Low Back Pain in the Elderly
Kim Edward LeBlanc
CLINICAL PEARLS
The L4 nerve root is evaluated by the patellar tendon reflex. Afflictions of the L5 nerve root are noted in the great toe. Diseases that affect the S1 nerve root are manifested by changes in the little toe.
During the side-bending maneuver, pain that is made worse by bending toward the contralateral side suggests muscular disease. Pain that is made worse by bending toward the ipsilateral side suggests disc disease.
Asymptomatic patients may have abnormal findings on computed tomography (CT) scan and magnetic resonance imaging (MRI). A patient’s complaints and symptoms must correlate with the actual findings on the scan.
A patient with lumbar spinal stenosis will find relief while leaning forward pushing a shopping cart, placing the lumbar spine in a flexed position.
Compression fractures are a fairly common event in the elderly and, in the lumbar spine, usually involve L1 or L2.
Approximately 50% of patients with solid tumors will have metastatic disease to the vertebral column.
In a patient complaining of back pain who has no abnormal findings on lumbosacral examination, the clinician should be alert that the pain may be emanating from an abdominal aortic aneurysm.
Low back pain is one of the most common ailments that afflict the population. In fact, this complaint is second only to an upper respiratory infection as the symptom that most often results in a visit to a physician’s office.1,2 In the United States, approximately 90% of all adults will have at least one episode of back pain in their lifetime.3 Furthermore, at least 50% of the working population of this country experiences back pain every year.4 This has significant impact on the well-being of not only the entire population, but the entire workforce as well.
The elderly population has been a relatively underrepresented and underreported group as a whole, but estimates
are that the prevalence of pain, in general, may be as high as 67% to 80%.5 Although the pain may occur in many different areas, similar to that experienced in their younger counterparts, back pain in the elderly has a high rate of occurrence. Back pain has been reported to be the third most common symptom in patients older than 75 years.6 However, in a systematic review of the literature, the frequency of low back pain in this population has been underestimated.7
are that the prevalence of pain, in general, may be as high as 67% to 80%.5 Although the pain may occur in many different areas, similar to that experienced in their younger counterparts, back pain in the elderly has a high rate of occurrence. Back pain has been reported to be the third most common symptom in patients older than 75 years.6 However, in a systematic review of the literature, the frequency of low back pain in this population has been underestimated.7
Low back pain may originate from a wide array of spinal structures, including muscles, fascia, ligaments, facet joints, vertebral periosteum, nerve roots, blood vessels, and the annulus fibrosis. Most commonly, the pain is associated with an age-related degenerative process, intervertebral disc herniation, or a musculoligamentous etiology.
Among patients older than 65, the more common diagnostic possibilities have a different emphasis as compared to those of a younger population. Although a so-called low back strain may occur in the older patient, osteoarthritis, compression fractures, carcinoma, spinal stenosis, and aortic aneurysms become much more frequent. This chapter will focus on some of the more common causes of back pain in the elderly, their diagnoses and treatments.
NORMAL AGING OF THE BACK
Some of the most notable changes associated with aging occur in the musculoskeletal system. Changes that have a direct impact on back stability and motion include the degenerative processes involving the intervertebral discs and joints, loss of bone mineralization, diminution of joint motion, decreased ligament flexibility, and the decline of muscle strength, endurance, and work capacity.
The lumbar spine and its supporting structures undergo degenerative changes with the aging process. The water and proteoglycan content of the nucleus pulposus decreases. This deterioration of the disc allows the vertebrae to move closer together. As this occurs, there is wearing of the articular cartilage of the apophyseal joints. Accompanying this is the formation of osteophytes, which may eventually begin to encroach on the vertebral spinal canal and foramina.
THE ANATOMY OF PAIN IN THE LUMBAR SEGMENT
Although there may be a variety of causes of back pain, a very important consideration in determining the cause is whether it is a mechanical etiology. In the elderly population, a nonmechanical cause should be considered prominently (e.g., primary or metastatic disease, infectious process, vascular disease) and ruled out when necessary.
However, regardless of age, the most common cause is related to a mechanical problem, with the pain emanating from a pain-sensitive structure. The most prominent of these include the vertebral periosteum, the spinal dura, the posterior longitudinal ligament, the outer third of the annulus fibrosis, and the associated vascular structures. These structures have a delicate nerve supply that produces pain whenever it is irritated.
In addition, each lumbar vertebra has a disc, which is pain-sensitive, and two facet joints, which are covered by a synovial membrane that is also pain-sensitive. There are many mechanical stresses placed on these structures that occur during flexion, extension, and rotation, particularly when supporting the body’s weight.
As degenerative changes progress, there may be encroachment on the nerve roots as they come off the spinal cord and exit through the intervertebral foraminal opening. Initially, this pain may be localized, but with advancing encroachment the pain may take on a radicular pattern specific to that nerve root.
The vertebrae are separated by intervertebral discs. The discs consist of the gelatinous nucleus pulposus that is surrounded by the annulus fibrosis. The major supporting structures of the vertebrae and discs are the paraspinal muscles and the ligamentous structures. The posterior elements of the vertebrae form the neural foramina, encase the spinal canal with bony protection, and interlock to form the facet joints. The main purpose of the facet joint is to allow motion of the bony segments.
There are several organs that are in close proximity to the lumbar spine lying anteriorly in a retroperitoneal location. These organs include the kidneys and ureters, the aorta and inferior vena cava, pancreas, and the periaortic lymph nodes. Any disease that affects any of these retroperitoneal structures could result in referred pain to the lumbar spine.
HISTORY
A complete and thorough history should allow an accurate working diagnosis in most patients. The history is particularly helpful in the geriatric patient as it aids in determining the effect the pain has on normal daily functioning.
The history should include the usual questions concerning past medical history, particularly comorbid conditions such as diabetes, cardiovascular disease, hypertension, carcinoma, and arthritic conditions. Past family and surgical histories should be obtained as well as questions on smoking, allergies, and present medications.
Specifically, the history should focus on the aspects of the low back pain, such as pain onset, the intensity of the pain, and specific location. Pain diagrams are helpful in allowing the patient to accurately display the location and radiation of the pain. Is there any associated trauma such as a fall or relationship to a particular inciting event or activity? What makes the pain worse? What makes the pain better? In what position is the pain most noticeable? Are there any associated neurologic symptoms or weakness, or bladder or bowel dysfunction? Are the symptoms rapidly progressive? A review of symptoms should be undertaken with questions directed toward underlying causes that
may suggest other organic problems, such as uterine leiomyomata, gastrointestinal diseases, aortic aneurysm, or carcinoma.
may suggest other organic problems, such as uterine leiomyomata, gastrointestinal diseases, aortic aneurysm, or carcinoma.
In the initial evaluation of a patient with acute low back pain it is important to keep in mind that certain positive findings in the history should raise “red flags.” These red flags should heighten the clinician’s suspicion that this may represent a significant disease process, something other than a simple musculoskeletal problem. For example, pain that begins following significant trauma or a fall should raise the suspicion of spinal fracture. If there is associated weight loss, presence of fever, or pain at rest, this suggests the possibility of a cancerous or infectious process. Pain that increases at night during sleep is quite suggestive of a neoplastic or infectious process as well. Lastly, the presence of bladder or bowel dysfunction, significant motor weakness of a limb, or saddle anesthesia suggests the possibility of cauda equina syndrome. More specific details will be provided in the subsequent text that describe each particular entity in detail.
PHYSICAL EXAMINATION
As in all phases of medicine, the physical examination should be both general and focused toward a specific diagnosis that is suggested by the history. Often overlooked is how the patient actually arrives in the office. The gait should be observed as well as how the patient sits. For example, a patient sitting in a chair and leaning back with an outstretched leg (to avoid stretching the sciatic nerve) should be suspected of having a significant disc problem. It is also important to observe directly and indirectly how the patient dresses and undresses. Indirectly observing a patient dressing and undressing while appearing to be “distracted” will allow the examiner to note inconsistencies in the complaints and movements. Palpation should be performed over specific areas of the lumbar region while noting muscle spasm, generalized and/or point tenderness of bone and soft tissue areas, and the alignment of spinous processes. Specific areas include the supraspinal ligaments, lumbar spinous processes, paraspinal musculature, sacroiliac joints, and coccyx. Localized soft tissue tenderness may be found with tumor, infection, or fracture (particularly point tenderness of bone).
Continuing in an orderly process, range of motion should be determined. The lumbar segment has six cardinal ranges of motion: Flexion, extension, lateral bending (both left and right), and rotation (both left and right). Each of these should be observed. Although the actual range of motion is important, the more pertinent findings should focus on the actual symmetry and quality of the motion. Biomechanical abnormalities and asymmetrical areas of flexibility may be noted during this phase of the examination. Considerable attention should be paid to the L4-5 and L5-S1 lumbar levels. Most of the motion of the lumbar segment occurs at these levels.
One of the most critical areas of the examination involves testing of neurologic function. This includes both the deep tendon reflexes and evaluation of muscle strength and sensation.
The L4 nerve root innervates the medial side of the foot (sensory) and the quadriceps muscle (motor). Consequently, impairment of the L4 nerve root will result in motor weakness during resisted quadriceps extension and difficulty when rising from a squatting position. L4 also has some role in ankle and great toe dorsiflexion. The knee jerk evaluates this nerve root at the patellar tendon level. Without nerve impingement, this deep tendon reflex will be asymmetrical when compared to the normal side.
The L5 nerve root innervates the dorsum of the foot (sensory) and the dorsiflexors of the ankle and great toe (motor). As a result, malfunctioning of this nerve root will result in motor weakness during heel walking and dorsiflexion of the ankle and great toe. There is no deep tendon reflex for the L5 nerve root.
The S1 nerve root innervates the lateral side of the foot and little toe (sensory) and the gastrocnemius muscle, soleus muscle, and toe flexors (motor). Impairment of S1 will result in weakness or inability to toe walk and plantar flex the foot and great toe. The S1 nerve root will be evaluated by the Achilles tendon reflex and noting any asymmetry when compared to the unaffected side.
The straight leg raise is a well-known maneuver that places the sciatic nerve on stretch and may be performed in a supine or sitting position. With impingement of a nerve root secondary to a herniated nucleus pulposus (disc), the resulting stretch will produce pain in a pattern specific to the nerve root. L4 will extend to the anterior thigh and leg; L5 down the leg to the great toe. S1 impingement will extend the pain down the lateral side of the leg to the little toe. A positive finding is reproduction or intensification of the pain that extends below the knee and not just in the back, buttocks, or posterior thigh. An age-related phenomenon must be noted. Older patients often have less disc volume due to desiccation. Therefore, these patients may not have a frankly positive nerve root.
There are occasions when the physical findings may not suggest pathology in the lumbar area and other physical testing should be employed. Most notable, pathology of the hip or sacroiliac joints may pose diagnostic conundrums. The flexion, abduction, and external rotation (FABER) maneuver should be utilized in this situation as it is a provocative maneuver specifically isolating the hip and sacroiliac joints. FABER stands for flexion, abduction, and external rotation and may also be referred to as the “figure-of-4” test. In performing this maneuver, the patient should be in the supine position. The affected lower extremity (hip) is placed in FABER and then the foot is placed on the opposite knee or proximal tibia (essentially producing
a figure-of-4). If this maneuver is painful on the ipsilateral side, then hip or sacroiliac joint pathology should be considered, depending on where the patient indicates the pain is located. Pain reproduced on the contralateral side or increased pain caused by the maneuver is a nonspecific finding and may not be helpful.
a figure-of-4). If this maneuver is painful on the ipsilateral side, then hip or sacroiliac joint pathology should be considered, depending on where the patient indicates the pain is located. Pain reproduced on the contralateral side or increased pain caused by the maneuver is a nonspecific finding and may not be helpful.
Abdominal and rectal examinations should be performed for findings that may suggest a cause for the complaints of back pain such as prostate or rectal carcinoma.
Gynecologic examinations should be performed when appropriate.
SPECIFIC CAUSES OF LOW BACK PAIN—DIFFERENTIAL DIAGNOSES
Back pain has a wide array of causes, as noted in Table 14.1.8 The most common etiologies in the elderly can usually be divided into mechanical causes, pain related to osteoporosis, or systemic entities such as tumor and infection. In determining the cause, the age of the patient does direct the physician to certain diagnoses that occur with higher frequency at that particular time of life.
The next section of this chapter will discuss some of the most common causes of back pain in the elderly population, along with the proper workup, including keys in making the diagnosis, as well as management and treatment of each entity.
TABLE 14.1 DIFFERENTIAL DIAGNOSES OF LOW BACK PAIN | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Low Back Sprain/Strain—ICD-9 Code: 847.2
CASE ONE
A 66-year-old man presents to your office complaining of low back pain that began while lifting several lawn chairs a few days ago. Although these chairs were not heavy, he noted pain within a few minutes in the lower back, with discomfort also noted in the buttocks and upper posterior thigh regions. He is active and healthy, with no prior history of back problems, weight loss, fever, or prostatic symptoms.
A sprain refers to injury to a ligamentous structure while a strain refers to injury to a muscle. When referring to the low back, sprain may be used in reference to injury to the paraspinal muscles. However, this term is also frequently used when referring to ligamentous injury of the annulus fibrosis or vertebral facet joints. The terms sprain and strain are often used interchangeably because of the deep location of the soft tissues of the lumbar region, rendering a precise location virtually impossible most of the time. Fortunately, a precise determination is usually not required as the management is virtually identical.
Workup/Keys to Diagnosis
Physical Examination
The patient may have subtle or obvious discomfort, with difficulty standing erect. Sitting may be uncomfortable or require frequent changes in position. Palpation reveals diffuse tenderness in the lower back and perhaps the sacroiliac area. Range of motion will be limited, particularly flexion. Side bending may worsen the pain when bending toward the contralateral side as a result of the stretching of the tissues. Neurologic examination is normal, including both sensory and motor function.
Imaging
In patients with a typical presentation, no studies are necessary. Beyond the age of 30, plain radiographs typically show a varying degree of degeneration such as disc space narrowing with or without spurring. Therefore, plain films are not helpful in this setting. However, in a patient with atypical symptoms or in one who fails to show improvement in 2 weeks, obtaining lumbosacral films should be considered. The overriding reason for obtaining radiographs at this point is to further evaluate the atypical symptoms or lack of significant symptomatic improvement. The radiographs will help confirm the diagnostic suspicions or suggest other causes of back pain, such as malignancy or infections.
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