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There has to be an easier way: facet fracture characteristics that reliably differentiate AOSpine F1 and F2 injuries

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Abstract

Purpose

To identify morphologic features of isolated cervical spine facet fractures that can reliably differentiate AOSpine F1 and F2 injuries.

Materials and methods

Retrospective review of cervical spine CTs on all patients who sustained isolated cervical fractures of the facets presenting to our level 1 trauma center from August 2012 through December 2015. CTs were reviewed for facet fracture characteristics and AOSpine facet fracture classification. Association between facet fracture characteristics and AOSpine classification was assessed through multivariable logistic regression models.

Results

Fifty-six patients with cervical spine fractures isolated to the facets were included in the study. The mean age was 36 (range 9–90) years with 55.4% (n = 31) males. A significant correlation was found between subtype F1 and subtype F2 in laterality (left- or right-sided) (p = 0.004), interfacetal fracture involvement (p < 0.0001), transverse process involvement (p < 0.001), displacement of fracture fragment (p < 0.001), comminution of fracture (p < 0.0001), and vertebral arch disruption (p = 0.001). After multivariable analysis, left side laterality (p = 0.03), transverse process involvement (p = 0.01), and fracture comminution (p = 0.003) were associated with F2 fractures.

Conclusion

Facet fractures with transverse process involvement or comminution have a higher probability of being an F2 fracture. These characteristics may be helpful when categorizing facet fractures using the AOSpine classification.

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Acknowledgments

  1. 1.

    Memorial Hospital System in Houston.

  2. 2.

    We acknowledge the support provided by the Biostatistics/Epidemiology/Research Design (BERD) component of the Center for Clinical and Translational Sciences (CCTS) for this project. CCTS is mainly funded by a grant (UL1 TR000371) from the National Center for Advancing Translational Sciences (NCATS), awarded to University of Texas Health Science Center at Houston.

  3. 3.

    The content is solely the responsibility of the authors and does not necessarily represent the official views of the NCATS.

Author information

Authors and Affiliations

  1. Department of Diagnostic and Therapeutic Radiology, Ramathibodi Hospital, Mahidol University, 270 Rama VI Road, Ratchathewi, Bangkok, 10400, Thailand

    Pinporn Jenjitranant

  2. Department of Diagnostic and Interventional Imaging, McGovern Medical School, The University of Texas Health Science Center at Houston, 6431 Fannin Street, 2.130B, Houston, TX, 77030, USA

    Nicholas M. Beckmann, Suresh K. Cheekatla & O. Clark West

  3. Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science Center at Houston, 6410 Fannin, UTPB 1100.08, Houston, TX, 77030, USA

    Chunyan Cai

  4. Biostatistics/Epidemiology/Research/Design Core, Center for Clinical and Translational Sciences, The University of Texas Health Science Center at Houston, 6410 Fannin, UTPB 1100.08, Houston, TX, 77030, USA

    Chunyan Cai

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  1. Pinporn Jenjitranant
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  2. Nicholas M. Beckmann
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Correspondence to Nicholas M. Beckmann.

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Appendix A

Appendix A

In the AOSpine subaxial cervical spine injury classification, injuries are classified based on morphology, facet injury, neurologic injury, and a small set of disease modifiers. Morphology is divided into three categories with each category assigned a letter classification: compression (A), tension band (B), and translation injuries (C). Compression injuries are further divided into five subtypes (A0–A4). A0 injuries are injuries without fracture (e.g., traumatic disc herniation) or minor fractures (e.g. spinous process or lamina fracture). A1 fractures are fractures through a single end plate without involvement of the posterior vertebral body cortex. A2 fractures are split fractures of the vertebral body involving both end plates without involvement of the posterior wall. A3 fractures are incomplete burst fractures involving a single end plate along with the posterior vertebral body cortex. A4 fractures are complete burst fractures involving both end plates along with the posterior vertebral body cortex. Tension band injuries are divided into three subtypes (B1–B3). B1 injuries are purely bony distraction injuries through the posterior elements. B2 injuries are distraction injuries through the posterior spine resulting in soft tissue disruption with or without accompanying bony injury. B3 injuries are all anterior distraction injury whether soft tissue or bony. There are no subcategories of translational injuries

figure a

Facet fractures are divided into four subtypes (F1–F4). F1 injuries are stable facet fractures, defined as fractures measuring less than 1 cm in length or less than 40% of the total lateral mass. F2 injuries are potentially unstable facet fracture, defined as fractures measuring more than 1 cm in length or more than 40% of the total lateral mass. F3 injuries are pedicolaminar fractures comprised of a combined fracture through the pedicle and ipsilateral lamina resulting in a free-floating lateral mass. F4 injuries are dislocated or perched facets regardless of whether a fracture is present. When classifying fractures, the right side facet fracture is described before the left facet. If both facet have the same grade of injury, the abbreviation “BL” is used.

figure b

Neurologic status is divided into six categories (N0–NX). N0 denotes a neurologically intact patient. N1 indicates a transient neurologic deficit. N2 represents a radiculopathy. Incomplete cord injuries are defined as N3, and N4 represents a complete cord injury. NX is used to describe patients in which neurologic status cannot be assessed. A modifier of “+” is added to denote continued spinal cord compression.

There are four potential clinical modifiers recognized in the AOSpine classification (M1–M4). M1 represents a posterior ligament complex injury without complete disruption (i.e., a B2-type injury without complete tearing of ligaments). M2 designates a critical disc herniation. M3 indicates a disease process that results in stiffening of the axial skeleton (e.g., diffuse idiopathic skeletal hyperostosis). M4 represents a vertebral artery injury.

Using the AOSpine classification system, complex clinical scenarios can be succinctly summarized as a short string of letters and numbers. For example, a patient with ankylosing spondylitis presenting with a hyperextension injury at C4–C5 resulting in right facet chip fracture, free-floating left facet, and transient upper extremity paresthesia can be simply classified as C4–C5:B3 (F1, F3, N1, M3) using the AOSpine system.

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Jenjitranant, P., Beckmann, N.M., Cai, C. et al. There has to be an easier way: facet fracture characteristics that reliably differentiate AOSpine F1 and F2 injuries. Emerg Radiol 26, 391–399 (2019). https://doi.org/10.1007/s10140-019-01684-1

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