The Cervical Spine




Cervical Spine Checklists



Radiographic examination





  • Minimum necessary views




    • Lateral cervical spine to include T1



    • AP cervical spine



    • AP open-mouth odontoid




  • CT examination: minimum necessary




    • Axial, sagittal, and coronal noncontrast images in bone algorithm




      • Extending through at least the level of T1




    • Axial and sagittal images in soft tissue algorithm





Common sites of injury in adults





  • Craniocervical junction (Skull base – C2)




    • Fractures




      • Occipital condyle




        • Atlas – C1



        • Posterior arch



        • Jefferson fracture – fractures of ring anterior and posterior



        • Anterior arch




      • Axis – C2




        • Odontoid (dens)



        • Body




          • Extension of dens fracture



          • Teardrop fracture




        • C2 pars interarticularis fractures – hangman’s fracture





    • Dislocations/subluxation




      • Atlanto-occipital dissociation



      • Atlanto-axial dislocation





  • Lower cervical spine (C3-C7)




    • Fractures




      • Vertebral bodies




        • Compression, distraction, and translation/rotation injuries (SLIC)




          • Simple compression, anterior wedge



          • Teardrop



          • Vertical sagittal split of vertebral body



          • Burst





      • Lateral mass




        • Facets



        • Articular mass



        • Transverse process




      • Spinous process



      • Traumatic disc injuries




    • Dislocations/subluxations




      • Teardrop fracture dislocation



      • Distraction – ligament disruption




        • Intervertebral disc, joint capsules, and interspinous ligament



        • Anterior and posterior longitudinal ligaments




      • Facets – unilateral or bilateral – rotation, shearing injuries




        • Subluxed



        • Perched



        • Dislocated







Special considerations in the elderly





  • Odontoid fractures common




    • Often combined with C1 arch fractures




  • Spinal cord injury in presence of significant degenerative arthritis and disc disease




    • Often with either subtle or even without overt radiographic abnormality (SCIWORA)



    • Hyperextension teardrop




      • Fracture of inferior or superior anterior margins of vertebral body



      • Fracture of osteophyte at superior or inferior anterior margin of vertebral body





  • Fractures in DISH (diffuse idiopathic skeletal hyperostosis)




Common sites of injury in children and adolescents





  • Cervical spine injury ( CSI) rare in children under 8 years of age




    • Relatively more involve upper cervical spine




      • Craniocervical dissociation



      • C1 fractures



      • Dens fractures uncommon in children




        • Rare – apophyseal separations of synchondrosis between dens and body of C2





    • Spinal cord injury without radiographic abnormality (SCIWORA)




  • At and beyond 14 years of age injuries similar to those of adults




    • Relatively more involve lower cervical spine, C4-C7



    • Vertebral body




      • Compression fracture



      • Teardrop fracture dislocation






Injuries likely to be missed





  • Subtle fractures on radiography – need CT




    • Nondisplaced odontoid fractures




  • Facet fractures



  • Occipital condyle fractures




Where else to look when you see something obvious





  • Avoid “satisfaction of search.”



  • Find an injury at one level: closely evaluate the entire cervical spine above and below.




    • Multilevel discontiguous spine fractures



    • Fractures of C1 and C2 often associated with fractures of the lower cervical spine (C4-C7)



    • Two- or three-level fractures encountered in 20% of spinal fractures




      • CT entire T and L spine after identifying fracture of C-spine





  • Find a compression fracture: look for associated posterior element injury.



  • Find a vertebral body injury: look for bony compromise of spinal canal.



  • Find a facet malalignment on one side: look for contralateral facet malalignment/fracture.




Where to look when you see nothing at all





  • Obtain an MRI for those with neurologic signs and symptoms.




    • Spinal cord contusion



    • Herniated nucleus pulposus (HNP)




  • Spinal cord injury without radiographic abnormality (SCIWORA)




    • Check width of spinal canal for spinal stenosis.



    • Spondylosis and degenerative changes in elderly




      • Check for evidence of hyperextension injury.




        • Teardrop fractures at anterior margins of vertebral bodies



        • Anterior widening of disc space



        • Prevertebral soft tissue swelling






  • Review images.




    • Spinolaminar line



    • Interspinous distances



    • Closely evaluate prevertebral soft tissues for swelling.



    • Look for subtle fractures.




      • Facets



      • Transverse processes



      • Spinous processes







Cervical Spine – The Primer


Preamble: Imaging Spinal Trauma


Though traditional and long the mainstay of cervical spine evaluation, radiographs of the cervical spine now have a limited role in the initial assessment of cervical spine trauma. Computed tomography (CT) was first introduced in the 1970s but did not prove adequate for the evaluation of the acutely injured spine until the early 2000s with the introduction and perfection of multidetector CT (MDCT), with rapid exposures coupled with the development of immediate and readily accomplished multiplanar image reconstructions. This permitted coronal and sagittal reconstructions of the entire length of the cervical spine in addition to the standard axial images. With these advances it became apparent that MDCT is more accurate and more efficient in the detection and depiction of spinal injuries.


The comparative difficulty of detection by radiography is shown by a fracture of the dens that is hard to see, if not impossible to identify, on the lateral cervical spine radiograph ( Figure 6-1 A ) but is clearly shown by the MDCT sagittal reconstruction ( Figure 6-1 B ). The associated fracture of the posterior arch of C1 is seen by both examinations ( Figure 6-1 A, C) .




FIGURE 6-1


A, Lateral cervical spine radiograph showing associated fracture of the posterior arch of C1. B, Fracture of the dens shown by MDCT sagittal reconstruction. C, Associated fracture of the posterior arch of C1.


It has been shown that up to 20% or more of cervical fractures disclosed by MDCT are unapparent, overlooked, or simply missed on plain film radiographs of the cervical spine. Thus, the American College of Radiology Appropriateness Criteria: Suspected Cervical Spine Injury states that MDCT, not radiography, is now the primary, preferred, and most appropriate method of imaging suspected cervical spine injury in patients older than 14 years.


Guidelines for imaging potential cervical spine injury (CSI)


There has long been professional and public concern about the overuse of radiography and computed tomography (CT) and the resultant excessive radiation exposure in patients with CSI. Two separate clinical guidelines that allow for triage of patients with suspected CSI have gained general approval: the NEXUS (National Emergency X-Radiography Utilization Study) criteria and the Canadian Cervical Spine Rule (CCR). Though written to address the indications for radiography in cervical spine trauma, they are equally applicable for computed tomography. Both the NEXUS and Canadian Cervical Spine Rule are recognized as valid by the American College of Radiology Appropriateness Criteria: Suspected Cervical Spine Injury. Use of one of these clinical decision rules is recommended to avoid excessive use of cervical spine imaging.


The rules are different for pediatric patients. In patients under age 14, radiography remains the examination of choice and is recommended by the ACR Appropriateness Criteria. This is done for two primary reasons: There is a relatively low incidence of CSI under the age of 14 and a strong desire to limit the radiation exposure dose from CT in younger individuals. However, cervical spine MDCT (multidetector CT) remains as the initial diagnostic modality for all patients age 14 and older because the incidence of CSI approaches that of adults.


NEXUS


The NEXUS criteria allow the physician to forego imaging entirely when certain criteria are met. The patient does not require imaging if there is




  • No midline cervical tenderness



  • No neurologic deficit



  • No distracting injury



  • Normal level of awareness (Glasgow Coma Scale [GCS] = 15)



  • No intoxication



Canadian Cervical Spine Rule


The Canadian Cervical Spine Rule is for alert and stable patients where cervical spine injury is a concern based on consideration of injury mechanism, patient age, and physical examination findings.




  • Prerequisites for this assessment




    • Concern for cervical spine injury



    • Patient alert (GCS = 15)



    • Patient in stable condition




  • High-risk factor that mandates radiography




    • Age ≥65yrs



    • Dangerous mechanism of injury




      • Fall from elevation ≥3 ft/5 stairs



      • Axial load to head (i.e., diving)



      • MVC high speed (>60 mph, 100 km/h), rollover, ejection



      • Motorized recreational vehicle



      • Bicycle crash




    • Paresthesias in extremity



    • Inability to actively rotate neck 45° to the right or left




  • Low-risk factors that allows safe assessment of range of motion




    • Simple rear-end MVC, but not to include




      • Rollover



      • Being pushed into oncoming traffic



      • Being hit by bus, large truck, or high-speed vehicle




    • Sitting position in the ED



    • Ambulatory at any time



    • Absence of midline cervical spine tenderness




Although CT is recommended as the primary means of imaging for the evaluation of cervical spine trauma, radiographic examinations are still ordered and obtained for that purpose. These patients usually have sustained lesser trauma and have no specific signs of cervical spine injury, thus, not qualifying for imaging under the NEXUS or Canadian Cervical Spine Rule guidelines. Such patients may not have sought care until several days after the injury but now do so because of continued and/or increasing pain in the neck and limitation of motion. The NEXUS criteria and Canadian Cervical Spine Rule notwithstanding, the examining physician feels compelled to obtain a radiographic examination of the cervical spine to dispel the patient’s anxiety, meet the “patient’s expectations” of proper care under the circumstances, as well as to demonstrate the physician’s concern for the patient and mollify potential liability concerns. The vast majority of such examinations obtained under these circumstances will show nothing more than straightening of the cervical spine due to muscle spasm without fractures or dislocations. These should be reported as “No evidence of fracture or dislocation” with the added comment, “If pain persists, a repeat examination should be obtained in 7 to 10 days. If pain is severe, consider CT examination to disclose occult fracture.”



Radiographic examination





  • Minimum necessary views




    • Lateral cervical spine to include T1



    • AP cervical spine



    • AP open-mouth odontoid




The radiographic examination of the cervical spine should include a minimum of three views: lateral ( Figure 6-2 A ), AP ( Figure 6-2 B ), and AP open mouth of C1/C2 ( Figure 6-2 C ). Fractures and dislocations are best visualized on the lateral projection ( Figure 6-2 A ). Rotational injuries and fractures of the lateral masses may be evident on the AP projection ( Fig 6-2 B ). A few fractures of the ring of the atlas (C1) and the dens of the axis (C2) may be better visualized on the AP open-mouth view ( Figure 6-2 C ).




  • Pattern of search: Lateral radiograph ( Figure 6-3 A )




    • Basion-dens interval



    • Atlanto-dens interval



    • Alignment of spine ( Figure 6-3 B )



    • Anterior spinal line (solid red line)



    • Posterior spinal line (dashed red line)



    • Spinolaminar line (dotted red line)



    • Interspinous distance (red dots)




      • Vertebral bodies configuration and alignment



      • Facet joints configuration, width and alignment



      • Prevertebral soft tissues




    • Pattern of search: AP radiograph ( Figure 6-4 A, B )




      • Alignment of spinous processes (thin red line)



      • Alignment of vertebral bodies (thick red lines)



      • Interspinous distance (red dots)



      • Undulant, smooth contour of the articular pillars (arrows)




      FIGURE 6-4


      A, B, AP radiograph.




    FIGURE 6-3


    A, Lateral radiograph. B, Alignment of spine.
























Open mouthed odontoid ( Figure 6-5 C ) Lateral view C1/C2 ( Figure 6-5 D )
Lateral alignment of C1-2 (short red lines) Clivus-dens interval (1-1.3 cm)
Atlanto-dental interval (thick red lines) Clivus-dens alignment (vertical red line)
Dens C1 anterior arch-dens interval (broken red circle)
C2 body Width of C2 and C3 (red line in C2-3 disc)
Occipital condyle Prevertebral soft tissues



FIGURE 6-2


A, Lateral view, radiographic examination of the cervical spine. Best visualizes fractures and dislocations. B, AP view, radiographic examination of the cervical spine. Rotational injuries and fractures of the lateral masses may be evident. C, AP open mouth of C1/C2 view, examination of the cervical spine. A few fractures of the ring of the atlas (C1) and the dens of the axis (C2) may be better visualized on the AP open-mouth view.


Computed tomography (MDCT)


MDCT has superseded radiography for the initial assessment of older teenagers and adults because of the accuracy and ease of detecting injuries by MDCT in comparison to radiography. Therefore, when imaging is indicated, cervical spine MDCT is the initial diagnostic modality in all patients age 14 and older.




FIGURE 6-5


A, Open-mouthed odontoid. B , Lateral view C1/C2. C, Open-mouthed odontoid (see table). D, Lateral view C1/C2 (see table).


CT examination: Minimum necessary








    • Axial, sagittal, and coronal noncontrast 2 mm or thinner images in bone algorithm




      • Extending through at least the level of T1




    • Axial and sagittal images in soft tissue algorithm




Having a well-defined and consistent search pattern for cervical spine evaluation will allow rapid identification of cervical injuries in the trauma patient. The minimum should include follow:


Sagittal CT search pattern ( Figure 6-6 )





  • Right atlanto-occipital (occipital-C1) and atlanto-axial (C1-C2) joints ( Figure 6-6 A, B )



  • Right lateral facet alignment and facet fractures ( Figure 6-6 A, B )



  • Anterior spinal line and vertebral body heights ( Figure 6-6 C )



  • Posterior spinal line ( Figure 6-6 C )



  • Spinolaminar line ( Figure 6-6 C )



  • Interspinous distances and posterior spinous processes ( Figure 6-6 C )



  • Midline craniocervical junction alignment ( Figure 6-6 C )




    • Basion-dens interval



    • C1 anterior arch – dens interval



    • Opisthion (posterior margin of foramen magnum) – C1 posterior arch – C2 spinolaminar junction alignment




  • Left lateral facet alignment and facet fractures



  • Left atlanto-occipital (OC-C1) and atlanto-axial (C1-C2) joints




FIGURE 6-6


A, Right atlanto-occipital (occipital-C1) joint. B, Atlanto-axial (C1-C2) joint. C, Anterior spinal line and vertebral body heights, posterior spinal line, spinolaminar line, interspinous distances and posterior spinous processes, midline craniocervical junction alignment.


Axial CT search pattern ( Figure 6-7 A, B )




  • 1.

    Vertebral body for fractures and uncovertebral joints


  • 2.

    Transverse processes and transverse foramina


  • 3.

    Pedicles


  • 4.

    Facets (also referred to as articular pillars)


  • 5.

    Posterior arch with laminae


  • 6.

    Spinous process




FIGURE 6-7


A, B, Axial CT search pattern.


Coronal search pattern ( Figure 6-8 A, B )




  • 1.

    Occipital condyles


  • 2.

    Facets and lateral masses (also referred to as articular pillars)


  • 3.

    Transverse processes


    Spinous processes (not shown)




FIGURE 6-8


A, B, Coronal search pattern.


Soft tissue windows ( Figures 6-9 and 6-10 )





  • Prevertebral soft tissues



  • Paraspinous musculature for edema/ hemorrhage



  • Tectorial membrane at craniocervical junction



  • Spinal canal for disc injuries, epidural hematoma, bone fragments




FIGURE 6-9


A, Normal appearance of the soft tissue anatomy at the craniocervical junction. Note the course and position of tectorial membrane extending from the clivus to the posterior surface of the dens. The posterior longitudinal ligament lining the spinal canal is seen on the posterior surface of the vertebral bodies, and the ligamentum flavum lining the posterior surface of the spinal canal is shown on and between the anterior surfaces of the laminae. B, Extradural hematomas pointing to underlying bone or joint abnormalities can be identified. C, The bone window clearly shows subluxation of the atlanto-occipital joint as the cause of the extradural hematoma.



FIGURE 6-10


A, Type II fracture of the dens. B, Mid-sagittal recon soft tissue window image revealed a small hematoma about the fracture. Closer inspection revealed a rounded density at the posterior surface of the C3-4 disc space and a similar density posteriorly consistent with an enfolded, hypertrophied ligamentum flavum. C, MRI of canal is constricted between these two densities. D, Herniated disc compressing the spinal cord.


It is important to view all images in both bone and soft tissue windows. Abnormal findings in the soft tissues point to underlying bone and joint abnormalities. The normal appearance of the soft tissue anatomy at the craniocervical junction is shown in Figure 6-9 A . Note the course and position of tectorial membrane extending from the clivus to the posterior surface of the dens. The posterior longitudinal ligament lining the spinal canal is seen on the posterior surface of the vertebral bodies, and the ligamentum flavum lining the posterior surface of the spinal canal is shown on and between the anterior surfaces of the laminae ( Figure 6-9 A ). Extradural hematomas pointing to underlying bone or joint abnormalities may be identified ( Figure 6-9 B ). In this case, the bone window clearly shows subluxation of the atlanto-occipital joint ( Figure 6-9 C ) as the cause of the extradural hematoma.


Bulging or herniated discs may be identified indicating the need for further evaluation by MRI ( Figure 6-10 ). This elderly patient sustained a type II fracture of the dens ( Figure 6-10 A ). Mid-sagittal recon soft tissue window image revealed a small hematoma about the fracture. Closer inspection revealed a rounded density at the posterior surface of the C3-4 disc space and a similar density posteriorly consistent with an enfolded, hypertrophied ligamentum flavum ( Figure 6-10 B ). The canal is constricted between these two densities. MRI confirms these findings ( Figure 6-10 C, D ). Note the herniated disc compressing the spinal cord ( Figure 6-10 D ). The spinal cord shows evidence of edema and/or myelomalacia. This proved to be important for preoperative planning. The fracture of the dens was reduced and pinned with single-screw fixation. An anterior discectomy was performed at C3-4 to relieve the pressure on the spinal cord. C3-4 was fused with placement of bone graft and a metal cage in the disc space.


Paraspinous musculature


Paraspinous muscular edema is a useful sign, when present, to indicate the presence of significant injury to the cervical spine soft tissues. However, edema takes time to develop, and the absence of paraspinous muscular edema does not exclude soft tissue injury. Evaluate the paraspinous soft tissues on a narrow CT window to visualize this finding optimally ( Figure 6-11 A ), confirmed on MRI in this patient ( Figure 6-11 B ).




FIGURE 6-11


A, B, Paraspinous soft tissues on a narrow CT window, confirmed on MRI in this patient.


Magnetic resonance (MR) evaluation


Indications for MR imaging in the cervical spine have expanded in recent years. For a patient with suspected cervical spine trauma, the American College of Radiology (ACR) appropriateness criteria recommend MRI evaluation of the cervical spine in addition to MDCT, especially when ligamentous or neurologic injury is suspected. ( ACR 2013 update ). The spectrum of spinal cord injury ranges from mild edema manifested by increased T2 signal in a patient without underlying myelomalacia, to severe edema, cord hemorrhage, and transection. Extensive cord signal change or compression on MRI, in a patient with only a partial or mild neurologic deficit, indicates a spinal cord at risk for further injury and a patient in whom aggressive management is warranted.


Integrity of the intervertebral disc and associated ligamentous structures is best evaluated with MRI. The anterior and posterior longitudinal ligaments, interspinous and supraspinous ligaments are assessed, in addition to the capsular ligaments of the facets. Imaging of the intervertebral disc can be complex, with annular fissures, disk protrusions and extrusions often difficult to date. Clinical history and physical exam findings are important in determining whether a disc protrusion is acute or chronic. A comprehensive review of cervical spine MRI is beyond the scope of this primer.



Common sites of injury in adults





  • Craniocervical junction (skull base – C2)




    • Fractures




      • Occipital condyle



      • Atlas – C1




        • Posterior arch



        • Jefferson fracture – fractures of ring anterior and posterior



        • Anterior arch




      • Axis – C2




        • Odontoid (dens)



        • Body




          • Extension of dens fracture



          • Teardrop fracture




        • C2 neural arch – hangman’s fracture





    • Dislocations/subluxation




      • Atlanto-occipital dissociation



      • Atlanto-axial dislocation





Diagrams of the craniocervical junction ( Figure 6-12 A , 6-12 B , Clivus, C1 and C2) pinpoint the common sites of fractures and dislocations in adults. The most common sites of fracture are identified by red lines. Red arrows demonstrate displacement of the lateral masses of C1 indicative of simultaneous fractures of the anterior and posterior arches of the atlas (C1). Your pattern of search should include all sites.




FIGURE 6-12


A, B, Diagrams of craniocervical junction pinpointing the common sites of fractures and dislocations in adults. The most common sites of fracture are identified by red lines. Red arrows demonstrate displacement of the lateral masses of C1 indicative of simultaneous fractures of the anterior and posterior arches of the atlas (C1).


Craniocervical junction injuries


Occipital condyle fractures


Occipital condyle fractures indicate disruption of the alar ligament, with or without other ligaments, at the craniocervical junction. The injury may be stable (unilateral ligament involvement) or unstable (bilateral involvement).




  • Diagnosis : There are three major types ( Figures 6-13 and 6-14 ):




    • Type I: comminution of the occipital condyle without significant displacement



    • Type II: extension of a basilar skull fracture through the occipital condyle



    • Type III: avulsion of the occipital condyle with inferomedial displacement




    FIGURE 6-13


    A, Type I occipital condyle fracture: comminution of the occipital condyle without significant displacement. B, Type II occipital condyle fractures: extension of a basilar skull fracture through the occipital condyle. C, Type III occipital condyle fractures: avulsion of the occipital condyle with inferomedial displacement.



    FIGURE 6-14


    A, Type I occipital condyle fracture: comminution of the occipital condyle without significant displacement. B, Type II occipital condyle fractures: extension of a basilar skull fracture through the occipital condyle. C, Type III occipital condyle fractures: avulsion of the occipital condyle with inferomedial displacement.



Figure 6-15 is another type III fracture of the left occipital condyle shown in the axial ( Figure 6-15 A ), coronal ( Figure 6-15 B ), and sagittal ( Figure 6-15 C ) left lateral reconstruction images.




FIGURE 6-15


A, Type III fracture of the left occipital condyle shown in the axial left lateral reconstruction image. B, Type III fracture of the left occipital condyle shown in the coronal left lateral reconstruction image. C, Type III fracture of the left occipital condyle shown in the sagittal left lateral reconstruction image.


Atlanto-occipital dissociation


Mechanism


Atlanto-occipital dissociation is most commonly due to anterior dislocation of the head relative to the spine but may also be caused by longitudinal distraction or posterior dislocation. This injury is much more common in young children. Atlanto-occipital dissociation is usually fatal, particularly when widely displaced, but there are some survivors. Survival is three times more likely in children, principally in those with lesser injuries and displacement.


Diagnosis


Evaluate the alignment of the occiput relative to C1. The joint surfaces should be parallel. The width of atlanto-occipital articulation is generally ≤2 mm ( Figure 6-16 A, B ). Look for supporting findings, like soft tissue swelling at the craniocervical junction (see Figure 6-18 ) or joint asymmetry ( Figure 6-16 C, D ) compared with the contralateral side.




FIGURE 6-16


A, B, The joint surfaces should be parallel. The width of atlanto-occipital articulation is generally ≤2 mm. B, Soft tissue swelling at the craniocervical junction. C, D, Joint asymmetry compared with the contralateral side.


This patient demonstrates atlantal-occipital joint widening ( Figure 6-17 A ), posterior dislocation of the cervical spine ( Figure 6-17 B ), and an increased basion-dens interval ( Figure 6-17 C ).




FIGURE 6-17


A, Atlantal-occipital joint widening. B, Posterior dislocation of the cervical spine. C, Increased basion-dens interval.


An anterior atlanto-occipital dissociation, with fracture of the right occipital condyle, is demonstrated by anterior displacement of the dens and C1 ( Figure 6-18 A, B ) and an associated extradural hematoma at the foramen magnum ( Figure 6-18 B ). Note also a small avulsion from the tip of the dens ( Figure 6-18 B ). Axial ( Figure 6-18 C ) and right sagittal images ( Figure 6-18 D, E ) reveal a fracture of the right occipital condyle and anterior dislocation of the atlanto-occipital joint.




FIGURE 6-18


A, Anterior atlanto-occipital dissociation, with fracture of the right occipital condyle, is demonstrated by anterior displacement of the dens and C1. B, Associated extradural hematoma at the foramen magnum, also a small avulsion from the tip of the dens. Axial ( C ) and right sagittal images ( D, E ) reveal a fracture of the right occipital condyle and anterior dislocation of the atlanto-occipital joint.


C1 ring fractures


C1 ring fractures may involve the anterior arch, the posterior arch, or both arches ( Figure 6-19 ). Fractures involving both arches are known as Jefferson fractures.




FIGURE 6-19


C1 ring fractures may involve the anterior arch, the posterior arch, or both arches.


Posterior arch


Mechanism


Hyperextension of the head compressing C1 arch between occiput and neural arch of C2.


Diagnosis


The most common posterior arch fracture is a bilateral vertical fracture of the neural (posterior) arch ( Figures 6-20 and 6-21 ). However, this fracture must be distinguished from developmental defects, which have rounded, tapered, and corticated margins ( Figure 6-21 , black arrow). The latter is a congenital failure of fusion of the two limbs of the posterior arch in the midline, a common normal variant, associated with a dens fracture and bilateral fractures of the posterior arch in this patient ( Figure 6-21 ).




FIGURE 6-20


The most common posterior arch fracture is a bilateral vertical fracture of the neural (posterior) arch.



FIGURE 6-21


This fracture must be distinguished from developmental defects, which have rounded, tapered, and corticated margins. This latter is a congenital failure of fusion of the two limbs of the posterior arch in the midline, a common normal variant, associated with a dens fracture and bilateral fractures of the posterior arch in this patient.


Anterior arch


Mechanism


Hyperextension of the head upon the neck results in the dens pressing against the anterior arch of C-1 and results in simultaneous fractures of the dens and anterior arch ( Figure 6-22 A, B ). Avulsions of the anterior longitudinal ligament and the longus colli muscle from their insertions create typically minimally displaced, horizontal fractures, often associated with dens fractures.




FIGURE 6-22


A, B, “Plough” fractures, segmental fractures of the anterior arch that are displaced anteriorly. B, Commonly associated with fractures of the dens.


Diagnosis


Segmental fractures of the anterior arch that are displaced anteriorly ( Figure 6-22 A ), so-called “plough” fractures, are due to the shearing forces of hyperextension injuries in the elderly. These are commonly associated with fractures of the dens ( Figure 6-22 B ).


Jefferson fracture


Mechanism


Blow to the vertex (axial loading) as in diving into shallow water.


Diagnosis


This is a comminuted C1 fracture that involves both the anterior and posterior arches with outward displacement of the fragments ( Figure 6-23 ) and commonly referred to as a Jefferson fracture. Frontal radiograph ( Figure 6-23 A ) and coronal CT images ( Figure 6-23 B ) show lateral subluxation of the lateral margins of C1 on C2 bilaterally. Axial CT image ( Figure 6-23 C ) and 3D reconstruction ( Figure 6-23 D , different patient) show two fractures in the anterior arch and one in the posterior arch.




FIGURE 6-23


A, Jefferson fracture, frontal radiograph. B, Jefferson fracture, coronal CT images. C, D, Axial CT image (A) and 3D reconstruction (B) show two fractures in the anterior arch and one in the posterior arch.


The reverse may also occur: two fractures in the posterior arch and one in the anterior arch ( Figure 6-24 A, B, C ) or, alternatively, two fractures in each arch.




FIGURE 6-24


Two Jefferson fractures in the posterior arch ( A and B ) and one in the anterior arch ( C ).


Atlanto-axial dislocation


Mechanism


Atlanto-axial dislocation ( Figure 6-25 A, B ) is said to be the most common dislocation at the craniocervical junction but is rarely due to trauma. It is more commonly associated with rheumatoid arthritis, its variants, or Down syndrome. The dislocation may also be transient secondary to ligamentous laxity associated with severe infections of the head and neck.




FIGURE 6-25


Atlanto-axial dislocation.


Diagnosis


Flexion views may be necessary to demonstrate the subluxation, which may be reduced in neutral position and extension. Normal distance of the anterior cortex of the dens to the posterior cortex of the anterior arch of the atlas:




  • 2.5 mm in adults



  • 5 mm in children



In <10% of cases, the predens space is V-shaped, widened cranially. The cranial portion of the V still usually measures <4 mm but may measure up to 7 mm and still be normal.


A widely displaced atlanto-axial dislocation in an elderly woman associated with a type II dens fracture and plough fracture of C1 are shown ( Figure 6-26 A, B, C, D ). The right ( Figure 6-26 A ) and left ( Figure 6-26 C ) facet joints are dislocated the full width of the facets posteriorly. A displaced fracture of the dens and wide, asymmetric separation between the anterior arch of C1 and dens is shown in the mid-sagittal reconstructed image ( Figure 6-26 B ). There is also a plough fracture of the anterior arch of C1 seen in the axial image ( Figure 6-26 D ).




FIGURE 6-26


A widely displaced atlanto-axial dislocation in an elderly woman associated with a type II dens fracture and plough fracture. The right (A) and left (C) facet joints are dislocated the full width of the facets posteriorly. A displaced fracture of the dens and wide, asymmetric separation between the anterior arch of C1 and dens is shown in the mid-sagittal reconstructed image (B) . There is also a plough fracture of the anterior arch of C1 seen in the axial image (D).


Axis (C2)


Fractures of the odontoid process (dens fractures)


Fractures of the odontoid are common in the elderly and frequently accompanied by fractures of C1 as a result of low-impact trauma such as falls from a standing height. Dens fractures occur in younger individuals from motor vehicle accidents and other high-impact trauma but are rarely encountered in children.


Mechanism


Hyperextension of head upon the cervical spine is the most common mechanism. Hyperflexion, axial loading, and shear forces contribute in some cases.


Diagnosis


Dens fractures are popularly classified by the Anderson and D’Alonzo Classification.




  • Type I: (4%) an oblique fracture limited to the dens ( Figure 6-27 A )




    FIGURE 6-27


    A, Type I: (4%) an oblique fracture limited to the dens. B, Type II: (66%) a transverse fracture at the base of the dens. C, Type III: (30%) a fracture at the base of the dens extending into body of C2.



  • Type II: (66%) a transverse fracture at the base of the dens ( Figure 6-27 B )



  • Type III: (30%) a fracture at the base of the dens extending into body of C2 ( Figure 6-27 C )



The typical features of a type II fracture of the dens are shown ( Figure 6-28 A, B ); the fracture line is transverse at the base of the dens. Note the dens is displaced posteriorly, and a tag of the cortex of the dens extends posteriorly from the base of the dens in keeping with a hyperextension mechanism of injury ( Figure 6-28 A ).




FIGURE 6-28


A, B, Typical features of a type II fracture. The fracture line is transverse at the base of the dens. Note the dens is displaced posteriorly and a tag of the cortex of the dens extends posteriorly from the base of the dens in keeping with a hyperextension mechanism of injury ( A ).


Figures 6-29 and 6-30 demonstrate the characteristic features of Anderson and D’Alonzo type III dens fractures. Note the fractures extend from the base of the dens into the body of C2. The body of C2 is comminuted, which has made the body of C2 wider than the body of C3 in one of the cases ( Figure 6-29 A, B ) and less so in the other ( Figure 6-30 A ). This widening is known as a “fat C2” and is characteristic of a type III odontoid fracture. Comminution with fracture lines extending from the base of the dens and superior facets into the bodies of C2 are well shown by axial ( Figure 6-29 D ) and coronal ( Figure 6-29 C and 6-30 B ) images.


Mar 23, 2019 | Posted by in MUSCULOSKELETAL IMAGING | Comments Off on The Cervical Spine
Premium Wordpress Themes by UFO Themes