IMPAIRMENTS, ACTIVITY LIMITATIONS, AND PARTICIPATION RESTRICTIONS

The lumbar spine is associated with a wide range of clinical disorders. Although lumbar spine pathology may be a result of rheumatologic, hematologic, endocrinologic, and even neoplastic disorders, most impairments of the lumbar spine are the results of mechanical disorders.

Mechanical disorders refer to pain that results from overuse of a normal anatomic structure or pain that results from trauma or deformity of an anatomic structure (1). Common mechanical disorders from the lumbar spine include muscle strain, degenerative disc disease, osteoarthritis, lumbar stenosis, spondylolysis, and scoliosis. Discussion of the presentation of each differential diagnosis is beyond the scope of this text.

Disabilities that result from the lumbar spine may result in an inability to meet personal, social, and occupational demands. Patients with lumbar spine pathology often will have difficulty performing ADLs, functional mobility, and work duties.

General population studies have demonstrated that most low back pain episodes are mild and rarely disabling, with only a small proportion seeking care. Among patients who do present for care, 75% to 90% of those with “acute” low back pain recover in terms of pain and disability (3). This is in contrast to those with “chronic” low back pain, when pain is present greater than 3 months, and where prior studies have shown that two-thirds of patients still had not fully recovered 1 to 2 years after the initial onset of pain (3).

Biomechanical and anatomic factors often do not explain this variability in the clinical course of patients with lumbar spine pathology. There have been multiple psychosocial factors found to play a role in the prognosis for low back pain.

Prior literature reviews found that general psychological stress, negative cognitive characteristics, and depression are all associated with a poor prognosis for recovery (3). A study by Sullivan et al. found that depression is associated with increased pain intensity, disability, medication use, and unemployment among those with low back pain (4).

Prior literature reviews also reported that passive coping strategies, somatization symptoms, involvement of workers’ compensation, involvement of legal representation, and fear avoidance were also associated with poor outcomes (3,5).

Other studied vocational psychosocial factors include job satisfaction, subjective appraisal of one’s ability to work, significant prognostic factors in low back pain, and educational level (3,6).

Even though most patients with low back pain usually recover within a few weeks, work absenteeism can be a problem encountered by the physician. The biggest risk factors for delayed return to work and chronic disability are psychosocial variables, such as depression, level of education, excessive pain level, fear avoidance, job dissatisfaction, legal representation, somatization disorder, unemployment, and workers’ compensation (5).

Recommendations for return to work should be highly individualized. In general, patients with nonspecific low back pain should continue to work, even when they continue to have low back pain symptoms during work. However, patients may require modified duty at work to prevent the aggravation of symptoms. A functional capacity evaluation (FCE) and vocational rehabilitation may assist in the preparation for return to work.

Associated conditions with mechanical low back pain include osteoarthritis of the peripheral joints. A prior epidemiologic study found a higher prevalence of hip and knee osteoarthritis in patients with spinal degenerative disorders (9).

In a patient presenting with acute low back pain, a comprehensive rehabilitation program begins with activity modification. Patients should avoid strenuous activity that may aggravate symptoms and nerve root irritation. Despite activity modification, the patient should be encouraged to ambulate and perform activities as tolerated. Strict bed rest is not recommended. Patients should be encouraged to return to work with modified duties.

Medication management includes nonsteroidal anti-inflammatory medications (NSAIDs), acetaminophen, muscle relaxants, and, in severe pain states, consideration for opioid analgesics (controversial). If there is a significant neuropathic component, membrane stabilizers, such as anticonvulsants and antidepressants, may be added as adjuvant treatment. There is no role for systemic glucocorticoids as an adjuvant treatment.

Formal physical therapy should include core strengthening, trunk coordination, and endurance exercises. If there is lower extremity pain, directional preference exercises may be helpful. Williams exercises (flexion-based exercises) may provide additional benefit in patients with neurogenic claudication symptoms from lumbar stenosis. McKenzie exercises (extension-based exercises) may provide additional benefit in patients with an acute disc herniation.

Additional forms of adjuvant treatment may include modalities, such as ice and/or heat, transcutaneous electrical nerve stimulation (TENS), and orthotics, such as lumbar corsets.

A comprehensive rehabilitation treatment may also include interventional procedures, depending on the presentation. Intraarticular facet injections and medial branch nerve blocks may be utilized as treatment for axial pain associated with facet disease. Epidural injections may be helpful for patients with lumbar radiculopathy/stenosis.

MEDICAL KNOWLEDGE

GOALS

Demonstrate knowledge of established and evolving biomedical, clinical epidemiological, and sociobehavioral sciences pertaining to lower back pain, as well as the application of this knowledge to guide holistic patient care.

OBJECTIVES

Discuss the following as they relate to lumbar spine/low back pain: (a) anatomy and clinical correlates; (b) epidemiology; (c) pathophysiology; (d) differential diagnosis; (e) diagnostic tests, common laboratories, and imaging; (f) treatment modalities; and (g) psychosocial and ethical issues.

The lumbar spine is comprised of 5 lumbar vertebrae, numbered L1 through L5. There is a small percentage of the population with 4 or 6 lumbar vertebrae. Directly beneath each lumbar vertebra, there is a pair of neural foramina with the same number designation. The neural foramina are bounded superiorly and inferiorly by pedicles, anteriorly by the intervertebral disc and vertebral body, and posteriorly by facet joints.

The spinal cord terminates at the conus medullaris, usually at the L1 or L2 level. Therefore, all lumbar and sacral spinal nerve roots originate from these levels. The dorsal root from the posterolateral aspect of the spinal cord and a ventral root from the anterolateral aspect of the cord join in the spinal canal to form the spinal nerve root. The spinal nerve roots then course down the intraspinal canal, forming the cauda equina until they exit at their respective foramina.

The primary function of the lumbar spine is for flexibility and protection of the spinal canal. The flexibility of the lumbar spine is accomplished through the functional units of the vertebral segments. Each vertebral segment is comprised of 3 functional units. One functional unit is formed between 2 vertebral bodies connected through an intervertebral disc. The 2 other functional units are the facet joints, formed from the articulation of the superior articular process of one vertebra with the inferior articular process of the vertebra above. The orientation of the lumbar facets is at a 90° angle to the transverse plane and at a 45° angle to the coronal plane. This makes the primary motion of the lumbar spine flexion and extension, with minimal side bending and rotation.

Any innervated structure in the lumbar spine can cause symptoms of low back and referred pain into the (usually proximal) extremity or extremities. Common pain generators in the lumbar spine include muscles, ligaments, dura mater, nerve roots, facet joints, annulus fibrosis of the disc, thoracolumbar fascia, and vertebrae.

Degeneration of the lumbar spine is postulated to be secondary to a degenerative cascade known as spondylosis (10). In phase I of this process (dysfunction phase), initial repetitive microtrauma leads to the development of circumferential tears of the annulus fibrosis and associated end-plate separation that may compromise disc nutrition supply. The circumferential annular tears will coalesce to form radial tears, resulting in loss of ability of the disc to retain water. This will lead to loss of disc height, disc desiccation, and disc bulging. In phase II (instability phase), there is loss of the mechanical integrity of the disc, with further loss of disc height. The loss of disc height increases the mechanical stress on the facet joints. This leads to facet degeneration, subluxation, and instability. In phase III (stabilization phase), continued disc space narrowing and fibrosis occur along with formation of osteophytes in the facet joints and vertebral bodies.

This cascade of degenerative anatomic changes in the lumbar spine may lead to lumbar stenosis, facet disease, and degenerative disc disease. Lumbar stenosis is the narrowing of the central lumbar spinal canal, lateral recess, or foramen from the process of spondylosis. If there is nerve root compression, the process is known as lumbar radiculopathy.

INCIDENCE AND PREVALENCE

A review by Hoy et al. (11) estimated the 1-year incidence of low back pain to range between 1.5% and 36%. The same review estimated the point prevalence to range from 1.0% to 58.1% (mean: 18.1%; median: 15.0%) and the 1-year prevalence to range from 0.8% to 82.5% (mean: 38.1%; median: 37.4%). The prevalence tended to be highest in the third decade, and increased with age until 60 to 65, then gradually declined (11). Women and individuals with lower educational status tended to have a higher prevalence of low back pain, while individuals in sedentary jobs had a lower prevalence of low back pain (12).

Low back pain has a significant psychosocial component. As mentioned previously, multiple psychosocial factors have been identified that are associated with low back pain. Therefore, psychological intervention may often play a role in the evaluation and treatment. One of the common psychosocial interventions for chronic pain is cognitive behavioral therapy (CBT) (13). CBT involves 3 basic components. The first component is a treatment rationale that helps patients understand that cognition and behavior may affect the pain experience and emphasizes the role that patients can play in controlling their own pain. The second component of CBT is coping skills training (relaxation techniques, distraction, etc.). The third component involves the application and maintenance of learned coping skills (13).

TREATMENT

Treatment of musculoskeletal disorders in the lumbar spine involves patient education, activity modification, lumbar support, therapy, medications, and injections.

Patient education topics include reassurance, methods of symptom control, and recognition of the red flags. Activity modification may include limiting prolonged sitting, heavy lifting, and excessive bending. Patients with radiculopathy, compression fracture, and disc disease should avoid flexion. Patients with stenosis and facet disease should avoid extension. Despite activity modification, patients should be encouraged to return to work as soon as possible.

Lumbar supports may prevent excessive spinal motion and/or reduce compressive loading of the spine by increasing intraabdominal pressure, but have limited evidence for efficacy. A thoracolumbar sacral orthosis (TLSO) is used in conditions requiring directional restriction, such as compression fractures and post laminectomy.

Therapy for the lumbar spine includes both physical therapy and exercise therapy. As mentioned previously, formal physical therapy may include core strengthening, trunk coordination, and endurance exercises. Directional preference exercises (Williams and McKenzie exercises) may be utilized in certain diagnoses. Patients may be candidates for aquatic therapy if land-based exercises are not tolerable. Modalities during therapy may include heat, ice, TENS, and traction.

Exercise therapy may include aerobic conditioning exercises, such as swimming, walking, and stationary biking. Home exercise programs may also be prescribed by the physician or therapist, where exercises will focus on correcting lumbar spine alignment, posture, and weakness.

Medications for treatment of musculoskeletal disorders in the lumbar spine include NSAIDs, acetaminophen, antidepressants, muscle relaxants, anticonvulsants, and opiates.

NSAIDs provide pain relief in both acute and chronic low back pain, but are associated with risks of gastrointestinal bleeding, renal dysfunction, exacerbation of hypertension, and cardiovascular risks. Antidepressants have been found to be more effective for chronic low back pain, but are also associated with many side effects.

Muscle relaxants are controversial due to the unclear role that muscle spasms play in low back pain. Opioids, like muscle relaxants, are also controversial. Opioids have potential for addiction, tolerance, and significant adverse effects.

Interventional treatments for musculoskeletal disorders of the lumbar spine include trigger point injections, epidural injections, facet injections, and medial branch nerve blocks.

Trigger point injections are indicated for myofascial pain, while epidural injections are indicated for lumbar radiculopathy, stenosis, and pain associated with discogenic disease. Facet injections and medial branch nerve blocks are indicated for axial pain associated with facet disease.

One prior review (14) attempted to systematically assess the benefits and harms of surgery for nonradicular back pain with common degenerative changes, radiculopathy with herniated lumbar disc, and symptomatic spinal stenosis. The review found that surgery for radiculopathy with herniated lumbar disc and symptomatic spinal stenosis is associated with shortterm benefits compared to nonsurgical therapy, though benefits diminish with long-term follow-up in some trials. Surgery for nonradicular back pain is no more effective than conservative management.

IMAGING, LABORATORY STUDIES, AND ELECTRODIAGNOSIS

Routine imaging of the lumbar spine should be discouraged due to the large number of “abnormal” imaging findings in asymptomatic individuals. One prior study found that one-third of asymptomatic subjects have a substantial abnormality on MRI (15).

An additional reason why routine imaging of the lumbar spine should be discouraged is because low back pain may often develop without radiologic change. Boos et al. (16) followed 46 asymptomatic patients with a herniated disc for an average of 5 years and found that MRI-identified disc abnormalities were poor predictors of the need for low back pain-related medical consultation when compared to the psychological aspects of work.

Current recommendations from the American College of Physicians (17) regarding imaging for low back pain are that (a) imaging is only indicated for severe progressive neurological deficits or when red flags are suspected and (b) routine imaging does not result in clinical benefit and may lead to harm.

When imaging is obtained, it is essential that radiologic findings be corroborated with patient presentation.

Common imaging modalities for the lumbar spine include plain films, CT, and MRI. Plain x-rays evaluate bony structural anatomy. Findings on lumbar spine plain films that may correlate with mechanical low back pain include fractures, transitional vertebra, spondylolisthesis, spondylolysis, excessive lordosis, scoliosis, disc space narrowing, osteophytes, facet disease, and neuroforaminal narrowing. Plain films are unable to evaluate soft-tissue structures. Flexion and extension x-rays may help determine if spinal instability is present, such as when spondylolisthesis is of concern.

CT scans are particularly useful for evaluating the details of bony structures. A CT scan may be indicated if there is suspicion of bony involvement with negative plain films. It may also be utilized in surgical planning. A CT may be combined with myelography, which significantly improves sensitivity. A CT myelogram may be indicated when the patient has a contraindication to MRI.

MRI is currently considered the “gold standard” in spinal imaging because of its ability to provide detailed imaging of the soft tissues, spinal canal, neuroforamen, ligaments, and disc. However, its high sensitivity may be detrimental to patient care because of its ability to mark “positive findings” in the asymptomatic patient.

Electrodiagnostic studies may play a pivotal role in the diagnosis of lumbar spine pathology. Nerve conduction studies and electromyography (EMG) assist in the physiologic (as opposed to anatomic in MRI) localization of a pathologic lesion. It is also useful in determining the type and severity of the neural injury, chronicity, as well as the prognosis for neural recovery. A nerve conduction study may be useful in ruling on peripheral nerve pathology, which may often present similar to lumbar spine radiculopathy or other pathology.

Laboratory studies are not typically useful in mechanical lumbar spine pathology, but may be useful for ruling out rheumatologic, hematologic, endocrinologic, and neoplastic disorders.

ETHICAL CONSIDERATIONS

Ethical issues in the management of low back pain involve both the physician and the patient. McGee et al. (18) held stakeholder meetings in 5 U.S. cities and found 6 main ethical issues relevant to chronic pain: