Low Back Pain

Low Back Pain



Kerry H. Levin



DEFINITION


Low back pain can best be described in terms of specific accompanying features. Low back pain is acute if it has a duration of about 1 month or less. Chronic low back pain is usually defined by symptoms of two months or more. Both acute and chronic low back pain can be further defined by the presence or absence of neurologic symptoms and signs. Nonspecific or nonradicular low back pain is not associated with neurologic symptoms or signs. In general, the pain is localized to the spine or paraspinal regions (or both) and does not radiate into the leg. In general, nonspecific low back pain is not associated with spinal nerve root compression. Nonspecific low back pain might or might not be associated with significant pathology on magnetic resonance imaging (MRI) and is often a result of simple soft tissue disorders such as strain, but it can also be caused by serious medical disorders arising in the bony spine, parameningeal, or retroperitoneal regions. See Table 1 for the differential diagnosis for low back pain.


Table 1 Differential Diagnosis of Low Back Pain



























Mechanical Causes Nonmechanical Causes Causes of Referred Pain
Idiopathic (sprain, strain) Malignancy Pelvic disease (prostatitis, endometriosis, pelvic inflammatory disease)
Spondylosis (disk, annulus, facet) Infection Renal disease (kidney stones, pyelonephritis, perinephric abscess)
Compression fracture Inflammatory spondyloarthropathy (ankylosing spondylitis, psoriatic spondylitis, Reiter’s syndrome, inflammatory bowel disease) Aortic aneurysm
Traumatic fracture Osteochondrosis Gastrointestinal disease (pancreatitis, cholecystitis, penetrating ulcer)
Alignment disorders (kyphosis, scoliosis, spondylolisthesis) Paget’s disease of bone  

Low back pain accompanied by spinal nerve root damage is usually associated with neurologic signs or symptoms and is described as radiculopathy. There is usually pathologic evidence of spinal nerve root compression by disk or arthritic spur, but other intraspinal pathologies may be present and are often apparent on an MRI scan of the lumbosacral spine.



PREVALENCE


Low back pain is second only to upper respiratory illness as a cause for visiting a physician.1 Up to two thirds of the population has low back symptoms at some time in their lives. In 1995 there were about two worker’s compensation claims for low back pain for every 100 workers. Seventy-five percent of patients with acute low back pain are back to work within 1 month of the onset of symptoms, and only 5% are disabled for more than 6 months.2 However, among those with continuing pain 6 to 10 weeks after onset, most still have some symptoms at 1 year.3


Among persons with chronic low back pain without neurologic deficits, a number of factors play a role in the length of disability. Recurrent low back pain and prolonged disability tend to correlate with prior history of low back pain, advancing age, job dissatisfaction, emotional distress, heavy or repetitive lifting and physical work, prolonged sitting or standing, and the presence of a worker’s compensation claim or pending litigation.4


Lumbosacral radiculopathy and radicular low back pain are less common than nonspecific low back pain. L5 radiculopathy is the most common lumbosacral radiculopathy, usually produced by disk herniation between the fourth and fifth lumbar vertebral bodies. S1 radiculopathy is the next most common, followed by L3 to L4 radiculopathy.



PATHOPHYSIOLOGY


The pathophysiology of nonradicular low back pain is usually indeterminate. In fact, one of the defining features of this disorder is its nonspecific etiology. Pain can arise from a number of sites, including the vertebral column, surrounding muscles, tendons, ligaments, and fascia. Stretching, tearing, or contusion of these tissues can occur after sudden unexpected force applied to the spine from events such as heavy lifting, torsion of the spine, and whiplash injury. Whether muscle spasm is a significant etiology of lumbar spine pain, either as cause or effect of back injury, has not been proved.


The pathophysiology of radicular spine pain and lumbosacral radiculopathy is usually more obvious. Disk herniation through the annulus fibrosis does not in itself produce pain, but compression by disk of the dural lining around the spinal nerve root sleeve is one likely explanation for the back pain associated with acute disk herniation. This is also likely to contribute to the pain from spinal nerve root compression from arthritic spurs at degenerated facet and uncovertebral joints. Compression can directly stretch nociceptors in dura or nerve root sleeve tissues, but ischemia from compression of vascular structures, inflammation, and secondary edema is also likely to play a role in some cases.



SIGNS AND SYMPTOMS


History and physical examination are critical to the diagnosis and thus to the formulation of a rational approach to management. The following briefly summarizes the major points.



History


The medical history should focus on both triggering and alleviating factors, as well as on the character of the pain. Signs and symptoms such as increased pain with Valsalva maneuvers, straight-leg-raising symptoms, the tendency for the pain to radiate into the buttock or leg, the presence of weakness or sensory deficit, and bowel or bladder urgency or incontinence are associated with neurologic causes of low back pain.


The history should also explore factors that increase the likelihood of an underlying systemic disorder as a cause. These include advanced age, history of cancer, unexplained weight loss, use of injected drugs, chronic infection, prolonged duration of pain, pain that does not respond to rest or recumbency, and failure to respond to previous therapy. Box 1 reviews these factors.



Box 1
Warning Signals of Systemic Disease Underlying Back Pain



Cancer

Prior history of malignancy

Advanced age

Unexplained weight loss

No pain relief with bed rest

Pain duration greater than 4 to 6 weeks

Failure to respond to standard therapies

Spinal infection

History of intravenous drug use

Urinary tract infection

Skin infection

Compression fracture

Advanced age

Trauma

Prolonged corticosteroid use

Rheumatologic disorders

Waddell and colleagues have described a number of historical features that point to nonorganic causes for low back pain, predicting delayed recovery and suggesting the need for a multidisciplinary approach to treatment.5 These are reviewed in Box 2.



Box 2 Historical Symptoms Suggesting Nonorganic Causes of Back Pain


Data from Waddell G, Bircher M, Finlayson D, Main CJ: Symptoms and signs: Physical disease or illness behaviour? BMJ (Clin Res Ed) 1984:289:739-741.



Pain at the tip of the tailbone

Whole-leg pain in global distribution

Whole-leg numbness in a global distribution

Sudden give-way weakness of the leg

Absence of even brief periods of relative pain relief

Failure or intolerance of numerous treatments

Numerous urgent care visits or hospitalizations for back pain


Examination


A general examination should be performed to identify potential systemic disorders, such as rheumatologic disease, skin disease, or bone deformities. The spine should be inspected for alignment, curvature, range of motion, focal tenderness, and overlying skin abnormalities such as a tuft of hair or pore. Mechanical maneuvers to elicit radicular and hip-joint symptoms should be considered, including straight-leg raising, reverse straight-leg raising, Patrick’s test, and Lasègue’s sign.


A careful neurologic examination should be undertaken to exclude motor and sensory deficits. Muscle strength in the L2 through S1 myotomes should be examined. The sensory examination should include soft-touch and pain sensation in the same segmental distributions. Muscle stretch reflexes should be elicited at the knee for the L3 to L4 segment and at the ankle for the S1 segment, and they can also be performed in the posterior thigh at the tendinous insertion of internal hamstrings for the L5 segment.


Waddell and colleagues have also described a number of findings on the physical examination that point to nonorganic causes for low back pain, predicting delayed recovery and suggesting the need for a multidisciplinary approach to treatment (Box 3).6



Box 3


Data from Waddell G, McCulloch JA, Kummel E, Venner RM: Non-organic physical signs in low-back pain. Spine 1980;5:117-125.


Signs on the Physical Examination Indicating Nonorganic Causes of Low Back Pain



Superficial tenderness over the lumbar region to light touch

Nonanatomic tenderness

Exacerbation of pain by applying a few pounds of pressure with the hands to the top of the head

Exacerbation of pain by simulated rotation of the spine

Ability to sit up straight from a supine position, but intolerance of the straight-leg-raising test

Nonanatomic distribution of sensory changes


DIAGNOSIS


The appropriate evaluation and management of low back pain rest on a few basic principles. First, it is necessary to determine whether the symptoms are caused by nerve root involvement. Second, it is necessary to determine whether the acute or chronic spine pain is related to a serious underlying medical illness that is manifesting itself as spine pain. After an initial assessment of the likely cause of the symptoms, the spine pain can then be treated.


A number of diagnostic tests can help pinpoint the cause of low back pain. Which test is selected depends on a host of factors uncovered during the history and physical examination. The diagnostic tests are described next.



Routine Radiographs of the Spine


Routine spine radiographs are of limited value because they visualize only bony structures. Guidelines from the U.S. Agency for Health Care Policy and Research (AHCPR) indicated value of routine spine radiographs for acute low back pain in the following settings: acute major trauma, minor trauma associated with risk of osteoporosis, risk of spinal infection, pain that does not respond to rest or recumbency, and history of cancer, fever, or unexplained weight loss.7 They may also be of value in assessing spinal alignment and rheumatologic disorders of bone.



Computed Tomography and Magnetic Resonance Imaging


Computed tomography (CT) and magnetic resonance imaging (MRI) are sensitive tools for evaluating neural structures such as spinal nerve roots and the spinal cord, and they can visualize soft tissue structures within the spinal canal. Of the two modalities, MRI resolution for neural structures is superior to CT. In the absence of motor, sensory, or autonomic deficits, and in the absence of significant trauma, infection, or malignancy, the American Academy of Neurology guideline recommends nonsurgical therapy before these techniques are used in patients with uncomplicated acute low back pain of less than 7 weeks’ duration.8 Patients with acute neurologic deficits associated with low back pain should be considered for MRI or CT of the lumbosacral spine unless surgery and invasive therapeutic options are not indicated.



Computed tomographic Myelography


CT myelography employs traditional myelography (intrathecal instillation of a radiocontrast agent, followed by routine spinal radiographs) followed by CT of the spine. It may be of value when MRI studies are inconclusive, especially in the assessment of the relation between spinal nerve roots and the bony neural foramina. Although this technique involves an invasive procedure, it is the study of choice when there are absolute contraindications to the use of MRI (presence of an implanted electronic device such as cardiac pacemaker or metal object in the inner ear, eye, or brain, such as an aneurysm clip).

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Jul 18, 2017 | Posted by in GENERAL SURGERY | Comments Off on Low Back Pain

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