Spinal injuries

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Chapter 70 Spinal injuries

There are few injuries that have a more devastating impact on both the patient and their family than spinal cord injuries (SCI). The physical, psychological and functional sequelae of permanent disability are immense. In addition, the economic cost to the individual and to society, with the loss of productivity and costs of hospitalisation, rehabilitation and ongoing care, are enormous.

AETIOLOGY

The incidence of SCI in developed countries is 12–53 new cases per million population per year (excluding deaths before reaching hospital).¹ There is some variation in the incidence and causes in different countries. About 80% of SCI are male, usually in the 15–35 years age group.

SCI are due mainly to motor car, motor bike and bicycle accidents (50%), falls (15–20%) and sporting injuries (10–25%).¹ Alcohol ingestion is frequently an associated factor. Work-related injuries account for 10–25%, and physical violence for 10–20% of SCI, especially from gunshot injury in the USA. Sporting and recreational injuries appear to be increasing (but with fewer now due to diving), and there is an increasing incidence of SCI in the elderly, especially from falls.² Ischaemic SCI is occasionally due to aortic injury or cross clamping. Pre-existing spinal pathology predisposes to SCI, including osteoarthritis, spinal canal stenosis, ankylosing spondylitis, rheumatoid arthritis and congenital abnormalities.

Fifty-five per cent of SCI are cervical (most at the C4–6 levels), with thoracic, thoracolumbar and lumbosacral injuries each being 15% of SCI. Forty-five per cent of SCI are complete and 55% incomplete. Between 20 and 60% of patients with SCI have significant associated injuries such as head and chest injuries.¹

PATHOGENESIS

SPINAL INJURY

CERVICAL SPINE

Injury to the cervical spine has been classified several ways ³^–⁵ relating to the mechanism of injury using the two-column concept. Differences appear to be due to the fact that compression of the anterior column is associated with distraction of the posterior column, and vice-versa. Injuries may be grouped according to the predominant mechanism of injury (Table 70.1) with these mechanisms having characteristic radiological patterns.

Table 70.1 Cervical spine injuries

Hyperflexion

Hyperflexion and rotation

Hyperextension

Hyperextension and rotation

Vertical compression or burst injury

THORACOLUMBAR SPINE

The classification of Denis ⁶ using the three-column concept of the spine has been widely adopted. Major injuries are classified as in Table 70.2.

Table 70.2 Major thoracolumbar spine injuries

Compression fractures

Burst fractures

Seat belt type injuries

Fracture dislocations

SPINAL CORD INJURY

Trauma to the spinal cord results in immediate primary and delayed secondary injury processes.

PRIMARY INJURY

Direct mechanical injury may produce focal compression, laceration or traction injury to the cord. Actual transection is unusual. Ischaemic injury may result from interference to the segmental spinal arterial supply.

SECONDARY INJURY

An understanding of secondary injury mechanisms has come from experimental SCI in animals.^1,⁷ Local hypoperfusion and ischaemia begin at the site of injury, extending progressively over hours from the site of injury in both directions. There is loss of spinal cord autoregulation, complicated by arterial hypotension with high SCI. Apart from ischaemia, other mechanisms may contribute to the secondary injury. These include the release of free radicals, eicosanoids, calcium, proteases, phospholipases and excitotoxic neurotransmitters (e.g. glutamate).

Petechial haemorrhages begin in the grey matter, progress over hours and may result in significant haemorrhage into the cord. There is oedema, cellular chromatolysis and vacuolation, and ultimately neuronal necrosis. Apoptosis, especially of oligodendrocytes, also occurs.¹ In the white matter vasogenic oedema, axonal degeneration and demyelination follow. Infiltration of polymorphs occurs in the haemorrhagic areas. Late coagulative necrosis and cavitation subsequently take place.

CLINICAL PRESENTATION

Spinal and spinal cord injuries should be suspected after severe trauma or head injuries, if there are motor or sensory symptoms or signs, or the patient reports neck or back pain.

NEUROLOGICAL ASSESSMENT

A detailed neurological examination is essential, including motor function, sensory function (spinothalamic and dorsal column) and reflexes, as well as anal motor function, sensation and reflexes. The vital capacity should be measured. This neurological examination provides the most useful information with respect to assessment of the SCI and to prognosis. However, it may be difficult to conduct on presentation due to head or other injuries, pain, alcohol or the administration of analgesic or other drugs.

In an alert patient SCI may be obvious with limb paralysis or weakness, numbness and absence of reflexes.

With a complete SCI there is muscle paralysis, with somatic and visceral sensory loss below a discrete segmental level. Spinal shock is usually present, with the additional features of muscle flaccidity, absence of tendon reflexes, vaso- and venodilatation, loss of bladder function and paralytic ileus. This term refers to a form of neurogenic ‘shock’ with temporary loss of somatic and autonomic reflex activity below the neurological level of injury. It usually lasts for 1–3 weeks before the recovery of distal reflex activity in the isolated cord segment.

TERMINOLOGY

The terminology for SCI has now been standardised.⁸

• Tetraplegia (preferred to quadriplegia) refers to impairment or loss of motor and/or sensory function in the cervical segments of the spinal cord due to damage of the neural elements within the spinal canal.

• Paraplegia refers to impairment or loss in the thoracic, lumbar or sacral segments of the cord, as well as conus and cauda equina injuries within the spinal canal.

• Neurological level is reported as the most caudal cord segment with normal motor and sensory function on both sides. As differences often exist it is preferred to describe the individual motor and sensory levels on each side (as the most caudal segments with normal motor and sensory function, respectively). In this context, normal motor function refers to a motor grade of 3, with all cephalad motor levels being grade 5.

• Skeletal level refers to the level with the greatest vertebral damage on X-ray.

• Complete injury refers to the absence of motor and sensory function in the lowest sacral segment.⁹ A zone of partial preservation exists if there is partial innervation of motor and sensory segments below the neurological level. This term is only used in complete SCI. If partial innervation of motor and sensory function is found below the neurological level and includes the lowest sacral segment (with anal sensation and voluntary external anal sphincter contraction) the injury is defined as incomplete. Grading of complete and incomplete SCI utilises the ASIA impairment scale⁸ (Table 70.3).

Table 70.3 American Spinal Injury Association (ASIA) impairment scale

Complete: No sensory or motor function is preserved in the sacral segments S4–S5

Incomplete: Sensory but not motor function is preserved below the neurological level and includes the sacral segments S4–S5

Incomplete: Motor function is preserved below the neurological level, and more than half of key muscles below the neurological level have a muscle grade less than 3

Incomplete: Motor function is preserved below the neurological level, and at least half of key muscles below the neurological level have a muscle grade greater than or equal to 3

Normal: Sensory and motor function is normal

INCOMPLETE SCI

Incomplete SCI tend to occur in characteristic syndromes.¹⁰

• The central cord syndrome is the most common, usually resulting from hyperextension injury to the neck, often in the elderly with a narrow spinal canal. There is disproportionate paralysis in the arms compared with the legs, and variable sensory loss.

• The anterior cord syndrome has extensive bilateral paralysis with loss of pain and temperature sensation, but preservation of sensory function in the posterior white columns.

• The Brown–Sequard syndrome is due to damage to one side of the spinal cord with loss of ipsilateral motor and proprioceptive function, as well as contralateral pain and temperature sensation. It usually results from penetrating injury.

• The conus medullaris syndrome is due to T12/L1 injury with damage to lumbar and sacral cord segments producing extensive paralysis in the legs of both upper and lower motor neurone type.

• The Cauda equina syndrome results from skeletal injuries below L1 with damage to the lumbosacral nerve roots resulting in lower motor neurone paralysis, and bladder and bowel areflexia.

• Spinal cord injury without radiological abnormality (SCIWORA) occurs mainly in children, but is now very uncommon with magnetic resonance imaging (MRI).

UNCONSCIOUS OR UNCOOPERATIVE PATIENTS

The neurological examination may be difficult if the patient is unconscious or uncooperative. In this case a number of signs may be helpful in drawing attention to a SCI as in Table 70.4. Confirmation of SCI may be established by MRI or somatosensory-evoked potentials (SSEP).

Table 70.4 Signs of SCI in unconscious or uncooperative patients

Response to pain above, but not below a suspected level

Flaccid areflexia in the arms and/or legs

Elbow flexion with the inability to extend suggestive of cervical SCI

Paradoxical pattern of breathing with indrawing of upper chest on inspiration (in the absence of upper respiratory tract obstruction or chest injury)

Inappropriate vasodilatation (in association with hypothermia, or in the legs but not the arms with thoracolumbar SCI)

Unexplained bradycardia, hypotension

Priapism

Loss of anal tone and reflexes

SPINE

Alert patients will report neck or back pain and tenderness with spinal injuries. A palpable gap may be felt between the spinous processes of thoracolumbar vertebrae. However, a spinal injury is readily overlooked in association with head or other major injuries, or alcohol ingestion.

ASSOCIATED INJURIES

CERVICAL SPINE INJURY/TETRAPLEGIA

Overall with major trauma the incidence of cervical spine injury (CSI) is 1–3%.¹¹ However, 2–10% of patients with head injuries have a CSI. The more severe the head injury, the more likely is CSI to be present. Patients with head injuries should be assumed to have a CSI until proved otherwise. Of patients with a cervical SCI, 25% have some degree of head injury, with 2–3% having a severe injury.^1,¹²

THORACOLUMBAR SPINE INJURY/PARAPLEGIA

Chest injuries are often present and are difficult to assess with the inability to take an erect chest X-ray, and the presence of a mediastinal haematoma associated with the vertebral injury. Contrast-enhanced helical CT of the chest may be used to assess other chest injuries, and to exclude an aortic injury,¹³ although aortography may be preferred for this purpose.

Abdominal injuries are difficult to diagnose if there is a SCI. However, they should be suspected if there is excessive hypotension, referred shoulder pain, or free gas or fluid seen on X-ray of the spine or chest. Abdominal CT, diagnostic peritoneal lavage or ultrasound may be used to delineate these injuries.¹⁴

IMAGING

PLAIN X-RAYS (Figure 70.1)

Plain X-rays remain the primary screening method for suspected spinal injuries in symptomatic patients, except in unconscious or multitrauma patients. However, the absence of a detectable abnormality does not exclude a spinal injury. Lesions may not be seen if the views are inadequate or of poor technical quality, or the observer is inexperienced. Even without these limitations, plain X-rays of the neck frequently miss fractures and subluxations,^15,¹⁶ and a high index of suspicion should be maintained. Adequate views of the entire cervical spine from the base of the skull down to and including the C7–T1 junction should always be obtained. Abnormalities of the prevertebral soft tissues are often present and indicative of subtle injuries.⁴

Figure 70.1 Plain lateral X-ray of the cervical spine showing a C5/6 dislocation.

With the cervical spine the three-view trauma series is standard in most hospitals (Table 70.5). This consists of lateral, anteroposterior (AP) and odontoid (open mouth) views. A five-view series with supine oblique views has been recommended as improving the diagnostic yield,¹⁷ but other studies show no difference in the detection rate. Lateral and AP views are standard screening views for the thoracolumbar spine.

Table 70.5 Basic examination of plain X-rays of cervical spine

Must include occipital condyles to C7–T1 junction
Lateral is the most important view and will show most injuries
Check for: Alignment: Vertebral bodies Spinous processes Pedicles in AP view Laminae in oblique views Bony changes: Bony integrity, density, contour Vertebral body height Pedicles, laminae Spines, transverse processes Atlas, dens Spaces: Intervertebral disc spaces Interspinous spaces Predental (atlas–dens) space Facet joints Atlanto-axial, atlanto-occipital joints Soft tissues: Prevertebral soft tissue shadow