Definition

Degeneration of the anatomic structures of the lumbar spine is a process associated with aging. Degenerative processes may affect several anatomic structures, resulting in different clinical syndromes, or may be entirely asymptomatic. Approximately one third of asymptomatic and one half of symptomatic younger adults show degenerative changes on lumbar spine magnetic resonance imaging [1,2]. At ages older than 60 years, degenerative changes are found in more than 90% of adults [3]. Degeneration may be accelerated in patients with previous trauma or injury to the lumbar spine. Factors such as diabetes mellitus, smoking, and obesity have been associated with increased rates of lumbar spine degeneration. L4-L5 and L5-S1 are the most commonly involved lumbar levels, given that they undergo the greatest torsion and compressive loads during activity. There has not been a proven gender predominance; however, some studies suggest that disc degeneration may affect more men, whereas facet arthropathy may be more prevalent in women [4]. Genetic factors have been suggested to play a major role in determining presence and extent of spine degeneration [5]. Twin studies have shown heritabilities ranging from 52% to 68% for various lumbar disc degeneration phenotypes [6].

The intervertebral disc experiences progressive dehydration as part of the normal aging process. In certain patients, fissures in the anulus fibrosus may develop, causing an inflammatory response. Nociceptive pain fibers may grow into these fissures [7]. Further degeneration may result in progression of the disease or complete annular tears, which may be the source of discogenic low back pain, also referred to as internal disc disruption syndrome. Up to 39% of patients with chronic low back pain may suffer from internal disc disruption [8]. The loss of segmental integrity may lead to further degeneration of the disc, which results in narrowing of the intervertebral disc space. Because of increased loads on the posterior elements, facet degeneration may develop.

The facet (zygapophyseal) joints and sacroiliac joints, like other synovial joints in the body, may develop osteoarthritis [9].

Facet arthropathy may be an independent or concurrent source of low back pain. Further disc degeneration and subsequent loss of disc height may cause subluxation of the facet joints, resulting in degenerative spondylolisthesis, most commonly at the L4-L5 level [10].

Other conditions seen with lumbar degeneration include spondylosis deformans and diffuse idiopathic skeletal hyperostosis. Spondylosis deformans is a degenerative condition marked by formation of anterolateral osteophytes and is mainly a radiologic diagnosis. In spondylosis deformans, the intervertebral spaces are usually well preserved, unlike in degenerative disc disease. The initiating factor in the development of this condition may be degeneration of the anulus fibrosus, primarily in the anterolateral disc space [11]. Spondylosis deformans may become clinically symptomatic if excessive osteophyte formation leads to neural compression, such as in spinal stenosis. Diffuse idiopathic skeletal hyperostosis involves ossification of the ligamentous attachments to the vertebral bones (entheses). Radiologic features consist of multilevel excessive anterior osteophyte formation. Diffuse idiopathic skeletal hyperostosis affects 5% to 10% of patients older than 65 years [12]. This diagnosis is typically an incidental finding on radiologic studies [13].

Other factors associated with lumbar degeneration include environmental, occupational, and psychosocial influences. Environmental influences include cigarette smoking and occupational activities that involve repetitive bending and prolonged exposures to stooping, sitting, or vibrational stresses. These repetitive actions may result in degeneration of the lumbosacral motion segments [12]. Psychosocial factors are well known to contribute to significant disability in low back pain, often in patients with only minimal structural impairment [14].

Symptoms

Lumbar degenerative symptoms range from minor to debilitating. Common complaints include chronic back pain and stiffness. Patients may also report limited range of motion, especially with extension in the case of facet arthropathy or spinal stenosis. Pain with lumbar flexion, coughing, sneezing, or Valsalva maneuver is often associated with disc disease. Should the degenerative changes result in compression of neural structures, patients may develop radicular symptoms into the leg. This can be seen in conditions such as lumbar disc herniations and spinal stenosis.

Lumbar degenerative disease is probably entirely asymptomatic in the majority of cases. Approximately one third of subjects have substantial abnormalities on magnetic resonance imaging despite being clinically asymptomatic [1]. Because of factors not well understood, such as leakage of inflammatory factors from the disc, a chronic pain syndrome may develop in some patients, possibly from repetitive sensitization of nociceptive fibers in the anulus fibrosus [15].

Clinicians should inquire about atypical symptoms of back pain, including night pain, fever, and recent weight loss. These may lead to the diagnosis of malignant neoplasm or infection.

Clinicians should also inquire about symptoms of chronic pain, including sleep disturbances and depression.

Physical Examination

The purpose of the physical examination is to direct further evaluation and therapy toward one of the five most common sources of low back pain: discogenic, facet arthropathy or instability, radiculopathy or neural compression, myofascial or soft tissue, and psychogenic. Combinations of these sources of back pain often exist. A diagnosis based on physical findings will allow the use of advanced diagnostic tests and therapeutic options in the most cost-effective approach.

A standardized low back examination should include assessment of flexibility (lumbosacral flexion, extension, trunk rotation, finger-floor distance, hamstring and iliopsoas range of motion, and hip range of motion). An inclinometer (Fig. 45.1) may assist in standardizing lumbar range of motion measurements [16]. A complete examination includes inspection of lower extremities for atrophy and vascular insufficiency, muscle strength testing, and assessment for sensory abnormalities and their distribution. It is important to note asymmetries in deep tendon reflexes (patellar tendon [L4], hamstring tendon [L5], and Achilles tendon [S1]), which may be the most objective finding. Upper motor neuron signs, such as Babinski and ankle clonus, should also be tested. Functional strength testing should include heel to toe walking, calf and toe raises, single-leg knee bends, and complete gait evaluation. Specific testing for lower back syndromes includes straight-leg raising, femoral stretch sign, dural tension signs, and sacroiliac joint provocative maneuvers (e.g., FABER, Gillet, Yeoman, and Gaenslen tests) as well as specific evaluation techniques, such as the McKenzie technique. Assessment of the patient for nonorganic signs of back pain (Waddell signs; Table 45.1) will help the clinician to recognize patients in whom psychological factors may contribute to the pain syndrome [17].

Functional Limitations

Functional limitations in degenerative diseases of the lumbar spine depend on the anatomic structures involved. All aspects of daily living, including self-care, work, sports activities, and recreation, may be affected.

Symptoms are typically exacerbated during bending, twisting, stooping, and forward flexion in patients with primary discogenic pain. Patients with facet arthropathy or instability report increased pain with extension-based activity, including standing and walking. Pain is often relieved with sitting and other similar forward-flexed positions. Patients with myofascial or soft tissue syndromes report pain that is worsened with static and prolonged physical activity. Symptomatic improvement may be associated with rest and modalities including heat, cold, and pressure. Patients with contributing psychological factors, such as depression and somatization disorders, typically report pain out of proportion to the underlying pathologic process, poor sleep, and significant disability in their daily activities.

Diagnostic Studies

Diagnostic testing is directed by the history and physical examination and should be ordered only if the therapeutic plan will be significantly influenced by the results. Anteroposterior and lateral lumbar spine radiographs are helpful for identifying loss of disc height as a result of disc degeneration, spondylosis or osteophyte formation, spondylolisthesis, scoliosis, and facet arthropathy (Fig. 45.2). Oblique views are helpful to identify spondylolysis. Flexion-extension films are necessary to identify dynamic instability and can assist in the selection of appropriate surgical candidates for fusion procedures. Significant degenerative instability usually does not occur before the age of 50 years, but it should be included in the differential diagnosis in patients with clinical symptoms suggestive of advanced facet arthropathy and disc degeneration [11