Lower back pain

Background

• Pain lasting >6wks is risk factor for more serious disease
• Night pain and unrelenting pain are worrisome symptoms
• Back pain in IV drug user is spinal infection until proven otherwise
• 95% of herniated discs occur at L4-L5 or L5-S1 (for both pain extends below the knee)
• Lumbago: acute, nonspecific back pain

Clinical Features

Lumbar nerve root distribution

• Musculoskeletal pain
  • Located primarily in the back w/ possible radiation into the buttock/thighs
  • Pain worse w/ movement but improves w/ rest
• Spinal stenosis
  • Bilateral sciatic pain worsened by walking (pseudo-claudication), prolonged standing
  • Pain relieved by forward flexion, esp sitting
• Sciatica
  • Radicular back pain in the distribution of a lumbar or sacral nerve root
    • Anything that compresses the nerve roots, cauda equina, or cord can cause sciatica
  • Pain worsened by coughing, Valsalva, sitting; relieved by lying in supine position
  • Occurs in only 1% of pts w/ back pain
  • Present in 95% of pts who have a symptomatic herniated disk
• Urinary/bowel disturbances, perineal anaesthesia
  • Cauda equine syndrome, due to compression of spinal nerve roots
  • Ortho emergency!
• Inflammatory back pain
  • Morning stiffness >30minutes
  • Consider seronegative spondyloarthropathies, esp if in young adults (eg ankylosing spondylitis, psoriatic arthropathy, IBD arthropathy, Reiter's disease)

Back Pain Risk factors and probability of Fracture or Malignancy

Factor	Post Test Probability (95%CI)
Older Age (>65yo)	9% (3-25%)
Prolonged corticosteroid	33% (10-67%)
Severe trauma	11% (8-16%)
Presence of contusion or abrasion	62% (49-74%)
Multiple red flags	90% (34-99%)
History of malignancy	33% (22-46%)

Red Flag Symptoms of Low Back Pain

Symptoms	Corresponding Pathology
Age under 18 years	Congenital abnormality
Age over 50 years	Fracture, malignancy
Anticoagulant use	Spinal hematoma
Fever	Infection, malignancy
Genitourinary issues including urinary retention/incontinence or sexual dysfunction	Cauda equina syndrome
Immunocompromised	Fracture, infection
IV drug use	Infection
Recent spinal surgery or epidural injection	Infection, spinal hematoma
Trauma	Fracture, spinal hematoma

Red Flag Signs of Low Back Pain

Signs	Corresponding Pathology
Reduced anal sphincter tone	Cauda equina syndrome
Hyperreflexia	Acute cord compression
Hyporeflexia/areflexia	Cauda equina syndrome
Lower extremity muscle weakness	Acute cord compression or Cauda equina syndrome
Saddle paresthesia/anesthesia	Cauda equina syndrome
Absent or decreased bulbocavernosus reflex	Cauda equina syndrome

Differential Diagnosis

Lower Back Pain

• Spine related
  • Acute ligamentous injury
  • Acute muscle strain
  • Disk herniation (Sciatica)
  • Degenerative joint disease
  • Spondylolithesis
  • Epidural compression syndromes
    • Spinal cord compression (non-traumatic)
    • Cauda equina syndrome
    • Conus medullaris syndrome
    • Epidural abscess (spinal)
    • Epidural hematoma (spinal)
  • Thoracic and lumbar fractures and dislocations
  • Cancer metastasis
  • Spinal stenosis
  • Transverse myelitis
  • Vertebral osteomyelitis
  • Ankylosing spondylitis
  • Spondylolisthesis
  • Discitis
  • Spinal Infarct
• Renal disease
  • Kidney stone
  • Pyelonephritis
  • Nephrolithiasis
• Intra-abdominal
  • Abdominal aortic aneurysm
  • Ulcer perforation
  • Retrocecal appendicitis
  • Large bowel obstruction
  • Pancreatitis
• Pelvic disease
  • PID
• Other
  • Retroperitoneal hemorrhage/mass
  • Meningitis

Work-Up

1. Pregnancy test
2. Exam
   1. Straight leg raise testing
      1. Screening exam for a herniated disk (Sn 68-80%)
      2. Lifting leg causes radicular pain of affected leg radiating to BELOW the knee
      3. Pain is worsened by ankle dorsiflexion
      4. Pain may be relieved by pressing across biceps femoris and pes anserinus tendons behind knee ('bowstringing')
   2. Crossed Straight leg raise testing (high Sp, low Sn)
      1. Lifting the asymptomatic leg causes radicular pain down the affected leg
   3. Nerve root compromise
   4. Rectal exam, perineal sensation, palpable bladder?
      1. To rule out cauda equina syndrome
3. Labs
   1. Only necessary if concerned for infection, tumor, or rheumatologic cause
      1. CBC, UA, ESR (90-98% Sn for infectious etiology)
   2. Consider post void residual
      1. Can be done with non invasively with Ultrasound
4. Imaging
   1. Plain films
      1. Only necessary if suspect fracture, tumor, or infection
   2. MRI
      1. Only necessary if suspect infection, neoplasm, epidural compression syndromes
      2. Consider for back pain >6-8wks
   3. Ultrasound
      1. Rule-out AAA

Treatment

• Nonspecific Back Pain (musculoskeletal)
  • Instruct to continue daily activities using pain as limiting factor
  • Meds
    • NSAIDs or acetaminophen
      • 1st line therapy
    • Opioids
      • Appropriate for moderate-severe pain but only for limited duration (1-2wks)
    • Muscle relaxants
      • Efficacy appears equal to NSAIDs
      • Diazepam 5-10mg PO q6-8hr OR methocarbamol 1000-1500mg PO QID
    • Steroids (of questionable effectiveness)
      • Prednisone 40-60mg PO qd x 5-10 days
• Sciatica
  • Treatment is the same as for musculoskeletal back pain
  • 80% of pts will ultimately improve without surgery
  • PCP should consider AEDs (gapapentin, titrate slowly) or TCAs (nortriptyline, amytriptyline)
• Spinal stenosis
  • Treatment is the same as for musculoskeletal back pain
• Cauda equine syndrome
  • Immediate Ortho referral for spinal decompression to avoid permanent bowel/bladder injury

See Also

• Back Pain (Red Flags)