Pediatric Thoracic Spine Injuries: A Single-Institution Experience

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1 Pediatric Imaging Review Junewick et al. Pediatric Thoracic Spine Injuries Pediatric Imaging Review Joseph J. Junewick 1,2,3 Heather L. orders 1,2,3 lan T. Davis 4,5 Junewick JJ, orders HL, Davis T Keywords: distraction fracture, flexion-distraction injury, pediatric thoracic spine fracture DOI: /JR Received October 29, 2013; accepted after revision December 12, Department of Radiology, Helen DeVos Children s Hospital, 100 Michigan ve, Grand Rapids, MI ddress correspondence to H. L. orders (heatherborders@gmail.com). 2 Department of Radiology, Michigan State University, College of Human Medicine, Grand Rapids, MI. 3 dvanced Radiology Services, Grand Rapids, MI. 4 Research Department, Grand Rapids Medical Education Partners, Grand Rapids, MI. 5 Department of Surgery, Michigan State University, College of Human Medicine, Grand Rapids, MI. This article is available for credit. JR 2014; 203: X/14/ merican Roentgen Ray Society Pediatric Thoracic Spine Injuries: Single-Institution Experience OJECTIVE. The objective of our study was to determine the incidence of various fractures of the thoracic spine in pediatric patients. CONCLUSION. Simple compression and process-only fractures were the most common types of fractures and all other fracture types were infrequent. Distraction injury was unexpectedly more common in the nonjunctional thoracic spine than in the junctional thoracic spine. S pine trauma is often designated by the following anatomic levels: cervical, thoracic, lumbar (nonjunctional), and junctional (craniocervical, cervicothoracic, and thoracolumbar). Different types and distributions of injuries are seen in pediatric patients compared with adults because of anatomic and biomechanical differences. The pediatric spine is more flexible and is not completely ossified compared with the adult spine, and the muscles of pediatric patients are typically weaker than those of adults. dditionally, the ligaments of pediatric patients are more elastic and the facet joints are more shallow [1 4]. These differences decrease as a patient approaches skeletal maturity. The purpose of this study was to determine the incidence of various injury patterns of the thoracic vertebrae in infants and children. Materials and Methods Institutional review board approval was given to review the records of all pediatric patients (< 18 years old) identified in the Helen DeVos Children s Hospital (level 1 trauma designation) Trauma Registry with thoracic spine fractures related to blunt trauma between July 2002 and June single radiologist reviewed all imaging studies available in the PCS to characterize the thoracic spine fractures. The imaging studies were characterized as dedicated CT or MRI of the thoracic spine (or both); CT of the chest; CT or MRI of the cervical spine only (or both) or CT or MRI of the cervical spine and lumbar spine with partial inclusion of the thoracic spine (or both); CT of the abdomen with partial inclusion of the thoracic spine; or radiography. Injuries were characterized as process-only fractures, which were defined as spinous or transverse process fractures with no compromise of the spinal canal or loss of column integrity; simple anterior compression fracture, loss of less than 50% of the anterior vertebral body height with an intact posterior column; unstable anterior compression fracture, any loss of vertebral body height with facet disruption or an interspinous ligament or posterior ligamentous complex injury; lateral compression fracture, predominant deformity of the right or left side of the vertebral body; burst fracture, comminuted body fracture with fragment displaced into the spinal canal; fracture-dislocation, fractures at two contiguous levels with vertebral malalignment leading to compromise of the spinal canal; hyperextensiondistraction, anterior vertebral body corner fracture with evidence of posterior column impaction or an anterior ligamentous injury; hyperflexion-distraction, transverse splitting of the posterior elements with anterior column compression; or other. Patient age and sex and the mechanism of injury were recorded for each patient. The imaging records and electronic medical records were reviewed for patient age and sex; the mechanism of injury; concomitant injuries of the chest to the thoracic great vessels, airways, diaphragm, and sternum (pulmonary contusion, pleural injuries, and rib fractures were not tabulated); neurologic deficit, which was categorized as none, paraplegia, or other; and the presence or absence of remote injuries (i.e., brain, cervical spine, lumbar spine, abdominopelvic viscera). Summary statistics were calculated for the data. Quantitative data were expressed as means ± SDs, whereas nominal data were expressed as percentages. Comparisons involving nominal data were performed using the chi-square test, Fisher JR:203, September

2 Junewick et al. exact test, or McNemar test. Comparisons involving quantitative data were performed using either the paired or unpaired Student t test, as appropriate. Significance was assessed at p < Results total of 104 pediatric patients were identified with thoracic spine fractures in the Trauma Registry. Thirty patients were excluded: two for fractures related to gunshot injury, two for thoracic cord injury without fracture, one for underlying osteogenesis imperfecta, and 25 for unsubstantiated fractures by imaging available in the PCS. The study cohort was composed of the remaining 74 patients, 45 boys and 29 girls; the average age of this cohort was 13.0 ± 4.1 years. Fortytwo subjects had sustained injuries by motor vehicle crash; 12, by fall; eight, by bicycle; two, as pedestrians hit by a motor vehicle; and 10, by another mechanism. No sports-related thoracic spine fractures were recorded during the time period of this study. The thoracic spine was evaluated by dedicated spinal CT or MRI (or both) in 45 patients; CT of the chest in 20 patients, nine of whom underwent additional partial imaging of the thoracic spine by dedicated CT or MRI (or both) of the cervical spine only or of the cervical spine and lumbar spine; partial inclusion on CT or MRI (or both) of the cervical spine only or of the cervical spine and lumbar spine in eight patients; and conventional radiography in one patient. In these 74 patients, 249 thoracic levels had fractures. There were 211 injuries that involved the nonjunctional thoracic spine (T2 T10), whereas 38 involved the junctional thoracic spine (T1, T11, or T12). Fortyfour patients had nonjunctional injuries alone, 14 had junctional injuries alone, and 16 had combined junctional and nonjunctional injuries. The most common fractures were simple compression fractures (66.7%) and processonly fractures (26.5%). ll other fracture categories had a frequency of 2.4% or less. Fracture types and incidence by vertebral level are illustrated in Figure 1. Fracture was more common in older patients: 14.5% of the fractures were in patients 0 8 years old, 45% in patients 9 14 years old, and 40.5% in patients years old. The fracture type was compared with the method of injury (motor vehicle crash, yes vs no) and the presence of thoracic injury, brain injury, and abdominal visceral injury (Tables 1 and 2). Only one comparison achieved a p value < 0.05: greater proportion of subjects with brain injury had process-only fractures than subjects without brain injury. However, given the very large number of comparisons made, the significance of this finding must be viewed with caution. TLE 1: Fracture Type by Whether Patient Was Injured in Motor Vehicle Crash or Whether Thoracic Injury Was Present Fracture Type Motor Vehicle Crash Thoracic Injury Yes a No a p Yes a No a p Simple compression 27/42 (64.3) 24/32 (75.0) /6 (66.7) 47/68 (69.1) > 0.99 Unstable compression b 4/42 (9.5) 1/32 (3.1) /6 (16.7) 4/68 (5.9) 0.35 Lateral compression 2/42 (4.8) 1/32 (3.1) > /6 (0.0) 3/68 (4.4) > 0.99 urst fracture 2/42 (4.8) 1/32 (3.1) > /6 (0.0) 3/68 (4.4) > 0.99 Hyperextension-distraction 2/42 (4.8) 0/32 (0.0) /6 (16.7) 1/68 (1.5) 0.16 Hyperflexion-distraction 2/42 (4.8) 4/32 (12.5) /6 (16.7) 5/68 (7.4) 0.41 Fracture-dislocation 2/42 (4.8) 0/32 (0.0) /6 (0.0) 2/68 (2.9) > 0.99 Process-only fracture 15/42 (35.7) 12/32 (37.5) > /6 (50.0) 24/68 (35.3) 0.66 Other 1/42 (2.4) 0/32 (0.0) > /6 (0.0) 1/68 (1.5) > 0.99 a Data are presented as no. of patients/total no. of patients (%). b ny loss of vertebral body height with facet dispuption or an interspinous ligament or posterior ligamentous complex injury. TLE 2: Fracture Type by Presence of rain Injury or bdominal Visceral Injury Fracture Type rain Injury bdominal Visceral Injury Yes a No a p Yes a No a p Simple compression 7/14 (50.0) 44/60 (73.3) /18 (55.6) 41/56 (73.2) 0.16 Unstable compression b 0/14 (0.0) 5/60 (8.3) /18 (5.6) 4/56 (7.1) > 0.99 Lateral compression 0/14 (0.0) 3/60 (5.0) > /18 (0.0) 3/56 (5.4) > 0.99 urst fracture 0/14 (0.0) 3/60 (5.0) > /18 (5.6) 2/56 (3.6) > 0.99 Hyperextension-distraction 0/14 (0.0) 2/60 (3.3) > /18 (11.1) 0/56 (0.0) 0.06 Hyperflexion-distraction 1/14 (7.1) 5/60 (8.3) > /18 (5.6) 5/56 (8.9) > 0.99 Fracture-dislocation 0/14 (0.0) 2/60 (3.3) > /18 (0.0) 2/56 (3.6) > 0.99 Process-only fracture 9/14 (64.3) 18/60 (30.0) /18 (50.0) 18/56 (32.1) 0.17 Other 0/14 (0.0) 1/60 (1.7) > /18 (0.0) 1/56 (1.8) > 0.99 a Data are presented as no. of patients/total no. of patients (%). b ny loss of vertebral body height with facet dispuption or an interspinous ligament or posterior ligamentous complex injury. 650 JR:203, September 2014

3 Pediatric Thoracic Spine Injuries Fracture types were also compared based on junctional (T1, T11, or T12) versus nonjunctional (T2 T10) segments of the thoracic spine. Simple compression, unstable compression, hyperflexion-distraction, and processonly fractures were significantly more prevalent in the nonjunctional thoracic segments than in the junctional thoracic segments (p < 0.05). Compression fractures were more often multiple in the nonjunctional versus the junctional thoracic spine (compression fractures per patient: mean, 2.0 ± 2.3 vs 0.2 ± 0.5, respectively; p < 0.001). The analyses were rerun, comparing the proportion of spinal elements involved in the fracture for the junctional (T1, T11, and T12) versus nonjunctional (T2 T10) thoracic spine. In this analysis, simple compression (p < 0.01), unstable compression (p = 0.01), and hyperflexion-distraction fractures (p = 0.02) were significantly more prevalent in the nonjunctional thoracic segments than in the junctional thoracic segments. Discussion Thoracic vertebrae are defined by the presence of ribs, but there are anatomic and biomechanical variations at different levels of the thoracic spine and also differences in the pediatric spine compared with the adult spine. The first thoracic vertebra has cervical features, with long transverse processes and a long horizontal spinous process. Coronally oriented intervertebral facets, inferiorly directed spinous processes, and rib stabilization with the sternum characterize T2 T10. The T11 and T12 vertebrae have lumbar features, and their ribs do not extend to the anterior chest wall. With trauma, the thoracic spine should be considered in three segments: junctional (cervicothoracic [C7 T1] and thoracolumbar [T11 L1]) and nonjunctional (T2 T10). Fractures of the pediatric spine are uncommon injuries [1 5]. Three main mechanisms of injury are described in the spine: flexion with or without compression, distraction, and shear [5]. Some injuries are a combination of multiple mechanisms, vectors, and types of force. Detailed descriptions of the various types of fractures occurring in the pediatric thoracic spine are difficult to find in the literature. Compression fractures are most commonly reported, followed by process-only fractures and then unstable fractures [1, 2]. Many injuries in the thoracic spine are related to hyperflexion because of the kyphotic posture. The initial mechanical failure in hyperflexion injuries involves the anterosuperior endplate (Fig. 2). Greater disruption of the vertebral body occurs with increased or more vertically focused force, giving rise to severe compression (Fig. 3) and burst fractures (Fig. 4). Simple compression injuries in the nonjunctional spine were most often multiple and contiguous in this series; the relative flexibility of the pediatric spine may allow force to be dispersed over multiple levels, which minimizes the effect on a single level [1], and a more flexible intervertebral disk may also allow force dispersion over multiple levels [5]. Process-only fractures (Fig. 5) are usually the result of ligamentous and muscular avulsion, although these fractures occasionally occur from impaction with adjacent osseous structures. In our patient population, simple compression fractures and process-only fractures were most commonly seen. Most unstable spinal injuries are the result of severe or multiple sequential or complex vector forces. Flexion with distraction is the mechanism of Chance injuries (Fig. 6), whereas extension with distraction leads to the lumberjack injury (Fig. 7). Fracture-dislocations ( ripped can injuries) (Fig. 8) are the result of multidirectional forces with distraction. Lateral compression fractures (Fig. 9) are usually associated with contralateral distraction injuries and are often a component of severe spinal injury. Unstable fractures were less common in our patient population. Junctional versus nonjunctional anatomy is often emphasized in trauma. Different injury patterns and different frequencies are reported in the junctional thoracic spine (cervicothoracic and thoracolumbar) compared with the nonjunctional thoracic spine. In this series, the nonjunctional thoracic spine was injured more often than the junctional thoracic spine. Distraction injuries are noted for their thoracolumbar junction predominance (related to increased junctional spine mobility) and association with neurologic sequelae, visceral injuries, and vascular disruption [3, 6 10]. In this series, most distraction injuries occurred in the nonjunctional thoracic spine. The relative predominance in the nonjunctional thoracic spine suggests that distraction injuries are more common in this region in the pediatric patient than previously thought, although there are a few other reports of nonjunctional flexion-distraction fractures [6, 10, 11]. The nonjunctional location may be related to a higher fulcrum (i.e., shoulder or chest restraint rather than a seat belt or lap belt) at the time of injury or the relatively larger upper body to lower body ratio in pediatric patients [1, 6]. Visceral, vascular, and neurologic sequelae were less commonly encountered in our series, which is possibly related to the nonjunctional predominance; the thoracic cage may limit the degree of distraction, redistribute forces, or afford greater protection to the spinal cord and thoracic viscera. In summary, most of the results of this series are similar to other reports in the literature. Our finding that simple compression fractures and unstable compression fractures were more common in the nonjunctional spine was an expected finding. Similarly, compression fractures and process-only fractures being the most common types of fractures in this series were also an expected finding based on other studies in the literature [1, 2]. However, distraction injuries occurring more frequently in the nonjunctional spine was unexpected, and this finding emphasizes the fact that pediatric patients should be carefully evaluated for this type of injury. There was not a significant increase in thoracic or abdominal visceral injuries in patients with nonjunctional thoracic spine distraction injuries in this series in distinction to thoracolumbar spine distraction injuries. The limitations of this study include its retrospective nature and the fact that all data are from a single institution and the imaging protocols were not uniform. The results of future multiinstitution studies would be interesting to assess for similar incidence of findings. Ideally, all patients would have undergone dedicated CT and MRI examinations of the thoracic spine; in our series, 29 of 74 patients underwent imaging that was not optimal, which may have contributed to the nondiagnosis of fractures. Other reports in the literature have similar limitations with regard to incomplete imaging; it is important to keep a low threshold for dedicated thoracic spine imaging in patients with the appropriate injury mechanism or clinical symptoms. cknowledgments We thank Ellen Junewick and the Helen DeVos Children s Hospital Trauma Registry for their assistance in the preparation of this manuscript. JR:203, September

4 References 1. Carreon LY, Glassman SD, Campbell MJ. Pediatric spine fractures: a review of 137 hospital admissions. J Spinal Disord Tech 2004; 17: Hegenbarth R, Ebel KD. Roentgen findings in fractures of the vertebral column in childhood. Pediatr Radiol 1976; 5: Cirak, Zeigfeld S, Knight VM, et al. Spinal injuries in children. J Pediatr Surg 2004; 39: Hofbauer M, Jaindl M, Höchtl LL, et al. Spine injury in polytraumatized pediatric patients: characteristics and experience from a level I trauma Fig. 1 ar chart shows types of fractures and incidence at each thoracic spine level. Fig year-old girl who was ejected from backseat during rollover motor vehicle crash. Sagittal STIR MR image shows multilevel simple, minor compression fractures, most obvious of which is at T4. center over two decades. J Trauma cute Care Junewick et al. Surg 2012; 73: Clark P, Letts M. Trauma to the thoracic and lumbar spine in the adolescent. Can J Surg 2001; 44: Davis JM, eall DP, Lastine C, Sweet C, Wolff J, Wu D. Chance fracture of the upper thoracic spine. JR 2004; 183: nderson P, Henley M, Rivara F, Maier R. Flexion distraction and chance injuries to the thoracolumbar spine. J Orthop Trauma 1991; 5: ernstein MP, Mirvis SE, Shanmuganathan K. Thoracic Spine Level T12 T11 T10 T9 T8 T7 T6 T5 T4 T3 T2 T No. of Patients Chance-type fractures of the thoracolumbar spine: imaging analysis in 53 patients. JR 2006; 187: Dennis HH, Tak HH. review of thoracolumbar spine fracture classifications. J Orthop Trauma 2011; 1: Sander L, Laurer H, El Saman, et al. Chance fracture of the upper thoracic spine in a child. Eur J Trauma Emerg Surg 2009; 35: Dhall SS, Tumialán LM, Mummaneni PV. Chance fracture of the second thoracic vertebra: case illustration. J Trauma 2006; 60:922 Simple compression Unstable compression and facet subluxation or dislocation Lateral compression urst Hyperextension-distraction Hyperflexion-distraction Fracture-dislocation Process-only fracture Other Fig year-old boy who was involved in motor vehicle crash. and, Sagittal T1-weighted FLIR () and STIR () images show severe compression of anterior T6 vertebral body, disruption of posterior ligamentous complex (arrow, ), interspinous edema, and paraspinous soft-tissue edema. lso note minor anterior T5 vertebral body compression and microtrabecular edema subjacent to superior endplates of T3 and T JR:203, September 2014

5 Pediatric Thoracic Spine Injuries Fig year-old boy who was restrained backseat passenger in rollover motor vehicle crash. Sagittal reformatted CT image shows severe compression deformity of T5; obliteration of T4 T5 disk space; and retropulsion of posterosuperior corner of vertebral body into spinal canal, which is consistent with burst fracture. Fig year-old girl who fell approximately 20 ft (6 m) from roof onto concrete. xial CT image shows nondisplaced left transverse process fracture and pulmonary contusions. C D Fig. 6 Flexion-distraction fracture in 13-year-old boy with lower extremity paralysis after all-terrain vehicle crash. D, Sagittal reformatted CT images show kyphotic posture of spine, compression of T9 vertebral body, and transverse distracting fracture of neural arch. JR:203, September

6 Junewick et al. Fig. 7 Hyperextension-distraction fracture in 3-year-old girl involved in motor vehicle crash. and, Sagittal reformatted CT images show neutral attitude of spine. Fracture transversely splits posterior elements of T3 and extends anteriorly through posterosuperior corner of T3 vertebral body. Triangular fracture fragment of anteroinferior aspect of T2 vertebral body represents hyperextension teardrop injury. C, Sagittal MR fast-relaxation fast spin-echo T2-weighted image confirms osseous injuries, posterior ligamentous complex disruption (arrow), and extensive injury at craniocervical junction. Fig year-old boy with altered sensation in lower extremities after all-terrain vehicle injury. C, xial (), coronal (), and volume-rendered 3D (C) CT images show fracture-dislocation at T12. C C 654 JR:203, September 2014

7 Pediatric Thoracic Spine Injuries Fig year-old girl involved in motor vehicle crash. Coronal reformatted CT image shows right lateral compression fracture of T5 and left lateral compression of T6 with extensive paraspinal hematoma; thoracostomy tube is present on right. FOR YOUR INFORMTION This article is available for CME and Self-ssessment (S-CME) credit that satisfies Part II requirements for maintenance of certification (MOC). To access the examination for this article, follow the prompts associated with the online version of the article. JR:203, September