X-ray of the spine and spinal cord: objectives of the study

Spinal radiography is a method of visualizing bone structures using ionizing radiation. In modern practice, it is used selectively: for the initial detection and classification of vertebral injuries, monitoring the position of implants, and assessing axial deformities and gross degenerative changes. For the soft tissues of the spinal canal, spinal cord, and nerve roots, magnetic resonance imaging is the primary method. This shift is due to the fact that X-rays primarily show bone, whereas neurological symptoms are more often caused by compression or pathology of soft tissues. [1]

The key idea behind the "right test for the right patient" approach is to avoid imaging where it won't change the management. For example, in cases of acute low back pain without any "red flags," imaging is unnecessary, and if cauda equina compression or infection is suspected, magnetic resonance imaging is the first test. This reduces unnecessary tests, costs, and radiation exposure. [2]

It is especially important to understand the role of computed tomography and myelography. Computed tomography complements X-rays in complex fractures and postoperative evaluation of bone grafting and screws, while computed tomography with myelography remains an option when magnetic resonance imaging is contraindicated or uninformative. [3]

When is an x-ray indicated?

X-rays are most valuable when a fracture is suspected after trauma, especially when available before CT scanning, as well as for monitoring deformities such as scoliosis and assessing static-dynamic axis disturbances. In neck trauma, clinical selection rules, such as the Canadian Cervical Spine Rules and the NEXUS criteria, guide imaging decisions, helping to avoid unnecessary examinations in low-risk patients. [4]

After spinal surgery, X-rays are the primary "baseline" imaging method immediately after the procedure and for subsequent visits: they allow for assessment of implant position, structural integrity, and gross instability during functional flexion and extension tests. If problems with the bone block are suspected or to clarify the fine geometry of the screws, computed tomography is added. For soft tissue complications, magnetic resonance imaging is preferred. [5]

For deformities in children and adolescents, standing X-rays remain the standard for measuring the Cobb angle and assessing global balance. Where a dual-plane slot-scanning system, such as low-dose technology, is available, the dose can be significantly reduced for serial imaging. [6]

In degenerative changes, X-rays help to see a decrease in the height of intervertebral discs, osteophytes, facet arthrosis and sagittal imbalance, but do not show herniations and canal stenosis, so in case of neurological deficit, other methods will be required. [7]

When X-rays are ineffective and what they are replaced with

If spinal cord or root compression, cauda equina syndrome, epidural abscess, discitis, or tumor are suspected, X-rays "see" too little and may delay proper diagnosis. Here, the first line of treatment is magnetic resonance imaging of the relevant area, either without enhancement or with enhancement as indicated. X-rays are usually uninformative in cases of infections and early tumor lesions. [8]

In acute low back pain without warning signs, imaging in the first 6 weeks does not improve outcomes and is not recommended. Conversely, in the presence of "red flags" such as trauma, immunosuppression, fever, rapidly progressing neurological deficits, or a history of cancer, immediate imaging, guided by magnetic resonance imaging, is indicated. [9]

In low-risk neck trauma patients, imaging may be omitted according to validated guidelines, but if it is not possible to "clear" the neck according to clinical guidelines, CT scanning becomes the imaging modality of choice because the sensitivity of X-rays to subtle injuries is low.[10]

If magnetic resonance imaging is contraindicated and an assessment of the dural sac and nerve roots is required, myelography followed by computed tomography is performed. This is especially useful in cases of significant metal artifacts, the inability to position the patient, or the presence of incompatible devices. [11]

How is an X-ray performed and how to prepare for it?

Preparation is usually minimal. The patient is asked to remove metal objects, ensure immobility, and maintain proper positioning. Standard AP and lateral views are performed while standing to assess the axis, and functional flexion and extension tests may be performed to detect instability. Strict positioning and coverage of the target area, including adjacent levels if injured, enhance the effectiveness of the examination. [12]

If cervical spine injury is suspected, active neck movements are prohibited until clinical "clearance" is achieved, and immobilization is maintained until imaging is decided. If the patient does not meet the clinical criteria, CT scanning is preferred, and X-rays are used sparingly. [13]

Postoperative studies are planned to obtain a baseline image shortly after the procedure for further comparison. Dynamic comparisons are made of alignment, interbody block height, absence of screw migration, and signs of instability based on functional tests. [14]

Any examination using ionizing radiation must be justified. The patient is informed of the expected benefits and alternative non-radiation methods, such as magnetic resonance imaging and ultrasound, if such alternatives are appropriate for the clinical task. [15]

Safety and radiation dose

The effective dose from a lumbar X-ray per projection is typically approximately 1.5 millisieverts, which is comparable to several months of natural background radiation; a series of two projections will yield a higher total dose. For comparison, an X-ray of an extremity delivers thousandths of a millisievert. In any case, the dose varies depending on the equipment, technique, and patient anatomy. [16]

During pregnancy, diagnostic doses for examinations outside the uterus are generally significantly lower than the thresholds associated with a deterministic risk to the fetus. The rule is simple: if an examination is indicated and affects management, it should not be delayed, but non-radiation methods are preferred. Current guidelines also indicate that the routine use of lead "aprons" to protect the gonads and fetus is not recommended, as this may impair automatic exposure and even increase the dose. [17]

In children, attention is paid to the total dose during deformity monitoring. Low-dose, dual-plane, slot-scanning systems allow for a significant reduction in radiation exposure while maintaining diagnostic quality in the upright position. In their absence, the dose is minimized through gentle protocols and reducing the frequency of examinations to that clinically necessary. [18]

For frequent serial studies, it is advisable to maintain an individual dose chart and use standardized protocols. Discussing the principles of justification and optimization with the patient and parents increases trust and compliance with monitoring. [19]

Table 1. Strengths and weaknesses of spinal imaging techniques

Method	What shows best	Where is the first choice method?	Restrictions
X-ray	Bone, alignment, implants, dynamic instability	Low-complexity trauma, deformities, postoperative control	Poor vision of the disc, ligaments, canal, and spinal cord
Computed tomography	Details of bone, minor fractures, screws, bone block	Complex fractures, planning and monitoring after surgery	Ionizing radiation, metal artifacts
Magnetic resonance imaging	Disc, ligaments, muscles, roots, spinal cord, abscesses	Neurological deficit, infections, tumors, stenosis	Contraindications, artifacts, less availability
Computed tomography with myelography	Lumen of the dural sac in cases of contraindications to magnetic resonance imaging	Magnetic resonance imaging cannot be performed due to strong artifacts.	Invasiveness, ionizing radiation, contrast
[20]

Table 2. Red flags of back pain for which imaging is indicated immediately

Category	Examples of signs
Infection	Fever, intravenous drug use, immunosuppression, elevated inflammatory markers
Oncology	Known malignancy, unexplained weight loss, night pain
Neurology	Progressive deficiency, pelvic dysfunction, saddle anesthesia
Trauma and osteoporosis	Recent trauma, old age, long-term use of glucocorticoids
[21]

Table 3. Choice of method in typical clinical situations

Situation	Recommended first
Acute lower back pain without red flags	Visualization is not required at the start, conservative management
Acute lower back pain with red flags	Magnetic resonance imaging of the relevant area; if contraindicated, computed tomography with contrast as indicated.
Suspected spinal infection	Magnetic resonance imaging without and with enhancement as indicated
Cervical spine injury with positive clinical rules	Computed tomography of the cervical spine
Postoperative check of implants	X-ray and dynamic tests, in case of problems, additionally computed tomography
[22]

Table 4. Estimated effective doses for radiological procedures

Study	Effective dose, millisievert
X-ray of the limb, one projection	0.001
Chest X-ray, one projection	0.02
Chest X-ray, two projections	0.1
X-ray of the lumbar spine, lateral projection	1.5
[23]

Table 5. Classification of thoracolumbar fractures according to AO Spine, enlarged

Type	The nature of the damage	An example of visualization tactics
Type A	Compression fractures of the anterior column	Computed tomography to clarify morphology, X-ray for dynamics
Type B	Translocation and distraction injuries of the posterior elements	Computed tomography is mandatory, magnetic resonance imaging to evaluate the ligaments
Type C	Rotational-translational unstable injuries	Comprehensive assessment, computed tomography and magnetic resonance imaging
[24]

Table 6. Children and serial images for deformities

Task	Preferred technique	Comments on dosage
Serial evaluation of scoliosis	Dual-plane slot-scanning low-dose system if available	Up to 10 times lower, micro-dose mode even lower
In the absence of such a system	Standard standing x-rays for strict indications	Reduce frequency, low dose protocols
[25]

Table 7. When is computed tomography with myelography needed?

Clinical task	Why not magnetic resonance imaging?	The role of myelography
Heavy metal artifacts	Signal distortion, inability to assess the dural sac	Contrast in the subarachnoid space followed by CT scan shows the outline of the sac and roots
Contraindications to magnetic resonance imaging	Non-removable devices, inability to lie still	Alternative visualization of stenosis and compression
Uninformative magnetic resonance imaging in stenosis	Data conflict, audit planning	Accurate assessment of the level and extent of the block
[26]

Trauma: How neck and back imaging is decided

In the emergency department, validated guidelines are used for awake patients without neurological deficits and at low risk of neck injury. If at least one high-risk criterion is present or the patient is unable to safely perform an active head rotation test, imaging is necessary. This reduces unnecessary examinations while maintaining safety. [27]

If the clinical rule is not met, CT scanning of the cervical spine is preferred, as radiography is less sensitive to subtle fractures and subluxations. In severely ill patients, CT scanning is immediately combined with other trauma protocols. [28]

In the thoracic and lumbar spine, computed tomography (CT) is also preferred for high-energy trauma to rule out multifragment fractures and retropulsion. X-rays are useful for preliminary screening in cases with a low probability of complex injury and for dynamic evaluation. The AO Spine classification helps standardize communication between the traumatologist, surgeon, and radiologist. [29]

Functional flexion and extension tests are performed only in neurologically stable patients and not immediately after injury. With limited range of motion, even functional imaging may be uninformative, and magnetic resonance imaging is then indicated. [30]

Infection and tumors: why x-rays don't help

If discitis, osteomyelitis, epidural abscess, or spondylodiscitis is suspected, the first method is magnetic resonance imaging without enhancement and, if necessary, with enhancement. X-rays are either normal or show late bone-destructive changes and are therefore only suitable for indirect dynamics. [31]

Infection guidelines emphasize the need for confirmation of the pathogen by blood culture or image-guided biopsy. This is critical for the initiation of etiotropic therapy and reduces the risk of unnecessary surgery. [32]

In cases of spinal tumors and suspected spinal cord compression, magnetic resonance imaging is also the preferred method. X-rays can reveal vertebral collapse or lytic lesions, but they do not assess extension into the epidural space or the degree of compression. [33]

If magnetic resonance imaging is not possible, computed tomography (CT) is appropriate, and if the lumen of the canal is in question, CT with myelography is appropriate. The choice depends on the clinical problem, availability, and risk profile. [34]

Degenerative Diseases and Stenosis: The Right Course of Action

For neck and back pain without neurological deficits, conservative therapy and observation are the initial treatment. If radicular symptoms, weakness, sensory disturbances, or persistent pain syndrome that changes management develop, magnetic resonance imaging of the affected area is performed. X-rays are useful for a general assessment of alignment and gross bony factors, but do not answer the main question of compression. [35]

In spinal stenosis, magnetic resonance imaging (MRI) determines the extent, levels, and condition of the nerve structures. If this method is contraindicated or distorted by artifacts, myelography followed by computed tomography (CT) is an alternative. This helps precisely localize the level for intervention or surgery. [36]

Following surgery for degenerative pathology, baseline radiographs are important for dynamic comparison. If new pain, fever, or neurological deficits develop, magnetic resonance imaging (MRI) reveals edema, granulation tissue, recurrent disc herniation, fluid, and abscesses. Computed tomography (CT) shows consolidation of the interbody joint and signs of loosening of the fixation. [37]

For the cervical spine, magnetic resonance imaging (MRI) is the preferred method for suspected myelopathy. Recent reviews highlight advances in understanding structural and even supraspinal changes, which impact treatment planning. X-rays are also helpful for alignment. [38]

Frequently asked questions

Is it safe?
Yes, with proper justification and dose optimization, radiography is considered a safe procedure. The doses are low compared to other sources, and in pregnant women, decisions are made on an individual basis, with priority given to non-radiation methods. Routine gonadal screening is currently not recommended by specialized societies. [39]

Why is imaging sometimes "not done right away"?
Because in uncomplicated acute low back pain, imaging does not improve outcomes or change management. When there are warning signs, imaging is performed immediately, and the method that best answers the clinical question is selected. [40]

When are extension and flexion imaging needed?
Only in cases of stable neurological status, to assess functional instability. In the cervical spine, with limited mobility, it is better to switch to magnetic resonance imaging rather than forceful testing. [41]

What to choose if magnetic resonance imaging is not possible?
Computed tomography with myelography helps assess the lumen of the dural sac and rootlet conflict with high geometric accuracy, especially in the presence of metal structures. The decision is made by the physician, taking into account the risks and objectives. [42]