Multidetector Computed Tomography of Cervical Spine Fractures in Ankylosing Spondylitis

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1 Acta Radiologica ISSN: (Print) (Online) Journal homepage: Multidetector Computed Tomography of Cervical Spine Fractures in Ankylosing Spondylitis M. P. Koivikko, M. J. Kiuru & S. K. Koskinen To cite this article: M. P. Koivikko, M. J. Kiuru & S. K. Koskinen (2004) Multidetector Computed Tomography of Cervical Spine Fractures in Ankylosing Spondylitis, Acta Radiologica, 45:7, To link to this article: Published online: 09 Jul Submit your article to this journal Article views: 88 View related articles Full Terms & Conditions of access and use can be found at Download by: [ ] Date: 25 December 2017, At: 22:47

2 ORIGINAL ARTICLE ACTA RADIOLOGICA Multidetector Computed Tomography of Cervical Spine Fractures in Ankylosing Spondylitis M. P. KOIVIKKO, M. J. KIURU & S. K. KOSKINEN Department of Radiology, Helsinki University Central Hospital, Töölö Trauma Center, Helsinki, Finland Downloaded by [ ] at 22:47 25 December 2017 Koivikko MP, Kiuru MJ, Koskinen SK. Multidetector computed tomography of cervical spine fractures in ankylosing spondylitis. Acta Radiol 2004;45: Purpose: To analyze multidetector computed tomography (MDCT) cervical spine findings in trauma patients with advanced ankylosing spondylitis (AS). Material and Methods: Using PACS, 2282 cervical spine MDCT examinations requested by emergency room physicians were found during a period of 3 years. Of these patients, 18 (16 M, aged 41 87, mean 57 years) had advanced AS. Primary imaging included radiography in 12 and MRI in 11 patients. Results: MDCT detected one facet joint subluxation and 31 fractures in 17 patients: 14 transverse fractures, 8 spinous process fractures, 2 Jefferson s fractures, 1 type I and 2 type II odontoid process fractures, and 1 each: atlanto-occipital joint fracture and C2 laminar fracture plus isolated transverse process and facet joint fractures. Radiographs detected 48% and MRI 60% of the fractures. MRI detected all transverse and odontoid fractures, demonstrating spinal cord abnormalities in 72%. Conclusion: MDCT is superior to plain radiographs or MRI, showing significantly more injuries and yielding more information on fracture morphology. MRI is valuable, however, in evaluating the spinal cord and soft-tissue injuries. Fractures in advanced AS often show an abnormal orientation and are frequently associated with spinal cord injuries. In these patients, for any suspected cervical spine injuries, MDCT is therefore the imaging modality of choice. Key words: Ankylosing spondylitis; trauma; cervical spine; computed tomography M. P. Koivikko, Department of Radiology, Helsinki University Central Hospital, Töölö Trauma Center, Topeliuksenkatu 5, FIN Helsinki, Finland (fax. z , . Mika.Koivikko@hus.fi) Accepted for publication 19 May 2004 Ankylosing spondylitis (AS, Bechterew s disease, Marie-Strümpell arthritis) is a rheumatic disease of unknown etiology with an estimated incidence of 1.4% (6), most commonly affecting males. The inflammatory process primarily affects the ligamentous structures of the spine and sacroiliac joints, and this becomes radiologically apparent as enthesopathic changes. In advanced stages of the disease, the ligaments ossify, resulting in an ankylosed, osteoporotic vertebral column, a bamboo spine. In emergency medicine cervical spine clearance, AS patients can be considered at high risk, because even a minor trauma can result in spinal fractures (23, 27). Such fractures, most commonly located in the lower cervical spine and cervicothoracic junction (9, 10), are associated with a high incidence of neurological injury and mortality (15, 19, 23). Since these fractures are difficult to diagnose by plain radiography (5, 10), the diagnosis is often delayed, placing the patient at high risk for neurological complications (5). Moreover, treatment of fractures in the fragile, ankylosed spine can be difficult (5, 15, 27). Without appropriate internal or external stabilization, the fractures frequently develop unstable pseudoarthrosis resembling that seen in long tubular bones (7). To avoid these complications, accurate and sensitive diagnostic imaging is essential. Conventional helical computed tomography (CT) is considered an accurate and reliable imaging modality and is widely used in modern emergency radiology (20). In cervical spine trauma, CT is both cost-effective and time-effective, and should be used in screening in high-risk patients (3, 8, 16). As a result of technical breakthroughs, multi-detector CT (MDCT) is faster than conventional helical CT, DOI / # 2004 Taylor & Francis

3 752 M. P. Koivikko et al. resulting in shorter scanning time, fewer motion artifacts, reduced partial volume effects, decreased image noise, high quality multiplanar reformation (MPR), and isotropic viewing (18, 24), all of which substantially increase the diagnostic power of this imaging modality. The purpose of this study was to evaluate MDCT findings in patients with advanced AS with suspected cervical spine fractures and to compare MDCT findings with plain radiography and MRI. Material and Methods This retrospective study took place in a leading level-one trauma center serving a population of 1.4 million people. In our institution, all high-risk patients (including patients with AS) are imaged with CT if cervical spine fracture is suspected. Plain radiography is not routinely used in cervical spine clearance of these patients. Utilizing our hospital s picture archiving and communication system (PACS), all 2282 cervical spine MDCT scans obtained in our hospital between August 2000 and June 2003 were retrieved. All AS patients with trauma and whose cervical spines were initially examined with MDCT were included in the study. All patients underwent routine cervical spine MDCT on a four-section multidetector scanner (Lightspeed QX/I; G.E. Medical Systems, Milwaukee, Wisc., USA). High-resolution scanning parameters were as follows: 1.25 mm collimation, gantry rotation time 1.0 s, pitch 3, table feed 3.75 mm, kv 120/140 (upper/lower cervical spine), mas 280/330, approximate total exposure time 35 s. Routinely, sagittal reconstructions were made with a 1.5-mm slice thickness and reconstruction increment. Coronal reconstructions were made when requested by the radiologist-on-call. All MDCT scans were reviewed for ankylosed spines. Patients were excluded for radiological findings or a medical history of diffuse idiopathic skeletal hyperostosis, rheumatoid arthritis, or other ankylosing diseases. Two emergency radiologists interpreted the MDCT scans and, when available, the plain radiographs of the ankylosed spines by consensus. Radiography included standard anterior and lateral view projections supplemented with a swimmer s-view projection when needed. A third emergency radiologist, blinded from the MDCT and plain radiography results, reviewed the patients MRI scans. Cervical spine MRI, obtained with either a 1.5T scanner (Signa LX 1.5T; G.E. Medical Systems) or a 0.23T open scanner (Outlook GP; Picker Nordstar, Helsinki, Finland), included routine sagittal T1-weighted and T2-weighted fast spin-echo sequences in addition to a sagittal STIR sequence, completed with axial T1-weighted and T2-weighted fast spin-echo sequences and a sagittal T2* sequence, whenever necessary. Results Of the consecutive 2282 cervical spine MDCT scans, 18 (0.8%; 16 M, 2 F; age 41 to 87 years, mean 57) patients met the inclusion criteria. Diagnosis was confirmed from medical records in 17 patients who had been diagnosed with AS from 6 to 40 (mean 27) years prior to trauma. In one patient, symptomatic for 7 years, the diagnosis had not been established, but imaging findings were characteristic for AS. The trauma mechanism was a simple fall in 13 patients (72%), a bicycle accident in 2 (11%), a fall from approximately 2 m in 2 (11%), and a fall from a horse in 1 (6%). Upon arrival, 9 (50%) patients had neurological symptoms indicating a spinal cord injury; 16 (89%) complained of neck pain, 1 was unconscious, and in 1 the clinical symptoms were undocumented. Primary MDCT detected cervical spine injuries in 17 (94%) of these 18 cases, which yields an estimated annual incidence of 4.0 per million. At our institution, this means approximately 1 case in every 2 months. Table 1 is a summary of MDCT findings, with radiography and MR correlation, and relevant clinical detail including neurological assessment using the Frankel grading (12). Based on MDCT, altogether 31 fractures and 1 facet joint subluxation were detectable. Seven patients had multiple fractures, in two of them non-contiguously. Upper cervical spine (C0 C2) injuries were found in 3 (17%) patients: 1 had fractures in an ankylosed atlanto-occipital joint, C2 laminae, and a type I odontoid process fracture (Fig. 1); 2 patients had a combination of a Jefferson s fracture and a type II odontoid process fracture (Fig. 2). Fourteen (78%) patients had transverse fractures extending through all three columns. In eight, the anterior part of the fracture ran through the vertebral body and in six through the ossified longitudinal ligaments and intervertebral disk. In 11 of them the fracture was oblique, reaching two vertebral levels in six (Fig. 3). In all oblique transverse fractures, the posterior column injury was located higher than the anterior column injury. The transverse fracture affected C6, or adjacent intervertebral spaces (C5/6 or C6/7), in 12 (85%) of

4 Multidetector CT of Cervical Spine Fractures 753 Table 1. Radiological findings and clinical details in 18 patients with ankylosing spondylitis Downloaded by [ ] at 22:47 25 December 2017 Patient no. Age (years) Gender Accident Primary MDCT findings the cases. Three of the transverse fractures were posteriorly dislocated, three anteriorly. These numbers do not include case no. 3, with an apparently false-negative MDCT scan of a transverse fracture (Fig. 4). In addition to those spinous process injuries, which were a part of a transverse fracture, MDCT detected eight spinous process fractures in five patients. In all of these, a transverse fracture was visible in the vicinity. The additional findings included isolated fractures of a transverse process, an articular process, and one subluxation of a nonankylosed facet joint. Plain radiographs were available for 12 (67%) cases, but in 11 (92%) of them, lateral view radiographs were inadequate, failing to visualize the entire cervical spine. The cause was the cranial position of shoulder shadows, obscuring the lower cervical spine up to C4 in two (18%), up to C6 in four (36%), and up to C7 in five (45%) cases. The Dislocation Visible on X-ray MRI SCI** SCI MRI*** Surgery 1 56 Male Simple fall C5-6 two-level TF 7 mm, ant. N/A N/A E N/A Posterior 2 62 Male Simple fall C6 TF None No Yes C None Anterior 3 87 Male Simple fall None* No N/A E N/A Conserv Male Fall from bicycle C6/7 TF 6 mm, ant. No Yes E None Conserv Male Simple fall C5-6 two-level TF None Yes Yes E NHC Posterior C3-4 spinous process fr. No No 6 47 Male Fall from bicycle Jefferson s fr. None Yes No A HC Posterior Type-II odontoid process fr. 8 mm, post. Yes Yes 7 65 Male Simple fall C4/5 TF 4 mm, post. Yes Yes A HC Anterior 8 56 Male Fall from height Jefferson s fr. None Yes No A T Posterior Type-II odontoid process fr. 4 mm, post. Yes Yes C5/6-6/7 two-level TF None No Yes C2-4 spinous process fr. Yes No C4/5 articular process fr. No No 9 60 Male Simple fall C7/Th1 facet subluxation 3 mm, ant. No Yes C HC Anterior Male Simple fall C6/7 TF 10 mm, ant. N/A N/A B N/A Posterior C7 spinous process fr Male Simple fall Ankylosed C0/C1 fr. 3 mm, post. No N/A E N/A Conserv. Type-I odontoid process fr. 3 mm, post. Yes C2 bilateral laminar fr. No Male Simple fall C6 TF None No N/A E N/A Posterior Female Fall from horse C7-Th1 two-level TF None N/A Yes E None Anterior Male Simple fall C7 TF None N/A Yes D NHC Anterior Male Fall from height C6 TF None Yes N/A E N/A N/A C7 spinous process fr. Yes Th2 transverse process fr. No Male Simple fall C5-6 two-level TF None N/A Yes D HC Anterior Male Simple fall C5/6 TF 4 mm, post. No Yes D C Posterior Female Simple fall C5-6 two-level TF 3 mm, post. N/A N/A E N/A Posterior C4 spinous process fr. fr.~fracture; TF~transverse fracture extending through all three columns; post.~posterior; ant.~anterior; N/A~not available; Conserv.~conservative treatment. *False-negative radiography and multidetector CT (MDCT) of a transverse fracture. **SCI Spinal cord injury assessed by Frankel s classification (12): A. Complete motor and sensory loss; B. Preserved sensation only; C. Non-functional motor activity; D. Functional motor activity; E. Normal neurology below injury level. ***Spinal cord injury MRI findings: NHC~non-hemorrhagic contusion; HC~hemorrhagic contusion; T~transsection; C~compression without medullopathic findings. additional projections (swimmer s view) obtained for eight were of acceptable diagnostic quality in only one (13%) case. Plain radiography detected only 12 (48%) of the 25 fractures detected by MDCT: all three odontoid fractures, both Jefferson s fractures, four (67%) of six spinous process fractures, and three (33%) of nine transverse fractures. Two articular-process injuries, one atlanto-occipital joint fracture, one fracture of C2 laminae, and one transverse process fracture were undetected. In the primary phase, 11 (61%) patients also underwent cervical spine MRI (within 0 to 3, a mean 0.9 days after the MDCT scan), eight of them 1.5T, and three 0.23T open MRI. In these patients, of 20 fractures detected by MDCT, MRI detected 12 (60%). No additional fractures were detected by MRI. MRI detected all nine transverse fractures, visualizing both the anterior and the posterior

5 754 M. P. Koivikko et al. column injury in seven and only the anterior column injury in two. MRI revealed spinal cord abnormalities in a total of 8 (72%) of the 11 patients. In transverse fractures, 6 (67%) of the 9 cases had spinal cord abnormalities: 1 spinal cord compression without medullopathic findings, 2 nonhemorrhagic and 2 hemorrhagic contusions, and 1 transsection. Three transverse fractures had associated spinal epidural hematomas, none of which caused medullary compression. MRI detected the one facet subluxation associated with a hemorrhagic contusion, and both odontoid fractures, with an associated hemorrhagic contusion and minimal spinal epidural hematoma in one. Both Jefferson s fractures were missed by MRI as well as five spinous process fractures and one articular process fracture. There was one false-positive odontoid process fracture on MRI, caused by non-traumatic erosions. Downloaded by [ ] at 22:47 25 December 2017 Discussion In our series of 18 patients with advanced AS, we found MDCT to be an extremely powerful imaging tool, detecting significantly more cervical spine fractures than did plain radiography. Although MRI could detect the most serious injuries with comparable sensitivity, MDCT was superior in demonstrating fracture morphology and delineation. We found that in advanced AS, fractures of the osteoporotic, anatomically distorted spine are often non-anatomically oriented a single fracture line, axially oriented in the anterior vertebra or intervertebral space, can also extend cranially for one or two vertebral levels in the middle and posterior column structures. Sagittal and coronal MPR images were invaluable in interpreting these findings. Spinal fractures are approximately 3.5-fold more common in AS patients than in the general population (9, 23), with 75% of the fractures located in the cervical spine (17), with a predilection for the lower cervical spine and cervicothoracic junction (10, 15, 26, 27). Osteoporosis, long lever arms present in the rigid spine, and kyphotic posture, positioning the head forward in a more vulnerable position, are probable factors causing the high susceptibility to fractures. The most Fig year-old man (case no. 11) who, after a 40-year-history of ankylosing spondylitis and several previous cervical spine fractures, sustained an upper cervical spine fracture from a simple fall. A. Plain radiography shows a fracture of the odontoid process (arrow); an old posterior atlanto-axial fusion and an anterior C3-6 plate stabilization are also visible. B. MDCT sagittal reformation image demonstrates fractures of the ankylosed atlantooccipital joint (arrow) and C2 laminae (arrowhead). C. Midline sagittal reformation shows the type I odontoid fracture (arrow) and an older Anderson lesion (arrowheads).

6 Multidetector CT of Cervical Spine Fractures 755 Fig year-old man (case no. 6) with AS, tetraplegic after falling from a bicycle. A. Plain radiography lateral view reveals a type II fracture (arrow) of the odontoid process, which is posteriorly dislocated (arrowheads). B. MDCT midline sagittal reformation showing the posteriorly dislocated type II odontoid process fracture (arrow). C. Axial image at the level of C1 shows a Jefferson s fracture (arrows) with associated transverse ligament avulsion fragment (arrowhead). D. T2-weighted (1.5T, TR/TE 4000/105, 3-mm slices with 4-mm spacing) sagittal MR image shows hemorrhagic contusion (arrowheads) of the spinal cord.

7 756 M. P. Koivikko et al. Fig year-old woman (case no. 13) who, after a 27-year history of AS, fell from a horse. A. At the level of C7/Th1, MDCT reveals discontinuity of the ossified anterior longitudinal ligament (arrow) and anterior widening of the intervertebral space. A suspicious line extends upwards following the posterior margin of C7 vertebral body (arrowheads). B. Fracture in the posterior aspect of C7 vertebral body is confirmed from the axial images (arrows). C. Sagittal reformation image reveals the same fracture line running through C7 pedicle (arrow) and ossified C6/7 facet joint (arrowhead). D. T2-weighted (1.5T, TR/TE 4000/105, 3-mm slice thickness with 4-mm spacing) sagittal MR image shows anteriorly a C7/Th1 intervertebral discoligamentous rupture (arrow).

8 Multidetector CT of Cervical Spine Fractures 757 Fig year-old man (case no. 3) with AS who, after a simple fall, complained of neck pain. The primary MDCT was false-negative both in the initial clinical setting and in our study. A. Plain radiography lateral view shows no fractures. Note the extreme osteoporosis of the cervical spine compared to the occipital bone (asterisk). B. Sagittal reformations of the primary MDCT scan show no evidence of fracture in the ankylosed articular pillars. Subtle inconsistency in the bone structure of the articular pillar is visible in retrospect (arrow). C. No fracture is evident in anterior column structures. The patient was discharged from hospital. Discontinuity of the ossified anterior longitudinal ligament is a finding that could, in retrospect, be suspected from this scan. D. Six weeks later, he sustained another simple fall and was tetraplegic on admission. MDCT reveals pseudoarthrosis of a transverse fracture running through the anterior part of C4 vertebral body and C3/4 intervertebral space (arrow). E. Fracture extending through articular pillar structures (arrows).

9 758 M. P. Koivikko et al. Fig. 4. (Continued.) common trauma mechanism is hyperextension (17, 19). Even minor trauma can result in an unstable fracture (9, 15, 23), a fact supported by our finding that 72% of the injuries resulted merely from a simple fall. In the general population, approximately onethird of the cervical spine fractures are located in the upper (C0 C2) cervical spine (14). We found upper cervical fractures in only 17% of our AS patients, in harmony with figures from earlier reports (9, 23, 27), in which the vast majority of the fractures in AS patients are subaxial. Only a few odontoid process fractures have been reported in AS patients (21). In the general population, type I odontoid process fractures, fractures of the odontoid tip, are extremely rare (14). The type I fracture in our series is, to the best of our knowledge, the first reported in an AS patient. In plain radiography of AS patients, difficulties frequently occur in obtaining lateral-projection radiographs of the lower cervical spine. Due to the rigidity of the spine, a swimmer s view is also difficult to obtain, and can be a neurologically hazardous maneuver. Despite the limited number of plain radiographs, obtained for only two-thirds of the cases in our study, some observations deserve closer attention: in 92%, plain radiography was unable to visualize the entire cervical spine. The 48% sensitivity, with only 33% of transverse fractures detected, is the most discouraging. If, however, plain radiography is the only imaging modality available, even the slightest abnormality should be considered suggestive of a serious fracture. For example, as demonstrated in our series, a simple spinous process fracture should alert the radiologist to search for a transverse fracture in the vicinity. CT has proved to be a safe and rapid contributory imaging modality in these injuries, yielding valuable information on fracture delineation and spinal canal compromise (11, 13, 26 28). On the basis of our MDCT results, most of the transverse fractures are located at the level of, or in the vicinity of C6. Whichever imaging modality is chosen for spinal clearance in AS patients, it should be possible to visualize even the lower cervical spine and the cervicothoracic junction. Experience with MRI in cervical spine injuries of AS patients is increasing (22, 25, 26). MRI, obtained in 61% of our cases, was superior to MDCT in the assessment of soft tissue and spinal cord injury. Many AS patients, however, are not eligible for MRI. Monitoring of the patient is difficult during MRI, which also takes a considerably longer time to perform than does CT. In addition to the contraindications posed by pacemakers, both MRI-incompatible anesthesiology equipment and skull traction devices often make MRI impossible. Moreover, because these patients occasionally have a severe kyphotic deformity, they cannot fit properly into the coil or even into the conventional closed-bore MR scanner. MR systems with an open design and circular surface coils, however, are a feasible option. In our series, 50% of the patients upon arrival had a spinal cord injury. Such injuries are common in cervical spine injuries of AS patients (5, 9, 10, 15, 23, 26). MURRAY et al. (19) found a 57% incidence of neurological injury and 35% mortality, compared with a respective 18% and 20% in otherwise normal spines, and the most common cause of death is respiratory complications (1, 9, 23, 27). The neurological injury is occasionally complicated, or is even caused by traumatic spinal epidural hematomas (SEH), which are more common in AS patients than in patients who have sustained a fracture in an otherwise healthy spine (4). In AS patients, the SEHs are usually located posterior to the dural sac (22). In our series, we found SEHs in 36% of patients who underwent MRI. All hematomas were located posterior to the dural sac, and none required surgical intervention. Our high rate of positive findings in AS patients indicates that a very low index of suspicion of fracture, and vigorous imaging even after the very most trivial trauma is justified. Standards of imaging should reflect the evolution of imaging

10 methods (2). Radiography can no longer be considered sufficient for screening AS patients. We therefore recommend that MDCT serve as the primary screening tool. It should be noted, however, that even MDCT risks false negatives. If MDCT is unavailable, we recommend a good quality single-slice helical CT with thin collimation. Altered biomechanics, with long lever arms present in the ankylosed spine, makes even a nondisplaced, hair-thin fracture potentially very unstable. In our opinion, in AS patients complaining of neck pain after any trauma, the best choice is MRI of the cervical spine, if MDCT turns out negative. Conversely, if MRI is opted for use as the primary screening modality, a negative MR scan should be confirmed by MDCT. If both turn out negative, careful clinical and radiological follow-up is wise. 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