Backache - Differential Diagnosis & Management

Epidemiology

Classification

Differential Diagnosis

1. Mechanical (>95% of LBP)

• Lumbosacral strain/sprain - most common cause overall; acute injury, paraspinal tenderness, muscle spasm; no neurological deficit
• Lumbar disc herniation - shooting/stabbing pain radiating down leg; L4-5 herniation: pain to dorsomedial foot; L5-S1 herniation: pain to lateral foot/small toe; positive straight leg raise (SLR); weakness of tibialis anterior (L5) or peroneus longus/brevis (S1)
• Lumbar facet joint syndrome - found in up to 35% of LBP cases; unilateral/bilateral low back pain radiating to thigh (not below knee); pain worsened by extension and lateral rotation; negative SLR; normal neurology
• Lumbar spinal stenosis - neurogenic claudication; bilateral leg pain/weakness with walking that is relieved by sitting/forward flexion (shopping cart sign); older patients
• Spondylolisthesis - anterior displacement of vertebral body (typically L5 on S1); may cause local or radicular pain
• Osteoporotic vertebral compression fracture - acute severe pain in post-menopausal woman; no preceding trauma

2. Inflammatory

• Spondyloarthritis (ankylosing spondylitis, PsA, reactive arthritis, IBD-associated) - age <40, insidious onset, morning stiffness >30 min, improves with exercise, alternating buttock pain, nocturnal pain in 2nd half of night; raised ESR/CRP, HLA-B27 positive
• Rheumatoid arthritis (less commonly causes LBP)

3. Infectious

• Vertebral osteomyelitis / discitis - fever, elevated inflammatory markers, palpation tenderness; night pain; often Staphylococcus aureus; requires antibiotics; MRI is investigation of choice
• Epidural abscess - spinal emergency; fever + back pain + neurological deficit
• Pott's disease (TB spine) - in endemic areas/immunocompromised

4. Neoplastic

• Metastatic disease (breast, lung, prostate, kidney, thyroid) - most common malignant cause; nocturnal pain not relieved by rest; history of malignancy; weight loss
• Primary spinal tumours (rare: meningioma, schwannoma, ependymoma)
• Multiple myeloma

5. Sacroiliac (SI) Joint Syndrome

• Unilateral low back/buttock pain radiating to hip or thigh; worsened climbing stairs; positive Patrick/FABER test; positive single-leg standing test - Bradley & Daroff's Neurology

6. Referred / Non-Spinal Causes

• Renal: pyelonephritis, nephrolithiasis (colicky, costovertebral angle tenderness)
• GI: peptic ulcer (penetrating), pancreatitis, retroperitoneal pathology
• Vascular: aortic aneurysm (pulsatile, expansile mass; vascular emergency)
• Gynaecological: endometriosis, uterine fibroids, ovarian pathology
• Prostate disease

7. Psychological / Biopsychosocial

• Chronic LBP has high co-prevalence with depression (33-67%), anxiety (10-30%), substance misuse (13-40%), and personality disorders (>50%). Psychosocial yellow flags (job dissatisfaction, disability claims, fear-avoidance) prolong chronicity. - Harrison's 22e

Red Flags (requiring urgent imaging - preferably MRI)

Note: Individual red flags have low sensitivity and specificity. The presence of multiple red flags significantly increases predictive value and should guide imaging decisions. - Firestein's Rheumatology

Investigations

Management

Step 1 - Acute Mechanical LBP (< 6 weeks)

• Reassurance and patient education - avoid bed rest; early return to normal activity within 2 weeks is widely recommended
• Targeted physiotherapy and core-strengthening exercises
• Heat application
• Manual therapy / spinal manipulation (modest benefit; non-inferior to other physical therapies)
• Massage (short-lived benefit for spasmodic/tension-based pain)

• NSAIDs - first-line analgesic (e.g., ibuprofen, naproxen, diclofenac); reduce inflammation and pain
• Non-benzodiazepine muscle relaxants (e.g., methocarbamol, cyclobenzaprine) - useful for spasm
• Paracetamol - no longer recommended as first-line; insufficient evidence for back pain specifically
• Opioids - short-term only for debilitating acute pain; lowest effective dose; avoid long-term; never combine with benzodiazepines (risk of respiratory depression)
• Gabapentinoids (gabapentin, pregabalin) - insufficient evidence for either axial or radicular back pain

Step 2 - Specific Cause Management

• NSAIDs + muscle relaxants + physiotherapy as initial treatment
• If not improving: lumbar epidural steroid injection (LESI) for fast relief (if no severe neural compression)
• Surgery (microdiscectomy) for: moderate-severe focal neurological deficit, bowel/bladder dysfunction, or severe pain >3 months not responding to conservative management

• NSAIDs first line
• If refractory: diagnostic medial branch block; intra-articular corticosteroid injection; radiofrequency ablation (medial branch neurotomy)

• NSAIDs first line
• SI joint corticosteroid injection for temporary relief
• Radiofrequency ablation if injections give short-lived benefit

• Physiotherapy, NSAIDs, analgesics
• Epidural steroid injections
• Surgical decompression (laminectomy) for severe/progressive neurological deficits

• NSAIDs (high doses); exercise is important
• TNF inhibitors / IL-17 inhibitors for NSAID-refractory disease

• IV antibiotics (target organism); surgical drainage if abscess, instability, or neurological compromise

• Analgesia, mobilisation, osteoporosis treatment (bisphosphonates, calcium/vitamin D)
• Kyphoplasty/vertebroplasty in selected cases

• Radiotherapy, steroids (for cord compression), surgical stabilisation, systemic oncology treatment as appropriate

Step 3 - Chronic LBP (> 3 months)

• Biopsychosocial model - address psychological comorbidities (depression, anxiety, catastrophisation, fear-avoidance)
• Cognitive-behavioural therapy (CBT) - reduces pain intensity; strong evidence
• Mindfulness-based stress reduction (MBSR)
• Yoga, Tai Chi - evidence for benefit
• Acupuncture - modest, short-lived benefit; true acupuncture slightly superior to sham

• Duloxetine (SNRI) - evidence for pain reduction in chronic LBP; also addresses comorbid depression
• Tricyclic antidepressants - analgesic benefit independent of antidepressant effect
• NSAIDs (with gastroprotection)
• Opioids are not recommended for long-term use; no demonstrated long-term benefit for pain or function

• Fluoroscopic epidural steroid injections (for radicular component)
• Facet joint injections / medial branch blocks
• Radiofrequency ablation
• Spinal cord stimulation (for refractory cases)

• Indicated for progressive neurological deficit, cauda equina syndrome, or failure of ≥3 months of comprehensive conservative treatment with confirmed structural lesion on imaging

MRI Images of Common Structural Causes

Summary Table