University of Iowa Family Practice Handbook, Fourth Edition, Chapter 16

Orthopedics: Low Back Pain

1. Overview. Low back pain is the second most common cause of lost work time. Most cases (90%) resolve within 6 weeks, 40% in 2 weeks; 5% of cases of low back pain become chronic in nature.
2. Etiology.
   1. Mechanical causes. Account for up to 98% of cases of back pain.
      1. Disk injury. Herniation of the nucleus pulposus usually occurs posteriorly. May impinge on nerve roots, particularly at the L4-L5-S1 levels. Typically pain increases with coughing, sneezing, riding in a car or trunk flexion and includes radicular symptoms and signs. Associated bowel or urinary abnormalities is a surgical emergency (cauda equina syndrome)
      2. Degenerative changes in facet joints. Result in nerve root impingement at the foramina. Sudden attacks lasting for a few days with symptom-free intervals. Typically pain is worse with trunk extension.
      3. Spondylosis. Spondylosis is defined as degenerative changes in vertebral bodies and disks. This may cause a nerve root impingement.
      4. Spondylolisthesis. Slippage of one vertebra anteriorly in relationship to the vertebral body below it. 80% occur at L5-S1.
      5. Spondylolysis. A defect in the pars interarticularis generally the result of repeated lumbar stress and hyperextension. It generally occurs in the younger patient (18 to mid-twenties) and occurs in 6% of the population. It is much more common in gymnasts. Pain is worse with extension and better with flexion.
      6. Vertebral body fracture. After trauma or spontaneous "wedge" fractures in elderly with osteoporosis or those using steroids (see Chapter 13 for a discussion of osteoporosis-related fractures).
      7. Spinal canal stenosis. Irritation during activity results in pain in one or both extremities while walking (similar pain to claudication). Relieved with rest. Exacerbated with back extension, relieved with flexion. Common in the elderly.
      8. Myofascial or soft-tissue injury or disorder. May have history of trauma, heavy work, or unusual activity.
      9. Arachnoiditis and postoperative scarring.
      10. Children. Under 10 years old: diskitis (see Chapter 12), tumor, AV malformations, and osteomyelitis. Over 10 years old: spondylolisthesis, herniated disks, juvenile kyphosis (Scheuermann’s disease--an osteochondritis that leads to wedging of the vertebrae and kyphotic posture), overuse syndrome, tumor, spondylolysis.
      11. Sacroiliitis. Inflammation of SI joints. Pain exacerbated with pressure on sacroiliac joint (although this is nonspecific for sacroiliitis).
   2. Systemic disorders.
      1. Malignancy
         1. Primary tumors. Multiple myeloma most common.
         2. Metastatic disease. 85% are from the breast, prostate, lung, kidney, and thyroid. Most cause lytic lesions with the exception of prostate and thyroid cancer, which cause sclerotic lesions. About 30% bone loss is required before lytic changes will be visible on radiographs.
      2. Miscellaneous. Osseous, disk, or epidural infection; spondyloarthropathy; metabolic bone disease, including osteoporosis; vascular disorders such as atherosclerosis or vasculitis.
   3. Neurologic causes.
      1. Myelopathy from intrinsic or extrinsic processes
      2. Lumbosacral plexopathy, especially in diabetes
      3. Neuropathy, including mononeuropathy and inflammatory demyelinating diseases
      4. Myopathy, including myositis and metabolic causes
   4. Referred pain, including GI disorders such as pancreatitis and perforated ulcer; GU disorders, including nephrolithiasis, prostatitis, and pyelonephritis; gynecologic disorders, including ectopic pregnancy and pelvic tumors; abdominal aortic aneurysm; or hip disorder.
3. Work-up.
   1. Physical examination.
      1. Standing. Examine for obvious defects. Palpate for tenderness or muscle spasm. Test the mobility of the lumbar spine with flexion, extension, and lateral flexion. Observe the patient’s gait and have the patient walk on toes (foot plantar flexion test S1) and heels (foot dorsiflexion test L5).
      2. With the patient sitting, do straight-leg raising (SLR) test: passive extension of the knee. A positive test is radicular pain (e.g., pain, paresthesias down the leg, not back pain or thigh pain from muscle stretching) at less than 60 degrees. However, straight leg raising is neither sensitive nor specific for disk disease. "Crossover" pain with radicular symptoms in the leg not lifted is very specific for disk disease.
      3. Reflexes. Patellar reflex tests the L4 root; Achilles tendon reflex tests the S1 root (L5-S1 disk). Babinski sign: if present, indicates disorder above the lumbar region such as cord tumor or CVA.
      4. Sensation.
         1. See dermatomal chart (see Figure 23-9) for a description of radicular sensory findings.
         2. Check hip abduction (L5 motor), perianal sensation (S3-5: also controls anal and urethral sphincter tone), hip extension (L5 motor). Saddle anesthesia and decreased anal sphincter tone indicate a surgical emergency.
   2. Laboratory and imaging studies.
      1. Lumbar spine films are not necessary in most patients. Plain films should be obtained if (1) symptoms last more than 6 weeks, (2) there is suspicion or history of malignancy, (3) the patient is using steroids, (4) is over 50 years of age, (5) has a history of trauma, or has neurologic deficits, or (6) is younger than 20 years of age. There is no need to obtain radiographic evaluation for history consistent with muscle strain.
      2. Patients suspected of having infectious or neoplastic causes of low back pain should have an imaging study such as a bone scan, CT, or MRI.
      3. If severe symptoms persist for several weeks despite conservative therapy and disk herniation or another surgically correctable disorder is suspected, then CT or MRI imaging may be useful. Generally, since surgery is not indicated unless pain is present for at least 6 weeks or there are signs of cauda equina syndrome, there no need for these imaging studies unless there is some indication other than pain. Electromyogram and nerve conduction velocity can be used to evaluate suspected nerve root involvement.
      4. Blood tests. Differential CBC with ESR, and biochemical screening (calcium, phosphate, alkaline phosphatase) should be performed when a systemic cause for back pain is suspected.
      5. Immunoelectrophoresis of serum and urine samples. Allows diagnosis of most cases of myeloma (Bence-Jones proteins).
4. Treatment.
   1. Acute back pain (no longer than 6 weeks).
      1. There is no difference in outcome when patients with acute back pain are treated by a family physician, a chiropractor, or an orthopedic surgeon. Therapy by a family physician is the most cost effective.
      2. Regardless of the method of treatment, 40% are better within 1 week, 60% to 85% in 3 weeks, and 90% in 2 months. Negative prognostic factors include more than 3 episodes of back pain, gradual onset of symptoms, and prolonged absence from work.
      3. Bedrest. Should be kept to a minimum and early mobilization encouraged. This is true in both back strain and radicular disease. If symptoms recur or considerable pain develops in relation to a specific activity or level of activity, the patient should temporarily limit that activity for several days but should not cease all activity.
      4. Analgesia. NSAIDs provide pain relief and decrease inflammation but have side effects. Acetaminophen provides analgesia but has no anti-inflammatory properties and may be used with or instead of NSAIDs. Narcotics should be used short term as needed. Muscle relaxants such as cyclobenzaprine or diazepam work mostly by sedating patients and preventing activity. However, they probably have little effect on muscle spasm.
      5. Physical therapy. Although classically several modes have been used to hasten resolution of back pain, most physical therapy modalities have no effect when rigorously tested. Traction, local application of heat, cold, and ultrasound, and corsets have been shown to have no effect. Proper lifting, strengthening, and weight loss may prevent recurrence. Transcutaneous electrical nerve stimulation may provide short-term symptomatic relief but has no proven long-term benefit. Acupuncture may also be of help.
      6. Epidural steroid injections. These have been classically used but a randomized trial shows that there is no benefit.
      7. Rehabilitation exercises. Trunk extensors, abdominal muscles, aerobic conditioning. The main benefit is that they promote early mobilization, which is critical in treating acute back pain. The specific exercise does not matter as much as the mobilization.
      8. Back support belts are ineffective in preventing back pain.
   2. Chronic back pain. Once back pain has been established for more than 1 year, the prognosis is poor. Mild analgesia should be used. Avoid chronic reliance on narcotics if possible (although addiction rates are low with chronic pain). If depression is encountered, it should be treated. Other modalities for chronic pain include tricyclics, carbamazepine and gabapentin. Physical modalities include transcutaneous electrical nerve stimulation or acupuncture with electrical stimulation. Both are effective but for a limited duration of time.
   3. Indications for admission and referral. Cauda equina syndrome (urinary retention, sphincter incontinence, saddle anesthesia), severe neurologic deficits (footdrop, areflexia, gastrocnemius-soleus or quadri-ceps weakness), progressive neurologic deficit, or multiple nerve root involvement.

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See related Provider Topics Back Pain, Bones, Joints and Muscles or Brain and Nervous System.

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