Chapter 28. Low Back Pain

In modern society, one would be hard-pressed to overestimate the impact of low back pain (LBP). The costs of this problem, in both human suffering and dollars, are staggering. Although figures vary widely, the lifetime prevalence of LBP is usually quoted as ranging from 60% to 85%, with an annual rate of about 5%. In one recent study, the point prevalence of LBP was estimated to be 30%.

LBP is the number one cause of worker absenteeism in the United States and most other countries in the industrialized world. In the United Kingdom, it is responsible for 12.5% of all sick days. A 1985 study estimated that 14% of the entire population of the United States misses at least 1 workday per year because of LBP. This figure is highest among people involved in manual labor, with low job satisfaction and poor workplace social support. About 2% of workers each year submit claims for disability from LBP, making it the leading cause of expenditures for workers’ compensation.

The chance of someone with LBP returning to work full-time after any significant absence declines exponentially over time. For example, after 6 months of disability, the chance of someone with LBP returning to work full-time is about 50%. After 1 year, this figure plummets to below 20%. After 2 years of missed work, less than 3% of disability patients will ever work regular jobs again. The economic cost of this epidemic is estimated by some experts to exceed $100 billion per year, not to mention the physical, emotional, and psychological tolls it exacts.

Where does all this back pain come from, and who are the people most at risk? Overall, the ratio between men and women is about equal, although younger patients with LBP tend to be disproportionately male, and women report more LBP after the age of 60. For both sexes, the incidence increases with age. Postacchini and colleagues suggested that genetics may play a role in certain types of LBP. In patients with discogenic LBP and those who had undergone surgery for a herniated disk, 35% and 37%, respectively, had at least one first-degree relative with a history of discogenic pain, versus 12% in the control group. In these same two groups, 5% and 10% of patients, respectively, also had at least one family member who had undergone disk surgery, compared to only 1% of patients without complaints of LBP.

Many studies have shown an association between LBP and poor general health. Obesity (and possibly excessive height as well), smoking, low levels of physical activity, and poor strength and flexibility all predispose people to LBP. Interestingly, jobs involving heavy physical labor, and participation in certain sports such as wrestling and gymnastics, have likewise been associated with back pain. Studies have also demonstrated an increased number of sick days taken for other disorders in workers with LBP, and an association between LBP and chronic illness.

Any discussion of LBP must begin with definitions. Chronic LBP is usually defined as LBP that persists longer than 7 to 12 weeks, although some experts define it as LBP that lasts longer than the expected period of healing. As with any form of acute pain, acute LBP represents a nociceptive response to injury. Nociceptors pervade all structures in the spine, so that injury to any of these will be perceived as pain. These structures include the annulus fibrosis, facet joints, paraspinous muscles, periosteum of the vertebral bodies, nerve roots and dorsal root ganglia, ligaments (particularly the anterior and posterior longitudinal ligaments), sacroiliac joints, meninges, and muscle-tendon complexes.

A comprehensive medical history is an indispensable part of the evaluation of any patient presenting with LBP. Although most patients referred to pain specialists present with chronic LBP from nonemergent, progressive medical conditions, a thorough history will rule out causes requiring immediate intervention.

A history of unexplained weight loss and malaise accompanied by back pain that is worse at night requires diagnostic studies to rule out malignancy. New onset of radicular symptoms associated with a rash in a dermatomal distribution may indicate herpes radiculitis. Unexplained fever, chills, night sweats, and a history of intravenous drug abuse or spinal procedures may herald an infection of the meninges or vertebral column. Cauda equina syndrome is a surgical emergency that may be caused by an epidural abscess, hematoma, spinal tumor, or herniated disk. Symptoms include severe back pain with radiculopathy, saddle distribution sensory loss, diminished anal sphincter tone, and urinary retention or incontinence. A history of recent trauma may indicate injury to the facet joints, sacroiliac joints, intervertebral disks, or fracture of the vertebral column. Large quantities of alcohol, caffeine, and smoking may accelerate the development of osteoporosis and predispose patients to spinal fractures. Finally, a ruptured abdominal aortic or iliac artery aneurysm can manifest as severe LBP. Risk factors include diastolic hypertension, chronic obstructive pulmonary disease, male gender, previous vascular procedures, and anticoagulant therapy. A ruptured abdominal aneurysm is a surgical emergency.

Following the general medical history, the physician should focus the interview on the primary complaint. The precipitating event often provides a key clue to the source of LBP. For example, an acute herniated nucleus pulposus (HNP) often causes a person to feel a “pop” in the back, followed shortly thereafter by pain shooting into the foot. The duration and frequency of pain can be important indicators of etiology, as in the case of patients with spondyloarthropathies, who frequently complain of aching LBP of long duration. Conversely, spinal tumors generally cause continuous pain that increases in intensity over time. The location and referral patterns of back pain must be ascertained in a thorough pain history. Pain radiating from the back to the lower limb, or localized exclusively to the lower leg, is strongly suggestive of nerve root irritation. A detailed history that delineates exacerbating and relieving factors can be extremely helpful in distinguishing the myriad sources of LBP. When a herniated disk irritates a nerve root, patients frequently complain of leg pain at rest. When spinal stenosis is responsible, maneuvers that reduce the size of the spinal canal, such as coughing or leaning backward, aggravate the pain. As a general rule, mechanical disorders such as degenerative disk disease and spinal stenosis result in pain that is increased with activity. When inflammatory arthropathies are responsible, pain and function are usually worse in the morning. Regardless of the suspected etiology, accompanying features such as paresthesias, dysethesias, numbness, and changes in bowel and bladder function should always be elicited.

The quality and characterization of pain are integral parts of a good medical interview. Adjectives such as “lancinating” and “shooting” are frequently used to describe pain of neuropathic origin, such as radiculopathy. Words such as “aching” or “pressing” tend to be reserved for nociceptive sources, such as disk disease and facet arthropathy. Finally, the intensity of pain and assessment of disability are essential in determining the effect pain has on a patient’s function and quality of life. Clearly, one’s perception of pain, the limitations it imposes on one’s lifestyle and issues involving secondary gain can have a profound impact on treatment. Several studies have shown that patients with pending litigation tend to have worse outcomes than those who are not entangled with the legal system.

Along similar lines, we inquire about symptoms of depression in all our pain patients. Previous studies have demonstrated an extremely high rate of major depression in patients with chronic pain, with figures ranging from 10% to 85%. In addition to pain management interventions, all patients with significant depressive symptoms are referred to the psychiatry service.

Examination of the lumbar spine begins with inspection. To start, the patient is disrobed and examined standing. The spine is viewed posteriorly, laterally, and anteriorly to check alignment. The back is then examined for any superficial abnormalities, such as redness (which may indicate infection or burns from heating pads), unusual skin markings (which can herald underlying bony or neurologic abnormalities), masses (lipomas may denote spina bifida), skin tags (neurofibromatosis), and skin discoloration (bony pathology). Posture should be viewed from multiple angles, because abnormalities can indicate pathology. Absent lumbar lordosis can be a manifestation of severe paraspinal muscle spasm, whereas an exaggerated lumbar lordosis can indicate weakened abdominal musculature. Unilateral muscle spasm can result in scoliosis. In addition to the low back, a complete examination of the lumbar spine must include inspection of the anterior abdominal wall, inguinal area, buttocks, and sciatic region.

Spinal motion is assessed during forward and lateral flexion, extension, and rotation. The normal range of motion for forward flexion is 40 to 60 degrees; for lateral bending, 15 to 20 degrees; for extension, 20 to 35 degrees; and for axial rotation, 3 to 18 degrees. Squatting tests not only lower extremity muscle strength, but joint function as well. Antalgic gait may be the result of back or leg pain. Other ambulatory abnormalities, such as steppage gait, back-knee gait, or flatfoot gait, can indicate weakness in the lower extremities. Patients with numbness in the soles of their feet may broaden their gait to gain stability.

Manual examination of the lumbar spine includes both bony and soft tissue palpation. Among the three layers of paraspinal muscles, only the most superficial layer, the sacrospinalis system, is palpable. On physical examination, it is not possible to distinguish between the three different muscles that comprise the sacrospinalis system. Posteriorly, the spinous processes are covered by ligaments, not muscles, and are thus easily palpated. Prominent gaps between spinous processes may signify spina bifida. A palpable “step-off” between processes may indicate spondylolisthesis. This is a common finding in patients with spondylolysis. Although vertebral tenderness is a sensitive sign for spinal pathology, it cannot reliably discriminate mechanical from medical disorders. To fully examine the coccyx, a rectal examination must be performed.

Neurologic dysfunction caused by abnormalities in the lumbosacral spine is usually manifested as altered sensation, reflexes, or muscle strength in the lower extremites. Lesions involving the T12 and L1 may manifest as weakness in the iliopsoas muscle, along with decreased sensation in the groin region. The L1 nerve root also innervates a small oblique band in the upper, anterior thigh. Patients with T12 and L1 dyfunction of the nerve roots may have diminished superficial abdominal and cremasteric reflexes. Nerve roots L2 through L4 are responsible for hip flexion and adduction (L2–3), and extension at the knee (L3–4). The sensory innervation of these roots includes branches to the back (L2–3), buttock, anterior thigh, and medial aspect of the lower leg and foot (L3–4). The patellar reflex is mediated through nerves originating from L2 through L4, with the L4 nerve root being the major contributor. The L5 nerve root covers the lateral part of the lower leg and the dorsum of the foot, to include the first two toes. To test the L5 nerve root, have the patient dorsiflex the foot or extend the great toe, or both. The associated reflex for this level is the tibialis posterior. The S1 root provides innervation to the sole, heel, and lateral edge of the foot. Muscle testing for S1 involves plantar flexion of the foot and flexion of the knee. The Achilles tendon reflex, mediated through the gastrocnemius muscle, tests the integrity of S1. The S2 nerve root provides sensation to the posterior and medial parts of the leg; its motor component enables flexion of the toes and plantar flexion of the feet. S3 provides sensation to the medial portion of the buttocks, while S4 and S5 nerves innervate the perirectal area. The coccygeal nerve is the sole innervation for the coccyx. There are no muscle tests to evaluate the nerve roots below S2, because there are no motor fibers from these levels. The bulbocavernous reflex is associated with the S3–4 nerve roots, whereas the anal reflex is mediated by S5 and C1. The addendum at the end of this chapter lists special tests used to diagnose specific causes of low back pain; see also Table 28-1.

Radiologic Imaging

With the advent of new procedures, neuromaging has taken on a greater role in recent years for the diagnosis of LBP. Conventional radiographs are frequently used during an initial evaluation of LBP, especially in patients with known musculoskeletal disease, or when a fracture is suspected. Disorders likely to be picked up on plain x-rays include spondylolisthesis, pars interarticularis defects, scoliosis, ankylosing spondylitis, Scheuermann’s disease, spinal stenosis, and osteoporosis. However, because of the low yield with radiographs, their utility in patients with LBP is controversial.

Magnetic resonance imaging (MRI) is the diagnostic test of choice for evaluating patients with radiculopathy. Other disorders in which MRI is the preferred imaging tool include syringomyelia, intramedullary tumors of the spinal cord, spinal cord infarction, traumatic injury, and multiple sclerosis. In a study by Jensen et al. published in the New England Journal of Medicine, only 36% of individuals without LBP were found to have normal intervertebral disks on MRI scans of their lumbar spine.

The strength of computed tomography (CT) in evaluating patients with LBP lies not in its resolution, but its ability to define spatial relationships between anatomic structures. As such, CT is helpful in patients with spinal stenosis, spinal infections, primary metastatic tumors of the spine, and spinal cord injuries. Because CT provides better images of bone than does MRI, it is preferred for patients with suspected bony abnormalities. Frequently, CT is used in conjunction with myelograms for the evaluation of radiculopathy, and following discography to better delineate disk disease.

Radionuclide bone scanning is the procedure of choice for detecting a variety of bone disorders. Bone scanning is the primary modality used to diagnose and follow skeletal metastases. Whereas osteomyelitis may not be detectable radiographically for more than a week after onset, a bone scan usually shows areas of enhancement within hours of onset. Other indications for bone scanning include occult vertebral fractures, bone disease associated with metabolic disorders, and spondyloarthropathies.

LBP is a symptom, not a disease. The incidence of LBP disability has tended to increase over the years, but the overall prevalence has remained remarkably steady. In spite of the wide variety of disorders that may present with LBP, in the large majority of cases no definitive diagnosis is ever given. Fortunately, most cases (80%–90%) resolve within 6 weeks with or without treatment. Table 28-2 lists the most common causes of chronic LBP by diagnosis.

Infections of the Lumbosacral Spine

Infectious causes of LBP include vertebral osteomyelitis, epidural abscess, and discitis. Vertebral osteomyelitis accounts for between 2% and 4% of all cases of osteomyelitis, with males being affected more than females, and the elderly more than young people. In descending order, the most common sources of infection are the genitourinary system, skin, respiratory tract, and spine surgery. Risk factors include intravenous drug abuse, immune suppression, and rectosigmoid disease. Although vertebral osteomyelitis may sometimes begin abruptly, more often the presentation is insidious. Back pain typically is described as sharp, persistent, and exacerbated with movement. Fever may be minimal or absent. On physical examination, there is usually marked tenderness over the affected vertebra, guarding, and paraspinal muscle spasm. Treatment involves antibiotics and immobilization.

Because of its poor blood supply, most cases of discitis either are iatrogenic or occur secondary to direct spread from an infected vertebra. Classically, patients report the onset of intense, spasmodic pain appearing 1 to 2 weeks after spine instrumentation. Fever is usually absent. In patients without previous surgery, the diagnosis may takes months or even years to make. Pain from discitis may be referred into the groin, flanks, hips, abdomen, or lower extremities. It usually is exacerbated by movement and relieved by rest. In one study, 3 of 13 patients with discitis had neurologic deficits at diagnosis. Physical examination of the spine reveals localized tenderness and restricted range of motion. Treatment is supportive, with antibiotics and pain medication being the mainstays of therapy. Although the treatment course is usually prolonged, surgical debridement is rarely necessary. Some studies have shown discitis to be associated with an increased incidence of chronic LBP.

Epidural abscesses account for approximately 1 in 10,000 hospital admissions. Predisposing factors include intravenous drug abuse, cirrhosis, and alcoholism, with men being affected at a greater rate than women. Although severe back pain that follows a spinal procedure should arouse suspicion, spinal instrumentation is usually not the cause of an epidural abscess. In a review of 39 cases of spinal epidural abscess over 27 years at Massachusetts General Hospital, only one was secondary to epidural placement.

The four cardinal signs of an epidural abscess are back pain, tenderness, leukocytosis, and fever. Interestingly, back pain is not universal. If left untreated, symptoms progress over a period of days or even months. Generally, the order of progression proceeds from localized back pain to radicular pain, weakness, incontinence, and paralysis. An epidural abscess is a surgical emergency. In one study, whereas patients diagnosed within 36 hours of the onset of symptoms had minimal residual weakness, no recovery was observed in patients paralyzed longer than 48 hours. Other infections that can result in back pain include herpes zoster, Lyme disease, and infectious sacroiliitis.

Vertebral Fractures and Spondylolysis

As the life expectancy of the U.S. population has continued to increase, so too has the incidence of spinal fractures. There are two main reasons for this: increasing disability with age, and a higher incidence of osteoporosis. In clinical practice, only 30% of vertebral fractures come to the attention of physicians, primarily because lack of severe back pain in many patients does not trigger obtaining radiologic studies. However, the prevalence of radiographically demonstrated vertebral deformities rises from 5% of individuals between the ages of 50–54, to 50% in women over 80 years. The most common locations for vertebral fractures are at the thoracolumbar junction, the mid-thoracic spine (T7–8), and the lumbar vertebral column. The prevalence of spinal fractures is highest in white women, owing the their increased incidence of osteoporosis. Aside from the increased propensity for vertebral fractures, some experts believe osteoporosis in and of itself can cause spinal pain. Aside from the increased propensity for vertebral fractures, some experts believe osteoporosis in and of itself can cause spinal pain.

The patient with a vertebral fracture typically presents with acute pain overlying the fracture site. For sacral fractures, pain may radiate into the buttocks or leg. The precise incidence of neurologic deficit depends on the extent, type and location of injury, but is usually cited as being greater than 30%. One way of distinguishing patients with spinal fractures from those with other types of fractures is the fact that more than half of all patients with severe vertebral fractures go on to develop chronic pain. Physical examination of the patient with a vertebral fracture(s) usually reveals marked tenderness on palpation. In patients with lumbar fractures who develop radiculopathy, straight leg raising tests may be positive.

Exercise programs for elderly patients suffering from spinal fractures have been shown to increase bone density, decrease the use of analgesics, and improve quality of life. Since patients with vertebral fractures are at increased risk to develop hip and other fractures, walking programs, fall-prevention courses and even Tai Chi may be beneficial. In most patients with isolated spinal fractures, non-steroidal anti-inflammatory drugs and/or short-acting opiods are sufficient for pain relief. In those with constant pain, sustained release opioids may be necessary. For patients whose main symptoms are consistent with radiculopathy, an epidural steroid injection(s) or trial with neuropathic pain medications may be a worthwhile endeavor. Two treatments that have been shown to both reduce subsequent fractures and provide analgesia for fracture patients are bisphosphonates and salmon calcitonin. In patients with focal pain and limited spinal fractures who do not respond to conservative measures, vertebroplasty, which involves the injection of an actylic polymer into a partially collapsed vertebra, or kyphoplasty should be considered. Finally, surgical intervention may be necessary in patients with unrelenting pain, spinal instability, or worsening neurologic deficit. Physical examination reveals marked tenderness on palpation. In most patients, analgesics and bed rest are sufficient treatment. In those who do not respond to conservative measures, vertebroplasty or surgery may be indicated.

One interesting type of vertebral fracture is spondylolysis, also known as pars interarticularis. For the white adult population, the incidence of spondylolysis has been reported to range between 3% and 6%. There is general agreement that most pars defects occur during childhood, with the large majority of cases being asymptomatic. Risk factors for pars fractures include spondylolisthesis, involvement in sports, and genetics. In active adolescents, spondylolysis can be a significant cause of LBP.

Patients with pars interarticularis usually present with focal LBP, although radiation into the buttock or thigh can occur. This pain may be increased during activities that require extension or rotation of the spine. On physical examination, many patients are noted to have a hyperlordotic posture with tight hamstrings. Diagnosis can be confirmed with plain radiographs, CT, or MRI.

The treatment of patients with symptomatic spondylolysis includes analgesics, bracing, cessation of sports, hamstring stretching, and strengthening of the abdominal muscles. In patients who require further pain management, pars injections may be helpful. In some cases, surgery may be necessary.

Metastatic Spinal Tumors

Bone is the third most common location of tumor metastases after the lungs and liver. In patients with metastatic cancer, tumor invades bone in 60% to 84% of cases, with the vertebral column and pelvis being the most frequently affected sites. In one study, 39% of all skeletal metastases were to the spine. The pain associated with spinal metastases develops slowly over weeks or months, gradually becoming more intense. Frequently, it can be localized to the involved vertebral bodies. Patients typically characterize it as a dull but constant pain. Aggravating factors may include weight bearing, activity, and nighttime, when the patient is trying to sleep. Besides back pain, other signs of spinal metastases include fever, chills, weight loss, and generalized fatigue. Pain treatment includes nonsteroidal anti-inflammatory drugs (NSAIDs), neuropathic pain medications, opioids, orthotics, and activity modification. In patients with neurologic deficits, surgical decompression may be necessary. As an adjunct to conventional modalities, chemotherapy, hormone treatment, corticosteroids, bisphosphonates, salmon calcitonin, radioisotopes, and radiotherapy can be helpful.

Spinal Stenosis

Technically, the term spinal stenosis can refer to central canal narrowing, lateral recess stenosis, or foraminal narrowing. The typical presentation of someone with spinal stenosis is an elderly person with axial low back and leg pain brought on by walking, especially down stairs or hills. Frequently, this pain is bilateral and radiates into the ankles. In contrast to patients with vascular claudication, whose symptoms take longer to resolve, those with spinal stenosis find that cessation of walking usually brings immediate relief. Because lumbar extension narrows the spinal canal, patients are often seen bending forward to obtain relief. Numbness and weakness may be present, with sensory complaints usually following a stocking-like distribution.

In contrast to patients with central spinal stenosis, those with lateral recess stenosis or foraminal narrowing tend to have dermatomal symptoms that relate to the irritation of an exiting nerve root(s). Symptoms may be sensory, motor, or both. Sensory complaints are more common than motor dysfunction because of the more peripheral location of sensory fibers in the cauda equina.

The most common causes of spinal stenosis are broad-based disk bulges, facet or ligamentum flavum hypertrophy, and osteophytes. In addition, foraminal narrowing can occur secondary to spondylolisthesis or loss of disk height. The diagnosis of spinal stenosis is usually made by MRI or CT scan.

Most patients with spinal stenosis have only mild to moderate limitation of function and can be treated conservatively. Some noninvasive therapies include lifestyle modification, exercise programs, and pharmacologic treatment with NSAIDs, neuropathic medications, and opioids. In a review of published studies evaluating bed rest for acute LBP and sciatica, Hagen and colleagues found that compared with advice to stay active, bed rest at best has no effect, and at worst may have harmful effects. For the acute exacerbation of radicular symptoms, translaminar epidural corticosteroid injections often provide good pain relief. In patients with foraminal narrowing, the transforaminal approach enables the clinician to deposit corticosteroids directly into the area of pathology. For patients with severe symptoms that are unresponsive to conservative treatment, surgical decompression may be required (Table 28-3).

Herniated Disc

A herniated disc, defined as the herniation of the nucleus pulposus (HNP) through the annulus fibrosis, is the most common cause of LBP, accounting for more than one third of cases. Statistically, herniated discs are more likely to occur in the morning, when the disk height is greatest and the compressive forces are increased. In more than 95% of cases, either the L4-5 or L5-S1 disc is affected. There also may be a genetic predisposition for disc herniation. The most common age for disc rupture is during the third and fourth decades of life.

Although the classic picture of an HNP is LBP accompanied by radicular symptoms, in reality less than half of all patients with disc herniations develop true sciatica. Sometimes, radicular pain develops years after an HNP. Clinically, patients may complain of a sharp, lancinating pain radiating down the leg in a dermatomal distribution. Maneuvers associated with an elevation of intrathecal pressure, such as coughing, sneezing, or prolonged sitting, usually aggravate this pain. On physical examination, sensory loss, muscle weakness, or diminished reflexes in the distribution of the affected nerve root may be present. The straight-leg raising test, although highly sensitive, is relatively nonspecific. Conversely, the crossed straight-leg raising test is very specific but poorly sensitive. In severe cases, bowel, bladder, or sexual disturbances may be present. The diagnosis of HNP is generally made by CT, MRI, or myelography. Electromyographic (EMG) findings can be helpful in patients with nerve root impingement.

In most cases, nonoperative treatment is sufficient for pain arising from a herniated disc. Conservative measures that may provide symptomatic relief include controlled exercise therapy, NSAIDs, and, in patients with radicular symptoms, neuropathic medications. Although spinal manipulation and traction may be beneficial in patients with acute axial LBP, there is scant evidence for their routine use in patients with radicular pain. In patients with the acute onset or exacerbation of sciatica, epidural corticosteroid injections can provide pain relief.

Over the past few years, numerous percutaneous techniques have been developed to excise portions of herniated discs without performing an open surgical procedure. Chemonucleolysis by injection of chymopapain into the nucleus pulposus was first described more than 30 years ago, and remains popular in Europe. In clinical studies, this technique has been consistently found to provide better relief than conservative treatment, but less certain results than discectomy. Newer, percutaneous techniques include laser discectomy, arthroscopic microdiscectomy, endoscopic discectomy and nucleoplasty. However, none of these treatments directly removes the portion of nuclear material that has extruded through an annular defect. This may explain their inferior results when compared with conventional surgery. In patients who do not respond to conservative treatments, lumbar discectomy can provide relief in approximately 75% of cases (Table 28-4).

Sacroiliac Joint Pain

The sacroiliac joint is a large (average surface area is 17.5 cm2 in adults), auricular-shaped, diarthrodial joint connecting the sacral spine to the iliac bones. The function of the sacroiliac joint is to dissipate the load of the upper trunk as it is transmitted to the lower extremities. As a cause of chronic LBP, sacroiliac joint dysfunction is estimated to affect between 15% and 30% of patients. Typically, patients describe a history of pain after falling, lifting and turning, or bracing themselves with their legs during a motor vehicle accident. Mechanistically, the typical injury pattern has been described as “an axial load coupled with abrupt rotation.” Patients may describe an aching, usually unilateral, low back or buttock pain that radiates into the groin or thigh area. Prolonged sitting, standing, or bending exacerbates pain. One disorder that is associated with a high incidence of sacroiliac joint pathology is ankylosing spondylitis. Pregnancy, because of the increased axial load, exaggerated lordotic posture, and hormonal-induced ligamentous flexibility, may also precipitate sacroiliac joint pain. Although infection and tumor can cause sacroiliac joint pain, these etiologies are rare.

On physical examination, the most common finding in patients with sacroiliac joint pain is tenderness overlying the joints. Patients with sacroiliac joint arthropathy have also been described as having a higher incidence of leg length discrepancy, pelvic obliquity, and scoliosis. Numerous physical tests have been described as tools to aid in the diagnosis of sacroiliac joint pain, with two of the most common being Patrick’s test and Gaenslen’s test. However, a study by Dreyfuss and colleagues found that there are no historical or physical examination features that can reliably be used to diagnosis sacroiliac joint pathology. Radiologic studies, such as CT and bone scans, have similarly been shown to be unreliable. As such, the only way to make a definitive diagnosis of sacroiliac joint pain is with diagnostic joint injections, which should be performed with radiologic guidance.

Treatment of sacroiliac joint pain can be a formative task for pain physicians. Pharmacotherapy with medications such as NSAIDs and tricyclic antidepressants can provide relief in some patients, although the benefits are limited. In patients with leg length discrepancies, shoe inserts can result in relief of symptoms by equalizing the pressure across the pelvis. Spinal manipulation has been used for years to provide relief to patients with sacroiliac joint pain, although research is limited. EMG studies have demonstrated muscular abnormalities in patients with sacroiliac joint dysfunction, which have formed the basis for exercise treatment. Two studies have provided preliminary evidence that prolotherapy can be helpful in patients with degenerative joint disease, although none specifically addressed sacroiliac joint pain. For acute pain, noninvasive modalities such as transcutaneous electrical nerve stimulation (TENS), heat and ice packs have been advocated. Perhaps the mainstay of treatment for sacroiliac pain is sacroiliac joint injections with corticosteroids and local anesthetic, which should always be accompanied by physical therapy. Personally, the authors have found that radiofrequency denervation of the L4 and L5 dorsal rami, and lateral branches of S1 to S3, which innervate the sacroiliac joint, can provide long-term relief in patients who respond to diagnostic nerve blocks.

Diskogenic Pain

Pain originating from the intervertebral discs is estimated to affect approximately 39% of patients with chronic LBP. The rationale behind discogenic pain is that as internal disc disruption destroys annular lamellae, the remaining lamellae can no longer bear the load that occurs during normal activities. As the stress on the disc increases, the mechanical threshold required to produce nociception is surpassed. The disc may then become chemically sensitized.

Patients with discogenic pain generally complain of the gradual onset of aching LBP that can extend into the buttock, hip, groin, or even a lower limb. This pain is frequently characterized as being exacerbated by prolonged sitting or bending forward, although a study by Schwarzer and colleagues found no clinical features that could reliably distinguish patients with diskogenic pain from those with other sources of LBP. Physical examination reveals an absence of focal neurologic deficits. As sole therapy, the pain relief that accompanies sacroiliac joint corticosteroid injection tends to be short-lived. In patients who respond to diagnostic blocks with local anesthetic, radiofequency denervation of the L4 and L5 dorsal rami and S1–3 lateral branches which innervate the sacroiliac joint, has been shown to provide long-term pain relief. A post-diskography CT scan can provide additional information regarding anatomic abnormalities.

Treatment of diskogenic pain usually begins with conservative therapy, including NSAIDs, weight loss, and physical therapy. In patients with one- or two-level disc disease, intradiskal electrothermal therapy (IDET) has been shown in uncontrolled studies to provide moderate pain relief. Although MRI and CT scans can indicate degenerative disc disease, the diagnois of discogenic pain is best made by provocative discography. False-positive discography is most likely to occur in patients with abnormal psychometric testing, multiple somatic complaints, and previous back surgery. In addition to enhancing sensitivity, obtaining a post-discography CT scan can provide additional information regarding anatomic abnormalities. In patients who have failed or who are not candidates for invasive therapy, opioids may be of benefit.

Facet Arthropathy

First described by Goldthwait in 1911, pain arising from the lumbar zygapophysial (LZ; facet) joints is frequently quoted to affect 15% to 40% of LBP sufferers, although estimates range from as low as 8% to as high as 94%. The LZ joints are paired, true synovial joints that connect adjacent vertebrae posterolaterally. The function of the LZ joints is to limit rotation and assist the intervertebral disk in resisting compressive forces during lordotic postures, so that maximal stress on the LZ joints occurs during lumbar extension and rotation. The load borne by these joints varies between 3% and 25% of the axial load, increasing during disc space narrowing and facet arthritis. During prolonged standing in a lordotic posture, 16% of the axial load is assumed by the facet joints. In patients with lumbar spondylosis, 70% of the compressive load can be transmitted to the joints. Some of the etiologies for facet arthropathy include microtrauma, capsular tears, synovial inflammation and impingement, chondromalacia, microhemorrhage, and meniscoid entrapment. When facet pain is caused by osteoarthritis, morning stiffness may be present. Some studies have found the incidence of facet joint disorders to be more common in women than in men.

Patients with lumbar facet disease typically present with the gradual onset of deep, achy LBP that may be referred into the groin, hip, buttock, or thigh. On physical examination, pain may be aggravated by maneuvers that increase the load borne by the LZ joints, such as hyperextension and rotation of the spine. On palpation of the back, tenderness in the paraspinous region(s) can often be elicited. CT or MRI scan may reveal hypertrophy of the facet joints. However, numerous studies have demonstrated that the only way to definitively identify the LZ joints as pain generators is to perform diagnostic local anesthetic injections under fluoroscopic guidance into either the facet joints themselves or the medial branches that innervate them. For each facet joint, innervation is derived from the medial branch of the primary dorsal ramus at the level of the joint and one level above it. In those patients who obtain significant pain relief from diagnostic nerve blocks, radiofrequency denervation has been demonstrated to provide long-term relief. Some authors have advocated confirmatory blocks before radiofrequency neurotomy.

Myofascial Pain

Myofascial pain is a common cause of LBP, with one study finding its prevalence to be almost 20%, second only to herniated discs. In addition, some studies have found LBP to be associated with elevated levels of paraspinal muscle tension. Myofascial LBP often presents as a deep, achy pain that is aggravated by activity and position changes. It may be localized to the low back, or radiate into the buttock, sacrum, thigh, abdominal wall, or even calf, depending on the affected muscle(s). Pain-induced weakness or paresthesias, or both, may be present but are nondermatomal in distribution. On physical examination, a tender, taut band of muscle may be noted (trigger point) that when palpated results in a characteristic referral pattern. Deep, traverse “snapping” palpation or needle insertion often elicits the characteristic local twitch response.

The treatment of myofascial LBP is conservative. Some of the therapies used for myofascial pain include ischemic compression massage, the so-called spray-and-stretch technique, iontophoresis, and physical therapy. A large, randomized controlled trial compared osteopathic manipulation with conventional noninvasive therapy in patients with axial LBP of less than 6 months’ duration. The osteopathic treatment group required less pain medication than the conventional treatment group, but had similar outcomes. When trigger points are identified, trigger point injections using local anesthetic can be helpful. A recent, randomized, double-blind study in patients with chronic LBP found injections with botulinum toxin A to be an effective treatment. When myofascial pain is associated with other pathology of the lumbar spine as is often the case, these problems need to be treated as well.

Piriformis Syndrome

The piriformis is a flat, pyramidal muscle extending from the anterior sacrum, greater sciatic foramen, and sacrotuberous ligament to the greater trochanter of the femur. The major function of the piriformis is to abduct and externally rotate the femur. The possibility that sciatic symptoms may stem from the piriformis muscle dates back to 1928, when Yeoman examined the relationship of the sacroiliac joint, sciatic nerve, and piriformis muscle. Although six anatomic variations between the sciatic nerve and piriformis muscle have been described, in the large majority of cases the sciatic nerve passes anterior to the muscle. Any process that causes the piriformis to spasm or contract inappropriately, or less frequently, results in muscle hypertrophy and sciatic nerve impingement, can lead to piriformis syndrome.

The typical presentation of piriformis syndrome is buttock pain or sciatica, or both, exacerbated by activities that necessitate hip adduction and internal rotation, such as cross-country skiing or prolonged sitting. Pain that accompanies bowel movements may be present and, for women, dyspareunia. Physical examination may reveal tenderness in the buttock extending from the lateral border of the sciatic foramen to the greater trochanter. Both pelvic and rectal examinations may reproduce the pain pattern. Pain is also elicited during resistance to hip flexion, adduction, and internal rotation (Freiberg’s sign). The neurologic examination is usually nonfocal, with most patients having a negative straight-leg raising test. Although CT, MRI, and electrodiagnostic studies may be helpful, by themselves these tests are insufficient to make the diagnosis.

For most patients with piriformis syndrome, conservative treatment is sufficient. This includes physical therapy and correction of leg length discrepancies, pelvic obliquity, abnormalities in gait or posture mechanics, and associated back or leg problems. Medications such as NSAIDs and muscle relaxants can sometimes be helpful. Other treatments that have been advocated include transrectal massage, vapocoolant spray coupled with soft-tissue stretching maneuvers, and TENS therapy. When conservative treatment fails, injection of the piriformis with local anesthetic and corticosteroids can relieve muscle spasm and pain. This treatment should be done using either a nerve stimulator to locate the sciatic nerve or fluoroscopy with contrast. In instances in which relief is short-term, piriformis injections can be repeated with botulinum toxin. In rare instances, surgical sectioning of the piriformis muscle may be necessary.

One disorder that is easily mistaken for piriformis syndrome is ischiogluteal bursitis. Patients with ischiogluteal bursitis usually complain of severe pain in the center of the buttock, which is worse with sitting or walking. This pain may radiate into the thigh, but rarely extends below the knee. Tests involving motion at the hip joint, such as straight-leg raising and Patrick’s tests, are often positive. Pressure applied on the lateral rectal wall during a digital rectal examination can elicit excruciating pain. Conservative treatment includes NSAIDs and soft pillows or so-called doughnuts for sitting. For patients with severe pain, bursa injections performed with corticosteroids and local anesthetic are indicated.

Failed Back Surgery Syndrome

The definition of failed back surgery syndrome (FBSS) is the persistence or development of low back or leg pain following surgery on the lumbosacral spine. Two statistics highlight the magnitude of so-called failed back syndrome as a pain problem in the United States. First, approximately 300,000 lumbosacral spine procedures are performed each year in the United States as a treatment for chronic LBP. Secondly, depending on the definition of failure, the incidence of FBSS can be as high as 60%.

The reasons why patients continue to have pain following spine surgery can be broadly categorized as follows: (1) poor patient selection (e.g., patients with a somatoform disorder or who are malingering); (2) surgery was not indicated in the first place or the patient underwent the wrong procedure (e.g., a patient with discogenic pain who underwent a laminectomy); (3) clear indication for surgery, but the procedure did not correct the original problem; (4) complication from surgery (e.g., discitis, pseudomeningocele, or a pars defect); (5) recurrent disc herniation; (6) secondary instability or degenerative changes occurring as a consequence of surgery (e.g., discogenic pain or sacroiliac joint pain developing at the level immediate below a spinal fusion, spondylolisthesis following laminectomy, or pain that develops over the site of a donor graft); (7) persistent or established neural injury (e.g., arachnoiditis or epidural scarring); and (8) an intercurrent diagnosis, such as cancer.

The workup of patients with FBSS begins with a detailed history and physical examination. Of particular importance is determining whether the patient’s pain is of the same character and quality as before the surgery, or represents a new symptom that has arisen. For instance, a new pain complaint might indicate a surgical complication. Equally crucial is determining whether or not, and for how long, the patient experienced a pain-free interval. The three most common scenarios are as follows:

• 1. No relief or the worsening of pain shortly after surgery. This category includes a retained disc fragment, failure to remove the offending disc, and certain iatrogenic infections.
• 2. Initial relief followed shortly thereafter by pain, numbness, or weakness. Examples of this group of disorders are arachnoiditis, epidural fibrosis, and battered-root syndrome with perineural scarring.
• 3. Excellent relief after the surgery followed by development of pain months or years later. This group includes a recurrent disc at the same or different level, pseudoarthrosis, and lumbar instability.

Overall, the most frequent causes of pain in patients with FBSS syndrome are recurrent disc herniation, spinal stenosis, epidural scarring, and arachnoiditis (Table 28-5). Table 28-5 lists the most frequent diagnoses conferred at one pain management center in patients with failed back surgery syndrome.

After obtaining a detailed history, the physician should arrive at a reasonable differential diagnosis. At this point, diagnostic studies are usually necessary. If a recurrent herniated disc or spinal stenosis is suspected, an MRI scan is indicated. Because scar tissue is relatively vascular, a gadolinium-enhanced MRI or CT scan is usually necessary to detect epidural fibrosis. This diagnosis can be confirmed with epidural mapping by the injection of contrast media through the caudal canal. In patients with epidural fibrosis, a filling defect is present. When arachnoiditis is suspected, myelography is the diagnostic imaging study of choice. Additional accuracy can be obtained when a myelogram is followed by CT. For osteomyelitis, bone scanning is the preferred test.

The treatment of FBSS is aimed at the underlying cause. Depending on the diagnosis, nerve blocks, including epidural corticosteroid injections, sacroiliac joint blocks, and facet blocks, can sometimes be of benefit. In patients with radicular symptoms, neuropathic pain medications may provide relief. Some clinicians report good results with epidural lysis of adhesions (i.e. Racz procedure) in FBSS patients with epidural fibrosis, although in our experience the analgesia conferred by this procedure tends to be short-lived. Causes of FBSS that may amenable to surgery include a recurrent disk herniation, postlaminectomy instability, recurrent spinal stenosis, nonunion, and a host of surgical complications. However, in a study by North and colleagues that followed 102 patients who underwent repeat back surgery, only 34% had a successful outcome. In patients who do not respond to nerve blocks, repeat surgery, or other medications, opioids are indicated. Finally, spinal cord stimulation may be of benefit for patients with FBSS who have intractable pain, especially those for whom leg pain is the predominant complaint.

Rare Causes

In addition to the usual causes of LBP, the astute clinician must also consider the unusual. Because of their effects on the musculoskeletal system, a host of different metabolic and endocrine disorders can result in LBP, including hyperthyroidism, hyperparathyroidism, and Cushing’s disease. For similar reasons, virtually any rheumatologic disorder can present as LBP. Visceral pain emanating from internal organs can be referred to the back secondary to convergence in the spinal cord. These sources of visceral pain include genitourinary organs, the kidneys, gallbladder, bowel, and liver. Vascular disease can manifest as LBP, which if not detected, can be catastrophic. Not only is the spine the site of metastatic tumors, but primary tumors may originate there as well. In some patients, hematologic disorders such as mastocytosis and hemoglobinopathies can lead to low back pain, as can diseases such as sarcoidosis, Paget’s disease and infectious endocarditis. Finally, psychiatric and functional disorders can manifest as chronic back pain, which can be extremely difficult to treat.

Bow String Sign

The patient is seated with the body bent forward and knee flexed to 70 degrees, a position that lengthens the course of the sciatic nerve. The examiner then applies pressure on the sciatic nerve by pressing the fingers into the popliteal fossa. An increase in leg pain signifies a radiculopathy.

Brudzinski’s Test

With the patient supine, the head is passively flexed to the chest. Reproduction of the patient’s leg pain signifies nerve root irritation.

Kernig’s Test

The patient lies supine with the hip flexed 90 degrees. The patient is then asked to extend the knee. Back pain may be a sign of nerve root irritation.

Lasegue’s Test

The patient lies supine with the hip flexed 90 degrees. The patient is then asked to slowly extend his knee. A positive test occurs with the elicitation of sciatic pain.

Milgram’s Test

The patient, lying supine, is asked to elevate both extended legs approximately 2 inches off the examining table. If the patient can hold this position for 30 seconds without pain, it aids the examiner in eliminating intrathecal pathology as a cause of pain. If the patient experiences pain during this maneuver or cannot hold the position, intrathecal pathology, such as a herniated disk, must not be ruled out.

Naffziger’s Test

The examiner gently compresses the patient’s jugular veins for about 10 seconds until the face begins to flush. The patient is then asked to cough, causing an increase in intrathecal pressure. Pain may indicate intrathecal pathology.

Stoop Test

The patient is asked to walk briskly for several minutes. When back, posterior thigh, and leg pain appear, the patient sits and flexes forward. Disappearance of the pain suggest neurogenic claudication. During this time, reflexes may be diminished.

Straight-Leg Raising Test

With the patient lying supine, the affected leg is raised with the knee fully extended. A positive test reproduces the patient’s radicular pain at between 30 and 70 degrees of elevation. Straight-leg raising is designed to stretch the affected nerve roots and dura and is especially useful for detecting radiculopathy involving the L4, L5, and S1 nerve roots. A variant of this test is the bilateral straight leg raising test, whereby the patient is asked to raise both legs simultaneously. Movement between 0 and 70 degrees tests the integrity of the sacroiliac joint. Movement above a 70-degree angle places stress on structures of the lumbar spine.

Valsalva’s Test

The patient is asked to bear down, as during a bowel movement or coughing, thus increasing intrathecal pressure. A positive test suggests intrathecal pathology.

Well Straight-Leg Raising Test (Fajersztajn’s Test)

When the straight-leg raising test is performed on the asymptomatic leg, pain may be reproduced on the affected side. A positive test may indicate a large disk herniation.

Cranial Shear Test

With the patient prone and the pelvis immobilized through the hip, pressure is applied to the coccygeal end of the sacrum. This test may be positive in patients with sacroiliac joint pain.

Extension Test

The patient is placed in the prone position, with one hand of the examiner on the thigh of the affected side and other hand over the opposite iliac crest. Downward pressure is exerted on the iliac crest, while pulling slightly on the anterior thigh, to elicit sacroiliac joint pain.

Flamingo Test

The patient is asked to stand on the involved leg and hop. Pain in the sacroiliac region is indicative of sacroiliac joint dysfunction.

Gaenslen’s Test

The patient lies supine on the examining table with both knees drawn to the chest. The patient is then asked to shift over to the edge of the table, so that the leg being tested hovers over the edge. The examiner presses down on the affected side, hyperextending the hip. A positive Gaenslen’s test is generally considered a sign of sacroiliac joint pain but may indicate hip pathology as well.

Gillet’s Test

While the patient stands with the feet approximately 12 inches apart, the examiner sits behind the patient and palpates the S2 spinous process with one thumb and the posterior superior iliac spine with the other. As if taking a large marching step, the patient then flexes the knee and hip of the side being tested. If the posterior superior iliac spine fails to move posteroinferiorly with respect to S2, the test is positive. This test is an indicator of sacroiliac joint dysfunction.

Patrick’s Test

The patient is positioned supine with the foot of the involved side against the opposite knee. The sacroiliac joint is then stressed by pressing simultaneously against the flexed knee and contralateral anterior superior iliac supine. Although Patrick’s test is predominantly used to assess sacroiliac joint dysfunction, pain in the inguinal or hip area may indicate hip pathology as well. Because this test involves flexion, abduction, and external rotation of the hip, it is also called the FABER test.

Pelvic Compression Test

This test compresses the pelvis by the application of lateral pressure to the uppermost iliac crest, directed toward the opposite iliac crest. It is believed to stretch the posterior sacroiliac ligaments and compress the anterior part of the joint.

Pelvic Distraction Test

For this test, the examiner applies pressure to both anterior superior iliac spines, directed posteriorly and laterally. This test is alleged to stretch the anterior sacroiliac ligaments.

Pelvic Rock Test

The patient lies supine, and the examiner cups both hands around the iliac crests with the thumbs on the anterior superior iliac spine and the palms on the iliac tubercles. The examiner then forcibly compresses the patient’s pelvis toward the midline of the body. Complaints of pain may indicate pathology in the sacroiliac joint.

Sacroiliac Shear Test

With the patient lying prone, the examiner crosses both hands over the sacrum. The overlying hand delivers a postero-anterior thrust, while the underlying hand is used to detect motion in the joint.

Thigh Thrust Test

This test applies a posterior shearing stress to the sacroiliac joint through the femur.

Beatty’s Maneuver

From the lateral decubitus position with the nonpainful side dependent, the patient is asked to abduct the thigh by moving the nonpainful leg off the table. Contraction of the piriformis muscle elicits pain in patients with piriformis syndrome.

Freiberg’s Sign

Recreation of buttock or leg pain, or both, occurs during internal rotation of the hip. This test may be positive in patients with piriformis syndrome.

Pace Sign

An indicator of piriformis syndrome, this test is positive when the patient experiences weakness during resisted abduction and external rotation of the leg.

Beevor’s Sign

While the examiner observes the patient’s umbilicus, the patient Is asked to do a quarter sit-up with the arms crossed over the chest. Normally, the umbilicus should not move. If the umbilicus is drawn up, down, or over to one side (the stronger side), weakness, atrophy, or asymmetry of the anterior abdominal or paraspinal muscles may be present. This sign is frequently positive in patients with meningomyelocele or poliomyelitis.

Sit-Up Test

Patients with severe discogenic pain or paraspinal muscle spasm have difficulty sitting up unassisted when flexed at their lumbar spine. They have a tendency to push up with their arms for support.

Tripod Sign

As the patient sits with legs dangling and hips flexed 90 degrees, the knees are passively extended. Patients with hamstring muscle tightness will extend the trunk to relieve the pressure.

Hoover’s Test

This test is helpful when malingering is suspected, and should be performed in conjunction with the straight-leg raising test. A patient who is making a genuine effort to raise the affected leg will automatically put pressure on the calcaneus of his opposite leg in order to gain leverage. By placing one hand under the patient’s heel, the examiner can determine whether or not the patient is making a concerted effort.

Kneeling Bench Test

While kneeling on a 12-inch bench, the patient is asked to bend forward and touch the floor. The only requisite for this maneuver is flexion at the hips. If the hips are normal and the patient’s fingers do not touch the floor, nonorganic pain is suspected.

Voluntary Release Test

This test is used to distinguish patients with true organic pathology from those with nonorganic complaints. When attempting a sustained muscle contraction such as flexion at the ankle, patients with nonorganic symptoms sustain the position with jerking and quivering movements, and release the contraction in a similar fashion. In contrast, patients with organic pathology execute these movements smoothly.

Waddell’s Signs

The following physical signs are used to distinguish patients with organic pathology from those with functional disorders and malingering:

• 1. Tenderness. The skin is tender to light pinching over a large lumbar area, or deep tenderness is experienced over a wide area and is nonanatomic in distribution.
• 2. Stimulation tests. The patient complains of low back pain when vertical pressure is exerted on the skull, or reports back pain when the pelvis and torso are rotated in the same plane.
• 3. Distraction tests. A positive test is elicited in the normal fashion during physical examination. This test is then repeated when the patient is distracted. A positive distraction test finding occurs when pain elicited during a formal examination disappears when the patient is distracted.
• 4. Discrepancies between symptoms and neuroanatomy. Examples include the patient who exhibits sensory abnormalities in a stocking rather than a dermatomal distribution, or one who demonstrates unexplained motor weakness.
• 5. Overreaction during the examination. This may take the form of excessive facial expressions, yelling, jumping, or cringing.

Babinski’s Reflex

Stimulation is applied to the plantar surface of the foot with a dull object. When the lateral four toes flex and fan and the large toe extends, an upper motor lesion is suspected.

Chaddock Reflex

This test is similar to the Babinski’s reflex test, except that the lateral aspect of the foot beneath the lateral malleolus is stimulated.

Oppenheim’s Test

A dull object is run down the anterior portion of the tibia. A positive response is similar to Babinski’s reflex.

Femoral Stretch Test

With the patient lying prone and the knees flexed, the legs are pushed backward toward the buttock. Pain felt in the anterior thigh may indicate entrapment of the femoral nerve or its nerve roots.

Schober’s Test

This test measures the flexibility of the lumbar spine. The patient’s back is marked twice, once at the level of the sacroiliac dimples, and again 10 cm above this point. As the patient flexes forward, the distance between the two points should increase by at least 4 cm. An abnormal test may indicate spondyloarthropathy.