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Orbital Fracture Evaluation by Coronal Computed Tomography
ORBITAL FRACTURE EVALUATION BY CORONAL C O M P U T E D TOMOGRAPHY A R T H U R S. G R O V E , J R . , M.D., R I N A T A D M O R , M.D., P A U L F. J. N E W , M.D., A N D K. JACK M O M O S E , M.D.
Boston, Massachusetts
Fractures of the orbital floor are fre quently accompanied by displacement of bone fragments and by soft tissue dam age. Using Caldwell and Waters views, roentgenograms of the face are used to detect fractures and evaluate distortion of the orbital walls. These roentgenograms may also allow visualization of soft tissue densities, outline prolapsed orbital con tents, and show air-fluid levels. 1 - 3 Radiographic linear tomography (laminography) and hypocycloidal tomogra phy (polytomography) are used to visua lize thin focal plane sections in order to distinguish greater bone and soft tissue details. However, bone fragments may not be seen clearly even on radiographic tomograms. Soft tissue densities found within the sinuses on x-ray films cannot be identified anatomically and may repre sent submucosal blood or prolapsed or bital tissues without muscle entrapment. 4 Other techniques which have been used to evaluate orbital fractures include xeroradiography, positive contrast orbitography, and computed tomography. 3 , 5 Of all these methods, only computed to mography provides detailed visualization of both the bones and the soft tissues of the orbits. Until recently, computed tomography of the head and orbits could only be performed in an axial plane. As a conse quence, cross-sections of the orbits could From the Department of Ophthalmology, Massa chusetts Eye and Ear Infirmary (Dr. Grove), and the Department of Radiology, Massachusetts General Hospital (Drs. Tadmor, New, and Momose), Har vard Medical School, Boston, Massachusetts. Reprint requests to Arthur S. Grove, Jr., M.D., Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA 02114.
only be visualized in the same plane as the paths of the optic nerves. Although the horizontal rectus muscles can be seen clearly on axial scans, it is extremely difficult to visualize soft tissues near the orbital floor and to detect defects in the floor.3,5-8 By using a computed tomographic total body scanner, high resolution scans can be made through the orbits in a coronal plane that is analogous to Caldwell-view x-ray films. This technique of coronal computed tomography has permitted vis ualization of tangential cross-sections of all four orbital walls, including the floor, and of the orbital soft tissues, including all extraocular muscles. 5 S U B J E C T S AND M E T H O D S
Patients at the Massachusetts Eye and Ear Infirmary who suffered serious midfacial trauma were examined by conven tion orbital x-ray films. Those who were suspected of having orbital fractures were usually examined by hypocycloidal to mography as well. Selected patients who had fractures of the orbital floor were then studied by coronal computed tomography to aid in the management of their injuries and to determine the usefulness of coro nal computed tomography for the evalua tion of orbital fractures. Computed tomography was performed with an EMI-5000 (prototype) total body scanner by using 24-cm field. We ob tained most coronal scans by placing the patients supine on an elevated board in the "hanging head" position. Some pa tients preferred the prone "elevated chin" position. The plane of the coronal scans was as near perpendicular to Reid's base line as possible. 5 Some patients could
AMERICAN JOURNAL OF OPHTHALMOLOGY 85:679-685, 1978
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Fig. 1 (Grove and associates). Case 1. Patient has restriction of movement of the right eye in upgaze (left) and downgaze (right) two weeks after trauma to the right orbit.
not tolerate sufficient head extension to achieve these positions, and scan planes of 60 degrees to 80 degrees from Reid's baseline were used. A specially designed 6-mm collimator was used and each patient was studied with three to five sections spaced at 5-mm intervals. We performed 70-second "high accuracy" scans and viewed images as direct enlargements of scan quadrants in order to improve visualization of the bones and soft tissues.
1977. A right hypertropia persisted after injury, and movement of the right eye was restricted in both upgaze and downgaze (Fig. 1). Polytomes demonstrated a linear fracture of the
RESULTS
All patients examined by coronal com puted tomography were first found to have orbital fractures by conventional ra diography. The computed tomograms in each case showed greater details of both the bones and soft tissues than the corre sponding roentgenograms. Three repre sentative cases of orbital floor fractures reported herein demonstrate features that can be visualized by coronal computed tomography to compare this technique with clinical findings and with the results of radiographic studies. These cases in clude a patient with a linear orbital floor fracture, a patient with a depressed orbit al floor fracture, and a patient with a severely comminuted orbital floor. CASE REPORTS
Case 1. Linear Fracture of Orbital Floor with Entrapment of Inferior Rectus Muscle—A 30-yearold woman was struck over the right eye in March
Fig. 2 (Grove and associates). Case 1. Tomographic sections through anterior orbits. Top, Polytome shows densities (arrows) in right maxillary and ethmoid sinuses. Bottom, Coronal computed tomog raphy shows small fracture (black arrow) in right orbital bloor and soft tissues (white arrows) in right maxillary and ethmoid sinuses. Normal tissues visu alized in left orbit include globe (G), levator (L), and medial rectus (M).
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Fig. 4 (Grove and associates). Case 1. Forced traction test shows restriction of elevation of right eye.
Fig. 3 (Grove and associates) Case 1. Tomographic sections through middle orbits. Top, Polytome shows slightly angulated bone fragment (arrow) of orbital floor. Bottom, coronal computed tomography shows soft tissues in right maxillary and ethmoid sinuses. Adjacent to angulated bone fragment is a soft tissue density (small arrowheads), which repre sents orbital component of entrapped inferior rectus muscle. Muscle is outlined by surrounding dark rim of low density fat. Normal tissues visualized in left orbit include optic nerve (N) and inferior rectus (I). Levator and medial rectus are again visible. right orbital floor. In the anterior tomograms, tissue densities were seen in the roof of the right maxillary sinus and in the lateral portion of the right ethmoid sinus (Fig. 2, top). Similar^oft tissue densities were found in the posterior tomograms, where a slightly angulated bone fragment was also visible (Fig. 3, top). Coronal computed tomography similarly revealed densities within the right maxillary and ethmoid sinuses. The linear fracture was clearly outlined in the anterior scans (Fig. 2, bottom). In the posterior scans, the inferior rectus muscle was visible within the fracture (Fig. 3, bottom). In the left orbit, normal
bone and soft tissue details were seen, including the globe, optic nerve, and extraocular muscles. A forced traction test showed restriction of eleva tion of the right eye (Fig. 4). Because vertical move ments of the right eye remained restricted and the patient suffered diplopia in primary gaze, the right orbit was explored two weeks after injury. Orbital fat was found prolapsed into a linear fracture of the floor (Fig. 5). As this tissue was withdrawn, the inferior rectus muscle (Fig. 6) was found incarcerat ed within the fracture. This muscle was extracted, and the defect was covered with a plastic plate. A forced traction test performed at the end of the
Fig. 5 (Grove and associates). Case 1. Exploration of right orbital floor reveals orbital soft tissues prolapsed into linear fracture (arrow).
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Fig. 6 (Grove and associates). Case 1. After extrac tion of prolapsed fat, inferior rectus muscle (arrows) is found incarcerated in orbital floor fracture.
operation revealed no restriction of elevation (Fig. 7). Recovery from surgery was uneventful, with no subjective diplopia persisting after one month. Movements of the right eye were full except for minimal restriction of downgaze (Fig. 8). Case 2. Depressed Fracture of Orbital Floor with Entrapment of Inferior Rectus Muscle—A 30-yearold man was struck over the right eye in May 1977. After injury vertical movements of the right eye were restricted, more severely in upgaze than in downgaze. Polytomes revealed a wide defect in the floor of the right orbit. On these examinations, a fragment of the floor could be seen depressed into the right maxillary sinus (Fig. 9, top). Coronal computed tomography clearly showed the depressed fragment as well as the inferior rectus muscle, which was trapped between the displaced bone and the lateral orbital floor (Fig. 9, bottom). Metallic dental fillings produced radiating artifacts on the lower portion of this scan. Since a forced traction test revealed restriction of elevation of the right eye, and since vertical move ments of the right eye did not improve in functional ly important positions of gaze, the right orbit was
MAY, 1978
Fig. 7 (Grove and associates). Case 1. Forced traction test after completion of surgery shows no restriction of elevation. explored four weeks after trauma. The inferior rec tus muscle was found trapped in the same position seen on the computed tomograms. The prolapsed tissues were withdrawn from the fracture, which was covered by a plastic plate. Although vertical movements of the right eye improved after surgery, the patient still complained of diplopia in extremes of upgaze and downgaze. Case 3. Comminuted Fracture of Orbital Floor with Large Soft Tissue Prolapse—A 28-year-old man was struck over the left eye in March 1977; immediately afterward, movements of the left eye were restricted in all positions of gaze, and the eye was 2 mm more prominent than the right. Polytomes showed opacification of the left maxillary and eth moid sinuses, together with fragmentation and de pression of the orbital floor (Figs. 10, top, and 11, top). Coronal computed tomography demonstrated the displaced bone fragments and delineated soft tissue densities more clearly than the roentgenograms. Air-fluid levels could be seen in the lower left maxillary sinus because the scans were performed with the patient supine in the hanging head posi-
Fig. 8 (Grove and associates). Case 1. Six weeks after operation, patient has no limitation of upgaze (left) and only minimal restriction of downgaze (right), causing no subjective diplopia.
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be localized by radiographic tomography. However, in our cases, bone fragments and fracture defects were better delineat ed by coronal computed tomography than by polytomography. Most fractures of the orbital floor do not require surgical repair. In many patients whose eye movements are limited in all positions of gaze, such as Case 3, the restriction may be caused by nerve dam age, generalized orbital edema, or hemor rhage. A patient with entrapment of the inferior rectus or inferior oblique muscle will usually have restriction chiefly of upgaze and downgaze. The forced trac tion test is useful to help determine when an extraocular muscle is entrapped within a fracture.2,3
Fig. 9 (Grove and associates). Case2. Tomographic sections through middle orbits. Top, Polytome shows fragment of orbital floor (arrow) depressed into maxillary sinus. Bottom, Coronal computed to mography shows soft tissue density including infe rior rectus muscle (black arrow), which can be seen adjacent to depressed floor fragment (white arrow). Dental fillings produce radiating artifacts visible in lower part of scan. tion, with his chin higher than his brow (Figs. 10, bottom, and 11, bottom). Within two weeks after injury, no diplopia was present in primary gaze and movements of the left eye had improved in all other positions of gaze. A forced traction test did not show restriction of verti cal movement of the left eye. At that time the left eye was neither abnormally prominent nor enophthalmic. No surgery was performed and the patient failed to return for additional examination. DISCUSSION
Fractures of the orbital floor can usual ly be visualized on Caldwell or Waters view roentgenograms. Fractures that are not seen on plain films can almost always
Fig. 10 (Grove and associates). Case 3. Tomographic sections through middle orbits. Top, Poly tome shows left paranasal sinus opacification and multiple bone fragments (arrows). Bottom, coronal computed tomography also shows comminuted or bital floor fragments (arrows) which are depressed into the maxillary sinus.
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the computed tomograms showed the in ferior rectus muscle directly adjacent to the fracture. Entrapment of the muscle was clinically suspected in these patients because of limitation of voluntary eye movements in upgaze and downgaze and because of forced traction testing. At the time of surgical exploration, entrapment of the inferior rectus was found and eye movements improved after the operation.
Fig. 11 (Grove and associates). Case 3. Tomographic sections through posterior orbits. Top, As in more anterior study, polytome shows depressed orbital floor (arrow). Bottom, Coronal computed to mography shows soft tissue details, multiple bone fragments, and air-fluid levels (arrows) which are not apparent on corresponding x-ray film.
Surgical intervention is usually re quired only if an orbital floor fracture mechanically impinges upon either the adjacent inferior rectus or inferior oblique muscle to produce significant diplopia in functionally important posi tions of gaze. In some patients, repair of the fracture may be warranted because of cosmetically objectionable lowering of the globe. Rarely, bone fragments which are displaced toward the globe or optic nerve may require surgical reduction. Each of the three patients described in this report had radiographic evidence of a fracture of the orbital floor and a soft tissue density within the maxillary sinus next to the bone defect. In Cases 1 and 2,
When bone is surrounded by air, as in the nose or sinuses, details are usually seen more clearly on polytomes than on computed tomograms. However, when bone fragments are located adjacent to soft tissues, they may be seen more dis cretely on coronal computed tomograms because of the capacity of computed to mography to detect small differences of tissue density. In all three of our cases, many bone fragments could be distin guished more easily on coronal computed tomograms than was possible on conven tional x-ray films. Additionally, air-fluid levels within the maxillary sinus were seen on the computed tomograms of one patient (Fig. 11, bottom). Coronal com puted tomography is also useful for studying the retrobulbar area in patients who have decreased vision, and to loca lize foreign bodies which may not be detected by x-ray examinations. 3 ' 5 Radiation dose to the lens was mea sured by the authors by using thermoluminescent dosimeters on a Rando phantom. During coronal scans with the EMI-5000 total body scanner, the lens dose was 10 to 12 rads when the patient was placed supine. When the patient was able to be placed in the prone positon, lens dose was only 1 rad. These doses were calculated using a 6-mm collimator with a series of five sections at 5-mm intervals. Since both radiographic tomography and coronal computed tomography in volve significant exposure to radiation, they should only be used in patients who may benefit from their use. In the case
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of coronal computed tomography, such patients include those with suspected or proven orbital fractures in whom ad ditional confirmation of muscle entrap ment is required before surgery. Coronal computed tomography might also be con sidered in individuals with possible intraorbital foreign bodies, those with unex plained reduction of vision, and those with possible displacement of bone spicules toward the globe or optic nerve.
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used to help confirm extraocular muscle entrapment in patients with orbital floor fractures. Coronal computed tomography can also be used to examine patients with possible intraorbital foreign bodies, un explained reduction of vision, or severely displaced bone fragments. ACKNOWLEDGMENTS
Stephen H. Sinclair, M.D., C. Davis Belcher III, M.D., and John C. Madigan, Jr., M.D., participated in the care of these patients.
SUMMARY
Coronal computed tomography pro duces orbital scans in a plane that is analogous to Caldwell-view x-ray films. Coronal computed tomography permits simultaneous visualization of the orbital walls and the orbital soft tissues, includ ing all extraocular muscles. Using coronal computed tomography, we studied a series of patients with radiographically proven orbital floor fractures. We studied in detail three of these pa tients, one with a linear orbital floor frac ture, one with a depressed orbital floor fracture, and one with a severely commi nuted orbital floor. In two patients, coro nal computed tomography showed inferi or rectus muscle entrapment, which was confirmed at the time of surgery. In each patient, some bone fragments could be seen more discreetly on coronal comput ed tomography than on conventional polytomes. Coronal computed tomography may be
REFERENCES 1. Zizmor, J.: Fractures of the orbit. In Zizmor, J., and Lombardi, F.: Atlas of Orbital Radiography. Birmingham, Alabama, Aesculapius, 1973, p. 21. 2. Smith, B., Grove, A. S., Jr., and Guibor, P.: Fractures of the orbit. In Duane, T. (ed): Clinical Ophthalmology, vol. 2. Hagerstown, Maryland, Harper and Row, 1976, p.l. 3. Grove, A. S., Jr.: New diagnostic techniques for the evaluation of orbital trauma. Trans. Am. Acad. Ophthalmol. Otolaryngol. 83:626, 1977. 4. Emery, J. M., and von Noorden, F. K.: Trau matic "pseudoprolapse" of orbital tissues into the maxillary antrum. A diagnostic pitfall. Trans. Am. Acad. Ophthalmol. Otolaryngol. 79:893, 1975. 5. Grove, A. S., Jr., Tadmor, R., Momose, K. J., and New, P. F. J.: Computerized tomography for evaluation of fractures and foreign bodies of the orbit. Doc. Ophthalmol. In press. 6. Grove, A. S., Jr., New, P. F. J., and Momose, K. J.: Computerized tomographic (CT) scanning for orbital evaluation. Trans. Am. Acad. Ophthalmol. Otolaryngol. 79:137, 1975. 7. Momose, K. J., New, P. F. J., Grove, A. S., Jr., and Scott, W. R.: The use of computed tomography in ophthalmology.-Radiology 115:371, 1975. 8. Hilal, S. K., Trokel, S. L., and Coleman, D. J.: High resolution computerized tomography and Bscan ultrasonography of the orbits. Trans. Am. Acad. Ophthalmol. Otolaryngol. 81:607, 1976.
Boston, Massachusetts
Fractures of the orbital floor are fre quently accompanied by displacement of bone fragments and by soft tissue dam age. Using Caldwell and Waters views, roentgenograms of the face are used to detect fractures and evaluate distortion of the orbital walls. These roentgenograms may also allow visualization of soft tissue densities, outline prolapsed orbital con tents, and show air-fluid levels. 1 - 3 Radiographic linear tomography (laminography) and hypocycloidal tomogra phy (polytomography) are used to visua lize thin focal plane sections in order to distinguish greater bone and soft tissue details. However, bone fragments may not be seen clearly even on radiographic tomograms. Soft tissue densities found within the sinuses on x-ray films cannot be identified anatomically and may repre sent submucosal blood or prolapsed or bital tissues without muscle entrapment. 4 Other techniques which have been used to evaluate orbital fractures include xeroradiography, positive contrast orbitography, and computed tomography. 3 , 5 Of all these methods, only computed to mography provides detailed visualization of both the bones and the soft tissues of the orbits. Until recently, computed tomography of the head and orbits could only be performed in an axial plane. As a conse quence, cross-sections of the orbits could From the Department of Ophthalmology, Massa chusetts Eye and Ear Infirmary (Dr. Grove), and the Department of Radiology, Massachusetts General Hospital (Drs. Tadmor, New, and Momose), Har vard Medical School, Boston, Massachusetts. Reprint requests to Arthur S. Grove, Jr., M.D., Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA 02114.
only be visualized in the same plane as the paths of the optic nerves. Although the horizontal rectus muscles can be seen clearly on axial scans, it is extremely difficult to visualize soft tissues near the orbital floor and to detect defects in the floor.3,5-8 By using a computed tomographic total body scanner, high resolution scans can be made through the orbits in a coronal plane that is analogous to Caldwell-view x-ray films. This technique of coronal computed tomography has permitted vis ualization of tangential cross-sections of all four orbital walls, including the floor, and of the orbital soft tissues, including all extraocular muscles. 5 S U B J E C T S AND M E T H O D S
Patients at the Massachusetts Eye and Ear Infirmary who suffered serious midfacial trauma were examined by conven tion orbital x-ray films. Those who were suspected of having orbital fractures were usually examined by hypocycloidal to mography as well. Selected patients who had fractures of the orbital floor were then studied by coronal computed tomography to aid in the management of their injuries and to determine the usefulness of coro nal computed tomography for the evalua tion of orbital fractures. Computed tomography was performed with an EMI-5000 (prototype) total body scanner by using 24-cm field. We ob tained most coronal scans by placing the patients supine on an elevated board in the "hanging head" position. Some pa tients preferred the prone "elevated chin" position. The plane of the coronal scans was as near perpendicular to Reid's base line as possible. 5 Some patients could
AMERICAN JOURNAL OF OPHTHALMOLOGY 85:679-685, 1978
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Fig. 1 (Grove and associates). Case 1. Patient has restriction of movement of the right eye in upgaze (left) and downgaze (right) two weeks after trauma to the right orbit.
not tolerate sufficient head extension to achieve these positions, and scan planes of 60 degrees to 80 degrees from Reid's baseline were used. A specially designed 6-mm collimator was used and each patient was studied with three to five sections spaced at 5-mm intervals. We performed 70-second "high accuracy" scans and viewed images as direct enlargements of scan quadrants in order to improve visualization of the bones and soft tissues.
1977. A right hypertropia persisted after injury, and movement of the right eye was restricted in both upgaze and downgaze (Fig. 1). Polytomes demonstrated a linear fracture of the
RESULTS
All patients examined by coronal com puted tomography were first found to have orbital fractures by conventional ra diography. The computed tomograms in each case showed greater details of both the bones and soft tissues than the corre sponding roentgenograms. Three repre sentative cases of orbital floor fractures reported herein demonstrate features that can be visualized by coronal computed tomography to compare this technique with clinical findings and with the results of radiographic studies. These cases in clude a patient with a linear orbital floor fracture, a patient with a depressed orbit al floor fracture, and a patient with a severely comminuted orbital floor. CASE REPORTS
Case 1. Linear Fracture of Orbital Floor with Entrapment of Inferior Rectus Muscle—A 30-yearold woman was struck over the right eye in March
Fig. 2 (Grove and associates). Case 1. Tomographic sections through anterior orbits. Top, Polytome shows densities (arrows) in right maxillary and ethmoid sinuses. Bottom, Coronal computed tomog raphy shows small fracture (black arrow) in right orbital bloor and soft tissues (white arrows) in right maxillary and ethmoid sinuses. Normal tissues visu alized in left orbit include globe (G), levator (L), and medial rectus (M).
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Fig. 4 (Grove and associates). Case 1. Forced traction test shows restriction of elevation of right eye.
Fig. 3 (Grove and associates) Case 1. Tomographic sections through middle orbits. Top, Polytome shows slightly angulated bone fragment (arrow) of orbital floor. Bottom, coronal computed tomography shows soft tissues in right maxillary and ethmoid sinuses. Adjacent to angulated bone fragment is a soft tissue density (small arrowheads), which repre sents orbital component of entrapped inferior rectus muscle. Muscle is outlined by surrounding dark rim of low density fat. Normal tissues visualized in left orbit include optic nerve (N) and inferior rectus (I). Levator and medial rectus are again visible. right orbital floor. In the anterior tomograms, tissue densities were seen in the roof of the right maxillary sinus and in the lateral portion of the right ethmoid sinus (Fig. 2, top). Similar^oft tissue densities were found in the posterior tomograms, where a slightly angulated bone fragment was also visible (Fig. 3, top). Coronal computed tomography similarly revealed densities within the right maxillary and ethmoid sinuses. The linear fracture was clearly outlined in the anterior scans (Fig. 2, bottom). In the posterior scans, the inferior rectus muscle was visible within the fracture (Fig. 3, bottom). In the left orbit, normal
bone and soft tissue details were seen, including the globe, optic nerve, and extraocular muscles. A forced traction test showed restriction of eleva tion of the right eye (Fig. 4). Because vertical move ments of the right eye remained restricted and the patient suffered diplopia in primary gaze, the right orbit was explored two weeks after injury. Orbital fat was found prolapsed into a linear fracture of the floor (Fig. 5). As this tissue was withdrawn, the inferior rectus muscle (Fig. 6) was found incarcerat ed within the fracture. This muscle was extracted, and the defect was covered with a plastic plate. A forced traction test performed at the end of the
Fig. 5 (Grove and associates). Case 1. Exploration of right orbital floor reveals orbital soft tissues prolapsed into linear fracture (arrow).
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Fig. 6 (Grove and associates). Case 1. After extrac tion of prolapsed fat, inferior rectus muscle (arrows) is found incarcerated in orbital floor fracture.
operation revealed no restriction of elevation (Fig. 7). Recovery from surgery was uneventful, with no subjective diplopia persisting after one month. Movements of the right eye were full except for minimal restriction of downgaze (Fig. 8). Case 2. Depressed Fracture of Orbital Floor with Entrapment of Inferior Rectus Muscle—A 30-yearold man was struck over the right eye in May 1977. After injury vertical movements of the right eye were restricted, more severely in upgaze than in downgaze. Polytomes revealed a wide defect in the floor of the right orbit. On these examinations, a fragment of the floor could be seen depressed into the right maxillary sinus (Fig. 9, top). Coronal computed tomography clearly showed the depressed fragment as well as the inferior rectus muscle, which was trapped between the displaced bone and the lateral orbital floor (Fig. 9, bottom). Metallic dental fillings produced radiating artifacts on the lower portion of this scan. Since a forced traction test revealed restriction of elevation of the right eye, and since vertical move ments of the right eye did not improve in functional ly important positions of gaze, the right orbit was
MAY, 1978
Fig. 7 (Grove and associates). Case 1. Forced traction test after completion of surgery shows no restriction of elevation. explored four weeks after trauma. The inferior rec tus muscle was found trapped in the same position seen on the computed tomograms. The prolapsed tissues were withdrawn from the fracture, which was covered by a plastic plate. Although vertical movements of the right eye improved after surgery, the patient still complained of diplopia in extremes of upgaze and downgaze. Case 3. Comminuted Fracture of Orbital Floor with Large Soft Tissue Prolapse—A 28-year-old man was struck over the left eye in March 1977; immediately afterward, movements of the left eye were restricted in all positions of gaze, and the eye was 2 mm more prominent than the right. Polytomes showed opacification of the left maxillary and eth moid sinuses, together with fragmentation and de pression of the orbital floor (Figs. 10, top, and 11, top). Coronal computed tomography demonstrated the displaced bone fragments and delineated soft tissue densities more clearly than the roentgenograms. Air-fluid levels could be seen in the lower left maxillary sinus because the scans were performed with the patient supine in the hanging head posi-
Fig. 8 (Grove and associates). Case 1. Six weeks after operation, patient has no limitation of upgaze (left) and only minimal restriction of downgaze (right), causing no subjective diplopia.
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be localized by radiographic tomography. However, in our cases, bone fragments and fracture defects were better delineat ed by coronal computed tomography than by polytomography. Most fractures of the orbital floor do not require surgical repair. In many patients whose eye movements are limited in all positions of gaze, such as Case 3, the restriction may be caused by nerve dam age, generalized orbital edema, or hemor rhage. A patient with entrapment of the inferior rectus or inferior oblique muscle will usually have restriction chiefly of upgaze and downgaze. The forced trac tion test is useful to help determine when an extraocular muscle is entrapped within a fracture.2,3
Fig. 9 (Grove and associates). Case2. Tomographic sections through middle orbits. Top, Polytome shows fragment of orbital floor (arrow) depressed into maxillary sinus. Bottom, Coronal computed to mography shows soft tissue density including infe rior rectus muscle (black arrow), which can be seen adjacent to depressed floor fragment (white arrow). Dental fillings produce radiating artifacts visible in lower part of scan. tion, with his chin higher than his brow (Figs. 10, bottom, and 11, bottom). Within two weeks after injury, no diplopia was present in primary gaze and movements of the left eye had improved in all other positions of gaze. A forced traction test did not show restriction of verti cal movement of the left eye. At that time the left eye was neither abnormally prominent nor enophthalmic. No surgery was performed and the patient failed to return for additional examination. DISCUSSION
Fractures of the orbital floor can usual ly be visualized on Caldwell or Waters view roentgenograms. Fractures that are not seen on plain films can almost always
Fig. 10 (Grove and associates). Case 3. Tomographic sections through middle orbits. Top, Poly tome shows left paranasal sinus opacification and multiple bone fragments (arrows). Bottom, coronal computed tomography also shows comminuted or bital floor fragments (arrows) which are depressed into the maxillary sinus.
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the computed tomograms showed the in ferior rectus muscle directly adjacent to the fracture. Entrapment of the muscle was clinically suspected in these patients because of limitation of voluntary eye movements in upgaze and downgaze and because of forced traction testing. At the time of surgical exploration, entrapment of the inferior rectus was found and eye movements improved after the operation.
Fig. 11 (Grove and associates). Case 3. Tomographic sections through posterior orbits. Top, As in more anterior study, polytome shows depressed orbital floor (arrow). Bottom, Coronal computed to mography shows soft tissue details, multiple bone fragments, and air-fluid levels (arrows) which are not apparent on corresponding x-ray film.
Surgical intervention is usually re quired only if an orbital floor fracture mechanically impinges upon either the adjacent inferior rectus or inferior oblique muscle to produce significant diplopia in functionally important posi tions of gaze. In some patients, repair of the fracture may be warranted because of cosmetically objectionable lowering of the globe. Rarely, bone fragments which are displaced toward the globe or optic nerve may require surgical reduction. Each of the three patients described in this report had radiographic evidence of a fracture of the orbital floor and a soft tissue density within the maxillary sinus next to the bone defect. In Cases 1 and 2,
When bone is surrounded by air, as in the nose or sinuses, details are usually seen more clearly on polytomes than on computed tomograms. However, when bone fragments are located adjacent to soft tissues, they may be seen more dis cretely on coronal computed tomograms because of the capacity of computed to mography to detect small differences of tissue density. In all three of our cases, many bone fragments could be distin guished more easily on coronal computed tomograms than was possible on conven tional x-ray films. Additionally, air-fluid levels within the maxillary sinus were seen on the computed tomograms of one patient (Fig. 11, bottom). Coronal com puted tomography is also useful for studying the retrobulbar area in patients who have decreased vision, and to loca lize foreign bodies which may not be detected by x-ray examinations. 3 ' 5 Radiation dose to the lens was mea sured by the authors by using thermoluminescent dosimeters on a Rando phantom. During coronal scans with the EMI-5000 total body scanner, the lens dose was 10 to 12 rads when the patient was placed supine. When the patient was able to be placed in the prone positon, lens dose was only 1 rad. These doses were calculated using a 6-mm collimator with a series of five sections at 5-mm intervals. Since both radiographic tomography and coronal computed tomography in volve significant exposure to radiation, they should only be used in patients who may benefit from their use. In the case
VOL. 85, NO. 5
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of coronal computed tomography, such patients include those with suspected or proven orbital fractures in whom ad ditional confirmation of muscle entrap ment is required before surgery. Coronal computed tomography might also be con sidered in individuals with possible intraorbital foreign bodies, those with unex plained reduction of vision, and those with possible displacement of bone spicules toward the globe or optic nerve.
685
used to help confirm extraocular muscle entrapment in patients with orbital floor fractures. Coronal computed tomography can also be used to examine patients with possible intraorbital foreign bodies, un explained reduction of vision, or severely displaced bone fragments. ACKNOWLEDGMENTS
Stephen H. Sinclair, M.D., C. Davis Belcher III, M.D., and John C. Madigan, Jr., M.D., participated in the care of these patients.
SUMMARY
Coronal computed tomography pro duces orbital scans in a plane that is analogous to Caldwell-view x-ray films. Coronal computed tomography permits simultaneous visualization of the orbital walls and the orbital soft tissues, includ ing all extraocular muscles. Using coronal computed tomography, we studied a series of patients with radiographically proven orbital floor fractures. We studied in detail three of these pa tients, one with a linear orbital floor frac ture, one with a depressed orbital floor fracture, and one with a severely commi nuted orbital floor. In two patients, coro nal computed tomography showed inferi or rectus muscle entrapment, which was confirmed at the time of surgery. In each patient, some bone fragments could be seen more discreetly on coronal comput ed tomography than on conventional polytomes. Coronal computed tomography may be
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