Biomechanical, Radiographic and Osteologic Observations of Lower Cervical Spine Injuries

Teardrop fracture following head-first impact in an ice hockey player: Case report and analysis of injury mechanisms

“…Continued compression and flexion caused the anterior fragment to be displaced forward, rotated in extension, and partially crushed. The fracture line of the anterior fragment was related in part to the sagittal plane concavity of the inferior endplate, consistent with the hypotheses of Kim et al 6 and Kazarian et al 12 Following separation of the anterior VB fragment, the posterior VB fragment sustained a vertical fracture in the sagittal plane (Figure 1 D-F). This vertical fracture was offset to the right of the midsagittal plane at its superior surface and propagated to the midsagittal plane at its inferior surface.…”

“…A VB of the middle or lower cervical spine has distinct features: 1) a superior surface with uncinate processes that project upward from its lateral margins and 2) a saddle-shaped inferior surface, 10 convex laterally and concave anteroposteriorly with the anteroinferior corner often skewed forward. 11,12 Bilateral Luschka joints, between the uncinate processes and the inferior borders of the adjacent VB, have been shown in mathematical modeling to increase cervical motions, while the uncinate processes reduce motions and coupling. 13 Hypotheses regarding teardrop fracture etiology, outlined by Kazarian et al 12 are based upon radiographic analyses of cervical trauma patients, biomechanics, and the observations of vertebral anatomy.…”

“…11,12 Bilateral Luschka joints, between the uncinate processes and the inferior borders of the adjacent VB, have been shown in mathematical modeling to increase cervical motions, while the uncinate processes reduce motions and coupling. 13 Hypotheses regarding teardrop fracture etiology, outlined by Kazarian et al 12 are based upon radiographic analyses of cervical trauma patients, biomechanics, and the observations of vertebral anatomy. The anterior fracture fragment forming the teardrop is hypothesized to have been sheared off of the larger posterior VB fragment.…”

“…14 Another hypothesis is that the fracture may initiate and propagate at the basivertebral veins. 12 Vertebral arterial anatomy indicates that the largest vein enters the posterior surface of the VB in the midsagittal plane and penetrates to approximately half its anteroposterior width. 15 Lastly, the compression load may decrease the height of the superior disc and increase its hoop tension which transfers lateral forces to the uncinate processes causing their outward expansion.…”

“…15 Lastly, the compression load may decrease the height of the superior disc and increase its hoop tension which transfers lateral forces to the uncinate processes causing their outward expansion. 12 The lateral forces which separate the right and left sides of the VB often cause associated fractures of the neural arch.…”