Traumatic Thoracolumbar Spine Injuries: What the Spine Surgeon Wants to Know 1

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1 Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at TRAUMA/EMERGENCY RADIOLOGY 2031 Traumatic Thoracolumbar Spine Injuries: What the Spine Surgeon Wants to Know 1 ONLINE-ONLY SA-CME See /search/rg LEARNING OBJECTIVES After completing this journal-based SA- CME activity, participants will be able to: Describe the use of the TLICS in evaluating imaging studies of traumatic spine injury. Recognize the role of bone and softtissue integrity in determining spine stability and injury management. Identify and report bone and soft-tissue injuries to spine surgeons using a patterned checklist approach. Bharti Khurana, MD Scott E. Sheehan, MD, MS Aaron Sodickson, MD, PhD Christopher M. Bono, MD Mitchel B. Harris, MD The Thoracolumbar Injury Classification and Severity Score (TLICS) is a scoring and classification system developed by the Spine Trauma Study Group in response to the recognition that previous classification systems have limited prognostic value and generally do not suggest treatment pathways. The TLICS provides a spine injury severity score based on three components: injury morphology, integrity of the posterior ligamentous complex (PLC), and neurologic status of the patient. A numerical score is calculated for each category, with a lower point value assigned to a less severe or less urgent injury and a higher point value assigned to a more severe injury requiring urgent management. The total score helps guide decision making about surgical versus nonsurgical management. The TLICS also emphasizes the importance of magnetic resonance imaging in evaluating PLC injury and acknowledges that the primary driver of surgical intervention is the patient s neurologic status. Knowledge of PLC anatomy and its significance is essential in recognizing unstable injuries. Signs of PLC injury at computed tomography include interspinous distance widening, facet joint widening, spinous process fracture, and vertebral subluxation or dislocation. Familiarity with the TLICS will help radiologists who interpret spine trauma imaging studies to effectively communicate findings to spine trauma surgeons. Supplemental material available at Scan this code for access to supplemental material on our website. Introduction Mechanical stability is a critical factor for treatment decision making in patients with traumatic spine injury. Spine stability is defined as the ability to prevent the development of neurologic injury and progressive deformity in response to physiologic loading and a normal range of movement (1). Spine stability relies on the integrity of both bone and ligamentous components. Injury to either or both can result in spine instability that requires surgical stabilization (2). Numerous thoracolumbar spine injury classification systems have been developed to guide clinical and surgical treatment (3 5). Early classification systems were based on anatomic structures or proposed injury mechanisms determined through Abbreviations: PLC = posterior ligamentous complex, STIR = short inversion time inversion-recovery, 3D = three-dimensional, TLICS = Thoracolumbar Injury Classification and Severity Score RadioGraphics 2013; 33: Published online /rg Content Codes: 1 From the Departments of Radiology (B.K., S.E.S., A.S.) and Orthopedic Surgery (C.M.B., M.B.H.), Brigham and Women s Hospital, 75 Francis St, Boston, MA Recipient of a Magna Cum Laude award for an education exhibit at the 2012 RSNA Annual Meeting. Received March 4, 2013; revision requested April 4 and received May 17; accepted May 23. For this journal-based SA-CME activity, the authors C.M.B. and M.B.H. have disclosed financial relationships (see p 2045); the other authors, editor, and reviewers have no relevant relationships to disclose. Address correspondence to B.K. ( bkhurana@gmail.com). RSNA, 2013 radiographics.rsna.org

2 2032 November-December 2013 radiographics.rsna.org Figure 1. Computer-generated lateral three-dimensional (3D) image of the thoracolumbar spine shows the components of the anterior (yellow) and posterior (orange) spinal motion segments. Figure 2. Computer-generated lateral 3D image shows the normal anatomic configuration of the PLC, which includes the supraspinous ligament, interspinous ligament, facet capsules, and ligamentum flavum. analysis of osseous components on radiographs and computed tomography (CT) images. Radiologists are arguably most familiar with the Denis three-column classification system, which is based on injury morphology and mechanism and includes four main categories: compression fracture, burst fracture, seat belt injury, and fracturedislocation (6). The differentiating feature of the Denis classification is its emphasis on the fracture involvement of the middle column, which includes the posterior half of the vertebral body and intervertebral disk and the posterior longitudinal ligament. Denis (7) specified that injury to the middle column renders the spine mechanically unstable and that all thoracolumbar burst fractures are unstable injuries that require surgical stabilization. Subsequent modifications of the Denis classification have recognized that with an intact posterior ligamentous complex (PLC), two-column unstable injuries can be successfully treated nonsurgically. This has created a confusing category of burst fractures referred to as unstable stable fractures (5). The Denis system does not provide prognostic information or consider the patient s neurologic status, and therefore it cannot adequately guide surgical intervention (8,9). The Arbeitsgemeinschaft für Osteosynthesefragen (AO) classification was the next major evolution in spinal injury classification (10). It divides injuries into three categories: compression (group A), distraction (group B), and translation or rotation (group C), with up to nine subtypes in each category based on fracture location, morphology, osseous or ligamentous disruption, and direction of displacement. One of its principle rationales is that groups A through C represent a continuum of progressively increasing injury severity and instability, with a concomitant increasing likelihood of the need for surgical stabilization. The AO system emphasizes the importance of injuries to soft-tissue structures such as the PLC, intervertebral disks, and anterior longitudinal ligament with respect to spine instability. Because of its highly detailed subclassifications, the AO system has shown limited interobserver variability. It is similar to its predecessors in that it does not incorporate the patient s neurologic status (3). Although magnetic resonance (MR) imaging allows direct and accurate visualization and assessment of PLC integrity after spine trauma, the importance of the PLC has been poorly addressed in existing classification systems. The need for a reliable, reproducible, clinically relevant, prognostic classification system with an optimal balance of ease of use and detail of injury description contributed to the development of a new classification system for thoracolumbar spine trauma, the Thoracolumbar Injury Classification and Severity Score (TLICS) (11 13). This article reviews the functional anatomy of the thoracolumbar spine, highlights the CT and MR imaging appearances of PLC integrity and disruption, and familiarizes radiologists with the TLICS so that they can adopt a pattern-based approach for efficient imaging interpretation and communication with spine surgeons.

3 RG Volume 33 Number 7 Khurana et al 2033 Figure 3. Computer-generated 3D models illustrate the similar mechanical structure of the thoracolumbar spine and a construction crane. Lateral views of the spine (a) and a construction crane (b) show an anteriorly displaced center of gravity that creates a compressive force (dotted arrow) on the spinal vertebrae similar to the force on the crane lifting arm. The resulting baseline flexion force (solid arrow) on the PLC is similar to the tension on the crane s lifting cable. Spine Anatomy and Functional Unit The spinal motion segment is the principle functional unit of the spine and consists of two vertebrae and the interconnecting soft tissues (14) (Movie 1). The anterior portion of the functional unit contains two aligned vertebral bodies, the intervertebral disk, and the anterior and posterior longitudinal ligaments. The posterior portion consists of the vertebral arches, facet joints, and posterior elements (Fig 1). Axial loading is supported primarily by the vertebral bodies and intervertebral disks. The vertebral bodies resist compressive loading. The intervertebral disks contain a central nucleus pulposus that absorbs and hydrostatically distributes compressive loading and an annulus fibrosus that resists the resulting circumferential tensile stress (14) (Movie 2). The posterior portion of the spinal motion segment guides spinal movement, with the type of motion determined by the plane of facet articulation. The coronal orientation of the thoracic facet joints minimizes extension but allows rotation, while the sagittal oblique orientation of the lumbar articular facets minimizes rotation (Movie 1). The posterior portion of the motion segment contains the PLC, which plays a critical stabilizing role. The PLC is composed of the supraspinous ligament, interspinous ligaments, articular facet capsules, and ligamentum flavum (Fig 2). The supraspinous ligament is a strong cordlike ligament that connects the tips of the spinous processes from C7 to the sacrum. The interspinous ligaments are weak, thin, membranous structures that connect the adjacent spinous processes. Both the supraspinous and interspinous ligaments have a high collagen content, and their high tensile strength limits flexion of the spine (14). The ligamentum flavum is a thick broad structure that connects the laminae of the adjacent vertebrae. It has a high elastin content and exerts a contractile force on the vertebral arches when it is elongated during flexion. The contractile force of the ligamentum flavum presses the vertebrae together and keeps them aligned (15). The facet joints are continuations of the laminae and are covered with hyaline cartilage on their articulating surfaces. They are the primary elements that act against rotational or torsional forces. In active extension, the facets function as a fulcrum, thereby reducing the load on the anterior column (13,15). The PLC serves as the posterior tension band of the spinal column. Because the axis of rotation is immediately anterior to or just within the anterior half of the vertebral body in the erect posture, there is a constant counterbalancing of the posterior ligament and erector spinae muscle forces at rest and at motion to resist compressive forces on the vertebral bodies (16). The mechanical structure of the spine has been compared with that of a construction crane where the weight lifted is far anterior, causing the boom (corresponding to the vertebral bodies) to be under compressive forces and the guy wires (corresponding to the PLC) to be under tension (Fig 3) (17).

4 2034 November-December 2013 radiographics.rsna.org TLICS Categories The TLICS, developed by the Spine Trauma Study Group, is both a scoring and a classification system. The system is based on three injury categories that are independently critical and complementary in helping determine and manage spine injury: (a) injury morphology, (b) integrity of the PLC, and (c) neurologic status of the patient (11). Within each category, subgroups are arranged from least to most significant, with a numeric value assigned to each injury pattern. Point values from the three main injury categories are totaled to provide a comprehensive severity score (Table 1). The TLICS helps identify injury features that are important in predicting biomechanical and neurologic spinal stability, thereby facilitating appropriate treatment recommendations (11). Injury Morphology One distinguishing feature of the TLICS is its emphasis on injury morphology rather than the mechanism of injury, a criterion used by earlier classification systems. Retrospective inference of injury mechanism from imaging findings can be controversial and variable. Various mechanisms can lead to similar injury patterns, and retrospective inference of injury mechanism based on imaging findings may result in systematic errors (18). The use of different descriptors in radiology reports can be confusing to spine surgeons and radiologists. The TLICS uses straightforward morphologic descriptions based on findings at radiography, CT, or MR imaging (Fig 4). Compression injuries are defined at imaging as a visible loss of vertebral body height or disruption of the vertebral endplate (19). Less severe compression injuries involve only the anterior portion of the vertebral body. Increased force results in burst fractures, which involve the posterior vertebral body with varying degrees of retropulsion. These injuries usually are caused by axial loading or lateral flexion. In TLICS injury morphology scoring, compression injury receives 1 point and burst fracture receives 2 points. Compression fracture with a coronal Table 1 The TLICS with Its Subcategories and Scoring Injury Category Point Value Injury morphology Compression 1 Burst 2 Translation or rotation 3 Distraction 4 PLC status Intact 0 Injury suspected or indeterminate 2 Injured 3 Neurologic status Intact 0 Nerve root involvement 2 Spinal cord or conus medullaris injury Incomplete 3 Complete 2 Cauda equina syndrome 3 Source. Reference 11. plane deformity of more than 15 is assigned a score of 2 points (3). Translation injuries (3 points) are defined at imaging as a horizontal displacement or rotation of one vertebral body with respect to another. These injuries result from torsional and shear forces and are characterized by rotation of the spinous processes, unilateral or bilateral facet fracture-dislocation, and vertebral subluxation (11). Anteroposterior or sagittal translational instability is best seen on lateral radiographs or sagittal CT or MR images, while instability in the mediolateral or coronal plane is best seen on anteroposterior radiographs and coronal CT images. Distraction injuries (4 points) are identified at imaging as anatomic dissociation along the vertical axis and can occur through the anterior and posterior supporting ligaments, the anterior and posterior osseous elements, or a combination of both. If more than one injury morphology exists, the single injury with the largest score is used. If multiple levels of injury are involved, each injury is assessed independently (11).

5 RG Volume 33 Number 7 Khurana et al 2035 Figure 4. Computer-generated 3D images show the four TLICS injury morphology categories: compression fracture (1 point) (a), compression with burst fracture (2 points) (b), translation or rotation injury (3 points) (c), and distraction injury (4 points) (d). Figure 5. Compression fracture with signs of PLC injury in two patients. (a) Sagittal CT image shows a directly visualized compression fracture with facet uncovering (arrows). (b) Axial CT image shows PLC disruption inferred by empty ( naked ) facets (arrows). PLC Integrity The PLC serves as the posterior tension band of the spinal column and protects the spine from excessive flexion, rotation, translation, and distraction. PLC integrity is emphasized in the TLICS. Once disrupted, the injured segment of the PLC usually requires surgical intervention because of its poor healing potential. Without surgery, an injured PLC can result in kyphotic progression and subsequent vertebral collapse (2). PLC integrity is categorized in the TLICS as intact, indeterminate, or disrupted. Assessment can be made with radiographs or CT or MR images. Disruption of the PLC is inferred on radiographs or CT images that show splaying of the spinous processes (widening of the interspinous space), avulsion fracture of the superior or inferior aspects of contiguous spinous processes, widening of the facet joints, empty ( naked ) facet joints, perched or dislocated facet joints, or vertebral body translation or rotation (Fig 5) (11,20).

6 2036 November-December 2013 radiographics.rsna.org Figure 6. Mild superior endplate compression fracture of T12 with an intact PLC. Sagittal T1- weighted (a) and axial T2-weighted (b) MR images show the supraspinous ligament (white arrow), interspinous ligament (black arrow), and ligamentum flavum (arrowhead) as continuous dark lines, with no findings of line discontinuity or T2-weighted signal hyperintensity that would suggest PLC injury. Unlike CT, MR imaging allows direct visualization of the PLC and thus is considered the imaging standard of reference for detecting PLC injury. Each component of the PLC requires individual analysis on MR images. The ligamentum flavum and supraspinous ligament are best seen on sagittal T1- or T2-weighted MR images as low-signal-intensity continuous black stripes (Fig 6). The interspinous ligaments are best evaluated with sagittal fluid-sensitive MR imaging that includes short inversion time inversion-recovery (STIR) or fat-saturated T2-weighted sequences (21,22). Axial fat-saturated T2-weighted MR images should be scrutinized for facet capsular edema or fluid. The most reliable signs of PLC injury are disruption of the low-signal-intensity black stripe on sagittal T1- or T2-weighted MR images, a finding that indicates a supraspinous ligament or ligamentum flavum tear, and fluid in the facet capsules or edema in the interspinous region on fluid-sensitive MR images, findings that reflect a capsular or interspinous ligament injury, respectively (23). An intact PLC is assigned a score of 0 points on the TLICS, and definite ligamentous injury is allocated 3 points. Isolated edema without clear ligament disruption is considered an indeterminate finding and is given a score of 2. A recent prospective analysis of MR imaging accuracy in diagnosis of traumatic PLC injuries has reported overall sensitivity and specificity of 91% and 100% respectively, with 100% accuracy in diagnosis of surgical fractures (24). MR imaging accuracy has been reported to be higher for detecting supraspinous ligament and ligamentum flavum injuries, where the grading is typically either intact or disrupted, and slightly lower for interspinous ligament and facet capsular injuries, which often fall into the indeterminate category because they may include a finding of edema without clear disruption (25). Earlier studies (26) have reported an overestimation of PLC injuries at MR imaging compared with subsequent surgical findings, and as a result, spine surgeons have used bone threshold parameters for reliability. However, with the exception of findings of significant vertebral body translation or interspinous widening, osseous findings such as a loss of vertebral body height and kyphosis have been found to be unreliable in assessing PLC integrity because of the inverse relationship between osseous destruction and ligamentous injury (27). Patients with severe osseous destruction may have less risk for PLC injury because the vertebral injury dissipates energy, thereby sparing adjacent soft tissues. Conversely, patients with a significant translation or rotation injury and less vertebral fragmentation may have a higher risk for PLC injury. The PLC must be directly assessed at MR imaging regardless of the severity of vertebral body injury seen at CT (28).

7 RG Volume 33 Number 7 Khurana et al 2037 Figure 7. Thoracic spine injury in a 17-year-old woman after a mechanical fall. (a) Sagittal CT image shows a compression fracture with predominant involvement of the anterior column (arrow), resultant kyphotic curvature (dotted line), and mild fanning of the spinous processes at the level of injury. (b) Sagittal CT image of the lateral vertebral bodies shows facet perching (arrow) with articular facet fracture, findings suggestive of a significant flexion component to the injury. (c, d) Sagittal T1-weighted (c) and STIR (d) MR images at the same level as a and b show disruption of the supraspinous ligament (black arrow) and ligamentum flavum (white arrow). Edema (arrowhead in d) in the posterior soft tissues and interspinous ligament is better visualized on the STIR image and illustrates the severity of the PLC injury. Compression and distraction injury morphologies make up a mechanistic continuum based on the magnitude of the flexion component of the injury force. A greater flexion component increases the risk for a destabilizing PLC injury. Compression with mild flexion results in relatively uniform height loss in the anterior and middle columns and minimizes the risk for a distraction injury to the PLC (Movie 3). An increased flexion component results in predominant height loss in the anterior column with relative height preservation in the middle column, a condition that exacerbates the distraction force on the PLC and results in destabilization (Fig 7; see also Movie 4).

8 2038 November-December 2013 radiographics.rsna.org Figure 8. Flexion injury of L1 in a 44-year-old man. (a, b) Sagittal T1-weighted (a) and STIR (b) MR images show avulsion of the posterior margin of the inferior endplate (arrowhead) and minimal anterior column compression (* in a). Fanning of the spinous processes (bracket in a) and disruption of the dark lines of the supraspinous ligament (black arrows in a) and ligamentum flavum (white arrows) are seen. Complete disruption of the interspinous ligament is shown (black arrow in b). (c) Axial T2-weighted MR image at the same level as a and b shows hemorrhage and edema throughout the PLC and no identifiable ligamentum flavum in the expected location (arrow), a finding indicative of disruption with retraction. Flexion-distraction mechanism and PLC injury should also be suspected if a superior or inferior posterior endplate fracture is seen because this likely reflects an avulsion fracture from the comparatively strong annulus fibrosus of the intervertebral disk (Fig 8; see also Movie 5) (10,29). PLC injuries can occur in this setting with minimal kyphosis or vertebral body height loss, a fact that further underscores the importance of MR imaging in assessing fracture stability. Neurologic Status The patient s neurologic status is a critical indicator of the degree of spinal column injury. The TLICS defines five categories of neurologic status based on deficit severity and the patient s recovery potential. Intact neurologic status at clinical examination is assigned a score of 0 points. Nerve root injury or complete spinal cord injury is allocated 2 points. Incomplete spinal cord injury or cauda equina syndrome is assigned 3 points because patients with this type of injury may receive greater potential benefit from surgical decompression than patients with complete spinal cord injury or no initial neurologic injury (3). Although clinical neurologic status cannot be directly determined at imaging, a cord or nerve root injury identified on MR images (Fig 9) should be included in the imaging report. Osseous retropulsion (Movie 6) or canal effacement may be evident on radiographs and CT or MR images and should be reported with the percentage of spinal canal narrowing. The anterior vertebral body compression percentage is the percentage of anterior vertebral body compression with respect to the average height of the anterior vertebral bodies immediately cephalad and caudad

9 RG Volume 33 Number 7 Khurana et al 2039 Figure 9. Thoracolumbar spine injury in a 38-year-old man. (a) Sagittal CT image shows a burst fracture of L1 (arrow) with fragment retropulsion into the spinal canal. (b, c) Sagittal (b) and axial (c) T2-weighted MR images show bone retropulsion with near-complete obliteration of the spinal canal (white arrow) and associated signal intensity change within the cord at a level superior to the injury (arrowhead in b). Disruption of the ligamentum flavum (black arrow) is also seen, a finding indicative of severe PLC injury. Complete cord injury was verified clinically, and a combined anterior and posterior surgical approach was used for repair. to the injury level (30,31). Retropulsion is the distance of a line drawn between the posterior margins of the adjacent vertebral bodies and the most posterior margin of the bone fragment. The distance between the posterior canal border and the anterior canal border represents the sagittal canal diameter. The posterior canal border is the convergence of the superior margins of the left and right laminae at the midline of the spinous process. The anterior canal border is the posterior extent of the retropulsed midvertebral body. The percentage of spinal canal compromise is calcu- lated using the following formula: a = (1 - x/y) 100, where a = percentage of spinal canal compromise, x = midsagittal diameter of the spinal canal at the level of injury, and y = mean of the midsagittal diameter of the spinal canal one segment above and one segment below the level of injury (32). Treatment Approach Although several classification systems have been developed to assess thoracolumbar spine injury, spine instability remains a controversial and poorly understood topic. The TLICS addresses three different categories of spine stability: (a) immediate mechanical stability, suggested by injury morphology; (b) long-term

10 2040 November-December 2013 radiographics.rsna.org Table 2 TLICS Treatment Guidelines for Spine Injury TLICS Score Treatment Recommendation 0 3 Nonsurgical 4 Nonsurgical or surgical 5 Surgical Source. Reference 11. stability, indicated by PLC status; and (c) neurologic stability, indicated by the presence or absence of a neurologic deficit. These categories form the basis of the TLICS and enable practical and clinically relevant assessment of spine stability. The TLICS total score helps surgeons evaluate injury severity and guides decision making about surgical versus nonsurgical management (Table 2). A TLICS total score of 3 or lower generally indicates nonsurgical management with brace immobilization and active patient mobilization. A score of 5 or higher warrants surgical intervention with deformity correction, neurologic decompression if necessary, and stabilization. A score of 4 indicates an intermediate zone where surgical or nonsurgical treatment may be equally appropriate (2). Treatment of burst fracture, especially in the absence of a neurologic deficit, is one of the most controversial areas of spine injury management (33). Osseous retropulsion alone does not imply neurologic injury or indicate a need for surgical decompression (18). Thoracic spine injury with retropulsion may cause significant neurologic injury because the spinal canal in the thoracic area is narrow and blood supply to the cord is sparse. In contrast, lumbar spine fracture may result in marked displacement of the cauda equina but no neurologic deficit because of the wider canal and cord termination near L1. A highly comminuted vertebral body fracture without internal fixation is more likely to deform under physiologic loading (34). This type of injury also may require short-segment posterior fixation and anterior fusion or long-segment posterior fixation. In the absence of a neurologic deficit, PLC integrity should be confirmed at MR imaging, especially if conservative management of burst fracture is planned (27). In addition to helping determine the need for surgical intervention, the TLICS can help guide the surgical approach. The surgical approach should be based primarily on the patient s neurologic status and the integrity of the PLC (Table 3). Patients with incomplete spinal cord injury with anterior compression will usually require an anterior surgical approach (Fig 10a, 10b), while patients with an injured PLC will require posterior surgical stabilization (Fig 10c, 10d). An anterior surgical approach allows more predictable and complete decompression of the neural elements, avoids damage to the posterior stabilizing structures, and reduces the risk of iatrogenic injury from posterior-approach manipulation of the dural sac (35). Patients with both a neurologic deficit and an injured PLC often require a combined anterior and posterior surgical approach (Fig 10e, 10f). Application of the TLICS: Clinical Examples Four patients with thoracolumbar spine trauma are described to demonstrate use of the TLICS with CT and MR imaging studies. Patient 1 A 21-year-old woman presented with back pain after a motor vehicle collision in which she was an unrestrained passenger in the middle seat. CT and MR imaging findings are shown in Figure 11. The patient s TLICS subscores were as follows: injury morphology (burst) = 2, PLC integrity (indeterminate) = 2, and neurologic status (normal) = 0. The patient s total TLICS score was 4. The injury was classified as burst injury with indeterminate PLC status. A posteriorapproach surgical repair was planned because of concern for PLC injury. At surgery, the interspinous ligament was noted to be injured and posterior-approach fusion was performed at T12- L1 and L1-L2.

11 RG Volume 33 Number 7 Khurana et al 2041 Figure 10. Compression fracture of L1. (a, b) In one patient, sagittal T1-weighted MR image (a) shows vertebral body compression and fragment retropulsion into the spinal canal but no clear PLC disruption. Postoperative lateral radiograph (b) shows the anterior (anterolateral) surgical approach used. (c, d) In another patient, sagittal T1-weighted MR image (c) shows complete disruption of the PLC but minimal vertebral body compression and no significant retropulsion. Lateral radiograph (d) shows the posterior surgical approach used. (e, f) In a third patient, sagittal T1-weighted MR image (e) shows significant vertebral body compression, fragment retropulsion, and PLC disruption. Lateral radiograph (f) shows the combined anterior and posterior surgical approach used. The anterior approach included a vertebral body implant cage, lateral body plate, and screw fusion. The posterior approach included a posterior rod and pedicle screw fusion. Table 3 Surgical Approach Guidelines Based on Neurologic Status and PLC Integrity Surgical Approach by PLC Status Neurologic Status Neurologically intact or nerve root injury Incomplete cord injury Complete cord injury Intact PLC Posterior Anterior Anterior or posterior Disrupted PLC Posterior Combined Combined or posterior

12 2042 November-December 2013 radiographics.rsna.org Figure 11. Compression burst fracture in a 21-year-old woman who was an unrestrained passenger in a motor vehicle collision. (a c) Sagittal CT image (a) and sagittal T2-weighted (b) and STIR (c) MR images show a fracture of L1 (white arrow) with significant fragment retropulsion but no cord or conus medullaris signal intensity abnormality. There is mild soft-tissue edema (arrowhead in c) and edema in the supraspinous and interspinous ligaments (black arrow in b and c) without definite ligament disruption. The ligamentum flavum appears intact. (d) Axial T2-weighted MR image shows a mild degree of impression on the thecal sac at the level of injury (arrow). The injury was classified as a burst fracture with indeterminate PLC status, and a posterior surgical approach was chosen because of clinical instability. At surgery, the interspinous ligament was found to be injured. Patient 2 A 21-year-old man presented with multiple injuries and lower extremity paralysis after a highspeed motor vehicle collision in which he was an unrestrained driver. CT and MR imaging findings are shown in Figure 12. The patient s TLICS subscores were as follows: injury morphology (translation) = 3, PLC (disrupted) = 3, and neurologic status (cord injury) = 3. The patient s total TLICS score was 9 (surgical treatment). The patient underwent posterior-approach open reduction and stabilization. Patient 3 A 29-year-old man presented with complete paralysis after he collided with a telephone pole while driving a motorcycle. CT and MR imaging findings are shown in Figure 13.

13 RG Volume 33 Number 7 Khurana et al 2043 Figure 12. Anterior translation injury in a 21-year-old man who was an unrestrained driver in a motor vehicle collision. Sagittal CT (a) and T2-weighted MR (b) images show a translation injury of T12 and L1 with secondary flexion. There is prominent widening of the interspinous space (bracket in a) and an annulus avulsion fracture of the inferior endplate of T12 (white arrow). Severe cord compression with signal intensity change (black arrow in b) and disruption of the supraspinous ligament (black arrowhead in b) and ligamentum flavum (white arrowhead in b) are seen. The patient underwent posterior-approach open reduction and stabilization. Figure 13. Distraction injury in a 29-year-old man after a motorcycle collision. Sagittal CT image (a) and sagittal STIR (b) and axial T2-weighted (c) MR images show a distraction injury of T10 (white arrow in a) with fracture line extension through the middle and posterior columns and subsequent distraction of the posterior element fracture fragments. Disruption of the ligamentum flavum (arrowhead in b), interspinous ligament (white arrow in b and c), and supraspinous ligament (black arrow in b and c) is seen. The patient underwent posterior-approach surgical repair.

14 2044 November-December 2013 radiographics.rsna.org Figure 14. Thoracic spine injury in a 17-yearold girl who was an unrestrained passenger in a motor vehicle collision. Coronal CT image (a) and sagittal (b) and axial (c) T2-weighted MR images show a lateral translation injury of T11 and T12 with lateral vertebral body overlap and marginal fractures (arrows in a), lateral canal compression with T11 nerve root injury (white arrow in b and c), and ligamentum flavum disruption (black arrow in b and c). The patient underwent posterior-approach surgical repair. The patient s TLICS system subscores were as follows: injury morphology (distraction) = 4, PLC (disrupted) = 3, and neurologic status (paralysis) = 2. The patient s total TLICS score was 9 (surgical treatment). The patient underwent posteriorapproach open reduction and stabilization. Patient 4 A 17-year-old girl presented with right-sided radiculopathy after a motor vehicle collision in which she was an unrestrained backseat passenger. CT and MR imaging findings are shown in Figure 14. The patient s TLICS subscores were as follows: injury morphology (translation) = 3, PLC (disrupted) = 3, and neurologic status (nerve root injury) = 2. The total TLICS score was 8 (surgical treatment). The patient underwent posteriorapproach open reduction and posterolateral fusion graft stabilization from T9-T10 through L2-L3. Reporting Thoracolumbar Injuries Because numerous classification systems are used to describe thoracolumbar injuries, radiology reports frequently contain inconsistent terminology, which can lead to miscommunication or delayed communication of clinically relevant findings. The TLICS provides the basis for more accurate radiology reports and more effective communication with spine surgeons. The TLICS is simple and easy to apply with fewer categories to remember. Significant information can be conveyed in one succinct paragraph. Table 4 provides a checklist based on the TLICS to help radiologists report spine injuries. Each injury is defined using one of the four TLICS injury morphology patterns, and a basic description of injury features and extent includes the degree of comminution, percentage of vertebral height loss, retropulsion distance, percentage of canal compromise, and other contiguous or noncontiguous vertebral injuries. PLC integrity is predicted based on CT findings of facet joint widening, interspinous distance widening, spinous process avulsion fracture, and vertebral body or facet subluxation or dislocation. At MR imaging, the patient s PLC status should be reported as injured, intact, or indeterminate. Findings of potential spinal cord injury, epidural hematoma, and other ligamentous or disk injuries are also recorded. Although the radiology report may

15 RG Volume 33 Number 7 Khurana et al 2045 Table 4 Checklist for Reporting Spine Injury at CT and MR Imaging CT Injury morphology Primary injury pattern (compression, burst, translation, flexion-distraction) Basic morphologic description of lesion Vertebral height loss (approximate percentage) Retropulsion with central spinal canal narrowing (approximate percentage) Other contiguous or noncontiguous injuries Degree of kyphosis PLC injury predictors Facet joint widening Interspinous distance widening Spinous process avulsion fracture Vertebral body subluxation or dislocation MR imaging Osseous injuries (similar to injury morphology noted at CT) Soft-tissue injuries PLC status (intact, indeterminate, or disrupted) Supraspinous ligament Ligamentum flavum Interspinous ligaments Facet capsule Disks Anterior and posterior longitudinal ligaments Neurologic injuries Spinal cord and conus medullaris Cauda equina Nerve root injury Epidural hematoma include the TLICS total score if there is clear imaging evidence of neurologic injury, generally the report will not include the total score if the patient s clinical neurologic status is unknown. Conclusion The TLICS is the most comprehensive and recent thoracolumbar injury grading scale to combine injury morphology, assessment of mechanical stability relevant to the PLC, and neurologic status into a system capable of guiding injury management. The TLICS provides the best available predictor of surgical versus nonsurgical management. Radiologists should use the key components of the TLICS to analyze, evaluate, and report spine injuries and to help guide decisions about surgical management. Disclosures of Conflicts of Interest. C.M.B.: Related financial activities: none. Other financial activities: consultant for Harvard Clinical Research Institute and United Health Care, royalties from Wolters Kluwer. M.H.: Related financial activities: none. Other financial activities: board member for North American Spine, consultant for Harvard Clinical Research Institute. References 1. Looby S, Flanders A. Spine trauma. Radiol Clin North Am 2011;49(1): Rihn JA, Anderson DT, Harris E, et al. A review of the TLICS system: a novel, user-friendly thoracolumbar trauma classification system. Acta Orthop 2008;79(4): Sethi MK, Schoenfeld AJ, Bono CM, Harris MB. The evolution of thoracolumbar injury classification systems. Spine J 2009;9(9): Ferguson RL, Allen BL Jr. A mechanistic classification of thoracolumbar spine fractures. Clin Orthop Relat Res 1984;189: McAfee PC, Yuan HA, Fredrickson BE, Lubicky JP. The value of computed tomography in thoracolumbar fractures: an analysis of one hundred consecutive cases and a new classification. J Bone Joint Surg Am 1983;65(4): Bono CM, Vaccaro AR, Hurlbert RJ, et al. Validating a newly proposed classification system for thoracolumbar spine trauma: looking to the future of the thoracolumbar injury classification and severity score. J Orthop Trauma 2006;20(8): Denis F. The three column spine and its significance in the classification of acute thoracolumbar spinal injuries. Spine 1983;8(8):

16 2046 November-December 2013 radiographics.rsna.org 8. Joaquim AF, Fernandes YB, Cavalcante RA, Fragoso RM, Honorato DC, Patel AA. Evaluation of the thoracolumbar injury classification system in thoracic and lumbar spinal trauma. Spine 2011;36(1): Oner FC, Ramos LM, Simmermacher RK, et al. Classification of thoracic and lumbar spine fractures: problems of reproducibility a study of 53 patients using CT and MRI. Eur Spine J 2002;11(3): Magerl F, Aebi M, Gertzbein SD, Harms J, Nazarian S. A comprehensive classification of thoracic and lumbar injuries. Eur Spine J 1994;3(4): Vaccaro AR, Lehman RA Jr, Hurlbert RJ, et al. A new classification of thoracolumbar injuries: the importance of injury morphology, the integrity of the posterior ligamentous complex, and neurologic status. Spine 2005;30(20): Garbuz DS, Masri BA, Esdaile J, Duncan CP. Classification systems in orthopaedics. J Am Acad Orthop Surg 2002;10(4): Audigé L, Bhandari M, Hanson B, Kellam J. A concept for the validation of fracture classifications. J Orthop Trauma 2005;19(6): Nordin M, Weiner S. Biomechanics of the lumbar spine. In: Nordin M, Fankel V, eds. Basic biomechanics of the musculoskeletal system. 3rd ed. Philadelphia, Pa: Lippincott Williams & Wilkins, 2001; Leone A, Guglielmi G, Cassar-Pullicino VN, Bonomo L. Lumbar intervertebral instability: a review. Radiology 2007;245(1): Asmussen E, Klausen K. Form and function of the erect human spine. Clin Orthop 1962;25(25): Whitesides TE Jr. Traumatic kyphosis of the thoracolumbar spine. Clin Orthop Relat Res 1977;128: Oner FC, Wood KB, Smith JS, Shaffrey CI. Therapeutic decision making in thoracolumbar spine trauma. Spine 2010;35(suppl 21):S235 S Patel AA, Dailey A, Brodke DS, et al. Thoracolumbar spine trauma classification: the Thoracolumbar Injury Classification and Severity Score system and case examples. J Neurosurg Spine 2009;10(3): Harris MB, Stelly MV, Villarraga ML, Schroeder AC, Thomas KA. Modeling of the naked facet sign in the thoracolumbar spine. J Spinal Disord 2001;14 (3): Haba H, Taneichi H, Kotani Y, et al. Diagnostic accuracy of magnetic resonance imaging for detecting posterior ligamentous complex injury associated with thoracic and lumbar fractures. J Neurosurg 2003;99(suppl 1):S20 S Lee JY, Vaccaro AR, Schweitzer KM Jr, et al. Assessment of injury to the thoracolumbar posterior ligamentous complex in the setting of normal-appearing plain radiography. Spine J 2007;7(4): Pizones J, Zúñiga L, Sánchez-Mariscal F, Alvarez P, Gómez-Rice A, Izquierdo E. MRI study of posttraumatic incompetence of posterior ligamentous complex: importance of the supraspinous ligament prospective study of 74 traumatic fractures. Eur Spine J 2012;21(11): Pizones J, Sánchez-Mariscal F, Zúñiga L, Alvarez P, Izquierdo E. Prospective analysis of magnetic resonance imaging accuracy in diagnosing traumatic injuries of the posterior ligamentous complex of the thoracolumbar spine. Spine 2012 Oct 19. [Epub ahead of print] 25. Pizones J, Izquierdo E, Alvarez P, et al. Impact of magnetic resonance imaging on decision making for thoracolumbar traumatic fracture diagnosis and treatment. Eur Spine J 2011;20(suppl 3):S390 S Vaccaro AR, Lee JY, Schweitzer KM Jr, et al. Assessment of injury to the posterior ligamentous complex in thoracolumbar spine trauma. Spine J 2006;6(5): Radcliff K, Su BW, Kepler CK, et al. Correlation of posterior ligamentous complex injury and neurological injury to loss of vertebral body height, kyphosis, and canal compromise. Spine 2012;37(13): Radcliff K, Kepler CK, Rubin TA, et al. Does the load-sharing classification predict ligamentous injury, neurological injury, and the need for surgery in patients with thoracolumbar burst fractures? Clinical article. J Neurosurg Spine 2012;16(6): Fredrickson BE, Edwards WT, Rauschning W, Bayley JC, Yuan HA. Vertebral burst fractures: an experimental, morphologic, and radiographic study. Spine 1992;17(9): Keynan O, Fisher CG, Vaccaro A, et al. Radiographic measurement parameters in thoracolumbar fractures: a systematic review and consensus statement of the Spine Trauma Study Group. Spine 2006; 31(5):E156 E Vaccaro AR, Nachwalter RS, Klein GR, Sewards JM, Albert TJ, Garfin SR. The significance of thoracolumbar spinal canal size in spinal cord injury patients. Spine 2001;26(4): Mohanty SP, Bhat NS, Abraham R, Ishwara Keerthi C. Neurological deficit and canal compromise in thoracolumbar and lumbar burst fractures. J Orthop Surg (Hong Kong) 2008;16(1): Rajasekaran S. Thoracolumbar burst fractures without neurological deficit: the role for conservative treatment. Eur Spine J 2010;19(suppl 1):S40 S Wood K, Buttermann G, Mehbod A, Garvey T, Jhanjee R, Sechriest V. Operative compared with nonoperative treatment of a thoracolumbar burst fracture without neurological deficit: a prospective, randomized study. J Bone Joint Surg Am 2003;85- A(5): Wood KB, Khanna G, Vaccaro AR, Arnold PM, Harris MB, Mehbod AA. Assessment of two thoracolumbar fracture classification systems as used by multiple surgeons. J Bone Joint Surg Am 2005;87 (7): This journal-based SA-CME activity has been approved for AMA PRA Category 1 Credit TM. See

17 Teaching Points November-December Issue 2013 Traumatic Thoracolumbar Spine Injuries: What the Spine Surgeon Wants to Know Bharti Khurana, MD Scott E. Sheehan, MD, MS Aaron Sodickson, MD, PhD Christopher M. Bono, MD Mitchel B. Harris, MD RadioGraphics 2013; 33: Published online /rg Content Codes: Page 2034 The TLICS, developed by the Spine Trauma Study Group, is both a scoring and a classification system. The system is based on three injury categories that are independently critical and complementary in helping determine and manage spine injury: (a) injury morphology, (b) integrity of the PLC, and (c) neurologic status of the patient. Page 2035 Disruption of the PLC is inferred on radiographs or CT images that show splaying of the spinous processes (widening of the interspinous space), avulsion fracture of the superior or inferior aspects of contiguous spinous processes, widening of the facet joints, empty ( naked ) facet joints, perched or dislocated facet joints, or vertebral body translation or rotation. Page 2038 Flexion-distraction mechanism and PLC injury should also be suspected if a superior or inferior posterior endplate fracture is seen because this likely reflects an avulsion fracture from the comparatively strong annulus fibrosus of the intervertebral disk. PLC injuries can occur in this setting with minimal kyphosis or vertebral body height loss, a fact that further underscores the importance of MR imaging in assessing fracture stability. Page 2040 A TLICS total score of 3 or lower generally indicates nonsurgical management with brace immobilization and active patient mobilization. A score of 5 or higher warrants surgical intervention with deformity correction, neurologic decompression if necessary, and stabilization. A score of 4 indicates an intermediate zone where surgical or nonsurgical treatment may be equally appropriate. Page 2044 Each injury is defined using one of the four TLICS injury morphology patterns, and a basic description of injury features and extent includes the degree of comminution, percentage of vertebral height loss, retropulsion distance, percentage of canal compromise, and other contiguous or noncontiguous vertebral injuries. PLC integrity is predicted based on CT findings of facet joint widening, interspinous distance widening, spinous process avulsion fracture, and vertebral body or facet subluxation or dislocation. At MR imaging, the patient s PLC status should be reported as injured, intact, or indeterminate. Findings of potential spinal cord injury, epidural hematoma, and other ligamentous or disk injuries are also recorded.