The paediatric plain cervical-spine film - got it cracked?

Transcription

1 The paediatric plain cervical-spine film - got it cracked? Poster No.: C-1690 Congress: ECR 2014 Type: Educational Exhibit Authors: J. B. Davies, K. Khanna, S. G. Cross; London/UK Keywords: Anatomy, Emergency, Musculoskeletal spine, Conventional radiography, Normal variants, Physiological studies, Congenital, Trauma DOI: /ecr2014/C-1690 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 27

2 Learning objectives To understand guidelines relating to imaging of Paediatric C-Spine in trauma To recognize signs of fracture of Paediatric C-Spine To understand the differences between normal paediatric and adult C-Spine Page 2 of 27

3 Background C-spine injury in children under the age of 10 years is a rare consequence of trauma, occurring in less than 2% of cases [1] however it is associated with a significant morbidity and mortality [2]. The anatomy of the paediatric c-spine differs from that of the adult and as a result, upper c-spine injuries predominate in children. Below 8 years of age the head to body ratio is relatively larger causing greater inertial forces in trauma. Joints are more flexible due to lax ligaments and less developed musculature [3]. Vertebrae are less stable due to incomplete ossification, incomplete spinous process development, wedge shaped vertebral bodies and more horizontal facet joints [4]. As a result more movement is possible and greater forces may be transferred through upper cervical vertebrae, corresponding to the most common location of injury [5]. By the age of 10 to 12 years of age the cervical spine has matured and reaches adult proportions [6] and after the age of 12 the sequalae of cervical spine trauma are similar to the adult population [7] Excluding important C-Spine injuries in trauma is essential to avoid serious neurological deficit [8]. History and examination often accompanied by imaging is required to minimize risk of missing significant injuries however, obtaining an accurate history and eliciting reliable neurological signs in young or unconscious children can be difficult. Evidence based methods for clearing the c-spine in adults are established [9] but insufficient data exists to create robust protocols for children and so adult guidelines have been adapted [10]. There is now a dedicated consensus guideline for clearing the paediatric c-spine which draws on all available evidence [11]. Diagnostic imaging modalities range from plane x-ray films and dynamic fluoroscopic images to CT and MRI. Exposure to ionizing radiation is however a major consideration in assessing for c-spine injuries in young patients due to the sensitivity of the paediatric thyroid. CT is becoming more commonly used however has been shown to significantly increase the risk of developing thyroid malignancy [12,13]. Page 3 of 27

4 Findings and procedure details Current Guidelines: Current consensus relies on a combination of the National Emergency X-Radiography Utilization Study (NEXUS) [14] and Canadian C-Spine guidelines [11]. The Nexus LowRisk Criteria are a tool used to aid in the exclusion of a significant c-spine injury and have been validated for use in the paediatric population [10]. The criteria draw on data from 34,069 patients evaluated by imaging of the c-spine following blunt trauma. 851 patients were less than 8 years of age, 11 of whom had a significant cervical spine injury. The NEXUS criteria were found to be highly sensitive (99%) for excluding injury and of those with c-spine injury not selected by any of the NEXUS criteria (n =8), none were younger than 10 years of age [15]. The NEXUS Low-Risk Criteria [14] Cervical-Spine radiography is indicated for patients with trauma unless they meet all of the following criteria: No posterior midline cervical-spine tenderness No evidence of intoxication A normal Level of alertness No focal neurological deficit No painful distracting injuries If a child presents with an injury and fulfills at least one of the NEXUS Low-Risk criteria then imaging is required however the appropriate imaging modality is not mentioned. The Trauma Association of Canada Paediatric Committee (Figure 1 & 2)has produced two consensus guidelines based on all available evidence to aid clinicians and radiologists recommend appropriate diagnostic management of these patients [11]. Although widely accepted, several bodies such as the UK's National Institute for Clinical Excellence (NICE) have subsequently produced their own recommendations [16] based on both NEXUS and the Canadian Paediatric Committee guidelines (Figure 1 & 2). NICE recommend that 2 views (AP and lateral) of the paediatric (less than 10 years of age) c-spine are sufficient to exclude injury, except where GCS < 9, when CT should be performed. Paediatric C-Spine Radiographs: Page 4 of 27

5 The accurate interpretation of the paediatric cervical spine radiograph is important to avoid the need for further imaging with CT. Odontoid views are not routinely obtained in blunt trauma due to the difficulty in obtaining adequate images due to a short neck and the difficulty in following commands. The odontoid view has also been shown not to improve the sensitivity to injury [17]. Of the views commonly acquired the lateral image is the most sensitive for detecting injury [18]. Combined, the AP and Lateral views are 87% sensitive to c-spine injury in children under 9 years of age [19]. In the acute setting, flexion and extension images are contraindicated as a result of the risk of causing a cord injury although they are also of limited value in the acute setting due to the limited range of movement resulting from muscle spasm and pain [20]. To ensure high quality images, care should be taken to ensure that the patient is adequately aligned prior to x-ray. There should be superimposition of the external auditory meati and lower cervical facets (Figure 3) Differences Between Adult and Paediatric C-Spine: Adequate film quality and alignment is crucial to maximize the sensitivity and specificity of the imaging test for the detection of traumatic injury (Figure 3). External Meati Should be aligned (arrow) and the cervical spine should be visualized from the skull base to the superior aspect of the T1 thoracic vertebrae. Anterior spinal line (black), posterior spinal line (red) and spinolaminar line (blue) are also shown. Pseudosubluxation, or anterior displacement of the C2 vertebral body relative to C3, or less commonly C3 on C4 is a common physiological appearance. It may be so profound as to resemble injury (Figures 4, 5, 6). Figure 4 is a lateral cervical radiograph demonstrating anterior pseudosubluxation of C2 on C3. Both the anterior and posterior spinal lines (Figure 4 Black and red lines respectively) are disrupted however the spinolaminar line (Figure 4, blue line) and C2 lines (Figure 5, Black line) are intact indicating pseudosubluxation, a normal variant. The C2 line runs tangential to the posterior cortex of the dens which should contact, not transect the body of C3 [17]. Another measure is the posterior cervical line (Figure 6, blue line), which is a straight line drawn between the anterior aspect of the spinous process' of C1 and C3. The anterior aspect of the spinous process of C2 should lie no further than 1mm from this line. A distance greater than 1mm represents true injury [21]. A distance greater than 2mm often indicates a bilateral pars interarticularis or "hangman fracture" of C2 [22]. Loss of cervical lordosis (Figure 7) is a common anatomical variant which may be present in the neutral position up to the age of 16 [23]. Ligamentous integrity may be assessed by measuring the interspinous distances which should not be greater than 1.5 times that of their superior or inferior neighbors. However, in flexion the distance between the C1 and Page 5 of 27

6 C2 spinous process' can increase markedly due to the strong ligamentous attachment of C1 to the skull base [24]. Figure 8,9 demonstrate the variation in pre vertebral soft tissue in patients with no spinal injuries. Significant ligamentous injury may occur without increased pre vertebral soft tissue thickness and normal thickness of retropharyngeal tissue also changes with age and is affected by phase of respiration in infants. Hypertrophied soft retropharyngral tissue should however measure less than half of the AP diameter of the vertebral body at the C2 -C3 level [25], or less than 6mm [26]. When lateral c-spine radiographs demonstrate widened pre cervical soft tissue in children with suspected traumatic injury repeat radiography should be repeated in inspiration to determine if the abnormality is real. Paediatric C-Spine Injuries: SCIWORA Spinal Cord Injury With-Out Radiographic Abnormality (SCIWORA) is defined by a spinal cord injury in the absence of any radiologically identifiable injury. The mechanism is thought to be secondary to severe transient ligamentous deformation resulting in trauma to the less elastic spinal cord or cord bold supply. When clinical signs suggestive of cord injury are present MRI should be performed to assess for SCIWORA. Occiput - C1 injury: Cranio cervical injuries are often fatal and may be caused by sudden deceleration such as those seen in vehicle crashes. Although rare, these injuries are 2.5 time more common in children due to their small occipital condyles and horizontally orientated atlanto occipital joints. The Wachenheim clivus line may be used to assess the craniocervical junction on lateral cervical spine plane film (Figure 10). An injury is suspected when the line does not intersect or is tangential to the odontoid process. The Powers ratio (Figure 11) is derived from the ratio of the distances from the basion to the posterior arch of C1 divided by the anterior arch of C1 to the opsithion (lip of the foramen magnum). In health, the ratio should be less than 1 (Figure 11) and the normal basion dens interval and basion axis interval should both be less than 12mm (Figure 12 & Figure 13). Injuries to the cranio cervical junction are usually associated with significant pre vertebral soft tissue swelling and significant neurological defecit. The basion axis interval (Figure 13) is demonstrated by the distance (red line) between the basion and a line drawn along the posterior aspect of the dens (black line). Normal is Page 6 of 27

7 between 12mm anterior and 4mm posterior [25]. Abnormality of this measurement may signify craniocervical junction pathology. C1 Fractures Fractures of the C1 vertebra may be caused by axial loading through the spine causing the lateral masses of C1 to impact upon the C2 vertebral body potentially disrupting the C1 ring. Fractures usually occur through the anterior or posterior arches and are known as Jefferson fractures. These injuries may manifest as increased distance between the lateral masses and odontoid process on an open mouth view (Figure 14) A distance of greater than 6mm is indicative of ligamentous disruption. Atlantoaxial injuries Atlantoaxial rotatory subluxation is a cause of torticollis and may occur as a result of congenital abnormalities or secondary to trauma. The anterior facet of C1 subluxes and may become fixed anterior to the C2 facet. In more severe cases there may be coexistent C1-C2 dislocation which results in increased pre dental space (Figure 15, 16) and loss of definition at the craniocervical junction Ligamentous disruption of the atlantoaxial joint. Anterior displacement of C1 on C2 with disruption of the transverse ligament is rare as an isolated injury but may occur as part of a constellation of findings associated with developmental bone dysplasias and syndromes such as Klippel-Feil syndrome. Odontoid fractures: Usually occur through the cartilaginous synchondrosis and results in anterior displacement of the odontoid with posterior tilt of the dens. Page 7 of 27

8 Images for this section: Fig. 1: The Trauma Association of Canada Paediatric Committee Guidelines Chung S, Mikrogianakis A, Wales P. Trauma association of Canada Paediatric Subcommittee National Paediatric C-Spine Evaluation Pathway: Consensus Guidelines. J Traum Ac Care Surg 2011; 70: Page 8 of 27

9 Fig. 2: The Trauma Association of Canada Paediatric Committee Guidelines Chung S, Mikrogianakis A, Wales P. Trauma association of Canada Paediatric Subcommittee National Paediatric C-Spine Evaluation Pathway: Consensus Guidelines. J Traum Ac Care Surg 2011; 70: Page 9 of 27

10 Fig. 3: Normal Cervical Alignment. External Meati Should be aligned (arrow) and the cervical spine should be visualized from the skull base to the superior aspect of the T1 thoracic vertebrae. Anterior spinal line (black), posterior spinal line (red) and spinolaminar line (blue) are also shown. Page 10 of 27

11 Fig. 4: Pseudosubluxation Page 11 of 27

12 Fig. 5: Pseudosubluxation, C2 line (Purple) Page 12 of 27

13 Fig. 6: Pseudosubluxation. Posterior cervical line (Blue) Page 13 of 27

14 Fig. 7: Loss of cervical lordosis Page 14 of 27

15 Fig. 8: Pre vertebral soft tissue Page 15 of 27

16 Fig. 9: Widened Pre Vertebral Soft Tissues Page 16 of 27

17 Fig. 10: Wackenheim line (Black) runs down the posterior aspect of the clivus and in normal radiographs will transect the posterior 1/3 of the dens [17] Page 17 of 27

18 Fig. 11: Powers ratio: The distance from the basion to the posterior arch of C1 (black line) divided by the distance from the opsithion to the anterior arch of C1 (red line). In normal subjects the powers ratio is less than 1 [17]. A Powers ratio greater than one indicates occipitocervical instability Page 18 of 27

19 Fig. 12: The normal basion dens interval (black line) (normal is <12 mm) and C1 -C2 intraspinous distance (red line)(normal is <12mm) [25] Page 19 of 27

20 Fig. 13: Basion axis interval is demonstrated by the distance (red line) between the basion and a line drawn along the posterior aspect of the dens (black line). Page 20 of 27

21 Fig. 14: Open mouth or "Peg" view Page 21 of 27

22 Fig. 15: Pre dental distance measurement.the normal pre dental distance (black line) decreases with increasing age. Less than 5 mm is acceptable below 8 years of age and less than 3mm is acceptable above 8 years of age [27] Page 22 of 27

23 Fig. 16: Pre dental distance measurement.the normal pre dental distance (black line) decreases with increasing age. Less than 5 mm is acceptable below 8 years of age and less than 3mm is acceptable above 8 years of age [27] Page 23 of 27

24 Conclusion Paediatric cervical spine injuries are rare. Cervical spine trauma in young patients causes diagnostic problems because of the sensitivity of the developing thyroid to ionizing radiation and a relative lack of data relating to the sensitivity of radiological investigations to paediatric cervical spine injury. Recent guidelines advising appropriate imaging pathways in paediatric blunt c-spine trauma have recently been published to aid decision making and should be familiar to those involved with these cases. The anatomical and physiological differences between adult and paediatric cervical spine result in different injury patterns to which all radiologists must be familiar. Presented in this poster are key points which are useful when interpreting paediatric cervical plain radiographs. Page 24 of 27

25 Personal information J. Davies, Department of Radiology, St Bartholomew's & Royal London Hospitals, London. K. Khanna, Department of Radiology, St Bartholomew's & Royal London Hospitals, London. S Cross, Department of Radiology, St Bartholomew's & Royal London Hospitals, London. Page 25 of 27

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27 18. Silva CT, Doria AS, Traubici J. Do additional views improve the diagnostic performance of cervical spine radiography in pediatric trauma? AJR 2010; 194: Buhs C, Klein M, Farmer D. The pediatric trauma c-spine: is the "odontoid" view necessary? J Pediatr Surg 2000; 35: Ralston ME, Chung K, Barnes PD, Emans JB, Schutzman SA. Role of flexion-extension radiographs in blunt pediatric cervical spine injury. Acad Emerg Med 2001; 8: Swischuk LE. Emergency imaging of the acutely ill or injured child. In: The spine and the spinal cord. 4th ed. Philadelphia, Pa: Lippincott Williams & Wilkins, 2000; Lustrin E, Karakas SP, Ortiz AO. Pediatric Cervical Spine: Normal Anatomy, Variants, and Trauma. RadioGraphics 2003; 23: Hall DE, Boydston W. Pediatric neck injuries. Pediatr Rev 1999; 20: Bonadio WA. Cervical spine trauma in children. I. General concepts, normal anatomy, radiographic evaluation. Am J Emerg Med 1993; 11: Egloff AM, Kadom N, Vezina G, Bulas D. Pediatric cervical spine trauma imaging: a practical approach. Pediatr Radiol 2009; 39: Warner WC. Rockwood and Wilkins' fractures in children. In: Beaty JH, Kasser JR, eds. Cervical spine injuries in children. Lippincott Williams & Wilkins 2001; Roche C, Carty H. Spinal trauma in children. Pediatr Radiol 2001; 31: Page 27 of 27