25. | Manual of Rheumatology and Outpatient Orthopedic Disorders (LB Spiral Manuals)

Chapter 18 Low Back Pain

Manual of Rheumatology and Outpatient Orthopedic Disorders

Chapter 18 Low Back Pain

Daniel J. Clauw and John F. Beary, III

Etiology
History
Physical examination
Diagnostic studies
Treatment
Rehabilitation and exercise

Low back pain is an extremely common condition, affecting 80% of persons at some point in their lifetime, which makes this complaint second only to the common cold as a reason for outpatient physician visits . Most episodes of acute low back pain resolve spontaneously, regardless of the type of therapy chosen . However, a small percentage of these acute cases, 5% to 10% in most series, progress to chronic low back pain. It is this latter group of patients that primarily accounts for the enormous amount of disability caused by low back pain, estimated to cost more than $20 billion annually and completely disable more than 2.5 million persons in the United States alone.

Epidemiologic studies have established demographic characteristics and risk factors for the development of low back pain. First episodes of low back pain typically occur between the ages of 20 and 40, with a relatively equal sex ratio. Well-established risk factors for the development of low back pain include heavy manual work, especially when twisting while lifting is involved; poor job satisfaction; exposure to vibration ( especially while driving motor vehicles); and cigarette smoking. A sedentary life-style and pregnancy are possible but unproven risk factors. The emphasis in this chapter is to guide the physician into a directed history and physical examination that will allow differentiation of the common causes of low back pain from the more serious, uncommon causes. Once these salient differences in presentations are understood , it becomes clear that the majority of patients who present with low back pain need no diagnostic tests and will respond to conservative management.

I. Etiology. Any of the components of the lumbosacral process may be responsible, alone or in combination, for low back pain, or pain may be referred to this area from a distant site. The history, physical examination, and diagnostic studies will allow the formation of a differential diagnosis from the list below.

Vertebral body (e.g., metastatic disease, metabolic bone disease, fracture).
Intervertebral disk (e.g., infection).
Joints (e.g., ankylosing spondylitis, osteoarthritis )
1. Apophyseal joints.
2. Sacroiliac joints.
Ligaments
1. Anterior and posterior longitudinal ligaments.
2. Interspinous and supraspinous ligaments.
3. Iliolumbar ligaments.
4. Apophyseal ligaments.
Nerve roots (e.g., herniated nucleus pulposus, spinal stenosis).
Paraspinous musculature (e.g., fibromyalgia, myofascial pain).
Pain from adjacent structures or referred pain
1. Kidney (e.g., pyelonephritis, perinephric abscess, nephrolithiasis).
2. Pelvic structures (e.g., pelvic inflammatory disease, ectopic pregnancy, endometriosis, prostatic disease).
3. Vascular (e.g., aortic aneurysm, mesenteric thrombosis).
4. Intestinal (e.g., diverticulitis).
Malignancy (involving any of the above structures).
Miscellaneous conditions (e.g., sickle cell disease).

II. History. The history is of the utmost importance to obtain associated symptoms and establish a pattern of pain.

Associated symptoms. A thorough review of systems is required to establish concomitant symptoms that would suggest a nonmechanical cause of low back pain.
1. Fevers or chills would raise the possibility of an infectious process.
2. Weight loss, chronic cough, change in bowel habits, night pain, or other constitutional symptoms may suggest an underlying malignancy.
3. Similar pain or morning stiffness in other areas of the body would increase the suspicion that this represents a more generalized rheumatologic condition (e.g., ankylosing spondylitis, psoriatic arthritis, or endocrine disorder , such as hypothyroidism , hyperthyroidism, or hyperparathyroidism).
4. If fatigue or a sleep disturbance is present, the diagnosis of fibromyalgia should be considered .
5. Morning stiffness or back pain that improves with exercise should prompt consideration of a seronegative spondyloarthropathy.
Pain. The quality of pain, its distribution, and modulating factors are helpful in determining etiology.
1. Onset of pain
  1. Sudden onset, particularly if associated with trauma, suggests bony or soft- tissue injury .
  2. Indolent onset suggests a nonmechanical cause.
  3. Episodic or colicky pain suggests an intraabdominal or pelvic etiology.
2. Localization of pain
  1. Localized.
  2. Radicular, suggesting nerve root impingement.
3. Modulating factors
  1. Exercise. Pain that worsens with exercise, especially walking, suggests osteoarthritis or spinal stenosis, whereas morning stiffness and improvement with exercise suggest a seronegative spondyloarthropathy.
  2. Valsalva maneuvers. Radicular pain worsened by coughing or sneezing suggests nerve root impingement.
Neurologic symptoms. The presence of neurologic symptoms should be specifically sought in patients with low back pain. Their presence not only can help delineate the site of the abnormality but also may prompt more rapid intervention.
1. Weakness, numbness, or paresthesias in a dermatomal distribution suggest nerve root impingement (Table 18-1).
  
  Table 18-1. Signs and symptoms of common disk lesions
  1. The most common cause of nerve root impingement in persons between ages 20 and 50 is a herniated nucleus pulposus; this condition is rare under age 20 because the disk is well hydrated and resilient.
  2. Radicular symptoms in persons over age 60 are more likely to be secondary to spinal stenosis resulting from degenerative arthritis.
  3. Be aware that neoplasm or infection that causes expansion or dislocation of any of the elements of the spinal cord can likewise lead to radiculopathy.
2. Bowel or bladder dysfunction suggests the presence of cauda equina syndrome and should prompt emergent investigation.

III. Physical examination. In addition to a general examination, patients with low back pain should be examined for specific abnormalities and undergo provocative maneuvers specifically designed to elicit pain in certain syndromes.

Patient standing
1. Note alignment of the spine, looking for a pelvic tilt that may indicate paravertebral spasm, for loss of normal lumbar lordosis that could indicate either spasm or ankylosis, and for evidence of structural scoliosis.
2. Evaluate gait, station, and posture .
3. Evaluate the patient's ability to flex, hyperextend, rotate, and tilt the spine.
Patient supine
1. Straight leg raising (SLR). Flex each leg at the hip with the knee extended and record the angle at which pain occurs and whether it causes pain to radiate below the knee.
  1. A true positive SLR test, defined as radicular pain radiating below the knee, is a sensitive indicator of nerve root impingement and should be confirmed by extending the knee while the patient is sitting to eliminate malingering.
  2. A crossed SLR test (radicular pain contralateral to the leg being raised) is highly predictive of nerve root compromise.
2. Evaluate hip and knee range of motion to eliminate these areas as a source of pain.
3. Carry out thorough neurologic (see Table 18-1) and vascular examinations.
Patient prone
1. Look for evidence of sciatic notch tenderness, sometimes seen in sciatica.
2. Results of the femoral stretch test (extending the hip) may be positive in L-4 radiculopathy.
3. Palpate bony structures, especially vertebral bodies, for localized tenderness, and examine for presence of trigger points, not only in the low back but also in other areas of the body.

IV. Diagnostic studies

Imaging studies. These studies are not performed until the patient fails a trial of conservative therapy or unless neurologic or constitutional symptoms are present. Because all of these studies have a high incidence of false-positive results, it is imperative that the history and physical examination correlate with the detected abnormality.
1. Plain films should be taken as an initial study in the evaluation of low back pain.
  1. Anteroposterior, lateral, and cone-down views of the lower two interspaces are standard; oblique views will identify subtle spondylolysis but are not routinely necessary.
  2. Flexion and extension views may be obtained to document instability.
2. Bone scintigraphy (bone scan) is useful as a screening study when malignancy (other than multiple myeloma) or infection is suspected.
3. Diskography is performed by injecting dye into the disk space. The incidence of false-positives is high unless symptoms are reproduced during diskogram injection. It is performed primarily when the results of other studies are negative or equivocal .
4. Computed tomography (CT). When used without intradural contrast, CT is the study of choice for delineating the bony structures of the spine (e.g., spinal stenosis). With the addition of intrathecal metrizamide, the sensitivity for detecting neural involvement is enhanced. Pitfalls are that CT does not detect intraspinal pathology (e.g., tumors ) and that the rate of false-positives is high in certain populations, especially older patients.
5. Myelography outlines the dural theca and its contents after injection of a contrast medium into the dural sac. This is a good study to delineate neural compression (it remains the study of choice when metal hardware is present or when arachnoiditis is a consideration) and is still required by many surgeons contemplating intervention. However, myelography is slowly falling from favor because of its side effects and because of improvements in MRI and CT.
6. Magnetic resonance imaging (MRI) is the newest diagnostic modality for the spine. The newer scanners have excellent resolution and can visualize both bony and soft-tissue structures well. MRI is now the study of choice for imaging intraspinal pathology (e.g., tumors). The principal problem with MRI is the high rate of false-positive examinations; up to 30% of asymptomatic persons will have significant abnormalities on this study.
7. Electrodiagnostic testing. Electromyography and nerve conduction studies are sometimes useful in the evaluation of low back pain. With acute nerve entrapment, results of these studies may be normal, but in chronic cases, they are often abnormal and can be used to corroborate findings from imaging studies and so help to eliminate false-positive results.
Radiologic signs
1. Degenerative disk disease. Radiographic abnormalities correlate poorly with symptoms.
  1. Narrowing of the intervertebral disk.
  2. Vacuum phenomenon . Radiolucency in the disk space.
  3. Traction osteophytes.
2. Osteoarthritis
  1. Osteophyte formation.
  2. Facet joint destruction.
  3. Spinal stenosis.
  4. Acquired spondylolisthesis (see section 3.b ).
3. Congenital and developmental defects. Many are asymptomatic and are incidental findings detected on plain radiographs.
  1. Spondylolysis (defect in pars interarticularis) is located in the neck of the Scotty dog on oblique views.
  2. Spondylolisthesis is slippage of one vertebral body on another. It can be a consequence of spondylolysis or acquired conditions.
  3. Transitional vertebrae, with lumbarization of S-1 or sacralization of L-5.
  4. Schmorl's nodes are defects in the vertebral end plates that allow vertical disk herniation.
  5. Scoliosis or kyphosis.
4. Seronegative spondyloarthropathies (ankylosing spondylitis, Reiter's syndrome, psoriatic arthritis, inflammatory bowel disease).
  1. Erosions or sclerosis of the sacroiliac joints are best seen in a Ferguson view of the pelvis, a special view that allows better visualization of the entire length of the joint.
  2. Syndesmophytes. Calcification of ligamentous structures leads to bridging of adjacent vertebral bodies.
5. Neoplasm
  1. Destruction of vertebral body.
  2. Loss of outline of pedicle on anteroposterior films.
  3. Pathologic fracture.
6. Infection should be suspected when destruction of adjacent vertebral end plates is present or bony destruction is accompanied by constitutional symptoms.
7. Miscellaneous
  1. Osteoporosis. Loss in mineralization, compression fractures with characteristic anterior wedging, fish mouth appearance to intervertebral spaces.
  2. Metabolic bone disease.
  3. Sickle cell disease.
Laboratory studies should be performed as indicated by the history and physical examination, age of patient, and chronicity of symptoms.
1. The erythrocyte sedimentation rate and C-reactive protein reflect acute-phase reactants and will usually be elevated in infection, inflammatory joint disease, and metastatic malignancies.
2. Determinations of calcium, phosphorus, and alkaline phosphatase levels screen for metabolic bone diseases.
3. Serum and urine protein immunoelectrophoreses should be performed if multiple myeloma is suspected.

V. Treatment. Because more than 90% of cases of low back pain are self-limited and resolve spontaneously, any treatment algorithm must account for this and avoid laboratory or imaging studies unless constitutional symptoms, weakness, or neurologic dysfunction suggests an urgent problem.

Acute treatment
1. Bed rest. The exact length of bed rest has yet to be established, but recent studies suggest that 2 to 3 days may be adequate for most patients who have no neurologic deficit, slightly longer if a deficit is present. Bed rest for longer than 1 week should generally be avoided because muscle weakness quickly develops.
2. Spinal traction. Although still used frequently, its only therapeutic value is to enforce bed rest, as the amount of traction that must be applied actually to affect pressure within disks is excessive.
3. Pharmacologic treatment
  1. Pain control. Antiinflammatory drugs (e.g., 400 to 800 mg of ibuprofen four times daily or 250 to 500 mg of naproxen twice daily) or analgesics (325 to 650 mg of acetominophen q4h) as needed to control pain. Narcotics should be used with caution if at all.
  2. Muscle relaxants. The mechanism of action of these drugs is not entirely clear, but they are helpful in some patients with acute low back pain. Examples include cyclobenzaprine (10 mg q6h), methocarbamol, and chlorzoxazone. Benzodiazepines such as diazepam may also be used for a limited period (long- term use can decrease the pain threshold).
4. Physical measures
  1. Moist heat.
  2. Massage, ultrasound .
  3. The use of bracing for any extended period is ill-advised, as it may lead to muscle weakness.
Failure of conservative therapy as outlined above, when followed for 4 to 6 weeks, is generally considered an indication to initiate a diagnostic workup and consider surgical intervention. The workup should include plain radiographs of the lumbosacral spine in addition to any other imaging or laboratory studies deemed necessary based on the history and physical examination (see section IV ).
Other treatment modalities
1. Injection of trigger points may be useful if the patient exhibits only a few specific trigger points and local pressure elicits pain in that area or is referred to another area (myofascial pain). Inject these areas with a corticosteroid and local anesthetic (e.g., 40 mg of methylprednisolone and 1 mL of 1% lidocaine without epinephrine).
2. Facet block. The true incidence of pain originating from facet joints is controversial , but injection of these joints in patients demonstrating facet abnormalities on imaging studies should certainly be considered before surgery is contemplated. In some centers, if this initial injection is successful in reducing pain, a more permanent surgical procedure such as rhizotomy may be performed.
3. Transcutaneous electrical nerve stimulator (TENS) therapy is helpful in some cases.
4. Physical therapy. Physical therapists who specialize in back problems (e.g., those involved in back-hardening programs) can make a major contribution to therapeutic success.
Invasive intervention should be contemplated when there is a failure of conservative therapy and there is a radiographically demonstrable anatomic defect that could explain the pain, or when malignancy or infection cannot be excluded with noninvasive techniques. The timing of surgery is critical; it should rarely be performed before 2 months of conservative therapy (except in circumstances noted above that require urgent intervention, such as persistent or worsening neurologic deficit). However, a delay of more than 6 months can lead to the development of a chronic pain syndrome and decrease the likelihood of a good surgical outcome. Types of surgical intervention include the following:
1. Laminectomy or hemilaminectomy. Removal of all or part of the lamina while preserving the apophyseal joints, or in the case of spinal stenosis, trimming the joints to decompress the neural tissues.
2. Laminotomy or hemilaminotomy. An opening is created in the lamina without its being totally removed.
3. Diskectomy. Removal of the nucleus pulposus from the intervertebral space and from any other ectopic location in the epidural space. This can be accomplished in one of the following ways:
  1. Standard surgical approach.
  2. Fiberoptic scope.
4. Spinal fusion. This is performed when instability is present, usually in combination with one of the above operations.
Chronic pain arises from a failure of standard therapy, and patients with this problem are a very difficult group to treat. A subset of this group has fibromyalgia, and these patients are identified by poor sleep, fatigue, and widespread pain and tender points. They may respond well to low doses of tricyclic antidepressants at bedtime (e.g., begin 10 mg of amitriptyline nightly, and escalate the dose by 10 mg once weekly to 50 to 70 mg nightly). In general, however, these patients are best managed by a multidisciplinary approach that combines psychosocial evaluation with one or more of the modalities discussed above.

VI. Rehabilitation and exercise. Flexibility and strengthening exercise is frequently recommended for patients with low back pain, although objective data supporting benefits are sparse. Nonetheless, there are some basic principles regarding rehabilitation in these patients that should be followed. Physical therapists are helpful in instructing patients in these programs.

Postsurgical patients
1. Ambulation is encouraged early, and prolonged sitting is avoided.
2. Lifting should be avoided.
Exercises for low back pain (see Chapter 56) should not be initiated until the acute phase of recovery has been completed and the patient can move freely without pain (approximately 2 weeks). Patients should be instructed to begin with only three to five repetitions of each exercise and proceed slowly.
1. Pelvic tilt. Buttocks are tightened, and the lumbar spine is flattened isometrically.
2. Modified sit-ups. With the patient supine, knees bent and arms at the side, the head and shoulders are lifted off the ground and held for 5 seconds.
3. Knee-chest stretch. Both knees are brought to the chest and held with the arms for 5 seconds; then, one at a time, the knees are extended and the legs are slowly brought to the ground.
4. Back extension. While lying prone with the arms at the sides, lift the chin and shoulders upward and hold for 5 seconds. Then, in the same position, lift one leg at a time upward and hold for 5 seconds.
Other recommendations
1. Weight reduction for obese patients.
2. Aerobic fitness should be increased, whenever possible, with walking, swimming, or other low-impact activities. Before one of these activities is performed, the patient should do stretching exercises to warm up properly.
3. Life-style modifications
  1. Proper lifting techniques. While lifting, the knees should be flexed and the back straight. Twisting while lifting should be avoided.
  2. A firm mattress should be used.
  3. Vocational training may be helpful.

Bibliography

Borenstein DG, Wiesel SW. Low back pain medical diagnosis and comprehensive management. Philadelphia: WB Saunders, 1995.

Frymoyer JW. Back pain and sciatica. N Engl J Med 1988;318(5):281.

Kelsey JL, Golden AL, Mundt DJ. Low back pain/prolapsed lumbar intervertebral disk. Rheum Dis Clin North Am 1990;16(3):699.

Porter RW. Mechanical disorders of the lumbar spine. Ann Med 1989;21(5):361.

Books@Ovid
Copyright 2000 by Lippincott Williams & Wilkins
Stephen A. Paget, M.D., Allan Gibofsky, M.D., J.D. and John F. Beary, III, M.D.
Manual of Rheumatology and Outpatient Orthopedic Disorders

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