When should a lumbar X‑ray be ordered after a fall if the patient has red‑flag signs such as focal lumbar tenderness, inability to bear weight, neurological deficits, a high‑energy mechanism, age ≥ 65, osteoporosis, chronic steroid use, anticoagulation, or prior spinal deformity?

When to Order Lumbar X-ray After a Fall

Order lumbar spine radiographs immediately after a fall if the patient has any of the following red-flag features: focal lumbar tenderness on palpation, inability to bear weight or ambulate, age ≥ 65 years, known osteoporosis or chronic steroid use, anticoagulation therapy, high-energy mechanism (fall ≥ 10 feet, motor vehicle crash ≥ 50 mph, ejection), neurological deficits, or prior spinal deformity. 1, 2

Red-Flag Criteria That Mandate Immediate Radiography

Age and Bone Health Factors:

• Age ≥ 65 years significantly increases fracture risk and warrants upright anteroposterior and lateral radiographs as the initial study 1
• Known osteoporosis or chronic steroid use creates high vulnerability to compression fractures even with minor trauma; radiography is the appropriate first-line modality 1
• The thoracic and lumbar spine are the most common sites for osteoporotic compression fractures, making imaging essential in at-risk populations 1

Mechanism of Injury:

• High-energy trauma (fall ≥ 10 feet, motor vehicle crash ≥ 50 mph, ejection from vehicle) carries a relative risk of 2 for thoracolumbar fracture and mandates imaging 2
• Even seemingly minor trauma in elderly or osteoporotic patients should prompt radiography due to reduced bone density 1

Physical Examination Findings:

• Focal lumbar tenderness on palpation of spinous processes has a positive likelihood ratio of 3.42–12.85 for vertebral fracture and should trigger imaging 3, 4
• Inability to bear weight or ambulate suggests significant structural injury requiring immediate radiographic evaluation 2
• Visible contusion or abrasion over the lumbar spine increases fracture probability (positive likelihood ratio 31.09) and necessitates imaging 3, 4
• Abnormal physical examination (90% sensitivity for positive radiological findings) is a strong indicator for obtaining radiographs 3

Neurological Deficits:

• Any neurological deficit (motor weakness, sensory changes, reflex asymmetry) carries a relative risk of 10 for thoracolumbar fracture and requires immediate imaging 5, 2
• Neurological findings suggest potential spinal canal compromise or nerve root compression that may require urgent intervention 1, 5

Anticoagulation Status:

• Patients on anticoagulation therapy are at increased risk for epidural hematoma and vertebral fracture complications, warranting a lower threshold for imaging 1

Prior Spinal Pathology:

• Pre-existing spinal deformity (scoliosis, kyphosis, prior fusion) alters biomechanics and increases fracture risk at adjacent segments 1, 6

Radiographic Protocol

Standard Views:

• Obtain upright anteroposterior and lateral radiographs as the initial study; upright positioning provides functional information about axial loading 1, 6
• Flexion and extension views may be added to evaluate spinal stability if initial films show concerning findings 1, 6

Limitations to Recognize:

• Radiographs have limited sensitivity for detecting vertebral body comminution, particularly in osteoporotic patients 1
• At least 50% of bone must be eroded before changes become visible on plain films 1
• A negative radiograph does not exclude fracture; if clinical suspicion remains high despite normal X-rays, proceed to advanced imaging 1, 5

When to Escalate to Advanced Imaging

Immediate MRI Indications (No Waiting Period):

• Progressive or severe neurological deficits suggesting spinal cord or cauda equina compression 1, 5, 7
• Suspected spinal cord injury or myelopathy 5, 8
• Radiographs show fracture with concern for canal compromise or retropulsion 1

MRI Without Contrast:

• MRI is superior to radiography for determining fracture acuity (bone marrow edema), assessing spinal canal compromise, and distinguishing benign from pathologic fractures 1
• Useful when radiographs are equivocal but clinical suspicion for fracture remains high 1

CT Lumbar Spine Without Contrast:

• Indicated when MRI is contraindicated or unavailable and detailed assessment of bony integrity is needed 1, 7
• Provides superior visualization of fracture extent and comminution compared to radiography 1

Common Pitfalls to Avoid

• Do not skip imaging in elderly patients with "minor" falls; age ≥ 65 years alone justifies radiography due to high fracture risk 1, 4
• Do not rely on absence of back pain to exclude fracture; 40% of patients with thoracolumbar fractures have no pain or tenderness, and 35% of these require surgical fixation 2
• Do not obtain oblique lumbar views; they double radiation exposure without adding diagnostic value beyond standard AP and lateral films 7
• Do not assume normal radiographs exclude all pathology; proceed to MRI if neurological deficits are present or clinical suspicion remains high 1, 5
• Do not delay imaging for a trial of conservative therapy when red flags are present; these features mandate immediate evaluation 1, 5

Combination of Red Flags

Multiple positive findings significantly increase fracture probability:

• The presence of two or more red flags (e.g., age > 65 + focal tenderness, or steroid use + inability to ambulate) substantially increases the positive likelihood ratio and strengthens the indication for imaging 3, 4
• Combined red flags perform better than individual findings, with greater magnitude and precision of diagnostic estimates 4
• Recent trauma plus age > 50 years is a particularly informative combination for vertebral fracture 9, 4

Special Populations

Patients with Glasgow Coma Scale ≤ 8:

• Altered mental status (GCS ≤ 8) carries a relative risk of 2 for thoracolumbar fracture and mandates imaging regardless of other findings 2

Patients Unable to Provide History:

• When clinical examination is limited, a lower threshold for imaging should be applied, particularly if mechanism suggests high energy 2, 8