Abstract
The unstable cervical spine requires prompt recognition, evaluation of neurologic deficits, evaluation and treatment of systemic effects, and meticulous airway management to ensure optimal outcome from a cervical spine injury. Here we present a typical case, review different types of cervical instability, review appropriate preoperative, intraoperative, and postoperative management of a patient with an unstable cervical spine. We also present an algorithm for evaluation of cervical spine injury.
Keywords
airway management, atlantoaxial subluxation, congenital cervical spine instability, evoked potentials, inflammatory cervical spine instability, neurogenic pulmonary edema, spinal shock, unstable cervical spine injury
Case Synopsis
A 79-year-old man presents with C1 and odontoid fractures sustained in a fall down stairs while he was intoxicated. He was found at the bottom of the stairs 2 days after the injury. In addition to alcoholism, the patient has a history of hypertension and smokes one to two packs of cigarettes per day. The patient is not oriented to time, place, or person and has inappropriate verbal responses, but there is no apparent neurologic deficit.
Problem Analysis
Definition
Cervical spine stability is defined as the ability of the spine to maintain relationships between vertebrae during physiologic loading, so as not to damage contained neural structures. Cervical spine instability occurs when physiologic loading causes patterns of vertebral displacement that jeopardize the cervical spinal cord. The muscles of the neck, along with ligamentous structures, intervertebral disks, and osseous articulations, all play a role in cervical spine stability. Upper cervical spine stability may be affected by trauma, congenital disorders, and inflammatory diseases, all of which may result in atlantoaxial instability ( Box 27.1 ).
Congenital
Down syndrome
Odontoid anomalies
Mucopolysaccharidoses
Acquired
Rheumatoid arthritis
Juvenile rheumatoid arthritis
Ankylosing spondylitis
Psoriatic arthritis
Enteropathic arthritis
Crohn’s disease
Ulcerative colitis
Reiter’s syndrome
Trauma
Odontoid fracture
Ligamentous disruption
Traumatic Cervical Spine Instability
The cervical spinal cord is particularly prone to injury because of spinal flexibility and the mass of the head. The spinal cord is injured when the ligaments, muscles, and osseous structures fail to dissipate the energy of impact. Transmission of this energy results in microhemorrhage in the spinal cord central gray matter and loss of neurotransmission in the surrounding white matter. A biochemical cascade that destabilizes the neurologic axon membrane and promotes vasospasm creates a secondary injury pattern after the initial insult. Also, primary cervical spinal cord injury leads to altered autonomic tone, loss of autoregulation, depressed cardiovascular function, and hypotension.
A traumatic atlantoaxial dislocation (atlantodental interval of >3 mm in adults older than 18 and >5 mm in children) occurs with forced displacement of the neck such as those sustained during tackling in football or rugby and often is associated with head injuries. If atlantoaxial dislocation or a type II odontoid fracture (fracture occurs at the base of the odontoid between the transverse ligament and the body of C2) occurs, there is a very high likelihood of ligamentous injury. The transverse ligament normally allows no more than 3 mm of anteroposterior translation between the odontoid and the anterior arch of the atlas. If disruption of this ligament occurs, displacement of the odontoid reduces the space available for the spinal cord ( Fig. 27.1 ). In the normal spine, the space available for the spinal cord is about 20 mm. Cord compression does not occur when the space is greater than 18 mm, but it does occur if it is less than 14 mm.
Congenital Cervical Spine Instability
Congenital or chromosomal anomalies may contribute to cervical spine instability, mostly atlantoaxial instability by means of either odontoid hypoplasia or laxity of the transverse ligaments. The stabilizing action of the odontoid during extension is lost with odontoid hypoplasia, and subluxation of the atlas occurs on the axis anteriorly, reducing the space available for the spinal cord. Laxity of the transverse ligament is present in 14% to 22% of patients with trisomy 21. Excessive laxity of other joints correlates with the presence of atlantoaxial instability. Other congenital conditions with skeletal dysplasia, such as Goldenhar syndrome, spondyloepiphyseal dysplasia, and Morquio (mucopolysaccharidosis type IV) syndrome, are high at risk for atlantoaxial instability.
Inflammatory Cervical Spine Instability
Cervical spine involvement is common in inflammatory arthropathies such as rheumatoid arthritis (RA) and ankylosing spondylitis. The pathophysiology of RA involves pannus formation, with subsequent destruction of cartilage and subchondral bone, along with ligamentous laxity and instability. Atlantoaxial subluxation occurs in about 25% of patients with RA. It occurs more frequently in men, in those with disease of long duration, in patients with subcutaneous nodules or seropositive disease, and in those receiving steroid therapy. Vertical subluxation of the odontoid process through the foramen magnum may also occur in patients with RA.
Epidemiology
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Cervical spine injuries occur in 1.5% to 7.7% of all major trauma cases.
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The peak distribution of injury is at the C4–C6 levels.
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The most common age of injury is 19 years. Nearly a quarter of all injuries occur between ages 17 and 22 years (24.3%), nearly half of all injuries occur between ages 16 and 30 (48.9%), and 10.7% of all injuries occur at age 60 or older. The average age at injury has increased from 29 years during the 1970s to 42 years currently. Males account for approximately 80% of new spinal cord injury (SCI) cases.
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Most cervical spine injuries result from motor vehicle accidents (MVAs; 42%–56%), falls (19%–30%), or gunshots and sports-related activities (6%–7%).
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MVAs and sports-related activities account for the majority of cervical spine injuries in younger patients, whereas falls account for most cervical spine injuries in older patients.
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Young children are less susceptible to cervical spine injury because they weigh less and have more cartilage than adults do; vulnerability increases with age.
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Cervical spine injuries in children younger than 2 years are exclusively C1–C2 injuries, because facet joints at this level are more horizontal and the ligaments more lax.
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Diseases of the respiratory system are the leading cause of death (67.4% of these are cases of pneumonia). The second leading cause of death is infective and parasitic diseases. These are usually cases of septicemia (89.2%) and are usually associated with decubitus ulcers, urinary tract infections, or respiratory infections.
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The cumulative 10-, 20-, 30-, and 40-year survival rates for patients with SCI are 81.71%, 68.05%, 52.99%, and 37.44%, respectively.
Recognition
History and Physical Examination
Recognition of a cervical spine injury begins with the history. High-risk causes (e.g., motor vehicle accident, fall, long-standing RA) or known chromosomal abnormalities may alert the clinician to the presence of an unstable cervical spine. For example, a patient with RA may complain of clicking on neck flexion and pain and stiffness of the neck. An alert trauma patient may complain of neck pain or tenderness. An alert patient without neck pain or neurologic deficit does not require further cervical spine evaluation, immobilization, or special precautions during airway manipulation. If the patient is not fully alert, complains of neck pain, has neurologic deficits, or has other painful injuries, cervical spine precautions should be maintained.
Vertebral injury can occur without cord damage because the spinal canal is widest in the cervical region. Neurologic deficits are present in 46% of patients and are more frequent with injuries involving C5–C7. A thorough neurologic examination should enable classification and identification of the level of the spinal cord lesion.
Autonomic instability may occur acutely and is termed spinal shock. With spinal shock, loss of sympathetic tone leads to generalized hemodynamic instability characterized by bradycardia, peripheral arterial and venous vasodilation, hypotension, and arrhythmia.
Respiratory compromise may occur acutely due to loss of intercostal muscle innervation or, with high cervical lesions, due to phrenic nerve loss. In normal individuals, expansion of the rib cage accounts for 60% of resting tidal volume. Therefore alveolar ventilation and the ability to cough are decreased with loss of intercostal muscle innervation, even if phrenic nerve function remains intact. Thus acute cervical cord injury may cause hypoxia, atelectasis, and respiratory failure. The possibility of aspiration pneumonitis may compound the situation. In addition, neurogenic pulmonary edema may be associated with SCI due to massive sympathetic discharge associated with trauma.
Vertebral artery injuries can occur with cervical spine injuries. If unrecognized or untreated, the incidence of mortality due to cerebrovascular ischemia is as high as 30%. The vertebral artery is most susceptible to injury at the point of entrance into the transverse foramen at C6. The second most common site is at C1–C2. Despite diagnosis and anticoagulation therapy, 5.8% become clinically symptomatic and 2.9% die due to cerebrovascular ischemia.
Radiographic Evaluation
The National Emergency X-radiography Use Study (NEXUS) Low Risk (NLR) criteria and the Canadian C-Spine Rule (CCR) were designed to identify patients who do not need diagnostic imaging to exclude a significant cervical spine injury. Cervical spine (CS) radiographs are indicated unless the patient meets the following five characteristics:
- 1.
Alert
- 2.
Not intoxicated
- 3.
No posterior cervical tenderness
- 4.
No neurologic changes
- 5.
No distracting injuries such as crush, burn, large lacerations, or significant fractures.
The CCR has a sensitivity of 99.4% (NLR 90.7%) in detecting injury and poses three questions:
- 1.
Does the patient have any high-risk injury (age >65, mechanism of injury is dangerous such as MVA, fall, bicycle accident)?
- 2.
Are there any low-risk factors present that would allow a safe assessment of range of motion to be obtained? Low-risk factors are simple rear-end collisions, ability to sit upright, ambulation, delayed onset of neck pain, or absence of cervical tenderness.
- 3.
Is the patient able to actively rotate neck 45 degrees to the right and the left?
If the patient has active rotation with low-risk factors and the absence of any high-risk factors, the physician can safely clear the cervical spine without radiographic imaging.
Plain radiography typically includes three views: anteroposterior, lateral, and odontoid. Plain radiography has been mostly replaced by computed tomography (CT) imaging because the false-negative rate is higher than that with CT. Emergency departments routinely rely on CT imaging to evaluate patients for injury. CT is best for detecting boney abnormalities. The most appropriate method for clearing the cervical spine in patients with altered mental status remains controversial. The Eastern Association for the Surgery of Trauma’s 2009 Practice Management Guidelines for Identification of Cervical Spine Injuries following Trauma notes that significant changes in practice have occurred since the first cervical spine injury guidelines were released in 1998. Now CT has replaced the three-view radiographic as the primary screening tool in the trauma patient who requires imaging. In the obtunded patient, flexion/extension dynamic bedside fluoroscopy adds no useful information, is inadequate, and may be dangerous. For the obtunded patient with a negative CT of the cervical spine, magnetic resonance imaging (MRI) may be obtained to further define ligamentous injury. If MRI is negative, immobilization of the CS can be discontinued. Controversy exists because the incidence of a ligamentous injury with a negative CT scan is very low. Hogan in 2005 studied 366 patients with a negative CT for CS injury. MRI imaging was also negative in 96.7%. Ligamentous injury was detected in 1.1% of these patients. Most often a spinal cord injury is associated with radiographic findings such as fractures, ligamentous injuries, or subluxations; however about 3.3% of adult patients with spinal cord injury without radiographic abnormality (SCIWORA) had spinal cord injury detected on MRI. So, at present, there is no definitive recommendation on the need for MRI after a negative CT of the CS. Additional MRI screening cares significant risk for the obtunded trauma patient and is expensive. Additionally, collar complications such as collar-related rash, skin breakdown, and pressure-related injuries; increase in intracranial pressure; higher incidence of ventilator days and intensive care length of stay; higher incidence of delirium; difficult central venous access; and delay in tracheostomy are possible when collars are left on for more than 72 hours. These issues need to be weighed against the small but potential possibility of a missed CS injury.
A diagnostic algorithm for the evaluation of a patient with possible cervical spine injury is shown in Fig. 27.2 .
