Back Pain & Spine (Clinical)

Triage and nonspecific back pain

Three buckets. Nearly all low back pain is benign, so the core skill is sorting. Mechanical or nonspecific pain (most cases) has no neurologic deficit; radicular pain radiates down the leg in a dermatome with a positive straight-leg raise; red-flag pain suggests cancer, infection, fracture or cauda equina. Screen every patient for red flags first, because their absence lets you avoid imaging.

Nonspecific back pain. Acute nonspecific low back pain without red flags needs no imaging in the first 4–6 weeks and usually resolves on its own. Advise staying active and avoiding bed rest. NSAIDs are first-line (acetaminophen adds little benefit); a short course of a skeletal muscle relaxant is another option. Avoid routine opioids, and add heat, exercise or physical therapy as needed.

Inflammatory back pain is different: a young adult with insidious onset, prolonged morning stiffness, improvement with exercise rather than rest, and night pain suggests ankylosing spondylitis (HLA-B27, sacroiliitis).

Red flags and spinal emergencies

Cauda equina syndrome. Compression of the lumbosacral roots below the conus, usually by a large central disc herniation, tumor, abscess or hematoma, causes saddle anesthesia, urinary retention with overflow incontinence, decreased anal tone, and bilateral leg weakness or sciatica with reduced reflexes. Urinary retention is the most sensitive sign, so check a post-void residual. It is a surgical emergency: emergent MRI and decompression prevent permanent bladder, bowel and motor deficits.

Malignancy. Spinal metastases, most often from breast, lung, prostate, thyroid or kidney cancer, are suspected with back pain in a patient over 50, a cancer history, unexplained weight loss, pain that is worse at night or unrelieved by rest, or symptoms beyond 4–6 weeks. Image with MRI and check labs such as CBC, ESR and CRP. If a patient with cancer develops weakness, a sensory level or sphincter dysfunction, give high-dose IV dexamethasone and obtain emergent MRI of the whole spine, followed by radiation or surgical decompression.

Night pain, weight loss and pain unrelieved by rest are the classic cancer red flags.

Spinal infection. Vertebral osteomyelitis, discitis and spinal epidural abscess occur in IV drug users, immunosuppressed patients and after spinal procedures, usually from S. aureus. Expect fever, focal point tenderness and elevated ESR and CRP. The epidural abscess triad is fever, back pain and a neurologic deficit, but the full triad is often absent early. Get an urgent contrast-enhanced MRI and blood cultures, start IV antibiotics that cover MRSA, and decompress surgically when a neurologic deficit is present.

Fracture. An osteoporotic vertebral compression fracture causes sudden focal midline pain after minimal or no trauma in an older adult or a patient on chronic glucocorticoids; plain radiographs are the first test.

Radiculopathy and disc herniation

Sciatica. A herniated disc compresses a nerve root, producing dermatomal pain that shoots below the knee, often with numbness and weakness. A positive straight-leg raise reproduces radicular pain at 30–70° of elevation and is sensitive; a crossed straight-leg raise, with pain in the affected leg when the good leg is lifted, is highly specific for disc herniation. Most herniations are paracentral and compress the traversing (lower) root, so an L4–L5 disc affects L5; a far-lateral herniation compresses the exiting root instead.

Foot drop from an L5 radiculopathy also weakens foot inversion and hip abduction; a common peroneal nerve palsy spares both.

Management. Most disc herniations improve within 4–6 weeks with conservative care: NSAIDs, staying active and physical therapy. Epidural steroid injections give short-term relief. MRI is reserved for red flags or for patients being considered for injection or surgery. Discectomy is indicated for cauda equina syndrome, a progressive or severe motor deficit, or radicular pain refractory to conservative therapy.

Lumbar spinal stenosis

Neurogenic claudication. Degenerative narrowing of the canal by disc bulging, facet hypertrophy and a thickened ligamentum flavum affects older adults. They describe bilateral leg pain, numbness or heaviness on walking and standing that worsens with extension and eases with flexion, such as sitting or leaning on a shopping cart; walking uphill and cycling are tolerated better than walking downhill. Pedal pulses are normal. Treat conservatively with physical therapy and analgesics; for refractory symptoms, confirm with MRI and consider decompressive laminectomy.

The shopping-cart sign, relief when leaning forward on a cart, is classic for spinal stenosis.

Imaging only with a reason

Imaging restraint. Do not image acute low back pain in the first 4–6 weeks without red flags. Degenerative findings such as disc bulges are common in people without pain, so early imaging of nonspecific pain uncovers incidental changes, drives unnecessary procedures and worsens outcomes.

• MRI: suspected cauda equina, infection, malignancy or a progressive neurologic deficit, and persistent radiculopathy when intervention is being considered
• Plain films: suspected fracture after trauma or in osteoporosis or chronic steroid use
• No imaging: acute nonspecific pain without red flags