Lumbar spinal stenosis is a common cause of impaired quality of life and diminished functional capacity in the elderly. Due to the advance of noninvasive imaging modalities, spinal stenosis is becoming more frequently identified, and has become the most frequent cause for spinal surgery in patients older than 65 years. Despite the ubiquitous nature of this condition, considerable controversy exists regarding the preferred treatment. Level I evidence that compares the effectiveness of surgical and nonsurgical treatment is lacking. The Spine Patient Outcomes Research Trial, a study that evaluates the common surgical treatments for the lumbar spine, has addressed this deficiency and is discussed in this article.
Lumbar spinal stenosis is a common cause of impaired quality of life and diminished functional capacity in the elderly. With the aging of the United States population, lumbar stenosis will be increasingly diagnosed and treated by primary care physicians and surgical and nonsurgical specialists alike. Because of the advance of noninvasive imaging modalities, spinal stenosis is becoming more frequently identified, and has become the most frequent cause for spinal surgery in patients older than 65 years. The rate of spinal surgery in the Medicare population has increased by 57%, from 2.1 to 3.4 per 1000, between 1988 and 1997, but in addition it has shown tremendous regional variation, both nationally and internationally.
Despite the ubiquitous nature of this condition, considerable controversy exists regarding the preferred treatment, and many commonly used treatments lack high-level evidence regarding their efficacy. A Cochrane database review in 2005 noted that most published articles consisted of uncontrolled case series or prospective cohort studies, and the few randomized trials that have been reported were performed on a small number of patients and reported mixed surgical indications. The current emphasis that is being placed on comparative effectiveness and evidence-based clinical practice has highlighted the need for high-quality data to help guide the treatment of lumbar stenosis patients. In particular, level I evidence comparing the effectiveness of surgical and nonsurgical treatment has been lacking. Recent studies, such as the Spine Patient Outcomes Research Trial (SPORT), have addressed some of these deficiencies and are discussed in this article.
Pathophysiology and clinical presentation
Spinal stenosis can be broadly classified as congenital or acquired (degenerative). Congenital lumbar spinal stenosis is rare, and is caused by a congenital narrowing of the spinal canal, mostly resulting from short pedicles. The anatomic changes responsible for degenerative lumbar spinal stenosis show considerable overlap with those that are seen during the normal aging of the lumbar spinal motion segment. Degeneration is believed to begin in the intervertebral disk where biochemical changes such as cell death and loss of proteoglycan and water content lead to progressive disk bulging and collapse. This process leads to an increased stress transfer to the posterior facet joints, which accelerates cartilaginous degeneration, hypertrophy, and osteophyte formation; this is associated with thickening and buckling of the ligamentum flavum. The combination of the ventral disk bulging and osteophyte formation and the dorsal facet and ligamentum flavum hyptertrophy combine to circumferentially narrow the spinal canal and the space available for the neural elements. This compression of the nerve roots of the cauda equina leads to the characteristic clinical signs and symptoms of lumbar spinal stenosis.
Patients with degenerative spinal stenosis are usually older than 40 years, and present with some combination of back and leg pain. The most specific presentation of lumbar spinal stenosis is neurogenic claudication. Patients develop a burning or aching pain in the lumbar region, buttocks, or lower extremities when in upright posture, and these are often associated with numbness, paresthesias, or subjective weakness. Typically their symptoms are worsened by the extension of the spine, which exacerbates the pathologic narrowing of the spinal canal. Patients report that standing, walking, and climbing stairs will cause symptoms to develop, and that these symptoms can be partially relieved by flexion of the spine, such as sitting or leaning forward (eg, pushing a shopping cart). Impaired walking ability is often an important factor in causing these patients to seek treatment. Neurogenic claudication symptoms must be distinguished from vascular claudication, which can mimic spinal stenosis. Although neurogenic claudication is the most characteristic presentation of lumbar spinal stenosis, not all patients will exhibit this constellation of symptoms. Many will report unilateral or bilateral radicular symptoms rather than true claudication. Neurologic findings on physical examination are unusual, and the diagnosis is generally made based on characteristic subjective complaints coupled with radiographic evidence of spinal canal narrowing from magnetic resonance imaging (MRI), computed tomography (CT), or CT myelography.
Nonsurgical treatment
Although the role of surgery has certainly been debated in the treatment of lumbar spinal stenosis, little high-level evidence is available to recommend specific nonsurgical treatments. In 1987, the Quebec Task Force on Spinal Disorders concluded that no large-sample, randomized controlled trials were available regarding specific conservative treatments for lumbar spinal stenosis. Current nonsurgical treatment largely follows established practice patterns, empiric evidence, and expert opinion. As the symptoms of lumbar stenosis are slowly evolving, a trial of conservative treatment is generally recommended. Commonly used conservative treatments for lumbar spinal stenosis include activity modification, medications, physical therapy, home exercise therapy, and spinal injections.
Activity modification generally consists of the avoidance of those activities that place mechanical stress on the lower back, particularly those that place the spine in extension, as this tends to exacerbate the symptoms. Although high-level evidence is lacking for the direct benefit of physical therapy or exercise for spinal stenosis, most clinicians believe that a program of core strengthening exercise and aerobic conditioning can be of benefit in maintaining functional independence in these patients. Aerobic activities that maintain the spine in a slightly flexed posture, such as recumbent stationary bicycles or elliptical trainers, may be better tolerated by stenosis patients.
Nonsteroidal anti-inflammatory drugs (NSAIDs) are amongst the most commonly used medications for degenerative spinal conditions, particularly acute low back pain. Data demonstrating their efficacy in the long-term treatment of spinal stenosis is lacking. These medications must be used with caution in the elderly because of side effects such as gastrointestinal bleeding or renal insufficiency. Routine screening of renal function is necessary if these drugs are to be used long-term. Similarly, muscle relaxants, which are commonly used in acute low back pain, should have a limited role in the long-term treatment of stenosis. Opioid analgesics have numerous long-term side effects including sedation, constipation, and the potential for dependency. Their use should be limited to controlling acute exacerbations of pain.
Epidural steroid injections (ESIs) may be beneficial in relieving radicular lower extremity symptoms in lumbar spinal stenosis. However, their use remains controversial and evidence regarding their effectiveness is conflicting. Cuckler and associates, in a randomized controlled trial, found no short-term or long-term benefit of epidural injection of methylprednisolone with local anesthetic compared with an injection of saline and local anesthetic. Hoogmartens and Morelle, in a retrospective review of 49 patients with lumbar spinal stenosis treated with epidural steroids, found that only 32% had acceptable pain relief at 2 years. In contrast, Riew and colleagues, in a double-blind, prospective randomized trial, found that 71% of surgical candidates injected with a combination of betamethasone and bupivacaine were able to avoid surgery at 13-month follow-up, as compared with 33% of the patients who received bupivacaine alone. This benefit seemed to be maintained at 5-year follow-up. In general, the limited use of ESI for exacerbations of symptoms are fairly well accepted by clinicians, but few data support the long-term benefit of multiple ESIs over prolonged periods. Their exact role in the treatment of lumbar spinal stenosis awaits further prospective study.
Nonsurgical treatment
Although the role of surgery has certainly been debated in the treatment of lumbar spinal stenosis, little high-level evidence is available to recommend specific nonsurgical treatments. In 1987, the Quebec Task Force on Spinal Disorders concluded that no large-sample, randomized controlled trials were available regarding specific conservative treatments for lumbar spinal stenosis. Current nonsurgical treatment largely follows established practice patterns, empiric evidence, and expert opinion. As the symptoms of lumbar stenosis are slowly evolving, a trial of conservative treatment is generally recommended. Commonly used conservative treatments for lumbar spinal stenosis include activity modification, medications, physical therapy, home exercise therapy, and spinal injections.
Activity modification generally consists of the avoidance of those activities that place mechanical stress on the lower back, particularly those that place the spine in extension, as this tends to exacerbate the symptoms. Although high-level evidence is lacking for the direct benefit of physical therapy or exercise for spinal stenosis, most clinicians believe that a program of core strengthening exercise and aerobic conditioning can be of benefit in maintaining functional independence in these patients. Aerobic activities that maintain the spine in a slightly flexed posture, such as recumbent stationary bicycles or elliptical trainers, may be better tolerated by stenosis patients.
Nonsteroidal anti-inflammatory drugs (NSAIDs) are amongst the most commonly used medications for degenerative spinal conditions, particularly acute low back pain. Data demonstrating their efficacy in the long-term treatment of spinal stenosis is lacking. These medications must be used with caution in the elderly because of side effects such as gastrointestinal bleeding or renal insufficiency. Routine screening of renal function is necessary if these drugs are to be used long-term. Similarly, muscle relaxants, which are commonly used in acute low back pain, should have a limited role in the long-term treatment of stenosis. Opioid analgesics have numerous long-term side effects including sedation, constipation, and the potential for dependency. Their use should be limited to controlling acute exacerbations of pain.
Epidural steroid injections (ESIs) may be beneficial in relieving radicular lower extremity symptoms in lumbar spinal stenosis. However, their use remains controversial and evidence regarding their effectiveness is conflicting. Cuckler and associates, in a randomized controlled trial, found no short-term or long-term benefit of epidural injection of methylprednisolone with local anesthetic compared with an injection of saline and local anesthetic. Hoogmartens and Morelle, in a retrospective review of 49 patients with lumbar spinal stenosis treated with epidural steroids, found that only 32% had acceptable pain relief at 2 years. In contrast, Riew and colleagues, in a double-blind, prospective randomized trial, found that 71% of surgical candidates injected with a combination of betamethasone and bupivacaine were able to avoid surgery at 13-month follow-up, as compared with 33% of the patients who received bupivacaine alone. This benefit seemed to be maintained at 5-year follow-up. In general, the limited use of ESI for exacerbations of symptoms are fairly well accepted by clinicians, but few data support the long-term benefit of multiple ESIs over prolonged periods. Their exact role in the treatment of lumbar spinal stenosis awaits further prospective study.
Surgical treatment
The exact surgical procedure that needs to be performed depends on the exact pathoanatomy of the canal narrowing seen in any given patient. Stenosis can be anatomically classified as central stenosis, lateral recess stenosis, and foraminal stenosis. Central stenosis is the narrowing of the central spinal canal from one edge of the dural tube to the other. Central stenosis most commonly occurs from a disk bulge anteriorly, or hypertrophied or infolded ligamentum flavum, or hypertrophic inferior articular facet posteriorly. Lateral recess stenosis is narrowing in the subarticular recess, bounded by the takeoff of the nerve root from the dural tube to the medial border of the pedicle. Lateral recess stenosis is most commonly caused by hypertrophy of the superior articular facet or the lateral insertion of the ligamentum flavum where it merges with the articular facet capsule. Again, an anteriorly bulging disk can contribute to lateral recess stenosis. Foraminal spinal stenosis occurs in the neuroforamen itself, bounded by the disk and vertebral endplate margins anteriorly, the pars interarticularis posteriorly, and the pedicles superiorly and inferiorly. Compression of the nerve root in the neuroforamen is most commonly caused by a combination of a bulging disk and rostral-caudal collapse of the pedicles due to disk degeneration and collapse. Compression of the neural elements can occur in one or several of the anatomic zones.
Standard surgical treatment of lumbar spinal stenosis consists of a decompressive lumbar laminectomy. Laminectomy begins with removal of the respective spinous process and supraspinous and interspinous ligaments to gain access to the interlaminar space in the midline. The lamina is then thinned with a rongeur or high-speed drill followed by removal using various Kerrison rongeurs. Removal of the hypertrophic ligamentum flavum then follows. The ligamentum flavum is carefully detached from the leading edge of the lamina below and from the undersurface of the lamina above. It is then removed using Kerrison rongeurs. The removal of lamina and ligamentum is carried laterally out to the level of the lateral recess, where the medial border of the pedicle can be palpated from within the canal using a curved ball-tipped probe. A partial medial facetectomy is then performed. The medial one-third to half of the facet is removed using 45°-angled Kerrison rongeurs. Finally, decompression of the nerve root in the neuroforamen can be performed with small (eg, 2 mm) Kerrison rongeurs. On completion of the decompression, a 3- to 4-mm curved ball-tipped probe should pass easily into the subarticular recess and then the neuroforamen, following the course of the nerve root as it exits the spinal canal. If the area of compression is more limited on preoperative imaging studies, a more limited procedure such as a unilateral partial laminotomy and foraminotomy can be performed.
Two surgical techniques that deserve mention at this point are spinal fusion and interspinous process devices. The indications to perform spinal fusion in combination with laminectomy are controversial and are beyond the scope of this article. In general, spinal fusion is indicated in situations whereby spinal instability is preexisting at the time of surgical decompression and decompression is likely to make instability worse, or in situations whereby the decompressive procedure is likely to induce postoperative instability. Interspinous process devices (eg, X-STOP [Kyphon Inc, Sunnyvale, CA, USA], Wallis [Abbott Spine Inc, Austin, TX, USA], or DIAM [Medtronic Sofamor Danek Inc, Memphis, TN, USA]), have recently emerged as an alternative to decompressive procedures such as laminectomy. These devices are designed to act as a block to hypertension posteriorly at the level of the facet, to prevent exacerbation of canal narrowing during extension postures of the spine. A recent prospective randomized trial suggests that the use of one of these devices is superior to conservative care in the treatment of symptomatic lumbar spinal stensosis. Interspinous process devices are a promising technology in the treatment of lumbar spinal stenosis, but their exact indications and role in the treatment of stenosis remain to be seen.
Evidence for surgical treatment of spinal stenosis
The literature regarding the surgical treatment of lumbar spinal stenosis has shown an evolution from uncontrolled case series to prospective randomized trials comparing surgical with nonoperative treatment (ie, SPORT). Several of these studies are outlined in Table 1 . Their side-by-side comparison is not designed to directly compare the merits of one study to another, but is meant to illustrate the evolution and natural progression of the literature associated with the surgical treatment of spinal stenosis.
| References | Study Design | Main Findings | Strengths | Weaknesses | Level of Evidence |
|---|---|---|---|---|---|
| Verbiest J Bone Joint J Surg, 1977 | Retrospective case series | Two-thirds experience relief |
|
| IV |
| Johnsson et al Spine, 1991 | Retrospective cohort and natural history study |
|
|
| IV |
| Katz et al J Bone Joint Surg, 1991 Spine, 1996 | Retrospective case series |
|
|
| IV |
| Herno et al Spine, 1993 | Retrospective case series |
|
|
| IV |
| Airaksinen et al Spine, 1997 | Retrospective case series |
|
|
| IV |
| Cornefjord et al Eur Spine J, 2000 | Retrospective case series |
|
|
| IV |
| Jönsson et al Spine, 1997 | Prospective cohort study |
|
|
| II |
| Atlas et al Spine, 1996 Spine, 2000 Spine, 2005 | Prospective observational (nonrandomized) study |
|
|
| II |
| Amundsen et al Spine, 2000 | Prospective, Partial randomization |
|
|
| II |
| Mariconda et al J Spinal Disord, 2002 | Prospective, partial randomization |
|
|
| II |
| Athiviraham & Yen Clin Orthop Relat Res, 2007 | Prospective, observational (nonrandomized) study |
|
|
| II |
| Malmivaara et al Spine, 2007 | Prospective randomized, controlled trial |
|
|
| I |
| Weinstein et al N Engl J Med, 2008 | Prospective, randomized controlled trial |
|
|
| I |
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