Fractures of the Spine

Relevant Anatomy

The articulations and ligamentous supporting structures are as unique in the atlas and axis, as is their respective developmental anatomy. Occipital condyles project downward and articulate with the atlas. The predominant motion of this joint is flexion and extension, and 50% of total cervical spine motion in this plane occurs at this joint. The atlantooccipital joint has more of a horizontal orientation, and the occipital condyles are small relative to adults, perhaps explaining the increased risk (2.5 times) of atlantooccipital dislocation in children as compared with adults. The odontoid process projects upward from the body of the axis, articulating with the posterior aspect of the anterior arch of the atlas. The odontoid is secured in this position by the transverse ligament, which spans from one side of the anterior arch of the atlas to the other, passing posterior to the odontoid process. This ligament functions as the primary stabilizer, preventing anterior translation of the atlas and dislocation of the atlantoaxial joint. The secondary stabilizers are the paired alar ligaments, which arise from each side of the dens and attach to the occipital condyles, functioning as checkrein ligaments with head rotation. In addition, the apical ligament arises from the tip of the dens and attaches to the foramen magnum. The facet joints between the atlas and axis are more horizontally oriented to permit rotation of the atlas and head.

The vertebra in the subaxial cervical spine articulate at five points: paired facet and uncovertebral joints and the intervertebral disk. The facet joints in the subaxial cervical spine are relatively horizontal, averaging 30 degrees of inclination at birth and increasing to 60 to 70 degrees at maturity. The thoracic and lumbar vertebrae articulate with one another via paired facet joints and the intervertebral disks. The thoracic vertebrae articulate with ribs through costochondral articulations. Other supporting structures include the interspinous/supraspinous ligament, ligamentum flavum, posterior longitudinal ligament, and anterior longitudinal ligament.

The spine typically assumes adult characteristics by the age of 8 to 10 years, and until that time, children tend to be more susceptible to upper cervical spine (above C3) injuries. There are two main reasons for the increased incidence of upper cervical spine injuries in this younger age group. The head is disproportionately large, creating a large bending moment in the upper cervical spine that shifts the fulcrum of motion to the axial (C2-C3) region of the spine as compared with C5-C6 in the older child. The spine is also inherently more mobile in the upper cervical region. The factors unique to younger children that contribute to the increased mobility include the presence of generalized laxity of the interspinous ligaments and joint capsules, underdeveloped neck musculature, thick cartilaginous end plates, incomplete vertebral ossification (wedge-shaped vertebral bodies), and shallow-angled facet joints, particularly in the upper segments (between the occiput and C4). As a consequence, subluxation/dislocation and spinal cord injuries without fracture are more common than fractures in this age group.

Incidence and Prevalence

Analysis of the Kid’s Inpatient Database (KID) has noted that the prevalence of spine injuries for children and adolescents has increased from 77 to 108 per million population over the time period from 1997 to 2009. The older adolescent group (15–19 years old) had the highest prevalence at 345 per million population. Approximately 15% of those with spinal injury also sustained neurologic injury, of which 87% occur in the older adolescent group. In 2009, the incidence of spinal cord injury (SCI) was estimated at 24 per million in the population under 21 years of age. However, the true incidence of pediatric spine injury may be higher than reported because of failure to recognize these injuries. Aufdermaur found evidence of fractures of the spine at autopsy in 12 of 100 children over an 8-year period. Seven injuries occurred in the cervical spine, four in the thoracic spine, and one in the lumbar spine. Importantly, only one of the 12 subjects had been suspected of having a spine fracture before necropsy.

Mechanism of Injury

Although these injuries are rare, a high index of suspicion is warranted in polytraumatized children, especially those with head injuries. Approximately 25% to 50% of children with a cervical spine injury have associated head trauma, and as a consequence of this comorbidity, the mortality rate is higher in children with spine injuries than their adult counterparts. Associated injuries most commonly involve the thorax, abdomen, head, and appendicular skeleton, and are present in 42% to 65% of children and adolescents with spinal trauma.

In older children, sports injuries, diving accidents, and gunshot injuries are the most common causes. A review of 300,394 emergency department visits from 1999 to 2008 found that 23% of pediatric cervical spine fractures were sports related. At the 17 Pediatric Emergency Care Applied Research Network (PECARN) hospitals, sports were responsible for as many cervical spine injuries as motor vehicle accidents among children age 8 to 15 years from 2000 to 2004.

The most common mechanisms of injury in young children are motor vehicle accidents, pedestrian-vehicle accidents, falls, or nonaccidental trauma (NAT) (child abuse). Polk-Williams reviewed the National Trauma Data Bank (NTDB) from 2001 to 2005 for patients younger than age 3 years that were injured via blunt trauma. The incidence of cervical spine injury was 1.6%, and the most common mechanisms were motor vehicle crashes (MVCs) (66%) or falls (15%).

In infants and young children, NAT is a significant cause of injury to the spine. NAT was identified in 3.2% of spinal injuries at a level 1 pediatric trauma center over an 8-year period. The mechanism was NAT in 19% of children aged 3 years or younger and 38% for those under the age of 2 years. These injuries are often associated with other typical stigmata of child abuse, including fractures of the skull, ribs, or long bones, and cutaneous lesions. The cervical spine is a common location of spine injuries in abused children (73%), and multilevel injuries are frequent. Upper cervical ligamentous injuries, avulsion fractures of the spinous processes, fractures of the pars or pedicles (most commonly C2), or compression fractures of multiple vertebral bodies are common patterns of injury and are thought to result from severe shaking or battering. Thoracic and lumbar injuries are less common. Displaced fractures through the thoracolumbar (TL) neurocentral synchondroses may occur in young children.

In neonates, birth trauma is the most common cause of injury to the cervical spine. Spinal column and spinal cord injuries occur in approximately 1 in 60,000 births and may be an unrecognized cause of death in newborns, as evidenced by necropsy findings of injury to the spinal cord in 10% to 50% of stillborn babies. Excessive distraction and/or hyperextension of the cervical spine are thought to be the most common mechanisms of injury, and may be associated with abnormal intrauterine position (transverse lie) or a difficult cephalic or breech delivery. When associated with cephalic delivery, the injuries tend to occur in the upper cervical spine and are caused by rotation. Injuries associated with breech delivery are thought to be caused by traction and occur in the lower cervical and thoracic spine. These injuries commonly occur in the absence of osseous injury. The diagnosis of SCI in neonates is often delayed and should always be considered in a neonate with hypotonia or cardiopulmonary instability or in an older infant with decreased tone, a nonprogressive neurological deficit, and no history of familial neurological disorders. Diagnosis can be made with either bedside ultrasound or MRI. Prevention of this injury is preferable. Recognition of intrauterine neck hyperextension in association with breech position may allow for a planned caesarean delivery, which may reduce the risk of SCI.

Initial Evaluation and Transport

Proper care of pediatric spine injuries begins at the scene of the accident with an appropriate index of suspicion. It should be assumed that a polytraumatized child has a spine injury until proven otherwise and appropriate precautions and immobilization undertaken. Children should be initially placed in a well-fitting cervical collar and immobilized on a spine board. In the event that commercial adult collars do not fit appropriately, sandbags or towel rolls can be placed on each side of the head to prevent motion. The prehospital triage algorithm endorsed by the Center for Disease Control for patients with a suspected cervical spine injury indicates that those with altered mental status (Glasgow Coma Scale [GCS] score <15) or paralysis should be directly transported to a trauma center. Improved neurologic outcomes and reduced mortality have been noted for pediatric patients who were directly transported to a pediatric trauma center following a cervical spine injury, after adjusting for injury severity. However, local hospitals should not be bypassed during transport if supportive care interventions such as airway management are not available from emergency medical services. Once the child arrives in the emergency room, every effort should be undertaken to evaluate the child expeditiously. The spine backboard is for transport/transfers only and should be removed from beneath the patient as soon as possible to prevent skin breakdown.

Herzenberg et al were the first to note that transport of young children (<8 years of age) on a standard adult spine board tended to cause excessive flexion of the cervical spine as a result of the disproportionately large head diameter relative to the chest in this age group. The obvious concern is that the flexed position of the spinal column could potentially jeopardize the cervical spinal cord, particularly if the mechanism of injury is related to a flexion force, which is often the case in motor vehicle accidents. Therefore, to obtain neutral position during transport, they recommended using a pediatric spine board with a cutout for the occiput or building up the child’s torso with blankets on a standard spine board. Alternatively, a standard spine board can be used placing a towel role under the shoulders to allow the head to drop into slight extension ( Fig. 10.3 ).

In a subsequent study, Curran et al prospectively evaluated methods of positioning the child to achieve neutral alignment of the cervical spine after trauma. They measured sagittal alignment on supine lateral radiographs in 118 pediatric trauma patients and determined that only 60% were within 5 degrees of neutral alignment. They suggested that younger children might need more relative chest elevation to avoid flexion of the head and cervical kyphosis following immobilization. These findings were confirmed by Nypaver et al, who determined in their study that children under 4 years old required an average of 5 additional millimeters of elevation of the torso than those older than 4 years to achieve neutral cervical spine alignment.

Although it is not known how alignment of the cervical spine during transport impacts outcome, it seems prudent to avoid flexion of the neck by following the recommendations of Herzenberg et al regarding spine board immobilization, keeping in mind that the very young may need additional elevation to achieve neutral alignment. A pediatric-sized cervical collar and appropriate positioning may not be enough to ensure neutral alignment of the cervical spine in young children. As a practical guideline for proper positioning of a child on the spine board during transport, the external auditory meatus should be aligned with or slightly posterior to the shoulders.

Cervical Spine Considerations

Clinical evaluation of a child suspected of having a spinal injury may be hampered by an inability to obtain accurate historical information and the unreliability of the physical examination. Children are often frightened, usually unable to describe pain, and either unable (altered mental status, age) or unwilling to cooperate with an examiner. The likelihood of missing a cervical spine injury has been reported to be increased almost 23-fold in children who are incapable of verbal communication for whatever reason, and therefore, a thorough and careful examination is essential when evaluating a polytraumatized child. The PECARN investigators identified eight risk factors for cervical spine injury in children presenting after blunt trauma: altered mental status, focal neurologic findings, neck pain, torticollis or limited range of motion, substantial torso injury, preexisting condition predisposing to cervical spine injury, diving injury mechanism, and high-risk MVC. A high-risk MVC was defined as a head-on collision, rollover accident, ejection from the vehicle, death within the same accident, or speed greater than 55 miles per hour. Historically, several mechanisms of injury are considered to be risk factors for overt or occult injury to the cervical spine: falls from a distance greater than the height of the child, pedestrian- or cyclist-motor vehicle accidents, and unrestrained occupant-motor vehicle accidents. The presence of head or facial trauma or loss of consciousness are also considered to be risk factors. Neck pain, guarding, and torticollis are the most reliable signs of an injury to the cervical spine in children. Extremity weakness, sensory changes (numbness or tingling), bowel and bladder dysfunction, and, less frequently, headaches, seizures, syncope, and respiratory distress are signs heralding injury to the spinal cord ( Box 10.1 ). If any of these conditions are present, immobilization of the cervical spine should be continued or initiated until imaging studies can be completed and the spine cleared.

The entire spine, from occiput to the sacrum, should be palpated while considering that spinal injuries can occur at multiple levels and are noncontiguous in up to 38%. Approximately 16% of noncontiguous spinal injuries may be initially overlooked, and one must maintain a high index of suspicious for other injuries. During the examination, the cervical collar should be carefully removed with an assistant stabilizing the head so that the patient or examiner does not inadvertently move the head. Cervical spine injuries often present with torticollis, so it is important to note the position of the head and the presence of asymmetry in alignment. The anterior and posterior neck is examined for lacerations and wounds. The cervical spine is palpated anteriorly and posteriorly for the presence of tenderness or interspinous widening. The collar is reapplied, and attention is directed to the TL spine.

Thoracolumbar Spine Considerations

The possibility of injury to the TL spine should always be suspected in children who are comatose, have a distracting injury, or are not verbal because of age. The thorax and abdomen need to be inspected for signs of trauma. Abdominal injuries, particularly those of the small bowel, are associated with flexion-distraction injuries of the TL spine and are often heralded by the presence of contusions or abrasions caused by lap belts. The patient should be log rolled while keeping the head and neck in alignment with the rest of the spine and trunk. During this maneuver, cervical in-line traction should be avoided, particularly in young children because of the increased risk of ligamentous and atlanto-occipital (A-O) injuries. The TL spine should be palpated along the spinous processes for evidence of tenderness, interspinous widening, or malalignment. The finding on physical examination of midline or paravertebral pain alone is predictive of the presence of a fracture of the TL spine with a sensitivity of 87% and specificity of 75%. Evaluation of the entire TL spine is critical so as not to miss a noncontiguous fracture, and a thorough neurological examination is important, given that 20% to 30% will have a have a deficit.

Neurological Examination

For all suspected spine injuries, an accurate baseline neurological examination should be carefully documented in patients who are conscious and cooperative. The sensory examination should include evaluation of light touch, pain, and proprioceptive function. Pain and temperature sensation are mediated by the spinothalamic tract that traverses the anterolateral column of the spinal cord. This can be assessed by using a clean needle to test pinprick sensation and an alcohol pad for temperature discrimination. Light touch and proprioceptive (position) sensation are functions of the posterior spinal columns. Light touch may be tested by stroking the extremity with a piece of paper and proprioception by asking the patient to determine directional change in the position of a finger or toe.

Dermatomal patterns of sensation correlate with the spinal nerve roots exiting specific anatomic levels of the spinal cord ( Fig. 10.4 ). C1 and C2 innervate the occipital region; C3 and C4, the cape of the neck; C5, the deltoid region; C6, the radial aspect of the forearm; C7, the long finger; C8, the ulnar border of the hand; and T1, the medial border of the arm. The chest and abdomen are innervated by the T2-T12 nerve roots. Specifically, T4 provides sensation at the nipple line; T10, the umbilicus; and T12, the inguinal ligament. In the lower extremities, the pattern of sensory innervation mirrors the embryonic rotational maturation of the limbs. L1 and L2 contribute innervation below the inguinal ligament to medial thigh; L3 provides sensation to the anterior midthigh; L4, to the knee region and medial calf; L5, to the lateral calf and first web space; and S1, to lateral aspect and sole of foot. The perineal region is innervated by the S3-S5 roots. Preservation of function at this level, referred to as “sacral sparing,” is important because it indicates that some of the spinal tracts are still intact and that the injury to the spinal cord is incomplete and therefore associated with a better prognosis for neurologic recovery.

Motor function should be graded on a scale of 0 to 5, with grade 0 indicating complete paralysis; grade 1. trace function; grade 2, full range of joint motion with gravity eliminated; grade 3, antigravity function; grade 4, function against slight resistance; and grade 5, normal strength against resistance. The level of SCI can be assessed by the presence or absence of function in key muscle groups. In the upper extremities, C5 innervates the muscles responsible for elbow flexion; C6, wrist extension; C7, wrist flexion; C8, finger flexion; and T1, finger abduction. In the lower extremities, L2 innervates hip flexion; L3, knee extension; L4, ankle dorsiflexion; L5 great, toe extension; and S1, ankle plantar flexion.

Deep tendon reflexes should be graded as absent (0), hypoactive (1), normal (2), or hyperreflexic (3). In the upper extremities, the biceps tendon reflex is mediated by the C5 nerve root, brachioradialis by C6, and the triceps by C7. In the lower extremity, the patellar tendon reflex is mediated by L4 and the Achilles tendon by S1.

The abdominal, Babinski, and bulbocavernosus reflexes should also be assessed. The abdominal reflex is performed by dividing the belly into four quadrants, with the umbilicus at the center. When the skin in each of the quadrants is stroked, the umbilicus should deviate in that direction. Absence of a response may signify an upper motor neuron lesion, whereas asymmetrical loss of the reflex may indicate a localized lower motor neuron lesion. The Babinski test is performed by stroking the lateral plantar aspect of the foot. A pathologic response is indicated by an up-going great toe and is indicative of an upper motor neuron lesion.

The bulbocavernosus reflex is an important test to determine the status of an injury to the SCI. The test is done by performing a digital rectal examination while simultaneously applying traction on an in-dwelling Foley catheter (or squeezing the glans penis or clitoris). Presence of the reflex is indicated by concurrent contraction of the anal sphincter and heralds the end of spinal shock. Spinal shock is a transient phenomenon that occurs within the first 24 hours of SCI and is thought to be caused by swelling about the neural structures within the spinal column. Once spinal shock has passed, as indicated by return of the bulbocavernosus reflex, the status of the SCI can be predictably characterized. This reflex is less reliable with injuries around the conus medullaris (T12-L2), as the afferent nerve fibers that mediate the reflex lie within the zone of injury and may be directly affected. As a consequence, return of the reflex may take much longer in this group of patients. Additionally, all patients with a significant spinal injury should have an evaluation of bladder function using postvoid straight catheterization.

When an accurate neurological examination cannot be obtained because of the child’s age or altered mental status, findings that may suggest a SCI in the initial evaluation period include flaccidity, diaphragmatic breathing without the assistance of accessory muscles, priapism, and the presence of clonus. ^. Evaluation of a patient in this setting should include inspection and palpation of the spine from the occiput to sacrum, assessment of motor and sensory function by ability to withdraw from painful stimuli, and testing of deep tendon, abdominal, Babinski, and bulbocavernosus reflexes.

Radiology of the Spine

Plain Radiography, Cervical

Plain radiography of the cervical spine has been studied most extensively because of the length of time it has been available. A single supine lateral cervical radiograph with visualization of all seven cervical vertebrae, including the occipitocervical and cervicothoracic junctions, has a reported sensitivity of approximately 80% in the pediatric population. Lally et al found that all seven cervical vertebrae were seen in only 57% of children on the initial cervical spine series, usually because of difficulty in visualizing the cervicothoracic junction. Visualization of the cervicothoracic junction can be improved with traction or the so-called swimmer’s view, in which the arm is extended overhead. The addition of AP and open-mouth odontoid x-rays increases the sensitivity of plain radiography to approximately 94% if adequate images can be obtained. However, the open-mouth odontoid can be especially challenging to obtain in the young child. Buhs et al performed a multiinstitutional retrospective review on children under 16 years old with a documented cervical spine injury. Standard AP and lateral x-rays confirmed the diagnosis in 13 of 15 children younger than 9 years old. In none of the 15 patients did the open-mouth odontoid view provide any additional information. In only one of 36 patients aged 9 to 16 years old was the open-mouth odontoid deemed to be beneficial, identifying a type III odontoid fracture. The authors concluded that the open-mouth odontoid view was not helpful in children less than 9 years old. Instead, they recommended use of computed tomography (CT) to evaluate the upper cervical spine from the occiput to C2. Similarly, Garton et al noted that for children younger than 8 years, the use of CT (occiput to C3) in combination with radiographs was more sensitive (94%) than radiographs with flexion/extension views (81%) or radiographs alone (75%).

The PECARN investigators reviewed a multicenter retrospective cohort of children younger than 16 years who sustained bony or ligamentous cervical spine injury after blunt trauma. Among 186 children with cervical spine injury who had adequate radiographs, 18 injuries were missed for a sensitivity of 90%. Only 4 of the 18 injuries not identified by radiographs would be considered “not clinically significant” by the NEXUS study group criteria; the remainder were clinically important injuries such as multilevel burst fractures and A-O dislocation. ( Box 10.3 )