Most people will experience at least one episode of back pain during their adult lifetime. Such episodes are usually of short duration, lasting from days to a few weeks. Many will resolve without any therapeutic intervention. The challenge is to manage the pain by using conservative yet adequate measures while limiting the more invasive diagnostic evaluations to those patients who present with associated worrisome features. These red-flag issues include new neurologic signs or symptoms; such systemic complaints as fever, weight loss, or sweats; loss of bowel or bladder function; and nighttime pain.
Presentation of low back pain
While back pain can affect individuals of any age, it is most frequently seen between the ages of 20 and 40 years. Gender distribution is equal. Initial patient assessment requires adequate characterization of the pain.
Where does it hurt?
Patients with back pain may describe a dull steady ache or diffuse pain at the base of the lumbar spine and over the buttocks. There usually is no point tenderness. The pain may or may not radiate into the thigh or lower extremity.
When does it hurt?
Most patients note a change of pain symptoms with a change in body position. For example, in disk-related back pain, symptoms are worse when the patient sits or stands for extended periods of time. Coughing or sneezing may aggravate symptoms related to a disk herniation that is impinging on nerve roots, while lying flat alleviates the pain. Forward flexion of the back may open up narrowed spinal-canal foraminal spaces in patients with lumbar spinal stenosis and improve their pain symptoms. These patients describe pain relief when leaning forward to push a shopping cart (“shopping cart sign”). In contrast, standing, which requires either a neutral stance or slight extension of the back, obliterates these foraminal spaces and often aggravates the pain.
How does activity affect the pain?
In general, back-pain symptoms improve with rest, at least in the short term. Patients with back pain due to a spondyloarthropathy, however, note more stiffening and worsening of symptoms following prolonged inactivity. These patients have nighttime symptoms and feel worst in the morning upon rising. Patients with back pain due to disk degeneration or spinal stenosis often feel best in the morning and note worsening symptoms as the day progresses. Spondyloarthropathies are more common in men and are often associated with HLA-B27 positivity.
Does the pain radiate?
Nerve-root impingement caused by disk protrusion or osteophytes due to osteoarthritis in the lumbar spine may cause sharp, shooting discomfort radiating down the leg(s), known as “sciatica.” Patients suffering from this condition may or may not experience associated low back pain. Depending on the location of the nerve impingement, symptoms may be unilateral or bilateral. Patients may also experience other sensory symptoms, such as burning or dysesthesia. When nerve impingement leads to a disruption of motor function, there may be complaints of weakness or even foot drop. Deep tendon reflexes may be reduced. These changes follow a dermatome pattern that corresponds to the affected nerve root.
What relieves the pain?
By the time they seek medical help, many patients have already tried low doses of nonsteroidal anti-inflammatory drugs (NSAIDs) or acetaminophen, with variable results. A careful history may reveal that these analgesics are partially effective, and a dose increase might be useful for additional pain relief. The application of heat or cold (showers, ice, or heat packs) to the low back may provide transient relief but does not yield any diagnostic clue regarding pain causation.
Establishing the diagnosis
Physical examination of the back is among the most commonly overlooked and underutilized portions of the patient evaluation. Inspection of spine posture can demonstrate scoliosis or asymmetry of muscle bulk and tone, suggesting spasm. In cases of vertebral compression fracture, there may be localized tenderness to palpation. The majority of patients will demonstrate poor lumbar flexibility. Patients should be asked to extend their spines backward from the neutral standing position. In cases of spinal stenosis, extension is generally more painful than forward flexion.
A straight-leg raise (SLR) test should be performed with the patient supine and the uninvolved knee bent to 45° and resting on the table. The examiner should hold the involved leg straight, cup the heel with the other hand, and gradually raise the leg. With a disk herniation that impinges on an irritated nerve root, the SLR will stretch the root, and pain will radiate below the tested knee, not merely in the back and hamstring muscles. The SLR test is positive if distal leg pain occurs with leg elevation <60°. Pain down the tested leg is sensitive but not specific for disk herniation, whereas pain down the non-tested leg (crossed SLR) is highly specific but not sensitive.
The value of these tests declines with advancing age. Sensory motor and deep tendon reflex examinations detailing areas of dysesthesia or hypoesthesia, motor weakness, and altered reflexes may help to identify the disk level of involvement.