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Pediatric spinal trauma

Description

Four generalized injury patterns have been recognized in pediatric spine trauma: fracture, fracture with subluxation, subluxation or dislocation alone, and spinal cord injury without radiographic abnormality (SCIWORA). While these injuries are rare and often carry a good prognosis, the mortality rate for certain of these injuries is relatively high.

Structure and function

 
         The pediatric spine undergoes significant change during the first fifteen years of life. The immature spine becomes progressively less mobile and progressively more adult-like as the child reaches adolescence. Several anatomical features present in the pediatric spine allow for increased mobility.

Early in life, the spinal synchondroses are open allowing greater movement within a given vertebral level, but most are fused by eight years of age. Greater cervical motion is afforded by the relatively horizontal orientation of the facets in the young spine. Upper cervical facets change their angulation from 30 degrees at birth to 60-70 degrees by adolescence. Similarly, the lower cervical spine changes orientation of facets from 55 degrees to 70 degrees. As the facets become more vertical, the spine becomes more restricted in movements. Children also have more wedge-shaped vertebrae than adults allowing for greater forward flexion. Anterior wedging less than 3mm is within normal limits and should not be mistaken for compression fracture. Lastly, the uncinate processes, which restrict lateral and rotational movement, are virtually absent in kids less than 10 years old.

In addition to osseous differences, the pediatric spine differs from the adult one regarding soft tissue structures too. There is relative ligamentous laxity (e.g. interspinous ligaments, posterior joint capsules, and cartilaginous end plates) and paraspinal musculature weakness in children, as these structures are often underdeveloped.

In young children, these properties allow the spine to lengthen to a much greater degree than the spinal cord resulting in a high incidence of spinal cord injury without vertebral column damage (higher incidence of SCIWORA in young). While the spinal column may stretch up to two inches before disruption occurs, the spinal cord may rupture with stretching of as little as one centimeter.

Moreover, while the fulcrum for cervical motion hinges on C2-C3 early in life, by age 10, the center of motion has changed to C5-C6. The biomechanical features of the immature spine result in a much higher prevalence of injury above C4 in children who are younger than eight years of age and progressively higher incidences of subaxial cervical, thoracic, and lumbar spine injuries with increasing age. 

Epidemiology

2-5% of all pediatric trauma involves injury to the spinal column or cord and 1-2% of all fractures occur at the spine. In Finland, the incidence of pediatric spinal injuries has been reported at 66 per 106 children per year. While the thoracolumbar region is most commonly affected in adults, the most common location for pediatric spinal injury is at the cervical spine with most studies reporting 40-80% of injuries occurring at this region. One recent study has suggested that while the proportion of injuries occurring at the cervical region is higher in younger children (less than 8 years old), the lumbar region may be most affected in older children. Several studies have confirmed that the level of spinal injury can be correlated to the age of the patient.

The age-adjusted incidence of cervical spine injury among US children has been reported at 74 per 106 children per year. However, a more recent study in Finland found a rate four times lower than this. There may be several possibilities to explain this finding but most likely, the difference may be attributed to advances in automobile safety regulations, as motor vehicle accidents are the leading cause of pediatric spine trauma. Much of the original epidemiological studies were from the 1950s-1990s and in the ensuing years, the introduction of better safety features for automobiles and car-seats may account for less frequent traumatic injury.

Regarding the spinal cord, the incidence of injury ranges from 1-4.6 per 106 children per year, and if pre- hospital fatalities are excluded, the incidence is closer to 1.9-2.4 per 106. The overall mortality rate for pediatric spinal trauma is likely about 4-8%, but some studies have reported a rate as high as 45-58% with 80% of those fatalities occurring in the setting of cervical spine trauma. This rate is higher than in adults likely because of the biomechanical properties of the immature spine and associated injuries in children. Older children have a higher risk of sustaining spinal injuries compared to younger ones with kids aged 0-9 and 15-17 having a 1% and 5% incidence of spinal injury after trauma respectively.   While increased flexibility in the pediatric spine may be protective in cases of minor trauma (where mobility allows for motion without injury), in cases of major trauma, that same mobility may lead to catastrophic outcome (as that mobility allows the cord to distract to dangerous lengths).

          Most reports have documented an equal distribution of spine trauma between boys and girls, but one study showed a ratio of 2:1, boys to girls.

Although not well reported, the distribution among injury patterns is as follows: fracture only occurs in 78% of cases, fracture with subluxation in 12%, subluxation or dislocation only in 6%, and in SCIWORA 3% of cases. Some of these values have widely disparate rates. For example, with a changing definition of SCIWORA with the advent of new imaging modalities, varying rates of its occurrence have been reported ranging from 4-50% of pediatric spinal cases. This disparity likely reflects whether the definition applies to the use of MRI or not (i.e. when no radiographic abnormality found on imaging includes MRI as well, the number is lower).

Clinical presentation

           

 

Biomechanical and anatomical features, such as increased head to body ratio, ligamentous laxity, muscle weakness, and facet orientation, place children at particular risk for upper cervical spinal injury. Atlanto-occipital injuries in children are often fatal and are associated with severe cord and brainstem damage. Yet, there have been some reports of patients surviving this injury with intact neurological function. Atlanto-axial instability (secondary to tear of the transverse ligament) is uncommon and tends to occur in younger kids as the properties of the immature spine tend to focus the load on the upper cervical spine.

         Injuries in children most commonly occur in the setting of motor vehicle collisions. One of the more frequent injuries seen is fracture of the odontoid. Similarly, pedicle fractures of C2 (hangman’s fractures) occur during hyperextension type injuries that may be seen with MVC.

         Subaxial spine injuries occur more frequently in older rather than younger children as the fulcrum of motion migrates from C2-3 to C5-6 as the spine develops. Thoracic and lumbar injuries are also more commonly seen in this population. These injuries include fracture-dislocations, burst fractures, simple compression fractures, facet dislocations, or fracture dislocations and posterior ligamentous injuries.

In addition to fracture and dislocation combinations, children with spine trauma may have no manifestation of injury radiographically but still have spinal damage. This entity has been called spinal cord injury without radiographic abnormality (SCIWORA). SCIWORA was initially defined as myelopathy secondary to trauma with no evidence of fracture or ligamentous instability on plan film or CT. While fractures or fractures with subluxation are more common in kids older than nine years, SCIWORA is more common in younger children. The average age of presentation with SCIWORA ranges from reports of 2.5 years old to some reports of 12 years old. It is more common in younger kids likely because of spinal elasticity that allows bones and ligaments, but not the cord, to stretch without damage. Younger children with SCIWORA almost always sustain complete spinal cord injuries while older children with SCIWORA (15-17 year olds) often have incomplete lesions, likely reflecting the mechanism of injury in the setting of increased head to body ratio and increased flexibility in young kids leading to more severe damage.

Complete lesions result in total loss of sensation and movement below the level of injury. Examples of incomplete lesions are the following:

-                anterior cord syndrome: injury to motor and sensory pathways in the anterior cord; patients can feel some sensation but movement and fine sensation is absent

-                central cord syndrome: injury to the nerves in center of cord leading to weakness or paralysis of the upper extremities and some sensation loss in arms; can have burning in cape-like distribution over upper extremities

-                Brown-Sequard syndrome: injury to one half of spinal cord with resultant loss of movement and some types of sensation below ipsilateral side of injury and loss of temperature and pain sensation below contralateral side of injury.

-                Cauda equina syndrome: injury to lumbosacral nerve roots with resultant loss of reflexes to affected limbs, loss of bowel/bladder control,

Patients with spine trauma may also present in spinal shock, referring to flaccidity and loss of reflexes that may make the cord appear functionless. Generally, return of function begins within 72 hours of injury with return of the bulbocavernosous reflex first (the lowest relex arc from S1-S3). Alternatively, patients may present in neurogenic shock. This scenario results from impairment of the descending sympathetic pathways resulting in loss of vasomotor tone and sympathetic innervation to the heart. It is characterized by the triad of hypotension, bradycardia, and peripheral vasodilation.

Red flags

-                ABCDEs for all trauma patients; thoroughly need to document complete neuro exam in cases of spine trauma

-                When board and collar a child, remember that the head is disproportionately large relative to the body so a backboard with a recess for the occiput or pads placed under torso are necessary to prevent flexion of cervical spine

-                Look for particular signs of associated injury such as a “seat belt sign” that may indicate GI or intrathoracic injury.

-                Maintain a high index of suspicion for spinal trauma/injury with children; do not clear c-spine until

 

Differential diagnosis

Almost half of all pediatric spine trauma will have an associated injury, with traumatic brain injury being the most commonly associated. Associated injuries significantly compound the morbidity and mortality of spinal trauma. Multiple studies have suggested that almost all fatalities in cases of spine trauma have an associated injury. Therefore, a high index of suspicion must exist for such injuries.

The most commonly associated injury has been craniocerebral injury. Several other associations have been found: increasing age has been correlated with an increased risk of other orthopedic injuries; boys are more likely to experience a GI system injury for any spine level; and thoracolumbar and lumbosacral injuries have shown an increased risk for GI injury.

Seat-belt injuries, also known as flexion-distraction injuries or Chance fractures are are commonly associated with other injuries. About half of all patients with these injuries have associated GI injuries including jejunal transection and small bowel perforation. They have also been reported in conjunction with aortic dissection.

In addition to other organ system injuries, multi-level spinal injury must be ruled out as well. Studies have reported up to 1/3 of patients presenting with multilevel spinal injury.

 

Objective evidence

Radiographic studies of the immature spinal column allow more complete evaluation of injuries, but must be interpreted with a thorough understanding of pediatric anatomy and biomechanics. Not all pediatric trauma patients need to be evaluated radiographically. If the patient is alert and conversant with no evidence of intoxication, if there is no midline tenderness, no neuro deficits, and no distracting injury, then radiographs are not necessary. Lee et al proposed the following ten risk factors for cervical spine injury for which if any are met, immobilization and radiographic evaluation are mandated:

1.    Unconscious patient

2.    Mechanism suggestive of possible cervical spine injury

3.    Neck pain

4.    Focal tenderness or inability to assess neck pain secondary to distracting injury

5.    Abnormal neuro exam

6.    History of transient neuro symptoms suggestive of SCIWORA (weakness, paresthesias, related to neck movement)

7.    Physical signs of neck trauma (ecchymosis, bruising or swelling)

8.    Unreliable exam secondary to substance abuse

9.    Significant head or face trauma

10.  Inconsolable child

When plain films are necessary, they must include AP and lateral views for all involved spinal levels and the addition of an open-mouth odontoid view for cervical spine injury (although, this view’s clinical utility has recently been questioned).

Radiographs of the cervical spine in cases of pediatric spine trauma may be difficult to interpret. Several normal variants may be confused with damage to the spine. Pseudosubluxation is seen commonly in children who are younger than eight years of age although, vertebral translation should not normally exceed 4 mm, should reduce on extension, and the alignment of the posterior spinolaminar line of Swischuk (line drawn along posterior arch from C1- C3 which should be smooth and continuous and should pass within 1 mm of the anterior cortex of the posterior arch of C2) should be preserved. The atlantodens interval (the distance between anterior cortex of the dens and the posterior cortex of anterior ring of atlas) may be lager in children and in those younger than 8 years old, may normally be between 3-5 mm, while in older children and adults it should be less than 3 mm.

Also, young children may have a relative cervical kyphosis which would be abnormal in an adult population.

Anatomic features can also complicate interpretation; persistence of cervical synchondroses can simulate traumatic injury as can congenital cervical fusions or deformities. Variations in odontoid development or synchondrosis closure are commonly misinterpreted on cervical radiographs. Differentiation between fractures and synchondroses can be made based on presence of subchondral sclerosis and smooth regular patterns of lucency, features not seen in fractures.

Despite the increasing use of MRI, flexion-extension radiographs remain important tools in the assessment of pediatric cervical injuries. Children are at increased risk for traumatic cervical instability with no osseous injury. They may be relatively uncooperative initially with an examination in the emergency department, and cervical range of motion may therefore be limited by paraspinal spasm or guarding. If the results of clinical examination and plain radiographs provide a relatively low index of suspicion, the completion of dynamic radiography in a delayed fashion can serve to rule out subtle instability patterns thus allowing the child to return to his or her accustomed activities and sports.

CT scans are generally recommended in cases of high-risk trauma, especially in cases with neurological deficits, neck tenderness, or equivocal physical exams. CT provides excellent delineation of osseous injury patterns which allow for evaluation of deformity, potential instability and assists with surgical planning.

When greater visualization of soft tissue and neural elements are needed, when plain films and CT are unrevealing in the setting of persistent neurological deficit or pain, or when a patient is uncooperative, multiply injured, or head-injured, MRI may assist in diagnosis.

         In addition to radiography, certain lab-work should be sent as for all trauma patients. A CBC to evaluate for potential blood loss, blood alcohol level and urine toxicology to evaluate for intoxication, radiographs of chest to evaluate for pneumo/hemothorax and aortic injury, FAST to evaluate for intrabdominal injury are all necessary.   For those children who are obtunded or have evidence of head trauma, a NCHCT is generally recommended.  For cases of thoracolumbar injury, in addition to basic trauma work-up, potential GI/GU injuries should be ruled out with studies including U/A (blood in urine) and plain films of abdomen looking free air in abdomen should be done.

Risk factors and prevention

The most common overall cause of pediatric spinal injury is motor vehicle accidents. 81% of patients who sustained a cervical spine injury were unrestrained or inappropriately restrained. By age, the most common mechanism among infants, toddlers, and adolescents is motor vehicle accidents, falls, and sports respectively. Advances in automobile and car-seat safety features as well as regulations regarding seat belt use and age/weight specific guidelines for car/booster seat use have resulted in a decrease in the incidence of pediatric spinal trauma. Moreover, improvements in protective gear used in adolescent sports have lead to a decrease in sport related injuries as well.

The utility and cost-benefit ratio of methylprednisone use to prevent cord damage after spine injury is still being debated. Based on the current literature, a recent Cochrane database review could not make formal recommendations for or against its use.

Treatment options

It is difficult to make categorical statements regarding treatment of spinal injury among pediatric trauma. Many cases may be treated non-surgically with the use of immobilization, often using collars or braces. Halo traction is also often recommended. One study reported a 30% rate of surgery among those who suffer spinal injury. In that study, the most common procedures were posterior lumbar spine stabilization, anterior cervical spine decompression and stabilization, and posterior thoracic spine stabilization (Table 2).

The indications for surgery in the pediatric patient are not well established and include non-reducible or grossly unstable injuries, significant subluxation without fracture, spinal cord compression in patients with incomplete neurological deficits, and persistently unstable injuries after non-operative therapy. Neurologically intact patients with radiographic evidence of spinal cord compression and patients with complete neurological injuries less than 24 hours after injury due to spinal cord compression may also be considered for surgical decompression.

         There is a dearth of prospective data on surgical intervention for pediatric spine trauma, with all of the recommended procedures guided by case reports. When early surgery is performed, optimal timing seems to be between 2 and 7 days after injury. Given the preponderance of concomitant injuries, a multidisciplinary approach, involving multiple surgical teams may be necessary. As a general rule for surgical approaches in immature children, posterior stabilization is advised as an anterior approach may compromise future growth. 

Table to follow

Outcomes

         Although there have been no prospective outcome based studies, most children who undergo non-surgical or surgical management of spine trauma do well.  The relatively good outcomes may be attributed to the plasticity of the young spinal cord and the recovery potential of immature bones and ligaments. But, the main predictor of outcome is the neurological status at the time of presentation; those with complete neurological injury rarely improve while those with mild to moderate deficits show the greatest potential for improvement.

Among children who suffer spine trauma, one study documented the most frequent complication as pneumonia (4%) followed by UTI (1%). The rates of complication in this study were higher in those undergoing surgery compared to non-surgical management but that may have been due to the severity of initial injury.  

Most patients may be treated non-operatively. Of the available data, only about 3% of patients will fail non-operative management. The rest usually heal without complication and may experience improvement in their neurological status. Non-surgical management with bracing has been associated with short-term complications such as skin breakdown and infection.

Those who undergo surgery for accepted surgical indications generally do well. Most patients who undergo instrumented fixation have callus formation, maintenance of alignment, stable fixation, and usual improvement in neurologic function at follow up. Some reported complications include infection, lack of fusion, and neurologic damage.

Spinal cord injury in children generally carries a good prognosis as well. About 2/3 of pediatric cervical spine injuries associated with neurological findings experience complete recovery of neurologic function. One study reported that 100% of children demonstrated improvement in neurologic function among those who suffered incomplete lesions. Overall, about 2/3 of children who sustain spinal cord injury can be expected to improve at least one ASIA grade.

In addition to neurologic compromise, the prevalence of spinal deformity among those who experience spinal cord injury has been reported to approach 100% (although some studies have reported the rate to be much lower, around 20%). Scoliosis is the most common deformity, followed by kyphosis and lordosis.

Key terms

 Pediatric spine, spinal cord, fracture, trauma, SCIWORA

Skills

 

-                ABCDE’s of trauma: Airway, Breathing, Circulation, Disability (neuro exam), and Exposure.

-                Skills performed in a trauma slot: CPR, IV placement, primary and secondary survey. Look for signs of cord damage and/or neurogenic shock (hypotension, bradycardia) which may necessitate fluids and pressors

-                Neuro exam (Disability) consists of evaluating sensation at each spinal level and motor function of each muscle group.

-                Sensation is evaluated on a 0-2 scale with 0 being no sensation, 1 being sensation intact but diminished, and 2 being normal sensation. Sensation is tested at each dermatomal level (see figure).

-                Motor is described on the ASIA scale as follows: 0- no contraction or movement, 1- minimal movement, 2- active movement but not against gravity, 3- active movement against gravity, 4- active movement against resistance, 5- active movement against full resistance.

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