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Preface

TheAgency for Healthcare Research and Quality (AHRQ), through its Evidence-BasedPractice Centers (EPCs), sponsors the development ofevidence reports and technology assessments to assist public- andprivate-sector organizations in their efforts to improve the quality of healthcare in the United States.The reports and assessments provide organizations with comprehensive,science-based information on common, costly medical conditions and new healthcare technologies. The EPCs systematically review the relevant scientificliterature on topics assigned to them by AHRQ and conduct additional analyseswhen appropriate prior to developing their reports and assessments.

Tobring the broadest range of experts into the development of evidence reportsand health technology assessments, AHRQ encourages the EPCsto form partnerships and enter into collaborations with other medical andresearch organizations. The EPCs work with thesepartner organizations to ensure that the evidence reports and technologyassessments they produce will become building blocks for health care qualityimprovement projects throughout the Nation. The reports undergo peer reviewprior to their release.

AHRQexpects that the EPC evidencereports and technology assessments will inform individual health plans,providers, and purchasers as well as the health care system as a whole byproviding important information to help improve health care quality.

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

Acting Director JohnM. Eisenberg, M.D.

Centerfor Practice and Director

Technology Assessment Agency forHealthcare Research

Agencyfor Healthcare Research and Quality

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.

Structured Abstract

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

Search strategy. A comprehensive data set was obtained bysearching MEDLINE^Ò,EMBASE^Ò, and 23 additionalelectronic databases; the gray literature; and the World Wide Web and byhand-searching article bibliographies. Date ranges spanned from database inception to July 2000. Our searches yielded 4,788 items forevaluation.

Selectioncriteria. Broad inclusion criteria were used toensure that no relevant information was overlooked. All controlled studies of natural history andconservative treatments, and all clinical studies of any design with relevant quantitativedata on diagnostics and surgical treatment were included in our assessment.

Dataanalysis. Weperformed meta-analyses on combinable data using the standardized differencebetween means (Hedges’ d) as the test statistic andchecked for heterogeneity using the Q test and each study’s standardizedresidual. The Èstatistics, graphical representations, and binomial effect size displays wereused to interpret the results.

Our quantitative analyses of data that did not permit combinationconsisted of performing de novo statistical analyses of published data. Effectsizes (Hedges’ d) were calculated, and statisticalpower analyses were performed.

Mainresults. Ourmeta-analyses, based on the few available studies, suggest that patients withcongenitally narrower spinal canals are more likely to exhibit LSS symptoms andthat patients with symptomatic LSS may have smaller canals. Considerable overlap exists between thespinal diameters of patients with and without LSS diagnoses. Some circumstantial evidence indicates thatthe 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 diagnosticimaging methods or of conservative or surgical treatments for LSS. Evaluation of conservative treatment trialsis complicated by the lack of patient inclusion criteria restricted to lumbarspinal stenosis. Evaluation of specific surgical techniques is difficult because relevantcontrolled studies often used demonstrably different patient groups. Trials that compare conservative to surgicaltreatment also fail to examine patients with similar clinical signs andsymptoms. One randomized controlledtrial provides evidence that patients with severe symptoms will benefit morefrom surgery than conservative therapy. Data from a single cohort study suggest that at one year aftertreatment, patients with moderate pain will benefit more from surgery than fromconservative treatment.

Conclusions. Definitive evidence-based statements about the diagnosis and treatmentof LSS await the results of well-designed clinical trials. Available data imply that patients withnarrower 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 bequantified. Some evidence suggests thatpatients with moderate to severe symptoms will benefit more from surgery thanfrom conservative treatment.

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

ECRI HealthTechnology 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 andQuality; June 2001.

Summary

Overview

The purpose of this report is to assess, in anevidence-based fashion, the efficacy of methods for the diagnosis and treatmentof degenerative lumbar spinal stenosis. Degenerative lumbar spinal stenosis is defined as a focal narrowing of the spinalcanal, although there is some variation among investigators about the preciseamount of narrowing that must occur before the canal is considered stenotic. Thegeneral term “spinal stenosis” can be applied tothree root compression mechanisms alone or in combination: (1) disk protrusionor herniation, (2) osteoticovergrowth into the spinal canal or the foramina through which the roots passlaterally, and (3) vertebral slippage or spondylolisthesis. Although symptoms overlap for these three mechanisms,the second category, osteotic stenosis,is specifically termed spinal stenosis; this categoryis the focus of this evidence report, with spondylolisthesisalso being addressed.

In extreme cases, lumbar stenosiscan cause cauda equinasyndrome, a syndrome characterized by neuromuscular dysfunction, and may resultin permanent nerve damage. Because manystudies excluded patients with cauda equina syndrome, we were not able to consider evidencerelated to it; and, therefore, consideration of caudaequina syndrome is beyond the scope of this evidencereport. This report, therefore, focuseson less extreme manifestations of lumbar spinal stenosisand 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 incidenceof spinal stenosis observed among patients referredto orthopedic departments was approximately 5 per 100,000 inhabitants. The National Low Back Pain Study examinedrecords for 2,374 patients with chronic low back pain who sought help fromorthopedic surgeons and neurosurgeons at eight academic medical centers acrossthe United States. From this study’s data, we calculated thatamong the patients seeking treatment for low back problems, 35 percent had osteo-related root compression and were possible candidatesfor bone-removing surgery. However, theseverity of disease was not reported in this study. Thus, the proportion of these patients withdisease severe enough to indicate surgery is not known.

Additional data from the National AmbulatoryMedical Care Survey and the National Spine Network indicate that among patientswith low back pain who see a specialist, 13 percent to14 percent may havespinal stenosis. The same references also show that among patients with low back pain whosee a general physician, 3 percent to 4 percent may have spinal stenosis.

The longitudinal Framingham Heart Studyprovides rates of degenerative vertebral slippage. This study found that 1percent of men and 1.5 percent of women already had vertebral slippage at thebaseline 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 developeddegenerative vertebral slippage.

Patients with symptomatic spinal stenosis typically have chronic low back pain and pain andweakness in the legs that limit standing and walking to brief durations andshort distances. This places limitationson 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 physicaldeterioration that may eventually result in the onset of cardiovascular andother serious health problems. Theseactivity restrictions may also lead to depression and other psychologicalproblems.

Moresevere stenosis can result in caudaequina syndrome. A common belief is that untreated spinal stenosiscan result in severe symptoms and may become permanent and unresponsive tomedical 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 theseconsequences occur among patients with lumbar spinal stenosis.

Reporting theEvidence

The present evidence report focuses on nine keyquestions. These are:

1. What is the relationship between eachrelevant patient characteristic and the presence and/or intensity of each ofthe patient signs, symptoms, and conditions of lumbar spinal stenosis?

2. Which relevant patient characteristicsare associated with an increased likelihood of focal narrowing of the spinalcanal?

3. What is the relationship between the degreeof stenosis and the presence and/orintensity of each of the signs, symptoms, and patient conditions?

4. What is the relationship between the signsand symptoms and other features of the patient history and physical and theresults of the imaging examination? Implicit in this question is anexamination of the criteria for diagnosis of spinal stenosis.

5. What is the relationship between thesigns and symptoms and other features of the patient history and physical andthe results of conservative treatment; and what is the relationship between thetype of conservative treatment and patient outcomes? Implicit in this question is whether anyparticular patient subgroup benefits from medical management of spinal stenosis.

6. What is the relationship between the signsand symptoms and other features of the patient history and physical and thesuccess or failure of surgical treatment? Implicit in this question is whether any particular patient subgroupbenefits from surgical treatment of spinal stenosisand whether some patients might benefit more from surgery than from medicalmanagement.

7. What is the relationship between the resultsof the imaging examination and the success or failure of surgical treatment? Implicit in this question is whether it ispossible to predict that a certain patient subgroup will benefit from surgery.

8. What is the relationship between the type ofsurgery received and the success or failure ofsurgical treatment?

9. What costs are associated with nonsurgical and surgical treatment of spinal stenosis?

Among the diagnostic imaging methods consideredin this report are myelography, computed tomography(CT), and magnetic resonance imaging (MRI). In evaluating these methods, the typical measures used to gauge testperformance (sensitivity, specificity, and positive and negative predictivevalues) were considered. Also examinedis whether these diagnostic methods can be used to predict which patients mayrespond to treatment. Evaluating theefficacy of diagnostic methods for spinal stenosis isdifficult because stenosis is often defined by theimaging findings themselves. Imagingexaminations for spinal stenosis are often performed,after medical management has proven unsuccessful, for the purpose of planningsurgery. Because there is no evidence tosuggest imaging is not necessary for surgical planning, we did not examine thisquestion.

The present evidence report also considers bothmedical and surgical treatments of spinal stenosis,and our searches for information about both classes of treatments werecomprehensive. In our analysis, we pay particular attention to patient-orientedoutcomes (i.e., relief of symptoms). This is because outcomes such as surgicalreduction or elimination of the stenosis are possiblewithout accomplishing a concomitant reduction in the intensity of symptoms.

Methodology

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

To ensure that our identification ofinformation relevant to these key questions was comprehensive, we searched the following databasesfor information:

The Cochrane Databaseof Systematic Reviews (through 2000 Issue 1)

TheCochrane Registry of Clinical Trials (through 2000 Issue 1)

The Cochrane ReviewMethodology Database (through 2000 Issue 1)

CRISP (through May2000)

Cumulative Index toNursing and Allied Health Literature (CINAHL)^®(1988 through November 22, 1999)

Current Contents^®—ClinicalMedicine (through May 2000)

The Database ofAbstracts of Reviews of Effectiveness (Cochrane Library) (through 2000Issue 1)

DissertationAbstracts (through February 29, 2000)

ECRI Library Catalog(through May 2000)

EMBASE^® (Excerpta Medica) (1974 through November 19, 1999)

Health Care FinancingAdministration (HCFA) Web site (through May 2000) including:

MedicareProvider Analysis and Review (MEDPAR)

1999National 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 ServicesResearch Projects (HSRProj) (through February 29, 2000)

HealthSTAR(Health Services, Technology, Administration, and Research) (1990 through May 20, 2000)

International HealthTechnology Assessment (IHTA)^© (1990 throughMay 2000)

Locatorplus (through May 2000)

MANTISÔ(through February 4, 2000)

MEDLINE^®(1964through March 8, 2000)

National GuidelineClearinghouseÔ (NGC) (through May 2000)

NHS EconomicEvaluation Database (NHS EED) (through May 2000)

PsycINFO^®(1967 through January 17, 2000)

REHABDATA (throughFebruary 2000)

TARGETÔ(through May 2000)

Search dates generally spanned each database from its inception toJuly 2000. These searches weresupplemented by hand searches of article bibliographies, searches of the grayliterature, and searches of the World Wide Web. Key words used as part of the search strategies for the followingdatabases are listed below.

Searches in MEDLINE^®, EMBASE^®, CINAHL^®,Current Contents^®

(presented in PubMedsyntax)

· Lumbarspinal 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)

· Spinalcanal measurement literature key words: Spinal canal/anatomy, histology, spine,anthropometry, spinal (column, canal, diameter, measure)

Searchesin 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 examininghuman subjects. Case reports wereexcluded.

Our literature searches were geared to seekingout articles on a broad range of conservative treatments. These included physical therapy, managementof symptoms with drugs, rigid brace, bed rest, epidural injection of steroidsand/or anesthetics, injection of calcitonin,acupuncture, trigger point treatment, electrical stimulation of nerves ormuscle, facet joint injections of steroids or anesthetics, chiropracticmanipulation, and multidisciplinary approaches. We also searched for studies on a broad range of surgical treatments. These included total radical laminectomy, standard wide decompressivelaminectomy, standard wide decompressivelaminectomy with fusion, standard wide decompressive laminectomy withfusion and instrumentation, partial laminectomy (hemilaminectomy), laminotomy, andforaminectomy.

Our searches yielded 4,788 items that wereevaluated for this project.

To prevent potential biases in this evidencereport, we adopted specific a priori criteria for determining whether we wouldretrieve any article identified by our literature searches. Separate criteria were developed for studiesof conservative treatment, studies of surgical treatment, and studies ofdiagnostic modalities. Disputes werealways resolved in favor of retrieving the full article.

Because the different key questions of thisreport could be answered using different kinds of data, we adopted slightlydifferent criteria to select articles relevant to answering questions aboutnatural history, treatment, and diagnosis. Our criteria were, in general, very broad in order to ensure that we didnot overlook any relevant information.

Patient groups less than 20 years of age wereexcluded to ensure that degenerative lumbar spinal stenosisand not congenital lumbar spinal stenosis was beingexamined. We abstracted only the data ondegenerative conditions when these data were reported separately.

To answer questions about the natural historyof lumbar spinal stenosis, we retrieved all publishedstudies that contained (or purported to contain) measurements of the spinalcanal among patients with lumbar stenosis and alltrials that contained (or purported to contain) measurements of the spinalcanal in normal healthy patients or patients with back pain, regardless ofcause. To be retrieved, studies relevant to the natural history of spinal stenosis had to contain more than 10 patients; or, if thestudy contained more than 1 patient group, it had to contain more than 10patients per group.

Only two general criteria were applied forretrieving articles on diagnosis of spinal stenosis.First, the article had to be on a diagnostic, and second, it had to be onpatients with degenerative lumbar spinal stenosis.

In general, we employed the following criteriafor determining whether an article on conservative treatments or surgery wouldbe retrieved:

· Weretrieved any controlled trial, regardless of whether the trial was randomizedor concurrently controlled.

· Inaddition to controlled trials, we also retrieved any clinical study of surgicaltreatment for lumbar spinal stenosis.

· Onlystudies with at least 10 patients in each arm of the trial were retrieved.

· Studies ofpatients with degenerative spondylolisthesis, alsocalled pseudospondylolisthesis, were included.

Once an article was retrieved, we evaluated thecomparability of the patients in its different groups, the reporting of data,whether results from more than one type of treatment were combined, and whetherresults from patients with different disorders or conditions werecombined. Trials that combined data fromdifferent procedures or from patients with different conditions were notconsidered further.

Data from all articles that met our inclusioncriteria were abstracted using electronic data abstraction forms.

Our analysis of the literature comprisedquestions for which we were able to combine evidence from different studies andquestions with evidence that did not permit such combination. We employed quantitative methods to answerboth types of questions.

For parts of questions 1 and 2, we found datathat permitted us to combine evidence, and we performed meta-analyses toaddress them.

Our quantitative analyses of those questionswith data that did not permit combination consisted of performing de novostatistical analyses of the data published in the relevant articles whereverpossible. Such statistics were eithercomputed from raw data presented in the article or from figures contained inthe article. In some cases, we computedeffect sizes based on the published data.

Findings

_ Patients with back pain or claudicationtend 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.

FutureResearch

At least some of the gaps in current researchon lumbar spinal stenosis seem to arise from thesuboptimal designs and incomplete reporting of patient characteristics andresults in studies that have been conducted to date. Controlled trials specifically are rare; oursearch revealed that only 4 of the 178 studies examining conservativetreatments and 7 of the 147 trials examining surgical treatments for lumbarspinal stenosis were RCTs.

The absence of detailed descriptions ofpatients enrolled in observational studies is another gap in currentlyavailable literature. Mean age andduration of illness prior to treatment were the only patient informationreported 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 patientsigns and symptoms complicates any attempt at correlating them with the extentof recovery after treatment.

Lackof detailed reporting of patient characteristics can sometimes be overcome ifstudies employ rather restricted patient inclusion criteria. Available information suggests, however, thatsuch criteria were only infrequently applied across studies of lumbar spinal stenosis. Forexample, although the mean age of patients reported in most studies was betweenages 50 and 70, some studies had means outside this range. Variation in age was even greater withinstudies, where the age ranges often extended to 30 years on either side of themean.

In addition, in the 15 studies of surgicaltreatments which reported on whether patients received (and showed noimprovement after) a course of conservative treatment, the actual amount ofprior conservative treatment reported ranged from as little as 2 weeks to asmuch as 16 years.

Inorder to advance patient care in this field, definitive evidence-basedstatements about the natural history, diagnosis, and treatment of spinal stenosis await the results of well-designed clinicaltrials. In particular, studies areneeded to determine:

_ the value of imaging to increase the likelihood of successwith 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.