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Cervical Spine Injuries in Children, Part I: Mechanism of Injury, Clinical Presentation, and Imaging
The Journal of Emergency Medicine, Vol. 41, No. 2, pp. 142–150, 2011 Copyright © 2011 Elsevier Inc. Printed in the USA. All rights reserved 0736-4679/$–see front matter
doi:10.1016/j.jemermed.2009.11.034
Original Contributions
CERVICAL SPINE INJURIES IN CHILDREN, PART I: MECHANISM OF INJURY, CLINICAL PRESENTATION, AND IMAGING Joshua S. Easter,
MD,*
Roger Barkin,
MD,†
Carlo L. Rosen,
MD,‡
and Kevin Ban,
MD§
*Department of Emergency Medicine, Children’s Hospital of Boston, Boston, Massachusetts, †Department of Pediatrics, University of Colorado, Denver, Colorado, ‡Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, and §Pediatric Trauma Center at Meyer Hospital, Florence, Italy Reprint Address: Carlo L. Rosen, MD, Harvard Affiliated Emergency Medicine Residency, Beth Israel Deaconess Medical Center, One Deaconess Rd., West CC2, Boston, MA 02215
e Abstract—Background: Cervical spine injuries are difficult to diagnose in children. They tend to occur in different locations than in adults, and they are more difficult to identify based on history or physical examination. As a result, children are often subjected to radiographic examinations to rule out cervical spine injury. Objectives: This two-part series will review the classic cervical spine injuries encountered in children based on age and presentation. Part I will discuss the mechanisms of injury, clinical presentations, and the use of different imaging modalities, including X-ray studies and computed tomography (CT). Part II discusses management of these injuries and special considerations, including the role of magnetic resonance imaging, as well as injuries unique to children. Discussion: Although X-ray studies have relatively low risks associated with their use, they do not identify all injuries. In contrast, CT has higher sensitivity but has greater radiation, and its use is more appropriate in children over 8 years of age. Conclusion: With knowledge of cervical spine anatomy and the characteristic injuries seen at different stages of development, emergency physicians can make informed decisions about the appropriate modalities for diagnosis of pediatric cervical spine injuries. © 2011 Elsevier Inc.
INTRODUCTION Pediatric patients possess many unique problems when they injure their cervical spines. Due to their anatomy, they are prone to different types and locations of injuries than adults. These can be difficult to identify with either the history or physical examination. As a result, many children with moderate to major trauma require plain films of the cervical spine (C-spine). These also are not straightforward, as the child’s changing anatomy makes it difficult to determine which findings on imaging represent true abnormalities. Many findings require additional imaging to differentiate them further. With knowledge of the pediatric C-spine and utilization of the appropriate imaging modality for a particular complaint and mechanism, these difficulties can be overcome and emergency physicians can successfully identify cervical spine injuries in children. This is crucial because these injuries are associated with high morbidity and mortality. Cervical spine injuries require meticulous diagnostic and management strategies to reduce long-term sequelae. Approximately 72% of spinal injuries in children ⬍ 8 years of age occur in the cervical area (1). Estimates for the mortality associated with these injuries vary from 4% to 41%. As many as 67% of children have neurologic deficits, and 66% have-
e Keywords— cervical spine; trauma; imaging; pediatric injury
RECEIVED: 2 June 2009; FINAL SUBMISSION ACCEPTED: 22 November 2009
RECEIVED:
17 September 2009; 142
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concomitant head or other major organ trauma, underlining the importance of accurate and timely diagnosis (2– 4). However, the lack of specificity of clinical signs and symptoms, and the normal anatomic variants in young children make the diagnosis more difficult.
MECHANISM OF INJURY Multiple different mechanisms can lead to C-spine injuries in children. Due to greater mobility of the pediatric spine, laxity of the ligaments, shallow and angled facet joints, and underdeveloped spinous processes, children younger than 8 –10 years of age are less prone to spinal fractures than adults (5). Sixty percent of injuries occur in boys. Motor vehicle collisions, falls, sports injuries, diving, and electrical accidents are generally causative (6).
Patient Age Patient age affects the type, location, and severity of injury to the cervical spine. Although children younger than 8 years of age are less likely to sustain bony fractures, they are at higher risk for injuries to the cervical cord due to their large head size compared to their thin cervical musculature. This disproportion in head size is inversely proportional to age, leading to higher torque forces with acceleration and deceleration in younger children. Autopsies have shown that the bony spinal column in infants can withstand 2 inches of stretch without tearing, while the neurovascular structures of the cord shear with stretching beyond a quarter of an inch (7). As a result of this weakness of the cord coupled with the larger forces created by their prominent heads, younger children’s cervical injuries are often sufficient to injure the spinal cord, resulting in immediate death. Younger children who survive the initial impact of the trauma tend to have relatively minor cord injuries with few cervical spine fractures due to the greater mobility of their spines and laxity of their ligaments. In children over the age of 8 years, the bony spine is less mobile, and similar levels of force that would cause a cord injury in younger children lead only to bony injury in older children. Nearly 80% of older children develop a fracture as the primary manifestation of cervical injury instead of the isolated cord injury encountered in younger children (8). The age of the child may correlate with the location of the injury. In children younger than 8 years old, 87– 100% of injuries occur at C3 or higher in the cervical column (9,10). The fulcrum for motion in this age group is located at C2–C3, as opposed to adults, where it is found at C5–C6 (11). Although there is a propensity for
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higher cord injuries, other injuries have been identified at all levels of the spinal column in younger children, suggesting that injuries in young children are not limited to the higher cervical cord exclusively (3). Meanwhile, children over the age of 12 years have anatomy similar to adults, resulting in similar injury patterns, with relatively more injuries occurring in the lower cervical spine (12). Finally, age affects the severity of the injury. Although spinal injuries in younger children are less common, there is higher morbidity and mortality. In a review of 179 pediatric trauma cases, the incidence of neurologic deficit in children ⬍ 8 years of age was 62% compared to 47% in older children (13). This is likely attributable to the aforementioned anatomical differences in the young pediatric spine, which predispose young patients to cord damage over bony injury. Similarly, the mortality rate is higher in children. In a retrospective review of 103 consecutive C-spine injuries at a pediatric trauma center, the mortality rate was 18%, significantly higher than the approximately 10% mortality identified in adults (10). Surviving children have superior outcomes when compared to adults, likely due to their greater healing potential. As many as 90% of patients recover partially and 60% recover completely (14). This healing potential is seen in both younger and older children.
Direction of Force As in adults, the direction of the force applied during the accident influences the nature and location of the resulting fracture and its subsequent stability in children (Table 1).
CLINICAL PRESENTATION Patients with spinal injuries should undergo neurologic examinations including motor, sensory, and reflex exam-
Table 1. Cervical Spine Fractures based on Mechanism
Mechanism Hyperflexion
Hyperextension
Axial Load
Injury Flexion teardrop Bilateral facet dislocation Unilateral facet dislocation Anterior subluxation Wedge fracture Spinous process fracture Hyperextension dislocation Extension teardrop Hangman’s fracture (pedicles C2) Burst fracture Jefferson (C1)
Stability (U ⫽ Unstable, S ⫽ Stable) U U S U/S U S U U U U U
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inations, as well as a thorough examination for associated injuries. Nearly one-third to one-half of all children with cervical cord injuries demonstrate neurologic deficits (15,16). Furthermore, 40% of spinal cord injuries are associated with head trauma, necessitating a complete cranial examination. Attention should be paid to the patient’s breathing and circulation because injuries to the cord at C3–C5 can result in phrenic nerve failure with subsequent hypoventilation or apnea. Similarly, spinal shock can affect the cardiovascular system, leading to hypotension or bradycardia. Any of these findings are ominous and can provide indirect evidence of a cervical spine injury when no other direct signs or symptoms of spinal trauma are present. Finally, no one particular symptom or sign provides both adequate sensitivity and specificity on physical examination to exclude a cervical spine injury.
IMAGING Due to the difficulty in detecting cervical spine injuries based on history and physical examination in pediatric trauma patients, imaging is frequently necessary. There is no consensus for when further evaluation with imaging is appropriate to diagnose a pediatric spinal cord injury. Lally et al. showed that routine plain films in all pediatric trauma patients have a low yield; only 1 in 187 patients possessed a fracture on routine X-ray study (17). However, failure to perform radiographic imaging on patients deemed injury free based on history and physical examination alone can result in delayed diagnosis of a fracture. Dietrich et al. classified 86% of delayed diagnoses of spinal injuries as a result of clinical misinterpretation of the original injury as “trivial” and subsequent failure to evaluate the patient with imaging sufficiently (18). This suggests that routine plain films may be necessary to avoid missing such fractures. The American College of Surgeons supports this contention, advocating plain films of the cervical spine as a part of the initial major trauma evaluation in all children (19). There is no consensus about when imaging should be obtained in pediatric patients.
Guidelines for Imaging Several studies have attempted to determine the appropriate clinical scenario for imaging the pediatric C-spine by identifying factors that place children at high risk for cervical spine injury. The first retrospective review of C-spine imaging in children assessed 206 trauma patients under the age of 16 years in whom C-spine plain films were obtained. The presence of neck pain, neck tender-
ness, limitation of mobility, a history of direct trauma to the neck, or abnormal neurologic examination identified 98% of C-spine injuries with a specificity of 54%. By imaging only patients with these signs or symptoms, 58 of 59 C-spine injuries were identified, and plain film utilization could have been reduced by 38%. The only missed injury involved damage to the cord but no bony injury (20). However, in this review, only 5% of patients underwent computed tomography (CT) scan or magnetic resonance imaging (MRI), and as a result, several injuries may have been missed that would have been visible with these modalities. Laham et al. expanded on this review by attempting to identify criteria that would be 100% sensitive for spinal injury in their retrospective analysis of 268 children (21). When children could communicate about their symptoms (i.e., they were over the age of 2 years) and did not have a debilitating head injury, the presence of neck pain was 100% sensitive for cervical injury. However, in their analysis, only 80% of patients received plain films and therefore, they may have missed fractures occurring in patients without neck pain. These retrospective reviews of C-spine injury do not provide sufficient evidence to create definitive guidelines for imaging in the emergency department (ED). Emergency physicians utilize the NEXUS criteria in adult patients to determine the need for C-spine imaging, and many practitioners extrapolate guidelines from the NEXUS criteria and apply them to children (22). The NEXUS analysis showed that imaging was unnecessary if patients had no midline cervical tenderness, no focal neurologic deficits, normal alertness, no intoxication, and no painful distracting injury. These criteria had a sensitivity of 99% for adult cervical spine injury (95% confidence interval [CI] 98 –99.6%). However, caution must be exercised in applying these guidelines to children. A retrospective review of 447 patients younger than 19 years of age found a sensitivity of 100% for the NEXUS criteria (23). In a multicenter trial of 3065 pediatric patients, Viccellio et al. considered children possessing any of the NEXUS criteria as high risk, whereas those without any of the criteria were deemed low risk (24). Of the 603 low-risk patients, none had a C-spine injury on three-view plain films. Thirty children had a C-spine injury, and each of these had at least one of the NEXUS criteria; the NEXUS criteria had a sensitivity of 100% (95% CI 88 –100%) and specificity of nearly 20%. Utilization of the NEXUS criteria would have reduced imaging by approximately 20% (24). In addition, adoption of the NEXUS rules by ED staff in one study reduced the need for surgical consult by 60%, without any increase in missed injuries (25). Despite this apparent confirmation of the validity of the NEXUS criteria for children in the ED, several limitations exist, particularly in younger patients. Viccel-
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lio’s confirmation of the NEXUS criteria in children included only 4 patients with C-spine injuries who were ⬍ 9 years of age and no patients ⬍ 2 years of age (24). This low number of injuries in the younger age groups is not an accurate reflection of the pathophysiology of cervical spine injuries. Younger children have a higher risk of spinal cord injury than older patients. In addition, being incapable of verbal communication renders them significantly more prone to having an undiagnosed neck injury. The low number of spinal cord injuries in younger children observed in Viccellio’s analysis likely arose because only a small number of younger children were enrolled; only 2.8% of patients in the study were ⬍ 2 years of age (24). Furthermore, the 95% CI cited by Viccellio, indicating the sensitivity of the NEXUS criteria, could be as low as 88% in children. This sensitivity is significantly lower than the 99% lower end of the confidence interval identified in adults with the NEXUS criteria and would result in a substantial number of potentially devastating missed injuries. There is still no consensus by professional organizations on the appropriate variables to include when making a decision about imaging the cervical spine in children. The American Association of Neurological Surgeons (AANS) recommends application of the NEXUS criteria in children over 9 years of age; in children who are alert, who have no neurologic deficit, midline C-spine tenderness, painful distracting injury, or intoxication, imaging is not required (26). Meanwhile, Lee et al. attempted to create consensus guidelines incorporating the various strategies employed in different disciplines (27). To increase the sensitivity of detecting injuries in children, they suggested expanding the criteria and imaging the C-spine whenever the NEXUS criteria were present or there was significant mechanism of injury, a history of transient neurologic symptoms or physical evidence of neck trauma, significant trauma to the head or face, or the child was inconsolable (27). Other authors suggest imaging the spine whenever the patient has a Glasgow Coma Scale (GCS) score of ⬍ 14 (28). Clearly, there is no consensus on the appropriate criteria for determining when children require C-spine imaging in the ED. However, it seems appropriate to apply the NEXUS criteria in children aged 9 years and older. For younger children, any concerning clinical history, signs, or symptoms in addition to the presence of any of the NEXUS criteria should lead to imaging with plain films.
Types of Plain Films There is also disagreement about the type of X-ray studies that should be obtained once the provider elects to image the cervical spine. The cross-table lateral identifies
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as many as 98% of cervical spine fractures, dislocations, or subluxations in children (18). However, several studies have found lower sensitivities when it is employed in isolation; it may miss as many as 20 –25% of fractures (20,29 –31). Therefore, providers typically acquire the anteroposterior (AP) view of the cervical spine to complete the cross-table lateral study. This view can identify lateral mass fractures and transverse process fractures not seen on the lateral film. When used in combination with the lateral view, sensitivity has been shown to increase to 87% in children ⬍ 8 years of age (32). Most trauma centers also obtain odontoid or openmouth views in cooperative patients, although the need for these views is more controversial. A multicenter retrospective review identified one case out of 51 Cspine injuries where the odontoid view provided the crucial view for diagnosing the injury. In children ⬍ 9 years old, the odontoid view did not provide any additional benefit. The authors concluded that in children ⬍ 9 years of age, the open-mouth view was unnecessary (32). Similarly, a survey of 432 pediatric radiologists revealed that only 46 fractures were seen on only the odontoid view in children ⬍ 5 years of age. The resulting low missed fracture rate (0.007 per year per radiologist) was interpreted by the authors as suggesting that the odontoid view should not be routinely acquired in children ⬍ 5 years old (32). Most fractures of the odontoid in younger children occur at the dens-body synchondrosis, the weakest area of C2, and these are typically apparent on a lateral X-ray study (32). Further complicating this issue is the difficulty in obtaining compliance for open-mouth views in young children. As a result of these factors, the AANS and the Congress of Neurological Surgeons recommend only AP and lateral X-ray studies in children ⬍ 9 years of age (26). Each of the aforementioned studies of the odontoid view had limitations. The first analysis included only 51 patients with actual C-spine injuries. The second study involved only radiologists, not emergency physicians, and suffered from weaknesses from its retrospective design as well as recall bias. Other reviews have shown that the odontoid view, combined with the AP and lateral views, increases sensitivity for C-spine injury to 94% (33). Further research is needed before definitively stating that the odontoid view is truly unnecessary, particularly in older children. In contrast to the odontoid view, flexion, extension, and oblique views are more widely accepted as having a minimal role in the initial ED assessment of C-spine injuries. Flexion and extension views are intended to demonstrate cervical instability, atlantoaxial joint instability, and ligamentous injury. The AANS recommends this approach (26). However, a review of 224 pediatric cases did not reveal any cases where flexion-extension
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X-ray studies aided in diagnosis in the ED (34). Also, false negatives can be obtained in children when they are frightened, in pain, or guarding their necks (12). False positives may arise from vertebral angulation seen on flexion views secondary to normal variation in ligament laxity (35). These views also require additional resources because at most institutions, physicians must passively flex and extend the patient’s neck for these films to prevent possible spinal cord damage from movement of the cervical spine. Moreover, nearly 30% of patients cannot adequately flex or extend the neck to provide these views (36). As a result of these complications, flexion and extension views should be utilized only 7 to 28 days after the injury (37). Oblique views are occasionally obtained to look at the pedicles, posterior lamina, and articular masses. These views are typically employed in adults and children when the AP, lateral, and odontoid views are normal but the patient has persistent pain. Ralston et al. demonstrated that oblique views are of little utility in children (38). Their retrospective review of 109 children showed no abnormalities on oblique views when the AP and lateral views were normal. For one patient with equivocal AP and lateral views, the oblique view demonstrated subluxation.
Interpretation of Plain Films When reading a cervical spine plain film series, a systematic process helps to identify injuries. A thorough analysis of the C-spine requires measurement of several intervals in the upper cervical spine because both atlantoaxial and atlantooccipital instability is much more common in children than in adults. To assess atlantoaxial stability (Table 2), several measurements should be made: 1) The Wackenheim’s clivus line is drawn along the posterior aspect of the clivus and should intersect the odontoid or be tangential to it (Figure 1). If this does not
Table 2. Measures of Atlantoaxial Instability in Children on Cervical Spine Plain Films Measures
Normal Findings (Distances Except Where Specified)
Wackenheim’s clivus Line along posterior edge of clivus line should intersect odontoid Power’s ratio Ratio of tip of basion to anterior atlas to opisthion to posterior atlas ⬍ 1 Harris criteria Basion and odontoid ⬍ 12 mm Atlantodens interval Posterior atlas to anterior dens ⬍ 5 mm Rule of thirds Spinal canal: 1/3 dens, 1/3 cord, 1/3 empty
Figure 1. Wackenheim’s Clivus Line—line drawn along the posterior portion of the clivus intersects the odontoid, making atlantoaxial instability less likely.
intersect or run perpendicular to the odontoid, it suggests atlantoaxial instability. 2) The Powers ratio measures the distance from the tip of the basion (anterior margin of the skull’s greater foramen) to the posterior arch of the atlas, and divides this value by the distance from the opisthion (posterior margin of the greater foramen) to the posterior aspect of the anterior arch of the atlas. If this ratio is ⬎ 1, it suggests an anterior atlantoaxial dislocation (Figure 2). However, a ratio ⬍ 1 does not rule out a posterior or longitudinal dislocation (39). 3) The rule of 12, or Harris criteria, are the criteria most easily employed in the ED. The distance between the basion and the rostral tip of the odontoid and the distance between the basion and the rostral position of the posterior cortical margin of the axis should both be ⬍ 12 mm (Figure 3). This rule is not always valid in children ⬍ 13 years of age (40). Moreover, each one of these criteria is limited by difficulty in identifying the requisite bony landmarks on plain films. The atlantodens interval and the rule of thirds are more readily measured in the ED (Table 2). The atlantodens interval, measuring the distance between the posterior cortex of the anterior arch of the atlas to the anterior cortex of the dens, should be ⬍ 5 mm (Figure 4). An interval larger than this indicates atlantoaxial instability (41). A more clinically relevant rule in the ED for atlantoaxial instability is the rule of thirds: the dens should fill one-third of the spinal canal space, the spinal cord one-third of the space, and the final third should be free. If this free space is reduced in size, it suggests atlantoaxial instability (35). The soft tissue distances also
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A B
A
B
Figure 2. Powers ratio—the ratio of the distance from the basion to the spinolaminar line of the atlas (line labeled A) to the distance between the anterior tubercle of the atlas and opisthion (posterior edge of the foramen magnum) (line labeled B) should be less than one.
Figure 4. Atlantodens interval—the distance between the anterior arch of the atlas (line labeled A) and anterior portion of the dens (line labeled B) should be < 5 mm.
Computed Tomography should be measured. The retropharyngeal space should be ⬍ 7 mm and the retrotracheal space ⬍ 14 mm (42). Soft tissue swelling greater than these values suggests the presence of an underlying fracture (Figure 5).
In the 21st century, many trauma centers are routinely utilizing CT instead of plain films to assess the cervical spine. A protocol of obtaining a CT scan in all adult
B A
Figure 3. Harris Criteria—the distance between a line drawn along the posterior cortex of the body of C2 and the rostral portion of the odontoid (line labeled A) should be within 12 mm (line labeled B) of the basion.
Figure 5. Swelling of the retropharyngeal space—the retropharyngeal space measures approximately 10 mm at C2, indicative of an underlying fracture, which is apparent in the lamina of C2.
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patients, coupled with an MRI study in patients presenting with neurologic deficits, had a sensitivity of 99% and specificity of 100% for cervical injuries. Only one of 100 cervical injuries was missed, and this missed injury occurred in a patient with a preexisting syringomyelia (43). When compared with plain films, CT scan identified eight of 20 C-spine injuries that were not visible on plain films, including three unstable injuries (44). CT also provided more adequate imaging on the first attempt, with only 1.4% of CT scans needing to be repeated, as opposed to 30% of plain films requiring repeat imaging due to inadequate views (45). CT reduced the time to diagnosis of injury and time to disposition from the ED. As a result of these benefits, CT scan has been deemed more cost-effective than plain films in moderate- or high-risk adult trauma patients (45). In children, the benefits of CT are less clear. CT scanning exposes children to approximately 10 –90 times more radiation than plain films (15). Children are more radiosensitive than adults, with the thyroid being particularly radiosensitive; there is a linear association between radiation dose and the incidence of thyroid cancer. Based on these data, Adelgais estimated that if CT scan replaced plain films as the primary modality to assess the cervical spine in pediatric trauma patients, an additional 18 cases of thyroid cancer would result each year (45). The increased risk of malignancy may be highest in children younger than 5 years old. Jimenez et al. determined the radiation dose from CT scan for children of different ages using anthropomorphic models (15). Utilizing data describing the increased risk of thyroid cancer in children undergoing ionizing radiation for the treatment of tinea capitis in the 1950s, they determined the relative risk of malignancy after a given radiation dose. In children ⬍ 5 years of age, the relative risk of thyroid cancer was 2.0. In contrast, for older children, the relative risk was 0.7, likely reflecting the decreased radiosensitivity of older children (15). Severely injured trauma patients also may not necessarily experience an increase in radiation with a focused CT scan of the cervical spine. These patients often receive multiple rounds of plain films in attempts to clear the cervical spine. The cumulative radiation from these multiple studies has been shown to be equivalent to that obtained with an initial C-spine CT scan in patients with a GCS score ⬍ 8 (46). CT scan also has been heralded in the adult literature as being more cost-effective than plain films and leading to shorter ED stays. It is unclear if these benefits apply to children. Unlike in adults, in children there is no statistically significant difference in the amount of time to disposition from the ED with CT scan vs. plain films; children spent 259 min in the ED for CT and 183 min for X-ray study (45). This may result from the need to sedate
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younger children to obtain a CT scan in 2004 when this study was completed. With the advent of new, faster CT scanners, the need for sedation has been reduced significantly, and as a result the time to disposition for children receiving CT scans may be shorter than estimated in this study. Regardless of these newer findings, time to disposition should not dictate the choice of study modality in children. This choice has the potential to have longterm adverse consequences both in terms of radiation exposure and potentially missed injuries, and therefore the choice should be made based on these factors rather than time to disposition. Routine CT screening does not seem to detect many injuries that are not apparent on X-ray study; CT scans of 606 patients under 5 years of age identified only 4 patients with C-spine injuries, and each of these injuries was also apparent on plain films (47). A more recent analysis in children revealed five of 23 C-spine injuries (21.7%) that were visible on CT scan but were not apparent on plain films (48). However, none of these injuries required surgical intervention, and the patient population was skewed toward sicker patients, as 30% of the injured patients were intubated with an average Injury Severity Score of 17.5. Moreover, it is unclear if these injuries were identified on CT scan by emergency physicians or pediatric radiologists. Due to these limitations, most authors recommend the use of CT scan in children only when the patient has severe injuries apparent on examination, or C-spine Xray studies are inadequate, show suspicious findings, or appear abnormal. Before obtaining a CT scan in children ⬍ 8 years of age, in whom bony injuries are less common, the radiation risks are higher, and the sensitivity of plain films better, cases can be discussed with a pediatric radiologist, traumatologist, or spine surgeon to determine the best imaging modality for clarifying the abnormalities seen on examination or X-ray study. In children 8 years of age and older, a CT scan may be more appropriate. These children have higher rates of bony injury and are better able to communicate their symptoms, thereby increasing the pretest probability of injury even when plain films are inconclusive. In addition, for children over 8 years of age, the radiation risks are reduced, and sedation is not typically required for the scan. As a result of these differences, a focused CT scan examining only the area of concern is appropriate for children over 8 years of age.
CONCLUSIONS After trauma, children are susceptible to unique injuries to the cervical spine when compared to adults. The age of a child helps predict the type of injury sustained and
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therefore can help guide imaging decisions. Children ⬍ 2 years of age rarely sustain bony fractures and are more likely to injure the spinal cord itself. As a result, X-ray studies are less helpful in this population, except after a severe mechanism of injury or when the physical examination reveals evidence of trauma to the neck or a neurologic deficit. Children between 2 and 8 years of age are more prone to bony injuries, although at rates less than older children and adults. They often cannot provide a complete history, and their physical examination findings can be subtle. Therefore, if there is a concern for potential cervical spine trauma, a more thorough evaluation is appropriate with X-ray studies, including an AP and a lateral view. Finally, in children over the age of 8 years, clinical criteria such as the NEXUS rules can be utilized to determine when imaging is needed. X-ray studies should include an AP, lateral, and odontoid view. CT scan is appropriate if X-ray studies reveal potential abnormalities or appear normal in the setting of substantial trauma or a neurologic deficit identified on physical examination. Part two of this series will discuss the role of MRI and the management of cervical spine injuries.
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149 17. Lally KP, Senac M, Hardin WD Jr, et al. Utility of the cervical spine radiograph in pediatric trauma. Am J Surg 1989;158: 540 –1. 18. Dietrich AM, Ginn-Pease ME, Bartkowski HM, et al. Pediatric cervical spine fractures: predominantly subtle presentation. J Pediatr Surg 1991;26:995–9. 19. Alexander R, and American College of Surgeons, Committee on Trauma. Advanced trauma life support for doctors, 7th edn. Chicago: American College of Surgeons; 2004. 20. Jaffe DM, Binns H, Radkowski MA, et al. Developing a clinical algorithm for early management of cervical spine injury in child trauma victims. Ann Emerg Med 1987;16:270 – 6. 21. Laham JL, Cotcamp DH, Gibbons PA, Kahana MD, Crone KR. Isolated head injuries versus multiple trauma in pediatric patients: do the same indications for cervical spine evaluation apply? Pediatr Neurosurg 1994;21:221– 6. 22. Hoffman JR, Schriger DL, Mower W, Luo JS, Zucker M: Low-risk criteria for cervical-spine radiography in blunt trauma: A prospective study. Ann Emerg Med 1992;21:1454 – 60. 23. Egloff AM, Kadom N, Vezina G, et al. Pediatric cervical spine trauma imaging: a practical approach. Pediatr Radiol 2009;39: 447–56. 24. Viccellio P, Simon H, Pressman BD, et al. A prospective multicenter study of cervical spine injury in children. Pediatrics 2001; 108:E20. 25. Anderson RC, Scaife ER, Fenton SJ, et al. Cervical spine clearance after trauma in children. J Neurosurg 2006;105(5 Suppl):361– 4. 26. Management of pediatric cervical spine and spinal cord injuries. Neurosurgery 2002;50(3 Suppl):S85–99. 27. Lee SL, Sena M, Greenholz SK, et al. A multidisciplinary approach to the development of a cervical spine clearance protocol: process, rationale, and initial results. J Pediatr Surg 2003;38:358 – 62. 28. Scarrow AM, Levy EI, Resnick DK, et al. Cervical spine evaluation in obtunded or comatose pediatric trauma patients: a pilot study. Pediatr Neurosurg 1999;30:169 –75. 29. Blahd WH Jr, Iserson KV, Bjelland JC. Efficacy of the posttraumatic cross table lateral view of the cervical spine. J Emerg Med 1985;2:243–9. 30. Shaffer MA, Doris PE. Limitation of the cross table lateral view in detecting cervical spine injuries: a retrospective analysis. Ann Emerg Med 1981;10:508 –13. 31. Jacobs LM, Schwartz R. Prospective analysis of acute cervical spine injury: a methodology to predict injury. Ann Emerg Med 1986;15:44 –9. 32. Buhs C, Cullen M, Klein M, et al. The pediatric trauma C-spine: is the ‘odontoid’ view necessary? J Pediatr Surg 2000;35:994 –7. 33. Yngve DA, Harris WP, Herndon WA, et al. Spinal cord injury without osseous spine fracture. J Pediatr Orthop 1988;8:153–9. 34. Dwek JR, Chung CB. Radiography of cervical spine injury in children: are flexion-extension radiographs useful for acute trauma? AJR Am J Roentgenol 2000;174:1617–9. 35. Eubanks JD, Gilmore A, Bess S, et al. Clearing the pediatric cervical spine following injury. J Am Acad Orthop Surg 2006;14: 552– 64. 36. Insko EK, Gracias VH, Gupta R, et al. Utility of flexion and extension radiographs of the cervical spine in the acute evaluation of blunt trauma. J Trauma 2002;53:426 –9. 37. Pollack CV Jr, Hendey GW, Martin DR, et al. Use of flexionextension radiographs of the cervical spine in blunt trauma. Ann Emerg Med 2001;38:8 –11. 38. Ralston ME, Ecklund K, Emans JB, et al. Role of oblique radiographs in blunt pediatric cervical spine injury. Pediatr Emerg Care 2003;19:68 –72. 39. Labbe JL, Leclair O, Duparc B. Traumatic atlanto-occipital dislocation with survival in children. J Pediatr Orthop B 2001; 10:319 –27. 40. Harris JH Jr. What is the minimum number of plain radiographs necessary to evaluate the cervical spine in patients who have had trauma? AJR Am J Roentgenol 1994;163:217– 8.
150 41. Pennecot GF, Gouraud D, Hardy JR, et al. Roentgenographical study of the stability of the cervical spine in children. J Pediatr Orthop 1984;4:346 –52. 42. Dormans JP. Evaluation of children with suspected cervical spine injury. J Bone Joint Surg Am 2002;84-A:124 –32. 43. Sanchez B, Waxman K, Jones T, et al. Cervical spine clearance in blunt trauma: evaluation of a computed tomography-based protocol. J Trauma 2005;59:179 – 83. 44. Berne JD, Velmahos GC, El-Tawil Q, et al. Value of complete cervical helical computed tomographic scanning in identifying cervical spine injury in the unevaluable blunt trauma patient with multiple injuries: a prospective study. J Trauma 1999;47:896–902; discussion 902–3.
J. S. Easter et al. 45. Adelgais KM, Grossman DC, Langer SG, et al. Use of helical computed tomography for imaging the pediatric cervical spine. Acad Emerg Med 2004;11:228 –36. 46. Keenan HT, Hollingshead MC, Chung CJ, et al. Using CT of the cervical spine for early evaluation of pediatric patients with head trauma. AJR Am J Roentgenol 2001;177:1405–9. 47. Hernandez JA, Chupik C, Swischuk LE. Cervical spine trauma in children under 5 years: productivity of CT. Emerg Radiol 2004; 10:176 – 8. 48. Rana AR, Drongowski R, Breckner G, Ehrlich PF. Traumatic cervical spine injuries: characteristics of missed injuries. J Pediatr Surg 2009;44:151–5.
doi:10.1016/j.jemermed.2009.11.034
Original Contributions
CERVICAL SPINE INJURIES IN CHILDREN, PART I: MECHANISM OF INJURY, CLINICAL PRESENTATION, AND IMAGING Joshua S. Easter,
MD,*
Roger Barkin,
MD,†
Carlo L. Rosen,
MD,‡
and Kevin Ban,
MD§
*Department of Emergency Medicine, Children’s Hospital of Boston, Boston, Massachusetts, †Department of Pediatrics, University of Colorado, Denver, Colorado, ‡Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, and §Pediatric Trauma Center at Meyer Hospital, Florence, Italy Reprint Address: Carlo L. Rosen, MD, Harvard Affiliated Emergency Medicine Residency, Beth Israel Deaconess Medical Center, One Deaconess Rd., West CC2, Boston, MA 02215
e Abstract—Background: Cervical spine injuries are difficult to diagnose in children. They tend to occur in different locations than in adults, and they are more difficult to identify based on history or physical examination. As a result, children are often subjected to radiographic examinations to rule out cervical spine injury. Objectives: This two-part series will review the classic cervical spine injuries encountered in children based on age and presentation. Part I will discuss the mechanisms of injury, clinical presentations, and the use of different imaging modalities, including X-ray studies and computed tomography (CT). Part II discusses management of these injuries and special considerations, including the role of magnetic resonance imaging, as well as injuries unique to children. Discussion: Although X-ray studies have relatively low risks associated with their use, they do not identify all injuries. In contrast, CT has higher sensitivity but has greater radiation, and its use is more appropriate in children over 8 years of age. Conclusion: With knowledge of cervical spine anatomy and the characteristic injuries seen at different stages of development, emergency physicians can make informed decisions about the appropriate modalities for diagnosis of pediatric cervical spine injuries. © 2011 Elsevier Inc.
INTRODUCTION Pediatric patients possess many unique problems when they injure their cervical spines. Due to their anatomy, they are prone to different types and locations of injuries than adults. These can be difficult to identify with either the history or physical examination. As a result, many children with moderate to major trauma require plain films of the cervical spine (C-spine). These also are not straightforward, as the child’s changing anatomy makes it difficult to determine which findings on imaging represent true abnormalities. Many findings require additional imaging to differentiate them further. With knowledge of the pediatric C-spine and utilization of the appropriate imaging modality for a particular complaint and mechanism, these difficulties can be overcome and emergency physicians can successfully identify cervical spine injuries in children. This is crucial because these injuries are associated with high morbidity and mortality. Cervical spine injuries require meticulous diagnostic and management strategies to reduce long-term sequelae. Approximately 72% of spinal injuries in children ⬍ 8 years of age occur in the cervical area (1). Estimates for the mortality associated with these injuries vary from 4% to 41%. As many as 67% of children have neurologic deficits, and 66% have-
e Keywords— cervical spine; trauma; imaging; pediatric injury
RECEIVED: 2 June 2009; FINAL SUBMISSION ACCEPTED: 22 November 2009
RECEIVED:
17 September 2009; 142
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concomitant head or other major organ trauma, underlining the importance of accurate and timely diagnosis (2– 4). However, the lack of specificity of clinical signs and symptoms, and the normal anatomic variants in young children make the diagnosis more difficult.
MECHANISM OF INJURY Multiple different mechanisms can lead to C-spine injuries in children. Due to greater mobility of the pediatric spine, laxity of the ligaments, shallow and angled facet joints, and underdeveloped spinous processes, children younger than 8 –10 years of age are less prone to spinal fractures than adults (5). Sixty percent of injuries occur in boys. Motor vehicle collisions, falls, sports injuries, diving, and electrical accidents are generally causative (6).
Patient Age Patient age affects the type, location, and severity of injury to the cervical spine. Although children younger than 8 years of age are less likely to sustain bony fractures, they are at higher risk for injuries to the cervical cord due to their large head size compared to their thin cervical musculature. This disproportion in head size is inversely proportional to age, leading to higher torque forces with acceleration and deceleration in younger children. Autopsies have shown that the bony spinal column in infants can withstand 2 inches of stretch without tearing, while the neurovascular structures of the cord shear with stretching beyond a quarter of an inch (7). As a result of this weakness of the cord coupled with the larger forces created by their prominent heads, younger children’s cervical injuries are often sufficient to injure the spinal cord, resulting in immediate death. Younger children who survive the initial impact of the trauma tend to have relatively minor cord injuries with few cervical spine fractures due to the greater mobility of their spines and laxity of their ligaments. In children over the age of 8 years, the bony spine is less mobile, and similar levels of force that would cause a cord injury in younger children lead only to bony injury in older children. Nearly 80% of older children develop a fracture as the primary manifestation of cervical injury instead of the isolated cord injury encountered in younger children (8). The age of the child may correlate with the location of the injury. In children younger than 8 years old, 87– 100% of injuries occur at C3 or higher in the cervical column (9,10). The fulcrum for motion in this age group is located at C2–C3, as opposed to adults, where it is found at C5–C6 (11). Although there is a propensity for
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higher cord injuries, other injuries have been identified at all levels of the spinal column in younger children, suggesting that injuries in young children are not limited to the higher cervical cord exclusively (3). Meanwhile, children over the age of 12 years have anatomy similar to adults, resulting in similar injury patterns, with relatively more injuries occurring in the lower cervical spine (12). Finally, age affects the severity of the injury. Although spinal injuries in younger children are less common, there is higher morbidity and mortality. In a review of 179 pediatric trauma cases, the incidence of neurologic deficit in children ⬍ 8 years of age was 62% compared to 47% in older children (13). This is likely attributable to the aforementioned anatomical differences in the young pediatric spine, which predispose young patients to cord damage over bony injury. Similarly, the mortality rate is higher in children. In a retrospective review of 103 consecutive C-spine injuries at a pediatric trauma center, the mortality rate was 18%, significantly higher than the approximately 10% mortality identified in adults (10). Surviving children have superior outcomes when compared to adults, likely due to their greater healing potential. As many as 90% of patients recover partially and 60% recover completely (14). This healing potential is seen in both younger and older children.
Direction of Force As in adults, the direction of the force applied during the accident influences the nature and location of the resulting fracture and its subsequent stability in children (Table 1).
CLINICAL PRESENTATION Patients with spinal injuries should undergo neurologic examinations including motor, sensory, and reflex exam-
Table 1. Cervical Spine Fractures based on Mechanism
Mechanism Hyperflexion
Hyperextension
Axial Load
Injury Flexion teardrop Bilateral facet dislocation Unilateral facet dislocation Anterior subluxation Wedge fracture Spinous process fracture Hyperextension dislocation Extension teardrop Hangman’s fracture (pedicles C2) Burst fracture Jefferson (C1)
Stability (U ⫽ Unstable, S ⫽ Stable) U U S U/S U S U U U U U
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inations, as well as a thorough examination for associated injuries. Nearly one-third to one-half of all children with cervical cord injuries demonstrate neurologic deficits (15,16). Furthermore, 40% of spinal cord injuries are associated with head trauma, necessitating a complete cranial examination. Attention should be paid to the patient’s breathing and circulation because injuries to the cord at C3–C5 can result in phrenic nerve failure with subsequent hypoventilation or apnea. Similarly, spinal shock can affect the cardiovascular system, leading to hypotension or bradycardia. Any of these findings are ominous and can provide indirect evidence of a cervical spine injury when no other direct signs or symptoms of spinal trauma are present. Finally, no one particular symptom or sign provides both adequate sensitivity and specificity on physical examination to exclude a cervical spine injury.
IMAGING Due to the difficulty in detecting cervical spine injuries based on history and physical examination in pediatric trauma patients, imaging is frequently necessary. There is no consensus for when further evaluation with imaging is appropriate to diagnose a pediatric spinal cord injury. Lally et al. showed that routine plain films in all pediatric trauma patients have a low yield; only 1 in 187 patients possessed a fracture on routine X-ray study (17). However, failure to perform radiographic imaging on patients deemed injury free based on history and physical examination alone can result in delayed diagnosis of a fracture. Dietrich et al. classified 86% of delayed diagnoses of spinal injuries as a result of clinical misinterpretation of the original injury as “trivial” and subsequent failure to evaluate the patient with imaging sufficiently (18). This suggests that routine plain films may be necessary to avoid missing such fractures. The American College of Surgeons supports this contention, advocating plain films of the cervical spine as a part of the initial major trauma evaluation in all children (19). There is no consensus about when imaging should be obtained in pediatric patients.
Guidelines for Imaging Several studies have attempted to determine the appropriate clinical scenario for imaging the pediatric C-spine by identifying factors that place children at high risk for cervical spine injury. The first retrospective review of C-spine imaging in children assessed 206 trauma patients under the age of 16 years in whom C-spine plain films were obtained. The presence of neck pain, neck tender-
ness, limitation of mobility, a history of direct trauma to the neck, or abnormal neurologic examination identified 98% of C-spine injuries with a specificity of 54%. By imaging only patients with these signs or symptoms, 58 of 59 C-spine injuries were identified, and plain film utilization could have been reduced by 38%. The only missed injury involved damage to the cord but no bony injury (20). However, in this review, only 5% of patients underwent computed tomography (CT) scan or magnetic resonance imaging (MRI), and as a result, several injuries may have been missed that would have been visible with these modalities. Laham et al. expanded on this review by attempting to identify criteria that would be 100% sensitive for spinal injury in their retrospective analysis of 268 children (21). When children could communicate about their symptoms (i.e., they were over the age of 2 years) and did not have a debilitating head injury, the presence of neck pain was 100% sensitive for cervical injury. However, in their analysis, only 80% of patients received plain films and therefore, they may have missed fractures occurring in patients without neck pain. These retrospective reviews of C-spine injury do not provide sufficient evidence to create definitive guidelines for imaging in the emergency department (ED). Emergency physicians utilize the NEXUS criteria in adult patients to determine the need for C-spine imaging, and many practitioners extrapolate guidelines from the NEXUS criteria and apply them to children (22). The NEXUS analysis showed that imaging was unnecessary if patients had no midline cervical tenderness, no focal neurologic deficits, normal alertness, no intoxication, and no painful distracting injury. These criteria had a sensitivity of 99% for adult cervical spine injury (95% confidence interval [CI] 98 –99.6%). However, caution must be exercised in applying these guidelines to children. A retrospective review of 447 patients younger than 19 years of age found a sensitivity of 100% for the NEXUS criteria (23). In a multicenter trial of 3065 pediatric patients, Viccellio et al. considered children possessing any of the NEXUS criteria as high risk, whereas those without any of the criteria were deemed low risk (24). Of the 603 low-risk patients, none had a C-spine injury on three-view plain films. Thirty children had a C-spine injury, and each of these had at least one of the NEXUS criteria; the NEXUS criteria had a sensitivity of 100% (95% CI 88 –100%) and specificity of nearly 20%. Utilization of the NEXUS criteria would have reduced imaging by approximately 20% (24). In addition, adoption of the NEXUS rules by ED staff in one study reduced the need for surgical consult by 60%, without any increase in missed injuries (25). Despite this apparent confirmation of the validity of the NEXUS criteria for children in the ED, several limitations exist, particularly in younger patients. Viccel-
Cervical Spine Injuries in Children, Part I
lio’s confirmation of the NEXUS criteria in children included only 4 patients with C-spine injuries who were ⬍ 9 years of age and no patients ⬍ 2 years of age (24). This low number of injuries in the younger age groups is not an accurate reflection of the pathophysiology of cervical spine injuries. Younger children have a higher risk of spinal cord injury than older patients. In addition, being incapable of verbal communication renders them significantly more prone to having an undiagnosed neck injury. The low number of spinal cord injuries in younger children observed in Viccellio’s analysis likely arose because only a small number of younger children were enrolled; only 2.8% of patients in the study were ⬍ 2 years of age (24). Furthermore, the 95% CI cited by Viccellio, indicating the sensitivity of the NEXUS criteria, could be as low as 88% in children. This sensitivity is significantly lower than the 99% lower end of the confidence interval identified in adults with the NEXUS criteria and would result in a substantial number of potentially devastating missed injuries. There is still no consensus by professional organizations on the appropriate variables to include when making a decision about imaging the cervical spine in children. The American Association of Neurological Surgeons (AANS) recommends application of the NEXUS criteria in children over 9 years of age; in children who are alert, who have no neurologic deficit, midline C-spine tenderness, painful distracting injury, or intoxication, imaging is not required (26). Meanwhile, Lee et al. attempted to create consensus guidelines incorporating the various strategies employed in different disciplines (27). To increase the sensitivity of detecting injuries in children, they suggested expanding the criteria and imaging the C-spine whenever the NEXUS criteria were present or there was significant mechanism of injury, a history of transient neurologic symptoms or physical evidence of neck trauma, significant trauma to the head or face, or the child was inconsolable (27). Other authors suggest imaging the spine whenever the patient has a Glasgow Coma Scale (GCS) score of ⬍ 14 (28). Clearly, there is no consensus on the appropriate criteria for determining when children require C-spine imaging in the ED. However, it seems appropriate to apply the NEXUS criteria in children aged 9 years and older. For younger children, any concerning clinical history, signs, or symptoms in addition to the presence of any of the NEXUS criteria should lead to imaging with plain films.
Types of Plain Films There is also disagreement about the type of X-ray studies that should be obtained once the provider elects to image the cervical spine. The cross-table lateral identifies
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as many as 98% of cervical spine fractures, dislocations, or subluxations in children (18). However, several studies have found lower sensitivities when it is employed in isolation; it may miss as many as 20 –25% of fractures (20,29 –31). Therefore, providers typically acquire the anteroposterior (AP) view of the cervical spine to complete the cross-table lateral study. This view can identify lateral mass fractures and transverse process fractures not seen on the lateral film. When used in combination with the lateral view, sensitivity has been shown to increase to 87% in children ⬍ 8 years of age (32). Most trauma centers also obtain odontoid or openmouth views in cooperative patients, although the need for these views is more controversial. A multicenter retrospective review identified one case out of 51 Cspine injuries where the odontoid view provided the crucial view for diagnosing the injury. In children ⬍ 9 years old, the odontoid view did not provide any additional benefit. The authors concluded that in children ⬍ 9 years of age, the open-mouth view was unnecessary (32). Similarly, a survey of 432 pediatric radiologists revealed that only 46 fractures were seen on only the odontoid view in children ⬍ 5 years of age. The resulting low missed fracture rate (0.007 per year per radiologist) was interpreted by the authors as suggesting that the odontoid view should not be routinely acquired in children ⬍ 5 years old (32). Most fractures of the odontoid in younger children occur at the dens-body synchondrosis, the weakest area of C2, and these are typically apparent on a lateral X-ray study (32). Further complicating this issue is the difficulty in obtaining compliance for open-mouth views in young children. As a result of these factors, the AANS and the Congress of Neurological Surgeons recommend only AP and lateral X-ray studies in children ⬍ 9 years of age (26). Each of the aforementioned studies of the odontoid view had limitations. The first analysis included only 51 patients with actual C-spine injuries. The second study involved only radiologists, not emergency physicians, and suffered from weaknesses from its retrospective design as well as recall bias. Other reviews have shown that the odontoid view, combined with the AP and lateral views, increases sensitivity for C-spine injury to 94% (33). Further research is needed before definitively stating that the odontoid view is truly unnecessary, particularly in older children. In contrast to the odontoid view, flexion, extension, and oblique views are more widely accepted as having a minimal role in the initial ED assessment of C-spine injuries. Flexion and extension views are intended to demonstrate cervical instability, atlantoaxial joint instability, and ligamentous injury. The AANS recommends this approach (26). However, a review of 224 pediatric cases did not reveal any cases where flexion-extension
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X-ray studies aided in diagnosis in the ED (34). Also, false negatives can be obtained in children when they are frightened, in pain, or guarding their necks (12). False positives may arise from vertebral angulation seen on flexion views secondary to normal variation in ligament laxity (35). These views also require additional resources because at most institutions, physicians must passively flex and extend the patient’s neck for these films to prevent possible spinal cord damage from movement of the cervical spine. Moreover, nearly 30% of patients cannot adequately flex or extend the neck to provide these views (36). As a result of these complications, flexion and extension views should be utilized only 7 to 28 days after the injury (37). Oblique views are occasionally obtained to look at the pedicles, posterior lamina, and articular masses. These views are typically employed in adults and children when the AP, lateral, and odontoid views are normal but the patient has persistent pain. Ralston et al. demonstrated that oblique views are of little utility in children (38). Their retrospective review of 109 children showed no abnormalities on oblique views when the AP and lateral views were normal. For one patient with equivocal AP and lateral views, the oblique view demonstrated subluxation.
Interpretation of Plain Films When reading a cervical spine plain film series, a systematic process helps to identify injuries. A thorough analysis of the C-spine requires measurement of several intervals in the upper cervical spine because both atlantoaxial and atlantooccipital instability is much more common in children than in adults. To assess atlantoaxial stability (Table 2), several measurements should be made: 1) The Wackenheim’s clivus line is drawn along the posterior aspect of the clivus and should intersect the odontoid or be tangential to it (Figure 1). If this does not
Table 2. Measures of Atlantoaxial Instability in Children on Cervical Spine Plain Films Measures
Normal Findings (Distances Except Where Specified)
Wackenheim’s clivus Line along posterior edge of clivus line should intersect odontoid Power’s ratio Ratio of tip of basion to anterior atlas to opisthion to posterior atlas ⬍ 1 Harris criteria Basion and odontoid ⬍ 12 mm Atlantodens interval Posterior atlas to anterior dens ⬍ 5 mm Rule of thirds Spinal canal: 1/3 dens, 1/3 cord, 1/3 empty
Figure 1. Wackenheim’s Clivus Line—line drawn along the posterior portion of the clivus intersects the odontoid, making atlantoaxial instability less likely.
intersect or run perpendicular to the odontoid, it suggests atlantoaxial instability. 2) The Powers ratio measures the distance from the tip of the basion (anterior margin of the skull’s greater foramen) to the posterior arch of the atlas, and divides this value by the distance from the opisthion (posterior margin of the greater foramen) to the posterior aspect of the anterior arch of the atlas. If this ratio is ⬎ 1, it suggests an anterior atlantoaxial dislocation (Figure 2). However, a ratio ⬍ 1 does not rule out a posterior or longitudinal dislocation (39). 3) The rule of 12, or Harris criteria, are the criteria most easily employed in the ED. The distance between the basion and the rostral tip of the odontoid and the distance between the basion and the rostral position of the posterior cortical margin of the axis should both be ⬍ 12 mm (Figure 3). This rule is not always valid in children ⬍ 13 years of age (40). Moreover, each one of these criteria is limited by difficulty in identifying the requisite bony landmarks on plain films. The atlantodens interval and the rule of thirds are more readily measured in the ED (Table 2). The atlantodens interval, measuring the distance between the posterior cortex of the anterior arch of the atlas to the anterior cortex of the dens, should be ⬍ 5 mm (Figure 4). An interval larger than this indicates atlantoaxial instability (41). A more clinically relevant rule in the ED for atlantoaxial instability is the rule of thirds: the dens should fill one-third of the spinal canal space, the spinal cord one-third of the space, and the final third should be free. If this free space is reduced in size, it suggests atlantoaxial instability (35). The soft tissue distances also
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A B
A
B
Figure 2. Powers ratio—the ratio of the distance from the basion to the spinolaminar line of the atlas (line labeled A) to the distance between the anterior tubercle of the atlas and opisthion (posterior edge of the foramen magnum) (line labeled B) should be less than one.
Figure 4. Atlantodens interval—the distance between the anterior arch of the atlas (line labeled A) and anterior portion of the dens (line labeled B) should be < 5 mm.
Computed Tomography should be measured. The retropharyngeal space should be ⬍ 7 mm and the retrotracheal space ⬍ 14 mm (42). Soft tissue swelling greater than these values suggests the presence of an underlying fracture (Figure 5).
In the 21st century, many trauma centers are routinely utilizing CT instead of plain films to assess the cervical spine. A protocol of obtaining a CT scan in all adult
B A
Figure 3. Harris Criteria—the distance between a line drawn along the posterior cortex of the body of C2 and the rostral portion of the odontoid (line labeled A) should be within 12 mm (line labeled B) of the basion.
Figure 5. Swelling of the retropharyngeal space—the retropharyngeal space measures approximately 10 mm at C2, indicative of an underlying fracture, which is apparent in the lamina of C2.
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patients, coupled with an MRI study in patients presenting with neurologic deficits, had a sensitivity of 99% and specificity of 100% for cervical injuries. Only one of 100 cervical injuries was missed, and this missed injury occurred in a patient with a preexisting syringomyelia (43). When compared with plain films, CT scan identified eight of 20 C-spine injuries that were not visible on plain films, including three unstable injuries (44). CT also provided more adequate imaging on the first attempt, with only 1.4% of CT scans needing to be repeated, as opposed to 30% of plain films requiring repeat imaging due to inadequate views (45). CT reduced the time to diagnosis of injury and time to disposition from the ED. As a result of these benefits, CT scan has been deemed more cost-effective than plain films in moderate- or high-risk adult trauma patients (45). In children, the benefits of CT are less clear. CT scanning exposes children to approximately 10 –90 times more radiation than plain films (15). Children are more radiosensitive than adults, with the thyroid being particularly radiosensitive; there is a linear association between radiation dose and the incidence of thyroid cancer. Based on these data, Adelgais estimated that if CT scan replaced plain films as the primary modality to assess the cervical spine in pediatric trauma patients, an additional 18 cases of thyroid cancer would result each year (45). The increased risk of malignancy may be highest in children younger than 5 years old. Jimenez et al. determined the radiation dose from CT scan for children of different ages using anthropomorphic models (15). Utilizing data describing the increased risk of thyroid cancer in children undergoing ionizing radiation for the treatment of tinea capitis in the 1950s, they determined the relative risk of malignancy after a given radiation dose. In children ⬍ 5 years of age, the relative risk of thyroid cancer was 2.0. In contrast, for older children, the relative risk was 0.7, likely reflecting the decreased radiosensitivity of older children (15). Severely injured trauma patients also may not necessarily experience an increase in radiation with a focused CT scan of the cervical spine. These patients often receive multiple rounds of plain films in attempts to clear the cervical spine. The cumulative radiation from these multiple studies has been shown to be equivalent to that obtained with an initial C-spine CT scan in patients with a GCS score ⬍ 8 (46). CT scan also has been heralded in the adult literature as being more cost-effective than plain films and leading to shorter ED stays. It is unclear if these benefits apply to children. Unlike in adults, in children there is no statistically significant difference in the amount of time to disposition from the ED with CT scan vs. plain films; children spent 259 min in the ED for CT and 183 min for X-ray study (45). This may result from the need to sedate
J. S. Easter et al.
younger children to obtain a CT scan in 2004 when this study was completed. With the advent of new, faster CT scanners, the need for sedation has been reduced significantly, and as a result the time to disposition for children receiving CT scans may be shorter than estimated in this study. Regardless of these newer findings, time to disposition should not dictate the choice of study modality in children. This choice has the potential to have longterm adverse consequences both in terms of radiation exposure and potentially missed injuries, and therefore the choice should be made based on these factors rather than time to disposition. Routine CT screening does not seem to detect many injuries that are not apparent on X-ray study; CT scans of 606 patients under 5 years of age identified only 4 patients with C-spine injuries, and each of these injuries was also apparent on plain films (47). A more recent analysis in children revealed five of 23 C-spine injuries (21.7%) that were visible on CT scan but were not apparent on plain films (48). However, none of these injuries required surgical intervention, and the patient population was skewed toward sicker patients, as 30% of the injured patients were intubated with an average Injury Severity Score of 17.5. Moreover, it is unclear if these injuries were identified on CT scan by emergency physicians or pediatric radiologists. Due to these limitations, most authors recommend the use of CT scan in children only when the patient has severe injuries apparent on examination, or C-spine Xray studies are inadequate, show suspicious findings, or appear abnormal. Before obtaining a CT scan in children ⬍ 8 years of age, in whom bony injuries are less common, the radiation risks are higher, and the sensitivity of plain films better, cases can be discussed with a pediatric radiologist, traumatologist, or spine surgeon to determine the best imaging modality for clarifying the abnormalities seen on examination or X-ray study. In children 8 years of age and older, a CT scan may be more appropriate. These children have higher rates of bony injury and are better able to communicate their symptoms, thereby increasing the pretest probability of injury even when plain films are inconclusive. In addition, for children over 8 years of age, the radiation risks are reduced, and sedation is not typically required for the scan. As a result of these differences, a focused CT scan examining only the area of concern is appropriate for children over 8 years of age.
CONCLUSIONS After trauma, children are susceptible to unique injuries to the cervical spine when compared to adults. The age of a child helps predict the type of injury sustained and
Cervical Spine Injuries in Children, Part I
therefore can help guide imaging decisions. Children ⬍ 2 years of age rarely sustain bony fractures and are more likely to injure the spinal cord itself. As a result, X-ray studies are less helpful in this population, except after a severe mechanism of injury or when the physical examination reveals evidence of trauma to the neck or a neurologic deficit. Children between 2 and 8 years of age are more prone to bony injuries, although at rates less than older children and adults. They often cannot provide a complete history, and their physical examination findings can be subtle. Therefore, if there is a concern for potential cervical spine trauma, a more thorough evaluation is appropriate with X-ray studies, including an AP and a lateral view. Finally, in children over the age of 8 years, clinical criteria such as the NEXUS rules can be utilized to determine when imaging is needed. X-ray studies should include an AP, lateral, and odontoid view. CT scan is appropriate if X-ray studies reveal potential abnormalities or appear normal in the setting of substantial trauma or a neurologic deficit identified on physical examination. Part two of this series will discuss the role of MRI and the management of cervical spine injuries.
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