Overview

The purpose of this report is to assess, in an evidence-based fashion, the efficacy of methods for the diagnosis and treatment of degenerative lumbar spinal stenosis. Degenerative lumbar spinal stenosis is defined as a focal narrowing of the spinal canal, although there is some variation among investigators about the precise amount of narrowing that must occur before the canal is considered stenotic.

The general term "spinal stenosis" can be applied to three root compression mechanisms alone or in combination:

1. Disk protrusion or herniation.
2. Osteotic overgrowth into the spinal canal or the foramina through which the roots pass laterally.
3. Vertebral slippage or spondylolisthesis.

Although symptoms overlap for these three mechanisms, the second category, osteotic stenosis, is specifically termed spinal stenosis. This category is the focus of this evidence report, with spondylolisthesis also being addressed.

In extreme cases, lumbar stenosis can cause cauda equina syndrome, a syndrome characterized by neuromuscular dysfunction, and may result in permanent nerve damage. Because many studies excluded patients with cauda equina syndrome, we were not able to consider evidence related to it. Therefore, consideration of cauda equina syndrome is beyond the scope of this evidence report. This report focuses on less extreme manifestations of lumbar spinal stenosis and considers the evidence surrounding all aspects of this condition.

Incidence and prevalence data on lumbar spinal stenosis come from several studies. In a Swedish study that defined spinal stenosis as a canal of 11 mm or less, the annual incidence of spinal stenosis observed among patients referred to orthopedic departments was approximately 5 per 100,000 inhabitants.

The National Low Back Pain Study examined records for 2,374 patients with chronic low back pain who sought help from orthopedic surgeons and neurosurgeons at eight academic medical centers across the United States. From this study's data, we calculated that among the patients seeking treatment for low back problems, 35 percent had osteo-related root compression and were possible candidates for bone-removing surgery. However, the severity of disease was not reported in this study. Thus, the proportion of these patients with disease severe enough to indicate surgery is not known.

Additional data from the National Ambulatory Medical Care Survey and the National Spine Network indicate that among patients with low back pain who see a specialist, 13 to 14 percent may have spinal stenosis. The same references also show that among patients with low back pain who see a general physician, 3 to 4 percent may have spinal stenosis.

The longitudinal Framingham Heart Study provides rates of degenerative vertebral slippage. This study found that 1 percent of men and 1.5 percent of women already had vertebral slippage at the baseline measurement at the mean age of 54 years. Over the following 25 years, 11 percent (23/217) of men and 25 percent (100/400) of women developed degenerative vertebral slippage.

Patients with symptomatic spinal stenosis typically have chronic low back pain and pain and weakness in the legs that limit standing and walking to brief durations and short distances. This places limitations on their ability to carry out self-supporting daily activities as well as work, social, and recreational activities. This lack of activity may lead to obesity and general physical deterioration that may eventually result in the onset of cardiovascular and other serious health problems. These activity restrictions may also lead to depression and other psychological problems.

More severe stenosis can result in cauda equina syndrome. A common belief is that untreated spinal stenosis can result in severe symptoms and may become permanent and unresponsive to medical or surgical treatment. However, except for acute onset of symptoms seen among patients with herniated disks, none of the studies that met our inclusion criteria examined how often these consequences occur among patients with lumbar spinal stenosis.

Reporting the Evidence

The present evidence report focuses on nine key questions. These are:

1. What is the relationship between each relevant patient characteristic and the presence and/or intensity of each of the patient signs, symptoms, and conditions of lumbar spinal stenosis?
2. Which relevant patient characteristics are associated with an increased likelihood of focal narrowing of the spinal canal?
3. What is the relationship between the degree of stenosis and the presence and/or intensity of each of the signs, symptoms, and patient conditions?
4. What is the relationship between the signs and symptoms and other features of the patient history and physical and the results of the imaging examination? Implicit in this question is an examination of the criteria for diagnosis of spinal stenosis.
5. What is the relationship between the signs and symptoms and other features of the patient history and physical and the results of conservative treatment; and what is the relationship between the type of conservative treatment and patient outcomes? Implicit in this question is whether any particular patient subgroup benefits from medical management of spinal stenosis.
6. What is the relationship between the signs and symptoms and other features of the patient history and physical and the success or failure of surgical treatment? Implicit in this question is whether any particular patient subgroup benefits from surgical treatment of spinal stenosis and whether some patients might benefit more from surgery than from medical management.
7. What is the relationship between the results of the imaging examination and the success or failure of surgical treatment? Implicit in this question is whether it is possible to predict that a certain patient subgroup will benefit from surgery.
8. What is the relationship between the type of surgery received and the success or failure of surgical treatment?
9. What costs are associated with nonsurgical and surgical treatment of spinal stenosis?

Among the diagnostic imaging methods considered in this report are myelography, computed tomography (CT), and magnetic resonance imaging (MRI). In evaluating these methods, the typical measures used to gauge test performance (sensitivity, specificity, and positive and negative predictive values) were considered. Also examined is whether these diagnostic methods can be used to predict which patients may respond to treatment.

Evaluating the efficacy of diagnostic methods for spinal stenosis is difficult because stenosis is often defined by the imaging findings themselves. Imaging examinations for spinal stenosis are often performed, after medical management has proven unsuccessful, for the purpose of planning surgery. Because there is no evidence to suggest imaging is not necessary for surgical planning, we did not examine this question.

The present evidence report also considers both medical and surgical treatments of spinal stenosis, and our searches for information about both classes of treatments were comprehensive. In our analysis, we pay particular attention to patient-oriented outcomes (i.e., relief of symptoms). This is because outcomes such as surgical reduction or elimination of the stenosis are possible without accomplishing a concomitant reduction in the intensity of symptoms.

Methodology

In order to focus, refine, and arrive at the key questions addressed by this evidence report, a research team comprising five experts in technology assessment developed a preliminary evidence model. This model and written descriptions of the specific issues depicted in it were then discussed in telephone conversations with 11 experts in the field of lumbar spinal stenosis and 1 patient representative. From these conversations a final evidence model was developed. The essential questions of this evidence report were then developed from the evidence model.

To ensure that our identification of information relevant to these key questions was comprehensive, we searched the following databases for information:

• The Cochrane Database of Systematic Reviews (through 2000 Issue 1).
• The Cochrane Registry of Clinical Trials (through 2000 Issue 1).
• The Cochrane Review Methodology Database (through 2000 Issue 1).
• CRISP (through May 2000).
• Cumulative Index to Nursing and Allied Health Literature (CINAHL)® (1988 through November 22, 1999).
• Current Contents®-Clinical Medicine (through May 2000).
• The Database of Abstracts of Reviews of Effectiveness (Cochrane Library) (through 2000 Issue 1).
• Dissertation Abstracts (through February 29, 2000).
• ECRI Library Catalog (through May 2000).
• EMBASE® (Excerpta Medica) (1974 through November 19, 1999).
• Health Care Financing Administration (HCFA) Web site (through May 2000) including:

  • Medicare Provider Analysis and Review (MEDPAR).
  • 1999 National Physician Fee Schedule Payment Amount File.
• Health Devices Alerts® (1977 through May 2000).
• Healthcare Standards (1975 through May 2000).
• Health Devices Sourcebase® (through May 2000).
• Health Services Research Projects (HSRProj) (through February 29, 2000).
• HealthSTAR (Health Services, Technology, Administration, and Research) (1990 through May 20, 2000).
• International Health Technology Assessment (IHTA)® (1990 through May 2000).
• Locator plus (through May 2000).
• MANTIS^TM (through February 4, 2000).
• MEDLINE® (1964 through March 8, 2000).
• National Guideline Clearinghouse^TM (NGC) (through May 2000).
• NHS Economic Evaluation Database (NHS EED) (through May 2000).
• PsycINFO® (1967 through January 17, 2000).
• REHABDATA (through February 2000).
• TARGET^TM (through May 2000).

Search dates generally spanned each database from its inception to July 2000. These searches were supplemented by hand searches of article bibliographies, searches of the gray literature, and searches of the World Wide Web. Key words used as part of the search strategies for the following databases are listed below.

Findings

• Patients with back pain or claudication tend to have narrower spines than asymptomatic patients.
• Increased patient age and the presence of herniated disks may also contribute to the development of back pain and other symptoms of stenosis. The strength of these relationships and the exact ages at which patients are most likely to develop symptoms cannot be determined from the information available.
• Some evidence suggests that disk degeneration, narrowing of the spinal canal, and degenerative changes in the spinal ligaments contribute to stenosis and that instability increases with age. However, the strength of this relationship and the age at which stenosis is most likely to occur cannot be determined from the available information.
• Heavier patients may be more likely to develop the degenerative changes leading to stenosis. Similarly, patients with osteoarthritis of the hips, as well as patients who perform heavy labor, tend to have more disk degeneration than other patients.
• Very little evidence exists correlating degree of narrowing of the lumbar spine with the presence or severity of the signs, symptoms, or conditions associated with stenosis. Difficulties associated with finding such correlations include the presence of large numbers of patients with spinal narrowing and no symptoms, variations in canal size throughout the population, and lack of an accepted system for quantifying the degree of narrowing.
• Only two studies provide numerical evidence of a lack of association between severity of stenosis or spondylolisthesis and severity of back pain. There is some evidence of a relationship between degree of spinal instability and back pain. Among patients with symptomatic stenosis, those with more severe stenosis tend to have more disability.
• Clinical signs and symptoms do not appear to predict whether the results of imaging tests will show severe stenosis.
• Evaluation of conservative treatment trials is complicated by the lack of patient inclusion criteria restricted to lumbar spinal stenosis. Controlled trials specifically examining and reporting on patients with lumbar spinal stenosis who receive conservative treatments are rare.
• Few studies have examined the question of the relationship of initial signs and symptoms to the final status or amount of change following conservative treatment. Studies reporting patient outcomes for conservative treatment vary in their results.
• One well-designed randomized controlled trial (RCT) indicates that local anesthetic block provides temporary relief from neurogenic claudication for about 1 month. Conclusions about effectiveness beyond 3 months cannot be made.
• Evidence for the efficacy of other conservative treatments in lumbar spinal stenosis patients is lacking. However, the lack of evidence for effectiveness does not prove that these treatments are not effective.
• The few studies that did stratify outcomes by patient characteristics, especially those that examined degree of stenosis, did not find a connection between successful treatment and specific patient characteristics.
• The lack of comparable patient groups and pretreatment data is a common problem in evaluating studies that examined both surgical and nonsurgical treatment groups.
• One RCT provides evidence that patients with severe symptoms will benefit more from surgery than conservative therapy.
• In general, data are lacking on the effect of conservative treatment on patients with severe stenosis since these patients seem to receive surgery shortly after diagnosis.
• There is limited, contradictory evidence on whether patients with moderate pain benefit more from surgery or from conservative treatment.
• No published trials provided the data necessary to determine whether the results of an imaging examination will determine the extent of success of surgical treatment.
• We are unable to determine whether imaging results can identify patient groups that would be more or less likely to benefit from surgery.
• The results of two RCTs seem to suggest that instrumentation in addition to fusion does not improve surgical outcomes among patients with spondylolisthesis. However, both trials likely had too few patients (and, therefore, insufficient statistical power) to render any definitive conclusion.
• One study provides evidence that fusion is beneficial compared to decompressive surgery alone.
• Information on the cost of surgical treatment of lumbar spinal stenosis came from several sources. Because present data did not allow us to estimate the effectiveness of any treatment or diagnostic, we were unable to perform a cost-effectiveness analysis.

Future Research

At least some of the gaps in current research on lumbar spinal stenosis seem to arise from the suboptimal designs and incomplete reporting of patient characteristics and results in studies that have been conducted to date. Controlled trials specifically are rare. Our search revealed that only 4 of the 178 studies examining conservative treatments and 7 of the 147 trials examining surgical treatments for lumbar spinal stenosis were RCTs.

The absence of detailed descriptions of patients enrolled in observational studies is another gap in currently available literature. Mean age and duration of illness prior to treatment were the only patient information reported in all four conservative treatment trials; among the surgical trials, only mean age was reported in more than 80 percent of the publications. The lack of detailed reporting of patient signs and symptoms complicates any attempt at correlating them with the extent of recovery after treatment.

Lack of detailed reporting of patient characteristics can sometimes be overcome if studies employ rather restricted patient inclusion criteria. Available information suggests, however, that such criteria were only infrequently applied across studies of lumbar spinal stenosis. For example, although the mean age of patients reported in most studies was between ages 50 and 70, some studies had means outside this range. Variation in age was even greater within studies, where the age ranges often extended to 30 years on either side of the mean.

In addition, in the 15 studies of surgical treatments which reported on whether patients received (and showed no improvement after) a course of conservative treatment, the actual amount of prior conservative treatment reported ranged from as little as 2 weeks to as much as 16 years.

In order to advance patient care in this field, definitive evidence-based statements about the natural history, diagnosis, and treatment of spinal stenosis await the results of well-designed clinical trials. In particular, studies are needed to determine:

• The value of imaging to increase the likelihood of success with either conservative or surgical treatment.
• The proper course of treatment, conservative or surgical, for patients with mild, moderate, or severe symptoms caused by degenerative lumbar stenosis.

Availability of the Full Report

The full evidence report from which this summary was taken was prepared for the Agency for Healthcare Research and Quality by ECRI, under contract No. 290-97-0020. It is expected to be available in late summer 2001. When available, printed copies may be obtained free of charge from the AHRQ Publications Clearinghouse by calling 1-800-358-9295. Requesters should ask for Evidence Report/Technology Assessment No. 32, Treatment of Degenerative Lumbar Spinal Stenosis (AHRQ Publication No. 01-E048).

Internet users will be able to access the report online at http://www.ahrq.gov/clinic/epcix.htm.

AHRQ Publication No. 01-E047
Current as of March 2001

Internet Citation:
Treatment of Degenerative Lumbar Spinal Stenosis. Summary, Evidence Report/Technology Assessment: Number 32. AHRQ Publication No. 01-E047, March 2001. Agency for Healthcare Research and Quality, Rockville, MD. http://hstat.nlm.nih.gov/ftrs/directBrowse.pl?collect=epc&dbName=stenosum

AHRQ Publication No. 01-E047