1. The Subaxial Injury Classification Scoring System (SLIC): What the Neuroradiologist Needs to Know Kyle M. Moulton MD FRCPC Jason Chew MbChB FRCPC FRANZCR Jason R. Shewchuk MD FRCPC University of British Columbia, Vancouver, BC, Canada ASNR 2016 Electronic Exhibit Submission

2. Instructions The presentation contains hyperlinks, denoted by text boxes, which will appear as follows: Click on these boxes for further information, relevant case examples, or to navigate to the specific section indicated Alternatively, you can proceed through the slideshow in conventional fashion by using the arrow keys At any time, click on the ‘UBC’ icon located in the upper left hand side, and you will be directed to the presentation overview from where you can quickly access any given component of the SLIC scoring system: Morphology of Injury

3. Objectives In viewing this presentation, the attendee will enhance his or her understanding of: Clinical features of subaxial cervical spine injury What constitutes the subaxial injury classification scoring system (SLIC) How SLIC is used in the management of patients with subaxial cervical spine injuries Imaging findings pertinent to SLIC scoring Evidence supporting the use of SLIC

4. Subaxial Cervical Spine Injuries The subaxial cervical spine – defined as caudal to C2 – accounts for majority of cervical spine fractures (65%) and dislocations (>75%) These injuries have highly variable clinical severity and outcome Require accurate classification to minimize morbidity and mortality Management is a common dilemma for orthopaedic surgeons and neurosurgeons, who must decide: 1.Whether the patient will benefit from surgery 2.And if so, the optimal approach and timing of surgery Vacarro AR et al. Spine 2007; 32 (21): 2365-2374

5. What is SLIC? SLIC is a comprehensive classification system for subaxial cervical trauma Addresses the question of whether the patient will benefit from surgery Incorporates information about injury pattern, severity, treatment considerations, and prognosis into a unifying scoring system to guide management SLIC score is based on the assessment of 3 domains, which are considered independent predictors of clinical outcome: Vacarro AR et al. Spine 2007; 32 (21): 2365-2374 Morphology of Injury Disco-ligamentous Integrity Neurologic Status (Click on links for further information)

6. Morphology of Injury

7. Based on radiographic, CT or MRI assessment Divided into 3 patterns, based on relation of anterior supporting structures: Compression (1 or 2 points) Distraction (3 points) Translation/rotation (4 points) Increasing clinical severity Increasing SLIC score (Click on links for further information)

8. Definition: loss of vertebral body height or endplate destruction Least clinically-severe pattern 1 point toward SLIC score + 1 point if burst component present Non-displaced or minimally-displaced posterior element fractures may be present Defined as: < 3.5 mm displacement or 11 degrees rotation Morphology of Injury Compression ** Displaced posterior element fractures are considered translation/rotation pattern!**

9. ‘Compression’ pattern includes the following sub-types: Compression Compression + burst Sagittal or coronal plane # Flexion tear drop # (Click on links for further information and examples) Morphology of Injury Compression

10. Compression # (without burst) Compression

11. Compression + burst # Compression Retropulsion Compression Retropulsion

12. Compression Sagittal or coronal plane # Sagittal Coronal

13. Compression Flexion Tear Drop # Tear drop Interspinous widening Disc injury or epidural hematoma

14. Definition: imaging evidence of dissociation along the craniocaudal axis Does not involve significant displacement or rotation component Defined as: < 3.5 mm displacement or 11 degrees rotation Requires disruption of strong facet joint capsules and/or disco-ligamentous structures, implying significant force, and greater clinical severity 3 points toward SLIC score ‘Distraction’ pattern can be thought of as two primary subtypes: Morphology of Injury Distraction Hyper-extensionHyper-flexion (Click on links for further information and examples)

15. Predominantly involves anterior structures Typically, a combination of: ALL Intervertebral disc PLL Facets Distraction Hyper-extension

16. Predominantly involves posterior structures Typically, a combination of: Facets Interspinous ligaments Ligamentum flavum Includes: ‘Perched’ or subluxed facets Distraction Hyper-flexion

17. Definition: evidence of horizontal displacement of one component relative to another Taken as > 3.5 mm displacement or 11 degrees of rotation May be static or dynamic (i.e. flexion-extension radiographs) Requires disruption of both anterior AND posterior supporting structures, implying significant force and injury 4 points toward SLIC score Typified by the following types of injuries: Morphology of Injury Translation/rotation Unilateral facet fracture-dislocation Bilateral facet fracture-dislocation Lateral mass fracture- separation Bilateral pedicle fractures (Click on links for further information and examples)

18. Translation/rotation Unilateral facet fracture-dislocation LeftRight Facet fracture-dislocation Normal

19. Translation/rotation Bilateral facet fracture-dislocation Right LeftMidline Facet fracture-dislocation Traumatic anterolisthesis and teardrop #

20. Translation/rotation Lateral mass fracture-dislocation (AKA isolated articular pillar fracture) Fracture pattern results in isolation and lateral subluxation of the articular pillar

21. Translation/rotation Bilateral pedicle fractures Bilateral pedicle #s

22. Discoligamentous Integrity

23. The discoligamentous complex (DLC) provides significant restraint against motion, making its integrity key to spinal stability Anatomically, the DLC consists of the: Intervertebral disc Anterior longitudinal ligament Posterior longitudinal ligament Ligamentum flavum Interspinous and supraspinous ligaments Facet capsules Discoligamentous Integrity (**strongest component of posterior tension band**) (**strongest component of anterior column**)

24. Evaluation of DLC integrity is either indirect (radiographs, CT or MRI) or direct (MRI only) DLC injury can be: Indirectly diagnosed when normal relationships between bony structures are compromised Directly diagnosed by the presence of abnormal T2 signal The SLIC scoring system divides findings of DLC injuries into two categories according to level of diagnostic confidence: Discoligamentous Integrity (Click on links for further information and examples) Definite DLC Injury (2 points toward SLIC score) Indeterminate DLC Injury (1 point toward SLIC score) Definite ALL Injury Definite Facet Capsule Injury Definite Interspinous Ligament Injury Indeterminate Disc Injury Indeterminate Ligamentous Injury Indeterminate Facet Capsule Injury

25. Requires abnormal widening of the intervertebral disc space May be seen on: Neutrally-positioned radiographs, CT or MRI Extension radiographs Discoligamentous Integrity Definite ALL Injury Disc widening ALL injury

26. Definite Facet Capsule Injury Requires abnormal facet alignment Defined as: Articular apposition < 50%, or > 2 mm diastasis Discoligamentous Integrity Diastasis > 2 mm

27. Definite Interspinous Ligament Injury Requires evidence of incompetence on flexion radiographs Defined as: Abnormal facet alignment Relative angulation > 11 degrees Discoligamentous Integrity

28. Indeterminate Disc Injury Increased T2 signal within disc, involving annulus and nucleus Even in isolation, this finding is highly suspicious for disc injury Disco-ligamentous Integrity Increased signal within nucleus

29. Indeterminate Facet Capsule Injury Increased T2 signal within facets No definite facet injury Remember, definite facet injury requires: Articular apposition > 50% Diastasis > 2 mm Disco-ligamentous Integrity

30. Indeterminate Ligamentous Injury Increased T2 signal within spinal ligaments No definite ligamentous injury Remember, definite injury requires: ALL: abnormal widening of intervertebral disc space Interspinous ligament: focal angulation > 11 degrees or abnormal facet alignment Disco-ligamentous Integrity Increased signal within interspinous ligament

31. Neurologic Status

32. Neurologic status, although not traditionally used in spine trauma classification systems, plays an important role in clinical decision-making Correlates with anatomic severity of injury as it implies failure of osteo- ligamentous protection of the spinal cord and/or nerve roots In certain cases, neurologic status may override all other considerations: Incomplete root or cord injury (ASIA B,C,D) in the presence of ongoing compression Significant neurologic injury in the presence of spondylosis Background ASIA Classification (Click on on link for additional information)

33. Neurologic Status SLIC Scoring Neurologic StatusSLIC Score* Intact0 Root injury1 Complete level (ASIA A) 2 Incomplete level (ASIA B, C, D) 3 * +1 is added for cord compression in setting of any deficit

34. Putting it all Together: The Total SLIC Score

35. The individual score of each domain is then added to make the total SLIC score The total SLIC score is then used to determine optimal management: **By assessing morphology of injury and discoligamentous integrity, the neuroradiologist plays a key role in determining patient management!** Total SLIC Score Determining Patient Management < 4: non-surgical management = 4: equivocal > 4: surgical management

36. Evidence for SLIC

37. Important Studies to Date

38. SLIC has good-to-excellent validity and reliability (both inter- and intra-observer) in determining patient management Least reliable domain of assessment is DLC integrity Studies are mostly retrospective case-series in design Limited to Level II evidence and lower Evidence for SLIC Take home points

39. Summary

40. SLIC is a valid and reliable tool for the classification of subaxial cervical spine injury SLIC is based on the assessment of three domains, which are independent predictors of clinical outcome: The score of each domain is added to give the total SLIC score, which helps determine whether surgery is indicated By assessing morphology of injury and DLC integrity, the neuroradiologist plays a an important role in determining optimal patient management Morphology of Injury Disco-ligamentous Integrity Neurologic Status (Click on links to review) SLIC Score What the Neuroradiologist Should Know

41. Thanks for your attention!

42. References Vaccaro AR, Hulbert RJ, Patel AA et al. The subaxial cervical spine injury classification system: a novel approach to recognize the importance of morphology, neurology and integrity of the disco-ligamentous complex. Spine 2007; 32 (21): 2365-2374 Dvorak MF, Fisher CG, Feelings MG et al. The surgical approach to subaxial cervical spine injuries. Spine 2007; 32: 2620-2629 Joaquim AF, Patel AA, Vaccaro AR. Cervical injuries scored according to the Subaxial Injury Classification System: an analysis of the literature. J of Craniovertebral Junction Spine 2014; 2: 65-72 Joaquim AF, Ghizoni E, Tedeschi H et al. Clinical results of patients with subaxial cervical spine trauma treated according to the SLIC score. J of Spinal Cord Med 2014; 420-424 Samuel S, Lin JL, Smith MM et al. Subaxial injury classification scoring system treatment recommendations: external agreement study based on retrospective review of 185 patients. Spine 2015; 40: 137-142 Stone AT, Bransford RJ, Lee MJ et al. Reliability of classification systems for subaxial cervical injuries. Evid Based Spine Care J. 2010; 1: 19-26 Lee NWJ, Yoon SH, Kim YJ et al. Interobserver and intraobserver reliability of suba-axial injury classification and severity scale between radiologist resident and spine surgeon. J Korean Neurosurg Soc 2012; 52: 200-203 Gupta P, Kumar A, Gamagati S. Mechanism and patterns of cervical spine fractures-dislocations in vertebral artery injury. J Craniovertebral Junction Spine. 2012 Jan-Jun; 3(1): 11–15 Dreizen D, Letzing M, Sliker CW et al. Multidetector CT of blunt cervical spine trauma in adults. Radiogrphics. 2014; 34; 7: 1842-65 Rao SK, Wasyliw C, Nunez DB. Spectrum of imaging findings in hyperextension injuries of the neck. Radiographics. 2005; 25: 1239-54

43. Supplementary Slides

44. ASIA Scoring System http://www.asia-spinalinjury.org/elearning/ASIA_ISCOS_high.pdf

45. Presentation Map Morphology of Injury Disco-ligamentous Integrity Neurologic Status Compression (1 or 2 points) Distraction (3 points) Translation/rotation (4 points) Compression Compression + burst Sagittal or coronal plane # Flexion tear drop # Defninite ALL Injury Definite Facet Capsule Injury Definite Interspinous Ligament Injury Indeterminate Disc Injury Indeterminate Ligamentous Injury Indeterminate Facet Capsule Injury Indeterminate DLC Injury (1 point) Definite DLC Injury (2 points) Unilateral facet fracture-dislocation Bilateral facet fracture-dislocation Lateral mass fracture-separation Bilateral pedicle fractures Hyper-extension Hyper-flexion (Click on links to return to desired section)