Epidemiology

The estimated annual cost of spine injuries, including inability to work and health care costs, exceeds $5 billion in the United States.¹

In the emergency department (ED), all trauma victims are screened for vertebral fractures, ligamentous disruptions, and spinal cord injuries because of the potentially devastating neurologic consequences of overlooking these injuries. Patients with a delayed diagnosis of spinal fracture are 7.5 times more likely to sustain secondary neurologic deficits.² Neurologic deficits from spinal cord injury may be subtle and can easily be missed if not specifically evaluated. Adding to these difficulties, plain film radiographs of the spine, though an adequate screening tool for other fractures, can miss 23% to 42% of cervical spinal fractures^3,⁴ and 13% to 50% of lumbar fractures.^5,⁶

Pathophysiology

In the setting of spinal trauma, the bone, ligaments, spinal cord, and vascular structures may be injured. Anatomically, the vertebral bony spine can be divided into structural columns. The cervical spine is traditionally divided into two columns—anterior and posterior. The anterior column consists of the load-bearing vertebral bodies, intervertebral disks, anterior longitudinal ligament, and posterior longitudinal ligament (Fig. 75.1). The posterior column consists of the more posterior structures, including the pedicles, laminae, and transverse and spinous processes (Fig. 75.2).

Fig. 75.1 Bony anatomy of a typical lower cervical vertebra (C3-C7): superior axial view with the anterior aspect oriented upward and the posterior aspect oriented downward.

Fig. 75.2 Bony anatomy of a typical thoracic and lumbar vertebra (T1-L5): superior axial view with the anterior aspect oriented upward and the posterior aspect oriented downward.

In contrast, the thoracic and lumbar vertebral spines are divided into three columns based on the modified Denis model—anterior, middle, and posterior (Fig. 75.3). The anterior column consists of the anterior longitudinal ligament, the anterior two thirds of the vertebral body, and the intervertebral disk. The middle column consists of the posterior longitudinal ligament, the posterior third of the vertebral body, and the intervertebral disk. Any disruption of the middle column predisposes a patient to significant spinal cord injury because the middle column abuts the spinal canal. The posterior column consists of the remaining posterior structures.

Fig. 75.3 Schematic diagram illustrating the lateral view of the anatomic columns of the cervical and thoracic/lumbar spine.

Note that the cervical spine’s anterior column is composed of the same structures as the thoracic/lumbar spine’s anterior and middle columns.

The C1 and C2 vertebrae are anatomically unique (Fig. 75.4). C1 (atlas) is a ring-link structure without a vertebral body. It articulates superiorly with the occipital condyles. This articulation allows 50% of normal neck flexion and extension. C2 (axis) projects the dens superiorly to articulate with C1. The transverse ligament tethers the dens to the anterior arch of C1. This atlantoaxial articulation allows 50% of normal neck rotation left and right.

Fig. 75.4 Bony anatomy of the upper cervical spine (C1 and C2): posterolateral view.

The C1 lateral masses articulate with the occipital condyles. The C2 dens projects cephalad, articulates with the C1 anterior arch, and is stabilized by the C1 transverse ligament.

The spinal cord spans from the foramen magnum to the L1 level, whereupon the spinal cord tapers into the conus medullaris and cauda equina, a collection of peripheral lower lumbar and sacral nerve roots. Because the spinal cord is thickest in the cervical spine, there is relatively less spinal canal space in the cervical levels than in the thoracic or lumbar spine. Thus spinal cord injuries occur more frequently with cervical spine trauma than with thoracic or lumbar spine trauma. The neurologic dermatomes can help localize the injury (Table 75.1).

Table 75.1 Individual Spinal Sensory Dermatomes, Motor Function, and Reflex Arcs

The vertebral arteries branch off the subclavian arteries and course superiorly within the transverse foramina of C2 to C6. These arteries then merge to form the basilar artery.

Presenting Signs and Symptoms

Patients with vertebral fractures usually have significant midline spinal tenderness on palpation. High-risk findings include spinal soft tissue swelling, ecchymosis, and step-off misalignment of the spine. Pain radiating along a dermatomal distribution suggests an associated radiculopathy. Thoracic spine fractures are uncommon because the articulating ribs provide stability to the spinal column; however, the thoracolumbar junction (encompassing the T10 to L2 vertebral levels) is commonly injured because the spine curvature changes from the kyphotic thoracic spine to the lordotic lumbar spine.

Patients with spinal cord injuries may have a spectrum of findings ranging from subtle neurologic deficits to grossly obvious paralysis. Spinal cord injuries should be suspected in any trauma victim who complains of neck or back pain, especially pain exacerbated by movement. Neurologic symptoms suggesting spinal cord injury include numbness, tingling, paresthesias, focal weakness, and paralysis. Other worrisome symptoms include urinary or fecal incontinence and urinary retention. Unconscious patients and those with impaired consciousness secondary to intoxication may harbor occult spinal cord injuries. Physical examination should focus on the spine and areas where associated injuries may occur (Tables 75.2 and 75.4).

Table 75.2 Physical Examination Findings Associated with Vertebral Fractures and Spinal Cord Injuries

INJURY	PHYSICAL EXAMINATION AREA	ASSOCIATED FINDINGS
Vertebral fracture	Spine	Tenderness of the neck and/or back. Examine the entire spine because vertebral fractures may occur in multiples.
	Neurologic	See spinal cord injury below.
	Chest	Thoracic spine fractures: Check for chest tenderness, unequal breath sounds, and arrhythmia, which are suggestive of an associated intrathoracic injury or myocardial contusion.
	Abdomen/pelvis	Thoracolumbar and lumbar spine fractures: Check for abdominal or pelvic tenderness. For instance, up to 50% of patients with a transverse process fracture⁷ and 33% of patients with a Chance fracture⁸ have concurrent intraabdominal pathology. A transverse area of ecchymosis on the lower abdominal wall (seat belt sign) increases the chance of an abdominopelvic injury.
	Extremity	Thoracolumbar and lumbar spine fractures: Check for calcaneal tenderness because 10% of calcaneal fractures are associated with a low thoracic or lumbar fracture. Mechanistically, these areas are fractured as a result of axial loading.
Spinal cord injury	Neurologic, motor (anterior column)	Assess motor function on a scale of 0 to 5 (see Table 75.3). motor level is defined as the most caudal segment with at least 3/5 strength. Injuries to the first eight cervical segments result in tetraplegia (previously known as quadriplegia); lesions below the T1 level result in paraplegia.
	Neurologic, sensory (spinothalamic tract)	Assess sensory function via pinprick and light touch on the following scale: 0 = absent; 1 = impaired; 2 = normal. The sensory level is defined as the most caudal segment of the spinal cord with normal sensory function. The highest intact sensory level should be marked on the patient’s spine to monitor for progression.
	Neurologic, sensory (dorsal column)	Assess vibratory sensory function on a scale of 0 to 2 by using a tuning fork over bony prominences. Assess position sense (proprioception) by flexing and extending the great toe.
	Neurology, deep tendon reflex	On a scale of 0 to 4, assess the deep tendon reflexes in the upper (biceps, triceps) and lower (patellar, Achilles) extremities (see Table 75.4).
	Anogenital	Assess rectal tone, sacral sensation, signs of urinary or fecal retention or incontinence, and priapism. Also check the anogenital reflexes: an anal wink (S2-S4) is present if the anal sphincter contracts in response to stroking the perianal skin area. The bulbocavernosus reflex (S3-S4) is elicited by squeezing the glans penis or clitoris (or pulling on an inserted Foley catheter), which results in reflexive contraction of the anal sphincter.
	Head-to-toe examination	A spinal cord injury may mask a patient’s ability to perceive and localize pain. Imaging of high-risk areas, such as the abdomen, and areas of bruising or swelling may be required to exclude occult injuries.

Table 75.3 Graded Assessment of Motor Function

GRADE	ASSESSMENT ON PHYSICAL EXAMINATION
0	No active contraction
1	Trace visible or palpable contraction
2	Movement with gravity eliminated
3	Movement against gravity
4	Movement against gravity and resistance
5	Normal power

Table 75.4 Graded Assessment of Deep Tendon Reflexes

GRADE	ASSESSMENT ON PHYSICAL EXAMINATION
0	Reflexes absent
1	Reflexes diminished but present
2	Normal reflexes
3	Reflexes increased
4	Clonus present

Spinal shock is a neurologic phenomenon resulting from physiologic transection of the spinal cord. It results in flaccid paralysis and loss of reflexes below the level of the spinal cord lesion. Spinal shock is temporary, commonly lasting for 24 to 48 hours, although it can persist for weeks. Patients suffering from spinal shock may appear (clinically) to have a complete spinal cord injury only to “miraculously” recover once the spinal shock has passed. Termination of spinal shock is identified by return of segmental reflexes; anogenital reflexes are the earliest to recover.

Neurogenic shock may occur in patients with cervical or high thoracic spinal cord injuries. It is a neurocardiovascular phenomenon resulting from impairment of the descending sympathetic pathways in the spinal cord. As a result, vasomotor tone is lost and visceral and peripheral vasodilation and hypotension ensue. Diminished sympathetic innervation to the heart also occurs and results in relative bradycardia despite the presence of hypotension.

Differential Diagnosis and Medical Decision Making

Indications for Cervical Spine Imaging

In the year 2000, in the hope of reducing the number of low-risk patients undergoing cervical spine plain film radiography, a multicenter study by the National Emergency X-radiography Utilization Study (NEXUS) group validated a set of five low-risk criteria for determining which patients do not require radiographic imaging if all the criteria are met (Box 75.1). This clinical decision tool demonstrated a sensitivity of 99.6% and a specificity of 12.9% for detecting clinically significant cervical spine fractures. It was thus extrapolated that 4309 (12.6%) of the 34,069 patients enrolled could have avoided plain film radiography.⁹

Box 75.1

NEXUS Low-Risk Criteria for a Cervical Spine Injury

A patient does not require cervical spine radiographic imaging if all five of the following low-risk conditions are met:

1. No posterior midline neck pain or tenderness

2. No focal neurologic deficit

3. Normal level of alertness

4. No evidence of intoxication

5. No clinically apparent, painful distracting injury *

NEXUS, National Emergency X-radiography Utilization Study.

From Hoffman JR, Mower WR, Wolfson AB, et al. Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma. N Engl J Med 2000;343:94-9.

^* Defined as a condition thought by the clinician to be producing pain sufficient to distract patients from a second (neck) injury.

Following development of the NEXUS criteria, the Canadian Cervical-Spine Rule (CCR) was developed (Fig. 75.5). The validated sensitivity and specificity for this decision rule were 99.4% and 45.1%, respectively.¹⁰

Fig. 75.5 Canadian Cervical-Spine Rule (CCR) algorithm for clinical clearance of the cervical spine.

The green box signifies a low-risk, negative work-up and clinical cervical spine clearance. Orange boxes signify a moderate-risk condition, and the red box signifies a high-risk condition, both of which require plain film radiography. ED, emergency department; GCS, Glasgow Coma Scale; RR, respiratory rate; SBP, systolic blood pressure.

(Data from Stiell IG, Clement CM, McKnight RD, et al. The Canadian C-Spine Rule versus the NEXUS low-risk criteria in patients with trauma. N Engl J Med 2003;349:2510-8.)

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