Anatomy Interpretation of Cervical Spine Radiographs Amy Gutman

Anatomy & Interpretation of Cervical Spine Radiographs Amy Gutman MD Chief of Emergency Medicine prehospitalmd@gmail. com

Objectives • Interdepartmental QA project to improve diagnostic accuracy & decrease number of reflexive send‐outs for radiology reads of commonly ordered radiographs • Review basic cervical spine anatomy & “radiologic anatomy” • Interpretation of the most common cervical spine radiographic views • Review of common fractures seen on plain radiographs

Interpretation AABCDS • What views to order? • Plain film: Lateral/AP/odontoid views • CT: Axial, sagittal, coronal slices • • • A = Adequacy A = Alignment B = Bone C = Cartilage D = Disc S = Soft tissue

Who Gets Imaging? NEXUS • Radiography indicated unless following criteria met: • No posterior midline C‐spine tenderness • No intoxication • Normal level of alertness • No focal neurologic deficit • No painful distracting injuries

Imaging? ~ Canadian CSpine Rule • High‐risk: • • • MVA >100 km/hr Fall >3 ft/>5 steps Axial compression injury Focal neurology Predisposing medical condition

CT vs Plain Radiographs • CT commonly performed for high sensitivity, wide availability & acquisition speed • CT recommended: • Clinical suspicion of injury, even if normal X‐ray • Inadequate plain film • Suspicious plain film • Fracture on plain X‐rays • Radiographs screening tool for low‐risk patients & the focus of this educational module

Cervical Spine Stability • Provided by anterior & posterior columns • 1 of 2 columns intact = stable • Both columns disrupted = unstable • Anterior column: • Vertebral bodies • Disc spaces • Anterior & posterior longitudinal ligaments • Annulus fibrosus • Posterior column: • Pedicles • Facets & apophyseal joints • Laminar spinous processes • Posterior ligament complex

AABCDS ~ Adequate? • All 7 vertebrae & C 7‐T 1 junction • Correct density to show soft tissue & bony structures

AABCDS ~ Alignment (4 Parallel Lines) • Anterior vertebral line • Anterior margin of vertebral bodies • Posterior vertebral line • Posterior margin of vertebral bodies • Spinolaminar line • Posterior margin of spinal canal • Posterior spinous line • Tips of the spinous processes • Lines have smooth / slight lordotic curve, without step‐off • Malalignment raises suspicion of ligamentous injury or fracture

Lateral View • Initial trauma x‐ray • 80% unstable cervical spine injuries detected with this single view

Lateral View ~ Anterior Alignment • Bodies form smooth anterior curve • Degenerative changes make interpretation difficult • Bone chips off superior vertebral body = ligamentous injury • Bone chip off inferior vertebral body = “tear‐drop sign” • Unstable with potential cord injury • Malalignment of odontoid process with body of C 2 = odontoid fracture

Lateral View ~ Anterior Subluxation • Disruption of posterior ligamentous complex secondary to hyperflexion • 20%‐ 50% with delayed instability • Flexion & extension views required • Radiographic features: • • • Loss of normal cervical lordosis Anterior displacement of vertebral body Fanning of the interspinous distance Associated compression fracture >25% Abnormal disk space

Lateral View ~ Posterior Alignment • Subluxation of vertebral body, bony fragments, or intervertebral disks into spinal canal • Narrowed disk space suspicious for disk extrusion into the spinal canal • C 7 often subluxed on T 1 • Must visualize this junction • Swimmer’s view if area not seen on standard lateral x‐ray • C 1 burst fracture (“Jefferson Fracture”) rare but potentially fatal with posterior alignment abnormalities

Anterior-Posterior (AP) Alignment • AP view alignment evaluated using edges of vertebral bodies & articular pillars • Cervical vertebral body height & height of joint spaces roughly equal at all levels • Spinous process should be midline & aligned

AABCDS ~ Bones* (Anatomy) • • • Vertebral bodies Pedicles Facet joints Lamina Spinous processes

Atlas ~ C 1 • Articulates with occipital condyle superiorly & axis inferiorly • Atlanto‐occipital articulation important for neck flexion & extension Axis ~ C 2 • Dens articulates with C 1 to form median altantoaxial joint • Atlas‐axis articulation important in neck lateral rotation

Bony Anatomy ~ C 3 -7 • Vertebral body equal in height anteriorly & posteriorly • Vertebra articulates with next vertebra at the body & articular processes • Vertebral artery passes through transverse foramen

Radiographic Anatomy

Bony Landmarks • Vertebral bodies should line up with a gentle arch (lordosis) • Each body rectangular & similar in size • Anterior height 1‐ 3 mm less than posterior height

Lateral Bony Landmarks • Pedicles project posteriorly to support articular pillars, forming intervertebral foramen superior & inferior margins • Left & right pedicles superimposed • Articular pillars are osseous masses connected to posterolateral vertebral bodies via pedicles • Facet joints formed between each lateral mass • Lateral masses rhomboid‐shaped structures projecting downward & posterior • Joint space distance roughly equal at all levels • Spinous processes progressively larger (C 7 > C 1)

Lateral View ~ Pedicles, Laminae, Lateral Masses • Pedicles connect lateral masses to vertebral bodies • Laminae connect lateral masses to spinous processes • Lateral masses articulate with each other at facet joints • If disk & ligaments between two vertebral bodies disrupted, bodies rotate on each resulting in dislocation of one/ both facet joints or “locked facets” • Hangman’s fracture • Fracture through C 2 pedicles & lateral masses of the C 2 vertebral body

Odontoid Anatomy

Odontoid View • Adequate film includes entire odontoid & lateral borders of C 1‐C 2 • Occipital condyles line up with C 1 lateral masses & superior articular facet • Distance from dens to C 1 lateral masses should be equal bilaterally • Asymmetry suggests C 1 or C 2 fracture or rotational abnormality • C 1 lateral mass tips should line up with lateral margins of C 2 superior articular facet • Odontoid should have uninterrupted cortical margins blending with C 2 body

AABCDS ~ Cartilaginous Spaces? • Predental space • Distance from dens to C 1 body • Should not measure >3 mm in adults & 5 mm in children • If space wide, suspect odontoid fracture or disruption of transverse ligament • If fracture suspected: CT • If ligamentous disruption suspected: MRI

AABCDS ~ Disc Spaces? • Roughly equal in height at anterior & posterior margins • Symmetric • Degenerative diseases may lead to spurring & loss of disc height making interpretation difficult

AABCDS ~ Soft Tissue Spaces? • Suspicion for underlying injury if enlarged, requiring further radiographic evaluation with CT / MRI: • Nasopharyngeal space C 1: 10 mm • Retropharyngeal space C 2‐C 4: 5‐ 7 mm • Retrotracheal space C 5‐C 7: 22 mm (adult), 14 mm (children) • C 1‐C 4 < ½ VB width, C 4 onwards <1 VB width • Space between lower cervical vertebrae & trachea < 1 vertebral body • If space between lower anterior border of C 3 & pharyngeal air shadow >7 mm, suspect retropharyngeal swelling / hemorrhage • Indirect sign of a C 2 fracture

COMMON CERVICAL SPINE FRACTURES

Jefferson Fracture • Unstable C 1 ring compression fracture with split lateral masses plus transverse ligament tear • Secondary to axial load (i. e. diving) • Features on “AP Open Mouth”: • Displacement of C 1 lateral masses beyond margins of C 2 vertebral body • Lateral displacement >2 mm or unilateral displacement

Alanto-Occipital Dissociation • Unstable disruption of atlanto‐occipital articulation • Secondary to hyperflexion / hyperextension • Radiographic features: • Malposition of occipital condyles in relation to atlas superior articulating facets • Increased Basion ratio: C 1 spinolaminar to opisthion (C 1 anterior arch posterior cortex) • Cervicocranial prevertebral soft tissue swelling

Alanto-Occipital Dissociation • Anterior margin of foramen magnum lines up with dens • A line projected downward from dorsal sellae along clivus to basion points to dens • Posterior margin of foramen magnum lines up with C 1 spinolaminar line • Check Basion Ratio: • Spinolaminar line of C 1 to Opisthion (C 1 anterior arch posterior cortex) = 0. 6‐ 1. 0 • Ratio >1. 0 implies anterior cranio‐cervical dislocation

Clay Shoveler’s • Stable spinous process fracture • Hyperflexion plus paraspinous muscle contraction pulling on spinous processes • Radiographic features: • Lateral: spinous process fracture • AP View: “Ghost sign” ~ double spinous process of C 6 or C 7 resulting from displaced fractured spinous process

Bilateral Facet Dislocation • Complete anterior dislocation of vertebral body resulting from extreme hyperflexion • Unstable, with high risk of cord damage • Radiographic features (best seen on lateral view): • Complete anterior dislocation of affected vertebral body by >50% of body AP diameter • Disruption of posterior ligament complex & anterior longitudinal ligament • "Bow tie" or "bat wing" appearance of locked facets

Unilateral Facet Dislocation • Facet joint dislocation & rupture of apophyseal joint ligaments resulting from flexion & rotatory injury of the cervical vertebrae • Stable, potential neurologic concerns • Radiographic features (lateral or oblique views): • Anterior dislocation of affected body by <50% • • of the vertebral body AP diameter Discordant rotation above & below involved level Facet within intervertebral foramen on oblique view Widening of the disk space "Bow tie" or "bat wing" appearance of the overriding locked facet

Hangman’s Fracture • Unstable fractures through the axis pars interaticularis from hyperextension & distraction • Radiographic features best seen on lateral view: • Prevertebral soft tissue swelling • Avulsion of C 2 anterior inferior corner associated with rupture of the anterior longitudinal ligament • Anterior dislocation of C 2 vertebral body • Bilateral C 2 pars interarticularis fractures

Odontoid Fractures • Fractures suspected if there is an anterior tilt of the odontoid on lateral view • Lucent fracture line difficult to see unless displaced • Another fracture indication is prevertebral soft tissue swelling

Odontoid Fractures

Teardrop • Unstable anterior compression fracture of vertebral body with posterior ligament disruption • Results from hyperflexion plus compression • Radiographic features: • Prevertebral swelling (anterior longitudinal • • ligament tear) Teardrop fragment (anterior vertebral body avulsion fracture) Posterior vertebral body subluxed into spinal canal Cord compression from vertebral body displacement Spinous process fracture

Wedge Fracture • Vertebral body compression fracture secondary to hyperflexion or compression • Usually stable • Radiographic features • “Buckled” anterior cortex • Anterior body height loss • Vertebral body antero‐superior fracture

Burst Fracture • Vertebral body fracture resulting from axial compression • May injury cord secondary to posterior fragment displacement • CT required to evaluate extent of damage

References • www. med‐ed. virginia. edu/courses. “The Cervical Spine” • www. Up. To. Date. com. “Cervical Spine Anatomy”, “Cervical Spine Radiographs” • Wiki. Medicine. “Cervical Spine Radiography” • Em. Rap. “Spinal Fractures”. Queried May 2017 • Raby, editor. Accident and Emergency Radiology 3 rd Edition. “Spinal Fractures” Saunders. 2015 • Short K. “A point of care guide to interpreting CTs, plain films and rationalizing their use in ED” Queried May 2017 • www. EBMConsult. com. “Cervical Vertebral Anatomy” Queried may 2017

Summary prehospitalmd@gmail. com • Interdepartmental QA project to improve diagnostic accuracy & decrease number of reflexive send‐ outs for radiology reads of commonly ordered radiographs • Review of the basic anatomy & “radiologic anatomy” of the cervical spine • Interpretation of most common cervical spine radiographic views • Review of common fractures seen on plain radiographs