Overview This report details the clinical course of a patient who presented following a high-energy collision with a ligamentous Chance injury at T11-T12. The patient was initially evaluated with 1 mm thin-cut CT imaging – which revealed subtle bony fractures suggestive of a mechanism of distraction. He was then evaluated with upright films in thoracolumbosacral orthosis (TLSO) – read as effectively absence of malalignment or progressive kyphosis. Because the potential for ligamentous disruption on initial CT imaging went unrecognized, MRI was not initially obtained. Following a protracted recovery complicated by intraabdominal injuries, the patient developed sudden onset of neurologic deficit following mobilization on post-injury day 11. MRI of the spine was obtained and demonstrated an unstable ligamentous Chance injury at T11-T12 with new evidence of compression of the neural elements at this level. To the authors’ knowledge, this case report is the first to present definitive evidence that upright films are unreliable in the detection of pathologic instability in ligamentous Chance injuries. The radiologic presentation of Chance injuries is described and an extremely low threshold for obtaining MRI of the spine when distraction injury is suspected is advocated.

Neurological Deterioration Secondary to Unrecognized Instability on CT Imaging and Upright Films in a Ligamentous Chance Fracture

Jonathan A. Forbes, MD¹ ∙ Michael A. Stoker² ∙ Pete E. Konrad, MD¹

Contact: Jonathan Forbes, MD. E-mail This e-mail address is being protected from spambots. You need JavaScript enabled to view it . 

Citation: Forbes JA, Stoker MA, Konrad PE. Neurological deterioration secondary to unrecognized instability on CT imaging and upright films in a ligamentous Chance fracture. J Surg Radiol. 2011 Jan 1;2(1). Download PDF J Surg Rad January 2011 A05.pdf 4332 Kb Received: August 31, 2010; Accepted: September 23, 2010; Published: September 25, 2010 Copyright: © 2010 Surgisphere Corporation. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Contents - Introduction - Case Report - Discussion - Conclusion - References

Introduction

Neurological deterioration secondary to unrecognized spinal instability (SI) is a significant source of potentially correctible morbidity in the trauma population. Studies indicate that approximately 0.025% of all trauma patients are affected by neurologic injury relating to unrecognized SI – including 0.21% of all patients with spine injuries.1 Three root causes have been proposed as proximal etiologies behind the failure to appropriately identify SI. In a study of 24 patients who suffered neurological deterioration secondary to missed instability by Levi et al., insufficient imaging was the root cause in 14 (58%) patients, misread imaging in 8 (33%) patients, and poor quality imaging in 2 (8%) patients.1

Patients who arrive to medical centers following high-energy collisions receive a CT traumagram – which includes axial CT imaging of the cervical, thoracic, and lumbar spine with image spacing of 5 mm or less.2 At the majority of level I trauma centers, this imaging is comprised of thin-cut axial imaging of 2.5 mm or less and includes coronal and sagittal reconstructions. MRI is obtained on a selective basis in patients who are felt to be at increased risk of SI given the appearance of the injury on CT imaging. The practice of obtaining upright plain films has been advocated in all patients with spinal injuries who are treated non-operatively, as deformity sometimes progresses to unacceptable levels with the physiological loads associated with an upright posture.3

In the past, traumatic injuries of the spine have been subdivided using the AO Spine Classification System based on underlying mechanism into compressive, flexion-distraction, and multidirectional fraction-dislocation injuries.4 At our institution, MRI is not routinely obtained in patients who present with injuries felt to be secondary to a mechanism of compression (e.g., anterior compression, superior endplate, burst fractures, etc.). In these patients, upright films are obtained in individuals whose injuries are felt to be amenable to non-operative therapy (e.g., bracing) following initial CT imaging. If the patient exhibits evidence of significant progressive kyphosis when upright, the posterior ligamentous complex is assumed to be compromised and surgical reduction and stabilization is indicated. If the patient fails to exhibit evidence of progressive kyphosis when upright, the posterior ligamentous complex is assumed to be physiologically viable and conservative management is recommended. In contrast to the diagnostic work-up for compressive injuries, patients with flexion-distraction injuries are often recommended for MRI of the spine soon after arrival. This recommendation relates to an association of these injuries with unstable ligamentous disruption – occasionally in the setting of subtle findings on CT imaging.1 While the radiologic features of ligamentous Chance injuries on CT imaging can be indistinct, the diagnosis of multidirectional fracture/dislocation injuries with associated instability is usually readily apparent.5 Consequently, many patients with fracture-dislocations injuries proceed to the OR for stabilization following initial CT imaging.

There is a paucity of information in the literature regarding the use of upright films in lieu of MRI in the detection of spinal instability. To the authors’ knowledge, this case report is the first of its kind to present evidence that upright films are unreliable in the detection of pathologic instability in ligamentous Chance injuries – where compromise of the bony anterior column is often minimal. The radiologic presentation of Chance fractures is described and an extremely low threshold for obtaining MRI of the spine when distraction injury is suspected is advocated.

Case Report

History and Examination

A 27 year-old male presented to the trauma center following an unrestrained high-speed motor vehicle collision notable for ejection. The patient was intubated on the scene and noted to be hemodynamically unstable en route to the hospital. His blood pressure eventually stabilized with fluids and vasopressors. Following arrival, he was evaluated and treated for multiple injuries visualized on CT traumagram, including complex orthopedic injuries of the left femur and right acetabulum in addition to various intraabdominal injuries. Immediately following initial evaluation and imaging, he was taken urgently to the operating room for exploratory laparotomy and hepatorrhapy, splenectomy, and right nephrectomy. A neurosurgery consultation was placed for spinal injuries noted on thin-cut (1 mm) CT imaging with reconstructions that included multiple transverse process and spinous process fractures of T10 through L4 in addition to extension of transverse process fractures to involve the pedicle at T10 and T11 (Figure 1). Fractures of the inferior-posterior endplate of T11 and the anterior superior endplate of T12 were also noted.

Figure 1. A. Sagittal CT image that includes subaxial cervical, thoracic, and lumbar spine. Thin arrow indicates anterior superior endplate fracture of T12. B-D. Axial cuts which include the T11, T12, and L1 vertebral bodies. In (B) the T10-T11 facet junction is visible, with no evidence of facet widening. In (C), diastasis of the right inferior articular process of T11 from the right superior articular process of T12 is illustrated by the thick arrow. E-H. Magnified consecutive sagittal images of the thoracolumbar junction are seen, proceeding from right to left. Fracture of the anterior superior endplate of T12 (indicative of avulsion of the annulus from the body secondary to distraction mechanism) is visible. In (E) diastasis of the right inferior articular process of T11 from the right superior articular process of T12 – illustrated by the arrowhead – suggests possible instability at this level. In contrast, as visualized in (H), no widening of the junction of the left inferior articular process of T11 with the left superior articular process of T12 is present.

Initial evaluation in the trauma ICU following surgery was limited secondary to the heavy sedation and paralytics required for his open abdomen. The patient returned to the OR for removal of packing and delayed primary closure of fascia approximately 6 hours following his initial procedure. On examination the following day, he was noted to be following commands weakly. Soft tissue swelling around the posterior thoracolumbar elements was noted on exam, with some apparent tenderness to palpation. Upright plain films of the thoracic and lumbar spine obtained on post-injury day (PID) 1 in a thoracolumbosacral orthosis (TLSO) failed to reveal any evidence of progressive kyphosis or malalignment (Figure 2) and the patient was cleared to mobilize as tolerated with brace when greater than 30 degrees. On PID3, the patient was taken to the OR for treatment of his orthopedic injuries. He continued to convalesce and was mobilized for the first time with physical therapy on PID9. This activity was associated with extreme pain in his back. On PID11, the patient developed new lower extremity weakness (ASIA C), again while being mobilized with the physical therapy. Neurosurgery was reconsulted emergently and MRI of the spine demonstrated a distractive injury with new instability and cord impingement at T11-12 consistent with a ligamentous chance injury (Figure 3).

Figure 2. Upright AP and lateral plain films of the thoracic and lumbar spine obtained on post-injury day (PID) 1 in a thoracolumbosacral orthosis (TLSO) failed to reveal evidence of progressive kyphosis or malalignment.

Figure 3. MRI of the spine demonstrates new evidence of instability and cord impingement at T11-12 consistent with a ligamentous chance injury.

Operation and Post-Operative Course

The patient was taken urgently to the operating room for a T11-T12 laminectomy with T10-L1 posterior spinal fusion. Post-operative films revealed good realignment (Figure 4). The patient’s bilateral paresis of the lower extremities improved over the ensuing weeks. He was discharged to rehab on PID16/POD5. At follow-up reevaluation at 6 weeks his lower extremity weakness was noted to have resolved entirely.

Figure 4. Post-operative upright films in brace after T11-T12 laminectomy with T10-L1 posterior spinal fusion.

Discussion

Flexion-distraction injuries were virtually unknown prior to routine use of the lap seat belt during motor vehicle collisions and were first formally described in 1948 by G.Q. Chance.6 Since this time, these injuries have alternatively been referred to as Chance and/or seat-belt type injuries. Flexion-distraction injuries result from a primary force vector acting along an axis of rotation anterior in location to the middle column.7 In Denis’ sentinel paper in 1983, he described four subtypes of spinal column injury based on fracture morphology: compression fractures, burst fractures, seat-belt type fractures, and fracture-dislocations.8 Each fracture could be described in terms of associated damage to the 3 columns (anterior, middle, posterior) of the spine. Seat-belt type fractures, also known as flexion-distraction injuries, were observed to result after failure of the middle and posterior columns in distraction.8 In these injuries, the anterior column may fail in tension or compression depending on whether the instantaneous axis of rotation is anterior to the anterior spinal column.7

In Magerl’s (e.g., AO Spine) comprehensive injury classification system published in 1994 (Figure 5), spinal column injuries were differentiated based on mechanism.4 Type A injuries were related to compression, Type B injuries were related to distraction, and Type C injuries were related to multidirectional injury, often with translation. Based on individual characteristics, fractures could be divided into further subcategories. Regarding injuries suffered secondary to a mechanism of distraction, B1 injuries primarily involve underlying ligamentous damage while B2 injuries involve damage to the bony elements. B3 injuries involve predominant distraction anteriorly. While these respective subcategories can be divided into additional subclassifications, further analysis is beyond the scope of this report. The patient in this case would be described as having a seat-belt type fracture using the Denis classification, and an AO Spine B1 (predominantly ligamentous flexion-distraction injury) using the Magerl classification.

Figure 5. The three injuries types of the AO Spine Classification are demonstrated. (A) Type A involves compression injury. (B) Type B involves distraction injury. (C) Type C involves multidirection injury with shear and/or translation. Images courtesy of M. Aebi, V. Arlet, J.K. Webb, AO-Manual of Spine Surgery, Vol. I, 2008. Thieme Publisher, Stuttgart.11

In patients who present to trauma centers across the U.S. following high-energy collisions, the current gold standard for detection of injuries to the spinal column involves thin-cut CT axial imaging with coronal and sagittal reconstructions. The sensitivity of this imaging modality regarding the detection of bony injury approaches 100%.9 Even more important than the diagnosis of bony injury, however, is detection of pathologic instability. The potential to miss SI can be analyzed in regards to Denis’ classification of spinal column injuries and largely relates to the potential of the injury complex in question to result in occult ligamentous disruption. Compression injuries are readily detected on CT imaging and are almost universally stable.4 Burst fractures similarly are routinely identified on CT imaging. Focal kyphosis > 30 degrees and/or loss of height >50% are suggestive of compromise of the posterior ligamentous complex (PLC) and instability in these fractures.10 When it is unclear on CT imaging as to whether true instability is present, upright films in unstable burst fractures often reveal progressive kyphosis under physiological loads (the films of another patient who presented following an MVC with a burst fracture with instability found on upright films can bee seen in Figure 6). At our institution, upright films are obtained for burst fractures felt to be amenable to non-operative therapy with bracing, based on findings on CT imaging. MRI in these patients is not routinely accomplished, as patients who demonstrate progressive kyphosis when upright require operative reduction and stabilization and patients who do not are considered to be stable and treated with bracing. It is notable that the routine use of MRI scans in all burst fractures to determine PLC integrity has been advocated by some authors.12 Other authors have questioned the clinical applicability of findings on MRI and have recommended against the routine use of MRI in patients with burst fractures because of a noted inability to influence management.13 Fracture-dislocation injuries often involve significant damage to the bony elements that is readily evident on CT imaging. These injuries are associated with instability and the highest incidence of neurologic deficit.4 While fracture-dislocation injuries are often readily detected following standard CT traumagram, cases of missed diagnoses and secondary neurologic injury have been reported.1

Flexion-distraction injuries are a unique group of spinal column injuries associated with significant instability and, not infrequently, subtle radiologic findings on CT imaging.14 The indistinct findings on initial plain film and CT imaging occasionally lead to misdiagnosis and undetected spinal instability (refer to Table 1 for a list of all previously published case reports of delayed diagnosis of unstable, ligamentous [AO Spine B1] Chance-type injuries.). Flexion-distraction injuries have been noted to be associated with a lower incidence of neurologic deficit on presentation than fracture-dislocation injuries4 and are relatively infrequent – representing 5 to 15% of all thoracolumbar fractures.8, 15, 16 Past descriptions have further classified flexion-distraction injuries into bony or ligamentous subtypes. Intuitively speaking, bony flexion-distraction injuries would be expected to be detected on CT more readily than those of the ligamentous variety. While this may be true, the vast majority of ligamentous flexion-distraction injuries appear to be associated with some evidence of bony injury. This is typified by a case series of 53 patients with flexion-distraction injuries by Bernstein et al., where no patient was found to have a purely ligamentous injury without evidence of bony involvement.14 Another retrospective review by Groves et al. found that only 1 of 24 patients had a purely ligamentous injury.17 The pattern of bony involvement with predominantly ligamentous (B1) flexion-distraction injuries is important, as these features may represent the only discernible evidence of underlying injury and/or instability on initial CT imaging. Location of these fractures is the first such characteristic that deserves mention. In the retrospective review by Bernstein and colleagues, 78% of flexion-distraction injuries occurred between T12 and L2.14 Associated injuries are also relevant – 40% of patients who presented with this injury complex in the aforementioned study had associated intraabdominal injury. A handful of notable radiologic findings have been described in patients who present with this injury complex. The “dissolving pedicle sign” has been described in an estimated 76% of flexion-distraction injuries.14 This feature has been defined as a gradual loss of definition of the pedicles at the level of the fracture and is particularly suggestive of a bony (AO Spine B2) Chance-type fracture. Another feature known as the “naked facet sign” – representing uncovering of the articular facets secondary to distraction injury – was seen in 40% of patients in the case series by Bernstein et al.14 One additional radiologic finding – known as the “empty vertebral body sign” – was found 100%, or 53 of 53 patients of the aforementioned series. The specificity of this latter finding is unknown. In the review of 24 MRI scans by Groves et al., a loss of anterior vertebral body height secondary to compression or corner fracture was described in 83% of patients with flexion-distraction injuries and facet disruption was seen in 71% of patients.17

While ligamentous Chance injuries are often diagnosed on CT imaging, the high prevalence of subtle findings leads to the potential for misdiagnosis. In contrast, when MRI is obtained in these patients, the radiologic findings are unambiguous and allow for definitive assessment of discoligamentous instability. It is also worth noting that dynamic flexion and extension films have been reported to be accurate in delineating instability in this setting.18 Cases such as this one that involve neurological deterioration secondary to unrecognized spinal instability are useful to review so that future morbidity can be avoided. Regarding the radiologic features previously defined, the patient described in this case report did not exhibit the traditional definition of the dissolving pedicle sign. However, the small degree of distraction that was present did result in a slightly asymmetric presentation of the pedicles on axial imaging at the T11-T12 level (refer to Figure 1c). Furthermore, while a formal “naked facet sign” was not present, axial imaging and sagittal reconstructions did demonstrate some diastasis of the right T11-T12 facet joint (refer to Figures 1c, 1e, 1f). Despite formal absence of the two previously described radiologic features, the “empty vertebral body sign” was present in the patient described (see Figure 7). This finding was felt to be secondary to the mild degree of splaying of the spinous process at the T11-T12 level in conjunction with the fractured T12 spinous process. One additional noteworthy radiologic finding in the patient described was the fracture of the anterior-superior endplate of T12 – likely consistent with distraction of the annulus at this level with avulsion of the aforementioned region of endplate. The bony findings in this patient, although subtle, were strongly indicative of a distractive injury. Knowledge that this patient had suffered a severe intraabdominal injury should have raised the index of suspicion for a flexion-distraction injury. In patients who present with radiologic findings suggestive of distractive injury in the thoracolumbar spine, MRI is recommended to fully ascertain the degree of discoligamentous disruption and definitively evaluate for spinal instability.

Figure 6. Radiologic films of another patient who presented following a MVC with a L1 burst fracture. Sagittal (A) and axial (B) CT images of the fracture are visible. The thin arrow demonstrates the level of the L1 burst fracture in (A). Upright AP (C) and lateral (D) films demonstrated progressive kyphosis at L1 (arrow) indicative of disruption of the PLC. The patient required posterolateral fusion for stabilization. The PLC disruption was verified intra-operatively.

Figure 7. Inferior displacement of T12 spinous process results in a degree of interspinous widening and “empty vertebral body sign” on AP radiograph (arrow).

Conclusion

Upright films are unreliable in the detection of spinal instability in Chance fractures. When CT imaging reveals evidence suggestive of a mechanism of distraction in the thoracolumbar spine, a low threshold for obtaining MRI of the thoracic and lumbar spine is advocated. If MRI is contraindicated, the use of dynamic (flexion and extension) plain films to diagnose instability in this setting has been described.

Disclosure

The authors report no conflicts of interest concerning the materials or methods used in this study or the findings specified in this paper.

References

1. Levi AD, Hurlbert RJ, Anderson P, Fehlings M, Rampersaud R, Massicotte EM, France JC, Le Huec JC, Hedlund R, Arnold P: Neurologic deterioration secondary to unrecognized spinal instability following trauma--a multicenter study. Spine 31(4):451-8, 2006.
2. Mancini DJ, Burchard KW, Pekala JS: Optimal thoracic and lumbar spine imaging for trauma: are thoracic and lumbar spine reformats always indicated? J Trauma 69(1):119-21, 2010.
3. Benzel EC: Spine surgery: techniques, complication, avoidance, and management, ed 2. Philadelphia, PA, Elsevier Churchill Livingstone, 2005.
4. Magerl F, Aebi M, Gertzbein SD, Harms J, Nazarian S: A comprehensive classification of thoracic and lumbar injuries. Eur Spine J 3(4):184-201,1994.
5. Liljenqvist U, Halm H, Castro WH, Mommsen U: Thoracic fracture-dislocations without spinal cord injury: a case report and literature review. Eur Spine J 4(4):252-6, 1995.
6. Chance GQ: Note on a type of flexion fracture of the spine. Br J Radiol 21:452–453,1948.
7. Patel AA, Vaccaro AR: Thoracolumbar spine trauma classification. J Am Acad Orthop Surg 18(2):63-71, 2010.
8. Denis F: The three column spine and its significance in the classification of acute thoracolumbar spinal injuries. Spine 8(8):817-31, 1983.
9. Roos JE, Hilfiker P, Platz A, et al: MDCT in emergency radiology: is standardized chest or abdominal protocol sufficient for evaluation of thoracic and lumbar spine trauma. AJR Am J Roentgenol. 183: 959–968, 2004.
10. Heary RF, Kumar S: Decision-making in burst fractures of the thoracolumbar and lumbar spine. Indian J Orthop 41:268-76, 2007.
11. Aebi M, Arlet V, WebbJK: AO-Manual of Spine Surgery, Vol. I, 2008. Thieme Publisher, Stuttgart.
12. Petersilge CA, Pathria MN, Emery SE, Masaryk TJ: Thoracolumbar burst fractures: evaluation with MR imaging. Radiology 194:49-54, 1995.
13. Dai LY, Ding WG, Wang XY, Jiang LS, Jiang SD, Xu HZ: Assessment of ligamentous injury in patients with thoracolumbar burst fractures using MRI. J Trauma 66(6):1610-5, 2009.
14. Bernstein MP, Mirvis SE, Shanmuganathan K: Chance-type fractures of the thoracolumbar spine: imaging analysis in 53 patients. AJR Am J Roentgenol 187(4):859-68, 2006.
15. Gertzbein SD, Court-Brown CM: Flexion-distraction injuries of the lumbar spine: mechanisms of injury and classification. Clin Orthop Relat Res 227:52–60, 1988.
16. Gumley G, Taylor TKF, Ryan MD: Distraction fractures of the lumbar spine. J Bone Joint Surg Br 64B:520–525, 1982.
17. Groves CJ, Cassar-Pullicino VN, Tins BJ, Tyrrell PN, McCall IW: Chance-type flexion-distraction injuries in the thoracolumbar spine: MR imaging characteristics. Radiology 236(2):601-8, 2005.
18. Ceroni D, Mousny M, Lironi A, Kaelin A: Pediatric seatbelt injuries: unusual Chance's fracture associated with intra-abdominal lesions in a child. Eur Spine J 13(2):167-71, 2004.
19. Burdi M, Bono CM, Kauffman CP, Hoyt D, Garfin SR: Delayed diagnosis of a flexion-distraction (seat belt) injury in a patient with multiple abdominal injuries: a case report. Am J Orthop 37(1):44-6, 2008.
20. Keene JS, Lash EG, Kling TF Jr: Undetected posttraumatic instability of "stable" thoracolumbar fractures. J Orthop Trauma 2(3):202-11, 1988.
21. Smith MW, Reed JD, Facco R, Hlaing T, McGee A, Hicks BM, Aaland M: The reliability of nonreconstructed computerized tomographic scans of the abdomen and pelvis in detecting thoracolumbar spine injuries in blunt trauma patients with altered mental status. J Bone Joint Surg Am  91(10):2342-9, 2009.