Chance fracture

Trauma in a 31 yo F due to a motor vehicle collision (MVC) • Xray of the Week

Figure 1. What are the important findings on this CT scan. What is the diagnosis?

Figure 2. A,B. Sagittal reformatted CT images. C-E. Axial CT images

Images show horizontal fracture through the right lamina (orange arrows), right pedicle (green arrows) and left pedicle (red arrows). Fracture of the spinous process (blue arrows) is also present.

Discussion:

Chance fractures are horizontal spinal fractures that extend through the spinous process, pedicles, and vertebral body at the thoracolumbar junction [1]. They typically result from flexion-distraction injury of the spine and may be referred to as “seat belt fractures” because they can occur in motor vehicle collisions where rapid deceleration causes flexion of the spine over the seat belt [1]. This causes distraction of the middle and posterior elements of the spine [1].

Table 1. Francis Denis Spine Fracture Classification System Source: https://www.researchgate.net/figure/Column-involvement-in-major-Denis-fracture-types_tbl1_288817814

The Chance fracture is classified as an unstable flexion-distraction spinal injury according to the Francis Denis three-column concept (Table 1) because it involves two or more columns: a distraction-type injury of the middle and posterior columns; compression-type injury of the anterior column may also be present in some cases [1,2]. Chance fractures can be identified as pure osseous, pure ligamentous, or osteoligamentous [1,2].

Chance fractures are difficult to identify as they do not present with neurological deficits but can present with intra-abdominal injuries [1]. Delays in diagnosis can result in progressive kyphosis and pain, so early diagnosis is essential. Differential diagnosis includes burst fracture, compression fracture, and distraction injury [1,3].

Figure 3. Axial CT image demonstrating the seat belt sign in this patient with stranding in the subcutaneous fat of the abdominal wall (red arrows).

CT shows the horizontal fracture as well as vertebral body compression [1]. Stranding in the subcutaneous fat of the abdominal wall results in the “seat belt sign” on CT [1] (Fig. 3). CT also shows “dissolving pedicle,” which refers to the progressive decrease in pedicle definition from anterior to posterior [3]. On MRI, there may be a bright T2 signal signifying edema with low signal intensity fracture lines, intervertebral disc injury, and spinal cord edema [1]. Plain radiograph shows empty vertebral body sign, which results from displacement of the spinous processes [3]. Increased distance between the pedicles and facet joints on plain X-ray may also be seen in a Chance fracture [3].

Treatment includes immobilization with a stabilizing brace in patients without neurological deficits [1]. Surgical stabilization may be required in patients who have neurological deficits or damage to the posterior ligaments [1].

References:

1. Koay J, Davis DD, Hogg JP. Chance Fractures. In: StatPearls. Treasure Island (FL): StatPearls Publishing; December 2, 2020. https://pubmed.ncbi.nlm.nih.gov/30725611/

2. Raniga SB, Skalski MR, Kirwadi A, Menon VK, Al-Azri FH, Butt S. Thoracolumbar Spine Injury at CT: Trauma/Emergency Radiology. Radiographics. 2016;36(7):2234-2235. doi:10.1148/rg.2016160058

3. Bernstein MP, Mirvis SE, Shanmuganathan K. Chance-type fractures of the thoracolumbar spine: imaging analysis in 53 patients. AJR Am J Roentgenol. 2006;187(4):859-868. doi:10.2214/AJR.05.0145

Amara Ahmed is a medical student at the Florida State University College of Medicine. She serves on the executive board of the American Medical Women’s Association and Humanities and Medicine. She is also an editor of HEAL: Humanism Evolving through Arts and Literature, a creative arts journal at the medical school. Prior to attending medical school, she graduated summa cum laude from the Honors Medical Scholars program at Florida State University where she completed her undergraduate studies in exercise physiology, biology, and chemistry. In her free time, she enjoys reading, writing, and spending time with family and friends.

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Kevin M. Rice, MD is the president of Global Radiology CME

Dr. Rice is a radiologist with Renaissance Imaging Medical Associates and is currently the Vice Chief of Staff at Valley Presbyterian Hospital in Los Angeles, California. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015, Dr. Rice and Natalie Rice founded Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" Award for the Most Effective Radiology Educator.

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