Spine



Spine


Thomas H. Berquist

William E. Clifton

Prasanna G. Vibhute

Vivek Gupta

Jeffrey J. Peterson



▪ TRAUMA: CERVICAL SPINE—BASIC CONCEPTS


KEY FACTS



  • Traumatic injuries to the cervical spine comprise approximately 65% of all spinal injuries.


  • The incidence of cervical spine injury (CSI) after blunt trauma is 2% to 6%.


  • Cervical spine immobilization is an important initial step in preventing neurologic injury after trauma. The immobilization may be “cleared” by a combination of physical examination findings and radiographic studies.


  • Computed tomography (CT) has approximately 100% sensitivity for detection of fractures compared with 65% for radiographs, and therefore should be the first imaging modality in patients with suspected injury (Level I evidence).


  • NEXUS (National Emergency X-Radiography Utilization Study) criteria and CCR (Canadian C-Spine Rule) are validated clinical decision tools to safely rule out CSI without the need to obtain radiographs in alert and stable trauma patients. Both have sensitivity of 90% to 100% for ruling out CSI (Table 2-1).


  • ACR Appropriateness Criteria rating if imaging indicated by NEXUS criteria:



    • CT cervical spine without intravenous (IV) contrast—9


    • Radiographs—6


    • Magnetic resonance imaging (MRI) without IV contrast for myelopathy—9, and treatment planning for unstable spine—8


    • Computed tomography angiography head and neck if clinical or imaging findings suggest arterial injury—9


  • Understanding the mechanism of injury is helpful for evaluating images and determining prognosis (Table 2-2).


  • Stability of injuries is important to assess. This can be usually accomplished on the lateral view or reformatted CT images, although all images should be assessed.


  • Indicators of instability include



    • More than one column involved (Fig. 2-7)


    • Subluxation greater than 3 mm


    • Increased interspinous distance


    • Facet joint widening


    • Narrowed disc or widened space


    • Vertebral compression greater than 25%


  • Not all radiographically documented cervical spine injuries are clinically significant (Table 2-3)









Table 2-1







NEXUS (National Emergency X-Radiography Utilization Study)


Patient’s neck can be clinically cleared safely without imaging if all five low-risk conditions are met:


No posterior midline neck pain or tenderness


No focal neurologic deficit


Normal level of alertness


No evidence of intoxication


No clinically apparent, painful other bodily injury distracting patient’s attention away from neck injury


CCR (Canadian C-Spine Rules)


image


Adapted from Stiell IG, Clement CM, McKnight RD, et al. The Canadian C-Spine Rule versus the NEXUS low-risk criteria in patients with trauma. N Engl J Med. 2003; 349:2510-2518.










Table 2-2 CERVICAL SPINE TRAUMA: MECHANISMS OF INJURY











































Type of Injury


Radiographic Features


Comments


Hyperflexion



Most common


Disruptive hyperflexion


Sprain, transient dislocation


Locked facets


Spinous process fractures


Compressive hyperflexion


Vertebral wedge fractures


Teardrop fractures


Fracture/dislocations


Shearing injuries


Anteriorly displaced odontoid fractures


Hyperextension



Findings may be subtle


Disruptive hyperextension


Hangman’s fractures


Hyperextension sprain


Anterior inferior body fractures


Compressive hyperextension


Posterior arch fractures


Hyperextension fracture/dislocation


Shearing


Posteriorly displaced odontoid fractures


Axial compression


Jefferson fractures


Burst fractures


Flexion-rotation


Rotary fixation of C1 on C2


Unilateral locked/perched facets


Lateral flexion


Uncinate process fractures


Transverse process fractures


Lateral wedge fractures










Table 2-3







Radiographically documented cervical spine injuries which are NOT clinically significant:


1. Spinous process fracture


2. Simple wedge compression fracture with less than 25% vertebral body height loss


3. Isolated avulsion without ligamentous injury


4. Type 1 odontoid fracture


5. Endplate fracture


6. Osteophyte fracture (should not include vertebral corner fracture or teardrop fracture)


7. Trabecular bone injury


8. Transverse process fracture


These, when occurring in isolation, are extremely unlikely to cause harm to the patient even if missed on the radiographs, and require no specific treatment.


Adapted from Hoffman JR et al. Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma. N Engl J Med. 2000;343:94-99.








FIGURE 2-1. Disruptive hyperflexion injuries. (A) Mechanism (blow to the occipital region) that causes more posterior soft tissue injury compared with anterior compression. (B) Lateral radiograph shows widened interspinous distance (double arrow), subluxation of the facets (posterior arrowhead) and slight subluxation, and disc space widening (anterior arrowhead).






FIGURE 2-2. Compressive hyperflexion injuries. (A) Mechanism of injury with force transmitted to the anterior vertebral body. (B) Lateral radiograph demonstrates compression of C7 and T1 (arrow).







FIGURE 2-3. Disruptive hyperextension injuries. (A) Disruptive hyperextension injury with anterior distraction. The cord may be compressed. (B) Lateral radiograph shows anterior disc space widening and vertebral chip fracture (arrow).






FIGURE 2-4. Compressive hyperextension injuries. (A) Mechanism resulting in posterior compression and less anterior distraction. (B) Lateral radiograph demonstrates a vertical posterior arch fracture (arrow).







FIGURE 2-5. Flexion-rotation injuries. (A) Mechanism of injury. (B) Lateral radiograph shows a unilateral locked facet with subluxation and “bow-tie” configuration (lines) of the facets.






FIGURE 2-6. Vertical compression injuries. (A) Mechanism of injury. (B, C) Axial computed tomography (CT) images of a burst fracture.







FIGURE 2-6. (continued)






FIGURE 2-7. Instability. (A) Lateral radiograph demonstrates the anterior (anterior longitudinal ligament, body, and disc), middle (posterior body and disc and posterior longitudinal ligament), and posterior (facet joints and posterior ligaments) columns. When two columns are involved, the injury should be considered unstable. (B) Lateral view shows multiple column involvement with widened interspinous distance (double arrow), subluxation (black lines), and anterior disc space narrowing (arrowhead) caused by a disruptive hyperflexion injury.



SUGGESTED READING

Antevil JL, Sise MJ, Sack DI, et al. Spiral computed tomography for the initial evaluation of spine trauma: a new standard of care? J Trauma. 2006;61:382-387.

Barba CA, Taggert J, Morgan AS, et al. A new cervical spine clearance protocol using computed tomography. J Trauma. 2001;51:652-656, discussion 656-657.

Denis F. Spinal instability as defined by the three-column spine concept in acute spinal trauma. Clin Orthop. 1984;189:65-76.

Gehweiler JA, Osborne RL, Becker RF. The Radiology of the Vertebral Trauma. Philadelphia: WB Saunders; 1980.

Griffen MM, Frykberg ER, Kerwin AJ, et al. Radiographic clearance of blunt cervical spine injury: plain radiograph or computed tomography scans. J Trauma. 2003;55:222-227.

Sliker CW, Mirvis SE, Shanmuganathan K. Assessing cervical spine stability in obtunded blunt trauma patients: review of the medical literature. Radiology. 2005;234:733-739.



▪ TRAUMA: CERVICAL SPINE—ATLANTO-OCCIPITAL FRACTURE DISLOCATIONS


KEY FACTS



  • Atlanto-occipital dislocations are usually fatal; therefore, imaging is rarely performed.


  • The injury results from high-velocity shearing forces dislocating the head from C1.


  • In children, the condyles are less well developed, making patients more susceptible to injury.


  • Occur due to widespread ligamentous disruption between the occiput and upper cervical spine. Often without bony fractures and hence more ready missed by an inexperienced observer.


  • If the patient survives the injury, treatment is occipital-C2 fusion.






FIGURE 2-8. Atlanto-occipital dislocation. (A) Lateral radiograph shows a huge prevertebral hematoma (arrows) with anterior dislocation of the occipital condyles (arrowhead). (B) Sagittal computed tomography (CT) reconstruction in another patient following high-speed motor vehicle accident shows clear separation of the occipital condyles from the C1 with huge prevertebral and epidural hematomas and stretching to the cervicomedullary junction. Both patients did not survive.



SUGGESTED READING

Deliganis AV, Baxter AB, Hanson JA, et al. Radiologic spectrum of craniocervical distraction injuries. Radiographics. 2000;20:S237-S250.

Hall GC, Kinsman MJ, Nazar RG, et al. Atlanto-occipital dislocation. World J Orthop. 2015;6(2):236-243. doi:10.5312/wjo.v6.i2.236.

Hosalkar HS, Cain EL, Chin KR, et al. Traumatic atlanto-occipital dislocation in children. J Bone Joint Surg. 2005;87A:2480-2488.



▪ TRAUMA: CERVICAL SPINE—C1 FRACTURES


KEY FACTS



  • Fractures of the atlas (C1) account for 25% of craniocervical injuries, 3% to 13% of cervical spine injuries, and 1% to 3% of all spinal injuries.


  • Biomechanism: Distraction of C1 lateral masses and failure of the C1 ring at its weakest points adjacent to the lateral masses due to axial loading of occiput.


  • Isolated posterior arch followed by anterior arch fractures are most common and are managed conservatively with excellent union rates.


  • Isolated burst fractures (including classic Jefferson fracture) are second most common and seldom cause neurologic injury because the anatomy and mechanism of injury force the fragments away from the spinal canal.


  • Injuries to transverse ligament are common and can occur without bony injury. Unless the occipital condyles are fractured, other ligaments are spared.


  • Modified Jefferson Classification:



    • Type I: Posterior arch alone, most common (67%), bilateral, nondisplaced, and stable


    • Type II: Anterior arch


    • Type III: Bilateral posterior arch with unilateral or bilateral anterior arch; includes classic Jefferson burst fracture defined by bilateral fractures of both anterior and posterior arches; usually high-velocity loading mechanism


    • Type IV: Lateral mass; usually medial portion of lateral mass and unilateral; low-velocity loading mechanism


    • Type V: Transverse fractures of anterior arch, usually horizontal and in elderly


  • Forty percent to forty-four percent atlas fractures can occur in combination with axis (C2) or subaxial cervical spine fractures. C2 fractures are usually Type II odontoid or isthmus (hangman’s fractures).


  • Treatment depends upon integrity of the transverse ligament and the presence or absence of other cervical spine injuries.



    • Isolated atlas fractures with intact transverse ligament or associated with avulsion of bony medial tubercle have a good union rate with external immobilization (hard collar vs. halo).


    • Isolated atlas fractures with disruption of mid-portion or nonbony avulsion from medial tubercle cannot heal and are treated with surgical fixation.


  • Imaging:



    • Radiographs include open-mouth odontoid, lateral, and flexion-extension views. CT preferred for complete evaluation. MRI highly sensitive for evaluation of transverse ligament rupture.


    • Displacement of C1 lateral mass over C2 facets suggests burst fracture of atlas.


    • C1 lateral mass overhang upon C2 facets combined on both sides >7 mm (rule of Spence) is suggestive of ruptured transverse ligament. However, rule of Spence can miss transverse ligament disruption from avulsion of medial tubercle.


    • The amount of C1 lateral mass overhang is important for surgical planning and fixation approach (transarticular vs. lateral mass).


    • Atlantodental interspace >3 mm in adults and >5 mm in children highly suggestive of ruptured transverse ligament.


    • Retropharyngeal soft tissue swelling at C1-C3 suggestive of anterior arch fracture.







FIGURE 2-9. Jefferson fracture. (A) Mechanism of injury for Jefferson fractures. (B) Anteroposterior (AP) open-mouth odontoid view shows displacement of the lateral masses outward (arrows). The extent of injury is best appreciated on the axial (C) and coronal (D) computed tomography (CT) images.







FIGURE 2-10. Hyperextension injury C1. Lateral radiograph of the upper cervical spine demonstrates an avulsion fracture of the anterior arch of C1 (arrow).



SUGGESTED READING

Dickman CA, Douglas RA, Sonntag VKH. Occipitocervical fusion: posterior stabilization of the craniovertebral junction and upper cervical spine. BNI Q. 1990;6(2):2-14.

Hadley MN, Dickman CA, Browner CM, et al. Acute traumatic atlas fractures: management and long term outcome. Neurosurgery. 1988;23(1):31-35.

Harris JH, Mirvis SE. The Radiology of Acute Cervical Spine Trauma. 3rd ed. Baltimore: Williams and Wilkins; 1996:340-366.

Jackson RS, Banit DM, Rhyne AL, et al. Upper cervical spine injuries. J Am Acad Orthop Surg. 2002;10:271-280.

Kakarla UK, Chang SW, Theodore N, et al. Atlas fractures. Neurosurgery. 2010; 66(suppl 3):A60-A67. doi:10.1227/01.NEU.0000366108.02499.8F.

Mead LB, Millhouse PW, Krystal J, et al. C1 fractures: a review of diagnoses, management options, and outcomes. Curr Rev Musculoskelet Med. 2016;9(3):255-262. doi:10.1007/s12178-016-9356-5.



▪ TRAUMA: CERVICAL SPINE—ATLANTOAXIAL DISLOCATIONS


KEY FACTS



  • Traumatic dislocations of the atlantoaxial axis are rare.


  • The transverse ligament assists in maintaining the normal C1-C2 relationship. Subluxations may occur with conditions that affect the normal osseous or ligamentous integrity (rheumatoid arthritis, retropharyngeal infection, congenital abnormalities, and trauma).


  • Traumatic subluxation/dislocation may be anterior, posterior, or rotary in nature.


  • Normally, the space between the odontoid and lower anterior arch of C1 is 2 mm in adults and 4 mm in children.


  • Imaging can be accomplished with lateral and open-mouth odontoid views. However, thin-section CT with reformatting or three-dimensional reconstruction is most accurate for detection and classification.






FIGURE 2-11. (A) Lateral radiograph of the upper cervical spine demonstrates anterior subluxation of C1 on C2. Odontoid-C1 and posterior arch relationships (dotted lines). (B) Axial computed tomography (CT) image demonstrates an anterior arch fracture (arrow) and avulsion (arrowhead) of the transverse ligament.







FIGURE 2-12. Rotary subluxation/fixation. Skeletal specimens with metal markers on the C2 facet demonstrate normal (A) and rotary fixation (B) of C1 on C2. Axial computed tomography (CT) (C) and three-dimensional surface rendered reconstructions, caudocranial (D) and craniocaudal (E) views show rotary fixation. The rotation of C1 (solid line) in relation to C2 (broken line) and (O) odontoid process in (C).







FIGURE 2-12. (continued)



SUGGESTED READING

Fielding JW, Hawkins RJ. Atlantoaxial rotary fixation. J Bone Joint Surg. 1977;57A:37-44.

Neumann U, Urbanski H, Riedel K. Posterior atlantoaxial dislocation without fracture of the odontoid. J Bone Joint Surg. 2003;85A:1343-1346.



▪ TRAUMA: CERVICAL SPINE—AXIS (C2)


KEY FACTS



  • Fractures of C2 are common, accounting for 15% to 27% of cervical spine injuries (Table 2-4). Up to 25% have associated lower cervical fractures. Odontoid fractures account for 75% of cervical spine injuries in children.


  • Ossification of the dens completes by 12 years of age; this must be considered in pediatric trauma cases.


  • Fractures of the odontoid and neural arch (hangman’s fracture) account for 80% of C2 fractures.


  • Odontoid fractures are classified by location (Table 2-5). Fractures of the base of the odontoid (Type II) have a high incidence of nonunion (54% to 67%) and instability.


  • Hangman’s fractures (neural arch) are hyperextension injuries.


  • Posterior C1-C2 fixation methods have a high fusion rate.


  • Anterior odontoid screw placement is contraindicated in cases of chronic fracture, disruption of transverse ligament, or angulated displacement of dens.








Table 2-4 AXIS (C2) FRACTURES


















Location


Incidence (%)


Odontoid


41


Hangman’s


38


Anterior inferior body


13


Lamina, spinous process


8









Table 2-5 ODONTOID FRACTURE CLASSIFICATION



















Type


Incidence (%)


Complications


I, odontoid tip


8


None


II, odontoid base


59


Nonunion 54%-67%


Neurologic 20%


III, below odontoid


33


Nonunion in 40% if displaced >5 mm








FIGURE 2-13. (A) Odontoid fracture classification: Type I—odontoid tip; Type II—odontoid base, above accessory ligament and vascular supply (arrows); and Type III—extend into body below vascular supply. Sagittal and coronal computed tomography (CT) images; (B, C) Type I (chronic) fracture; (D, E) Type II fracture with posterior subluxation of C1 and displacement of the odontoid process; and (F, G) Type III fracture.







FIGURE 2-14. Hangman’s fracture with anterior displacement of C2 on C3 on lateral radiograph (A) and sagittal computed tomography (CT) image (B). Fracture of bilateral C2 pars on axial CT (C).







FIGURE 2-15. Anterior inferior body fracture of C2 (arrow).



SUGGESTED READING

Berquist TH. Imaging of Orthopedic Trauma. 2nd ed. New York: Raven Press; 1992:93-206.

Jackson RS, Banit DM, Rhyne AL, et al. Upper cervical spine injuries. J Acad Orthop Surg. 2002;10:271-280.

Sim HB, Lee JW, Park JT, et al. Biomechanical evaluations of various C1-C2 posterior fixation techniques. Spine. 2011;36:E401-E407.



▪ TRAUMA: CERVICAL SPINE—LOWER CERVICAL SPINE: VERTEBRAL ARCH FRACTURES


KEY FACTS



  • Vertebral arch fractures are most frequently the result of hyperextension or lateral flexion injuries. Common sites and incidences in our experience are as follows:





















    Lamina


    28%


    Pedicle


    25%


    Spinous process


    22%


    Pillar


    16%


    Facets


    9%


    Transverse process


    2%



  • Laminar fractures are commonly associated with spinous process fractures. The majority occur from C5-C7.


  • Pedicle fractures may occur at C2 (hangman’s) or in the lower cervical spine. If nondisplaced, they may be easily overlooked on routine radiographs.


  • Spinous process fractures are most common from C5-T1. Injury may be the result of direct trauma, hyperextension, or hyperflexion.


  • Pillar fractures without displacement may be overlooked on radiographs. They are most common at C6.


  • Facet fractures are the result of flexion-rotation or hyperflexion injuries.


  • Transverse process fractures occur with direct trauma or lateral flexion, and are managed conservatively.


  • In general, isolated nondisplaced posterior element fractures have a high spontaneous union rate and are managed conservatively with bracing unless there is neurologic compromise.


  • Displaced fractures of the facet or pedicle are treated with surgical fixation; however, conservative treatment may be attempted.


  • Transverse process fractures are stable; however, it is important to assess for potential vertebral artery injury secondary to transverse foramen compromise (40% incidence).






FIGURE 2-16. Computed tomography (CT) image of a remote fracture of the left transverse process through the foramen transversarium (arrows).







FIGURE 2-17. Sagittal computed tomography (CT) image of a C5 facet fracture (arrow).






FIGURE 2-18. Spinous process fracture at C7 (Clay shoveler’s fracture). (A) Anteroposterior (AP) view shows a double spinous process (arrows). This is a helpful sign because the lower cervical spine is often difficult to visualize on the lateral view. (B) Lateral view shows the C7 spinous process fracture clearly in this case.




SUGGESTED READING

Berquist TH. Imaging of adult cervical spine trauma. Radiographics. 1988;8:667-694.

Harris JH, Mirvis SE. The Radiology of Acute Cervical Spine Trauma. 3rd ed. Baltimore: Williams and Wilkins; 1996:408-419.

Inamasu J, Guiot BH. Vertebral artery injury after blunt cervical trauma: an update. Surg Neurol. 2006;65:238-245, discussion 245-246.

Kotani Y, Abumi K, Ito M, et al. Cervical spine injuries associated with lateral mass and facet joint fractures: new classification and surgical treatment with pedicle screw fixation. Eur Spine J. 2005;14:69-77.

Lee SH, Sung JK. Unilateral lateral mass-facet fractures with rotational instability: new classification and a review of 39 cases treated conservatively and with single segment anterior fusion. J Trauma. 2009;66:758-767.

Torg JS, Sennett B, Vegso JJ, et al. Axial loading injuries to the middle cervical spine segment. An analysis and classification of twenty-five cases. Am J Sports Med. 1991;19:6-20.



▪ TRAUMA: CERVICAL SPINE—LOWER CERVICAL SPINE: VERTEBRAL BODY FRACTURES


KEY FACTS



  • More than 31% of cervical spine injuries involve the vertebral body. Seventy-five percent of fractures occur from C5-C7.


  • Flexion teardop fractures (avulsion injuries of inferior vertebral body) may have a benign appearance on plain radiographs; however, they have a high rate of spinal cord injury and are unstable injuries.


  • Burst fractures usually occur in the lower cervical spine and have a high incidence of neurologic injury; however, they may be managed conservatively with bracing if there is no ligamentous disruption.


  • Ligamentous disruption can be hidden by spontaneous reduction in plain radiographs taken in the supine position.


  • Table 2-6 summarizes vertebral body fractures.








Table 2-6 VERTEBRAL BODY FRACTURES
































Type


Mechanism of Injury


Comments


Chip fractures


Hyperextension (anterior inferior body)


Hyperflexion (anterior superior body)


Usually stable


Teardrop fractures


Hyperflexion neurologic injury


Quadriplegia in 87%



Hyperextension


C2 most common


Compression fracture


Flexion-compression


Look for posterior soft tissue injuries


Lateral wedge, uncinate process


Asymmetric vertical compression


Burst fractures


Vertical compression


CT to assess spinal canal


CT, computed tomography.







FIGURE 2-19. Flexion-compression injury with compression of C7 and an anterior chip fracture (open arrow). There is widening of the interspinous distance (arrow) indicating posterior ligament injury and instability.







FIGURE 2-20. Teardrop fractures. (A) Hyperextension teardrop of C4. Note the posterior arch fractures of C2 and C3 (arrows) indicating the mechanism of injury. (B) Hyperflexion teardrop fracture of C5 with compromise of the spinal canal (dotted lines) and posterior ligament tears (double arrow)—finding best seen on sagittal computed tomography (CT) image (C). Axial CT (D) shows the sagittal fracture commonly seen with flexion teardrop fracture.







FIGURE 2-21. Axial (A) and sagittal (B) computed tomography (CT) images show chronic C5 vertebral body burst fracture with retropulsion which mildly narrows the spinal canal. Also noted are chronic compression deformities of C6 and C7 vertebral bodies and a nonunited Type II odontoid fracture.



SUGGESTED READING

Berquist TH. Imaging of Orthopedic Trauma. 2nd ed. New York: Raven Press; 1992:93-206.

Dvorak MF, Fisher CG, Fehlings MG, et al. The surgical approach to subaxial cervical spine injuries: an evidence-based algorithm based on the SLIC classification system. Spine. 2007;32:2620-2629.

Kwon BK, Vaccaro AR, Grauer JN, et al. Subaxial cervical spine trauma. J Am Acad Orthop Surg. 2006;14:78-89.

Lauweryns P. Role of conservative treatment of cervical spine injuries. Eur Spine J. 2010;19(suppl 1):S23-S26.

Sanchez B, Waxmann K, Jones T, et al. Cervical spine clearance in blunt trauma: evaluation of a computed tomography-based protocol. J Trauma. 2005;59:179-183.



▪ TRAUMA: CERVICAL SPINE—LOWER CERVICAL SPINE: SUBLUXATION, FRACTURE/DISLOCATION


KEY FACTS



  • Most significant ligament injuries involve the posterior column. Seventy-three percent occur at the C5-C7 levels. Anterior ligament injuries are most common at C2-C4 and C6-C7. Ligament injuries may occur alone or with fractures.


  • The spectrum of injuries may be subtle, without obvious abnormality and normal bony alignment, or injuries may be grossly obvious, such as bilateral locked facets.


  • Unilateral facet locking or perching may present with subtle radiographic findings. This flexion-rotation injury accounts for 12% of cervical injuries. Reformatted CT imaging is often required for detection and complete evaluation of these injuries.


  • Flexion-distraction injuries may present with acute spinal cord injury, radiculopathy, or both.


  • Magnetic resonance (MR) should be performed in stable patients who have suspected ligamentous injury and inconclusive findings on CT.


  • Ligamentous injury (anterior longitudinal ligament [ALL] and posterior longitudinal ligament [PLL]) is an unstable injury, and open reduction/internal fixation is indicated.






FIGURE 2-22. Flexion-distraction injury with posterior ligament tear at C5-C6. Flexion (A) and extension (B) views show subluxation and widening of the interspinous distance and facet joints with flexion that reduces with extension. Treatment—posterior fusion.







FIGURE 2-23. Unilateral locked facet. (A) Anteroposterior (AP) radiograph shows disc space asymmetry (arrow) at C4-C5 and rotation of the spinous process. (B) Lateral view shows subluxation, and the C4 facets form the “bow-tie” sign. (C) Oblique view shows the facet overlap (arrow).







FIGURE 2-24. Sagittal computed tomography (CT) images of locked (A) and perched (B) facets (arrow).







FIGURE 2-25. Lateral radiograph (A) demonstrates bilateral locked facets at C5-C6 with a chip fracture (arrow) of C6. Subluxation with bilateral locked facets must be equal or greater than 50%. Sagittal T2 magnetic resonance imaging (MRI) (B) in another patient with bilateral facet dislocation demonstrates spinal cord impingement, ligamentum flavum, and interspinous ligament injury (black arrows) with resultant fanning of the C6 and C7 spinous processes. Quadriplegia occurs in 72% of patients with this injury.



SUGGESTED READING

Brodke DS, Anderson PA, Newell DW, et al. Comparison of anterior and posterior approaches in cervical spinal cord injuries. J Spinal Disord Tech. 2003;16:229-235.

Harris JH, Mirvis SE. The Radiology of Acute Cervical Spine Trauma. 3rd ed. Baltimore: Williams and Wilkins; 1996:270-276, 291-304.

Scher AT. Anterior cervical subluxation: an unstable position. Am J Roentgenol. 1979;133:275-280.

Vaccaro AR, Hulbert RJ, Patel AA, et al. The subaxial cervical spine injury classification system: a novel approach to recognize the importance of morphology, neurology, and integrity of the disco-ligamentous complex. Spine. 2007;32:2365-2374.

Vaccaro AR, Nachwalter RS. Is magnetic resonance imaging indicated before reduction of a unilateral cervical facet dislocation? Spine. 2002;27:117-118.



▪ TRAUMA: THORACOLUMBAR SPINE—BASIC CONCEPTS


KEY FACTS



  • Because of differences in range of motion, transition in the facet joints, and other anatomic factors, the thoracolumbar junction is most susceptible to injury (66% of injuries occur between T12 and L2).


  • Mechanism of injury



    • Hyperflexion (most common)


    • Flexion-compression


    • Flexion-distraction


    • Flexion-rotation


    • Lateral flexion


    • Vertical compression


    • Hyperextension


    • Shearing/rotation forces


  • Complete evaluation of bone and soft tissue structures is essential to assess stability.


  • Thoracolumbar spine injuries are classified on the basis of radiographic and CT features.


  • Instability: Three-column approach of Denis is most useful. If two columns (Fig. 2-26) are involved, the injury is unstable.


  • Image evaluation: Routine radiographs remain the primary screening tool for thoracolumbar fractures. However, CT is almost 100% sensitive for fracture detection compared with 32% for radiographs. CT is also useful to fully evaluate fragment position and spinal canal compromise. MRI is useful in selected cases to evaluate the cord, nerve roots, and soft tissue injuries. Unsuspected posterior ligament injuries are evident on MRI, when not seen on radiographs or CT.

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Oct 17, 2018 | Posted by in MUSCULOSKELETAL IMAGING | Comments Off on Spine
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