What are the causes and treatments of midline back pain that does not radiate?

Causes of Midline Back Pain Without Radiation

Midline back pain that does not radiate is most commonly nonspecific mechanical low back pain (>85% of cases), but you must systematically rule out serious underlying pathology including vertebral compression fracture, vertebral malignancy, infection, and inflammatory conditions before settling on this diagnosis. 1

Primary Diagnostic Categories

The overwhelming majority of midline back pain falls into three categories 1:

• Nonspecific mechanical low back pain accounts for >85% of cases and arises from spinal structures such as bone, ligaments, discs, joints, and muscles 1, 2
• Back pain with specific underlying pathology accounts for <2% combined but carries significant morbidity if missed 1
• Back pain with radiculopathy or spinal stenosis (~7%) typically presents with radiation and is less relevant to your question 1

Red Flag Conditions Requiring Immediate Evaluation

Vertebral Compression Fracture (4% prevalence)

• Most likely serious cause of midline-only pain, characterized by midline tenderness in high-risk patients 1
• Risk factors include osteoporosis, postmenopausal status, steroid use, age >50, and frail appearance 1, 3
• Plain radiography is the appropriate initial imaging modality 1

Vertebral Malignancy (0.7% prevalence)

• History of cancer has a positive likelihood ratio of 14.7, jumping posttest probability from 0.7% to 9% 1
• Additional red flags include unexplained weight loss, age >50, and failure to improve with conservative therapy 1
• ESR ≥20 mm/h has 78% sensitivity and 67% specificity for cancer 3, 4
• MRI of the lumbar spine is the diagnostic test of choice, providing superior visualization of vertebral marrow and spinal canal 3

Inflammatory Causes

• Consider in younger patients (<45 years) with chronic symptoms and morning stiffness, as missing this diagnosis delays access to highly effective TNF-blocking agents 1

Infection (Osteomyelitis/Discitis)

• Fever, IV drug use, recent spinal procedure, or immunosuppression warrant urgent evaluation 1
• ESR and MRI are appropriate diagnostic tests 3

Less Common Causes

Anorectal Disorders

• Anal fissures can present as dull aching midline lumbosacral pain without radiation 5
• Specifically ask about anal pruritus, hematochezia, or constipation 5
• Physical exam may be unremarkable; colonoscopy establishes diagnosis 5

Specific Mechanical Causes

• Discogenic pain (without nerve root compression) presents as midline pain 2
• Zygapophysial (facet) joint pain typically causes midline or paraspinal pain 2
• Sacroiliac joint pain may present near midline at lumbosacral junction 5
• Myofascial pain from paraspinal muscles 2

Imaging Strategy

The American College of Physicians recommends against routine imaging in patients with nonspecific low back pain without red flags, as this does not improve outcomes and may lead to unnecessary interventions 1, 4:

• A single lumbar spine x-ray delivers gonadal radiation equivalent to daily chest x-rays for >1 year 1
• Imaging identifies many abnormalities that correlate poorly with symptoms 4
• Delay imaging for at least 1-2 months in patients without red flags 6

When to Image:

• Immediate imaging if any red flags present (cancer history, trauma with fracture risk, neurological deficits, infection risk) 1, 3
• Plain radiography for suspected compression fracture 1
• MRI preferred over CT for suspected malignancy, infection, or when soft tissue visualization needed 1, 3

Critical Pitfalls to Avoid

• Missing vertebral compression fracture in patients with osteoporosis risk factors and midline tenderness 1
• Overlooking cancer in patients with prior malignancy—posttest probability jumps to 9% in this population 1
• Failing to consider inflammatory causes in younger patients with chronic morning stiffness 1
• Ordering routine imaging without red flags exposes patients to unnecessary radiation without clinical benefit 1, 4
• Not asking about anorectal symptoms in patients with lumbosacral midline pain 5

Psychosocial Risk Factors for Chronicity

Assess for yellow flags that predict poorer outcomes 1:

• Depression and passive coping strategies 1
• Job dissatisfaction 1
• Higher baseline disability levels 1
• The STarT Back tool is useful for risk-stratifying patients at 2 weeks 1