Bilateral Facet Dislocation at C7-T1​

A 70-year-old female fell off her bed while changing a light bulb and complains of left shoulder pain. What is the diagnosis? • Xray of the Week

Figure 1. Non-contrast CT of the cervical spine. What is the diagnosis?

Figure 2. Non-contrast CT of the cervical spine (sagittal reconstructions): Bilateral facet dislocation at C7-T1 with anterior subluxation of C7 on T1. The inferior facets of C7 are locked anterior to the superior facets of T1 (yellow and green arrows), with anterior vertebral body translation present. There are associated fractures of C7 and T1 (red arrows).

Figure 2. Non-contrast axial CT of the cervical spine: Bilateral facet dislocation at C7-T1 with naked facet sign (green arrow) and reverse hamburger bun sign (red arrow).

Discussion

The cervicothoracic junction (C7–T1) represents a biomechanical transition between the mobile cervical spine and the rigid thoracic spine, making it particularly vulnerable to traumatic instability. Bilateral facet dislocation at this level is a highly unstable injury most commonly associated with high-energy trauma but may also occur after low-energy falls in elderly patients due to osteopenia and degenerative stiffness. [1] The injury involves both facets "jumping" anteriorly, disrupting ligamentous stability and risking cord compression.[2] Delayed diagnosis can occur due to poor visualization of C7-T1 on plain films, emphasizing the need for CT in suspected cases.[3] As seen in this case, "teardrop" fragment on C7 or T1 represents a highly unstable flexion-compression or flexion-distraction injury; it is not a minor avulsion and signifies severe ligamentous damage.[5]

Imaging Findings

CT is the imaging modality of choice for evaluating suspected cervicothoracic junction trauma, as plain radiographs frequently fail to visualize C7–T1 due to shoulder overlap. Multiplanar CT reformations are essential for assessing alignment, facet integrity, and associated fractures. [1]

• Key CT findings include:

• High-grade anterior translation of C7 relative to T1

• Bilateral jumped or locked facets with loss of normal facet articulation

• Widening of the interspinous distance indicating posterior ligamentous complex disruption

• Small anterior vertebral body fracture fragments at C7 and T1 consistent with flexion

• teardrop fractures

• Marked narrowing of the spinal canal at the C7–T1 level

• Axial CT images demonstrate bilateral reverse hamburger bun and naked facet signs, which are pathognomonic for facet dislocation. [2,3]

Differential Diagnosis

Traumatic bilateral facet dislocation must be distinguished from degenerative spondylolisthesis, which is common in geriatric patients but lacks joint capsule disruption and typically involves less than 4 mm of translation. Unilateral facet dislocation involves a rotational component and manifests as a "bow-tie" sign on lateral radiographs with less than 25% anterior translation. Isolated flexion teardrop fractures involve significant three-column injury but lack the mechanical "locking" of the facet joints seen in dislocations. Traumatic

dislocation is favored when there is facet joint disruption, significant translation, and associated ligamentous injury. [1]

Management and Prognosis

Bilateral facet dislocation at C7–T1 represents a surgical emergency due to profound instability and high risk of neurologic deterioration. Initial management includes cervical immobilization and urgent neurosurgical consultation. Most cases require operative fixation, often via posterior or combined anterior-posterior approaches. Prognosis depends largely on neurologic status at presentation. [1]

Key Learning Points

• C7–T1 injuries are frequently missed on plain radiographs

• Low-energy falls can cause severe cervical instability in elderly patients

• Reverse hamburger bun and naked facet signs are key CT indicators

• Anterior teardrop fractures signify severe ligamentous injury

• Early recognition and surgical management are critical

• Correlate with MRI for soft tissue/cord assessment.

References

1. Raniga SB, Menon V, Al Muzahmi KS, Butt S. MDCT of acute subaxial cervical spine trauma: a mechanism-based approach. Insights Imaging. 2014;5(3):321–338. doi: 10.1007/s13244-014-0311-y

2. Daffner SD, Daffner RH. Computed tomography diagnosis of facet dislocations: the hamburger bun and reverse hamburger bun signs. J Emerg Med. 2002;23(4):387–394. DOI: 10.1016/s0736-4679(02)00577-2

3. Lingawi SS. The naked facet sign. Radiology. 2001;219(2):366–367. DOI: 10.1148/radiology.219.2.r01ma06366

4. Kim KS, Chen HH, Russell EJ, Rogers LF. Flexion teardrop fracture of the cervical spine: radiographic characteristics. AJR Am J Roentgenol. 1989;152(2):319–326. DOI: 10.2214/ajr.152.2.319

5. Kim KS, Chen HH, Russell EJ, Rogers LF. Flexion teardrop fracture of the cervical spine: radiographic characteristics. AJR Am J Roentgenol. 1989;152(2):319-326. DOI: 10.2214/ajr.152.2.319

Nishad Kosaraju is a second-year osteopathic medical student (OMS-II) at the Edward Via College of Osteopathic Medicine–Carolinas Campus (VCOM-Carolinas). He has a strong interest in diagnostic imaging and interventional radiology, with particular enthusiasm for case-based learning and understanding how imaging directly informs clinical decision-making.

Nishad did his undergraduate education at UNC Chapel Hill, where he studied Exercise and Sports Science. Nishad enjoys contributing educational radiology cases that highlight classic imaging findings, uncommon presentations of common conditions, and high-yield diagnostic pearls for trainees. Outside of medicine, he enjoys golf, classical music, and technological advances in medicine.

Kevin M. Rice, MD is the president of Global Radiology CME and is a radiologist with Cape Radiology Group. He has held several leadership positions including Board Member and 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. He was once again a semifinalist for a "Minnie" for 2021's Most Effective Radiology Educator by AuntMinnie.com. He has continued to teach by mentoring medical students interested in radiology. Everyone he has mentored has been accepted into top programs across the country, including Harvard, UC San Diego, Northwestern, Vanderbilt, and Thomas Jefferson.

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