Figure 1
High-velocity frontal collision, and the boy was a seat-belt restrained back seat passenger. At the time of the impact, the seat-belt was under the arm instead of over the shoulder, while the lap-belt was in place.
Flexion-distraction seat-belt injury
The patient was admitted following a road traffic accident (RTA). The accident was a high-velocity frontal collision,and the boy was a seat-belt restrained back seat passenger. Unfortunately, at the time of the impact, the seat-belt was under the arm instead of over the shoulder, while the lap-belt was in place.
When admitted,the GCS was 15/15. Lacerations were present over the left forehead. There was bruising in the peri-umbilical region,with diffuse guarding and rigidity over the mid-abdomen. When the patient was log-rolled, it was noticed that there was a boggy haematoma measuring 10x12 cm over D10-L2 vertebrae. There was normal sensation,tone,power and reflexes in both lower limbs. Perianal sensation was unaltered.
Although the patient went straight to CT and initial abdominal films were not performed,the scout view from the CT can be taken as the straight abdomen film. There is a suspicion of altered alignment at L2, although it is difficult to identify a definite fracture line. Axial images from the CT demonstrate diffuse swelling of the perivertebral muscles in the region of the upper lumbar spine, with disruption of the posterior elements of L2.
Multiplanar reconstructions in the sagittal and coronal planes clearly show a transverse fracture passing through the body of L2 and extending through the pedicles into the spinous process. There is anterior wedging of the body, with separation of the fractured elements posteriorly. The features are classical of flexion-distraction injury associated with seat-belts, with the typical picture of a Chance fracture.
An MRI was also performed,confirming these findings and demonstrating abnormal signal in L1,L3 and L4 vertebrae in addition to L2, consistent with bruising. The conus and cauda equina were intact, correlating with clinical findings.
Although the patient went straight to CT and initial abdominal films were not performed,the scout view from the CT can be taken as the straight abdomen film. There is a suspicion of altered alignment at L2, although it is difficult to identify a definite fracture line. Axial images from the CT demonstrate diffuse swelling of the perivertebral muscles in the region of the upper lumbar spine, with disruption of the posterior elements of L2.
Multiplanar reconstructions in the sagittal and coronal planes clearly show a transverse fracture passing through the body of L2 and extending through the pedicles into the spinous process. There is anterior wedging of the body, with separation of the fractured elements posteriorly. The features are classical of flexion-distraction injury associated with seat-belts, with the typical picture of a Chance fracture.
An MRI was also performed,confirming these findings and demonstrating abnormal signal in L1,L3 and L4 vertebrae in addition to L2, consistent with bruising. The conus and cauda equina were intact, correlating with clinical findings.
The 3 column theory of spinal stability put forward by Denis in 1984 postulates that the spinal column can be subdivided into :
(1) an ANTERIOR column,consisting of anterior longitudinal ligament, anterior half of the annulus fibrosus and the vertebral body,
(2)a MIDDLE column,consisting of the posterior longitudinal ligament, posterior half of the annulus fibrosus and the vertebral body, and
(3) a POSTERIOR column,consisting of the neural arch and the intervening ligaments.
The middle column acts as a fulcrum between the other two and it's integrity is essential for stability of the spine. Hence, flexion and extension injuries, with intact middle columns, tend to be stable, while flexion-distraction injuries' such as the one described, burst ,translocation and dislocation injuries are classed as unstable, with inherent risk of neural damage (1).
In a seat-belt injury, a flexion-distraction force is at work, rotating the lumbar vertebral body about a transverse axis that passes through the nucleus pulposus. There is unequal distribution of stresses, with the anterior segment of the vertebral body subjected to x4 times the compression force on the ineterspinous ligaments(2). The extreme forward flexion due to the seat-belt produces tension stress on both the bodies and the neural arches, leading to laceration of the posterior ligaments and distraction of the fractured fragments. Chance fractures,which are horizontal splits through the bodies, transverse processes, pedicles, laminae and spinous processes, are a specific subtype of such injuries.
The case exemplifies the above, demonstrating a Chance type of fracture right through the body, transverse processes, pedicles and neural arch of L2 vertebra, at the site where one would expect the lap belt to cross anteriorly. There is distraction of the posterior elements with ligamentous disruption. The fracture is unstable, although the MRI confirms that there is no immediate neural damage.
Such compression and horizontally oriented fractures of the thoracolumbar spine are difficult to detect on axial CT(3), unless displacement is large. But good quality Multiplanar Reconstructions from Multidetector CT enable such injuries to be easily seen and described and the images are often of great value to the clinician.
(1) an ANTERIOR column,consisting of anterior longitudinal ligament, anterior half of the annulus fibrosus and the vertebral body,
(2)a MIDDLE column,consisting of the posterior longitudinal ligament, posterior half of the annulus fibrosus and the vertebral body, and
(3) a POSTERIOR column,consisting of the neural arch and the intervening ligaments.
The middle column acts as a fulcrum between the other two and it's integrity is essential for stability of the spine. Hence, flexion and extension injuries, with intact middle columns, tend to be stable, while flexion-distraction injuries' such as the one described, burst ,translocation and dislocation injuries are classed as unstable, with inherent risk of neural damage (1).
In a seat-belt injury, a flexion-distraction force is at work, rotating the lumbar vertebral body about a transverse axis that passes through the nucleus pulposus. There is unequal distribution of stresses, with the anterior segment of the vertebral body subjected to x4 times the compression force on the ineterspinous ligaments(2). The extreme forward flexion due to the seat-belt produces tension stress on both the bodies and the neural arches, leading to laceration of the posterior ligaments and distraction of the fractured fragments. Chance fractures,which are horizontal splits through the bodies, transverse processes, pedicles, laminae and spinous processes, are a specific subtype of such injuries.
The case exemplifies the above, demonstrating a Chance type of fracture right through the body, transverse processes, pedicles and neural arch of L2 vertebra, at the site where one would expect the lap belt to cross anteriorly. There is distraction of the posterior elements with ligamentous disruption. The fracture is unstable, although the MRI confirms that there is no immediate neural damage.
Such compression and horizontally oriented fractures of the thoracolumbar spine are difficult to detect on axial CT(3), unless displacement is large. But good quality Multiplanar Reconstructions from Multidetector CT enable such injuries to be easily seen and described and the images are often of great value to the clinician.
References
[1]
Carty H, Brunelle F, Shaw D, Kendall B.<br>Imaging in children<br>
Churchill Livingstone, 1995, pp 1740-41.
[2] Caffey J.<br> Paediatric X-ray Diagnosis. Seventh edition <br>Mosby, 1993: pp 1614-15.
[3] Haaga J, Alfidi R.<br>Computed Tomography of the whole body.Second edition<br> Mosby, 1995, Vol 1 pp 566.
Case information
| URL: | https://www.eurorad.org/case/2640 |
| DOI: | 10.1594/EURORAD/CASE.2640 |
| ISSN: | 1563-4086 |
Figure 2
Figure 3
Figure 4
Figure 5
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
