BACKGROUND

Cervical spine fractures are seen in approximately 5% of trauma patients being evaluated at level I trauma centers.

 

Dislocations and displaced fractures require reduction and frequently surgical stabilization.

 

This chapter focuses on the cervical fractures that often require reduction and the closed and open techniques used to manage them.

 

GENERAL PRINCIPLES OF CLOSED REDUCTION

Traction

 

Application of longitudinal traction assists in the reduction of cervical spine fractures through ligamentotaxis and the ability to apply rotational moments to the cervical spine.

 

Traction can be performed urgently in the emergency room.

 

Successful reduction requires an understanding of the biomechanics of both injury and reduction.

 

Traction is contraindicated in extension distraction injuries and type IIA hangman's fractures (see later section).

 

Placement of a towel roll between the scapulae can help to raise the head off the bed and allow for better control of the flexion or extension moment.

 

Low weight (10 pounds) should initially be placed in order to ensure that there is no craniocervical instability or unsuspected distraction.

 

Weight is generally added in 10-pound increments with lateral radiographs obtained every 10 to 15 minutes after adding weight in order to allow for the viscoelastic tissues to creep and for the muscles to fatigue. Serial neurologic examinations should also be performed and documented with each addition of weight.

 

 

 

FIG 1 • A,B. Gardner-Wells tongs are to be placed with pins approximately 1 cm above the pinna in line with the external auditory meatus, below the equator of the skull. Anterior halo pins are placed over the lateral third of the eyebrow in order to avoid the supraorbital and supratrochlear nerves, whereas posterior pin sites are posterior to the pinna, below the equator of the skull.

 

 

If not successful, open reduction in the operating room is generally indicated.

 

Gardner-Wells Tongs

 

Available in stainless steel and titanium. Stainless steel tongs offer the advantage of being able to safely use more weight, whereas titanium tongs are magnetic resonance imaging (MRI) compatible yet are limited in the

amount of weight they can safely support (no more than 50 pounds).6

 

Imaging of the skull (plain films or computed tomography [CT] scan) should be obtained prior to pin placement to ensure there are no skull fractures.

 

Pin placement is extremely important. The pins should generally be placed 1 cm above the pinna, in line with the external auditory meatus and below the equator of the skull (FIG 1). Placement more anteriorly results in an extension moment, whereas placement more posteriorly results in a flexion moment (sometimes desirable for facet dislocations).

 

The pin sites should be prepped with Betadine. Because these pins are temporary, the hair does not need to be shaved. Lidocaine is injected subcutaneously and subperiosteally at the planned pin sites.

 

Pins should be tightened until the indicator protrudes at least 1 mm, which corresponds to 30 pounds of compression at the pin site. Undertightened pins can disengage and cause scalp lacerations. Do not overtighten pins, as penetration of the inner table of the skull can occur.

 

Gardner-Wells tongs are temporary devices used for reduction. Use of halo ring traction should be considered if a halo is to be used for definitive management, although the amount of weight that can be applied to a halo ring is also less than

 

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what can be added to stainless steel Gardner-Wells tongs. We generally prefer to perform a reduction using Gardner-Wells tongs and then convert to a halo if surgery is going to be delayed, and the patient needs to be stabilized in the interim.

 

Halo Vest Application

 

Most halo vest systems are now MRI compatible.

 

Proper application of the ring is essential to prevent nerve injury, skin problems, and provide a method of immobilization with long-term durability.

 

At least two providers familiar with halo application are required.

 

The first step is to size the vest and the ring using the manufacturer's instructions. The vest should extend down to the level of the xiphoid and be snug but allow access to the skin. The ring should fit as close to the skull as possible without contacting the skin at any point.

 

The patient can be logrolled to place the posterior portion of the vest.

 

One person then holds the halo ring in place, ensuring that it does not contact the ears or the head, is symmetrically and appropriately aligned, and is below the equator of the skull.

 

Another person then plans the pin placement (see FIG 1). The two anterior pins are generally placed 1 cm cranial to the lateral third of the orbital rim to avoid the supraorbital and supratrochlear nerves. The pins can be placed into the eyebrow in patients concerned about scar cosmesis. The posterior pins are generally placed 1 cm above the helix of the ear, posterior to the external auditory meatus, and below the equator of the skull.

 

If the halo is going to remain in place for an extended period, the posterior pin sites should be shaved prior to starting the procedure. The pin sites should be prepped with Betadine, and lidocaine should be injected subcutaneously and subperiosteally.

 

While one person holds the ring in place (various devices such as suction cups and blunt pins can be used to assist with this), the other person screws the pins in until they all just contact the skin. Opposing pins should then be tightened simultaneously, going back and forth between the two pairs. The pins should be tightened to 8-inch pounds using either a torque-limiting breakaway applicator or a torque wrench.

 

The halo ring can then be attached to traction using the appropriate metal bail or to the uprights of the halo vest. The head should be positioned appropriately, and radiographs should be obtained to determine if the alignment is appropriate.

 

Pins should be retightened to 8-inch pounds in 24 to 48 hours.

 

Loose pins can be retightened once and should then be replaced through another hole if they loosen again.

 

Meticulous pin site care is required, although pin site infection can still occur. If infection is present but the pin is still tight, it can be treated with local care and oral antibiotics. If the pin loosens in the presence of infection, it should be replaced.

 

Bivector Traction

 

Bivector traction allows for simultaneous control of longitudinal traction and a flexion moment using a specially designed traction apparatus on a RotoRest bed (FIG 2).

 

The patient is positioned on a RotoRest bed with the head pad removed and shoulder roll in place to allow for freedom of motion of the head in the sagittal plane.

 

 

 

FIG 2 • Bivector traction with Gardner-Wells tongs. Two cables are used in order to adjust anterior and superior traction individually in order to affect a reduction.

 

 

Longitudinal traction is applied to the ring using an S-clip and anterior traction is applied via a cord attached to both of the pins. The two forces should initially be at 90 degrees to each other and can then be fine-tuned as needed.

 

Application of weight to the anterior pulley allows flexion to be “dialed-in” without having to change the position of the longitudinal traction, which can be difficult when heavy weight has been applied.

 

Bivector traction is indicated for most cervical spine reductions as it allows for more precise control of the traction vector than a single vector traction setup.

 

ODONTOID FRACTURES

DEFINITION

Fracture through the odontoid process that can be located from the tip of the dens to its base. Odontoid fractures are very common, accounting for 10% to 20% of all cervical fractures.19

 

 

ANATOMY

 

Two ossification centers fuse in utero, separating the dens ossification center from the primary ossification

center of the C2 vertebral body.31 These two ossification centers are separated by the dentocentral synchondrosis, which fuses by age 7 years. Another secondary ossification center, the ossiculum terminale, forms at the tip of the dens around age 9 years and fuses by age 13 years.

 

There is a rich vascular supply around the dens originating from the vertebral arteries and ascending pharyngeal artery. Although it was thought that type II dens fractures were predisposed to nonunion due to the

presence of a watershed area at the base of the dens, this has been shown to be untrue.20

 

The transverse atlantal ligament runs posterior to dens and connects to the posterior aspect of the anterior C1 ring bilaterally, preventing anterior translation of C1 on C2. The alar ligaments run from the tip of the dens to the skull base and restrict axial rotation. The weak apical ligament connects the tip of the dens to the occiput (FIG 3).

 

The C2 nerve root exits posterior to the C1-C2 joint in contrast to nerve roots below this level, which exit anterior to the facet joints. This puts the C2 nerve root at risk during posterior C1-C2 fusions.

 

 

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FIG 3 • Ligamentous anatomy of the upper cervical spine.

 

 

 

Fifty percent of axial rotation of the cervical spine occurs at C1-C2. A fracture of the dens results in atlantoaxial instability.

CLASSIFICATION

 

Anderson and D'Alonzo2 (FIG 4)

 

Type I fractures are avulsions of the apical portion of dens and generally represents a stable fracture with a high union rate.23 Occipital cervical dissociation should be suspected and ruled out.

 

 

Type II fractures involve the base of the odontoid and do not extend into the C2 body. These are generally considered unstable and are associated with a nonunion rate of at least 32% with nonoperative treatment.10 Type III fractures extend into the vertebral body of C2. These are relatively stable fractures that have a union

rate of 85% to 90% with nonoperative treatment.23

 

 

 

FIG 4 • Anderson and D'Alonzo classification of odontoid fractures. Type I involves the apex, type II involves the base of the dens, and type III enters the body of C2.

 

PATIENT PRESENTATION

 

Studies of traffic fatalities suggest that high-energy dens fractures could be associated with a mortality rate of up to 40%.9 The mortality rate in low-energy trauma is much lower.

 

The vast majority of patients who survive the initial injury present neurologically intact, although a wide variety of neurologic deficits associated with odontoid fractures have been described.2

 

Delayed presentation is common, and patients frequently present with neck pain and may have varying degrees of myelopathy. Respiratory depression and death have been reported.15

IMAGING

 

Plain films including an open mouth view of the odontoid should be obtained. However, nondisplaced dens fractures are frequently missed on plain films.4

 

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CT scan with thin cuts and sagittal and coronal reformations is the study of choice to detect and characterize odontoid fractures.

 

MRI is indicated in patients with neurologic deficit and can be useful to assess the ligaments of the upper cervical spine.

 

CLOSED REDUCTION AND TREATMENT

 

Gardner-Wells tongs are applied and bivector traction is used to reduce displaced odontoid fractures.35 If definitive treatment in a halo vest is planned, reduction can be performed with a halo ring. Although single vector traction can be used for the reduction of odontoid fractures, bivector traction allows for more precise control of the traction vector.

 

In posteriorly displaced fractures, there is a risk of respiratory compromise during the reduction maneuver that typically requires flexion of the neck. This is most likely due to compression of the airways by the retropharyngeal hematoma, although others have suggested that it is due to the displaced odontoid

compressing the respiratory pathways that run in the anterolateral portion of the upper spinal cord.11,33 As such, nasotracheal intubation of these patients prior to reduction is recommended.

 

 

 

FIG 5 • Fixation techniques for odontoid fractures. A. Anterior lag screw. B. Transarticular fusion. C. Harms fusion.

 

 

A relatively low amount of weight is generally required (20 to 30 pounds), and serial plain x-rays or fluoroscopy should be used with bivector traction to fine-tune the reduction.

 

Types I and III fractures rarely need reduction and can be managed with a halo vest or cervical collar. It has been recommended that type II fractures, particularly in elderly patients who cannot tolerate a halo vest, should be treated surgically.26

 

SURGICAL TREATMENT

 

Indicated for elderly patients with type II fractures and for failure to hold reduction or nonunion in younger patients.

 

Options include odontoid screw, transarticular C1-C2 fusion, and Harms posterior C1-C2 fusion (FIG 5). Posterior C1-C2 wiring is an older technique that also had acceptable

 

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results, although a lower fusion rate than transarticular fixation.13 Anterior screw fixation allows for some preservation of C1-C2 rotation, although it is associated with a higher rate of technical problems and nonunions compared to posterior C1-C2 fusion.43

 

OUTCOMES

In type II fractures, union rates are approximately 51% with collar treatment, 65% with halo vest orthosis, 82% with odontoid screw fixation, and 93% with posterior C1-C2 fusion.21

In type III fractures, collar immobilization results in a union rate of approximately 92% compared to 95% with halo vest orthosis.21

 

 

COMPLICATIONS

In patients older than 70 years old, inpatient mortality can be as high as 35%.30

In patients older than 65 years old treated with a halo vest orthosis, mortality can be as high as 42%, primarily due to pneumonia and cardiac arrest.37

Operative treatment of dens fractures in the elderly is also associated with high mortality rates of 40% with anterior screw fixation and 22% for posterior C1-C2 fusion.17,30

Anterior screw fixation can result in nonunion and screw cut out, particularly in elderly, osteoporotic bone.3 Posterior screw placement at C1 and C2 can result in vascular injury to the vertebral or internal carotid arteries.22

PEARLS AND PITFALLS

 

 

Bivector traction

• Can be extremely helpful in the reduction of displaced odontoid

fractures

Posteriorly

displaced fractures

• Should be intubated prior to closed reduction

Elderly patients

with a halo vest

• Treatment is associated with high morbidity and mortality in elderly

  patients, so operative treatment is often favored.

• We prefer a posterior Harms C1-C2 fusion in these patients.

 

TRAUMATIC SPONDYLOLISTHESIS OF THE AXIS (“HANGMAN'S FRACTURE”)

DEFINITION

Fracture through the C2 pars interarticularis. A similar lesion is seen in judicial hangings, although the mechanisms and outcomes are obviously quite different.

 

 

 

ANATOMY

 

C2 is a unique vertebra in that it serves as the transition from the upper cervical spine to the lower cervical spine.

 

The superior articular processes (SAPs) are anterolateral to the spinal canal, biconcave, articulate with the inferior articular processes (IAPs) of C1, and allow for rotation around the dens. The IAPs are posterolateral to the spinal canal and articulate with the SAPs of C3. The pars connects the superior and IAPs of C2 and is an area of frequent injury due to its relative weakness (FIG 6).

 

The vertebral artery runs through the C2 foramen on the lateral aspect of the C1-C2 joint.

 

The spinal canal is quite capacious at C2, explaining the low rate of neurologic injuries with fractures at this level.

 

PATHOGENESIS AND CLASSIFICATION

 

The most commonly used classification is Levine and Edward's28 modification of Effendi's classification system (FIG 7).

 

Type I fractures are nondisplaced (<3 mm) and nonangulated vertical fractures just posterior to the vertebral body that are parallel and symmetric to each other. These typically result from hyperextension and axial loading. The discal and ligamentous structures are generally intact, and these represent stable fractures.

 

Type IA, or atypical, fractures are nondisplaced (<3 mm) and nonangulated vertical fractures that are asymmetric (ie, the fracture lines are located at slightly different locations in the neural arch and are not parallel). These typically result from hyperextension and lateral bending. These generally represent stable

fractures. Starr and Eismont36 also described two displaced “atypical” hangman's fractures that were associated with neurologic deficit due to the spinal cord becoming impaled on the posterior fragment at the fracture site.

 

Type II fractures are displaced (>3 mm), angulated fractures that tend to be vertically oriented just posterior to the vertebral body. The pars fractures occur with initial hyperextension, which is then followed by flexion which disrupts the disc, elevates the anterior longitudinal ligament (ALL) off of C3, and often fractures the anterosuperior corner of C3.

 

Type IIA fractures are angulated (often >15 degrees), minimally translated fractures that are oriented obliquely, running from anteroinferior to posterosuperior through the pars. The mechanism of injury is distraction-flexion, resulting in the pars failing in tension. The disc fails from posterior to anterior, and the ALL is usually intact. It is important to recognize this variant because traction will exacerbate the deformity rather than reduce it.

 

Type III fractures are typically type I fractures through the pars combined with a bilateral C2-C3 facet dislocation. The mechanism leading to type III fractures is unclear, but it has been hypothesized that a distraction-flexion injury resulting in facet dislocation occurs initially followed by an extension force that fractures the pars. Due to the discontinuity between the vertebral body and the dislocated facets, closed reduction generally fails, and this injury requires operative treatment.

 

 

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FIG 6 • A,B. C2 bony anatomy.

 

 

 

FIG 7 • A-D. Levine and Edward's classification of traumatic spondylolisthesis of the axis (hangman's fracture). Type I fractures are minimally displaced (<3 mm). Type II fractures are displaced (>3 mm), angulated fractures. Type IIA fractures are angulated but minimally translated, usually with an intact ALL. Type III fractures have an accompanying bilateral facet dislocation.

 

 

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PATIENT HISTORY AND PHYSICAL FINDINGS

 

The most common mechanism of injury is motor vehicle accident.

 

 

Neurologic injury is uncommon due to the large diameter of the spinal canal at this level, occurring in only 6.5%

of patients in one series.16 The majority of patients with neurologic injuries have type III fractures, although neurologic injury can also be seen in atypical type IA fractures due to asymmetric canal narrowing.

 

Concomitant fractures elsewhere in the spine are common, so the remainder of the spine needs to be assessed with physical examination and imaging.

IMAGING

 

Cross-table lateral radiographs generally demonstrate the fracture lines through the pars and the traumatic spondylolisthesis if present. The exception is the type IA fracture, in which the fracture lines are in different planes and are not always seen on the x-ray.

 

Type II fractures can reduce when the patient is supine, so upright x-rays should be obtained in patients with type I fractures. Some authors have even suggested physician supervised flexion-extension radiographs in neurologically intact patients with apparent type I fractures to ensure that it does not actually represent a type II

fracture.27

 

CT scan of the cervical spine should be obtained to better characterize the fracture and rule out other cervical spine fractures. Imaging of the thoracic and lumbar spine should also be obtained to rule out noncontiguous fractures, as multiple spine fractures are present in up to 30% of patients with traumatic spondylolisthesis of the

axis.18

 

MRI is indicated in patients with neurologic deficits or type III fractures, which must be evaluated for a disc herniation in association with the facet dislocation.

 

NONOPERATIVE MANAGEMENT

 

Type I and type IA fractures can be treated with a cervical collar for 3 months. Upright x-rays are obtained to make sure the fracture is not actually a type II fracture.

 

Type II fractures often are reduced by closed reduction. Because the mechanism causing displacement of these fractures is flexion and compression, reduction requires extension and traction.

 

This is generally best performed using halo ring traction, as it allows for conversion to a halo vest orthosis.

 

To obtain reduction, a towel roll is generally placed at approximately C6 to extend the spine, and traction is applied. Reduction is generally obtained with 25 to 40 pounds.

 

Following reduction, a halo vest orthosis is applied, and upright x-rays are obtained to ensure that reduction can be maintained with the halo vest.

 

In patients with more than 5 mm of anterior translation or 11 degrees of angulation, reduction is difficult to

maintain in the halo vest.41 These patients can be treated with prolonged skeletal traction (up to 6 weeks) followed by halo vest immobilization after the fracture becomes stable or with surgery. Many physicians forgo prolonged traction due to patient discomfort and cost and will accept fracture displacement while immobilized in a halo orthosis.

 

Type IIA fractures result from flexion-distraction, so traction is absolutely contraindicated and will increase the deformity. These fractures are characterized by angulation without translation and oblique fracture lines.

 

Type IIA fractures should be reduced with gentle hyperextension and axial compression. An acceptable reduction is less than 10 degrees of angulation. Prior to reduction, a halo ring should be placed and then attached to the halo vest with the neck in mild extension and compression in order to maintain the reduction. The halo vest is generally maintained for 3 months. Failure to obtain or maintain an acceptable reduction is an indication for surgery.

 

Type III fractures cannot be managed with closed treatment.

 

SURGICAL MANAGEMENT

Indications

 

 

For type II and type IIA fractures in which an acceptable reduction cannot be maintained with a halo vest, surgery is indicated. Open reduction and osteosynthesis with placement of C2 pedicle screws across the fracture site is the surgical treatment of choice.

 

A C2-C3 anterior cervical decompression and fusion (ACDF) is another option for fractures that lose reduction or go onto nonunion.

 

Type III fractures require open reduction and fixation of the facet dislocation and subsequent positioning of the head in an extended position if needed to reduce the spondylolisthesis.

 

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TECHNIQUES

• C2 Osteosynthesis

   

  A posterior approach is used, with Mayfield tongs or a halo ring attached to the operating table to hold the head in a reduced position.

   

  The posterior elements of C2 are completely exposed, and the isthmus of C2 is palpated to help guide screw placement. Care is taken to protect the C2 nerve root.

   

  Lag screws are placed across the fracture site using fluoroscopy guidance, if desired (TECH FIG 1).

   

   

   

  TECH FIG 1 • C2 osteosynthesis using pedicle screws placed across the pars fractures in traumatic spondylolisthesis of the axis (hangman's fracture).

• Open Reduction Internal Fixation of Facet Dislocation

 

The head is positioned in Mayfield tongs, and the posterior elements of C2 and C3 are completely exposed.

 

Towel clips or tenaculums are then used to reduce the dislocated facets, and any remaining spondylolisthesis is reduced by positioning the head in extension.

 

 

 

TECH FIG 2 • C2-C3 posterior fusion for type III traumatic spondylolisthesis of the axis (hangman's fracture) using C2 pedicle screws across the pars fractures and lateral mass fixation at C3 following open reduction of the facet dislocation.

 

 

Following reduction, C2 pedicle screws are placed across the fracture site using a lag technique to promote osteosynthesis of the pars fractures.

 

Lateral mass screws are then placed at C3 and connected to the C2 pedicle screws using rods.

 

The remaining cartilage in the C2-C3 facet joint is removed using a burr and bone graft applied in order to obtain a C2-C3 fusion (TECH FIG 2).

 

Alternatively, the pars fracture may be treated nonoperatively with halo immobilization.

 

 

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PEARLS AND PITFALLS

 

Types I and IA

fractures

• Stable and should not be overtreated

• A collar is sufficient.

Type IIA

fracture

• Must be identified and traction is absolutely contraindicated in these

  patients as it will increase the deformity.

• These patients should undergo closed reduction with gentle extension and axial compression.

Type III

fracture

• The only absolute indication for surgery.

 

 

OUTCOMES

 

The union rate for types I and IA fractures approaches 100%.27

Some patients can develop C2-C3 facet arthritis due to cartilage damage that occurs with hyperextension at the time of injury.

Patients with type II fractures usually develop anterior ankylosis at C2-C3 due to the injury to the disc and elevation of the ALL. If this fails to occur, nonunion can occur, although the rate of this is unknown.

Patients with type III fractures typically have worse outcomes if they suffered a neurologic injury. No longterm outcome data on this group are available, likely due to the very low incidence of this injury.

 

 

COMPLICATIONS

Nonunion is rare and can be treated with C2 pedicle screw osteosynthesis or a C2-C3 ACDF. Injury to the spinal cord or vertebral artery can occur with improper C2 pedicle screw placement.

Characterization of the course of the vertebral artery is necessary prior to performing this procedure.

 

 

SUBAXIAL FACET DISLOCATIONS

DEFINITION

Facet dislocations occur when the IAP of the cranial vertebra dislocates anterior to the SAP of the caudal vertebra.

This occurs with a distraction-flexion mechanism.

Distraction-flexion injuries can present as subluxations with gapping of the facet joint, “perched” facets with the IAP resting on the SAP or “jumped” facets where the IAP has dislocated anterior to the SAP.

These injuries can be unilateral or bilateral.

 

 

ANATOMY

 

The cervical spine can be viewed as having an anterior column (ALL, vertebral body, disc, posterior longitudinal ligament [PLL]) and a posterior column (pedicle, lateral masses, facet joints, facet capsules, ligamentum flavum, inter- and supraspinous ligaments) that provide stability.

 

The facet joints in the subaxial cervical spine are oriented in the coronal plane and inclined approximately 45 degrees horizontally (FIG 8). This orientation allows for axial rotation, lateral bending, and flexion-extension, with coupled lateral bending and axial rotation.

 

The cervical nerve roots exit directly laterally and exit above the pedicle of the vertebra for which they are named (ie, C7 nerve root exits above the C7 pedicle), posterior to the vertebral artery.

 

The vertebral artery runs through the foramina transversarium from C2 through C6 but generally not through the foramen at C7. It is located anteriorly to the medial aspect of the lateral masses.

 

PATHOGENESIS AND CLASSIFICATION

 

 

A popular classification for subaxial cervical spine injuries was published by Allen et al1 in 1982. Facet dislocations are classified in the distractive flexion (DF) phylogeny (FIG 9).

 

The subaxial cervical spine injury classification (SLIC) system would classify this injury as a translational

cervical injury with facet dislocation, with disruption of the discoligamentous complex with or without a neurologic deficit.

 

The majority of facet dislocations are due to shallow diving injuries or motor vehicle accidents in which the head is axially loaded anterior to the midsagittal plane, resulting in flexion and posterior distraction.

 

A biomechanical model demonstrated that the posterior ligamentous structures fail first, allowing for flexion and separation of the facet joints. As anterior column soft tissue

 

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structures fail, including the PLL and posterior anulus, anterior translation and facet dislocation can then occur.32

 

 

 

FIG 8 • Osteoligamentous anatomy of the cervical spine.

 

 

 

FIG 9 • Allen and Ferguson's DF phylogeny. DF-1 injuries involve subluxation of the facet joints. DF-2 is a unilateral dislocation. DF-3 is a bilateral dislocation. DF-4 is 100% anterior translation of the vertebra.

 

 

In Allen's DF phylogeny, DF stage 1 (DF-1) injuries include facet subluxation without dislocation, DF-2 injuries are unilateral facet dislocations with approximately 25% anterior translation of the cranial vertebra on the caudal vertebra, DF-3 injuries are bilateral facet dislocations with approximately 50% anterior translation, and DF-4 injuries represent 100% anterior translation (ie, the “floating vertebra”).

 

PATIENT HISTORY, PHYSICAL FINDINGS, AND INITIAL MANAGEMENT

 

There is a high rate of spinal cord injury (SCI) associated with facet dislocations, at least 25% with unilateral dislocations and over 50% with bilateral dislocations.42

 

Patients should undergo full trauma resuscitation with immobilization of the cervical spine in the field.

 

The use of methylprednisolone in SCI patients is controversial. The National Acute Spinal Cord Injury Study (NASCIS) 2 and 3 trials concluded that SCI patients presenting within 8 hours of injury should receive methylprednisolone (30 mg/kg bolus followed by 5.4 mg/kg/hour infusion for 24 hours if presentation is within 3

hours of injury and for 48 hours if presentation is between 3 and 8 hours after injury).7,8 However, these recommendations are based on minimal neurologic improvements found only in subgroup analyses, and many

centers have abandoned the use of steroids in SCI.24

 

An attempt should be made to maintain mean arterial pressure above 85 mm Hg for the first 5 to 7 days following SCI in order to maintain perfusion of the injured cord.5

IMAGING

 

Standard radiographic evaluation of a suspected cervical spine injury includes anteroposterior (AP), lateral, and open mouth views. In order to be sufficient, both the occipitocervical and the cervicothoracic junctions should be visualized.

 

Most trauma centers now obtain CT scans of the cervical spine in all trauma patients because they are much more sensitive in diagnosing subtle cervical spine fractures and fractures at the occipitocervical and cervicothoracic junctions.25

 

MRI is indicated in all patients with facet dislocations to assess the status of the spinal cord, ligamentous structures, and the intervertebral disc. The timing of MRI relative to reduction is controversial. Many physicians experienced in the management of cervical dislocations advocate an immediate closed skeletal reduction in the absence of MRI only in an awake, alert, oriented, and cooperative patient in order to closely follow the patient's

neurologic status during the process of reduction.14,40

 

There is almost absolute consensus that patients with a complete SCI should also undergo immediate closed reduction prior to MRI because the potential downside neurologically is small compared to the potential benefit of immediate neurologic decompression. Obtunded patients should undergo MRI prior to closed reduction because they are unable to cooperate with serial neurologic examinations.

 

 

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All patients need an MRI prior to surgical treatment to assess the need for an anterior discectomy.

 

 

Imaging of the entire spine should be performed due to the high rate of noncontiguous injuries (10% to 15%).39

 

NONOPERATIVE MANAGEMENT

 

All patients with facet dislocations need to undergo reduction in order to decrease the pressure on the spinal cord as soon as possible. The timing of MRI relative to closed reduction is discussed earlier.

 

Most facet dislocations occur in the lower cervical spine, and large amounts of weight can be required (up to 140 pounds) to obtain a closed reduction. As such, stainless steel Gardner-Wells tongs should be used.

 

An initial flexion moment should be applied along with axial traction in order to unlock the facet joints. This may be accomplished with bivector traction, although positioning the tongs posterior to the external auditory meatus will also produce a flexion moment.

 

Once the facets are perched, the physician can then gently extend the patient's neck in order to obtain a reduction. This is done by using the treating physician's thumbs to control the traction pins while the other fingers are used to provide an anterior counterforce to the posterior aspect of the lower cervical spine. A towel roll between the scapulae and removal of the foam pad beneath the patient's head on the RotoRest bed can allow for unencumbered extension (FIG 10).

 

During the reduction maneuver, an assistant can decrease the amount of traction. If reduction is successful (it is oftentimes accompanied by a palpable clunk), the patient can be left with 10 pounds of traction in extension to control the head and maintain reduction.

 

 

 

FIG 10 • Reduction of C5-C6 bilateral facet dislocation. A. Injury film showing dislocated facets. B. Axial traction with slight flexion has been applied, and the facets are perched. C. Extension was applied at this point, resulting in reduction.

 

 

Reduction should be confirmed radiographically, and the patient's neurologic status should be documented. A decline in neurologic function with reduction suggests possible cord compression by herniated disc material.

 

An MRI should be obtained prior to going to the operating room in order to assess for the possibility of a herniated disc impinging on the cord. If present in a neurologically intact or incomplete patient, an anterior discectomy is indicated.

 

If operative treatment is delayed, application of a halo vest orthosis should be considered to maintain the reduction.

 

For unilateral facet dislocations, a reduction maneuver is often required.12 Following the application of traction, the physician must axially rotate the head away from the side of the dislocation while flexion is applied in order to unlock the facet. Once imaging suggests the facet is perched, a reduction maneuver can be performed in which the neck is extended and axially rotated toward the side of the dislocation.

 

SURGICAL TREATMENT

 

Facet dislocations represent unstable injuries, and surgical intervention should be strongly considered. A variety of situations can be encountered that necessitate different approaches to treatment (FIG 11).

 

If the dislocation is irreducible, the patient should be taken to the operating room for an open reduction and stabilization. An MRI should be obtained prior to going to the operating room in order to assess for a disc herniation and the need for an anterior discectomy prior to reduction.

 

For anesthesia, awake fiberoptic intubation avoids excessive cervical extension and allows for a neurologic examination after intubation. Neurophysiologic baselines are recorded after the administration of general anesthesia as well as after

 

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prone positioning and shoulder taping. We generally obtain prepositioning baselines in all patients, and it is required in neurologically intact patients or those with incomplete SCIs.

 

Neurophysiologic spinal cord monitoring during open reduction is extremely helpful. If a change in neurologic

status is detected, the reduction maneuver can readily be reversed, potentially avoiding permanent neurologic injury.

 

 

 

FIG 11 • Algorithm for treatment of facet dislocations.

 

 

Multimodality monitoring is preferred, including motor evoked potentials, somatosensory evoked potentials, and spontaneous electromyogram (EMG) recordings.

 

 

02

TECHNIQUES

Posterior Open Reduction

If the dislocation is irreducible with closed methods and there is no significant disc herniation, a posterior open reduction is favored because it allows direct access to the dislocated facet joints (TECH FIGS 3 and 4).

For prone positioning, the patient can remain in their halo ring or Mayfield tongs can be applied. The patient can then be rotated into the prone position on a Stryker frame or Jackson table. Traction can be

 

applied during the rotation maneuver in order to increase stability.

 

After prone positioning and establishment of neurophysiology baseline recordings, a standard subperiosteal dissection of the posterior cervical spine is performed.

 

Care should be taken to avoid violating the facet capsules and interspinous ligaments of levels not involved in the intended fusion.

 

The dislocated level can often be detected by a step-off between the spinous processes and the presence of hematoma and posterior ligamentous injury.

 

Once the dislocation is identified clinically and/or radiographically, the lateral masses are exposed completely.

 

The dislocation can be reduced by grasping the involved cephalad and caudal spinous process with a tenaculum or towel clip at the spinolaminar junction.

 

The neurophysiologist should be warned of the possibility of an acute signal change. If any significant neurophysiologic changes are detected, the procedure should be halted.

 

 

 

TECH FIG 3 • A-C. Posterior open reduction technique for unilateral facet dislocation. Tenaculums can be used to apply rotational and flexion moments to unlock the facet followed by axial traction and reduction.

 

 

Axial caudal traction is applied to the caudal tenaculum. A gentle distraction and kyphotic moment is applied to the cephalad tenaculum to disengage the dislocated IAP.

 

A rotational force may also be required for unilateral facet dislocations. The maneuver is applied until the IAP(s) of the cephalad vertebra is freed from the SAP(s) of the caudal vertebra.

 

After disengaging the IAP(s), reduction can be obtained by applying cranial traction to the cranial vertebra until the IAP(s) clear the SAP. Caudal traction is then performed to reduce the IAP(s) posterior to the

SAP(s).

 

If this maneuver fails to achieve reduction, a Penfield or nerve hook along with the traction maneuvers can be used to lever the dislocated IAP over the SAP. Care must be taken to avoid fracturing the articular processes.

 

The cranial edge of the SAP can also be trimmed using the burr in order to eliminate a barrier to reduction, although the surgeon should avoid overresection of the SAP as this decreases stability.

 

Following reduction, lateral mass or pedicle screws are then placed in the standard fashion at the level of the dislocation. A one-level fusion can be performed if there is no soft tissue injury at the adjacent levels and the lateral masses are intact and allow for good screw purchase. If these criteria are not met, additional levels must be included in the fusion.

 

Many surgeons use local bone and bone graft extender for the fusion, although autograft harvested from the iliac crest is widely used.

 

To achieve anatomic alignment, compression can be applied across the lateral mass screws.

 

 

03

 

 

 

TECH FIG 4 • A-C. Posterior open reduction technique for bilateral facet dislocation. Tenaculums can be used to unlock the facet joints with axial traction and slight flexion followed by extension to affect the reduction.

Anterior Open Reduction

 

Although posterior open reduction is generally preferred for unreducible facet dislocations, if a disc herniation is present, an initial anterior approach is required. If the dislocation can be reduced through an anterior approach following discectomy, a posterior procedure may be avoided.

 

The patient is positioned supine with a shoulder roll and the head supported in slight extension on a gel

roll.

 

 

Plain x-ray or fluoroscopy is essential to monitor the reduction maneuver. A standard ACDF approach is used.

 

Once adequate exposure had been obtained, a discectomy is performed along with resection of the PLL. A complete, aggressive discectomy prior to reduction is of paramount importance to reduce the risk of neurologic injury.

 

Vertebral body pins (Caspar or equivalent devices) are placed into the vertebral bodies, diverging from each other approximately 10 to 20 degrees in order to produce a bending moment.

 

Gently manipulating the pins into parallel orientation in the distraction device creates a flexion moment to unlock the facets. Subsequent distraction often results in perching of the facets.

 

The cranial vertebral body is then translated dorsally with leverage through an interbody distractor or Cobb in order to obtain reduction. This can be done with simple manual manipulation of the distraction pins or by placing a Cobb under the inferior endplate of the dislocated vertebra and applying a gentle superoposterior force once the facets are perched. Clearly, care must be taken to avoid overly aggressive reduction maneuvers or plunging into the spinal canal with the Cobb.

 

In the case of a unilateral dislocation, the distraction pins should be applied with a divergent angle in the axial plane to accentuate the rotational deformity as traction is applied in order to unlock the facets. For example, if the right C5-C6 facet joint is dislocated, the C5 pin would be placed rotated toward the right (in the opposite direction that the C5 vertebra is rotated) such that a rotational moment will be applied that will help to unlock the dislocation after traction is applied. Once the facet is perched, manual pressure or a Cobb can be used to affect reduction.

 

Following radiographic confirmation of reduction, an interbody structural bone graft and anterior plate are placed. In general, we prefer to use allograft in the traumatic setting to prevent creating a wound at the iliac crest harvest site that could be at higher risk of infection in the trauma population.

 

Autograft could be considered in patients at high risk of nonunion (ie, smokers).

 

We use traditional fixed plates rather than dynamic plates when treating trauma patients because we are usually fixing a single level, and there is no evidence that dynamic plates improve fusion rates in single-level cases. In addition, if an anterior-only construct is performed, a dynamic plate could allow for collapse into kyphosis due to injury to the posterior ligamentous complex that accompanies these injuries.

 

04

Stabilization following Reduction

 

If a successful closed reduction is performed, the surgeon must determine what approach to use for stabilization (ie, anterior, posterior, or circumferential).

 

Posterior fixation has been shown to be biomechanically superior to ACDF38; however, clinical results of

ACDF have been shown to be equivalent to posterior fusion even for bilateral facet dislocations.34 Posterior surgery is generally associated with more surgical morbidity and postoperative pain due to the stripping of the paraspinal muscles off the posterior elements.

 

Circumferential fusion is certainly the strongest construct and is preferred for bilateral facet dislocations by some authors. Additionally, it can avoid the need for multiple-level fusion, which is sometimes necessary if a posterior-only approach is used.

 

If an anterior approach is necessary to remove herniated disc material, an ACDF is probably sufficient. Posterior fixation can also be added to improve the strength of the construct.

 

If a posterior approach is needed to obtain reduction, posterior fixation alone is typically sufficient. An

ACDF can also be performed to strengthen the construct.

In cases where closed reduction is successful and there is no disc herniation, the approach is left to the surgeon's discretion.

 

 

Closed reduction

• Should be performed urgently, and prereduction MRI is not necessary in

awake, alert, cooperative patients who can comply with a neurologic examination

Closed reduction of

lower cervical spine facet dislocations

• Can sometimes require high amounts of weight (up to 140 pounds), but

efforts should be made to obtain a rapid closed reduction in order to decrease pressure on the cord and simplify surgical treatment

Preoperative MRI

• Always required to determine if a disc herniation is present

Open reduction

• Much easier to perform via a posterior approach, although reduction with

an anterior approach is technically feasible and often performed

PEARLS AND PITFALLS

 

 

COMPLICATIONS

Neurologic deterioration during closed reduction or surgery is a feared complication. This risk can be minimized with frequent neurologic examinations in an awake, alert, cooperative patient during closed reduction and neurologic monitoring during surgery.

Vertebral artery injury has been reported in up to 11% of patients with cervical spine injuries.29 However, the majority are asymptomatic and treatment is controversial. For patients who are symptomatic, anticoagulation is an option, but the risks and benefits of anticoagulation in the presence of a spine injury must be weighed.

Cervical SCI patients are at risk for many complications including deep venous thrombosis, decubitus ulcers, contractures, osteoporosis, and respiratory failure (particularly with higher SCI). Coordination of care with an SCI rehabilitation team is essential to avoid these and other complications.

OUTCOMES

The neurologic status of the patient is the main determinant of outcome.

Union rates following operative stabilization of facet dislocations are over 90%.34

 

 

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