Update on subaxial cervical trauma classification systems

Author’s Accepted Manuscript Update on subaxial cervical trauma classification systems Tyler M. Kreitz, Gregory D. Schroeder, Alexander R. Vaccaro www.elsevier.com/locate/enganabound

PII: DOI: Reference:

S1040-7383(16)30036-3 http://dx.doi.org/10.1053/j.semss.2016.09.002 YSSPS588

To appear in: Seminars in Spine Surgery Cite this article as: Tyler M. Kreitz, Gregory D. Schroeder and Alexander R. Vaccaro, Update on subaxial cervical trauma classification systems, Seminars in Spine Surgery, http://dx.doi.org/10.1053/j.semss.2016.09.002 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Update on Subaxial Cervical Trauma Classification Systems Tyler M. Kreitz MD, Gregory D. Schroeder MD, Alexander R. Vaccaro MD, PhD, MBA

Rothman Institute at Thomas Jefferson University Hospital, Philadelphia, PA Corresponding author: Alexander R. Vaccaro MD, PhD, MBA Rothman Institute 925 Chestnut St., 5t Floor. Philadelphia, PA 19107. USA

Abstract Injury classification systems guide management, predict prognosis, and allow for communication between providers. Several classification systems for subaxial cervical trauma have been described. Historically, classifications focused on osseous morphology, inferred mechanism of action, and stability. Later, neurologic status of the patient and integrity of the posterior ligamentous complex were described as important determinants of treatment. This review will detail important historic classifications, the Subaxial Injury Classification (SLIC) and Severity Scale, and the novel AOSpine Subaxial Cervical Spine Injury Classification System.

Introduction The subaxial cervical spine, C3-C7, is a highly mobile section of the spine which, when injured, may result in significant morbidity. A standardized classification system for traumatic cervical spine injuries is necessary as miscommunication or misdiagnosis can have significant impact on treatment and expected outcomes. Classification systems allow for standardization of injuries in order to guide treatment and predict prognosis of

the injury. Classification systems are of increased importance in the setting of trauma as these patients are likely to be taken care of in a multidisciplinary team approach and/or transferred to tertiary care centers where communication between care providers is of utmost importance. Classification systems also allow for standardization of injuries for academic purposes. An ideal classification system is all-inclusive, mutually exclusive, and straightforward without ambiguity 1. The system highlights injury characteristics relevant for patient care in a distinct reproducible manner between observers. Since the discovery of x-rays, several classification systems describing traumatic injuries to the subaxial cervical spine have been described 1–6. Existing classification systems have provided varying degrees of accuracy, clinical relevance, and reproducibility, and none of these previous systems has gained universal acceptance. Historical Classifications Prior to the routine use of radiographs, spine injuries were described as having or not having concomitant spinal cord injury based on clinical presentation and neurologic examination7. Böhler first described spinal cord injuries based on radiographic injury morphology during World War I8,9. Since that time, several classification systems have been developed focusing on fracture morphology, mechanism of injury, and injury stability. Holdsworth published the first spinal injury classification describing mechanism of injury in 1970, based on his observation of 2,000 patients with traumatic spine injuries. This classification was designed for injuries in the cervical and thoracic spine, and placed an emphasis on stable versus unstable injuries. While the actual classification is no longer clinically used, in this classification Holdsworth coined the

term “burst fracture” to describe an injury that disrupts one or both endplates; furthermore, Holdsworth identified that the integrity of the posterior ligamentous complex (PLC) is one of the keys to spinal stability after a spine fracture4. AllenFerguson described the first broadly used mechanistic classification system in 1982. Their system was based on review of 165 fracture radiographs and classified injuries based on six distinct inferred mechanisms based on fracture pattern; compressive flexion, vertical compression, distractive flexion, compressive extension, distractive extension, and lateral flexion10. The Allen-Ferguson classification contributed significantly to injury mechanistic nomenclature, but several independent validation studies have demonstrated poor user reliability11–13. Harris’ would later expand on this mechanism based system, designating flexion, flexion and rotation, hyperextension and rotation, vertical compression, extension, and lateral flexion type injuries 3. In 1994, Magerl et al. published their classification of injuries based on three primary mechanisms (compression/A type fractures, distraction/B type fractures and rotational/C type fractures) with a total of 53 subtypes. This system was designed based on incremental increase in fracture severity between the three main types (A B C)14. The Magerl system was primarily used for thoracolumbar injuries, but has also been extrapolated to describe injuries to the subaxial cervical spine. Due to its complexity and significant number of fracture subtypes, multiple authors demonstrated poor to fair intraobserver reliability15,16. These previous classification systems focused on overly descriptive mechanistic terminology and were unable to be reliably used or clinically validated 12. Recognizing the limitations of these previous classifications, more recent classifications have focused on fracture morphology, as well as other critical factors that

affect the treatment algorithm such as the integrity of the posterior ligamentous complex and the neurologic status of the patients.

Subaxial Cervical Spine Injury Classification (SLIC) System Vaccaro et al developed the Subaxial Injury Classification (SLIC) and Severity Scale in 200711. This system was developed as an attempt to consolidate and standardize previous classification systems and develop an associated treatment algorithm. The SLIC was the first classification to incorporate the integrity of the discoligamentous complex (DLC) and the neurologic status of the patient in addition to fracture morphology. Fracture morphology is classified as compression injuries; translational/rotational injuries and distraction injuries. The DLC is classified as intact, disrupted, or indeterminate. Finally, neurologic status is classified as intact, nerve root deficit, complete or incomplete spinal cord injury, and continuous cord compression in setting of neurologic deficit (Table 1). The morphology, DLC integrity, and neurologic classification are each assigned an integer value based on severity. A combined injury severity score and corresponding treatment recommendation is then determined. The SLIC recommends non-operative treatment for injuries with a score of less than four, and operative intervention for those greater than four. If the injury score is four, operative on nonoperative treatment may be appropriate depending on patient and surgeon variables. Vaccaro et al. initially reported treatment recommendation agreement of 93.3% among raters using the SLIC injury severity treatment algorithm11. An independent

retrospective analysis by Samuel et al. evaluated agreement between treatment received and SLIC recommended treatment amongst 185 patients who presented with subaxial cervical spine trauma. They demonstrated substantial agreement between treatment received and SLIC recommendations; 96.3% agreement among surgically managed patients and 93.6% agreement for those treated non-surgically17. Several independent analyses have been performed evaluating inter- and intra-observer reliability of the SLIC system12,18,19. Stone et al demonstrated excellent inter-observer reliability using the SLIC system for morphology, DLC, and neurological status [Intraclass Correlation (ICC)=0.86, 0.90, and 0.98 respectively] and excellent intra-observer reliability (ICC=0.94, 0.94, 0.99) in the analysis of 50 patients with subaxial injuries. Additionally, independent validation by Lee et al. also demonstrated significant inter- and intra-observer agreement amongst trained observers evaluating 75 subaxial trauma cases using the SLIC system. They demonstrated substantial inter-observer agreement in injury morphology (CC=0.603), total SLIC severity sacle (ICC=0.775), and fair agreement in DLC score (ICC=0.304). Intra-observer agreement was substantial for all observers18. More recently, a prospective independent analysis of the SLIC by Van Middendorp et al. demonstrated poor intra-observer reliability for morphology (κ=0.29) and average reliability (κ=0.46) for DLC classification19. Primary disagreement occurred in the classification of a flexion teardrop fracture with concomitant DLC and facet injury. According to the SLIC, teardrop patterns are mentioned as both severe translational/rotational injuries and less severe compressive morphology patterns11. While accepted favorably compared to historical systems, there was disagreement in morphology patterns between users of the SLIC system.

AOSpine Subaxial Cervical Spine Injury Classification System The AOSpine Subaxial Cervical Spine Injury Classification System was recently developed by international academics as an all-encompassing and universally accepted means of classifying cervical spine injuries with previous disagreements in mind20. Similar to the AOSpine Thoracolumbar Spine Injury Classification System21, this system is characterized by the morphologic characteristics of injuries based CT and radiographic findings. The AOSpine system was developed as a simple yet comprehensive system with high inter- and intra-observer reliability. A recent independent evaluation of the novel AOSpine Subaxial Cervical Spine Injury Classification System has demonstrated high inter- and intra-observer reliability (κ=0.61 and 0.68 respectively) among six trained observers22. The AOSpine Subaxial Cervical Spine Injury Classification System describes injuries based on four criteria; (1) injury morphology, (2) facet injury, (3) neurologic status, and (4) case-specific modifiers. Three basic morphology types are described; Type A compression injuries, Type B disruption of the anterior or posterior tension band without spinal malalignment, and Type C translational injuries (Table 2). Facet injuries (Type F) are described with increasing severity from non-displaced fractures (Type F1) to facet subluxation (Type F4) (Table 2). Neurologic status (N) is described with increasing neurologic compromise (Table 3). Case-specific modifiers (M) include; PLC injury, acute disc herniation, spondylotic disease, and concomitant vertebral artery injury (Table 3). Injuries are described by their level, primary injury morphology, any secondary

injury subtypes, neurologic status and associated modifiers. Secondary injury types and case specific modifiers are listed in parenthesis after injury level and primary injury type. Cervical spine compression injuries (AOSpine type A) result from failure of the anterior column (vertebral body) and/or the posterior structures (spinous processes, lamina). Minor compression injuries result in soft tissue injuries or isolated lamina or spinous process fractures (AOSpine type A0). Central cord syndrome in the absence of fracture may be designated by type A0. Vertebral body compression fractures that do not extend into the posterior wall of the vertebral body, may involve a single endplate (AO type A1), or both endplates in a coronal split or pincer pattern (AO type A2). Burst fractures are compression type injuries with extension into the posterior wall of the vertebral body with varying degrees of bony retropulsion into the spinal canal. Burst patterns may involve one (AOSpine type A3) or both endplates (AOSpine type A4). Tension band injuries (AOSpine type B) result from disruption of either the anterior or posterior tension band structures of the subaxial cervical spine without translation (AOSpine type C) of the injured vertebrae. A posterior tension band injury may involve bony structures alone (AOSpine type B1) or with associated capsular and ligamentous structures (AOSpine type B2). These injuries may extend anteriorly through the vertebral body or intervertebral disc. Anterior tension band injuries involve disruption of either the intervertebral disc or body in an ankylosed spine (AOSpine type B3). These injuries maintain an intact posterior hinge preventing vertebral translation. Displacement of the injured vertebrae with anterior and posterior tension band injuries is instead classified as translational (AOSpine Type C).

Translational injuries (AOSpine Type C) occur with displacement of one vertebral body relative to another. Translation may occur in any direction (anterior, posterior, lateral, vertical), and is often associated with vertebral body or posterior element fracture (AO type C). Any associated type A or B injury with translation should first be classified as translational type C with subtype A or B in parenthesis. These are very unstable injuries. Integrity of the facet joint complex is an important determinant of stability in subaxial cervical spine trauma. Injuries vary from minor non-displaced fractures (AOSpine type F1), to displaced fractures with fragment > 1cm or 40% of the lateral mass (AOSpine type F2) (Figure 1), to facet injuries that result in a floating lateral mass (AOSpine type F3) of facet subluxation (AO type F4). In unilateral facet fractures, stability may be determined based on the percentage of lateral mass involvement as measured on CT scan. Spector et al. demonstrated increased risk of failure of nonoperative treatment in patients with unilateral facet fractures involving >40% of the height of the intact lateral mass or absolute height > 1cm 23. Under the AOSpine classification, if similar subtype injury exists to both facets at the same level, the bilateral (BL) modifier is used. In the case of differing subtype injuries to the same vertebrae facets, the right facet is described first, followed by the left. Neurologic status is graded similar to that of the thoracolumbar system21. Injuries are described as neurologically intact (N0), transient neurologic deficit that has resolved (N1), presence of radiculopathy (N2), incomplete spinal cord injury (N3), complete spinal cord injury (N4), and undetermined status (NX). A “+” is given in the case of ongoing neurologic compression in the setting of incomplete deficit. Case specific

modifiers are used to describe unique circumstances relevant to clinical decision-making. These include injury to the posterior ligamentous complex (M1) as measured by MRI findings, injury morphology, and clinical evaluation. The PLC includes the facet capsule, supraspinous, and interspinous ligaments. Distraction type injuries often result in injury to the posterior ligamentous complex. Facet capsule integrity may differentiate minor injuries from more significant unstable injuries 24. Determining the extent of injury of the PLC based on MRI alone has proven to be inconsistent, and should not be used along with injury morphology and clinical examination to determine stability of injury and associated treatment10,25. Additional modifiers include; critical disc herniation (M2), Metabolic/spondylotic bone disease (M3) [Diffuse Idiopathic Skeletal Hyperostosis (DISH), Ankylosing Spondylitis (AS), Ossification of the Posterior Longitudinal Ligament (OPLL), Ossification of the Ligamentum Flavum (OLF)], and vertebral artery injury (M4). Initial reliability analysis from the developers of the study found substantial intraobserver (κ = 0.75) and interobserver κ = 0.64) for all injury subtypes13. More recently the reliability of this classification has been independently validated, with findings of substantial interobserver reliability for the three main types of injury (κ = 0.61), and moderate reliability for the subtypes (κ = 0.57). Importantly, they also reported an improvement in interobserver reliability using the AOSpine classification (κ = 0.61; 0.57) compared to the Allen and Ferguson classification (κ = 0.46). Currently no treatment algorithm has been published to accompany the AOSpine Subaxial Cervical Spine Injury Classification System, but similar to the approach taken for the development of the surgical algorithm for the AOSpine Thoracolumbar Injury Classification System,

multiple studies are underway25–29; the results of these studies will help establish an evidence-based treatment algorithm for the AOSpine Subaxial Cervical Spine Injury Classification System.

Case Examples: Figure 2 is a 38 year-old male who presented with neck pain after a snowboarding accident. CT scan of the cervical spine demonstrates a fracture of C7 that included both endplates as well as the posterior vertebral wall pattern. Using the AOSpine classification, this is an A4 (N0) injury; using the SLIC classification, it is a burst fracture without DLC incongruity or neurologic impairment (severity score of 2).

Figure 3 is a 58 year-old female who presented with neck pain and incomplete spinal cord injury after a motor vehicle collision. CT and MRI scans of the cervical spine demonstrates a translational injury with C6/7 bilateral perched facets and injury to the DLC. Using the AOSPine classification, this is a type C (F4 BL, N3) injury; using the SLIC classification, it is distraction type with DLC incongruity and incomplete spinal cord injury (severity score of 9).

Figure 4 is a 66 year-old male with a history of ankylosing spondylitis who presented with neck pain, deformity, and incomplete spinal cord injury after a fall down

stairs. CT and MRI scans of the cervical spine demonstrates a C4/5 translational injury in an ankylosed spine. Using the AOSpine classification, this is a type C (N3, M3) injury; using the SLIC classification, is is a translational injury with DLC incongruity (severity score of 10).

Conclusion To date, there is no universally accepted classification system for injuries in the subaxial spine. Historical classification systems have provided varying degrees of accuracy, clinical relevance, and reproducibility. Most recently, the AOSpine Subaxial Cervical Spine Injury Classification System was developed as a simple yet comprehensive classification system for clinical and academic purposes. Like the AOSpine thoracolumbar spine injury classification system, it is based primarily on CT and radiographic injury morphology with associated case specific modifiers. This system has demonstrated significant independent inter- and intra-observer reliability, but without a surgical algorithm, its clinical utility is unclear. Further studies are needed to develop the algorithm, as well as demonstrate its efficacy and practicality in the management of patients with subaxial cervical spine injuries.

Figure Legend Figure 1. A parasagittal CT image demonstrating a minimally displaced C7 facet fracture of the superior articular process. This fragment measures 8.5mm (AO Type F1).

Figure 2: Sagittal and axial CT images demonstrate a fracture through both endplates and the posterior verbal body wall. Figure 3: Midsagittal/parasagittal CT images and T2-weighted MRI image demonstrating translational injury of C6/7 with perched facets. Figure 4: Midsagittal CT and T2-weighted MRI image demonstrating translational injury of C4/5 in an ankylosed spine.

Drs. Schroeder and Kreitz report no proprietary or commercial interest in any product mentioned or concept discussed in this article. Dr. Vaccaro has the following to disclose: Health Care Entity Relationships and Investments Entity Relationship (See Legend Below) Replication Medica d DePuy a Medtronics a,c Stryker Spine a,c, Globus a,c,d Paradigm Spine d Stout Medical a,d Progressive Spinal Technologies b,d Advanced Spinal Intellectual Properties d Aesculap c Spine Medica d Computational Biodynamics d Spinology d In Vivo d Flagship Surgical b,d Cytonics d Bonovo Orthopaedics d Electrocore d Gamma Spine d Location Based Intelligence d FlowPharma d Gerson Lehrman Group a Guidepoint Global a Medacorp a Rothman Institute and Related Properties d AO Spine b Innovative Surgical Design a,b,d Association of Collaborative Spine Research b Orthobullets a Thieme c Jaypee c Elseviere c Taylor Francis/Hodder and Stoughton c Expert testimony a Nuvasive a Vertiflex d Avaz Surgical d Clinical Spine Surgery f Spine Journal f Prime Surgeons b,d Dimension Orthotics, LLC d Spine Therapy Network, Inc b Legend a. Consulting / Independent Contractor b. Service on Scientific Advisory Board / Board of Directors / Service on Committees c. Receipt of Royalty Payments d. Stock / Stock Option Ownership Interests e. Institutional / Educational Grant f. Deputy editor/ Editor

References: 1.

van Middendorp JJ, Audige L, Hanson B, et al. What should an ideal spinal injury classification system consist of? A methodological review and conceptual proposal for future classifications. Eur Spine J Off Publ Eur Spine Soc Eur Spinal Deform Soc Eur Sect Cerv Spine Res Soc. 2010;19(8):1238-1249. doi:10.1007/s00586-010-1415-9.

2.

Allen BLJ, Ferguson RL, Lehmann TR, et al. A mechanistic classification of closed, indirect fractures and dislocations of the lower cervical spine. Spine. 1982;7(1):1-27.

3.

Harris JHJ, Edeiken-Monroe B, Kopaniky DR. A practical classification of acute cervical spine injuries. Orthop Clin North Am. 1986;17(1):15-30.

4.

Holdsworth F. Fractures, dislocations, and fracture-dislocations of the spine. J Bone Joint Surg Am. 1970;52(8):1534-1551.

5.

Aebi M, Nazarian S. [Classification of injuries of the cervical spine]. Orthopade. 1987;16(1):27-36.

6.

Blauth M KA, Mair G, Schmid. Classification of injuries of the subaxial cervical spine. AO Spine Man Clin Appl. 2007;Vol 2 Stuttgart: Thieme:21-38.

7.

Burrell HL. I. Fracture of the Spine: A Summary of All the Cases (244) which were Treated at the Boston City Hospital from 1864 to 1905. Ann Surg. 1905;42(4):481-506.

8.

Bohler L. The treatment of fractures. A translation of “Technik der Knochenbruchbehandlung im Frieden und im Kriege.” ME Vienna Austria Steinberg Wilhelm Maudrich. 1929.

9.

Bohler L. Die Technik der Knochenbruchbehandlung. 1951;Wien: Maudrich.

10. Vaccaro AR, Rihn JA, Saravanja D, et al. Injury of the posterior ligamentous complex of the thoracolumbar spine: a prospective evaluation of the diagnostic accuracy of magnetic resonance imaging. Spine. 2009;34(23):E841-E847. doi:10.1097/BRS.0b013e3181bd11be. 11. 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. doi:10.1097/BRS.0b013e3181557b92. 12. Stone AT, Bransford RJ, Lee MJ, et al. Reliability of classification systems for subaxial cervical injuries. Evid-Based Spine-Care J. 2010;1(3):19-26. doi:10.1055/s-0030-1267064.

13. Urrutia J, Zamora T, Campos M, et al. A comparative agreement evaluation of two subaxial cervical spine injury classification systems: the AOSpine and the Allen and Ferguson schemes. Eur Spine J Off Publ Eur Spine Soc Eur Spinal Deform Soc Eur Sect Cerv Spine Res Soc. March 2016. doi:10.1007/s00586-0164498-0. 14. Magerl F, Aebi M, Gertzbein SD, et al. A comprehensive classification of thoracic and lumbar injuries. Eur Spine J Off Publ Eur Spine Soc Eur Spinal Deform Soc Eur Sect Cerv Spine Res Soc. 1994;3(4):184-201. 15. Oner FC, Ramos LMP, Simmermacher RKJ, et al. Classification of thoracic and lumbar spine fractures: problems of reproducibility. A study of 53 patients using CT and MRI. Eur Spine J Off Publ Eur Spine Soc Eur Spinal Deform Soc Eur Sect Cerv Spine Res Soc. 2002;11(3):235-245. doi:10.1007/s00586-001-0364-8. 16. Aebi M. Classification of thoracolumbar fractures and dislocations. Eur Spine J Off Publ Eur Spine Soc Eur Spinal Deform Soc Eur Sect Cerv Spine Res Soc. 2010;19 Suppl 1:S2-S7. doi:10.1007/s00586-009-1114-6. 17. Samuel S, Lin J-L, Smith MM, et al. Subaxial injury classification scoring system treatment recommendations: external agreement study based on retrospective review of 185 patients. Spine. 2015;40(3):137-142. doi:10.1097/BRS.0000000000000666. 18. Lee WJ, Yoon SH, Kim YJ, et al. Interobserver and Intraobserver Reliability of Sub-Axial Injury Classification and Severity Scale between Radiologist, Resident and Spine Surgeon. J Korean Neurosurg Soc. 2012;52(3):200-203. doi:10.3340/jkns.2012.52.3.200. 19. van Middendorp JJ, Audige L, et al. The Subaxial Cervical Spine Injury Classification System: an external agreement validation study. Spine J Off J North Am Spine Soc. 2013;13(9):1055-1063. doi:10.1016/j.spinee.2013.02.040. 20. Vaccaro AR, Koerner JD, Radcliff KE, et al. AOSpine subaxial cervical spine injury classification system. Eur Spine J Off Publ Eur Spine Soc Eur Spinal Deform Soc Eur Sect Cerv Spine Res Soc. February 2015. doi:10.1007/s00586-015-38313. 21. Vaccaro AR, Oner C, Kepler CK, et al. AOSpine thoracolumbar spine injury classification system: fracture description, neurological status, and key modifiers. Spine. 2013;38(23):2028-2037. doi:10.1097/BRS.0b013e3182a8a381. 22. Urrutia J, Zamora T, Yurac R, et al. An independent inter- and intra-observer agreement evaluation of the AOSpine subaxial cervical spine injury classification system. Spine. November 2015. doi:10.1097/BRS.0000000000001302.

23. Spector LR, Kim DH, Affonso J, et al.. Use of computed tomography to predict failure of nonoperative treatment of unilateral facet fractures of the cervical spine. Spine. 2006;31(24):2827-2835. doi:10.1097/01.brs.0000245864.72372.8f. 24. Onan OA, Heggeness MH, Hipp JA. A motion analysis of the cervical facet joint. Spine. 1998;23(4):430-439. 25. Schroeder GD, Kepler CK, Koerner JD, et al. A Worldwide Analysis of the Reliability and Perceived Importance of an Injury to the Posterior Ligamentous Complex in AO Type A Fractures. Glob Spine J. 2015;5(5):378-382. doi:10.1055/s-0035-1549034. 26. Sadiqi S, Oner FC, Dvorak MF, et al.. The Influence of Spine Surgeons’ Experience on the Classification and Intraobserver Reliability of the Novel AOSpine Thoracolumbar Spine Injury Classification System-An International Study. Spine. 2015;40(23):E1250-E1256. doi:10.1097/BRS.0000000000001042. 27. Schroeder GD, Vaccaro AR, Kepler CK, et al. Establishing the injury severity of thoracolumbar trauma: confirmation of the hierarchical structure of the AOSpine Thoracolumbar Spine Injury Classification System. Spine. 2015;40(8):E498-E503. doi:10.1097/BRS.0000000000000824. 28. Schroeder GD, Kepler CK, Koerner JD, et al. Can a Thoracolumbar Injury Severity Score Be Uniformly Applied from T1 to L5 or Are Modifications Necessary? Glob Spine J. 2015;5(4):339-345. doi:10.1055/s-0035-1549035. 29. Schroeder GD, Kepler CK, Koerner JD, et al. A Worldwide Analysis of the Reliability and Perceived Importance of an Injury to the Posterior Ligamentous Complex in AO Type A Fractures. Glob Spine J. 2015;5(5):378-382. doi:10.1055/s-0035-1549034.

Table 1. The Subaxial Cervical Spine Injury Classification (SLIC) System11 Table 1 Injury Variables

Score

Morphology Compression fracture

1

Burst fracture

2

Distraction

3

Rotation/translation

4

Discoligamentous Complex (DLC) Intact

0

Indeterminate

1

Disrupted

3

Neurologically intact

0

Nerve root injury

1

Complete spinal cord injury

2

Incomplete spinal cord injury

3

Continuous cord compression in setting of neurodeficit

(+) 1

Neurology

Table 2. The AOSpine Subaxial Cervical Spine Injury Classification System20 Table 2 Subgroup Description Type A—Compression Fractures Soft tissue injury or minor bony injury ie. spinous A0 process or lamina fracture A1

A fracture through a single endplate that does not extend into the posterior wall

A2

A fracture through a both endplate that does not extend into the posterior wall

A3

A fracture through a single endplate that does extend into the posterior wall (incomplete burst)

A4

B1

A fracture through both endplates that does extend into the posterior wall (complete burst) Type B—Tension Band Injuries A completely osseous posterior tension band injury

B2 B3

C

F1 F2 F3 F4

Posterior tension band injury affecting capsule/ligamentous structures Disruption of the anterior tension band Type C—Translational Injuries Any injury that results in translation of the vertebral body relative to another Type F-Facet Injuries Minor non-displaced fracture Displaced fracture with fragment >1cm or 40% of the lateral mass Facet injury resulting in floating lateral mass Facet subluxation

Table 3. Neurologic status and case-specific modifiers for the AOSpine Subaxial Cervical Spine Injury Classification System20 Table 3 Subgroup Description Neurologic Status N0 No neurologic injury N1 Resolved temporary neurologic injury N2 Presence of radiculopathy Incomplete spinal cord injury or cauda N3 equina syndrome N4 Complete spinal cord injury A reliable neurologic exam cannot be Nx obtained (+)

M1 M2 M3 M4

Ongoing neurologic compression Patient Specific Modifiers Injury to PLC Critical Disc Herniation Metabolic/spondylotic Bone Disease Vertebral Artery Injury