Imaging of the Spine in Victims of Trauma 17

17

Imaging of the Spine in Victims of Trauma

C. Craig Blackmore and Gregory David Avey

Issues of Imaging of the Cervical Spine

I. Who should undergo cervical spine imaging?

A. NEXUS prediction rule

B. Canadian cervical spine prediction rule C. Applicability to children

II. What cervical spine imaging is appropriate in high-risk patients?

A. Cost-effectiveness analysis

III. Special case: defining patients at high fracture risk A. Applicability to children

IV. Special case: the unconscious patient

Issues of Imaging of the Thoracolumbar Spine

V. Who should undergo thoracolumbar spine imaging?

A. Applicability to children

VI. Which thoracolumbar imaging is appropriate in blunt trauma patients?

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Cervical spine imaging is not necessary in subjects with all five of the following: (1) absence of posterior midline tenderness, (2) absence of focal neurologic deficit, (3) normal level of alertness, (4) no evidence of intoxication, and (5) absence of painful distracting injury (strong evidence).

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Computed tomography (CT) scan of the cervical spine is cost- effective as the initial imaging strategy in patients at high probability of fracture (neurologic deficit, head injury, high energy mechanism) who are already to undergo head CT (moderate evidence).

Issues

Key Points

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No adequate data exist on the appropriate cervical spine evaluation in subjects who cannot be examined due to a head injury (insufficient evidence).

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Imaging of the thoracolumbar spine is not necessary in blunt trauma patients with all five of the following: (1) absence of thoracolumbar back pain, (2) absence of thoracolumbar spine tenderness on midline palpation, (3) normal level of alertness, (4) absence of distracting injury, and (5) no evidence of intoxication (moderate evidence).

Definition and Pathophysiology

The majority of spine fractures occur from high-energy trauma such as high-speed motor vehicle accidents and falls from heights (1,2). However, an important minority occur from relatively low-energy mechanisms such as falls from a standing height or low-velocity automobile accidents (3,4).

Epidemiology

Cervical spine fractures occur in approximately 10,000 individuals per year in the United States, most the result of blunt trauma (5,6). Among patients with a fracture, approximately one third will sustain severe neurologic injury (6,7). Unfortunately, fractures of the cervical spine may not be clinically obvious. Patients may be neurologically intact initially, but if not treated appropriately and promptly, progress to severe neurologic compromise (8). Delayed onset of paralysis occurs in up to 15% of missed fractures, and death due to unidentified cervical spine fracture is possible (9,10). Furthermore, the mechanism of injury is also not always useful for excluding cervical spine fracture.

Thoracolumbar spine injury has been estimated to occur in between 2%

and 4% of all blunt trauma patients (11,12). These injuries were judged to require treatment in approximately three fourths of those identified (13).

Much like cervical spine fractures, a resulting neurologic deficit is noted in approximately one third of those with thoracolumbar injury (14,15). Given the potentially serious consequences of these injuries, it is unsettling to find that studies have noted a significant delay in diagnosis in 11% to 22% of patients with spine fractures (9,16,17).

Overall Cost to Society

There is enormous variability in the practice of cervical spine imaging

(18,19), but in most centers, imaging is used liberally. As a result, the yield

from cervical spine imaging is low, with only 0.9% to 2.8% of such imaging

studies demonstrating injury (20,21). Overall, the total cost of the imaging,

evaluation, and care of patients with cervical spine trauma in the United

States is an estimated $3.4 billion per year (22). The yield of thoracolum-

bar imaging is somewhat higher than cervical spine imaging, with posi-

tive studies accounting for 7.6% to 9% of blunt trauma thoracolumbar

exams (23). The total societal cost of thoracolumbar spine injury has been

estimated at $1 billion per year (24).

Goals

The overall goal of initial spine imaging is to detect potentially unstable fractures to enable immobilization or stabilization and prevent develop- ment or progression of neurologic injury. Additional imaging studies may be performed to inform prognosis and guide surgical intervention for unstable injuries.

Methodology

A Medline search was performed using PubMed (National Library of Medicine, Bethesda, Maryland) for original research publications dis- cussing the diagnostic performance and effectiveness of imaging strategies in the cervical and thoracolumbar spine. Clinical predictors of cervical and thoracolumbar spine fracture were also included in the literature search.

The search for cervical spine–related publications covered the period 1966 to March 2002. The search strategy employed different combinations of the following terms: (1) cervical spine, (2) radiography or imaging or computed tomography, and (3) fracture or injury. The search for thoracolumbar spine–

related publications covered the period 1980 to March 2004. The search strategy included the MESH headings (1) spine and diagnosis, and (2) imaging and trauma. Additional articles were identified by reviewing the reference lists of relevant papers. This review was limited to human studies and the English-language literature. The authors performed an initial review of the titles and abstracts of the identified articles followed by review of the full text in articles that were relevant.

I. Who Should Undergo Cervical Spine Imaging?

Summary of Evidence: Determination of which blunt trauma subjects should undergo cervical spine imaging, and which should not undergo imaging, is a question that has been studied in detail in literally tens of thousands of subjects. The two major level I (strong evidence) studies, the NEXUS trial (Table 17.1), and the Canadian C-spine rule (Table 17.2) were comprehensive multicenter investigations of this topic. The NEXUS rule (Table 17.1) has undergone extensive validation and demonstrates high sensitivity for detec- tion of fractures. The Canadian C-spine rule (Table 17-2) also has high sensitivity, and potentially higher specificity than the NEXUS. However, neither of these rules has been tested in an implementation trial to deter- mine their impact outside the research setting.

Table 17.1. NEXUS criteria: imaging of the cervi- cal spine is not necessary if all five of the NEXUS criteria are met

1. Absence of posterior midline tenderness 2. Absence of focal neurologic deficit 3. Normal level of alertness

4. No evidence of intoxication

5. Absence of painful distracting injury

Source: Adapted from Hoffman et al. (29).

Supporting Evidence: The low yield of cervical imaging has prompted a number of investigators to attempt to identify clinical factors that can be used to predict cervical spine fracture. Early studies of this question were largely level III (limited evidence) investigations consisting of unselected case series. For example, in 1988, Roberge and colleagues (25) studied 467 consecutive subjects who underwent cervical spine radiography and found that subjects with cervical discomfort or tenderness were more likely to have a fracture than those without such symptoms or signs. Additional investigators identified associations between cervical spine fracture and mechanism of injury (26,27), level of consciousness (20,21,27), and intoxi- cation (20,28). However, all of these investigations involved small numbers of subjects with fracture and a single or small number of centers.

A. NEXUS Prediction Rule

The first major cohort investigation of clinical indicators for cervical spine imaging was the National Emergency X-Radiography Utilization Study (NEXUS) (5,29). This was a large Level I study performed at 23 different emergency departments across the United States. The goal of the NEXUS study was to assess the validity of four predetermined clinical criteria for cervical spine injury (Table 17.1). These criteria were (1) altered neurologic function, (2) intoxication, (3) midline posterior bony cervical spine tender- ness, and (4) distracting injury. The NEXUS investigators prospectively enrolled over 34,000 patients who underwent radiography of the cervical spine following blunt trauma. Of these, 818 (2.4%) had cervical spine injury. These authors found that the clinical predictors had a sensitivity of 99.6% for clinically significant injury (Table 17.3) (5,29). The authors also reported high interobserver agreement ( k = 0.73) for the prediction rule (30), and reported that use of the rule would have decreased the overall ordering of cervical radiography by an estimated 12.6% (29).

Table 17.2. The Canadian C-spine rule

If the following three determinations are made, then imaging is not indicated 1. No high-risk factor, including:

Age >64 years

Dangerous mechanism, including:

Fall from >3 m/5 stairs Axial load to head (diving)

High-speed motor vehicle accident (60 mph, rollover, ejection) Bicycle collision

Motorized recreational vehicle Paresthesias in extremities 2. Low-risk factor is present

Simple rear-end vehicular crash, excluding:

Pushed into oncoming traffic Hit by bus/large truck Rollover

Hit by high-speed vehicle

Sitting position in emergency department Ambulatory at any time

Delayed onset of neck pain

Absence of midline cervical tenderness

3. Able to actively rotate neck (45 degrees left and right)

Source: Adapted from Dickinson et al. (33).

B. Canadian Cervical Spine Prediction Rule

A second level I clinical prediction rule, the Canadian C-spine rule for radi- ography (25) was published subsequent to the NEXUS trial, but with a similar objective: to derive a clinical decision rule that is highly sensitive for detecting acute cervical spine injury. The Canadian C-spine rule was a prospective cohort study of 8924 subjects from 10 community and univer- sity hospitals in Canada. Excluded were patients who had neurologic impairment, decreased mental status, or penetrating trauma. Like the NEXUS study, the Canadian C-Spine Study was an observational study performed without informed patient consent. However, patients who were eligible for the study but did not undergo radiography were followed up with a structured telephone interview 14 days following their discharge from the emergency department (ED). Thus, any patients who had not undergone radiography, and who had missed fracture would potentially be discovered during the investigation. The Canadian study investigated the predictive ability of 20 factors, and based on the reliability and pre- dictive properties of these factors, developed a prediction rule consisting of three questions. According to the Canadian C-spine rule (Table 17.2), the probability of cervical spine injury is extremely low, and imaging is not indicated if the following three determinations are made: (1) absence of high-risk factor (age >65 years, dangerous mechanism, paresthesias in extremities); (2) presence of a low-risk factor (simple rear-end motor vehicle collision, sitting position in ED, ambulatory at any time since injury, delayed onset of neck pain, or absence of midline cervical C-spine tender- ness); or (3) patient is able to actively rotate neck 45 degrees to left and right. The Canadian study group reported sensitivity of 100% and speci- ficity of 42.5% for this clinical prediction rule and also reported that the rate of ordering radiography would be 58.2% of the current rate (Table 17.3) (31).

The Canadian C-spine rule was validated using a prospective cohort study of 8283 patients presenting at the same 10 Canadian community and academic hospitals as the original study (32). The results of this verifica- tion trial noted a sensitivity of 99.4% and a specificity of 45.1%, very similar

Table 17.3. Diagnostic performance

Potential decrease Test (reference) Sensitivity Specificity in radiography C-spine prediction rules

NEXUS (29) 99.6 12.9 12.6

Canadian C-spine rule (31) 100 42.5 41.8

TL-spine prediction rules

Holmes et al. (11) 100 3.9 3.7

C-spine imaging

Radiography (43,45) Overall 93.9 95.3 N/A

Low risk 96.4 N/A

High risk 78.1–89.3 N/A

CT (39,41,42,46)

Overall

TL-spine imaging 99.0 93.1 N/A

Radiography (60,64)

63.0 94.6 N/A

CT (60–64) 97.8 99.6 N/A

1

Pooled from these references.

N/A, not applicable.

to the results of the derivation study. It was noted during the course of this study that physicians failed to evaluate neck range of motion, as required by the Canadian C-spine rule, in 10.2% of patients. While virtually all of this group of incompletely evaluated patients underwent cervical spine imaging (98.8%), this group was found to have a lower rate of injury (0.8%) than the cohort as a whole (2.0%).

The data supporting the adoption of one cervical spine prediction rule over the other is limited. Two studies, the validation study for the Canadian C-spine rule and a retrospective analysis of the Canadian C-spine derivation cohort have attempted to compare the NEXUS and Canadian rules (32,33). However, both cohorts excluded those with altered levels of consciousness, effectively eliminating one of the NEXUS criteria. In addi- tion, others have voiced concerns regarding physician familiarity with the various rules, side-by-side comparison, and the definitions of the NEXUS criteria used in these trials (34,35). The choice of clinical prediction rule in a broader clinical context is also unclear, as no trial has examined the impact of implementing these prediction rules outside of the research setting.

C. Applicability to Children

Evidence for who should undergo imaging is less complete in children than in adults. Determination of clinical predictors of injury in pediatric patients is complicated by the decreased incidence of injury in children, requiring a larger sample size for adequate study (36,37). In addition, chil- dren may sustain serious cervical cord injuries that are not radiographi- cally apparent (37,38). Among the level I studies, the Canadian clinical prediction rule development study excluded children (31). The NEXUS trial included children, but there were only 30 injuries in patients under age 18, and only four in patients under age 9 (36). Although no pediatric injuries were missed in the NEXUS study, sample size was too small to adequately assess the sensitivity of the prediction rule in this group.

Therefore, no adequate evidence exists regarding appropriate criteria for imaging in children.

II. What Cervical Spine Imaging Is Appropriate in High-Risk Patients?

Summary of Evidence: Cervical spine CT is more sensitive than radiogra- phy, and more specific in patients at high risk of fracture. But CT has higher direct costs than radiography. However, cost-effectiveness analysis demon- strates that CT is cost-effective, and may actually be cost-saving from the societal perspective in patients at high probability of fracture. Cost savings with CT are from a decreased number of second imaging examinations resulting from inadequate radiograph studies, and to the high cost in dollars and health for the rare fracture missed from radiography that leads to severe neurologic deficit. Radiography remains the most cost-effective imaging option in patients at low probability of injury (Fig 17.1).

Supporting Evidence: There are multiple investigations of radiography

accuracy, although most are retrospective, level III (limited evidence)

studies (39,40). Further, sensitivity of radiography is dependent on the

selected reference standard. Studies incorporating CT as the reference

standard suggest that radiography misses 23% to 57% of fractures (41,42).

However, the clinical relevance of these missed fractures is uncertain.

Studies using fractures that become apparent clinically as the reference standard are probably more relevant for clinical practice. No formal meta- analyses of radiograph accuracy exist. However, weighted pooling of the larger studies using a clinical gold standard suggests that radiography is relatively accurate, with a sensitivity of approximately 94% and a speci- ficity of approximately 95% when all trauma patients are considered (Table 17.3) (43).

Cervical radiography has substantial limitations in patients at the highest probability of fracture. Patients involved in high-energy trauma are commonly on backboards, have other injuries, and may be uncooperative.

Cervical radiography in this group has been found to be more difficult to perform adequately, resulting in lower specificity, and requiring longer time, more repeat radiographs, and higher costs (44,45). Radiograph speci- ficity ranges from approximately 96% in patients with only minor noncer- vical injuries, to 89% in patients with head injury, to 78% in patients with head injury and a high-energy mechanism such as motorcycle crash (45).

Radiographs are relatively inexpensive, with direct, short-term resource ranging from $34 to $60 (44).

More recently, CT has been proposed as an initial cervical spine evalua- tion modality in patients who are victims of major trauma. Nuñez and col- leagues studied the use of CT in the initial evaluation of trauma patients and demonstrated high sensitivity for fracture (99%) in a large, level II prospective series (moderate evidence) (42). This has been subsequently confirmed by other studies (46,47). Also, CT demonstrated high specificity (93%), even in patients at high-risk of fracture (Table 17.3) (46).

Figure 17.1. Evidence-based decision tree for imaging of the cervical spine in victims of trauma. The NEXUS or Canadian prediction rules are used to select patients for imaging. If imaging is appropriate, the Harborview prediction rule is used to select patients for CT rather than radiography. However, cervical spine CT is only used as the initial imaging strategy in patients who are to undergo head CT.

Patients who are not to undergo head CT are imaged with radiography.

Direct, short-term resource costs of cervical spine CT likely exceed those of radiography, but no comprehensive cost analyses of CT have been pub- lished. Assessment of cost of cervical spine CT is difficult as many institu- tions obtain economies of scale by performing CT of the cervical spine in the same setting as CT of the head (43,47). However, CT may be faster than radiography, and Nuñez and colleagues (42) have suggested that use of CT may decrease patient time in the emergency department. Therefore, CT has higher sensitivity and specificity for cervical spine fracture in high-risk patients, but at potentially higher cost.

The appropriateness of CT as initial cervical spine imaging strategy in patients who are also undergoing head CT has been examined with cost- effectiveness analysis (43). This analysis, taken from the societal perspec- tive, was based on a decision-analysis model, and compared the cost effectiveness of radiography and CT for patients at different probabilities of cervical spine fracture. The cervical spine cost-effectiveness model, taken from the societal perspective, was dependent on radiograph sensitivity, radiograph specificity, CT sensitivity, CT specificity, probability of fracture, and the probability of paralysis or the likelihood that a patient will become paralyzed if a fracture was missed by cervical imaging. In addition, the cost-effectiveness model was dependent on the short-term resource cost of radiography and CT, as well as the cost of the imaging that was induced by the initial strategy, and the cost of any neurologic deficit (paralysis) that developed from missed fracture. Costs were estimated from Medicare reimbursement data, and literature estimates, and the analysis was limited to adults (43).

A. Cost-Effectiveness Analysis

Cost-effectiveness analysis revealed that in patients at high risk ( >10%) of cervical spine fracture, CT was actually a dominant strategy, both saving money and improving health through the prevention of paralysis. The cost savings associated with the use of CT was due to fewer inadequate exams, and to the very high medical and financial cost of the rare case of paraly- sis. The probability of a patient developing paralysis from missed fracture was actually extremely low, as fractures were uncommon, and the sensi- tivity of imaging was very high. However, the lifetime medical costs of a patient who became paralyzed were high, with estimates ranging from

$525,000 to $950,000 (1995 dollars), and not including societal costs such as lost wages. In addition to the cost, there were obvious health consequences of paralysis. The dominance of CT over radiography in these high-proba- bility patients was robust to sensitivity analysis testing of the uncertainty in the estimates. In patients at moderate probability of fracture (4–10%), CT cost more overall than radiography, but with a cost-effectiveness ratio on the order of $25,000 per quality-adjusted life year. In patients at low probability of cervical spine fracture ( <4%) CT was clearly not cost-effective, and radiography was the preferred strategy (43).

III. Special Case: Defining Patients at High Fracture Risk

Summary of Evidence: Selection of patients for cost-effective use of cervical

spine CT is dependent on probability of fracture. The Harborview high-

risk cervical spine criteria have been developed and validated by a single

institution level II (moderate evidence) study. Using these criteria, patients can be identified with injury probabilities ranging from 0.2% to 12.8%.

Supporting Evidence: Patients at risk for cervical spine fracture are a het- erogeneous group. Some patients have sustained major trauma and will be at high probability of injury, while others will have sustained only minor trauma and will be at low probability of having sustained cervical spine fracture. Given that cost-effectiveness of imaging is dependent on the prob- ability of cervical spine fracture, optimization of imaging in the cervical spine requires stratification of patients into different levels of probability of fracture. This stratification must be based on clinical findings that are apparent when patients are first evaluated in the ED, prior to any imaging.

To identify patients at high probability of fracture, Blackmore and col- leagues (48) developed and validated a clinical prediction rule. This level II study employed a case-control study design, in which 160 patients were evaluated at Harborview Medical Center in the years 1994 to 1995 who had cervical spine fracture. Controls were 304 randomly selected adult blunt trauma patients from the same institution. The authors used logistic regres- sion and recursive partitioning to develop a clinical prediction rule, which was then validated internally using the bootstrap technique. Using likeli- hood ratios from the clinical prediction rule and the known base preva- lence of cervical spine fracture in the institution’s population, the authors developed a series of fracture probability estimates for patients of differ- ent clinical circumstances (48). Although derived retrospectively, this pre- diction rule was subsequently prospectively validated on a separate patient group at the same institution (Table 17.4) (49). To date, this predic- tion rule has not been validated at other institutions. A clinical prediction rule has also been developed (but not validated) to evaluate predictors of cervical spine fracture in the elderly. The elderly prediction rule was iden- tical to that in all adults, except that a higher proportion of injured patients were missed by the prediction rule criteria (50).

A. Applicability to Children

Comparison of CT versus radiography has not been well explored in children. The cost-effectiveness analysis of Blackmore and colleagues (43) excluded children, as did the studies of the Harborview high-risk cervical spine criteria (48,49). Further, the lower frequency of injury in children Table 17.4. Harborview high-risk cervical spine criteria

Presence of any of the following criteria indicates a patient at sufficiently high- risk to warrant initial use of CT to evaluate the cervical spine

1. High-energy injury mechanism

High-speed (>35 mph) motor vehicle or motorcycle accident Motor vehicle accident with death at scene

Fall from height greater than 10 feet 2. High-risk clinical parameter

Significant head injury, including intracranial hemorrhage or unconscious in emergency department

Neurologic signs or symptoms referable to the cervical spine Pelvic or multiple extremity fractures

Source: Adapted from Hanson et al. (49).

(36,37) and the increased radiosensitivity of pediatric patients (51) suggest that cost-effectiveness results from adults may not be relevant.

IV. Special Case: The Unconscious Patient

Summary of Evidence: The theoretical risk of radiographically occult un- stable ligamentous injury in patients who are unexaminable due to head injury has led to a variety of imaging approaches. There is insufficient evi- dence to support any particular approach.

Supporting Evidence: Standard radiologic and CT examinations of the cervical spine allow assessment of bony alignment. However, anecdotal reports exist in the literature describing unstable ligamentous injuries without malalignment on imaging (52,53). Accordingly, organizations including the Eastern Association for the Surgery of Trauma recommend additional imaging of the neck soft tissues to exclude unstable ligamen- tous injury. Proposed imaging approaches include magnetic resonance imaging (MRI), flexion and extension radiography, and fluoroscopy.

To date, there have been no reported level I or level II studies of the accuracy or clinical utility of any of the proposed imaging algorithms.

Case-series data suggest that approximately 2% of obtunded patients may have unstable cervical spine injuries not detectable on initial CT or radiography (52,54,55). The clinical significance of these injuries has not been established.

V. Who Should Undergo Thoracolumbar Spine Imaging?

Summary of Evidence: Clinical prediction rules to determine which patients should undergo thoracolumbar spine imaging have been developed but not validated. Although these prediction rules have high sensitivities for detecting thoracolumbar fractures, their low specificities and low positive predictive values would require imaging a large number of patients without thoracolumbar injuries. This drawback limits the clinical utility of these prediction rules (moderate evidence).

Supporting Evidence: Given the relative lack of clarity regarding which blunt trauma patients require thoracolumbar imaging, several level III (limited evidence) studies have examined potential risks for thoracolum- bar fracture. These limited studies have identified associations among the risk of thoracolumbar injury and high-speed motor vehicle accident (53,54), fall from a significant height (13,56,57), complaint of back pain (12–14,56,58), elevated injury score (13,56), decreased level of conscious- ness (14,56–58), and abnormal neurologic exam (14,57).

Two separate clinical predication rules to guide thoracolumbar spine

imaging decisions have been validated. The smaller study, conducted by

Hsu et al. (59), examined the effect of six clinical criteria on two retro-

spective groups (59). The first group consisted of a cohort of 100 patients

with known thoracolumbar fracture, while the second group consisted of

100 randomly selected multitrauma patients. The criteria evaluated were

(1) back pain/midline tenderness, (2) local signs of injury, (3) neurologic deficit, (4) cervical spine fracture, (5) distracting injury, and (6) intoxica- tion. The results of this small-scale, retrospective trial found that 100% of the patients in the known thoracolumbar fracture group would have been imaged appropriately using the proposed criteria. This proposed pathway was then tested retrospectively in the group of randomly selected blunt trauma patients, and was found to have a sensitivity of 100%, a specificity of 11.3%, and a negative predictive value of 100%. Implementing these cri- teria would still require imaging the thoracolumbar spine in 92% of the selected multitrauma patients.

A much larger prospective, single center study by Holmes et al. (11) eval- uated similar criteria in 2404 consecutive blunt trauma patients who under- went thoracolumbar imaging (moderate evidence). These clinical criteria were (1) complaints of thoracolumbar spine pain, (2) thoracolumbar spine pain on midline palpation, (3) decreased level of consciousness, (4) abnor- mal peripheral nerve examination, (5) distracting injury, and (6) intoxica- tion (Table 17.5). This prediction rule was successful in achieving 100%

sensitivity for detecting thoracolumbar fracture; however, the specificity was only 3.9%. Due to this low specificity, implementing this prediction rule in this patient population would have decreased the rate of thora- columbar imaging by merely 4%.

A. Applicability to Children

It is unknown if these clinical prediction rules may be applied to children.

The largest study by Holmes et al. (11) did allow the enrollment of chil- dren; however, they do not report the actual number of children enrolled.

The youngest patient enrolled in the small trial by Hsu et al. (59) was 14 years.

VI. Which Thoracolumbar Imaging Is Appropriate in Blunt Trauma Patients?

Summary of Evidence: Multiple studies have shown that some CT proto- cols used for imaging the chest and abdominal visceral organs are more sensitive and specific for detecting thoracolumbar spine fracture than con- ventional radiography. In patients undergoing such scans, conventional radiography may be eliminated (limited evidence). The effect of primary screening with CT scan on cost and radiation exposure has not been thor- oughly studied for the thoracolumbar spine.

Table 17.5. Thoracolumbar spine imaging criteria 1. Thoracolumbar spine pain

2. Thoracolumbar spine tenderness on midline palpation 3. Decreased level of consciousness

4. Abnormal peripheral nerve examination 5. Distracting injury

6. Intoxication

Supporting Evidence: Multiple level III (limited evidence) studies examine the possibility of eliminating conventional radiography in those patients who are candidates for both conventional thoracolumbar radiographs and CT evaluation of the chest or abdominal viscera; however, many of these trials are hampered by small sample sizes or verification bias (60–64).

Studies that combine the results of both CT and conventional radiography as the reference standard suggest that CT has a sensitivity of 78.1% to 97%, while conventional radiographs have a sensitivity of 32.0% to 74% for detecting thoracolumbar fracture (61–63). The clinical importance of thoracolumbar fractures not found with conventional radiography is unknown, as no studies with clinically based outcome measures were located.

A single level III (limited evidence) trial examined the use of CT as an initial evaluation in patients for whom a CT scan is not indicated for other reasons (62). This prospective, single center trial examined 222 trauma patients with both CT and conventional radiographs as initial screening exams. The reported sensitivity was 97% for CT examination and 58% for conventional radiographs. The results of this trial are limited in that only 36 patients were diagnosed with thoracolumbar fracture during the course of the trial.

Future Research

• Studies in both cervical spine and thoracolumbar spine imaging indicate that CT is more sensitive than traditional radiography in detecting frac- tures. However, the clinical relevance of these fractures is uncertain.

• The applicability of spine injury clinical prediction rules in pediatric patients is unknown. In addition, the sensitivity, specificity, and cost- effectiveness of the various imaging exams in the pediatric population are not well established.

• Clinical prediction rules for imaging of the thoracolumbar spine have been developed, but further research is necessary to validate such approaches. The effect of implementing these rules on cost, cost- effectiveness, and radiation exposure has not been determined.

• Appropriate imaging to detect unstable ligamentous injury, particularly in clinically unexaminable patients remains unresolved.

Take-Home Table and Figure Suggested Imaging Protocols

• Cervical spine radiography: anteroposterior, open mouth, lateral, swimmer’s lateral (optional: 45-degree oblique views with 10-degree cephalad tube angulation).

• Cervical spine CT (multidetector): C0 to T4, detector collimation 1.25 mm.

Sagittal reformations: 3-mm intervals, right neuroforamen to left neuro- foramen. Coronal reformations: 3-mm intervals, front of vertebral body through spinal canal, C0 to C5 only.

• Thoracolumbar spine radiography: anteroposterior and interval.

Swimmer’s lateral of cervirothoracic junction if no CT cervical spine.

• Thoracolumbar spine CT (reconstructions from trauma abdomen pelvis CT). Axial images at 2.5 mm slice interval and sagittal reformations at 2.5 mm intervals.

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