33 vertebrae: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused), and 4 coccygeal (fused)
Supports and protects spinal cord and nerve roots
Denis three-column theory (Figure 9.1)
Anterior two-thirds of vertebral body and annulus
Anterior longitudinal ligament (ALL)
Weight bearing in the erect position
Posterior one-third of vertebral body and annulus
Posterior longitudinal ligament (PLL)
Pedicles, facets, lamina, and spinous processes
Posterior ligamentous complex (PLC)
Paravertebral musculature attachments
Typically, vertebral size increases caudally (more weight supported)
Occipital condyles of the skull articulate with superior facets of the atlas.
Tectorial membrane—extension of PLL
50% of head flexion/extension (˜50°)
No vertebral body
No spinous process
Vertebral arteries travel through transverse foramen and then enter the foramen magnum (to avoid injury, C1 dissection should not be >1.5 cm lateral from the midline in an adult; Figure 9.2).
Odontoid process is the attachment site of the alar and cruciate ligaments.
Transverse bands of cruciate ligament are the most critical for C1-C2 stability.
Bifid spinous process
50% of cervical rotation occurs at atlanto-axial joints (˜50°).
Bifid spinous process except for C7
Vertebral arteries do not travel in C7 transverse foramen.
Subaxial spine contributes to cervical motion: lateral flexion (˜60°), flexion/extension (˜50°), and rotation (50°).
Costal facets articulate with the ribs, providing rigidity.
Normal thoracic kyphosis is 20° to 50°.
Largest transverse processes
Range of motion: flexion/extension (75°), lateral flexion (75°), and rotation (70°)
Normal lumbar lordosis is ˜60° (range, 20°-80°).
Cauda equina begins at L1-L2.
Range of motion: flexion/extension (85°), lateral flexion (30°), and rotation (10°)
Five fused vertebrae
Four pairs of pelvic sacral foramina ventrally and dorsally
Sacral canal opens into sacral hiatus.
Four fused vertebrae
Gluteus maximus muscle
External anal sphincter
Levator ani muscle (including coccygeus)
Synovial joints that facilitate and limit spinal motion: flexion, extension, and rotation
Orientation varies with spinal level.
Thin layer of hyaline cartilage between articulating surfaces
Supports annulus fibrosus
Thick at center of vertebral body and thin at edges
Hourglass shape with wider and thinner sections over disks
Connect laminae of adjacent vertebrae from axis to sacrum
Hypertrophy may exacerbate nerve root compression.
Interconnect pia mater with dura mater
Suspend and provide stability to the spinal cord
Extend down to T12
Continuation of ligamentum nuchae in cervical spine—C7 to sacrum
Limits hyperflexion of the spine
Between adjacent spinous processes
Limits hyperflexion of the spine
Between transverse processes
Limits lateral flexion of the spine
Twenty-three fibrocartilaginous disks starting at C2-C3 and ending at L5-S1
Constitutes 20% to 33% of vertebral column height—aging causes disk dehydration and height decrease
Cross-sectional areas of disks increase craniocaudally. L4-L5 disk space is largest.
At birth, blood vessels that are present at endplates perforate intervertebral disk, extending into the annulus fibrosus.
Normal adult intervertebral disk is avascular, with capillaries terminating at endplates; receives nutrients via passive diffusion.
Outer layer—type I collagen fibers, obliquely oriented
High tensile strength
Superficial fibers of annulus fibrosus innervated by sinuvertebral nerves from dorsal root ganglia
Negatively charged proteoglycans
Type II collagen
Approximately 88% water
High compressive strength
Extrinsic muscular attachments—trapezius, rhomboids, serratus posterior, and latissimus dorsi
Splenius capitis and cervicis muscles
Lateral flexion of neck
Three erector spinae muscles—spinalis, longissimus, and iliocostalis muscles
Trunk extension and lateral flexion
Semispinalis muscles—neck extension
Multifidus and rotatores muscles—stabilize and rotate vertebrae
Spinal cord (Figure 9.4)
Part of the central nervous system
Meninges cover spinal cord
Pia mater (innermost layer)
Arachnoid mater—subarachnoid space (between pia and arachnoid mater)
Filled with cerebrospinal fluid (CSF)
Dura mater (outermost layer)
Terminates with conus medullaris at L1-L2, then transitions into cauda equina
Spinothalamic tracts carry sensory information.
Lateral—pain and temperature
Dorsal—deep touch, vibratory, and proprioception
Corticospinal tracts carry motor information.
Thirty-one pairs of spinal nerves, exit through neural foramina
Cervical roots 1 to 7 exit canal above the pedicle of the corresponding vertebrae and cervical root 8 exits below C7 pedicle.
All other spine roots exit canal below the pedicles of the corresponding vertebrae.
Common deficits by nerve root are shown in Table 9.1.
Twenty-two ganglia—3 cervical, 11 thoracic, 4 lumbar, and 4 sacral
Three cervical ganglia—stellate, middle, and superior
Injury of middle cervical ganglion leads to Horner syndrome.
Ascend through transverse foramen of C6-C1
Table 9.1 Common Deficits by Nerve Root
Shoulder abduction, elbow flexion (biceps)
Elbow flexion (brachioradialis), wrist extension
Thumb, radial forearm
Elbow extension, wrist flexion, finger extension
Small finger, ulnar forearm
Groin, iliac crest
Hip flexion, hip adduction
Hip flexion, hip adduction, knee extension
Knee extension, ankle dorsiflexion
Lateral thigh, anterior knee, medial leg
Ankle dorsiflexion, foot inversion, toe dorsiflexion, hip extension/abduction
Anterolateral leg, dorsal foot
Foot plantar flexion, foot eversion
Posterior leg, lateral foot
Toe plantar flexion
Bowel and bladder function
Branches supply the posterior spinal arteries and the anterior spinal artery.
Unite to form basilar artery
Three vertical arteries
Anterior spinal artery—runs down ventral median fissure
Two posterior spinal arteries—run down dorsal fissures
Enter via intervertebral foramina along with nerve roots
Artery of Adamkiewicz
Largest segmental medullary artery
Commonly left-sided and present between T8 and L1
Damage may cause paralysis
Parallels arterial supply pathways
There are also internal and external venous plexuses.
Assume trauma patients have a cervical spine injury until confirmed otherwise
Immobilize in rigid cervical collar, use spinal board for transport, and log roll for posterior examination
Children: Use specialized board with occipital recess and body pad to maintain spinal alignment.
Often involves high-energy trauma such as motor vehicle accidents, falls from heights, and high-impact sports
Occurs more commonly in those >65 years of age and in men
Assess mechanism of injury and forces involved
Distraction, compression, hyperflexion, hyperextension, lateral flexion, rotational, or translation forces
Distractive forces can cause ligamentous injuries that are not apparent on initial imaging.
C2 is the most commonly fractured vertebra (24%), followed by C6 and C7.
Subaxial spine (C3-C7) accounts for 65% of cervical fractures and 75% of cervical dislocations/subluxations.
Examine for midline bony tenderness.
Complete neurologic examination, including cranial nerves, which can be involved in high cervical spine injuries
Hoffman sign: Flick finger nail and observe for reflexive thumb contraction, which may suggest cervical myelopathy or cord injury.
Romberg sign: Standing patient is asked to close eyes and stand still; swaying or imbalance suggests injury to cerebellum or dorsal column of the spinal cord that mediates proprioception.
In subacute setting, if there is no longer suspicion for fracture or dislocation:
Lhermitte sign: Maximally flex the neck and trunk. Radiating pain down the arms or spine suggests cervical spinal stenosis.
Spurling sign: Patient’s head is extended and rotated to the side of suspected neural impingement and axially compressed. Radiating pain suggests cervical foraminal stenosis.
Cervical spine clearance without radiographic imaging
National Emergency X-Radiography Utilization Study (NEXUS) low-risk criteria
Patient must be awake and alert
Patient cannot be intoxicated
No neurologic deficits
No painful, distracting injuries
No posterior midline cervical spine tenderness
Canadian C-spine rule (CCR)
Absence of all high-risk factors that necessitate radiography
Age ≥65 years
Paresthesias in extremities
Presence of any low-risk factors that suggest range-of-motion testing would be safe
Simple rear-end motor vehicle collision
Sitting position in the emergency department
Ambulatory at any time
Delayed (not immediate) onset of neck pain
Absence of midline cervical spine tenderness
If criteria 1 and 2 are satisfied, test range of motion; if patient can rotate neck actively 45° to the left and right, cervical spine can be cleared without radiography.
CCR has higher sensitivity and specificity for cervical spine injury and decreases radiography rates when compared with NEXUS criteria.
If the cervical spine cannot be cleared clinically, radiographs (anteroposterior [AP], lateral, odontoid views, and swimmer’s view if needed to visualize cervicothoracic junction) and/or computed tomography (CT) should be obtained.
Inspect the following on the lateral cervical spine radiograph: anterior vertebral line, posterior vertebral line, spinolaminar line, and spinous process line (Figure 9.5).
Prevertebral soft tissues are normally ≤6 mm at C2 and ≤18 mm at C6.
Order magnetic resonance imaging (MRI) if there is concern for neurologic or major soft-tissue (eg, ligamentous) injury as MRI provides the best visualization of spinal cord injury, disk herniation, and PLC disruption.
Order magnetic resonance angiography or CT angiography if there is concern for vertebral artery injury.
Select operative versus nonoperative treatment according to specific patient-related factors: previous functional level, medical comorbidities, associated injuries, and the patient’s personal wishes.
Surgical treatment usually aims to:
Reduce spinal cord or nerve root compression
Provide mechanical stability, thereby preventing pain, deformity, and further neurologic injury
Often caused by axial loading of the skull on C1 lateral masses or by lateral hyperflexion injuries
Anderson and Montesano classification
Type I: compression/impaction-type fracture causing occipital condyle comminution
Type II: shear-type fracture extending into the skull resulting from direct blow to the skull
Type III: condylar-alar ligament avulsion fracture resulting from forced rotation and lateral bending
Type I and type II injuries are usually stable and treated with cervical orthosis if there is no fragment displacement into the foramen magnum (alar ligaments and tectorial membrane usually preserved).
Type III injuries are more likely to be unstable, requiring halo immobilization or occipitocervical arthrodesis.
Anterior pin placement when applying a halo should be superolateral to the eyebrow to avoid supraorbital nerve injury.
Usually highly unstable and involves alar ligament and tectorial membrane disruption
Type I: anterior dislocation (occiput translated anteriorly relative to cervical spine)
Type II: longitudinal dislocation (occipital condyles distracted off of atlas)
Type III: posterior dislocation (occiput translated posteriorly relative to cervical spine)
Powers ratio calculated on CT
Powers ratio = (basion to posterior arch of C1 distance)/(anterior arch of C1 to opisthion distance) (Figure 9.6)
Powers ratio >1 is suggestive of anterior dislocation.
Basion-dens interval calculated on CT
Value of 9 to 12 mm also suggestive of atlanto-occipital dissociation
Atlanto-occipital dissociations usually require posterior occipitocervical arthrodesis for maintenance of long-term stability.
Atlanto-dens interval (ADI)
In healthy adults—usually <3 mm for men and <2.5 mm for women
In children <15 years of age—usually <5 mm
Chronic instability can usually be seen on flexion-extension views, although such views would usually be contraindicated after an acute trauma when instability is suspected.
C1-C2 subluxation caused by forced flexion of the neck leads to:
Rupture of the transverse ligament (best seen on MRI) or
Avulsion fracture of C1 lateral mass via pull by the transverse ligament (fragment best seen on CT)
Transverse ligament rupture—often requires C1-C2 arthrodesis because of instability and poor ligamentous healing potential
Avulsion fracture—often treated with halo immobilization because of potential for osseous healing of C1 lateral mass avulsion fracture
Atlanto-axial rotatory subluxation
Caused by combined rotatory and flexion or extension forces; can occur spontaneously without any clear trauma
Fielding classification assesses:
Pivot point (odontoid or facet)
Transverse ligament competence
In about half of cases, the odontoid serves as the pivot point, the transverse ligament remains intact, and the ADI is <3 mm. Treat with gradual cervical halter traction with patient supine.
Rarely necessitates C1-C2 arthrodesis
Caused by high-energy axial loads
Anterior arch fractures
Posterior arch fractures
Transverse process fractures
Lateral mass fractures (often comminuted)
Burst fractures (ie, Jefferson fractures): combined anterior and posterior arch fractures
If isolated, C1 fractures are usually not associated with spinal cord injury because of the large space available for the cord at this level.
Most fractures can be treated in cervical orthosis or halo immobilization if the transverse ligament remains intact.
Burst fractures (ie, Jefferson fractures; Figure 9.7)
Usually involve lateral mass displacement away from the spinal canal
On odontoid radiographic view, if C1 right and left lateral mass overhang distance (compared with C2) is greater than 7 to 8 mm, then the transverse ligament is considered ruptured and the fracture is deemed unstable; this necessitates C1-C2 arthrodesis (or occipitocervical arthrodesis if inadequate C1 bony purchase).
Odontoid process fractures (˜50% of C2 fractures)
Lateral mass fractures
Pars fractures (also known as “Hangman’s fracture”)
Odontoid process fractures (Figure 9.8)
Result from hyperextension or hyperflexion injuries
Classified in relation to watershed area at the base of the dens, from which the odontoid process receives its vascular supply
Figure 9.8 Odontoid process fractures. From Morgan RA. Acute management of spine trauma. In: Swiontkowski MF, ed. Manual of Orthopaedics. 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2013:232-261.
Type I: apical avulsion fracture (involves alar ligament)
Type IIA: base fracture at the junction of the odontoid process and C2 body—minimally displaced
Type IIB: base fracture—displaced with anterosuperior to posteroinferior oblique fracture line
Type IIC: base fracture—displaced with anteroinferior to posterosuperior oblique fracture line
Type III: body fracture in the C2 cancellous bone, possibly extending into lateral facets
If isolated injuries, type I and III fractures are usually stable and have good healing potential with cervical collar (Type I) or halo immobilization (Type III).
Type II fractures have a high nonunion rate and can often benefit from surgical fixation. Nonunion risk factors:
Increased patient age
Displacement >5 mm
Type II fractures can be treated by lag screw fixation (Type IIB pattern is most likely to benefit from this technique) or C1-C2 arthrodesis.
C2 lateral mass fractures
Caused by combined lateral bending and axial compression forces
Usually treated in cervical orthosis. Chronic pain may be an indication for later arthrodesis.
C2 pars fractures (Hangman fracture; Figure 9.9)
This represents a traumatic spondylolisthesis of the axis caused by hyperextension and axial loading; involves fractures of bilateral pars interarticularis of C2.
Levine and Edwards classification categorizes these fractures according to the degree of displacement, angulation, translation, and C2-C3 disk disruption.
Type I: nondisplaced, <3 mm translation, no angulation, C2-C3 disk intact
Type II: displaced, substantial C2-C3 angulation and >3 mm translation, C2-C3 disk disrupted
Type IIA: displaced, severe C2-C3 angulation but no translation, severe C2-C3 ligamentous complex disruption, hinging on the ALL
Type III: pars fracture with associated unilateral or bilateral C2-C3 facet dislocation
Type I: usually treated with cervical orthosis
Type II: if <5-mm displacement, can be reduced with axial traction and extension and then immobilized in halo; if >5-mm displacement, usually requires surgical stabilization
Type IIA: should not be placed in traction because of risk for ligamentous disruption; reduce with hyperextension alone and then halo immobilization
Type III: usually requires reduction followed by open reduction and internal fixation of C2, or arthrodesis of C2-C3 or C1-C3
Allen-Ferguson classification system categorizes subaxial fractures and dislocations by injury mechanism (Figure 9.10).
Subaxial injury classification system builds on the Allen-Ferguson classification system, grading injuries by morphology, discoligamentous complex damage, and extent of neurologic compromise (Table 9.2).
Higher scores are more likely to require surgical treatment.
Compressive flexion injuries
Cervical spine is axially loaded and flexed—indicates compression fractures without neurologic deficits; can often be treated nonoperatively.
In severe cases, can develop triangular “teardrop” fracture anteriorly, PLC disruption, and retrolisthesis, causing spinal canal compromise, which requires surgical treatment with anterior decompression and plating with or without posterior fixation.
Vertical compression injuries
Pure axial loading can cause burst fractures with retropulsion of bony fragments into the canal.
Can be treated with anterior decompression and plating with or without posterior fixation
Distractive flexion injuries
Most common mechanism causing facet dislocations
Subaxial facet dislocations (Figure 9.11)
Most commonly occur at C5-C6 and C6-C7 levels
Unilateral facet dislocations—usually involves <50% translation
Bilateral facet dislocations—usually involves >50% translation
Often associated with nerve root or spinal cord injuries; 30% of patients have complete spinal cord injuries
Use of MRI is controversial; most authors recommend MRI before reduction to rule out herniated disk, which occurs in ˜7% of cases.
If herniated disk present, proceed with open decompression and arthrodesis via anterior approach.
If no herniated disk present and the patient is alert and cooperative, attempt closed reduction with traction.
Compressive extension injuries can cause unilateral or bilateral vertebral arch fractures; in most severe cases, there can be anterior ligamentous disruption with anterolisthesis.
Distractive extension injuries cause anterior ligamentous disruption and, in most severe cases, injury of the PLC with posterior displacement of the rostral vertebral body into the canal.
Table 9.2 Subaxial Cervical Spine Injury Classification System Scale
+1 = 2
Complete cord injury
Incomplete cord injury
Continuous cord compression in setting of neurologic deficit (neuro modifier)
a For example, facet perch, hyperextension.
b For example, facet dislocation, unstable teardrop, or advanced-stage flexion-compression injury.
c For example, isolated interspinous widening, magnetic resonance imaging signal change only.
d For example, widening of disk space, facet perch, or dislocation.
From Vaccaro AR, Hulbert RJ, Patel AA, et al; Spine Trauma Study Group. 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 (Phila Pa 1976). 2007;32:2365-2374.
Treatment depends on stability and neurologic compromise, with most severe cases requiring surgical intervention.
Lateral flexion injuries
Involve direct trauma to the side of the head, leading to distraction forces on the side of impact and compression contralaterally
Can result in ligamentous disruption and lateral mass fractures
Treatment depends on stability and neurologic compromise.
Cervical spinous process avulsion fracture
Known as “clay-shoveler fracture”
Most common at C7
Results from musculoligamentous avulsive forces during sudden flexion/extension activities (eg, shoveling hard dirt)
Usually treated nonoperatively; can be excised if patient develops painful nonunion
Major causes of thoracolumbar trauma: motor vehicle accidents (38%), falls, violence (gunshot wounds), and sporting accidents
Bimodal distribution in young adults and the elderly
Location of thoracolumbar spine trauma
T11-L2 thoracolumbar junction/transitional zone (50%)
Fulcrum for movement
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