The position of the spine at the time of impact is important in explaining the injury pattern [205].. The position of the spine at impact determines the fracture pattern Cadaveric studie
Trang 1Personal, societal, and
environmental factors
appear to play a role
Although it seems that females are at slightly greater risk, the evidence that gender is associated with risk of WAD is inconsistent [107] Younger patients appear to have a slightly higher risk of WAD [107] Preliminary evidence indi-cates that headrests/car seats which aim to limit head extension during a rear-end collision have a preventive effect on WAD reporting [107] The evidence regard-ing risk factors for WAD is sparse but appears to include personal, societal, and environmental factors [107]
WAD tends to become
chronic
The rate of patients reporting persistent pain, restriction of motion or other
symptoms at 6 months or more after a whiplash injury (late whiplash syndrome)
[184], sufficient to hinder return to normal activities such as driving, normal occupational and leisure activities, ranges between 1 % and 71 % [52, 175, 207] However, it appears from the literature that there is a strong tendency for WAD to become chronic, with about 50 % of patients having symptoms one year after the injury [43] Greater initial pain, more symptoms, and greater initial disability appear to predict slower recovery Postinjury psychological factors such as pas-sive coping style, depressed mood, and fear of movement were prognostic for slower or less complete recovery [43]
Pathomechanisms Normal Anatomy
Functionally, the cervical spine is divided into the upper cervical spine [occiput (C0)–C1–C2] and the lower (subaxial) cervical spine (C3–C7) The C0–C1–C2 complex is responsible for 50 % of all cervical rotation while 80 % of all flexion/ extension occurs in the lower cervical spine [135] (Table 1)
Table 1 Normal cervical spinal motion
Flexion/extension R/L rotation In-/reclination
(50 %) 2 × 3° (10 %)
C3/T1 10 – 20° (83 %) 2 × 2–14° (50 %) 2 × 2–6° (90 %)
According to Louis [135]
Upper Cervical Spine
The atlas-occiput junction primarily allows flexion/extension and limited rota-tion The flexion is limited by a skeletal contact between the anterior margin of the foramen magnum and the tip of the dens [204] Flexion/extension is also lim-ited by the tectorial membrane, which is the cephalad continuation of the poste-rior longitudinal ligament [204] Axial rotation at the craniocervical junction is restricted by osseous as well as ligamentous structures (Fig 1) The occipital
Trang 2con-Figure 1 Anatomy of the upper cervical spine
aLateral midsagittal view;bsuperior view;ccoronal view.
The alar ligaments restrain upper cervical spine rotation
dyles articulate with a concave shaped joint surface of the atlas The atlantoaxial
joint is composed of lateral mass articulations with loosely associated joint
cap-sules and an atlantodental articulation [135] The paired bilateral alar ligaments
bilaterally connect the dens with the occiput condyle and the atlantal mass The
alar ligaments restrain rotation of the upper cervical spine, whereas the trans- The transverse ligaments
restrict flexion and displacement of the atlas
verse ligaments restrict flexion as well as anterior displacement of the atlas [69].
The transverse ligament also protects the atlantoaxial joints from rotatory
dislo-cation Lateral bending is controlled by both components of the alar ligaments
[204] Ligamentous laxity and a horizontal articular plane at the occiput–C1
joint, along with the relatively large weight of the head, may explain why injuries
at this junction are more common in children than adults [205]
Lower (Subaxial) Cervical Spine
The vertebrae of the lower cervical spine have a superior cortical surface which
is concave in the coronal plane and convex in the sagittal plane (Fig 2) This
con-figuration allows flexion, extension, and lateral tilt by gliding motion of the facets
[135] The lateral aspect of the vertebral body has a superior projection (uncinate
process) which develops during growth and is established at the end of
adoles-cence As the discs become degenerative, these projections articulate with the
body of the next highest vertebra and can lead to an uncovertebral osteoarthrosis
[135] The range of flexion/extension is in part dictated by the geometry and
stiff-ness of the intervertebral disc, i.e., the greater the disc height and the smaller the
sagittal diameter, the greater is the motion Conversely, the greater the stiffness of
The C5/6 level exhibits the largest ROM
the disc, the smaller the spinal motion [204] The C5/6 level exhibits the largest
range of motion, which in part explains its susceptibility to trauma and
degener-ation [136] Besides the intervertebral disc and facet joints, the muscles and the
ligaments, particularly the yellow ligament, dictate the spinal kinematics [204]
The facet joint capsules are stretched in flexion and therefore limit rotation in
this position
Trang 3Figure 2 Anatomy of the lower (subaxial) cervical spine
aAxial view;bcoronal view;clateral view.
Biomechanics of Cervical Spine Trauma The conditions under which neck injury occurs include several key variables
such as [205]:
) impact magnitude
) impact direction
) point of application
) rate of application The rate of application of the impact load is a critical variable The relative posi-tion of the head, neck and thorax is a major factor in both the threshold of failure and the pattern of failure Pattern of failure indicates which structural compo-nents of the spine are injured The position of the spine at the time of impact is important in explaining the injury pattern [205]
The position of the spine
at impact determines the
fracture pattern
Cadaveric studies have substantially increased our understanding of the frac-ture mechanisms that lead to specific spinal fracfrac-tures [205] Fracfrac-tures of the atlas
ring (Jefferson fractures) can be created in an experimental setup by axial
load-ing of the straight spine in slight extension In an experimental study, Altoff [18]
has shown that dens fractures result from a combination of horizontal shear and
Os odontoideum commonly
results from childhood
trauma of the dens
vertical compression [205] An os odontoideum ( Fig 3a, b) is considered to be a result of an early childhood trauma to the dens that leads to a non-union and sub-sequent formation of a loose ossicle This entity usually causes an atlantoaxial instability [76, 141, 176] In a biomechanical study, Fielding et al [73] have shown
that atlantoaxial instabilities can result from tears of the transverse ligament without a fracture of the dens Traumatic spondylolisthesis of the axial pedicle
was first described by Schneider [172] in the context of judicial hanging with a submental knot (hangman’s fracture) that results in an extension-distraction injury Similar injuries are observed in motor vehicle and diving accidents
In the lower cervical spine, Bauze and Ardran [27] were able to reproduce pure
ligamentous injuries by vertical loading of the lower cervical spine in the
for-ward flexed position This mechanism produced bilateral dislocation of the facets without fracture A unilateral dislocation was produced if lateral tilt or axial rota-tion occurred as well The maximum vertical load was only 145 kg, and coincided with the rupture of the posterior ligament and capsule and the stripping of the anterior longitudinal ligament, but this occurred before dislocation The authors
Trang 4b
c
d
Figure 3 Specific fracture types
aOpen-mouth andblateral dens views (CT) demonstrate an os odontoideum
which may result from early childhood trauma.cAxial CT scan anddsagittal
image reformation demonstrate the typical feature of a “tear-drop” fracture
which results from a distraction injury with posterior ligamentous disruption.
concluded that the low vertical load indicates a peculiar vulnerability of the
cer-vical spine in this flexed position This correlates well with the minor trauma
often seen in association with forward dislocation [27] Axial loading less than
1 cm anterior to the neural position produced anterior compression fractures of
the vertebral body, while axial loads applied further anteriorly resulted in a
rear-ward buckling with subsequent disc and endplate failure Burst fractures can be
produced by direct axial compression of a slightly flexed cervical spine [205] In
an experimental setup, “tear-drop” fractures could be created by axial
compres-Tear-drop fracture results from a flexion/compression injury with disruption
of the posterior ligaments
sion of the neutral and minimally flexed cervical spine [137, 205] The “tear-drop
fracture” ( Fig 3a, b) was first described by Schneider and Kahn in 1956 [171]
This injury type is a fracture by the mechanism of flexion/compression with
sag-ittal sprain of the intervertebral cervical disc and disruption of the posterior
liga-ments CT investigations demonstrated the coexistence of two lines of fractures:
a frontal fracture (by the mechanism of flexion), and a sagittal fracture (by
com-pression) Displacement of the posterior vertebral body fragment frequently
results in a spinal cord injury [82] Cervical disc ruptures could be produced in
many specimens subjected to axial impact in various degrees of
flexion/exten-sion but appear to be most common in axial rotation and lateral flexion at the
time of impact [205]
Trang 5) The loss of the ability of the spine under physiological loads to maintain its pattern of displacement so that there is no initial or additional neurological deficit, no major deformity and no incapacitating pain.
The definition of instability
remains controversial
However, various attempts were made to develop radiological criteria (see
below), to guide the choice of treatment [206]
Spinal Cord Injury
It is now well accepted that acute spinal cord injury (SCI) involves both [72, 109]:
) primary injury mechanisms
) secondary injury mechanisms
The primary injury of the spinal cord results in local deformation and energy
transformation at the time of injury and is irreversible It can therefore not be repaired by surgical decompression In the vast majority of cases the injury is caused by bony fragments that acutely compress the spinal cord Further
mecha-Both primary and secondary
mechanisms contribute
to SCI
nisms include acute spinal cord distraction, acceleration-deceleration with shearing, and laceration from penetrating injuries [72] The injury directly dam-ages cell bodies and/or processes of neurons The cells that are damaged might die and there is no evidence that they are replaced [37] and can therefore not be
repaired by surgical decompression Immediately after the primary injury,
sec-ondary injury mechanisms may initiate, leading to delayed or secsec-ondary cell
death that evolves over a period of days to weeks [109] A variety of complex
chemical pathways are likely involved including [109]:
) hypoxia and ischemia
) intracellular and extracellular ionic shifts
) lipid peroxidation
) free radical production
) excitotoxicity
) eicosanoid production
) neutral protease activation
) prostaglandin production
) programmed cell death or apoptosis
Secondary SCI resulting
from hypotension and poor
tissue oxygenization
must be avoided
These mechanisms result in a secondary death of neuronal and glial support cells days or weeks after the injury [109] These secondary events are potentially pre-ventable and reversible [72] In the case of a lesion of the cord cranial to T1, a complete loss of sympathetic activity will develop that results in loss of compen-satory vasoconstriction (leading to hypotension) and loss of cardial sympathetic activation (leading to bradycardia) Secondary deteriorations of spinal cord function that result from hypotension and inadequate tissue oxygenization have
to be avoided
Trang 6Injuries to the spinal cord often result in spinal shock This is a term that is
com-monly used but poorly understood [144] In analogy to the electrical circuit, the
state of spinal shock can be considered as a result of a blown fuse The
phenome-Spinal shock is characterized
by an immediate post-injury loss of sensation, flaccid paralysis and loss of all reflexes
non of spinal shock is usually described as a loss of sensation and flaccid
paraly-sis accompanied by an absence of all reflexes below the spinal cord injury It is
thought to be due to a loss of background excitatory input from supraspinal
axons [65] Spinal shock is considered the first phase of the response to a spinal
cord injury, hyperreflexia and spasticity representing the following phases
When spinal shock resolves, usually within days up to 6 weeks, reflexes will
return and residual motor functions can be found The clinical significance of
spinal shock lies in the associated loss of motor function (in nerves that are not
necessarily damaged) and a flaccid paralysis caudal to the lesion
Central cord syndrome is characterized by dispro-portionately more motor impairment of the upper than lower extremities
Central spinal cord injuries are among the most common, well-recognized
spinal cord injury patterns identified in neurologically injured patients after
acute trauma Originally described by Schneider et al in 1954 [170], this pattern
of neurologically incomplete spinal cord injury is characterized by
dispropor-tionately more motor impairment of the upper than of the lower extremities,
bladder dysfunction and varying degrees of sensory loss below the level of the
lesion It has been associated with hyperextension injuries of the cervical spine,
even without apparent damage to the bony spine (mainly by osseous spurs), but
has also been described in association with vertebral body fractures and
frac-ture-dislocation injuries The natural history of acute central cervical spinal cord
injuries indicates gradual recovery of neurological function for most patients,
although it is usually incomplete and related to the severity of injury and the age
of the patient [142, 170, 174]
Pathomechanism of Whiplash-Associated Disorders
It is likely that WAD results from cervical sprain or strain but the exact
pathome-chanisms remain largely unknown [107] Structural abnormalities of cervical
joints, discs, ligaments and/or muscles are very rarely found Indeed, there is
evi-WAD is inversely related
to the severity of the injury
dence that the likelihood of the development of WAD is inversely related to the
severity of the injury [88, 138]
Whiplash actually describes the injury as an acceleration/deceleration
mech-anism of energy transfer to the neck [184] Kinematic analysis demonstrated
that the whiplash mechanism consists of translation/extension (high energy)
with consecutive flexion (low energy) of the cervical spine Hyperextension of
the cervical spine has not been observed during vehicle crashes if headrests are
installed [45] The current evidence does not allow any conclusions to be drawn
about a specific injury mechanism; particularly the minimum threshold of
impact forces causing WAD in real-life accidents remains unknown [107]
Inter-estingly, no evidence suggests that awareness of the collision, head position at the
time of impact, or cervical spondylosis are of relevance for WAD [107]
The large variety of clinical symptoms which have been associated with
whip-lash injuries, including cognitive dysfunction following the injury, lead to the
WAD is not associated with mild brain damage
suspicion of a mild traumatic brain injury [160, 169, 191] Based on a recent
com-prehensive review of the literature, there is no evidence that poor cognitive
func-tioning in patients seeking treatment for chronic WAD is the result of
demonstra-ble brain damage Instead, these deficits may be linked to a chronic health
condi-tion including chronic pain [107] In this context it has been shown that spinal
cord hyperexcitability in patients with chronic pain after whiplash injury can
cause exaggerated pain following low intensity nociceptive or innocuous
periph-WAD has similarities with chronic pain syndromes
eral stimulation Spinal hypersensitivity may explain, at least in part, pain in the
absence of detectable tissue damage [26, 56, 103]
Trang 7In patients with evidence for neurological deficits, the history should include:
) time of onset (immediate, secondary)
) course (unchanged, progressive, or improving)
The time course of the
neurological deficit matters
Particularly, progressive paresis must not be missed
History should include the
trauma type and injury
mechanism
The history should include a detailed assessment of the injury, i.e.:
) type of trauma (high vs low-energy)
) mechanism of injury (compression, flexion/distraction, hyperextension, rotation, shear injury)
In polytraumatized or unconscious patients history taking is not possible for
obvious reasons and the patient must be subjected to thorough imaging studies Polytraumatized patients must be considered to have sustained a cervical injury until proven otherwise
Patients who have suffered a rear-end collision present as a particular
diag-nostic challenge In these patients pain may even persist for a long time after the
accident (late whiplash syndrome) [184] and imaging studies are usually
nega-tive It is therefore mandatory to assess the history with great detail also with regard to the medicolegal implications of these injuries Patients frequently com-plain of [104, 140, 149, 159, 161]:
) reduced/painful neck movements
) headache
) paresthesias
) temporomandibular pain
) dizziness/unsteadiness
) nausea/vomiting
) difficulty swallowing
) tinnitus
) sleep disturbances
) cognitive dysfunction (memory and concentration problems)
) vision problems
) lower back pain
The history should also comprehensively assess details of collision and injury
such as [184]:
) type of collision (rear-end, frontal or side impact)
) use of headrest/seat belt
) position in the car
) injury pattern for all passengers
) head contusion
) severity of impact to the vehicle The latter aspects may be of more relevance in the medicolegal than a clinical context
Trang 8Physical Findings
The initial focus is on vital functions and neurological deficits
The initial focus of the physical examination of a patient with a putative cervical
spine injury is on:
) vital functions (perfusion, respiration)
) neurological deficits
Timely and effective resuscitation is critical to the management of
polytrauma-tized and spinal cord injury patients In cervical spine injuries above C5,
respira-tion may be compromised because of damage to the diaphragm innervarespira-tion (C4)
or injuries to the brain stem In both polytrauma and spinal cord injury,
hypo-tension is common although the underlying pathophysiology is different The
reason for the hypotension can be hypovolemic and/or neurogenic shock (due to
the loss of neurovegetative function) that have to be considered and treated
accordingly The emergency room management of the multiply injured patient
with spine injuries has recently been reviewed [209]
The inspection and palpation of the spine should include the search for:
) skin bruises, lacerations, ecchymoses
) open wounds
) swellings
) hematoma
) painful structures (spinous, transverse, and mastoid processes; facet joints)
) spinal (mal)alignment (torticollis)
) gaps/steps
Rotatory dislocations present typically with torticollis with the head in the “cock
robin position,” so called because the chin is turned towards one side and the
neck is laterally flexed to the opposite side
Consider a latent unstable spine before functional testing
A full functional testing of the cervical spine should only be done after a
frac-ture dislocation has been excluded by radiography or in patients who present
with secondary problems The patient is best examined sitting on an
examina-tion table with their lower limbs and feet freely moving (see Chapter 8) The
functional testing should be done very carefully The assessment of the mobility
of the cervical spine consists of:
) flexion/extension (chin-sternum distance: documentation, e.g., 2/18 cm)
) left/ride rotation (normal: 60°–0 – 60°) in neutral position
) left/ride rotation (normal: 30°–0 – 30°) in flexed position
) left/ride rotation (normal: 40°–0 – 40°) in extended position
) left/side bending (normal: 40°–0 – 40°)
In case of limitation in active movements, the examination should be repeated
with passive motion to differentiate between a soft (muscle, pain) and a hard
(bony) stop The examiner should not only record the range of motion but also
pain provocation Examining the cervical spine against resistance can be used to
stress the intervertebral discs (flexion, side bending) or facet joints (rotation,
extension), respectively If a cervical radiculopathy is suspected, a Spurling or
shoulder depression test can be done (see Chapter 8)
A thorough neurological examination is indispensable (see Chapter 11) In
case of a neurological deficit, the differentiation is mandatory between:
) nerve root(s) injury
) spinal cord injury (complete, incomplete)
The differentiation of a complete and incomplete paraplegia is important for the
prognosis Approximately 60 % of patients with an incomplete lesion have the
Trang 9can range from asymptomatic (in about 20 %) to a partial or complete “locked-in
syndrome” [147] This syndrome is caused by a separation of the corticobulbary
and corticospinal tracts at the abducens nuclei level in the pontine Clinically, the
“lock-in syndrome” is characterized by tetraplegia, muteness and akinesia Only movements of the eyelids and the eye in the vertical direction are preserved
Precise documentation
of the initial neurological
status is mandatory
Neurological function must be precisely documented (see Chapter 11) The two most commonly used systems for quantifying and grading the spinal cord injury are the Frankel system [81] and the more comprehensive system
devel-oped by the American Spinal Injury Association (ASIA) [139].
Classification of Whiplash-Associated Disorders
For patients who have sustained a cervical sprain or strain due to a motor vehicle
collision, the Quebec Task Force has recommended a clinical classification
sys-tem which grades symptoms as follows [43, 184] (Table 3):
Table 3 Grading of whiplash-associated disorders
Grade 0 ) WAD refers to no neck complaints and no physical signs
Grade I ) WAD refers to injuries involving complaints of neck pain, stiffness or
tender-ness, but no physical signs
Grade II ) WAD refers to neck complaints accompanied by decreased range of motion
and point tenderness (musculoskeletal signs)
Grade III ) WAD refers to neck complaints accompanied by neurological signs such as
decreased or absent deep tendon reflexes, weakness and/or sensory deficits
Grade IV ) WAD refers to injuries in which neck complaints are accompanied by
frac-ture or dislocation
Other symptoms such as deafness, dizziness, tinnitus, headache, memory loss, dysphagia, and temporomandibular joint pain can be present in all grades
Diagnostic Work-up
Immobilization of the
cervical spine must be
maintained until an injury
is excluded
Immobilization of the cervical spine must be maintained until the cervical spine
is “cleared,” i.e., a spinal cord injury or spinal column injury has been ruled out
by clinical or radiographic assessment [9, 10, 164]
Imaging Studies
A cervical spine injury
is found in 2 – 6 % of all
symptomatic patients
The reported incidence of cervical spine injuries in the symptomatic patient
ranges from 2 % to 6 % in Class I evidence studies [10] Symptomatic patients
require radiographic studies to rule out the presence of a traumatic cervical spine injury before the cervical spine is cleared
Trang 10Figure 4 Canadian C-Spine Rule
MVC motor vehicle collision, ED emergency department (According to Stiell et al [186], reproduced with permission
from AMA).
In 2001, a highly sensitive decision rule (“Canadian C-Spine Rule”) was derived,
for use in cervical spine radiography in alert and stable trauma patients [186]
This rule comprises three main questions (Fig 4) and has had a 100 % sensitivity
in identifying 151 clinically important cervical spine injuries
The NEXUS (National Emergency X-radiography Utilization Study) [105]
developed a decision instrument which allows the identification of patients who
have a low probability of a cervical injury The five criteria which must be met
are:
) no midline cervical tenderness
) no focal neurological deficit
) normal alertness
) no intoxication
) no painful, distracting injury
In this study, only 2 out of 34 069 evaluated patients classified as unlikely to have
an injury met the preset criteria of having a potential significant injury (only one
needed surgical treatment) [105] However, this study was criticized because two
criteria, “presence of intoxication” and “distracting, painful injuries,” are poorly
reproducible [186]