Low back pain is a common problem in older individuals, but its etiology, natural history, and therapy are not well defined. Epidemiologic studies have reported the prevalence of back pain in older individuals from 6% to 47%. A recent Israeli study found that 44% of 70-year-olds and 58% of 77-year-olds reported back pain.

In the United States, back pain is the third most frequent symptom in those aged 75 years and older visiting their physicians. This pain is associated with depression, dependence in daily living activities, female gender, and poor self-reported health. The association of back pain and physical function has been quantified; the number of months with restricting back pain is associated with such markers of frailty as worsening rapid gait, chair stands, and foot tap performance. In the study of Medicare beneficiaries 65 years and older, back pain was second only to shortness of breath while climbing stairs in its association with impaired general physical health status.

Back pain is also becoming a substantial drain on health-care resources for older adults. While there was a 42% increase in total Medicare patients from 1991 to 2002, there was 131.7% increase in patients diagnosed with low back pain, and a 387% increase in low back pain charges.

It is clear that low back pain is a common problem for older individuals, is associated with poor outcome, and consumes a significant percentage of health-care resources. Our knowledge of the natural history and outcomes of this problem is limited. The studies during the past two decades that have helped to outline the natural history and outcome of back pain have been conducted exclusively in individuals younger than 60 years of age.

There is very little information in the literature on the natural history, associated features, and the etiology of older patients with back pain.

The clinician must first determine whether the problem is in the hip or back. It can be difficult to distinguish these conditions, as both can give buttock and low back pain. Pain that occurs when going from the supine to sitting position is more apt to be from the back, while groin pain, worsened with weight bearing, favors the hip. A complete examination of the passive range of motion of the hip, done with the patient in the supine position, should reveal 40 degrees of hip abduction, more than 100 degrees of flexion, 50 to 60 degrees of external rotation, and 20 degrees of internal rotation. In addition, a manual muscle examination of the lower extremities, which demonstrates mild weakness of the L4, L5 (hip abductor and great toe extensor) and L5, S1 (hip extensors) innervated muscles of the lower extremities, favors the back as the cause of pain. One recent study demonstrated that the presence of groin pain, a limp, and limited internal rotation of the hip all favored the hip as the cause of pain.

A number of discrete conditions may cause back pain in older individuals. These conditions include tumors, infections, vertebral compression fractures, osteoporotic sacral fractures sciatica, lumbar spinal stenosis, and mechanical causes. One approach to the assessment of back pain in older individuals is to evaluate those patients for the historical, physical, and diagnostic imaging features of these discrete conditions and then to appraise the patient with nonspecific low back pain without one of these conditions.

Tumor

The clinician must always be alert to nonmechanical, either referred or systemic, causes of low back pain. Visceral causes of back pain, such as abdominal aortic aneurysms or pancreatic cancer, are usually nonpositional, progressive, and associated with a normal examination of the lumbar spine and hip.

Tumors usually present with a gradual onset and progressive course, with persistent worsening of the pain over weeks and months. This insidious onset of pain, which is initially mild but progressive in severity, is quite distinct from the abrupt onset and positional characteristics of mechanical low back pain. Tumor pain is often nonpositional, lasts longer than 4 weeks, and is associated with systemic symptoms. One study found that an abnormal CBC and ESR are the best screening tests for tumor as a cause of back pain.

Infection

Although a rare cause of back pain, vertebral and disc infections can be difficult to distinguish from a mechanical cause of back pain; disc infections can cause the same abrupt onset, positional changes, and L4, L5 and L5, S1 neurologic abnormalities seen in mechanical disc disease.

Back pain is the most common musculoskeletal complaint seen in endocarditis. Because the disc is often involved in this condition, the signs and symptoms can mimic mechanical disc disease. Fever can be absent in older patients with infection. The clinician must be alert to a possible infectious cause of back pain for patients with a high risk of endovascular infection (artificial heart valves, indwelling venous catheters, intravenous drug abuse, etc.) and in patients with systemic symptoms and signs of inflammation.

Vertebral Compression Fractures

The abrupt onset of severe back pain, especially in a patient with risk factors for osteoporosis, should always call for a spinal x-ray to rule out a vertebral compression fracture (Table 121-1). At times, the initial x-ray is normal and the changes of vertebral collapse appear several days to weeks after the onset of pain. As there is no dislocation with osteoporotic vertebral fractures, neurological signs and symptoms are quite rare. Pain may be referred, however, into the chest, abdomen, or leg. Any movement, even rolling in bed, usually exacerbates the pain for the first several days. Pain then gradually improves over the next several weeks and resolves in 6 weeks.

Only approximately 30% to 40% of vertebral compression fractures are symptomatic. Most symptomatic fractures are in the lower thoracic and lumbar spine. Most mid and upper thoracic fractures are asymptomatic.

The presence of a vertebral fracture does increase the risk of a subsequent fracture. In a multicenter study of osteoporosis, the presence of a fracture increased the risk of subsequent fractures in the next year from 6.6% to 19.2%.

The role of osteoporosis and vertebral fracture in chronic back pain and disability is not clear. The finding that fractures are associated with increased mortality from pulmonary disease and cancer indicate that these fractures may be markers of frailty. While some studies have shown increased disability in patients with vertebral fractures, a British population-based study found no correlation between minor vertebral deformities and back pain. A study of women in Hawaii showed a correlation between recent fractures and back pain, but the prevalence of back pain among women with prevalent fractures was not significantly higher than those without these fractures. Finally, the Study of Osteoporotic Fractures found an increase in back pain and disability only if vertebral deformities were greater than 4 standard deviations from the mean.

Osteoporotic Sacral Fractures

There have been a number of reports of “sacral insufficiency fractures” as a cause of back pain. Older patients, usually women, complain of dull low back pain. This pain is also felt in the buttock area. The application of pressure to the sacrum is very painful. Associated neurologic defects have not been reported. The pain usually resolves spontaneously in 4 to 6 weeks. Approximately 50% of these patients had a preceding fall, and the majority of patients have old pelvic and vertebral compression fractures on x-ray.

Plain x-rays of the sacrum are normal, but technetium bone scans demonstrate the fractures. CT scans of the sacrum usually show displacement of the anterior border of the sacrum. A sacral insufficiency fracture should be considered if a woman with osteoporosis develops sudden pain in the low back and buttock with sacral tenderness.

Sciatica

Sciatica is usually defined as pain radiating to one leg below the gluteal fold. It is often felt in the buttock area, radiating into the posterior aspect of the leg down to the ankle. It may, however, be incomplete, as in the calf pain seen in the “pseudoclaudication” syndrome with lumbar spinal stenosis. The natural history of this condition is well defined in younger adults. Fifty percent of these patients have full resolution of symptoms within 6 weeks. While there are no studies of the natural history of sciatica in older patients, many clinicians do find that sciatica, which develops abruptly and occurs in all positions, usually has a good natural history, similar to that seen in younger individuals. Patients who develop sciatica as part of the lumbar spinal stenosis syndrome, with gradual progression of pain with shorter and shorter periods of standing and walking, have a more prolonged and persistent natural history.

Lumbar Spinal Stenosis

Narrowing of the lateral recess of the vertebral canal, as well as the anterior–posterior diameter of the canal, is frequently seen on diagnostic imaging tests of the lumbar spine in older individuals. These abnormalities have clinical significance only if the typical history of lumbar spinal stenosis is present (Table 121-2).

Changes in spinal dynamics with movement explain some of the clinical features of lumbar spinal stenosis. Flexion of the lumbar spine decreases the intraspinal protrusion of the disc, decreases the bulge of the yellow ligaments within the canal, and stretches and decreases the cross-sectional area of nerve roots, resulting in an increase in spinal canal volume in relation to nerve root bulk. Extension of the lumbar spine causes bulging of the disc into the canal, enfolding and protrusion of the yellow ligaments into the spinal canal, and a relaxation and increase of the cross-sectional diameter of nerve roots. Extension of the canal thus produces a decreased volume of the spinal canal in relation to nerve root bulk.

These changes in dynamics explain the clinical picture of lumbar spinal stenosis. Positions that extend the spine (standing, walking down hill, prone lying, and extending the back) worsen symptoms, while positions that flex the spine (sitting, bending forward, placing weight on a walker or cart, and lying in a flex position) relieve the symptoms.

Patients with lumbar spinal stenosis present with pain, either in the lower back or legs, which comes on with prolonged standing and walking and is relieved with sitting. Individuals with this condition will often bend their spine more as they walk and find that they can walk further in a grocery store, supported by a cart. The leg pain can present with a classic picture of sciatica (pain radiating from the posterior aspect of the buttock down to the foot) or an incomplete “pseudoclaudication” syndrome, in which the patient feels pain only in the calf while standing and walking.

Lumbar spinal stenosis should not produce pain when going from lying to sitting and should not produce severe pain with bending, stooping, or lifting objects. In a masked study comparing radiologic and electrodiagnostic diagnoses to clinical impression, MRI findings and their interpretation did not relate in any important way to the clinical diagnosis of lumbar spinal stenosis.

Mechanical Low Back Pain

The majority of older people with low back pain do not have tumors, infections, lumbar spinal stenosis, or vertebral compression fractures (Table 121-3). They are best described as patients with mechanical back pain of uncertain etiology. Because the nucleus pulposus loses water content with aging, herniation of this structure is unusual beyond the age of 55 years.