What are the differential diagnoses and management options for lower back pain with radiation down the legs after a slip injury?

Differential Diagnoses for Lower Back Pain with Leg Radiation After Slip Injury

The primary differential diagnosis is lumbar radiculopathy from disc herniation, followed by spinal stenosis, vertebral compression fracture, and less commonly cauda equina syndrome, infection, or malignancy. 1

Key Differential Diagnoses

Most Likely: Radiculopathy from Disc Herniation

• Sciatica (pain radiating below the knee in sciatic nerve distribution) is the hallmark symptom of lumbar radiculopathy and is the most common presentation after traumatic injury with leg radiation 2
• Look for sensory impairment, motor weakness, or diminished deep tendon reflexes in a specific nerve root distribution 2
• Perform straight-leg-raise test: positive if sciatica is reproduced when leg is raised between 30-70 degrees 1, 2
• A positive crossed straight-leg-raise test (reproduction of sciatica when lifting the unaffected leg) is highly specific for nerve root compression 1

Spinal Stenosis

• Presents with neurogenic claudication: leg pain or weakness with walking/standing that is relieved by sitting or spinal flexion 1
• More common in older patients 1
• Symptoms are typically bilateral rather than unilateral 1

Vertebral Compression Fracture

• Suspect in patients with osteoporosis history, chronic steroid use, or significant trauma relative to age 1
• Pain is typically localized to the back without true radicular symptoms 1
• Plain radiography is the appropriate initial imaging for suspected fracture 1

Red Flag Conditions (Require Urgent Evaluation)

Cauda Equina Syndrome:

• New urinary retention or overflow incontinence from sphincter dysfunction 3
• Bilateral lower extremity motor weakness 1
• Saddle anesthesia 1
• Requires immediate MRI and surgical consultation as delayed treatment worsens outcomes 1

Infection (Vertebral Osteomyelitis/Discitis):

• Fever, recent invasive spinal procedure, or IV drug use 3
• Prevalence is only 0.01% in primary care but carries high morbidity if missed 4

Malignancy:

• History of cancer (strongest predictor), age >50, unexplained weight loss 1
• Consider ESR (≥20 mm/h has 78% sensitivity, 67% specificity for cancer) 1
• Prevalence is 0.7% in primary care settings 4

Management Algorithm

Initial Assessment (First 4 Weeks)

Do NOT routinely obtain imaging in the absence of red flags 1

• Most patients with acute radiculopathy improve within the first 4 weeks with conservative management 1
• Routine imaging does not improve outcomes and leads to unnecessary interventions 1
• Imaging identifies many abnormalities that correlate poorly with symptoms 1

Conservative Management:

• NSAIDs have moderate evidence for short-term benefit 3
• Acetaminophen can be used though evidence is limited 5
• Skeletal muscle relaxants (e.g., cyclobenzaprine 5-10 mg) have good evidence for effectiveness, though drowsiness and dry mouth are common side effects 6, 5
• Advise patients to stay active rather than bed rest—maintaining activity is more effective for radicular pain 2, 5
• Heat therapy has good evidence for benefit 5

When to Image (After 4-6 Weeks)

Obtain MRI (preferred over CT) if: 1

• Persistent radicular symptoms after 4-6 weeks of conservative therapy AND patient is a surgical candidate 1
• Severe or progressive neurologic deficits at any time 1
• Any red flag symptoms suggesting cauda equina, infection, or malignancy 1, 3

MRI is preferred because it provides better visualization of soft tissue, vertebral marrow, and spinal canal without ionizing radiation 1

Surgical Referral Indications

Immediate referral (within 2 weeks): 2

• Cauda equina syndrome 1
• Progressive motor deficits 2
• Severe radicular pain unresponsive to conservative measures 2

Referral at 3 months if symptoms persist despite conservative therapy: 2

• Discectomy may be appropriate for persistent radicular symptoms from disc herniation 1, 2
• Epidural steroid injections are an option for persistent radiculopathy 1

Consider referral after 1 year for nonspecific low back pain without clear radiculopathy if conservative measures fail 1, 2

Critical Pitfalls to Avoid

• Do not order imaging in the first 4-6 weeks unless red flags are present—this exposes patients to unnecessary radiation, identifies clinically insignificant findings, and increases healthcare costs without improving outcomes 1, 4
• Do not miss cauda equina syndrome—always ask about urinary retention, bilateral leg weakness, and saddle anesthesia, as delayed diagnosis significantly worsens outcomes 1
• In young women, avoid unnecessary lumbar spine radiographs—gonadal radiation from 2-view lumbar films equals daily chest X-rays for over 1 year 1
• Reassess patients at 1 month if symptoms persist or worsen—earlier reassessment is appropriate for severe pain, functional deficits, older age, or signs of radiculopathy 1