Imaging of spinal trauma

1. Imaging of spinal trauma Dr. Vishal Sankpal

2. Imaging modalities • Radiography • Computed Tomography (CT) • MRI

3. The three-view radiography series • antero-posterior, • lateral, and • open mouth odontoid is still the imaging modality of choice as initial study for symptomatic patients ( as recommended by the American College of Radiology Appropriateness Criteria and the Advanced Trauma Life Support (ATLS) course of the American College of Surgeons )

4. Special consideration regarding radiation dose due to the inherent radio-sensitivity of developing tissues in children compared to adults • Antero-posterior (AP) and lateral radiographs under the age of 4 • AP, lateral and open mouth radiographs from 4 to 8 years old • Children at 9 years of age and older are imaged with the adult protocol. This is the approximate age at which the fracture patterns revert to the adult patterns. • CTis reserved for those subjects in whom an abnormality is identified on radiography.

5. Plain Film Radiography and CTof the Cervical Spine: Normal Anatomy

6. Flexion-extension radiographs are not very helpful in the acute setting because muscle spasm in acutely injured patients precludes an adequate examination • Flexion-extension radiographs are helpful for ensuring that minor degrees of anterolisthesis or retrolisthesisin patients with cervical spondylosisare fixed deformities

8. 1 – Anterior spinal line 2 – Posterior spinal line 3 – Spino-laminar line

9. Spinolaminarline – • Any displacement in this line may be an indication of subtle traumatic vertebral injury/dislocation. • A line drawn through C1- 3 spinolaminar lines should intercept the C2 spinolaminarline. • A displacement of the C2 spinolaminar line of more than 2 mm, compared with a line drawn between the spinolaminar lines of C1 and C3, is abnormal.

10. Basion dental interval (BDI) - the basion (white dot) should lie within 12 mm of the top of the odontoid process The basion-axial interval (BAI) - the PAL (white line) should lie within 12 mm of the basion

11. Basion dental interval The basion-axial interval Normal < 12 mm

12. Concept initially evolved from a retrospective review of thoracolumbar spine injuries and observation of spinal instability, it has also been applied to the cervical spine. • The posterior column consists posterior ligamentous complex. • The middle column includes the posterior longitudinal ligament, posterior annulus fibrosus, and posterior wall of the vertebral body. • The anterior column consists of the anterior vertebral body, anterior annulus fibrosus, and anterior longitudinal ligament. Three-column concept of the spine (Denis)

13. Anterior Atlanto-dental interval (AADI) • does not normally exceed 3 mm in adults and 5 mm in children • In adults, because of maturity of the transverse atlantal ligament, the AADI remains constant in flexion and extension. • In infants and children until the age of approximately 8 years, the AADI varies in width in flexion and extension.

14. Diameter of the spinal canal • Difficulties in making accurate measurements secondary to differences in magnification or focal spot-film distance. • This problem can be overcome by comparing the AP width of the canal with that of the vertebral body(canal / body) • The normal ratio of the spinal canal (white arrow) to the vertebral body (black arrow) is 0.8 or more.

15. The normal atlanto-axial articulation in open- mouth odontoid view • The lateral margins of the lateral atlanto-axial joints are symmetric and are on essentially in the same vertical plane, plus or minus 1 mm.

17. Cervical spine injuries - classification Location - • Upper cervical injuries - include injuries to the base of the skull (including the occipital condyles or C0), C1, and C2. • Lower cervical injuries (sub-axial) - include injuries from C3 through C7

18. Cervical spine injuries - classification • Vector forces – Flexion Flexion-rotation Lateral flexion Extension Extension-rotation Vertical compression

19. Stability versus Instability • When assessing stability in the spinal column, the three-column theory of Denis suggests that if two columns have failed, the spinal column is unstable.

20. Occipital condyle fractures • OCF are rare, being found at postmortem examination in 1% to 5% of patients who had sustained trauma to the cervical spine and head • Clinical manifestations of OCF are highly variable • Not typically shown with conventional radiography

21. Plain film findings: Difficult diagnosis due to overlapping of the bony structures of the face, upper cervical spine, and skull base. • May be visible in open-mouth views that include the condyles • OCF are readily identified on axial or coronal reformatted CT

22. Anderson-Montesano classification system (for OCF): • ▪ Type I: Loading fracture of the occipital condyle, typically comminuted and in a vertical sagittal plane, but where there is no fracture displacement or associated craniocervicalinstability. • ▪ Type II: Skull-base fracture that propagates into one or both occipital condyles • ▪ Type III: Infero-medial avulsion fracture of the condyle by the intact alar ligament, with medial displacement of the fragment into the foramen magnum. Type III OCF are considered potentially unstable because of an avulsed alar ligament

23. Type I Type II Type III

24. UNSTABLE: • ▪ Occipital condyle fragment displacement >5 mm • ▪ Occipito-atlantaldislocation • ▪ Bilateral occipital condyle fractures

25. Atlanto-occipital Dislocation • Atlanto-occipital dislocation (AOD) is an uncommon injury that involves complete disruption of all ligamentous relationships between the occiput and the atlas • Stability and function of the atlanto-occipital articulation are provided by the cruciate ligament, tectorial membrane, apical dental ligament, and paired alar ligaments, as well as the articular capsule ligaments • Death usually occurs immediately from stretching of the brainstem, which can result in respiratory arrest

26. The lateral cervical spine radiograph is most likely to reveal the injury • Sagittal CT reconstructions or sagittal magnetic resonance imaging (MRI) can allow for the diagnosis when plain radiography is inconclusive. Atlanto-occipital Distraction • >12 mm Basion Dental distance • Separated occipital condyle and superior surface of C1

27. Atlas (C1) Fractures • Generally related to axial loading • Neurologic compromise is relatively infrequent with fractures of the C1 ring, presumably because the axial compression mechanism results in a burst configuration with expansion of the spinal canal • Jefferson Fracture • Lateral Mass (C1) Fracture • Isolated Fractures of C1

28. Jefferson Fracture • Classically, a four-point injury with fractures occurring at the junctions of the anterior and posterior arches with the lateral masses, the weakest structural portions of the atlas • Most commonly there are two fractures in the posterior arch (one on each side) and a single fracture in the anterior arch, off the midline • Mechanism - A JF is created by sudden and direct axial loading on the vertex. The lateral articular masses of the atlas become compressed between the occipital condyles and the superior articular facets of the axis. By its nature, this is a decompressive injury because the bony fragments are displaced radially away from the neural structures

29. Jefferson Fracture Most common

30. Plain film findings: Open-mouth odontoid view - ▪ Bilateral offset or spreading of the lateral articular masses of C1 in relation to the apposing articular surfaces of C2 ▪ It is often difficult to visualize the lines of fracture per se Lateral view: (difficult diagnosis on the lateral view) ▪ Increase in the atlanto-axial distance (>3 mm) ▪ Anterior or posterior displacement of the C1 spino-laminar line ▪ The retropharyngeal soft tissue may be abnormal in both contour and thickness

31. Jefferson fracture Normal

32. CT findings - • Axial images: ▪ Identify and establish the sites and number of C1 ring fractures ▪ Establish separation between fracture fragments of the atlas, if >7 mm the lesion is considered unstable • Coronal reconstruction: ▪ Assess offset or spreading of the lateral articular masses of C1 in relation to the apposing articular surfaces of C2 • Sagittal reconstruction: ▪ Assess increase in the atlanto-axial distance (>3 mm) and anterior or posterior displacement of the C1 spino-laminar line

33. Unstable (on CT) - An unstable JF is one in which the transverse ligament is disrupted. • Coronal reconstructions: ▪ Total C1 lateral masses offset of the two sides in excess of 7 mm (adding the amount of lateral displacement of each C1 lateral mass) • Sagittal reconstructions: Increase in the atlantoaxial distance (>3 mm) • Axial views: >7 mm separation between fracture fragments of the atlas ▪ Because multilevel fractures (C1 and C2) are considered unstable, a cautious search for contiguous fractures is critical

34. Lateral Mass (C1) Fracture • Usually occur as a result of a lateral tilt • May be limited to the lateral mass of C1, or more commonly, occurs in association with occipital condyle fractures and/or fracture of the articular process of C2 • Usually visible on the open-mouth view • However, sometimes the abnormal cervico-cranial prevertebral soft tissue contour is the only sign of injury in plain films • A fracture of the lateral mass of C1 is considered unstable

35. Lateral Mass (C1) Fracture

36. Isolated Fractures of C1 • usually stable • should be distinguished from the Jefferson bursting fracture and its variants • The most common isolated fracture of C1 is a bilateral vertical fracture through the posterior neural arch • Carries no risk of neurologic deficit • This fracture must be distinguished from developmental defects

37. smooth margins of a partially non-ossified posterior atlas ring Isolated fracture of posterior arch

38. Axis (C2) Fractures • Approximately 25% are hangman fractures, over half (58%) are odontoid fractures, and the remainder are miscellaneous fractures involving the body, lateral mass, or spinous process • Hangman Fracture (Traumatic Spondylolisthesis of C2) • Odontoid Fractures • C2 Lateral Body Fractures

39. Hangman Fracture (Traumatic Spondylolisthesis of C2) • Mechanism – • most common form of this injury results from extension combined with axial loading • Hangman fracture is a bilateral fracture through the pars interarticularis of C2 • The pars interarticularis is found between the superior and inferior articular processes of C2 • Spinal cord damage is uncommon, despite frequent significant fracture displacement, due to the wide spinal canal at this level

40. Plain film findings - • Lateral view: The fracture usually is diagnosed readily on the lateral radiograph in >90% of cases unless non-displaced. ▪ Prevertebral soft tissue swelling or hematoma, often absent ▪ Fractures are often anterior to the inferior facets. They are oblique, extending from superior/posterior to inferior/anterior ▪ Positive axis ring sign, which will show posterior ring disruption from atypical fractures extending into the posterior C2 vertebral body cortex ▪ “Fat C2 sign” ▪ Posterior displacement of the C2 spino-laminar line of >2 mm, ▪ An avulsion fracture of the anterior margin of the axis or anterior superior margin at C3 is often present and identifies the site of rupture of the anterior longitudinal ligament • AP view: Usually not visible on AP cervical spine radiograph.

41. CT findings - CT is valuable to exclude or verify fracture line extension into the vertebral foramina or vertebral body, or to detect subtle concurrent adjacent injuries. • Axial images: ▪ Identify the sites of C2 ring fractures and extension into the vertebral foramina or vertebral body. ▪ Establish separation between fracture fragments of the pars inter-articularisof C2 • Sagittal reconstruction: ▪ Assess the fractures lines and posterior displacement of the C2 spinolaminar line ▪ Assess C2-3 disc space ▪ Establish separation and angulation between fracture fragments of the pars interarticularis of C2

42. Fat C2 sign C2 ring sign

43. Classification of the hangman fracture • Type I fracture - an isolated “hairline” fracture, with < 3 mm fragment displacement, < 15-degree angle at the fracture site, and normal C2-3 disc space • Type II injuries - > 3 mm of fragment displacement or more than a 15-degree angle at the fracture site and an abnormal C2-3 disc space • Type III consists - changes that characterize type II injury + C2-3 articular facet dislocation

44. Type I hangman fracture

45. Type II hangman fracture

46. Type III hangman fracture

47. Odontoid Fractures Classification of dens fractures (Anderson and D'Alonso) - based upon the location of the fracture site with respect to the dens • Type I - an oblique fracture of the superior lateral aspect of the dens, avulsed by the alar (“check”) ligament; this is an extremely uncommon injury, occurring in < 4% of odontoid fractures • Type II- fracture at the base of the dens (most common - comprising 60% of dens fractures) • Type III - an oblique fracture of the superior portion of the axis body caudal to its junction with the base of the dens

48. Odontoid fractures

49. Odontoid FracturesPlain film findings - The radiologic diagnosis of odontoid fractures usually is established using the lateral cervical and open-mouth odontoid view radiographs. • Open-mouth odontoid view: • Type II odontoid fractures - transverse or oblique transverse fracture through the lower portion of the dens. The transverse fracture at the base of the dens must be differentiated from a developmental abnormality termed as os odontoideum. • Os odontoideum is rounded, has a cortical margin around its entire surface, and is usually more widely separated from the base of the odontoid than a fracture, and with smooth margin. Nonunion odontoid fractures may be impossible to distinguish from an os odontoideum.

50. Lateral view: (Difficult diagnosis on the lateral view) • Minimal displacement often precludes demonstration of the fracture line. • Positive axis ring sign will show posterior or anterior ring disruption in type III fractures • Type III fractures are almost always better visualized on the lateral projection and may not be evident on the anteroposteriorview • Anterior or posterior displacement of the C2 spinolaminar line of >2 mm • “Fat C2 sign” in type III fractures