Safety and Utility of Functional Dynamic Cervical Spine Radiographs in Select Subaxial Cervical Injury With Incomplete or No Neurological Deficit: Hybrid Retrospective and Prospective Observational Study

Abstract

Study Design

Hybrid retrospective and prospective observational study.

Objectives

To evaluate the safety and clinical utility of Functional Dynamic Cervical Spine Radiographs (FDCSR) under supervision in assessing instability of subaxial cervical spine in non-obtunded cervical spine trauma patients with incomplete or no neurological deficits.

Methods

We reviewed records and radiographs of patients with traumatic cervical spine injury from January 2014 to December 2017 (retrospectively) and January 2018 to December 2018 (prospectively). Inclusion criteria: (1) Patients with intact neurology and stable injuries on static radiographs (<11° angulation, <3.5 mm translation) who underwent FDCSR; (2) Patients with neurological deficits and degenerative/congenital canal stenosis without discernible injuries on static radiographs, suggestive of hyperextension injuries. Outcomes assessed included X-ray adequacy, pre- and post-procedure neurological status, pain/spasm during imaging, and evidence of instability.

Results

Of 6890 patients evaluated, 364 met inclusion criteria (258 retrospective, 86 prospective). Pre-FDCSR neurological status was AIS-B (1.1%), AIS-C (8%), AIS-D (12.6%), and normal (78.3%). No neurological deterioration occurred post-FDCSR. X-rays were adequate in 202 cases (55.5%) and inadequate in 162. Instability was detected in 4.95% of adequate (n = 10) and 11.7% of inadequate (n = 19) FDCSR studies, with an overall instability rate of 7.97% (n = 29).

Conclusions

FDCSR, when performed under appropriate supervision, is a safe and effective adjunct for detecting cervical spine instability in select trauma patients. It can identify occult instability even in suboptimal studies, supporting its utility in the evaluation of patients with equivocal findings on static imaging.

Keywords

cervical spine cervical spine trauma cervical spine instability X-ray

Introduction

Cervical spinal cord injury is believed to be a devastating event with substantial psychosocial and socioeconomic impact on the patient and caregivers. It has been reported to have a varied incidence ranging from 3.62% to 50% in the setting of a cervical spine fracture.^1-10 Primary injury to the cord occurs at the time of trauma due to mechanical damage whereas secondary injury occurs due to vascular and biochemical effects.¹¹ Persistent compression and vertebral column instability have been described to cause secondary spinal cord injury.^11-13 A prompt detection of these injuries and timely immobilization is essential to prevent additional injury to the spinal cord. The incidence of delayed diagnosis in cervical injuries ranges from 5% to 20% in the literature.^14-16

Radiologic misinterpretation, incomplete sets of radiographs or inadequate radiographs were described as common reasons for delayed or missed diagnosis. Disco-ligamentous injuries could be missed even on a three view X-ray series as well as on a computed tomography (CT) scan. FDCSR could be helpful to identify the injury in such cases.¹⁷ However, the diagnostic value of FDCSR following normal CT scan findings has been questioned in a few previous studies.^18-20 Though imaging techniques such as MRI can identify disco-ligamentous injuries, it is limited by the unavailability and cost issues, particularly in the developing countries. Also, MRI has been observed to have a high false positive rate.²¹ All of the previous studies have been performed in cases where a fracture could not be recognized on a radiograph or CT scan. The current subaxial cervical spine classification systems that are commonly employed are mechanistic classifications, which are useful for categorizing the injury patterns but do not reliably predict stability and management.²² Post-traumatic cervical spine instability can lead to persistent pain, long-term disability, and an increased risk of delayed spinal cord injury. CT and MRI, while essential, offer a static assessment. However FDCSR can reveal occult instability that may not be apparent on static imaging-thus providing a more functional insight into spinal behaviour under physiological conditions.

At our centre, we routinely perform FDCSR in Subaxial Cervical Injury (SACI) even in cases with a fracture detectable on X-ray/CT scan to predict instability when there is a questionable stability of a fracture. We performed a hybrid retrospective and prospective observational study to establish the safety and utility of FDCSR in cervical spine trauma with incomplete or no neurological deficit.

Methods

We hypothesized that FDCSR is useful and safe in selected patients with SACI with incomplete or no neurological deficits. A combined retrospective and prospective analysis was conducted using hospital records and imaging databases from a tertiary care referral center, covering the period from January 1, 2014, to December 31, 2018. The retrospective component encompassed data from January 2014 to December 2017, while the prospective component included data collected from January 2018 to December 2018.

Ethical approval was not needed as per the institutional guidelines for observational study. Details of the patients who underwent FDCSR were collected.

Radiological Protocol Followed in the Institute

All the patients who present to the hospital with injury to the cervical spine undergo a detailed clinical assessment and neurological examination. The need for imaging is assessed using the National Emergency X-Radiography Utilization Study (NEXUS) tool²³ or the Canadian C-Spine Rule.²⁴ Where imaging is required, static plain radiography and/or CT is employed to evaluate for fractures. MRI is advised in cases when the neurological status is affected. FDCSR are advised if there is

1. No evident bony injury but there is a suspicion of disco-ligamentous injury.

2. In neurologically intact patients: Those with stable injuries on neutral radiographs (<11° angulation relative to adjacent segment and <3.5 mm horizontal translation)

3. In patients with neurological deficit: All fractures with neurological deficit are generally considered to be unstable. However, we perform FDCSR in patients with neurological deficit in degenerative/congenital stenotic canal with no radiologically discernible injury on static radiographs (ie, hyper extension injuries).

4. An evident fracture but stability of which is questionable.

The fractures that are considered unstable includes cervical facet subluxation or dislocation, burst fractures with >50% height loss of the vertebral body, and teardrop injuries. FDCSR were avoided in these fractures. FDCSR were also avoided in polytrauma patients with poor general condition. Traction was not used in any patient during FDCSR.

For FDCSR, it is assumed that the extreme forces required to produce a cervical spine injury are not replicable by an active and physiological flexion and extension of the neck. All patients who undergo FDCSR must be awake, alert and able to obey commands of the physician. FDCSR are not performed on unconscious patients with head injuries. Under supervision, the patient is asked to actively flex and extend the neck as much as possible. The patient is asked to abort the movement and report if there is a feeling of tingling/numbness/weakness in the limbs or if there is unbearable pain.

Parameters Assessed

Demographic details such as age and sex, mode of injury, type of injury and details of treatment received before presentation were retrieved from the data base. Details of the complaints of the patient during FDCSR, and neurological status before and after FDCSR were also retrieved. The following parameters were assessed

Adequacy of Radiographs

FDCSR were considered adequate if the C7/T1 junction could be visualized and there is ≥30° of motion from neutral in either direction.²⁵ Adequacy of FDCSR is essential for the purpose of detecting unstable areas and pinpointing possible injury sites.

Assessment of Instability

Instability was defined as listhesis of greater than 3.5 mm or 11° of relative angulation²⁵ (Figure 1).

Figure 1.

Assessment of Instability With FDCSR. Listhesis of 0.65 cm Between C3-C4 on Flexion (A), Listhesis of 0.56 cm Between C3-C4 on Extension (B) T2 Weighted MRI Mid-Sagittal View (C), and Axial (D) View at C3-C4 Disc Level of the Same Patient With SACI With AIS-C Neurological Status With Doubtful Stability

In patients with instability detected on FDCSR, the clinical details such as the type of management (conservative/surgical), radiological details such as the listhesis/angulation, the type of surgery, blood loss, operative time, preoperative, postoperative follow-up VAS/NDI and follow-up radiological parameter of C2-C7 alignment were collected/measured.

Assessment of Neurological Status Via International Standards for Neurological Classification of Spinal Cord Injury (ISNCSI)

ISNCSI examination was used for assessment of neurological status of the patient. Assessment was performed by trained spine fellow or spine surgeon both before and after the procedure.

Statistical Analysis

All statistical analyses were performed using IBM SPSS (Statistical Package for Social Sciences) Statistics for Windows, Version 25.0. Armonk, NY: IBM Corp. Both descriptive and inferential statistical analysis has been carried out in the study. Results on continuous measurements were presented as mean and standard deviation with range (Min-Max). Results on categorical measurements were presented as numbers (n) and percentages (%). T-test of two independent sample means were used to find significance difference between two independent samples for continuous outcomes with P value <0.05 being significant.

Results

Out of 6890 patients who presented with Traumatic Cervical Spinal Cord Injury during the timeframe of our study, 5.28% (n = 364) patients satisfied the eligibility criteria of FDCSR and were included in the analysis. Mean age was around third to fifth decade with male preponderance. The main mechanism of injury was fall from height affecting C5-C6 level (Table 1).

Table 1.

Characteristics and Epidemiological Data of Patients Included in the Study

Mean age (years)	45.8 +/− 14.49
Gender n (%)	Male: 307 (84.34)
Gender n (%)	Female: 57 (15.66)
Mode of Injury n (%)	Fall from height: 243 (66.76)
	Road Traffic Accident: 119 (32.69)
	Others: 2 (0.55)
Level of Injury n (%)	C3-C4: 42 (11.54)
	C4-C5: 112 (30.77)
	C5-C6: 175 (48.08)
	C6-C7: 35 (9.62)
Interval between Injury to FDCSR n (%)	0-4 days: 112 (30.77)
	5-9 days: 187 (51.37)
	>=10 days: 65 (17.86)

Among the FDCSR of 364 patients, 162 x-rays were inadequate and 202 x-rays were adequate with adequacy rate being 55.5%. Among 202 patients with adequate x-rays, instability was seen in 4.95% (n = 10). Among 162 cases with inadequate FDCSR, instability was seen in 11.7% (n = 19) patients. The overall instability rate in the study was 7.97% (n = 29) (Figure 2).

Figure 2.

Flowchart Depicting the Adequacy Rate and Instability Rate of FDCSR in Our Study

Assessment of any complaints during/following FDCSR was noted. 267 patients were found to have no complaints, while 37 patients had pain/spasm and 60 patients had discomfort during/following FDCSR. The neurological status before and after FDCSR were same: AIS-B in 1.1% (n = 4), AIS-C in 8% (n = 29), AIS-D in 12.6% (n = 46) and normal neurology in 78.3% (n = 285) patients. There was no worsening of neurological status in any patient during/following FDCSR. Instability was predominant at C5-C6 level with most patients undergoing surgery via anterior approach (Table 2).

Table 2.

Descriptive Details of Patients With Cervical Instability in FDCSR

Mean age (years)	46.93 ± 17.73
Gender (n)	24 males, 5 females
Mean listhesis (mm)	4.94 ± 0.92
Mean Relative angulation (degrees)	11.90 ± 3.67
Level of instability	n (%)
C3-C4	5 (17.24%)
C4-C5	7 (24.12%)
C5-C6	17 (58.62%)
C6-C7	0 (0%)
Any deficit following FDCSR	None
Management (n)	Surgical: 25
Management (n)	Conservative: 4
Surgery Type (n)	Anterior surgery: 21
Surgery Type (n)	Posterior surgery: 4
Mean hospital stay (days)	6.52 ± 3.05
Mean operative time (min)	168.97
Mean Blood loss (ml)	141.72 ± 82.98

Among the instability group of patients who underwent surgery, a detailed assessment at preoperative, third month, first year and final follow-up were performed regarding the clinical outcomes via VAS and NDI and radiological outcome of C2-C7 angulation were performed to look for spinal alignment. There was significant decrease in VAS and NDI as well as maintenance of cervical lordosis with subsequent follow up (Table 3).

Table 3.

Preoperative and Postoperative Clinico-Radiological Parameters in Patients Undergoing Surgery in Unstable FDCSR

	VAS	NDI	C2-C7 angle
Preoperative	7.12 ± 1.31	26.48 ± 7.00	30.61 ± 3.05
3 months postoperative	4.14 ± 1.36	11.31 ± 4.67	31.17 ± 3.02
1 year postoperative	2 ± 0.60	8.38 ± 3.90	32.41 ± 2.42
Final follow-up	0.41 ± 0.62	6.28 ± 3.92	34.23 ± 1.81
P value (preoperative vs final follow up)	<0.0001	<0.0001	<0.0001

The patients with stable X-ray in FDCSR were followed up during the time frame of the study. None of these patients had worsening of the neurology with conservative measures (Table 4). Most patients within this group had normal neurological status, while other subgroups with neurological deficits primarily had spinal cord edema and showed some improvement over time.

Table 4.

Descriptive Details of Patients With Stable Cervical Spine in FDCSR

Mean age (years)	42.21 ± 15.33
Gender (n)	283 males, 52 females
Mean listhesis (mm)	1.33 ± 0.32
Mean Relative angulation (degrees)	4.60 ± 1.28
Neurological status	n (%)
No neurological deficits	235 (70.15%)
AIS-D	67 (20%)
AIS-C	21 (6.27%)
AIS-B	12 (3.58%)
AIS-A	None
Any progression of deficit following FDCSR	None

Discussion

While evaluating a patient of cervical spine injury, assessing the stability is vital to decide the management. Plain radiographs, flexion-extension views, and computed tomography exhibited strong diagnostic performance, with high sensitivity and specificity. In comparison, magnetic resonance imaging showed a high incidence of false-positive findings, indicating good sensitivity but poor specificity. Therefore, for conclusively excluding ligamentous instability following a negative cervical spine X-ray or CT scan, the evidence favors the use of fluoroscopic flexion-extension radiographs rather than MRI.²¹ Of note, in patients who are medically unfit for surgical intervention, close follow-up with serial imaging-including repeat functional dynamic cervical spine radiographs (FDCSR) at 6 to 8 weeks-is essential to reassess for persistent or evolving cervical instability. This approach allows for ongoing evaluation of spinal stability as healing progresses, and gives relevant information on subsequent management decisions.

This study assessed the study the safety and utility of Functional Dynamic Cervical Spine Radiographs (FDCSR) under-supervision in assessing stability of select cervical spine trauma cases in non-obtunded patients with incomplete or no neurological deficit. While FDCSR have been utilized in a few centers around the world to diagnose missed cervical spine injuries, its safety and utility in evaluating the stability of a fracture has not been established till date. On analysis, we found that nearly 8% (7.97%) of the instabilities could be additionally detected using FDCSR in cases of acute cervical spine injury with no or incomplete neurological deficit.

Safety

Previous studies by Lewis et al,²⁶ Wang et al,²⁷ Brady et al,²⁸ and Spiteri et al²⁹ found no neurological sequelae following flexion and extension x-rays of the cervical spine. Brooks et al,³⁰ Griffith et al,²⁰ and Freedman et al³¹ did not notice any neurological complications due to the FDCSR in obtunded patients as well. Davis et al³² in 2001 in his study on 301 patients evaluated the efficacy of flexion/extension studies under fluoroscopy in obtunded patients who had normal cervical spine plain films and found that one patient was rendered tetraplegic by the FDCSR. This study demonstrated the rare, but devastating complications that may occur with FDCSR in obtunded patients. Ralston et al³³ in their study related to the pediatric population found transient paresthesia as a complication in 0.8% of the patient. However, the indications of FDCSR in previous studies were to diagnose the injury in cases where a fracture could not be identifiable on an X-ray or CT scan. In contrast, our study assessed, in addition, the safety of FDCSR in cases where a fracture is evident on static X-ray/CT scan but its stability is in question. None of the cases developed neurological deficit.

Utility

Wang et al²⁷ in their study on 290 patients found instability in 1(0.34%) patient. Pollack et al³⁴ found instability in 6 out of 86 subjects (6.98%). Cox et al³⁵ in his 110 patients found instability in 9 (8.18%) patients. Brooks et al³⁰ found fracture or instability in 5/78 patients (6.41%). Insko et al³⁶ in 2002 reported their study on 106 patients, who were awake, had neck pain and normal static radiographs and found cervical spine instability in 9/106 (8.49%) of the patients. These studies were to identify the instability in cases where radiographs were normal and hence differ from our present study.

To our knowledge, no similar study has been reported on the safety and utility of FDCSR to evaluate instability in patients with evident fractures on the static X-ray/CT scan. The study has limitations. X-rays were inadequate in 45.5% of the patients. However, instability could still be detected on inadequate X-rays. Literature review reveals variable adequacy and inadequacy rates of cervical X-ray. Wang et al (1999) in their study found adequacy in 97/290 patients ie, 33.45% of X-rays.²⁷ Anglen et al³⁷ (2002) in their study on 837 patients, found that one-third of the X-rays done to evaluate instability were inadequate. Insko (2002) in their study on 106 patients found 70% of the X-rays inadequate.³⁶ Griffiths et al. (2002) in their study on 447 patients found 59% of the X-rays inadequate, with 31% of the inadequacy due to inadequate motion and 40% of the inadequacy due to inadequate visualisation.²⁰ Bolinger et al. (2004) in their study on 56 patients found adequacy of X-ray only in 4%. He also observed that visualising lower cervical spine in obtunded patients is always inadequate.³⁸ Padayachee et al. (2006) in their study on 276 subjects found inadequacy in 9/276 ie, 3.26% of the cases.³⁹ Khan et al. (2011) in his study of 311 patients found 31% of the X-rays to be inadequate.²⁵ Nasir et al. (2012) in their study on 200 subjects found inadequacy in 45% of the X-rays.⁴⁰ McCracken et al in 2013 found inadequacy in 80% of the X-rays. They described adequacy as visualisation of C7-T1, with 30° change in angle from flexion to extension. It was concluded that adequate flexion extension films are difficult to obtain and are minimally helpful for clearance of the cervical spine in awake and alert trauma patients.⁴¹ Sim et al. (2013) in their study on 155 subjects found 91% inadequacy in X-rays.⁴² Hence, the definition of adequacy of X-rays followed in our study and previous studies may need to be modified since the pain/spasm limits the adequacy of X-rays. The primary reason for inadequate radiographs in our study was patient discomfort or pain, which limited the range of motion during imaging. To address this, we recommend considering the use of pre-procedural analgesia, where appropriate, to improve image adequacy. This strategy warrants further investigation and could be explored in future prospective studies.

Also, since the study involves radiological measurements, errors in calculation of angles and errors in obtaining true lateral radiographs are possible.

Conclusions

In selected patients, FDCSR under supervision can be safely utilized in patients with sub axial cervical spine injury to evaluate for instability. They are useful in identifying instability in occult stable injuries, even in cases where adequate flexion or extension could not be performed.

Footnotes

ORCID iDs

Jeevan Kumar Sharma

Anuj Gupta

Kalyan Kumar Varma Kalidindi

Padmini Yadav

Harvinder Singh Chhabra

Ethical Considerations

Ethical approval was not needed as per institutional guidelines for an observation study issued from Indian Spinal Injuries Center, New Delhi, India.

Consent to Participate

Not required as per the Institutional approval policy for retrospective part. For prospective patients consent was taken.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of Conflicting Interests

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

Data Availability Statement

Will be provided on request.*

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