Cervical Spine Trauma: Pearls and Pitfalls

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Bernstein and BaxterFig. 5—55-year-oldman with atypicalhangman’s fracture.Transaxial CTangiography imageshows fracturesthrough bothtransverse foramina,with occlusion of rightvertebral artery.Fig. 6—21-yearoldwoman withanterior subluxation.Lateral cervicalspine radiographshows subtle signsof hyperflexion,including C6–7interspinous widening(arrow), uncoveringof facets, and slightanterior translation.Courtesy of Rybak L,NYU Langone MedicalCenter, New York, NY.limited to posterior ligament complex injury and is stable. Anteriorsubluxation reflects further hyperflexion with disruptionof the posterior longitudinal ligament and posterior disk annulus(middle of column of Denis), which leads to instability.The radiologic evaluation of hyperflexion sprain and anteriorsubluxation can be challenging. Radiographic and CT signsare subtle; even when recognized, the significance may not beappreciated. However, it is important to understand becausemissed injury can lead to significant morbidity, including pain,kyphosis, delayed vertebral dislocation, and neurologic deficit.Appearance on Relevant ModalitiesImaging features of progressively severe hyperflexion injuriesinclude (from posterior to anterior) fanning of spinousprocesses or interspinous widening, uncovered facets, widenedposterior disk space, focal kyphosis, and anterior subluxation.Vertebral body compression fractures may seen with sufficienthyperflexion and axial loading.When CT findings are equivocal, MRI can detect edema ofthe cervical ligaments and soft tissues. Flexion and extensionradiographs should not be performed in the presence of musclespasm to avoid false-negative results.Differential DiagnosisCervical straightening and reversal of the normal lordosis mayoccur in cervical muscle spasm and should be distinguished fromtrue anterior subluxation. Close attention to facet alignment onCT and posterior disk spacing are most helpful in this regard.Degenerative changes may be confused with traumaticsubluxation. In contrast to traumatic anterior subluxation, retrolisthesisis the usual consequence of cervical spondylosisbecause of normal cervical lordosis and posterior inclinationof the articular facets. Degenerated facet joints are most commonlynarrowed, with thinning of the bony facet from longtermwear. In traumatic subluxations, however, the facet jointsare often abnormally widened.Hyperextension-DislocationRelevant Mechanism, Anatomy, and CauseHyperextension cervical spine injuries range from the stablehyperextension sprain to the highly unstable hyperextensiondislocation.They are predominantly ligamentous disruptionsthat progress from anterior to posterior, beginning with the anteriorlongitudinal ligament and anterior annulus fibrosus andextending through the posterior annulus, posterior longitudinalligament, and ligamentum flavum. The hyperextensiondislocationinjury often results in major neurologic deficits,typically a central cord syndrome.Approximately 25% of cervical spine injuries are the resultof hyperextension forces, either associated with direct impact,or through a whiplash effect. Direct impact injuries are oftenassociated with frontal head or facial injuries. Conditions predisposingto injury include age older than 65 years, with increasedpropensity for falls and motor vehicle crashes, degenerativechanges, spinal canal stenosis, and osteopenia.Appearance on Relevant ModalitiesAlthough hyperextension-dislocation injuries are severe andunstable, imaging signs are often subtle. Extensive soft-tissueinjury and displacement occurs at the moment of trauma, butmuscular spasm and immobilization in a cervical collar canresult in an apparently normal spine examination.Hyperextension-dislocation injuries usually involve thelower cervical spine. Signs on lateral radiographs and sagittalCT reformations include mild anterior intervertebral disk spacewidening, anterior vertebral body avulsion fragments, and facetmalalignment (Fig. 7A). In the normal spine, facets should beparallel. With extension injuries, one may see V-shaped facetjoints that are wide anteriorly and tapered posteriorly.MRI reveals the extent of discoligamentous injury. T2-weighted images show ligamentous disruption, soft-tissueedema, disk protrusion, and spinal cord injuries (Fig. 7B).Differential DiagnosisLike the hyperflexion sprain and anterior subluxation, thehyperextension-dislocation may be overlooked and misinterpretedas normal on both radiographs and CT. Neurologic24 2012 ARRS Categorical Course
Cervical Spine TraumaFig. 7—64-year-old man with hyperextensiondislocation.A, Midsagittal CT image shows slight anteriordisc space widening at C3–4 and osteophytechip fracture (arrow). Spinal column is otherwisewell aligned.B, Midsagittal T2-weighted MRI showsprevertebral soft-tissue edema with disruptionof anterior longitudinal ligament (arrow).Contused spinal cord is squeezed betweentraumatic disc herniation (arrowhead) andligamentum flavum. Posterior soft-tissue injuryis indicated by high signal changes. (Reprintedwith permission from [1])ABFig. 8—69-year-oldman with fused spinehyperextensionfracture with corticaldisruption of C6(arrow). Transversefracture orientation iseasily overlooked ontransaxial CT.deficit, concurrent head trauma, or facial fracture should raisesuspicion for this potentially unstable injury.Vertebral body corner fractures, when present in hyperextension-dislocationinjuries, tend to have a preferentially horizontalorientation. This is in contrast to the more verticallyoriented hyperextension teardrop fracture, which is usuallyseen in the upper cervical spine, typically at C2.Cervical Spine Trauma in PreexistingPathologic Conditions: Fused SpineHyperextension InjuryRelevant Mechanism, Anatomy, and CauseAnkylosing spondylitis and diffuse idiopathic skeletal hyperostosisboth result in intervertebral bridging with fusion andpoor underlying bone quality. Rigidity of the fused segment rendersit susceptible to fracture with even mild hyperextension.Most patients with fused spine hyperextension fractures haveprofound neurologic deficits. Delayed neurologic injury occurs in20–100% of cases when initial diagnosis is missed. The high incidenceof noncontiguous additional fractures mandates screeningof the entire spine. Surgical repair requires long segment fixation.Appearance on Relevant ModalitiesA high index of suspicion should be maintained with traumapatients who have ankylosing spondylitis or diffuse idiopathicskeletal hyperostosis because fused spine hyperextension fracturesmay be occult on radiographs and CT. This is due to bothfrequent spontaneous reduction and underlying osteoporosis,particularly in patients with advanced disease.Sagittal CT reformations optimally identify undisplacedsubtle fractures because they are often horizontal, limitingthe utility of transaxial images (Fig. 8). Fractures may involvethe vertebral body, the fused disk space, or traverse both in anoblique fashion. These fractures typically involve the lowercervical spine and are complete, crossing all ossified ligamentsfrom anterior to posterior and resulting in marked instability.REFERENCE1. Legome E, Shockley LW, eds. Trauma: A Comprehensive Emergency Medicine Approach.Cambridge, UK: Cambridge University Press: 2011SUGGESTED READING1. American College of Radiology. ACR appropriateness criteria: suspected spinetrauma. American College of Radiology Website. www.acr.org/SecondaryMain-MenuCategories/quality_safety/app_criteria/pdf/ExpertPanelonPediatricImaging/Othertopics/SuspectedSpineTrauma.aspx. Published 1999. Updated 2009. AccessedOctober 19, 20112. Daffner RH, Daffner SD. Vertebral injuries: detection and implications. Eur J Radiol2002; 42:100–1163. Hoffman JR, Mower WR, Wolfson AB, Todd KH, Zucker MI. Validity of a set of clinicalcriteria to rule out injury to the cervical spine in patients with blunt trauma: NationalEmergency X-Radiography Utilization Study Group. N Engl J Med 2000; 343:94–994. Rao SK, Wasyliw C, Nunez DB Jr. Spectrum of imaging findings in hyperextensioninjuries of the neck. RadioGraphics 2005; 25:1239–12545. Stiell IG, Wells GA, Vandemheen KL, et al. The Canadian C-spine rule for radiographyin alert and stable trauma patients. JAMA 2001; 286:1841–1848Pitfalls in Clinical Imaging 25
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