X-ray of the lumbosacral spine: how it is done

Lumbosacral radiography is a projectional X-ray examination that allows for the assessment of intervertebral space height, endplate contours, osteophytes, antelisthesis and retrolisthesis, signs of acute and chronic fractures, and gross instability on functional images. Clinically, this method is used as an accessible "first line" for suspected low-energy trauma, deformity, and for basic documentation of known structural changes. [1]

In uncomplicated acute low back pain without alarm features, imaging is generally not indicated in the first few weeks, as complaints are often self-limited and routine imaging does not change management. This approach is consistent with the American College of Radiology's appropriateness criteria and clinical guidelines for the management of low back pain. [2]

If moderate- or high-energy trauma is suspected, especially in the elderly and those with osteoporosis, the role of X-rays is limited: computed tomography (CT) is more sensitive for the initial diagnosis of thoracolumbar fractures, better at detecting multiple and occult injuries. In emergency traumatology, CT is considered the first-line procedure. [3]

Thus, the location of radiography is pinpointed: in case of uncomplicated pain it is often not required, in case of high-risk trauma it is inferior to sectional methods, and in chronic and deformative conditions it helps to quickly obtain a reference point and monitor the dynamics. [4]

What does an X-ray show and where are its boundaries?

Standard projections allow the physician to visualize the height of the intervertebral spaces, osteophytes, endplate sclerosis, spondylolisthesis, severe fractures of the spinous and transverse processes, compression deformities of the vertebral bodies, and also to roughly assess the facet joints. This provides the basis for describing degenerative and traumatic changes. [5]

Detection of dynamic instability is possible using a pair of functional flexion and extension radiographs; however, studies show that such radiographs often underestimate the true mobility of the segment. Comparison of standing radiographs with prone magnetic resonance imaging (MRI) data increases sensitivity for instability. [6]

Oblique views have historically been used in suspected spondylolysis cases, but current literature does not demonstrate a convincing benefit in sensitivity compared to the anteroposterior plus lateral set, while the dose load is higher. Therefore, routine inclusion of oblique views is no longer recommended. [7]

The main limitations of X-rays are their low sensitivity to hidden fissures, early inflammatory and soft tissue changes, and root compression. If X-rays are negative and clinical suspicion persists, a transition to computed tomography and magnetic resonance imaging is warranted. [8]

Table 1. Lumbar X-ray: strengths and limitations

Parameter	Strengths	Restrictions
Availability	Fast, everywhere	Less sensitivity to hidden fractures
Degenerative changes	Osteophytes and the height of the cracks are clearly visible	Does not show bone swelling and nerve structures
Instability	Functional series are possible	May underestimate segment mobility
Dose	Lower than CT scan	Higher with extended series and oblique projections

Summarized from methodological reviews and studies on functional and oblique images. [9]

Indications in adults: when is x-ray appropriate?

In acute pain without "red flags," imaging in the primary care setting is not indicated, as most cases improve within 4 weeks of conservative treatment. "Red flags" include oncologic suspicion, infection, significant deficits, trauma, progressive neurologic symptoms, and suspicion of cauda equina syndrome.[10]

In cases of minor trauma in the elderly, with long-term glucocorticosteroid use, and with known osteoporosis, radiography is warranted as an initial investigation to detect a compression fracture, especially if complaints are localized and there is palpable tenderness of the spinous processes. Further management depends on the clinical presentation and radiographic findings. [11]

If moderate- or high-energy trauma is suspected, computed tomography (CT) is preferred for the initial diagnosis of thoracolumbar junction injuries, as it is superior to radiography in sensitivity and speed in the emergency setting. This is reflected in current trauma guidelines. [12]

In chronic pain with planned invasive treatment, radiographs are acceptable for an initial "map" of deformities and levels; however, the choice of approach and extent of intervention is determined by cross-sectional imaging data. Appropriateness criteria emphasize the need to correlate images with symptoms. [13]

Table 2. "Situation - appropriateness of X-ray - next step"

Situation	X-ray	The next step
Acute pain without red flags	Not shown	Observation and conservative therapy
Suspected compression fracture with minor trauma	Shown	If in doubt, computed tomography
Moderate to high energy trauma	Limited role	The first line is computed tomography
Planning invasive treatment	Let's say for reference	Solutions based on magnetic resonance imaging and computed tomography data

Summary of relevance criteria and traumatological sources. [14]

Technique and projections: how to get an informative image

The standard includes an anteroposterior projection and a lateral projection in the standing or prone position, with a narrow collimation on the lumbar spine. The anteroposterior projection shows symmetry, the height of the disc spaces and facet joints, while the lateral projection shows the vertebral bodies, endplates, and sagittal balance. [15]

An additional targeted lateral projection at the L5-S1 level is used to clarify the lower intervertebral spaces when standard lateral imaging is insufficient. Research assesses how often this "cone beam" image actually adds significant information and suggests individualizing its use. [16]

Functional radiographs in flexion and extension are used when instability is suspected. It should be remembered that the classic flexion-extension pair may underestimate the true extent of displacement, so interpretation is based on clinical findings and data from other methods. [17]

Oblique projections for spondylolysis are not routinely recommended due to the lack of proven sensitivity gain compared to standard pairs and the increased dose involved. The choice to perform them selectively is left to discretion in cases of atypical defect location. [18]

Table 3. Projections and their tasks

Projection	Task	Comment
Anteroposterior	Symmetry, height of slits, facets	Basic overview assessment
Side	Vertebral bodies, endplates, sagittal profile	Compression wrench
L5-S1 sighting	Detailing of lower levels	Assign when visibility on standard side is insufficient
Functional series	Search for instability	May be underestimated, interpret in clinical context

Summarized from methodological articles and positions on “cone” projections. [19]

Radiation exposure and how to reduce it

The estimated effective dose for lumbar radiography in adults is approximately 1.4 mSv, which is equivalent to approximately 6 months of natural background radiation. The actual dose depends on the number of projections, body weight, and device parameters. [20]

Minimizing exposure is achieved through tight collimation, avoiding unnecessary oblique projections, precise image capture to prevent blur and duplicate images, and proper selection of exposure parameters. Quality control and auditing of duplicates are practical tools for reducing total dose. [21]

The current position of professional radiation safety societies does not support routine gonadal shielding during radiography, as it does not improve the benefit-risk ratio and may obscure diagnostically significant areas. Instead, emphasis is placed on collimation and parameters. [22]

For comparison, spinal computed tomography (CT) uses higher doses than projectional radiography, but CT provides the necessary sensitivity for trauma. The decision on the method of choice is made by the physician, taking into account the clinical presentation and the expected impact on the treatment plan. [23]

Table 4. Examples of dose guidelines

Study	Approximate effective dose
X-ray of the lumbar spine	about 1.4-1.5 mSv
Computed tomography of the spine	about 6 mSv and higher depending on the protocol
Natural background per year	about 3.0 mSv

Summary of reference materials on doses. [24]

Special clinical situations

When spondylolysis is suspected in adolescents, the initial test often remains radiography with an emphasis on lateral views, while the need for oblique views is controversial and has not been proven to increase diagnostic value. If images are negative and clinical symptoms persist, cross-sectional methods are indicated. [25]

Functional radiographs are used to assess instability, but some studies indicate decreased mobility with standard pairing. Comparison of standing radiographs and prone magnetic resonance imaging may better detect occult instability. [26]

Postoperatively, radiography is useful for basic implant position monitoring and rough assessment of screw position, but if complications are suspected, computed tomography and magnetic resonance imaging are preferred because they provide more precise assessment of bone and soft tissue structures. The appropriateness criteria emphasize this distinction. [27]

If inflammatory spondyloarthritis is suspected, lumbar X-rays are supplemented with visualization of the sacroiliac joints, and in the early stages, magnetic resonance imaging is more informative to detect bone edema. In the absence of bone pathology, X-rays do not rule out an inflammatory process. [28]

Table 5. "Question

Clinical question	Preferred method	Why
Spondylolysis in a teenager	X-ray, if necessary, cross-sectional methods	Fast, affordable, but obliques don't provide any growth
Dynamic instability	Functional imaging plus correlation	A classic pair can reduce mobility
Suspected complications after surgery	Computer and magnetic resonance imaging	Detailing of bone and soft tissues
Inflammatory nature of pain	Magnetic resonance imaging of the sacroiliac joints	Early visualization of bone edema

Summarized from thematic sources. [29]

Pediatric practice

In children, routine imaging for low back pain without "red flags" is not indicated. Indications are formulated strictly to avoid unnecessary exposure, guided by the same principles as in adults: suspicion of serious pathology, trauma, or progressive deficit. [30]

When necessary, radiography is performed with narrow collimation and a minimum of projections, avoiding unnecessary additional views. Current radiation safety guidelines do not recommend routine gonad shielding; emphasis is placed on parameters and collimation. [31]

In children, as in adults, with high suspicion, computed tomography is preferred due to its greater sensitivity to fractures, especially in multilevel injuries. The decision is made individually, taking into account age and clinical characteristics. [32]

If spondylolysis is suspected, initial radiography in adolescents is appropriate, but if the images are negative and symptoms persist, magnetic resonance imaging or computed tomography is chosen for clarification. This helps avoid missing isthmus defects. [33]

Table 6. Indications for X-rays in children and protective measures

Situation	Recommendation
Pain without red flags	No visualization needed
Suspected injury	Assess the clinical picture; if there is high suspicion, perform a computed tomography scan.
Spondylolysis	X-ray as a starting point; if in doubt, use cross-sectional methods
Radiation protection	Collimation, minimum projections, no routine gonadal shielding

Summarized from imaging and safety recommendations. [34]

Interpretation and next steps

If an X-ray reveals a compression fracture, its height, wedge-shaped form, and posterior wall involvement are assessed. If signs are equivocal and pain is severe, a CT scan is ordered to clarify the morphology and stability. This is especially important in the elderly and when taking glucocorticosteroids. [35]

If radiographs are negative and symptoms persist, especially if the pain is radicular in nature, the next step is magnetic resonance imaging to evaluate the discs, roots, and soft tissues, or computed tomography in the case of a traumatic etiology. The choice of method determines the treatment strategy. [36]

If "red flags" such as cauda equina syndrome, malignancy, or infection are present, imaging, primarily magnetic resonance imaging, is required without delay to avoid missing the treatment window. Recent international guidelines emphasize avoiding unnecessary imaging while simultaneously promoting timely examination in cases of serious pathology. [37]

To reduce unnecessary research, following consensus guidelines and criteria for appropriateness is helpful. Systematic reviews show that the use of such guidelines improves the quality of care and reduces costs. [38]

Table 7. "X-ray finding - what next"

Find	Action
Compression fracture	Computed tomography for clarification, treatment plan
Gross instability	Sectional visualization, consultation with a specialist
Degenerative changes without red flags	Conservative therapy, without urgent post-slice imaging
Normal values for persistent symptoms	Magnetic resonance imaging for soft tissue assessment

Summarized by appropriateness criteria and clinical standards. [39]

Frequently asked questions

Is any preparation necessary before an X-ray? There is no special preparation: metal objects are removed, the patient remains still, and, if possible, images are taken standing to better assess the sagittal profile. The physician determines which projections are necessary. [40]

Is the dose harmful? The dose is low, typically around 1.4 mSv per examination in an adult, which is comparable to approximately 6 months of natural background radiation. With proper collimation and avoidance of unnecessary radiation, the exposure is even lower. [41]

Why doesn't everyone get imaging for low back pain? Because in the absence of "red flags," routine imaging doesn't improve outcomes, and in the first few weeks, pain often improves with conservative therapy. Guidelines recommend avoiding unnecessary imaging. [42]

Why are "functional" images sometimes requested? They can help suspect instability, but they can underestimate its severity, so the results are considered in conjunction with the clinical picture and data from other imaging studies. Treatment decisions are always comprehensive. [43]