CT vs MRI C-Spine Imaging for C-Spine Clearance in Obtunded Patients in Low-Energy Trauma Mechanisms

Abstract

Background

Current guidelines from trauma societies recommend cervical spine (c-spine) clearance for obtunded blunt trauma patients after negative CT c-spine (CS-CT). However, the value of additional c-spine MRI (CS-MRI) in patients with low-energy trauma mechanisms is unclear and controversial. This study hypothesizes that obtunded blunt low-energy mechanism trauma patients would not have c-spine injuries requiring surgery on CS-MRI after negative CS-CT.

Methods

A retrospective review was conducted at a level 1 trauma center, analyzing adults with low-energy blunt trauma from 2018-2022. Inclusion criteria encompassed individuals over 18 years old admitted to the ICU following assault/fall 10 feet or less requiring intubation for 24+ hours. Exclusion criteria included patients with high-energy trauma or intubated later in their admission/less than 24 hours. Primary outcomes were c-spine injuries identified on MRI following negative CS-CT and percentage of patients requiring surgery. Statistical significance was set at 5%.

Results

Of 1462 charts, 300 patients met inclusion criteria. Of these 300 patients, 194 underwent only CS-CT (64.7%), while 106 underwent both CT and MRI (35.3%). Among the 82 patients with negative CS-CT who received CS-MRI, only 1 (1.2%) was found to have an unstable c-spine injury. Patients who underwent CS-MRI had increased ICU length of stay (7.52 vs 11.87 days) and ventilator days (6.12 vs 9.43 days) compared CS-CT alone.

Discussion

The findings suggest that negative CS-CT is typically sufficient for clearance in low-energy trauma patients. Additional CS-MRI may increase health care resource use without revealing significant injuries, supporting streamlined c-spine clearance protocols based on trauma mechanism.

Keywords

CT C-spine MRI C-spine spinal trauma spine injury trauma acute care

Key Takeaways

• Further cervical spine MRI after a negative cervical spine CT scan is associated with increased health care utilization costs while not providing additional clinical benefit.

• In obtunded blunt trauma patients with low-energy mechanisms, high-quality CT imaging for c-spine injuries is adequate, especially with a low suspicion of injury.

Introduction

Identification of cervical spine injuries in obtunded trauma patients is challenging due to the lack of a reliable neurological exam. This challenge is further complicated as missed cervical spine injuries and premature collar removal can lead to progressive deformity and irreversible neurological damage. In these instances, clearance of the cervical spine becomes dependent on advanced imaging rather than clinical examination. As a result, some advocate for both a negative screening cervical spine computed tomography (CS-CT) followed by a confirmatory negative cervical spine magnetic resonance imaging (CS-MRI) to allow for safe collar removal. However, this notion has been challenged as additional advanced imaging, such as CS-MRI can lead to prolonged cervical collar use, pressure ulcers, respiratory compromise, delirium, and increased cost.^1-8 Several systematic reviews suggest that the confirmatory CS-MRI provides little benefit and rarely identify unstable cervical spine injuries that were not previously seen on a negative CS-CT.^9-16 Recent practice guidelines echo these findings and advocate for prompt removal of the cervical collar in the obtunded blunt trauma patient with a negative CS-CT.¹⁷ Interestingly, after the Eastern Association of the Surgery of Trauma (EAST) released these guidelines, a recent study utilizing the National Trauma Data Bank (NTDB) showed that the incidence of screening CS-MRI in this population had increased without a clear explanation.¹⁸

There is a wide range of practice variations when clearing the cervical spine in obtunded patients even with these previously stated guidelines and study findings.¹⁹ This may be due, in part, to the broad definition of “blunt trauma” found in these studies. One could speculate that lower energy mechanisms, such as falls less than 10 feet or assault would not benefit from CS-MRI after a negative CS-CT, as the likelihood of an unstable ligamentous injury would be exceedingly rare. This relationship between mechanism energy and imaging accuracy has not been well defined in the cervical spine clearance literature. Therefore, the authors sought to investigate the rate of cervical spine injuries missed on the initial CS-CT but identified on CS-MRI in the obtunded blunt trauma patient with a low-energy mechanism (fall less than 10 feet, assault). At our institution, the decision to obtain a CS-MRI following a negative CS-CT was primarily influenced by individual physician preference rather than a standardized protocol. The aim of the study is to determine if additional CS-MRI imaging in patients with low-energy trauma mechanisms identified any further injuries requiring surgery that CS-CT did not identify. We hypothesize that obtunded blunt trauma patients who underwent a low-energy mechanism would not have additional c-spine injuries requiring surgery that were identified on screening CS-MRI after negative CS-CT.

Methods

A retrospective review at an American College of Surgeons-verified Level 1 trauma center of adults with low-energy blunt trauma from 2018-2022 was conducted. Inclusion criteria consisted of adults (≥18 years) admitted to the trauma ICU following an assault or a fall less than 10 feet who required intubation for more than 24 hours. Exclusion criteria included high-energy trauma mechanisms (MVC, MCC, or falls from height), patients under 18 years old, and those extubated within 24 hours or never intubated. Patients were considered obtunded if they required intubation for ≥24 hours due to altered mental status, inability to protect their airway, or clinical concern for cervical spine injury preventing an adequate neurological exam. Patients intubated for other indications, such as respiratory failure or procedural sedation, were excluded if they had no documented neurological impairment. Data collected included the mechanism of injury, primary diagnosis, Injury Severity Score (ISS), duration of mechanical ventilation, CS-CT and CS-MRI results (if applicable), time to CS-MRI from admission, need for c-spine surgery, and complications related to cervical collar use. The study was approved by the Institutional Review Board of the affiliated university and hospital, with a waiver of informed consent due to its retrospective nature (UMC-2022-457, 12/21/2022).

Outcomes

Primary outcomes included frequency of c-spine injuries identified on CS-MRI after negative CS-CT and the percentage of patients requiring surgery. Secondary outcomes included complications related to c-collar use, time to cervical spine clearance, ICU length of stay (ICU LOS), and ventilator days.

Statistical Analysis

First, univariate and bivariate tests were conducted to analyze the data. All assumptions, including normality and homogeneity of variance, were assessed. Categorical variables were represented as frequencies and proportions, whereas continuous variables were represented by mean and standard deviations. Groups were categorized as patients who underwent CS-CT only vs those having both CS-CT and CS-MRI. The mean differences in the continuous outcomes were calculated using independent-samples- t test/or Welch t test if homogeneity of variance was not assumed. Chi-square/Fisher exact test was used for comparing the nominal groups. The normal approximation to the binomial distribution method was used to calculate 95% confidence intervals of proportions in the univariate analyses. All analyses were conducted using the Statistical Package for Social Sciences for Windows (SPSS) version 28 (IBM Corp. Armonk, NY, USA). All analyses were conducted at α = 0.05. All P values were two-sided.

Results

Initially, 1462 patient charts were reviewed based on trauma ICU admission and blunt trauma mechanisms. After application of exclusion criteria, 300 patient charts met the final study criteria (see Figure 1).

Demographics

The characteristics of the study population utilized for data analysis, or patients that were intubated for at least 24 hours, are displayed in Table 1. Three-hundred patients were included in this study total, with 232 patients (77.3%) experiencing a fall of 10 feet or less and 68 patients (22.7%) with a mechanism of assault. Of the 300 total patients, 146 (48.7%) patients had an isolated TBI, 30 patients had isolated single system trauma without TBI, 97 patients had multisystem trauma with TBI, and 27 (9.0%) patients had multisystem trauma without a TBI.

Table 1.

Characteristics of the Initial Sample of Obtunded Blunt Trauma Patients (N = 300).

Variable	Categories	n (%)	95% CI (LCL, UCL)
Demographic characteristics
Age [M(SD)]	-	59.50 (17.83)	57.47, 61.53
Gender	Female	77 (25.7)	20.8, 31.0
Gender	Male	223 (74.3)	69.0, 79.2
Race	White	194 (64.7)	58.9, 70.1
	Black or African American	46 (15.3)	11.5, 19.9
	Asian	13 (4.3)	2.3, 7.3
	Other including American Indian, Native Hawaiian or Pacific Islander	47 (15.7)	11.7, 20.3
Ethnicity	Hispanic	39 (13.0)	9.4, 17.3
Ethnicity	Non-Hispanic	261 (87.0)	82.7, 90.6
Injury characteristics
Mechanism	Assault	68 (22.7)	18.0, 27.8
Mechanism	Fall of 10 feet or less	232 (77.3)	72.2, 81.6
ISS [M(SD)]	-	18.96 (8.95)	17.94, 19.97
Injury diagnosis	Isolated TBI	146 (48.7)	42.8, 54.5
	Isolated single system without TBI	30 (10.0)	6.8, 13.9
	Polytrauma with TBI	97 (32.3)	27.1, 37.9
	Polytrauma without TBI	27 (9.0)	6.0, 12.8

M = Mean; SD = Standard Deviation; CI = Confidence Interval; LCL = Lower Confidence Level; UCL = Upper Confidence Level.

Imaging

Of the 300 patients included, 194 (64.7%) underwent only CS-CT, while 106 (35.3%) underwent both CS-CT and CS-MRI (Figure 2). Among the 194 patients who had only CS-CT, 37 (19.1%) had a cervical spine injury identified. None of these patients had a missed or delayed diagnosis. Of the 106 patients who underwent both CS-CT and CS-MRI, 24 (22.6%) had a cervical spine injury identified. Six of these 24 patients had an injury visible on CS-CT and underwent subsequent CS-MRI for further characterization or surgical planning. The remaining 82 patients had a negative CS-CT, but 18 (17.0%) were subsequently found to have injuries on CS-MRI. These MRI-detected injuries included 15 cases of isolated ligamentous injury, 2 stable fractures without ligamentous disruption, and one unstable injury requiring surgery. Of the 15 patients with isolated ligamentous injuries, nine remained in a cervical collar at discharge, while six had their collars removed with documented clearance. The 2 patients with stable fractures were managed nonoperatively with a cervical collar, which was not cleared prior to discharge. One patient (1.2%) required cervical spine surgery during admission, while 81 (98.8%) did not require operative intervention (Table 2).

Table 2.

Reporting the MRI Results Among Those With the Negative CT Scan and Who Underwent MRI Scan (n = 82).

MRI Result	Frequency	Proportion
Ligamentous injury	15	18.3
No acute injuries	64	78.0
Stable C-spine injuries	2	2.4
Unstable C-spine injuries	1	1.2

Outcomes

Table 3 compares patients that received a CS-CT alone with patients that had a negative CS-CT that underwent further CS-MRI imaging. There was not a significant difference in complications related to c-collar use, cervical spine clearance, or need of c-spine operation between either of the groups. However, there was a significantly longer length of time to c-spine clearance after hospital admission in patients who received a CS-MRI in addition to a CS-CT vs a CS-CT alone (P=<0.001). In regard to health care resource utilization, patients that received a CS-MRI in addition to CS-CT had a significantly higher amount of ICU days (P < 0.001) and ventilator days (P < 0.001).

Table 3.

Comparison of Clinical Outcomes and Health Resource Utilization of CT Scan Only vs the Group With Negative CT Scan and Who Underwent MRI Scan (N = 276).

Variable	Group 1 (CS-CT Only)(n = 194)	Group 2 (Negative CS-CT + CS-MRI)(n = 82)	P Value
Clinical outcomes
Complications related to C-collar	2 (1.0)	0 (0.0)	0.36
Cervical clearance	154 (79.4)	67 (81.7)	0.66
Need for C-spine operation	4 (2.1)	1 (1.2)	0.63
Days to C-spine clearance
M(SD)	2.29 (2.91)	3.62 (3.13)	0.002
Health care resource utilization
ICU days M(SD)	7.52 (6.25)	11.87 (8.21)	<0.001
Ventilator days
M(SD)	6.12 (5.98)	9.43 (7.25)	<0.001

M = Mean; SD = Standard Deviation; P values less than 0.05 are considered statistically significant and are bolded in the table.

Discussion

High-quality CS-CT has the ability to discern unstable c-spine injuries and is reliable enough to forgo additional c-spine imaging if there is no further clinical suspicion for an injury. The obtunded blunt trauma patient provides a unique level of clinical challenge, as providers must rely on monitoring, imaging, and other adjunct studies to determine the severity of injury and do not have a clear clinical exam to assist in judgment. Therefore, the most reliable test for the clearance of the cervical spine, the clinical exam, can no longer be utilized.¹⁷ The notion that obtaining an MRI for cervical spine clearance may be extraneous when a high-quality CS-CT performed with negative findings is not new.^1,20 In addition, EAST and Western Trauma Association (WTA) have guidelines that affirm this practice.^17,21 Furthermore, previous research has indicated that there may be an associated increased health care utilization cost when performing these additional screening MRIs without added clinical benefit.¹⁵ Our study corroborates these findings, with an average increase of five additional days in the ICU and three additional days on the ventilator for patients undergoing further CS-MRI screening. While there are a multitude of variables that may cause these findings in the injured ICU patient, it is notable that these same patterns were found in our sample as well.

The most substantial concern of not performing a screening CS-MRI despite a negative CS-CT in this population is the incidence of a missed injury. A missed unstable cervical spine injury may lead to devastating neurologic dysfunction and even death in these patients. However, as a previous study has shown, the likelihood of a severe injury not being identified on high-quality CT imaging is extremely low.²² Our study supported this finding with patients involved in low-energy trauma mechanisms with potentially lower risk of a severe injury and found that 78% of patients undergoing CS-MRIs had no additional injuries. Of the identified missed injuries, only one required surgery for stabilization. This specific patient was unique in the study, as there was an initial report of possible neurologic injury by EMS on arrival to the trauma bay, but a detailed neurologic assessment could not be performed due to early intubation secondary to respiratory compromise. Therefore, this patient still met our inclusion criteria and despite negative CS-CT findings, he underwent CS-MRI imaging because of this suspicion and was identified to have an unstable injury requiring surgery. This finding promotes the recommendation from EAST in which if there is clinical suspicion of injury, further work-up and imaging should be performed.¹⁷

Future studies should analyze patients that have been involved with high-energy trauma mechanisms, such as high-speed motor vehicle or motorcycle collisions, and automobile vs pedestrians, to determine if there are higher rates of clinically significant missed injuries identified on CS-MRIs. With this, further recommendations may be developed to limit the number of CS-MRIs based on trauma mechanisms and promote a decrease of unnecessary medical imaging.

There are several limitations to this study. First, it was conducted as a retrospective chart review and is subject to the known biases already established. Due to this, our ability to establish any cause-effect relationships will be limited. Second, although our study covers 4 years of trauma admissions, the sample size remains relatively small—with 300 patients meeting inclusion criteria and 82 patients undergoing CS-MRI after negative CS-CT findings. Given the single-institution nature of the study and the unique case mix of patients, the generalizability of our findings may be limited. Additionally, the small subgroup size raises the possibility of over- or under-sampling, especially given that 18.3% of these patients demonstrated ligamentous injury on MRI. Furthermore, with 77.3% of study patients experiencing a fall of less than 10 feet as their injury etiology, there may be a lack of generalizability to the broader low-energy trauma population. Another notable limitation is the reliance on descriptive statistical analyses, such as t-tests and chi-square comparisons, to evaluate differences between patients who had CT alone vs those that underwent CT and MRI. Patients who had an MRI done may systematically differ based on age, comorbidities, ISS, or clinical suspicion, which may introduce selection bias. Future research incorporating risk-adjusted analyses could better consider these potential confounders and strengthen validity of the findings.

Additionally, while our study concluded that routine CS-MRI after a negative CS-CT may not provide significant additional clinical benefit, the relatively high proportion (18.3%) of ligamentous injuries identified on MRI warrants further discussion. Although these injuries were managed conservatively, ligamentous injuries without associated fracture still carry risk for long-term morbidity. The lack of follow-up data of the ligamentous and stable c-spine injuries in our study limits our ability to assess the clinical outcomes of these patients, including potential complications or the necessity of prolonged immobilization. Future studies should examine the long-term impact of these injuries to better determine the clinical significance of MRI-detected ligamentous injuries. Finally, our study identified one patient out of 82 with an unstable fracture requiring surgery, raising the question of whether MRI should still be considered in select cases. While the incidence was low, the consequences of missing an unstable injury are indeed significant. Cost is an integral factor in medical decision-making. However, patient and family input regarding the trade-offs between cost and potential clinical benefit should be incorporated into imaging strategy discussions as well. In conclusion, while our findings suggest that CS-MRI after a negative CS-CT for c-spine injuries in low-energy blunt trauma patients is associated with increased health care utilization costs while not providing significant clinical benefit, additional research is required to refine patient selection criteria for CS-MRI and further evaluate long-term clinical outcomes.

Footnotes

Acknowledgments

The authors would like to thank the University Medical Center Trauma Registrars for their contribution to this work: Lisa Rogge, Trauma Program Manager; Robert McClaren, Lead Registrar; Dina Bailey, Mary Henson, and Daniel Wood.

Author Contributions

R.R.—literature search, study design, data collection, data interpretation, writing, and critical revisions. J.D.—data collection, data interpretation, critical revisions. J.M.—literature search, data collection, writing, critical revisions. H.K.—data collection, writing, critical revisions. K.B. - study design, data interpretation, writing, critical revisions. S.M.—study design, data interpretation, and critical revisions. D.R.F.—study design, data interpretation, and critical revisions. A.G.M.—literature search, study design, data collection, data interpretation, critical revisions.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Ethical Statement

ORCID iDs

Henry Krasner

Allison G. McNickle

Data Availability Statement

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.*

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