Lumbar Degenerative Spondylolisthesis

Vincent J. Devlin and Matthew R. Eager

Lumbar degenerative spondylolisthesis is defined as the anterior subluxation of one vertebra relative to the adjacent inferior vertebra in the presence of an intact posterior neural arch. The subluxation results from degenerative changes involving the intervertebral disk and posterior facet joints. As the subluxation increases, secondary hypertrophy of the facet joints and ligamentum flavum contribute to spinal stenosis. The subluxation is usually limited to less than 30% by the intact neural arch and facet joints. Degenerative spondylolisthesis generally occurs in patients greater than 40 years of age. It is more common in females (female-to-male ratio 4:1), blacks (black-to-white ratio 3:1), and diabetic patients. Ninety percent of cases of degenerative spondylolisthesis occur at the L4–L5 level; 10% of cases occur at L3–L4 or L5–S1. Degenerative spondylolisthesis is frequently associated with sacralization of the L5 vertebra.

Classification

Degenerative spondylolisthesis represents a heterogenous process with no universally accepted classification. A variety of factors, including disk space height, segmental motion on flexion-extension radiographs, segmental kyphosis at the level of slip, and the presence/absence of stabilizing osteophytes, have been used to stratify patients into broad treatment groups based on varying definitions of spinal instability.

Workup

History

Physical Examination

Essential components of the physical examination of the patient with suspected lumbar degenerative spondylolisthesis include inspection, palpation, assessment of lumbar range of motion, and a complete neurologic examination, including lower-extremity sensation, motor strength, and reflexes. Physical examination should rule out nonspinal disorders (degenerative hip arthritis, peripheral vascular disease) that may mimic degenerative spondylolisthesis. Hip joint arthrosis may cause buttock and thigh pain that can erroneously be attributed to spinal stenosis. Assessment of hip joint range of motion and the presence of pain at the extremes of motion, especially internal rotation, can determine whether the hip joints are a source of pain and whether hip joint radiographs are indicated. If both hip arthritis and degenerative spondylolisthesis are present, injection of the hip joints under fluoroscopic guidance can aid in sorting out which problem is more symptomatic. Peripheral vascular disease can also cause symptoms of claudication. Assessment of lower-extremity peripheral pulses is an important part of the initial examination of adult patients with spinal disorders. Vascular claudication is associated with increased muscular exertion in the lower extremities independent of trunk position. Symptoms due to vascular claudication typically occur in the distal calf and foot and are not associated with back pain. Generally, these symptoms are exacerbated by walking and are relieved by stopping and standing and not specifically by sitting down or flexing the lumbar spine, as is the case with neurogenic claudication.

Spinal Imaging

Initial imaging studies should include standing anteroposterior (AP) and lateral lumbar radiographs, as well as lateral flexion-extension radiographs. Lumbar magnetic resonance imaging (MRI) is the preferred imaging study for evaluation of the spinal canal for neural compression. In patients who are unable to tolerate MRI (e.g., because of a pacemaker or claustrophobia), a computed tomographic (CT) myelogram is obtained. Parameters to assess on plain radiograph include the degree of subluxation, abnormal mobility at the olisthetic level, segmental kyphosis, and disk space height. In patients who have not undergone prior lumbar spine surgery, degenerative spondylolisthesis presents with a subluxation less than 50% (grade 1 or 2 slippage). Degenerative spondylolisthesis typically results in central spinal stenosis at the level of the subluxation as well as subarticular (zone 1) stenosis with compromise of the traversing nerve root. The exiting nerve root is generally spared from compression unless there is severe loss of disk space height. For example, L4–L5 degenerative spondylolisthesis results in central and subarticular spinal stenosis with compromise of the L5 nerve root (traversing nerve root of the L4–L5 motion segment). The L4 nerve root (exiting nerve root of the L4–L5 motion segment) is generally spared from compression unless severe loss of disk space height results in foraminal narrowing.

Nonsurgical

Nonsurgical treatment options include nonsteroidal anti-inflammatory drugs (NSAIDs), physical therapy, orthoses, and injections. Physical therapy should include aerobic conditioning and exercises that emphasize lumbar flexion. Epidural corticosteroid injections are most likely to be effective for patients with significant lower-extremity symptoms rather than for patients whose predominant symptoms are in the low back.

Surgical

Surgical treatment is considered for patients who fail to improve with nonsurgical management or who present with progressive neurologic deficit, persistent or recurrent leg or back pain, neurogenic claudication, and significant reduction in quality of life. Imaging studies should be consistent with the diagnosis of degenerative spondylolisthesis with spinal stenosis, and the patient should be a medically appropriate candidate for spinal surgery. Surgical treatment options that are commonly considered for degenerative spondylolisthesis include (1) decompression; (2) decompression and posterior spinal fusion without spinal instrumentation; (3) decompression and posterior spinal fusion combined with posterior spinal instrumentation; and (4) decompression, posterior spinal fusion, and posterior spinal instrumentation combined with interbody fusion (anterior or posterior).