Under its Evidence-based Practice Program, the Agency for Healthcare Research and Quality (AHRQ) is developing scientific information for other agencies and organizations on which to base clinical guidelines, performance measures, and other quality improvement tools. Contractor institutions review all relevant scientific literature on assigned clinical care topics and produce evidence reports and technology assessments, conduct research on methodologies and the effectiveness of their implementation, and participate in technical assistance activities.
Overview / Reporting the Evidence / Methodology / Findings / Future Research / Availability of the Full Report
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:
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.
Return to ContentsThe present evidence report focuses on nine key questions. These are:
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.
Return to ContentsIn 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:
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.
Searches were restricted to studies examining human subjects. Case reports were excluded.
Our literature searches were geared to seeking out articles on a broad range of conservative treatments. These included physical therapy, management of symptoms with drugs, rigid brace, bed rest, epidural injection of steroids and/or anesthetics, injection of calcitonin, acupuncture, trigger point treatment, electrical stimulation of nerves or muscle, facet joint injections of steroids or anesthetics, chiropractic manipulation, and multidisciplinary approaches.
We also searched for studies on a broad range of surgical treatments. These included total radical laminectomy, standard wide decompressive laminectomy, standard wide decompressive laminectomy with fusion, standard wide decompressive laminectomy with fusion and instrumentation, partial laminectomy (hemilaminectomy), laminotomy, and foraminectomy.
Our searches yielded 4,788 items that were evaluated for this project.
To prevent potential biases in this evidence report, we adopted specific a priori criteria for determining whether we would retrieve any article identified by our literature searches. Separate criteria were developed for studies of conservative treatment, studies of surgical treatment, and studies of diagnostic modalities. Disputes were always resolved in favor of retrieving the full article.
Because the different key questions of this report could be answered using different kinds of data, we adopted slightly different criteria to select articles relevant to answering questions about natural history, treatment, and diagnosis. Our criteria were, in general, very broad in order to ensure that we did not overlook any relevant information.
Patient groups less than 20 years of age were excluded to ensure that degenerative lumbar spinal stenosis and not congenital lumbar spinal stenosis was being examined. We abstracted only the data on degenerative conditions when these data were reported separately.
To answer questions about the natural history of lumbar spinal stenosis, we retrieved all published studies that contained (or purported to contain) measurements of the spinal canal among patients with lumbar stenosis and all trials that contained (or purported to contain) measurements of the spinal canal in normal healthy patients or patients with back pain, regardless of cause. To be retrieved, studies relevant to the natural history of spinal stenosis had to contain more than 10 patients; or, if the study contained more than 1 patient group, it had to contain more than 10 patients per group.
Only two general criteria were applied for retrieving articles on diagnosis of spinal stenosis. First, the article had to be on a diagnostic, and second, it had to be on patients with degenerative lumbar spinal stenosis.
In general, we employed the following criteria for determining whether an article on conservative treatments or surgery would be retrieved:
Once an article was retrieved, we evaluated the comparability of the patients in its different groups, the reporting of data, whether results from more than one type of treatment were combined, and whether results from patients with different disorders or conditions were combined. Trials that combined data from different procedures or from patients with different conditions were not considered further.
Data from all articles that met our inclusion criteria were abstracted using electronic data abstraction forms.
Our analysis of the literature comprised questions for which we were able to combine evidence from different studies and questions with evidence that did not permit such combination. We employed quantitative methods to answer both types of questions.
For parts of questions 1 and 2, we found data that permitted us to combine evidence, and we performed meta-analyses to address them.
Our quantitative analyses of those questions with data that did not permit combination consisted of performing de novo statistical analyses of the data published in the relevant articles wherever possible. Such statistics were either computed from raw data presented in the article or from figures contained in the article. In some cases, we computed effect sizes based on the published data.
Return to ContentsAt 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 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. Printed copies of the report 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).
The Evidence Report is also online on the National Library of Medicine Bookshelf (select for Volume I and Volume II). The report can also be downloaded as a zipped file.
AHRQ Publication Number 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://www.ahrq.gov/clinic/epcsums/stenosum.htm
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