous and the retina. Hyperdense elements within the globe, deriving both from foreign bodies and from silicon oil for the treatment of retinal detachment, may mimic hemorrhage at CT.22
and the type of the foreign bodies. CT has a high sensitivity for metallic objects, while the detection of other materials, such as glass, wood, and organic material, may be problematic.26,27 Wooden foreign bodies appear hypoattenuating at CT; furthermore, they can be suspected by their geometric margins. MRI may be useful in doubtful cases, if contraindications are excluded (metallic objects detectable by CT). The higher contrast resolution and the use of fat suppression sequences facilitate the detection of injuries, foreign bodies. and the inflammatory response.6 Of course, adequate ophthalmologic clinical history reduces the possibility of erroneous diagnosis of synthetic material.
Carotid-Cavernous Fistula The occurrence of carotid-cavernous fistula, resulting from a traumatic laceration of the intracavernous segment of the internal carotid artery, has to be suspected in presence of diplopia associated with chemosis, hyperemia, and pulsatile exophthalmos.6 CT examination demonstrates edema and ocular proptosis and dilation of the superior ophthalmic vein. This latter finding has been reported in compression of the orbital apex and in other nontraumatic conditions, including cavernous sinus thrombosis, venous varix, Graves disease, and as a normal venous variant. Diagnosis of carotid-cavernous fistula has to be confirmed with CT angiography or with the conventional angiography.6,28
Intraorbital Foreign Bodies Detection and localization of foreign bodies are the key element in the radiologic examination of orbital trauma. Highresolution CT can detect objects ⬍1 mm in size.6 Diagnostic accuracy of CT depends also on the location
Optic Nerve Injuries Traumatic optic nerve injuries may be direct or indirect. Fracture of the optic canal is a rare occurrence. Often, a decrease in visual acuity does not correspond to a fracture
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390 diagnosis suggesting damage to the vascular supply of the nerve by compression or tearing of the vessel.6,29 A rapid decrease of visual acuity may represent a surgical emergency if confirmed by the finding of impingement or optic nerve injury at CT. MRI may detect increased signal intensity on T2-weighted sequences as a manifestation of direct injury.30
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Management of Orbital Trauma: Role of the Radiologist The clinical implications of orbital fractures differ from other facial fractures. The timing of surgery for orbital fracture is strongly related to a combination of several parameters, such as age, anatomic location of the fracture, presence of penetrating injuries and foreign bodies, presence of CSF leakage, functional involvement by muscle entrapment, and damage to the optic nerve.1,2 Surgical reconstruction of orbital fractures may be delayed until 10-14 days after orbital swelling has decreased.1,4 There are some conditions in which orbital fracture repair should be performed urgently, because of the high risk of permanent functional impairment and facial deformity.1 CT plays a crucial role for the evaluation of findings that indicate urgent treatment; moreover, CT helps to guide and plan the correct management of the patient toward a late surgical or conservative approach.
Indications for Orbital Fracture Surgery Within 2 Weeks ●
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Symptomatic diplopia because of limitation of motility with positive forced duction test and radiologic evidence of an entrapped muscle or perimuscular soft tissue on CT is an indication for surgery within 2 weeks. The imaging specialist must detect features of muscle entrapment or diagnose orbital edema and hemorrhage as alternative causes of transient diplopia. These latter findings resolve within 2-3 weeks and can be managed with conservative approach.1,2,31 Significant enophthalmos (⬎2.0 mm) secondary to orbital wall defect is an additional indication for surgery within 2 weeks.1,2,31 There is a direct relationship between the increase of orbital volume and the degree of late enophthalmos.32 The ability to recognize enophthalmos and associated bony wall defect by CT scanning is crucial for the surgeon. CT scan can also detect postinjury edema and hemorrhage with false proptosis, which masks a true enophthalmos.1 An orbital floor defect will not necessarily cause enophthalmos if the integrity of the fascial support of the globe is intact.1,31,33,34
Immediate or Early Surgery ●
“Trap-door” fracture in young patients (aged ⬍18 yr) associated with diplopia, ocular motility vertical limita-
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tions, and edema (white-eyed appearance) is an indication for immediate surgery. CT examination may or may not reveal the fracture in this age group; however the entrapped muscle or perimuscular soft tissue is well visualized.1,31,33 A rapid posttraumatic decrease of visual acuity or color vision and an afferent papillary defect alert the physician to the presence of traumatic optic neuropathy.2 Highresolution CT of the orbital apex should be performed to evaluate for possible fracture with optic nerve impingement. The imaging specialist may also detect damage to the globe or hematoma with compression on the optic nerve. Often, a localizable fracture is not found.6 Penetrating craniocerebral injuries associated with orbital fractures are an indication for immediate surgery. CT scans can provide information regarding involvement of anterior cranial fossa, revealing pneumocephalus, intracranial hematoma, leakage of CSF, and violation of the dura.1,2 Retained foreign body is another potential indication for immediate surgery. CT scans are crucial for this diagnosis.1 Diplopia with CT evidence of an entrapped muscle can also be considered as indication for urgent surgery, particularly if associated with a nonresolving oculocardiac reflex. Symptoms include a vagal tone response with bradycardia, vomiting, syncope, and potentially fatal heart block.1,2,31,35,36
References 1. Kontio R, Lindqvist C: Management of orbital fractures. Oral Maxillofac Surg Clin North Am 21:209-220, 2009 2. Joseph JM, Glavas IP: Orbital fractures: A review. Clin Ophthalmol 12:95-100, 2011 3. Dal Canto AJ, Linberg JV: Comparison of orbital fracture repair performed within 14 days versus 15 to 29 days after trauma. Ophthal Plast Reconstr Surg 24:437-443, 2008 4. Rhim CH, Scholz T, Salibian A, et al: Orbital floor fractures: A retrospective review of 45 cases at a tertiary health care center. Craniomaxillofac Trauma Reconstr 3:41-47, 2010 5. Lelli GJ, Milite J, Maher E: Orbital floor fractures: Evaluation, indications, approach, and pearls from an ophthalmologist’s perspective. Facial Plast Surg 23:190-199, 2007 6. Kubal WS: Imaging of orbital trauma. Radiographics 28:1729-1739, 2008 7. Ng P, Chu C, Young N, et al: Imaging of orbital floor fractures. Australas Radiol 40:264-268, 1996 8. Napolitano G, Sodano A, Califano L, et al: Multidetector row computed tomography with multiplanar and 3D images in the evaluation of posttreatment mandibular fractures. Semin Ultrasound CT MR 30:181187, 2009 9. Romeo A, Pinto A, Cappabianca S, et al: Role of multidetector row computed tomography in the management of mandible traumatic lesions. Semin Ultrasound CT MR 30:174-180, 2009 10. Rhea JT, Rao PM, Novelline RA: Helical CT and three-dimensional CT of facial and orbital injury. Radiol Clin North Am 37:489-513, 1999 11. Hopper RA, Salemy S, Sze RW: Diagnosis of midface fractures with CT: What the surgeon needs to know. Radiographics 26:783-793, 2006 12. Grant JH 3rd, Patrinely JR, Weiss AH, et al: Trapdoor fracture of the orbit in a pediatric population. Plast Reconstr Surg 109:482-489; discussion: 490-495, 2002 13. Bansagi ZC, Meyer DR: Internal orbital fractures in the pediatric
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16. 17. 18. 19. 20.
21. 22.
23. 24.
age group: Characterization and management. Ophthalmology 107: 829-836, 2000 Markowitz BL, Manson PN, Sargent L, et al: Management of the medial canthal tendon in nasoethmoid orbital fractures: The importance of the central fragment in classification and treatment. Plast Reconstr Surg 87:843-853, 1991 Linnau KF, Hallam DK, Lomoschitz FM, et al: Orbital apex injury: Trauma at the junction between the face and the cranium. Eur J Radiol 48:5-16, 2003 Novelline RA, Liebig T, Jordan J, et al: Computed tomography of ocular trauma. Emerg Radiol 1:56-67, 1994 Netland KE, Martinez J, LaCour OJ, et al: Traumatic anterior lens dislocation: A case report. J Emerg Med 17:637-639, 1999 Hardjasudarma M, Rivera E, Ganley JP, et al: Computed tomography of traumatic dislocation of the lens. Emerg Radiol 1:180-182, 1994 Bord SP, Linden J: Trauma to the globe and orbit. Emerg Med Clin North Am 26:97-123, 2008 Joseph DP, Pieramici DJ, Beauchamp NJ: Computed tomography in the diagnosis and prognosis of open-globe injuries. Ophthalmology 107: 1899-1906, 2000 Weissman JL, Beatty RL, Hirsch WL, et al: Enlarged anterior chamber: CT finding of a ruptured globe. AJNR Am J Neuroradiol 16:936-938, 1995 Lane JI, Watson RE Jr, Witte RJ, et al: Retinal detachment: Imaging of surgical treatments and complications. Radiographics 23:983-994, 2003 Mafee MF, Karimi A, Shah J, et al: Anatomy and pathology of the eye: Role of MR imaging and CT. Neuroimaging Clin N Am 15:23-47, 2005 Pieramici DJ: Vitreoretinal trauma. Ophthalmol Clin North Am 15: 225-234, 2002
391 25. Dalma-Weiszhausz J, Dalma A: The uvea in ocular trauma. Ophthalmol Clin North Am 15:205-213, 2002 26. Gor DM, Kirsch CF, Leen J, et al: Radiologic differentiation of intraocular glass: Evaluation of imaging techniques, glass types, size, and effect of intraocular hemorrhage. AJR Am J Roentgenol 177:1199-1203, 2001 27. Adesanya OO, Dawkins DM: Intraorbital wooden foreign body (IOFB): Mimicking air on CT. Emerg Radiol 14:45-49, 2007 28. Anderson K, Collie DA, Capewell A: CT angiographic appearances of carotico-cavernous fistula. Clin Radiol 56:514-516, 2001 29. Catalano RA: Blunt ocular injuries, in Catalano RA (ed): Ocular Emergencies. Philadelphia, PA, W. B. Saunders, 1992, pp 153-177 30. Go JL, Vu VN, Lee KJ, et al: Orbital trauma. Neuroimaging Clin N Am 12:311-324, 2002 31. Burnstine MA: Clinical recommendations for repair of isolated orbital floor fractures: An evidence-based analysis. Ophthalmology 109:12071210, 2002; discussion: 1210-1211 32. Ahn HB, Ryu WY, Yoo KW, et al: Prediction of enophthalmos by computer-based volume measurement of orbital fractures in a Korean population. Ophthal Plast Reconstr Surg 1:36-39, 2008 33. Cole P, Boyd V, Banerji S, et al: Comprehensive management of orbital fractures. Plast Reconstr Surg 120:57-61, 2007 34. de Man K, Wijngaarde R, Hes J, et al: Influence of age on the management of blow-out fractures of the orbital floor. Int J Oral Maxillofac Surg 20:330-336, 1991 35. Sires BS, Stanley RB Jr, Levine LM: Oculocardiac reflex caused by orbital floor trapdoor fracture: An indication for urgent repair. Arch Ophthalmol 116:955-956, 1998 36. Grant JH, Patrinely JR, Weiss AH, et al: Trapdoor fracture of the orbit in a pediatric population. Plast Reconstr Surg 109:482-489, 2002
O
rbital fractures have a widely variable presentation and clinical severity. The anatomic complexity of the orbital and intraorbital structures also creates confusion. Orbital fractures differ from all other facial fractures in that surgery does not typically attempt to achieve bone healing but instead aims to reconstruct the defective area of the fractured wall, restoring the original shape of the orbit.1 Thus, delaying the operation for varying periods is feasible and often recommended. Resolution of orbital swelling or hemorrhage, and reduction of their influence on the clinical course, facilitates accurate diagnosis and strengthens the indications for surgery.1-4 Ophthalmologic counseling is crucial,2,5 but physical examination might be difficult because of the altered condition of the wounded eye; moreover, the patient may be unable to cooperate.6 In these cases, the diagnosis is limited to radiologic examination, which provides guidance for the maxillofacial surgeon. Therefore, the radiologist’s role is crucial in the early detection of the findings that can result in esthetic deformities and functional deficiencies. Medicolegal issues must not be overlooked.
*Department of Diagnostic Radiology and Radiotherapy, Federico II University of Naples, Naples, Italy. †Institute of Radiology, Second University of Naples, Naples, Italy. ‡Department of Health Science, Chair of Radiology, University of Molise, Campobasso, Italy. §Institute of Radiology, University of Turin, Turin, Italy. Address reprint requests to Ferdinando Caranci, MD, Department of Diagnostic Radiology and Radiotherapy, Federico II University of Naples, Via Boccaccio 2, 80123 Naples, Italy. E-mail: [email protected]
0887-2171/$-see front matter © 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1053/j.sult.2012.06.007
Radiographic examination of the orbits is rarely performed; ultrasonography can be very useful for evaluating the globe and its contents, but it is contraindicated if a ruptured globe is suspected.6 Computed tomography (CT) is considered the imaging modality of choice in evaluating orbital trauma, and it is the most accurate method in detecting fractures.2,6,7,8 Protocols include thin-section axial CT scans as well as multiplanar reformatted images. Both are useful tools to guide treatment.6,9,10 In addition to its primary role in the evaluation of the fractures, CT may also provide information for the detection of soft-tissue injuries. Magnetic resonance imaging (MRI) may be difficult to be perform in emergent conditions and is contraindicated if there is the possibility that a metallic intraorbital foreign body is present.6 Therefore, it is not recommended in the initial evaluation of the trauma, although MRI ultimately can provide useful detailed information.
Imaging of the Orbital Fractures Orbital fractures can be isolated but are more commonly associated with other midface fractures, such as posterior propagation of naso-orbito-ethmoid fractures (medial orbital wall) and zygomaticomaxillary complex fractures (orbital floor, lateral orbital wall). Fractures of the orbital skeleton may also occur in Le Fort II complex (medial wall and floor) and Le Fort III complex (medial wall, posterior orbital floor, lateral wall).11 Detailed knowledge of the anatomy of the orbit is required, including bone laminae and recesses. Supraorbital and infraorbital foramina should not be misinterpreted as fractures. Blow out fractures are the most common. They are caused by 385
386
Figure 1 Blow out fracture of the orbital floor. Coronal nonenhanced-reformatted computed tomography (CT) image. Left orbital floor fracture without evidence of entrapment of the inferior rectus muscle, which remains flattened in cross-sectional appearance, indicating integrity of the fascial support of the globe.
increased intraorbital pressure because of direct orbital blunt injury, which causes a break of the orbital walls at their weakest point.2,11 These fractures are differentiated into pure or impure type depending on the involvement of the orbital rim. Blow in fractures are less frequent; they result from direct injury to the paranasal sinus region with centrifugal displacement of bone fragments.11
Orbital Floor Fractures The orbital floor and medial wall are relatively thin; therefore, they are more vulnerable and frequent sites of frac-
Figure 2 Blow out fracture of the orbital floor. Coronal nonenhanced-reformatted CT image. Left orbital floor fracture, with the inferior rectus attracted inferiorly toward the maxillary sinus; the cross-sectional appearance of the muscle has changed from flattened to ovoid, indicating entrapment because of disruption of the fascial support.
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Figure 3 Medial wall fracture. Axial nonenhanced CT image. The right lamina papyracea has collapsed toward the midline, causing an increase of the orbital volume (without enophthalmos); the ipsilateral medial rectus maintains the typical flattened profile without herniation into the fracture site. Lateral orbital wall fractures are present bilaterally.
ture.2 In these cases, there is a strong potential for diplopia because of entrapment of inferior and medial rectus muscles. To plan adequate medical and surgical treatment, CT scanning is required to evaluate the shape and position of these muscles.1,11 In case of orbital floor fracture, it is mandatory to evaluate the shape and position of the inferior rectus muscle and of orbital adipose tissue on coronal and sagittal CT reconstructions. The study can provide information regarding entrapment of the inferior rectus muscle and the fascial sling of the globe, directly correlating with diplopia and vertical restriction. On cross-section images, if the inferior rectus remains flattened and in the correct position (Fig. 1), the fascial sling is likely intact and the surgeon will encounter minimal entrapped periorbital tissue. If the inferior rectus has a rounded shape and is inferiorly displaced, the fascial sling is likely compromised, leading to periorbita and muscle prolapse through the orbital floor defect (Fig. 2).11 Infraorbital groove (nerve) involvement often occurs in orbital floor fractures with consequent sensory dysfunction.2,5 A large wall defect can be associated with increase of the orbital volume resulting in enophthalmos.1,2 Entrapment of the inferior rectus in children may be easily missed or underestimated. The flexible pediatric bone springs back into place after injury covering the traumatic defect like a “trapdoor.” This results in a normal appearance at CT except for the infraorbital entrapped muscle. Such entrapment can be the only feature of a previous floor fracture.11 This fracture requires prompt detection by the radiologist and urgent treatment within 24-72 hours to minimize the possibility of permanent motility problems.2,4,11-13
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Medial Orbital Wall Fractures Medial wall fractures are strongly associated with diplopia because of the entrapment of the medial rectus muscle with extraocular horizontal motility restriction, resulting in a pseudo-Duane retraction syndrome.2,11 Axial CT scans show loss of the normal posterior-medial bulge (lamina papyracea) of the orbit with secondary increase in orbital volume and enophthalmos. Both blow in and blow out patterns can result in muscle entrapment (Fig. 3).11 It is important to evaluate the extension of associated fractures of the naso-orbito-ethmoid complex involving the region of frontal process of the maxilla and the lacrimal fossa, where the medial canthal tendon attaches.2,11,14 CT scans can provide information about damage to the attachments of the medial canthi, alerting the surgeon to the need for a medial canthoplasty. Accurate fixation of bone fragment is sometimes required to restore the canthal anatomy: if the tendon insertion is not returned to its correct position, these fractures can result in permanent deformity characterized by telecanthus and globe malposition. The imaging specialist must also evaluate images for nasofrontal duct disruption, which may predispose the patient to future mucocele formation.2,11
External Wall and Orbital Apex Fractures Figure 4 Zygomaticomaxillary complex fracture. (A) Axial nonenhanced CT image, (B) coronal reformatted CT image. Nondisplaced fracture of the left zygoma, without angulation of the lateral orbital wall at the zygomaticosphenoid suture or changes in orbital volume.
External wall and orbital apex fractures result from direct lateral injury and may be an extension of a zygomaticomaxillary fractures.11 Radiologic description should include the degree of angulation of the lateral orbital wall (Fig. 4) and location of bone fragments (Fig. 5) (and should also describe the relationship with the optic nerve. In severe zygomaticomaxillary complex fractures with loss of anatomical integrity, the orbital defect may appear minimal and be underestimated.11 It is important to visualize the zygomatic defect and anatomic position to appreciate
Figure 5 Lateral wall fracture. (A) Axial nonenhanced CT image, (B) 3-dimensional–reconstructed image. Trimalar fracture involving the lateral orbit, with impingement of the lateral rectus by small bony fragments. (Color version of figure is available online.)
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388 the true loss of bone support. Orbital apex fractures may be associated with compression of the intracanalicular segment of optic nerve with subsequent loss of vision.11 Although rare, orbital apex fracture may indicate a surgical emergency if there is radiologic and clinical evidence of optic nerve impingement. Any clinical or radiologic finding indicating potential damage to the globe or the optic nerve, such as a retrobulbar hematoma or impinging bone fragment, should be immediately communicated to the surgeon especially if associated with decreasing vision.11,15
Orbital Roof Fractures Although common in the pediatric population, isolated orbital roof fractures are rarely found in adults.11 Direct blunt trauma of the superior orbital rim can result in isolated detached bone fragment that moves caudally in the orbit causing exophthalmos (blow in fracture). Minor dislocations are not generally an indication for repair (Figs 6 and 7). However, orbital roof fractures can be associated with pneumocephalus, intracranial hematoma, cerebrospinal fluid (CSF) leaks, and violation of the dura, necessitating early neurosurgical consultation.2,11
Intraorbital Trauma Anterior Chamber and Lens Injuries Bleeding into anterior chamber (hyphema) is detectable with physical examination (fluid-blood level) and results from disruption of blood vessels in the iris or ciliary body. This could be visualized by CT as increased attenuation in the anterior chamber.5 Reduction of anteroposterior diameter of the anterior chamber is an indirect finding of corneal laceration. This can result in prolapse of the iris into the anterior chamber to close the defect. Anterior subluxation of the lens, although rare, could be a false finding: therefore, the radiologist needs to evaluate the original position of the lens.5,16 Subluxation or traumatic luxation of the lens occurs secondary to deformation of the globe with dislocation and attraction of its constituents stretching zonular attachment of the lens. Partial or total laceration of the suspensory apparatus of the lens results, respectively, in a subluxation or in a complete luxation of the lens. Posterior luxation is more common because the iris hampers anterior luxation.5,17 The diagnosis of the dislocated lens, mostly caused by trauma (⬎50%), is generally made at the ophthalmologic examination and easily confirmed at CT. The reader should be aware that bilateral spontaneous dislocation of the lens occurs with systemic collagenopathies (Marfan syndrome, Ehlers–Danlos syndrome) and homocystinuria.18
Rupture of the Globe
Figure 6 Orbital roof fracture. (A) Axial nonenhanced CT image, (B) coronal-reformatted CT image. Depressed comminuted fracture of the right frontal sinus table that involves the right orbital roof.
Rupture of the globe is a major cause of blindness and must be ruled out in any patient who has suffered orbital trauma. Ruptures occur most commonly at the insertion of the intraocular muscles where the sclera is thinnest.19 CT has a 75% efficiency in the assessment of the rupture, which could be also visualized by clinical examination.20 CT findings suggestive of an open-globe injury include change in the globe contour with loss of volume (“flat-tire” sign), scleral discontinuity, pneumobulb, and presence of foreign bodies. An indirect sign of globe rupture is the posterior displacement of the lens into the vitreous humor, secondary to the loss of substance, with the expansion of the anterior chamber; in this case, the lens remains attached to the zonular fibers with no luxation.21 Hematoma and posttraumatic edema may cause deformation of the globe. This is important to recognize because it is a generally transient and reversible.1,2 The reader should be aware that congenital (eg, coloboma) or acquired (eg, staphyloma) deformities of the globe may lead to an erroneous diagnosis of traumatic deformation.5 Other causes of misinterpretation include intraocular air and endocular foreign bodies. The presence of endocular gas may result from a previous treatment of retinal detachment with injection of perfluoropropane into the vitreous. Similarly, the presence of synthetic material and a hyperdense scleral band may mimic foreign bodies.5,22 To avoid mistakes, the radiologist should recognize these conditions by comparison with previous examination and an adequate clinical evaluation.
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Figure 7 Orbital roof fracture. 3-dimensional–reconstructed images. Fracture of the right frontal bone extending to the orbital roof fracture with minimal bone displacement; right trimalar comminuted (complex) fracture and right parasymphyseal comminuted fracture of the mandible are associated. (Color version of figure is available online.)
Ocular Detachments Orbital trauma may result in lacerations of the 3 layers of the globe, leading to fluid collections detectable on CT examination. Retinal detachment occurs when the retina is separated from the choroid; it may also follow a traumatic laceration of the retina with collection of vitreous into the subretinal space. These collections assume a typical V-form with the posterior apex at the optic disk, to which the retina is firmly adhered, and the anterior extremities at the ora serrata.23,24 The presence of this finding in pediatric age may raise concern for possible nonaccidental trauma. Choroid detachment is due to a collection of fluid into the virtual suprachoroidal space, between the choroid and the sclera, typically creating biconvex-lens shape.23,25 Ocular hypotony (reduction of endocular pressure) may result from a traumatic perforation, and worsens with a choroid detachment. Diminished endocular pressure results in decreased pressure in the suprachoroidal space and accumulation of transudate, leading to a choroid detachment. Hemorrhage occurs if the detachment is associated with tearing of blood vessels. Posttraumatic hemorrhages may also occur within the vitreous (hemovitreous) or in the space between the vitreous and the retina. Hyperdense elements within the globe, deriving both from foreign bodies and from silicon oil for the treatment of retinal detachment, may mimic hemorrhage at CT.22
and the type of the foreign bodies. CT has a high sensitivity for metallic objects, while the detection of other materials, such as glass, wood, and organic material, may be problematic.26,27 Wooden foreign bodies appear hypoattenuating at CT; furthermore, they can be suspected by their geometric margins. MRI may be useful in doubtful cases, if contraindications are excluded (metallic objects detectable by CT). The higher contrast resolution and the use of fat suppression sequences facilitate the detection of injuries, foreign bodies. and the inflammatory response.6 Of course, adequate ophthalmologic clinical history reduces the possibility of erroneous diagnosis of synthetic material.
Carotid-Cavernous Fistula The occurrence of carotid-cavernous fistula, resulting from a traumatic laceration of the intracavernous segment of the internal carotid artery, has to be suspected in presence of diplopia associated with chemosis, hyperemia, and pulsatile exophthalmos.6 CT examination demonstrates edema and ocular proptosis and dilation of the superior ophthalmic vein. This latter finding has been reported in compression of the orbital apex and in other nontraumatic conditions, including cavernous sinus thrombosis, venous varix, Graves disease, and as a normal venous variant. Diagnosis of carotid-cavernous fistula has to be confirmed with CT angiography or with the conventional angiography.6,28
Intraorbital Foreign Bodies Detection and localization of foreign bodies are the key element in the radiologic examination of orbital trauma. Highresolution CT can detect objects ⬍1 mm in size.6 Diagnostic accuracy of CT depends also on the location
Optic Nerve Injuries Traumatic optic nerve injuries may be direct or indirect. Fracture of the optic canal is a rare occurrence. Often, a decrease in visual acuity does not correspond to a fracture
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390 diagnosis suggesting damage to the vascular supply of the nerve by compression or tearing of the vessel.6,29 A rapid decrease of visual acuity may represent a surgical emergency if confirmed by the finding of impingement or optic nerve injury at CT. MRI may detect increased signal intensity on T2-weighted sequences as a manifestation of direct injury.30
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Management of Orbital Trauma: Role of the Radiologist The clinical implications of orbital fractures differ from other facial fractures. The timing of surgery for orbital fracture is strongly related to a combination of several parameters, such as age, anatomic location of the fracture, presence of penetrating injuries and foreign bodies, presence of CSF leakage, functional involvement by muscle entrapment, and damage to the optic nerve.1,2 Surgical reconstruction of orbital fractures may be delayed until 10-14 days after orbital swelling has decreased.1,4 There are some conditions in which orbital fracture repair should be performed urgently, because of the high risk of permanent functional impairment and facial deformity.1 CT plays a crucial role for the evaluation of findings that indicate urgent treatment; moreover, CT helps to guide and plan the correct management of the patient toward a late surgical or conservative approach.
Indications for Orbital Fracture Surgery Within 2 Weeks ●
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Symptomatic diplopia because of limitation of motility with positive forced duction test and radiologic evidence of an entrapped muscle or perimuscular soft tissue on CT is an indication for surgery within 2 weeks. The imaging specialist must detect features of muscle entrapment or diagnose orbital edema and hemorrhage as alternative causes of transient diplopia. These latter findings resolve within 2-3 weeks and can be managed with conservative approach.1,2,31 Significant enophthalmos (⬎2.0 mm) secondary to orbital wall defect is an additional indication for surgery within 2 weeks.1,2,31 There is a direct relationship between the increase of orbital volume and the degree of late enophthalmos.32 The ability to recognize enophthalmos and associated bony wall defect by CT scanning is crucial for the surgeon. CT scan can also detect postinjury edema and hemorrhage with false proptosis, which masks a true enophthalmos.1 An orbital floor defect will not necessarily cause enophthalmos if the integrity of the fascial support of the globe is intact.1,31,33,34
Immediate or Early Surgery ●
“Trap-door” fracture in young patients (aged ⬍18 yr) associated with diplopia, ocular motility vertical limita-
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tions, and edema (white-eyed appearance) is an indication for immediate surgery. CT examination may or may not reveal the fracture in this age group; however the entrapped muscle or perimuscular soft tissue is well visualized.1,31,33 A rapid posttraumatic decrease of visual acuity or color vision and an afferent papillary defect alert the physician to the presence of traumatic optic neuropathy.2 Highresolution CT of the orbital apex should be performed to evaluate for possible fracture with optic nerve impingement. The imaging specialist may also detect damage to the globe or hematoma with compression on the optic nerve. Often, a localizable fracture is not found.6 Penetrating craniocerebral injuries associated with orbital fractures are an indication for immediate surgery. CT scans can provide information regarding involvement of anterior cranial fossa, revealing pneumocephalus, intracranial hematoma, leakage of CSF, and violation of the dura.1,2 Retained foreign body is another potential indication for immediate surgery. CT scans are crucial for this diagnosis.1 Diplopia with CT evidence of an entrapped muscle can also be considered as indication for urgent surgery, particularly if associated with a nonresolving oculocardiac reflex. Symptoms include a vagal tone response with bradycardia, vomiting, syncope, and potentially fatal heart block.1,2,31,35,36
References 1. Kontio R, Lindqvist C: Management of orbital fractures. Oral Maxillofac Surg Clin North Am 21:209-220, 2009 2. Joseph JM, Glavas IP: Orbital fractures: A review. Clin Ophthalmol 12:95-100, 2011 3. Dal Canto AJ, Linberg JV: Comparison of orbital fracture repair performed within 14 days versus 15 to 29 days after trauma. Ophthal Plast Reconstr Surg 24:437-443, 2008 4. Rhim CH, Scholz T, Salibian A, et al: Orbital floor fractures: A retrospective review of 45 cases at a tertiary health care center. Craniomaxillofac Trauma Reconstr 3:41-47, 2010 5. Lelli GJ, Milite J, Maher E: Orbital floor fractures: Evaluation, indications, approach, and pearls from an ophthalmologist’s perspective. Facial Plast Surg 23:190-199, 2007 6. Kubal WS: Imaging of orbital trauma. Radiographics 28:1729-1739, 2008 7. Ng P, Chu C, Young N, et al: Imaging of orbital floor fractures. Australas Radiol 40:264-268, 1996 8. Napolitano G, Sodano A, Califano L, et al: Multidetector row computed tomography with multiplanar and 3D images in the evaluation of posttreatment mandibular fractures. Semin Ultrasound CT MR 30:181187, 2009 9. Romeo A, Pinto A, Cappabianca S, et al: Role of multidetector row computed tomography in the management of mandible traumatic lesions. Semin Ultrasound CT MR 30:174-180, 2009 10. Rhea JT, Rao PM, Novelline RA: Helical CT and three-dimensional CT of facial and orbital injury. Radiol Clin North Am 37:489-513, 1999 11. Hopper RA, Salemy S, Sze RW: Diagnosis of midface fractures with CT: What the surgeon needs to know. Radiographics 26:783-793, 2006 12. Grant JH 3rd, Patrinely JR, Weiss AH, et al: Trapdoor fracture of the orbit in a pediatric population. Plast Reconstr Surg 109:482-489; discussion: 490-495, 2002 13. Bansagi ZC, Meyer DR: Internal orbital fractures in the pediatric
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391 25. Dalma-Weiszhausz J, Dalma A: The uvea in ocular trauma. Ophthalmol Clin North Am 15:205-213, 2002 26. Gor DM, Kirsch CF, Leen J, et al: Radiologic differentiation of intraocular glass: Evaluation of imaging techniques, glass types, size, and effect of intraocular hemorrhage. AJR Am J Roentgenol 177:1199-1203, 2001 27. Adesanya OO, Dawkins DM: Intraorbital wooden foreign body (IOFB): Mimicking air on CT. Emerg Radiol 14:45-49, 2007 28. Anderson K, Collie DA, Capewell A: CT angiographic appearances of carotico-cavernous fistula. Clin Radiol 56:514-516, 2001 29. Catalano RA: Blunt ocular injuries, in Catalano RA (ed): Ocular Emergencies. Philadelphia, PA, W. B. Saunders, 1992, pp 153-177 30. Go JL, Vu VN, Lee KJ, et al: Orbital trauma. Neuroimaging Clin N Am 12:311-324, 2002 31. Burnstine MA: Clinical recommendations for repair of isolated orbital floor fractures: An evidence-based analysis. Ophthalmology 109:12071210, 2002; discussion: 1210-1211 32. Ahn HB, Ryu WY, Yoo KW, et al: Prediction of enophthalmos by computer-based volume measurement of orbital fractures in a Korean population. Ophthal Plast Reconstr Surg 1:36-39, 2008 33. Cole P, Boyd V, Banerji S, et al: Comprehensive management of orbital fractures. Plast Reconstr Surg 120:57-61, 2007 34. de Man K, Wijngaarde R, Hes J, et al: Influence of age on the management of blow-out fractures of the orbital floor. Int J Oral Maxillofac Surg 20:330-336, 1991 35. Sires BS, Stanley RB Jr, Levine LM: Oculocardiac reflex caused by orbital floor trapdoor fracture: An indication for urgent repair. Arch Ophthalmol 116:955-956, 1998 36. Grant JH, Patrinely JR, Weiss AH, et al: Trapdoor fracture of the orbit in a pediatric population. Plast Reconstr Surg 109:482-489, 2002