Evidence Report/Technology Assessment

Number 32

Prepared for:
Agency for Healthcare Research and Quality
Department of Health and Human Services
U.S. Public Health Service
2101 East Jefferson Street
Rockville, MD 20852

www.ahrq.gov

Contract No. 290-97-0020

Prepared by:
ECRI, Plymouth Meeting, PA
Health Technology Assessment Group

AHRQ Publication No. 01-E048

June 2001

ISBN 1-58763-051-6
ISSN 1530-4396

This report may be used, in whole or in part, as the basis for development of clinical practice guidelines and other quality enhancement tools, or as a basis for reimbursement and coverage policies. Endorsement by the Agency for Healthcare Research and Quality (AHRQ) or the Department of Health and Human Services (DHHS) of such derivative products may not be stated or implied.

The Agency for Healthcare Research and Quality (AHRQ), through its Evidence-Based Practice Centers (EPCs), sponsors the development of evidence reports and technology assessments to assist public- and private-sector organizations in their efforts to improve the quality of health care in the United States. The reports and assessments provide organizations with comprehensive, science-based information on common, costly medical conditions and new health care technologies. The EPCs systematically review the relevant scientific literature on topics assigned to them by AHRQ and conduct additional analyses when appropriate prior to developing their reports and assessments.

To bring the broadest range of experts into the development of evidence reports and health technology assessments, AHRQ encourages the EPCs to form partnerships and enter into collaborations with other medical and research organizations. The EPCs work with these partner organizations to ensure that the evidence reports and technology assessments they produce will become building blocks for health care quality improvement projects throughout the Nation. The reports undergo peer review prior to their release.

AHRQ expects that the EPC evidence reports and technology assessments will inform individual health plans, providers, and purchasers as well as the health care system as a whole by providing important information to help improve health care quality.

We welcome written comments on this evidence report. They may be sent to: Acting Director, Center for Practice and Technology Assessment, Agency for Healthcare Research and Quality, 6010 Executive Blvd., Suite 300, Rockville, MD 20852.

Acting Director	John M. Eisenberg, M.D.
Center for Practice and Technology Assessment	Director
Agency for Healthcare Research and Quality	Agency for Healthcare Research and Quality

The authors of this report are responsible for its content. Statements in the report should not be construed as endorsement by the Agency for Healthcare Research and Quality or the U.S. Department of Health and Human Services of a particular drug, device, test, treatment, or other clinical service.

This report assesses the clinical evidence describing the natural history, diagnosis, and treatment of degenerative lumbar spinal stenosis (LSS). LSS causes low back pain, radiculopathy, and neurogenic claudication and impedes normal physical activity. LSS is commonly diagnosed in the elderly. Medicare records indicate that the rate of LSS surgery in the United States is between 30 and 132 per 100,000.

A comprehensive data set was obtained by searching MEDLINE, EMBASE, and 23 additional electronic databases; the gray literature; and the World Wide Web and by hand-searching article bibliographies. Date ranges spanned from database inception to July 2000. Our searches yielded 4,788 items for evaluation.

Broad inclusion criteria were used to ensure that no relevant information was overlooked. All controlled studies of natural history and conservative treatments, and all clinical studies of any design with relevant quantitative data on diagnostics and surgical treatment were included in our assessment.

We performed meta-analyses on combinable data using the standardized difference between means (Hedges' d) as the test statistic and checked for heterogeneity using the Q test and each study's standardized residual. The statistics, graphical representations, and binomial effect size displays were used to interpret the results.

Our quantitative analyses of data that did not permit combination consisted of performing de novo statistical analyses of published data. Effect sizes (Hedges' d) were calculated, and statistical power analyses were performed.

Our meta-analyses, based on the few available studies, suggest that patients with congenitally narrower spinal canals are more likely to exhibit LSS symptoms and that patients with symptomatic LSS may have smaller canals. Considerable overlap exists between the spinal diameters of patients with and without LSS diagnoses. Some circumstantial evidence indicates that the development of symptomatic LSS may be influenced by patient age, weight, and occupation and osteoarthritis of the hips.

Definitive conclusions cannot be made about the efficacy of diagnostic imaging methods or of conservative or surgical treatments for LSS. Evaluation of conservative treatment trials is complicated by the lack of patient inclusion criteria restricted to lumbar spinal stenosis. Evaluation of specific surgical techniques is difficult because relevant controlled studies often used demonstrably different patient groups. Trials that compare conservative to surgical treatment also fail to examine patients with similar clinical signs and symptoms. One randomized controlled trial provides evidence that patients with severe symptoms will benefit more from surgery than conservative therapy. Data from a single cohort study suggest that at one year after treatment, patients with moderate pain will benefit more from surgery than from conservative treatment.

Definitive evidence-based statements about the diagnosis and treatment of LSS await the results of well-designed clinical trials. Available data imply that patients with narrower spinal canals may be more likely to develop some symptoms of LSS. The relationship between degree of stenosis and severity of symptoms is unclear and cannot be quantified. Some evidence suggests that patients with moderate to severe symptoms will benefit more from surgery than from conservative treatment.

This document is in the public domain and may be used and reprinted without permission except for copyrighted materials noted for which further reproduction is prohibited without the specific permission of copyright holders. AHRQ appreciates citation as to source and the suggested format is as follows:

ECRI Health Technology Assessment Group. Treatment of Degenerative Lumbar Spinal Stenosis. Evidence Report/Technology Assessment No. 32 (Prepared by ECRI under Contract No. 290-97-0020). AHRQ Publication No. 01-E048. Rockville (MD): Agency for Healthcare Research and Quality; June 2001.

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, and (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; and, therefore, consideration of cauda equina syndrome is beyond the scope of this evidence report. This report, therefore, 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 percent to14 percent may have spinal stenosis. The same references also show that among patients with low back pain who see a general physician, 3 percent 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.

The 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.

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)

Locatorplus (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.

Searches in MEDLINE, EMBASE, CINAHL, Current Contents

(presented in PubMed syntax)

• Lumbar spinal stenosis literature key words: Spinal stenosis, sciatica, backache, spinal diseases, ischialgia, compressive neuropathy, spinal claudication, neurogenic claudication, intermittent claudication, nerve root entrapment, nerve root compression, osteoarthritis, spondylosis, spondylolisthesis, cauda equina, spinal osteophytosis, stenosis (lumbar, exit zone, nerve root canal, foraminal)
• Spinal canal measurement literature key words: Spinal canal/anatomy, histology, spine, anthropometry, spinal (column, canal, diameter, measure)

Searches in PsycINFO

(presented in DIALOG syntax)

• Key words: Back pain (chronic), cauda equina (syndrome, compression), sciatica, lumbago, spondylolisthesis, spinal osteophytosis, stenosis (spinal, lumbar, foraminal, nerve root canal), intermittent neurogenic claudication

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:

• We retrieved any controlled trial, regardless of whether the trial was randomized or concurrently controlled.
• In addition to controlled trials, we also retrieved any clinical study of surgical treatment for lumbar spinal stenosis.
• Only studies with at least 10 patients in each arm of the trial were retrieved.
• Studies of patients with degenerative spondylolisthesis, also called pseudospondylolisthesis, were included.

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.

• 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.

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, and
• the proper course of treatment, conservative or surgical, for patients with mild, moderate, or severe symptoms caused by degenerative lumbar stenosis.