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Surgical Treatment of Spinal Injury Neurochirurgia

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      Surgical Treatment of Spinal
                 Injury
                         Daniel R. Fassett
                          James S. Harrop




Traumatic injuries to the spinal column are common events, with
    more than 50,000 fractures to the spinal column occurring
    annually in the United States (1). Spinal injury remains a
 heterogeneous group of injuries and therefore various strategies
 are employed in their treatment. Multiple clinical variables must
   be addressed, including the degree of ligamentous and bony
   injury, the presence of neu rologic deficits, perceived patient
 compliance, and overall health status; these factors are used to
determine how the injuries are treated. Treatment can range from
simple limitation in activity to external orthosis to open reduction
   and internal fixation with spinal instrumentation. The goal of
   treating these injuries is to utilize the least invasive surgical
   technique to stabilize the injured segment while limiting the
     potential for subsequent catastrophic neurologic injury,
  progression of a deformity, a nd chronic pain conditions. These
 surgical goals are also tempered by other medical management
issues that focus on minimizing hospitalization and immobilization
and maximizing the benefits of early and aggressive rehabilitation.
  Historical Perspective of Spinal Injury
                         Treatment
   Treatment of traumatic spinal injuries was first recorded by
 Hippocrates (460-370 BCE) who used traction devices to obtain
    spinal reduction and advocated external stabilization and
immobilization. Surgery was not considered a viable option at this
time because of the high mortality of surgical techniques, and the
presence of neurologic deficits in the setting of spinal trauma was
    deemed universally fatal. Surgical decompression for the
treatment of traumatic spinal cord injury was in itially popularized
    by Paulus of Aegina (625 -690 CE) but was not universally
accepted because of very poor surgical outcomes at the time. In
 1646, Fabricius Hildanus performed the first documented open
       reduction of a spinal fracture (2, 3, 4, 5, 6 and 7).
It was not until the advent of spinal instrumentation in the 1950s
  that a more aggressive surgical approach was favored in the
 treatment of spinal column injuries. Before the development of
  spinal instrumentation, there was a bias toward conservative
                 treatment, which often involved
                               P.40


long periods of immobilization (4 to 8 weeks commonly) typically
   with traction to restore the spinal alignment and allow the
 fractures time to heal (8). These long periods of immobilization
 were associated with significant medical complications including
pneumonia, deep vein thrombosis, and decubitus ulcers. The use
of spinal instrumentation provided surgeons the ability to restore
immediate stability to the spinal column, thus allowing for earlier
      mobilization and fewer co mplications from prolonged
 immobilization. In addition, spinal instrumentation theoretically
 improved fusion rates by providing a stable environment of bone
 healing, thus reducing the risks of late neurologic deterioration
    due to spinal instability, progre ssive spinal deformity, and
associated axial back pain syndromes. Even with improvements in
 instrumentation, it was realized that all instrumentation will fail
    eventually unless a bony fusion is achieved and, therefore,
   arthrodesis remains a critical part of all spinal stabilization
                          surgeries (4,6).

  Clinical and Radiographic Evaluation of
                   the Trauma Patient
 The treatment of spinal trauma consists of an assessment of the
   traumatic injury through a detailed neurologic examination,
    physical examination, and th en a radiographic evaluation.
   Radiographic evaluation often begins with plain radiographs
followed by supplemental imaging of questionable areas of injury.
  Although modern imaging techniques have greatly aided in the
  diagnosis of fractures, determination o f ligamentous instability
with imaging alone is still unproven even with techniques designed
 to evaluate the soft tissues such as magnetic resonance imaging
                             (MRI) (9).

             Cervical Spine Evaluation
Any trauma patient should immediately be placed in cervical spine
  immobilization when assessed by emergency medical services
 (EMS) in the field. Any nonintoxicated patient without neck pain,
   neurologic deficits, and distracting injuries (injuries to other
     portions of the body that could potentially mask the pain
  associated with spinal injury) can be cleared of cervical spine
 injury with a normal clinical examination alone (i.e., showing no
neck pain over a full range of motion of the cervical spine) (10).
 Neurologically intact patients with neck pain or tenderness are
 usually assessed with three view (anteroposterior [AP], lateral,
   and open-mouth odontoid views) plain radiographs as initial
  assessment (11). If these plain radiographs are normal, these
patients are often kept in cervical collar immobilization for 1 to 2
weeks and then should have delayed passive cervical flexion and
   extension imaging to assess for potential occult ligamentous
injury. Although the prevalence of occult ligamentous injury in the
setting of normal radiographs is small, the delay in the follow -up
flexion/extension imaging can minimize false negative results by
  allowing muscle spasm to subside. In the neurologically intact
   patient with severe neck pain and normal plain radiographs,
     computed tomography (CT), and possibly MRI should be
  considered to rule out an occult fracture or herniated disc not
               seen on the plain radiographs (11).
In comatose, obtunded, or intoxicated/sedated patients, where an
   adequate neurologic examination cannot be obtained, plain
 radiographs or CT scan are standard in most trauma protocols.
With the increase in speed and resolution of multidetector helical
     CT scanning, this modality is becoming more popular for
  evaluating multitrauma patients in a time -efficient manner. If
   these patients remain comatose, dynamic flexion/extension
studies with fluoroscopic guidance or a normal cervical spine MRI
  within 48 hours of injury is sometimes performed for cervical
spine clearance, although the inherent value of either meth od for
 the exclusion of occult soft tissue injury is questionable (9,11).
Patients with neurologic deficits that are clinically attributable to a
spinal cord injury deserve rapid radiographic assessment possibly
 including plain films, CT scanning, and MRI. In the setting of an
  obvious cervical spine deformity with neurologic deficits, some
 surgeons may immediately institute reduction measures such as
     cervical traction. Other surgeons may insist upon further
    evaluation with CT and MRI before initiating any r eduction
  measures. The extent of radiographic workup in the setting of
spinal cord injury will depend on the preferences of the individual
     surgeon, the unique characteristics of the fracture being
 evaluated, and the character of neurologic examination. Pat ients
     with incomplete spinal cord injuries, where there is some
neurologic function below the level of the spinal cord injury, may
 warrant an emergent MRI examination to assess integrity of the
spinal canal and rule out herniated discs as an explanation fo r the
  neurologic deficits. The patient with a progressive, incomplete
 neurologic deficit requires immediate assessment and treatment
as these patients have the greatest potential to permanently lose
                   function with treatment delay.

   Thoracic and Lumbar Spine Evaluation
    Awake, neurologically intact patients can have thoracic and
  lumbar spine precautions discontinued if they do not have any
    pain suggestive of spinal injury and do not have distracting
   injuries. Neurologically intact patients that complain of pain
localizing to the spine or who harbor a distracting injury should be
evaluated radiographically with a minimum of AP and lateral plain
                            radiographs.
                                 P.41
    Depending upon the severity of their symptoms, CT or MRI
       imaging may be warranted. Comatose, obtunded, or
sedated/intoxicated patients should always be evaluated with plain
 films or CT scanning. Multisystem trauma patients often require
routine CT imaging of the chest, abdomen, and pelvis. It has been
  suggested that limited resolution imaging of the thoracic and
lumbar spine can be extracted from these data sets and used as a
          substitute for radiographs of these areas (12).
In patients with neurologic defici ts where there is a high suspicion
       for spinal injury, CT scans with coronal and sagittal
 reconstructions are often the initial imaging modality to improve
   the sensitivity for diagnosis of spinal injury and also provide
better anatomic details about the spe cific fracture. A patient with
   a persistent neurologic deficit and a “normal†• CT scan
 warrants performance of an emergent MRI both to visualize the
spinal cord and cauda equina and to rule out soft tissue etiologies
 of spinal column compromise such as herniated discs or epidural
  hematoma that may be not visualized with CT scanning. Some
   surgeons may wish to obtain emergent MRI in patients with
obvious fractures diagnosed with CT, since the MRI can help locate
   the level of the conus medullaris, assess th e integrity of the
     intervertebral discs, and better appreciate the extent of
ligamentous injury. All of these factors may impact the treatment
of the patient by providing the surgeon with a better appreciation
                of the anatomy of the spinal injury.

            Current Treatment Options
                    External Orthosis
 Numerous external orthosis (spinal braces) options are available
for the treatment of spinal injuries. The principle of bracing is to
 reduce motion at the injured spinal area in order to improve the
likelihood of healing and reduce the potential for neurologic injury
 as a result of spinal instability. In general it is felt that maximal
  reduction in motion will result in better healing of the injured
 spinal segment, but literature is lacking in regard to how much
motion is “too much― when considering bracing. Indications
for external orthosis following spinal injury can vary significantly
 among individual surgeons since there are limited guidelines in
 the surgical literature for this type of treatment. Some fractures
 may not require any bracing as they are deemed to be very low
  risk for spinal instability and other fractures may be stabilized
    surgically, thus eliminating the need for external orthosis.
    For the cervical spine, options ranging from least to most
restrictive are soft and hard cervical collars (Philadelphia, Aspen,
  Miami J), cervical bracing with the addition of a thoracic vest
(SOMI and Minerva braces), and halo -vest immobilization (Fig. 3 -
1). A cervical collar is the least cumbersome of the cervical spine
orthosis options; however, this comes at the cost of it offering the
 least support in terms of limiting range of motion. Studies have
   shown that cervical hard collars allow for over 30 degrees of
flexion-extension motion in the cervical spine and provide min imal
    support at the lower cervical spine (13). Braces that add a
  thoracic vest immobilize the cervical spine and cervicothoracic
    junction better but still allow for significant motion at the
      craniocervical junction (Fig. 3 -1B) (14,15). Halo -vest
      immobilization (Fig. 3-1C) accomplishes the most rigid
immobilization by fixating a halo -ring around the head (pins into
 the skull) and securing the halo -ring to a thoracic vest by rods.
Although halo immobilization provides the most support and may
  improve fusion r ates, it may be associated with complications
   ranging from pin loosening, pin site infections, to swallowing
   dysfunction, reduced immobilization, and cerebral abscesses
   attributable to intracranial penetration of fixation pins. Halo
  immobilization also ten ds to limit motion of the upper cervical
 spine with greater efficiency than the middle and lower cervical
spine. Even with halo immobilization, studies have shown that 2 to
10 degrees of motion can take place at the craniocervical junction,
and the lower cervical spine and cervicothoracic junction may not
be adequately mobilized (14). In addition, immobilization in a halo
 can cause limited motion at the ends of the spine (craniocervical
  and cervicothoracic) with exaggerated motion in the subaxial
                spine, referred to as snaking (14).
In the thoracic spine, the rib cage provides some natural support
  for thoracic spine fractures. The upper thoracic region (T5 and
   above) is a very difficult region to immobilize with external
  orthosis, unless the patient is immobi lized with a halo orthosis
   with a long thoracic vest. Spinal fractures from T6 to L2 are
    typically braced with a custom molded, hard -shell orthosis
  (thoracolumbar-sacral orthosis [TLSO]) or with more versatile,
adjustable-fit braces (e.g., Jewitt, Aspen) ( Fig. 3-2A) or clamshell
  brace (Fig. 3-2B). Below L3, a lumbosacral orthosis is used for
    support. In addition, to increase the immobilization at the
lumbosacral junction, a leg extension can be fitted to the orthosis
 to assist in limiting motion across the pelvis. Casting (Fig. 3 -2C)
is another option for lumbar and thoracolumbar fractures and can
 provide better support and eliminate concerns of noncompliance.
   Surgical Options for Traumatic Spinal
                           Injuries
 Controversy persists in the surgical community regar ding the
 optimal treatment of many traumatic spinal injuries, especially
  regarding timing of surgical intervention and type of surgical
             approach. Surgical intervention is often
                               P.42


  advocated to (a) decompress the neural elements in cases of
neurologic deficit; (b) prevent possible late neurologic injury in
unstable fractures; (c) correct and prevent deformity that could
  result in chronic axial (back) pain or neurologic loss; and (d)
provide for early mobilization, thus avoiding the complications of
                       prolonged bed rest.
FIGURE 3-1. A wide variety of spinal orthoses are available to
treat cervical spine injuries including: (A) cervical collars (Aspen
cervical collar shown), (B) cervical brace with thoracic vest
(Minerva brace shown), and (C) halo-vest immobilization (Bremer
Halo Crown and AirFlo vest by DePuy Spine, A Johnson & Johnson
Company).

 Anterior (ventral), posterior (dorsal), and combined anterior and
    posterior approache s can be used to treat traumatic spinal
  instability. The surgical approach selected may depend on the
  fracture pattern, the neurologic status of the patient, and the
individual preference of the surgeon. Anterior approaches may be
                        favored in situations
                                P.43


    where a herniated disc or bone fragment is causing ventral
  compression on the spinal cord. In addition, fracture patterns
     where the integrity of the anterior column of the spine is
significantly compromised (unstable spine) may be best addressed
 by an anterior approach to restore the structural stability of the
anterior spinal column. In either case, the surgical approach also
includes some form of instrumentation. Spinal instrumentation is a
   method of straightening and stabilizing the spine after spina l
fusion, by surgically attaching hooks, rods, and wire to the spine
 in a way that redistributes the stresses on the bones and keeps
                     them in proper alignment.
FIGURE 3-2. Thoracolumbar fractures can be braced with (A)
adjustable-fit thoracolumbar sacral orthosis (Aspen TLSO shown),
(B) custom-fit hard-shell braces (clam shell), and (C) casting.
Posterior surgical approaches and instrumentation typically allow
for better reduction when deformities are present and may benefit
in restoring the posterior tension band in distraction-type injuries
where there is disruption of the posterio r ligamentous structures.
    The posterior ligamentous structures (ligamentum flavum,
  interspinous ligaments, supraspinous ligaments, and so forth)
      serve to hold the spine in normal alignment and since
                                P.44


    they are under tension in most parts of the spine they are
 referred to collectively as the posterior tension band . Injury to
these ligamentous structures can allow the spine to deform into a
 more kyphotic posture. With posterior instrumentation, there is
 restoration of the biomechanical forces needed to h old the spine
    in normal alignment. In terms of restoration of alignment,
posterior instrumentation (lateral mass screws) typically provides
  better fixation and mechanical advantage that can be used in
  spinal reduction maneuvers to better restore spinal ali gnment.
   In translation injuries (fracture -dislocations), when there is
severe, circumferential disruption of the spinal column, combined
  anterior-posterior instrumentation procedures may be used to
 maximize stability of the spinal column and increase the fusion
   rates. Circumferential spinal instrumentation (anterior and
posterior combined operations) is more commonly utilized in areas
of high biomechanical stress, such as the cervicothoracic junction
 and thoracolumbar junction, where the biomechanical forces on
the spine are greater and make these areas more prone to failure
                    of stabilization procedures.
  There is no single preferred approach to many types of spinal
  fractures; frequently the preferences of the individual surgeon
 take precedence. Despite the maturation of surgical techniques
and development of sophisticated spinal instrumentation devices,
   there is a lack of good guidelines for the treatment of many
  fractures. In general, posterior approaches to the thoracic and
lumbar spine are often favored because of the ease and familiarity
of approach. Anterior approaches to the thoracic and lumbar spine
   tend to be more technically challenging (mobilizing the lung,
 viscera, and great vessels) and may require the assistance of a
general or thoracic surgeon to aid with the approach to the spine.

    Treatment of Cervical Spine Injuries
           Occipital Condyle Fractures
Occiptial condyle fracture is an uncommon injury occurring in less
than 3% of patients with blunt craniovertebral trauma (16,17). CT
   is required to diagnose this i njury as there is less than 3%
diagnostic sensitivity with plain radiographs (18). These fractures
were first classified by Anderson and Montesano (19) into (a) Type
       I—comminuted due to axial compression, (b) Type
  II—extension of a basilar skull fractu re through the occipital
 condyle, and (c) Type III—an avulsion of the occipital condyle
   likely due to a rotational force that avulses a portion of the
occipital condyle with the alar ligament (Fig. 3 -3). There is a lack
of adequate studies to determine t he optimum treatment strategy
for these fractures. Most surgeons consider type I and II fractures
 stable injuries and will recommend cervical collar immobilization
  alone as an option to reduce pain associated with this injury.
     Type III occipital condyle fr actures are considered to be
mechanically unstable and have been associated with development
of lower cranial nerve deficits if untreated. Translation ≤ 1 mm
  between the occipital condyles and lateral masses of C1 at the
occipital-C1 joint is considered abnormal. Most unilateral type III
fractures are treated with cervical collar immobilization, but some
  surgeons advocate halo immobilization for fractures that have
  features of instability such as marked fracture displacement or
     abnormal craniocervical ali gnment. There are no specific
guidelines or measurements that predict which unilateral type III
  fractures are at risk for long -term instability. After a period of
immobilization, unilateral fractures can be evaluated in follow -up
with CT scanning to assess for the extent of bone union across the
   fractured segment, and flexion/extension radiographs can be
useful to assess for stability at the occipitocervical junction. Gross
instability at the occipitocervical junction is presumed for the rare
bilateral type III occipital condyle fractures, and atlanto -occipital
  dislocation (AOD) can be a component of this injury. When the
  features of AOD are present, an occipital cervical fusion is the
preferred method of treatment or in any patient that continues to
    have instability despite conservative therapy with external
                      immobilization. (20,21).

           Atlanto-Occipital Dislocation
    AOD has a significantly high fatality rate as a result of the
significant forces required to create this injury. AOD is commonly
associated with significant intracranial injury as well as vertebral
  artery injuries as a result of this distraction injury across the
     craniocervical junction. With improvements in the early
   recognition and stabilization of spinal injuries by EMS, more
 patients are surviving this injury. As a result of the tremendous
     distractive forces associated with the AOD, the tectorial
 membrane, posterior ligamentous structures, and facet capsules
     between the atlas and occipital condyles are injured, yet
surprisingly these injuries can b e difficult to detect on radiography
  and a high degree of vigilance is required. Several diagnostic
 criteria exist to help diagnose this injury on lateral radiographs
  including (a) the Powers ratio (22), (b) basion -dens distances,
 (such as Harris's rule of 12) (23, 24 and 25), (c) distances from
posterior mandible to anterior arch of C1 or dens (Dublin method)
   (26), and (d) Lee's X -line method (27) (Table 3 -1). Of these
  diagnostic options, Harris's rule of 12 appears to be the most
sensitive means of diagno sing this injury on plain films or sagittal
  reformatted CT images (Fig. 3 -4A). MRI potentially can also be
                                P.45


   very beneficial by showing the ligamentous disruption at the
                      craniocervical junction.
FIGURE 3-3. Classification of occipital condyle fractures
according to Anderson and Montesano (1). A: Type I fractures
may occur with axial loading. (Anderson PA, Montesano PX.
Morphology and treatment of occipital condyle fractures. Spine.
1988;13(7):731-736.) B: Type II fractures are extensions of a
basilar cranial fracture. C: Type III fractures may result from an
avulsion of the condyle during rotation, lateral bending, or a
combination of mechanisms. (From Jackson RS, Banit DM, Rhyne
AL III, et al. Upper cervical spine injuries. J Am Acad Orthop Surg .
2002;10(4):271-280, with permission.)
   AOD is considered highly unstable because of the extent of
    ligamentous injury and requires surgical stabilization with
 occipitocervical fusion procedures that instrument bridge ac ross
the occiput and upper cervical spine via a posterior approach (Fig.
                               3-4B).

                   Jefferson Fracture
   Bilateral fractures through the ring of C1 (classic Jefferson
 fracture) (Fig. 3 -5A) and other fractures of C1 can typically be
treated with conservative measures (collar or halo immobilization)
   because of the high rate of spontaneous fusion and limited
  ligamentous instability. Integrity of the transverse ligament is
   used as a determinant of stability and the need for possible
surgical stabilization. The most common means of evaluating the
   integrity of the transverse ligament is with an open -mouth
 odontoid view radiograph to assess the alignment of the lateral
masses of C1 and C2 using the rule of Spence (28). Greater than
7 mm of combined lateral overhang of the lateral masses of C1 on
C2 constitutes violation of the rule of Spence and suggests likely
transverse ligament rupture (Fig. 3 -5B). The transverse ligament
   may also be evaluated on MRI, but the application of MRI in
detecting transverse ligament rupture is unproven (29). Flexion -
extension plain films can also be used to assess for possible C1 -2
  instability. In the presence of C1 -2 instability from transverse
  ligament rupture, C1 -2 arthrodesis is recommended via wiring
   techniques, transarticular screws, or other C1 and C2 screw
techniques (Fig. 3 -6). Various rods, plates, and wire loop (Fig. 3 -
    6A) constructs are available to stabilize the craniocervical
junction. These systems generally provide screw fixation into the
 posterior occiput at the cephalad end. For fixation at the caudal
   end, a variety of devices can be used, including atlantoaxial
    transarticular screws (screws placed through the C2 pars
interarticularis, across the C1 -2 lateral mass articulation, and into
  the lateral mass of C1) (Fig. 3 -6B), C2 pars interarticularis or
                                P.46


 pedicle screws, and C2 laminar screws (Fig. 3 -6C). Extension of
 the construct to the subaxial spine with lateral mass screws can
 provide improved fixation in some cases where bone quality or
                 poor screw purchase is a concern.

     Table 3-1 Criteria Used to Diagnose
   Atlanto-Occipital Dislocation on Plain
                   Lateral Radiographs

 1. Powers Ratio


 â–ª Ratio of the distances from basion to the anterior wall of
 the posterior arch of C1 divided by the distance from the
 opisthion (posterior lip of the foramen magnum) to the
 posterior wall of the anterior arch of C1.


 ▪ Normal ≤0.9, Indeterminate 0.9–1.0, Abnormal >1.0


 â–ª Only sensitive for diagnosing anteriorly directed
 dislocations.


 2. Harris Rule of 12s
â–ª Two distances are measured: (a) distance from the base of
the dens to the clivus and (b) distance from a line draw from
the posterior wall of the dens to the clivus.


â–ª It is considered abnormal if the clivus is >12 mm above
the tip of the dens or 12 mm anterior to the posterior dens
line; therefore, the basis for rule of 12s. If the clivus is >4
mm posteriorly displaced behind the posterior dens line, this is
also consider abnormal and likely represents a posteriorly
directed dislocation.


â–ª Considered the most sensitive rule to diagnose all
directions of dislocation.


3. Dublin method


â–ª Measures the distance from the posterior ramus of the
mandible to the ventral aspect of the anterior ring of C1 and
the ventral aspect of the base of the dens.


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