Spine J (N American Spine Soc) 2004 (May); 4 (3): 335–356 ~ FULL TEXT
Gert Bronfort PhD, DC, Mitchell Haas DC, MA,
Roni L. Evans DC, MS, and Lex M. Bouter PhD
Department of Research,
Wolfe-Harris Center for Clinical Studies,
Northwestern Health Sciences University,
2501 W, 84th Street
Bloomington, MN 55431, USA.
The authors categorized 43 randomized controlled trials to assess the efficacy of spinal manipulative therapy (SMT) for back and neck pain. Overall, there was limited to moderate evidence (depending on the study) that spinal manipulative treatment for both chronic and acute lower back pain was more effective and provided more short-term relief than many other types of care, including prescription drugs, physical therapy and home exercise. There was moderate evidence that spinal mobilization was superior to physical therapy and some medical regimens for some types of neck pain. The data synthesis in the study suggests that recommendations can be made with some confidence regarding the use of SMT and/or mobilization as a viable option for the treatment of both low back pain and neck pain.
BACKGROUND CONTEXT: Despite the many published randomized clinical trials (RCTs), a substantial number of reviews and several national clinical guidelines, much controversy still remains regarding the evidence for or against efficacy of spinal manipulation for low back pain and neck pain.
PURPOSE: To reassess the efficacy of spinal manipulative therapy (SMT) and mobilization (MOB) for the management of low back pain (LBP) and neck pain (NP), with special attention to applying more stringent criteria for study admissibility into evidence and for isolating the effect of SMT and/or MOB.
STUDY DESIGN: RCTs including 10 or more subjects per group receiving SMT or MOB and using patient-oriented primary outcome measures (eg, patient-rated pain, disability, global improvement and recovery time).
METHODS: Articles in English, Danish, Swedish, Norwegian and Dutch reporting on randomized trials were identified by a comprehensive search of computerized and bibliographic literature databases up to the end of 2002. Two reviewers independently abstracted data and assessed study quality according to eight explicit criteria. A best evidence synthesis incorporating explicit, detailed information about outcome measures and interventions was used to evaluate treatment efficacy. The strength of evidence was assessed by a classification system that incorporated study validity and statistical significance of study results. Sixty-nine RCTs met the study selection criteria and were reviewed and assigned validity scores varying from 6 to 81 on a scale of 0 to 100. Forty-three RCTs met the admissibility criteria for evidence.
Acute LBP: There is moderate evidence that SMT provides more short-term pain relief than MOB and detuned diathermy, and limited evidence of faster recovery than a commonly used physical therapy treatment strategy.
Chronic LBP: There is moderate evidence that SMT has an effect similar to an efficacious prescription nonsteroidal anti-inflammatory drug, SMT/MOB is effective in the short term when compared with placebo and general practitioner care, and in the long term compared to physical therapy. There is limited to moderate evidence that SMT is better than physical therapy and home back exercise in both the short and long term. There is limited evidence that SMT is superior to sham SMT in the short term and superior to chemonucleolysis for disc herniation in the short term. However, there is also limited evidence that MOB is inferior to back exercise after disc herniation surgery.
Mix of acute and chronic LBP: SMT/MOB provides either similar or better pain outcomes in the short and long term when compared with placebo and with other treatments, such as McKenzie therapy, medical care, management by physical therapists, soft tissue treatment and back school.
Acute NP: There are few studies, and the evidence is currently inconclusive.
Chronic NP: There is moderate evidence that SMT/MOB is superior to general practitioner management for short-term pain reduction but that SMT offers at most similar pain relief to high-technology rehabilitative exercise in the short and long term.
Mix of acute and chronic NP: The overall evidence is not clear. There is moderate evidence that MOB is superior to physical therapy and family physician care, and similar to SMT in both the short and long term. There is limited evidence that SMT, in both the short and long term, is inferior to physical therapy.
CONCLUSION: Our data synthesis suggests that recommendations can be made with some confidence regarding the use of SMT and/or MOB as a viable option for the treatment of both low back pain and NP. There have been few high-quality trials distinguishing between acute and chronic patients, and most are limited to shorter-term follow-up. Future trials should examine well-defined subgroups of patients, further address the value of SMT and MOB for acute patients, establish optimal number of treatment visits and consider the cost-effectiveness of care.
From the FULL TEXT Article:
More than 50 mostly qualitative, nonsystematic reviews
have been published since 1979 addressing the role of spinal
manipulation and mobilization in the treatment of back and
neck pain (NP).  A majority of these reviews, including
most of the systematic reviews [2–7], have concluded that
spinal manipulation is an efficacious treatment for low back
pain (LBP).  However, most reviews restricted their positive
conclusions to patients with acute LBP. 
A number of scales and checklists have been developed
to assess the quality of randomized clinical trials (RCTs).  In general, positive or negative trial outcomes have been
accepted at face value without consideration of the magnitude
of the differences among interventions. A shortcoming
of this approach is exemplified by reevaluations of individual
RCTs on the efficacy of spinal manipulation, where it was
found that the data supported conclusions that were in conflict with those of the original publications. 
Our reevaluation of the literature follows from a previous
systematic review of reviews , in which the authors
observed that the vast majority of the reviews of spinal
manipulation for LBP were of inadequate methodological
quality. Furthermore, the authors identified a need to develop
standards of quality for systematic reviews in general, which
was emphasized in an accompanying editorial by Moher
and Olkin.  The methodology used in this review is
intended as a step in that direction. Using a stringent best
evidence synthesis method, we reviewed the literature and
contrasted our findings with other recent systematic reviews
on the efficacy of spinal manipulation and mobilization for
back and neck pain. [11, 12]
The purpose of this review is to reassess the efficacy of
spinal manipulative therapy (SMT) and mobilization (MOB)
for the management of LBP and NP, with special attention
to applying more stringent criteria for study admissibility
into evidence and for isolating the effect of SMT and/or
SMT is defined as the application of high-velocity, lowamplitude
manual thrusts to the spinal joints slightly beyond
the passive range of joint motion.  MOB is defined as
the application of manual force to the spinal joints within the
passive range of joint motion that does not involve a thrust.
A literature search for all RCTs evaluating the therapeutic
efficacy of SMT and/or MOB for LBP and NP was performed
accessing MEDLINE (1966 to end of 2002), Embase
(1974 to end of 2002), CINAHL and the chiropractic reference
systems CRAC and MANTIS. Articles in English,
Danish, Swedish, Norwegian and Dutch reporting on randomized
trials were identified by a comprehensive search
of computerized and bibliographic literature databases. The
search strategy was based on combinations of the main
keywords: manipulation, spinal; low back pain; cervical
vertebrae; manipulation/orthopedic, randomized controlled
trials, comparative study, review literature, chiropractic
Each study had to have 10 or more subjects receiving
SMT and/or MOB to be included in this review. The main
outcome measures had to be explicitly patient oriented (eg,
patient-rated pain, global improvement, low back or neck
disability, recovery time, work loss, medication use and
functional health status). Additionally, citation tracking of
references in relevant publications was used, including the
nonindexed chiropractic, osteopathic, physical therapy and
medical journals. Abstracts from proceedings and unpublished
trials were not included.
Data abstraction and synthesis
A best evidence synthesis incorporating explicit information
about outcome measures, interventions and magnitude
of treatment differences and their associated p values was used
to evaluate treatment efficacy. [12, 14, 15] Two authors (MH
and GB) independently extracted and recorded relevant data
from each article. Statistical pooling was considered to be
an adjunct to the systematic review and not the primary goal.
All original data on outcomes were normalized to a 0–100
percentage-point scale whenever possible. Between-group
differences are reported in the text in percentage points on
the 100–point scale.
Categorization of low back and neck pain
Studies were classified into six categories: acute LBP,
chronic LBP, mix of acute and chronic LBP, acuteNP, chronic
NP, and mix of acute and chronic NP. For the purpose of
this review, acute was defined as a duration of less than 6
weeks, and chronic as a duration of 6 weeks or longer.
Categorization of short-term and long-term outcomes
Short-term follow-up was defined as outcomes evaluated
up to 3 months after the initial study treatment. Long-term
follow-up was defined as outcomes evaluated more than 3
months after onset of study therapy.
Assessment of methodological quality of RCTs
A critical evaluation list of eight methodological items
and their operational definitions (see Appendix) was used
to assess methodological quality and represents a modification
of previously used instruments. [16, 17] The quality
scores for this review were well correlated (r = 0.80) with
scores from a 14–item scoring system used in a previous
review.  The quality score items included concealment
of treatment allocation, blinding of patients, blinding of
provider and control of attention bias, blinding of assessor
and influence by study personnel, similarity of study groups at
baseline, dropouts accounted for, missing data accounted for
and intention-to-treat analysis. Two reviewers performed the
methodological scoring of the RCTs independently (MH
and GB). Differences in scores were resolved by consensus
between the two reviewers. Two other authors of this review
scored the trials for which GB was the primary author. The
reviewers could not be blinded to study results because of
their familiarity with the literature. The validity scores
of the individual RCTs were used as part of the evidence
Assessment of the level of evidence of efficacy
The criteria for determining the level of evidence of efficacy
was adapted from the Agency for Health Care Policy
and Research’s guidelines for acute low back pain.  Our
system evaluated the evidence by taking into account the
1) the type of comparison intervention (established efficacious treatment, commonly used therapy or placebo),
2) methodological quality as expressed by validity scores,
3) the number of studies and
4) statistical significance of study findings.
Four (4) categories were used to describe evidence
levels: strong, moderate, limited and inconclusive. All
eligible RCTs were considered regardless of their results.
Statistical pooling of two or more trials was considered
if they were homogeneous in terms of patient population,
interventions, outcomes and follow-up time points. For determination
of the outcome of each RCT, we prioritized
patient-rated pain, disability and improvement.
The assessment of efficacy depended on the type of comparison
intervention. To be declared evidence of efficacy, a
study was required to show that SMT and/or MOB had at
least a similar magnitude of effect compared with an established
efficacious treatment or was superior to a placebo
or a commonly used therapy. To be declared evidence of
inefficacy, a study had to show that SMT was inferior to an
established efficacious treatment, commonly used therapy
or showed an effect similar or inferior to a placebo intervention
or no-treatment control. For the purpose of this review,
adequate statistical power was defined as at least 80% power
to detect a group difference in effect size of 0.5 and an alpha
level of .05. A group difference in effect size of <0.5 or
<10 percentage points on the primary outcome measure
was defined as representing a similar effect. Methodological
quality and statistical significance were then considered to
determine the evidence level, as defined in Table 1. Studies
with strong, moderate, or limited evidence are tabulated in
the evidence of efficacy summary tables. Studies with only
inconclusive evidence were omitted from these tables (i.e.,
underpowered studies with statistically insignificant findings
or studies with validity scores <20).
There is one additional assessment of evidence. When
SMT is found to have similar effect to a commonly used
therapy without established efficacy, neither efficacy nor
inefficacy can be established. Furthermore, no study tested
equivalence. Therefore, we called this case evidence of similarity
of effect to distinguish the evidence from efficacy,
inefficacy and equivalence.
Exclusion from evidence
An RCT was excluded from evidence synthesis under
the following conditions:
1) the main outcome measure was not rated by the patient;
2) quantitative information on the main outcome was lacking;
3) the trial was designed to test the immediate postintervention effect of a single therapeutic session without a follow-up period;
4) SMT and/or MOB was combined with other therapies not allowing us to isolate its unique contribution to the overall treatment effect.
We identified 46 LBP trials of SMT/MOB. Of these, 31
studies with a total of 5,202 participants met the inclusion
SMT was investigated in 25 trials, MOB in 3 trials and
a combination in 3 trials. Chiropractors in 14 trials, medical
doctors in 7 trials, physical therapists in 6 trials and osteopaths
in 4 trials provided SMT/MOB.
included acupuncture, back school, bed rest, corset, diathermy,
education advice, electrical modalities, exercise,
heat, injections, massage and trigger point therapy, medication,
no treatment, placebo, physical therapy, sham SMT
and ultrasound. The number of treatments varied from 1 to
24, and outcomes were measured from immediate posttreatment
to 3 years after commencement of therapy. Among the
studies in evidence, 6 trials (N = 662) evaluated acute LBP,
11 trials (N = 1,472) assessed chronic LBP and 14 trials
(N = 3,068) investigated a mix of acute and chronic LBP
patients. The methodological qualities of the LBP RCTs are
shown in Table 2. The 15 LBP studies excluded from
evidence and the reasons for ineligibility are summarized
in Table 3. The primary exclusion criterion was the inability
to isolate a unique contribution of SMT/MOB to the treatment
The LBP RCTs were divided into three subcategories:
acute, chronic and a mix of acute and chronic. They were
too dissimilar in terms of patient characteristics, outcome
measures, time points and type of treatment comparisons to
allow for statistical pooling. Whenever RCT group differences
did not show statistical significance, they were termed
Fifteen RCTs were identified. Six remained in evidence
(Table 4) [20–25], and 9 were excluded [26–34] (Table 3)
Hadler et al.  (validity score [VS], 69) showed that
one session of SMT was superior to one session of MOB.
Glover et al.  (VS, 50) found one session of SMT to
be superior to detuned diathermy 1 week after treatment.
MacDonald and Bell  (VS, 38) found that SMT was
nonsignificantly better than low back education in a subgroup
of patients 1 week after the start of treatment. Farrell
and Twomey  (VS, 25) showed that patients receiving
SMT recovered faster than patients receiving a combination
of diathermy, exercise and ergonomic instruction. Mathews
et al.  (VS, 19) found that patients with LBP accompanied
by sciatica improved faster with SMT than with heat
after 2 weeks of treatment. Godfrey et al.  (VS, 19)
found SMT combined with low-level electrical stimulation
was nonsignificantly better in terms of pain reduction than
than low-level electrical stimulation alone after 2 weeks.
Evidence of efficacy
There is moderate evidence that SMT has better shortterm
efficacy than spinal mobilization and detuned diathermy.
There is limited evidence that SMT has better short-term
efficacy than a combination of diathermy, exercise and ergonomic
instruction (Table 5).
Fifteen RCTs on chronic LBP were identified, of which
11 evaluated SMT and/or MOB in isolation (Table 6) [35–48] Four RCTs were excluded from evidence (Table 3). [49–52]
Bronfort et al.  (VS, 81) showed that the combination
of SMT and exercise was similar in effect to the combination
of nonsteroidal anti-inflammatory drugs (NSAIDs) and
exercise. Hemmila¨ et al.  (VS, 63) found that SMT
resulted in greater short- and long-term disability reduction
than home back exercise or physical therapy (PT). SMT was
superior to PT for pain in the long term. Koes et al. [39, 40] (VS, 50) showed SMT/MOB to have an advantage
over general medical practice and placebo for severity of
main complaint and perceived global improvement in the
long term. Burton et al.  (VS, 38) showed that SMT had
a higher short-term reduction in pain and disability for disc
herniation than chemonucleolysis. Pope et al. [37, 38] (VS,
38) found SMT superior to transcutaneous electrical nerve
stimulation (TENS) in pain improvement.Waagen et al. 
(VS, 38) reported an advantage of SMT over placebo in
pain reduction after 2 weeks of treatment. Gibson et al. 
(VS, 38) found detuned diathermy better than SMT/MOB
and active diathermy. Baseline dissimilarity between groups
rendered the results of this trial questionable. Triano et al.  (VS, 31) showed SMT had more short-term pain and
disability reduction than sham SMT. Coxhead et al. 
(VS, 25), showed SMT was superior to traction, exercise,
corset and no treatment in the short term. Timm  (VS, 25)
found MOB resulted in slightly more short-term disability
reduction than PT and no-treatment control. Exercise resulted
in more disability reduction than MOB. Herzog et al.  (VS, 6) found no significant short-term differences
between SMT, back education and exercise in pain and
Evidence of efficacy
There is moderate evidence that SMT with strengthening
exercise is similar in effect to prescription NSAIDs with
exercise for pain relief in both the short and long term. There
is moderate evidence that SMT/MOB is superior to physical
therapy and to home exercise for reducing disability in the
long term. There is moderate evidence that SMT/MOB is
superior to general practice medical care and to placebo in
the short term, and superior to physical therapy in the
long term for patient improvement. There is limited evidence
in the short term for the following: that in terms of pain/
disability reduction, SMT/MOB is superior to physical
therapy, home back exercise, TENS, traction/exercise/corset,
no treatment and placebo; also in the short term, that SMT
is superior to sham SMT and chemonucleolysis and that
MOB is inferior to exercise for disc herniation (Table 7).
Mix of acute and chronic low back pain
Sixteen trials were identified. Fourteen met the criteria
for admissibility (Table 8) [53–67]. Two trials were excluded
(Table 3). [68, 69]
Hurwitz et al. [53, 144] (VS, 63) foundSMT almost identical
to medical care for pain and disability in the short and
long term. Adding the use of physical modalities to SMT
did not improve any outcomes. Hsieh et al.  (VS, 63)
found a nonsignificant advantage for SMT over myofascial
therapy and for back school over SMT in terms of pain and
disability reduction. Cherkin et al.  (VS, 50) found a
short-term advantage of SMT over a booklet, and no difference
between SMT and McKenzie therapy for pain in the
short term. Skargren et al. [58, 59] (VS, 50) showed equal
effectiveness for SMT and PT in terms of pain and disability
reduction in the short and long term. Andersson et al. 
(VS, 50) found a small but nonsignificant short-term benefit
of SMT over standard medical care for pain and no difference
for disability. Meade et al. [56, 57] (VS, 31) showed a small,
significant advantage of SMT over hospital outpatient management
for disability in the short and long term. Bronfor  (VS, 31) showed that SMT was nonsignificantly better
than medical general practice in improvement and sick leave,
both in the short and long term. Zylbergold and Piper 
(VS, 38) found that SMT and heat were nonsignificantly
better than flexion exercise and heat for pain and disability.
Giles and Muller  (VS, 31) found nonsignificantly
more pain and disability reduction favoring SMT after 3
to 4 weeks of treatment compared with acupuncture and
medication. Doran and Newell  (VS, 25), showed that
SMT resulted in greater improvement than physiotherapy,
corset or analgesics after treatment. No important differences
were seen subsequently. Hoehler et al.  (VS, 25) found
a nonsignificant but greater pain reduction for SMT than
placebo massage. A significantly higher proportion in the
SMT group reported effective treatment. Evans et al. 
(VS, 19) found a substantially higher proportion of patients
receiving SMT than patients receiving analgesics rated
treatment effective. The advantage in pain reduction for SMT
was nonsignificant. Wreje et al.  (VS, 13) found that
one session of SMT produced a lower number of sick-leave
days than friction massage. Postacchini  (VS, 6) showed
greater global improvement for SMT than for placebo ointment.
Other comparisons had ambiguous results.
Evidence of efficacy
There is moderate evidence that SMT is superior to an
information booklet for pain reduction in the short term, but
similar in the long term. There is also moderate evidence
in the short and long term that SMT is similar to the following
for pain and/or disability: McKenzie therapy, medical care
with instruction in exercise, soft tissue therapy, physical
therapy and back school. SMT is similar to medical care
in the short term. There is limited evidence of short- and
long-term superiority of SMT over hospital outpatient care
for pain and disability. There is limited evidence of shortterm
superiority of SMT over medication and placebo massage
We identified 23 NP trials of SMT/MOB. Of these, 12
studies with a total of 1,172 participants met the inclusion
criteria. SMT was investigated in 7 trials, MOB in 4 trials
and a combination in 1 trial. Therapy was provided by a
doctor of chiropractic in 5 trials, a medical doctor in 2 trials,
a physical therapist in 4 trials and a manual therapist in 1
trial. Comparison therapies included acupuncture, collar, education,
electrical exercise, heat, modalities, medication, no
treatment, physical therapy, placebo and rest. The number of
treatments varied from 1 to 24, and outcomes were evaluated
from immediately after the first treatment to 1 year after
commencement of therapy. Among the studies in evidence,
2 trials (N=82) evaluated acute NP, 5 trials (n=444) assessed
chronic NP and 5 trials (n646) investigated a mix of acute
and chronic LBP patients. The methodological qualities of
the NP RCTs are shown in Table 10. The 11 NP studies
excluded from evidence and the reasons for ineligibility are
summarized in Table 11. The primary exclusion criterion
was the inability to isolate a unique contribution of SMT/
MOB to the treatment effect.
The NP RCTs were divided into three subcategories:
acute, chronic and a mix of acute and chronic. They were
too dissimilar in terms of patient characteristics, outcome
measures, time points and type of treatment comparisons to
allow for statistical pooling. Whenever RCT group differences
did not show statistical significance, they were termed
Five trials involving MOB or SMT were identified. Two
met the criteria for admissibility (Table 12) [71, 72], and
three trials were excluded (Table 11). [73–75]
Nordemar and Thorner  (VS, 44) found a regimen with
MOBwasnonsignificantly better thanthe regimenwithoutMOB
in the short term for pain. MOB was no better than TENS. Howe et al.  (VS, 19) observed a higher proportion of
patients receiving SMT experienced short-term pain improvement
after the first treatment than a no-treatment control.
Evidence of efficacy
The evidence was inconclusive for acute NP in the short
term. There were no trials with long-term outcomes in evidence
Five trials met the criteria for admissibility in the treatment
for chronic NP [39, 40, 76–79] (Table 14). Two trials [80, 81] were excluded from evidence (Table 11).
Bronfort et al.  (VS, 75) found that high-technology
rehabilitative exercise produced more long-term pain reduction
than SMT. Koes et al. [39, 40] (VS, 50) found SMT/
MOB superior to massage and to medical care for physical
functioning in the short term. Jordan et al.  (VS, 31)
found small, nonsignificant differences between spinal manipulation,
intensive exercise and physical therapy in the
short and long term. Sloop et al.  (VS, 31) showed a
nonsignificant advantage of SMT over placebo in the short
term for pain reduction and improvement. David et al. 
(VS, 31) reported nonsignificantly higher reduction in pain
for MOB than acupuncture in the short and long term; disability
Evidence of efficacy
There is moderate evidence for the following: that SMT/
MOB is superior to general practice medical care and physical
therapy in the short term for improving physical functioning;
that SMT is at most similar to high-technology
rehabilitative exercise in the short term and long term; that
SMT/MOB is similar in effect to detuned modalities in the
short term (Table 15).
Mix of acute and chronic neck pain
Five trials were included in evidence (Table 16) [58, 63, 82–84] Six trials were excluded (Table 11). [85–90]
Hoving  (VS, 69) found that patients receiving MOB
had faster improvement and less pain than patients receiving
physical therapy or general practice care in the short and
long term. Hurwitz et al.  (VS, 63) found essentially no
differences between the effect of SMT and MOB in terms
of pain and disability reduction in the short and long term.
Skargren et al.  (VS, 44) showed that physical therapy
resulted in greater pain reduction than SMT in the short and
long term. Brodin  (VS, 31) found greater short-term
pain reduction for a combination therapy including MOB
than for a combination therapy including massage or for
analgesics alone. Giles and Muller  (VS, 25) found SMT
produced nonsignificantly more pain and disability improvement
in the short term than acupuncture or analgesic
Evidence of efficacy
There is moderate evidence that MOB is superior to PT
for pain control in the short and long term and superior to
medical care in the short term. There is also moderate evidence
that SMT and MOB are similar in the short and long
term. There is limited evidence that SMT is inferior to PT
in the short and long term. There is also limited short-term
evidence that MOB is superior to some medical regimens (Table 17).
A sensitivity analysis was conducted to evaluate the effect
of changing the quality scores required for each level of
evidence in Table 1. We assessed the effect of 10 points in the 100–point quality scale. For LBP, lowering the required score would have added 4 studies with limited evidence of
efficacy for SMT. Raising the score from 50 to 60 would have
reduced the level of evidence from moderate to limited for
7 of 9 LBP studies. For NP, lowering the score would have
introduced limited evidence of efficacy of MOB for acute NP
and added to the moderate evidence of SMT efficacy for a
mix of acute/chronic NP. Raising the cutoff score would
have reduced moderate evidence for chronic NP to limited
evidence. Overall, sensitivity analysis showed that
changing the rules of evidence would have produced little
impact on the conclusions of our review.
Our review is an attempt to improve on the methodology
of existing systematic reviews, as suggested by Assendelft
et al.  We decided that studies with confounded
treatment effects could not support the efficacy of the target
therapies. Consequently, combination-therapy studies had to
isolate the unique contribution of SMT and/or MOB to the
overall treatment effect to be admitted into evidence. Patientoriented
outcomes, such as pain or disability, were required
for all studies. An effort was made to transform the relevant
outcomes to a common scale of percentage points, allowing
a standardized comparison across different studies.
We chose to evaluate the evidence of efficacy based on
the best evidence synthesis method [11, 12] rather than a
formal meta-analysis of all available RCTs. A number of
meta-analytical methods have been advocated for combining
clinical trials [91–94], but there is limited consensus regarding
decision rules for statistical pooling of study results [95, 96]. It is recognized by several authors that one of the
most important limitations of published meta-analyses is
inadequate control for clinical heterogeneity (important
differences in treatments, outcome measures and clinical
characteristics of patients) of included studies. [14, 95–97]
Because clinical heterogeneity was found to be a major
issue in the RCTs that formed the basis for our efficacy
determination, we decided not to perform a statistical pooling
of trial results. However, if current efforts (eg, by the Cochrane
Collaboration ) are successful in further developing
the methodology, statistical pooling of clinically heterogeneous
studies may be feasible in the future.
Systematic reviews on effectiveness of SMT/MOB
There are now more randomized controlled clinical trials
on spinal manipulation for the management of LBP than for
any other treatment method. Several systematic reviews of
studies evaluating spinal manipulation for back pain have
been published since 1985. Most of the reviews have assessed
and factored in the methodological quality or validity
of the RCTs. However, weighting the credibility of trial
results using these quality scores remains controversial, and
no single approach for incorporating quality scores in the
determination of the evidence has been accepted (eg,
methods suggested by Detsky et al. ). There is some
evidence suggesting that nonrandomized, unblinded trials,
cases series and trials with historical controls tend to overestimate
the magnitude of a difference or an effect. [100, 101] Yet, there is little evidence that quality scores assigned to RCTs are good predictors of the magnitude and direction of
outcomes of therapy.  Most research methodologists
are in agreement that quality is important  but are
unclear as to how much quality really matters.
The first attempt at statistical pooling of clinical trial
results was performed by Ottenbacher and Di Fabio , who
calculated effect sizes for pain and flexibility in 92 subcomparisons
within nine trials on SMT for LBP, 2 of which were
nonrandomized. He concluded that there was only limited
empirical support for the efficacy of SMT.
In 1991, Koes et al.  published a systematic review
of back and neck pain and concluded that, even though some
results were promising, the efficacy of spinal manipulation
had not been convincingly demonstrated. They chose not to
perform statistical pooling but to primarily look at trial results
as reported by authors, and relate the methodological
quality to negative and positive outcomes. They also concluded
that the quality of the 34 trials on LBP was
disappointingly low and much more attention needed to be
paid to methodology in future trials. An update in 1996 of
the Koes et al. review involving three additional trials did
not change their conclusions. 
Anderson et al.  performed effect size pooling for 23
LBP trials, 5 of which were nonrandomized, and concluded
that SMT was consistently more effective than a number of
comparison therapies. A sensitivity analysis including only
the studies with relatively high-quality scores yielded a
slightly lowered pooled estimate of effect size. Similarly, Di
Fabio  found that the published clinical trials did provide
evidence of efficacy of spinal manipulation for treatment of
In a more detailed and critical evaluation, Shekelle et al. 
concluded that spinal manipulation had been demonstrated
to be of short-term benefit in certain patients, particularly
those with uncomplicated acute LBP. They based this conclusion
on a meta-analysis (statistical pooling) of a subset
of seven clinical trials, which had data on recovery at 3
weeks. The overall pooled estimate showed a 17% higher
likelihood of recovery in favor of spinal manipulation. However,
a substantial number of trials were excluded from
the meta-analysis because most of the published RCTs at the
time used continuous outcomes that could not be collapsed
into dichotomous outcomes used in the meta-analysis (ie,
recovered/not recovered). The reviews by Andersen et al.  and Shekelle et al.  formed the major basis for the
conclusions regarding the efficacy of spinal manipulation in
the acute low back problems guidelines developed by the
Agency for Health Care Policy and Research in the United
Two reviews by Assendelft et al. [17, 105] (1992 and
1996) have focused entirely on trials addressing the efficacy
of SMT for patients with LBP in which the SMT was delivered
by chiropractors. The result of the second review, an
update of the first involving a total of eight RCTs, was that
no convincing evidence of efficacy of chiropractic SMT for
either chronic or acute LBP could be demonstrated. The
authors considered performing statistical pooling but
decided that it was not possible because of the heterogeneity
of the trials. 
The most comprehensive systematic review involving
an array of different treatments for LBP was reported by van
Tulder et al.  in 1997. They assessed the methodological
quality of the trials and used specific evidence-based rules to
determine the presence and strength of evidence of efficacy.
They concluded that for acute LBP, there was limited evidence
to suggest that spinal manipulation is better than placebo,
physical therapy, exercise and short-wave diathermy.
For chronic LBP, they found strong evidence that spinal
manipulation was better than placebo and moderate evidence
that it was better than the treatment offered by a general
practitioner, massage, bed rest and analgesics.
Also in 1997, Bronfort [106, 107] published a systematic
review of the efficacy of spinal manipulation emphasizing
the magnitude of treatment effects compared with other treatments
in determining the strength of evidence. He elected
to ignore the conclusions by the authors of the individual
RCTs and to focus on the data only. He reached a conclusion
similar to that of Van Tulder et al. , finding evidence
of short-term efficacy for spinal manipulation in patients
with both acute and chronic LBP. Currently, a Cochrane
review by Assendelft and Shekelle  is in process that
addresses the efficacy of spinal manipulation for both acute
and chronic LBP.
The methodological differences among systematic reviews
have the potential to generate varying conclusions
regarding the efficacy of spinal manipulation. Surprisingly,
the conclusions regarding SMT for acute LBP have been
relatively consistent, with one exception. The majority of
the reviews indicated some evidence supporting the shortterm
efficacy of SMT for acute LBP, whereas Koes et al.  found the evidence inconclusive. For chronic LBP, the
results of the systematic reviews have been more mixed, with
the earlier reviews finding inconclusive evidence and later
reviews finding moderate to strong evidence in support of
SMT. Table 18 summarizes the systematic reviews that have
addressed SMT for LBP.
Four systematic reviews have assessed the efficacy of
SMT and MOB in NP conditions. [3, 16, 109, 110] Koes et
al.  found no convincing evidence of efficacy of SMT
in NP patients based on the review of five trials. Di Fabio  also found no evidence of efficacy. Hurwitz et al. 
reviewed three RCTs on acute NP [71, 73, 74] and concluded
that there was a short-term benefit of cervical MOB. In
contrast, we excluded two of the studies [73, 74] contributing
to this conclusion because the unique treatment effects of
MOB could not be isolated. Furthermore, Hurwitz et al.  performed a meta-analysis of three subacute/chronic
NP trials. [40, 72, 77] They concluded that SMT and/or MOB
showed a clinically important short-term advantage over
muscle relaxants and usual medical care. We decided to
refrain from statistical pooling of the trials on the grounds
of clinical heterogeneity. Despite the methodological differences,
the findings of Hurwitz et al. are consistent with
our results. Finally, Aker et al.  concluded that conservative
treatment of SMT and MOB in combination with
other therapies is efficacious for NP. In their discussion, they
state that their analysis did not allow for the isolation of the
unique effect of the target therapies.
In a review of reviews on treatment for NP, Hoving et
al.  showed that there was poor concordance among
reviews including effectiveness of SMT and MOB. Many
of the reviews displayed major methodological flaws. The
authors concluded that there is a paucity of evidence from
primary studies on NP, and hence, more research is needed to
allow systematic reviews to formulate stronger conclusions.
Clinical practice guidelines
Since 1990, national health-care agencies, advisory
groups or family medicine groups in North America, Europe,
Israel, New Zealand and Australia have developed official
national LBP guidelines (see Table 19). The number of RCTs
has increased during this time, and different criteria have been
used for prioritizing and incorporating scientific evidence
in the development of these documents. It is therefore not
surprising that the recommendations vary substantially. The
New Zealand  and original British guidelines 
relied primarily on the conclusions of the US guidelines. The
Dutch  guidelines are based on a mixture of evidence and
opinion, the Australian guidelines  on a nonsystematic
review of the literature, and the Israeli guidelines  on
the results of the systematic review by Koes et al. published
in 1996. [16, 117] The US , the updated British 
and the newly published Norwegian guidelines  followed
explicit rules for determining and weighting the scientific
evidence. None of these last three mentioned guidelines
have assessed the efficacy for chronic LBP, but all conclude
that there is efficacy for and recommend the use of spinal
manipulation in the treatment of acute LBP.Of the guidelines
that have addressed the treatment of both acute and chronic
LBP, the Finnish , Swiss  and German  advocate
the use of SMT only in the acute phase. The Danish
MTV report published in 1999  recommends SMT as
a treatment option for both acute and chronic LBP. The
Swedish guidelines published in 2000  also concluded
that there is scientific evidence to support the use of SMT
for short-term relief of both acute and chronic LBP. Currently,
the European countries are working together to coordinate
and produce updated European evidence-based
guidelines for both acute and chronic LBP. As of mid-2002,
the recommendations for acute LBP are in the process of
Conclusions about the strength of evidence from systematic
reviews and clinical guidelines are largely dependent
on the evidence-classification system used by the authors.
Because of the lack of consensus in this area , efforts
are being made primarily by a rapidly growing international
organization, the Cochrane Collaboration , to standardize
methods guiding the conduct of systematic reviews. This
organization is dedicated to the conduct of the highest quality
systematic reviews of the effects of health care. As these
standards evolve and get implemented, the validity of many
of the systematic reviews and clinical guidelines in existence
will likely be questioned and either abandoned or updated
appropriately. Clinicians using guidelines are advised to
become familiar with critical appraisal tools to help them
in evidence-based clinical decision making. [126, 127]
Clinicians should exercise caution in interpreting the results
of individual RCTs on SMT and/or MOB. In spite of
urgent calls for improved methodological quality of RCTs
on spinal manipulation [105, 128], it appears that even the
most recently published RCTs have been of discouragingly
low quality. Fifty-two (75%) of the 69 RCTs in this review
exhibited relatively low quality (validity scores less than
50). Of the 43 trials accepted into evidence, 29 (67%) also
had relatively low validity scores (6 to 44). Additionally,
clinicians should be careful about generalizing the findings of
systematic reviews to practice. Disparate patient populations
are likely to be included in the reviews, and potentially
important distinguishing characteristics, such as condition
severity, are not always carefully defined. In addition, providers
with different backgrounds and training apply diverse
SMT/MOB therapeutic approaches.
Optimally, reviews should include all trials regardless of
language.  Because of the languages spoken by the authors,
this review was restricted to English, Scandinavian
and Dutch languages. Although an attempt was made to identify
trials in other languages, this approach was not fully
systematic and may have overlooked some relevant trials.
However, none of the over 50 reviews previously reviewed
by Assendelft et al.  included RCTs that were published in
languages other than those addressed in this review.
Another possible limitation of the current review is publication
bias.  No exhaustive effort was made to identify
unpublished research, which is more likely to have negative
outcomes. [130–132] This phenomenon is likely to be partly
the result of lack of submission for and acceptance of negative
trials for publication.  It is recognized that attempts
to retrieve unpublished data from trials are also
likely to be biased.  The best solution to this problem
is to insist that journal editors make a policy of deciding on
publication based on scientific quality and not on the outcome
of the study. Also, to help prevent publication bias,
prospective registration of all RCTs should be undertaken. [130, 132]
Specific conclusions regarding the strength of evidence
from systematic reviews and practice guidelines vary substantially.
This is not surprising given the differences in
literature evaluation protocols regarding study inclusion criteria,
subclassification of back and NP by duration of complaint
and recurrence, methodological quality determination,
rules for weighting evidence and statistical analysis. The
validity scores of this review generally demonstrated modest
correlation with the methodological scores of other systematic
reviews on the topic (r = 0.41 to 0.74). [7, 16, 110] However,
the five-point validity scale used in one review 
was negatively correlated with our scores (r = –0.26).
This means that substantial inconsistencies between quality
scoring systems exist. In some cases, trials assigned lowquality
scores in this review were assigned high scores in
previous reviews. This disparity in review results is consistent
with findings of other investigators in different clinical
topic areas.  Until standardized methods to conduct
systematic reviews are fully implemented (such as those
being developed by the Cochrane Collaboration), there will
continue to be disparity between even the highest-quality
Trial results and treatment of individual patients
Interpretation of the results of RCTs has traditionally
focused on the statistical significance, whereas the clinical
importance of differences between treatments or control has
frequently been ignored. Very little is known about what
is considered by patients to be a minimal clinically important
change in outcome measures, such as pain and disability.
However, a key question needed to interpret the
results of clinical trials is whether the measured standardized
group difference in outcomes (effect size) is clinically important.
Sometimes, the investigators arbitrarily stipulate the
minimal clinically important difference. Usually, authors
assume that if the mean difference between a treatment and
control is appreciably less than the smallest predetermined
important change, then the treatment had little or no effect.
Conversely, it is also assumed that if the observed mean
difference between treatments is substantially larger than the
smallest important change, most or all patients benefited
from the treatment. This is not necessarily true.
Benefit depends not only on differences between group
means, but also on the distribution of outcomes among patients
within each treatment group. Members of an international
clinical significance consensus group recently
addressed this topic in a series of publications. [133–135]
They concluded that no single approach to interpreting findings
from RCTs and systematic reviews is perfect. Authors
too often draw inappropriate conclusions when they declare
treatment ineffectiveness based solely on presence or absence
of statistical differences between a test treatment and
a control. To inform decisions about management of the
individual patients, it may be much more appropriate to
think in terms of available treatment options that have shown
a meaningful clinical effect rather than choosing or discarding
specific therapies based on mean group differences of
undefined clinical importance.
Side-effects and complications
In evaluating any therapy, weighing the potential risks
against the potential benefits is a crucial issue. The adverse
reactions associated with spinal manipulation can be divided
into three categories. The first category consists of relatively
common benign transient side effects, such as local muscle
and joint soreness, which rarely lead to even short-term
impairment in functional status.  The best source of
information on these common side effects comes from several
Scandinavian prospective studies , which show
that the mild short-lasting muscle soreness occurs in up to
half of patients treated. The second category consists of
reversible serious complications, which are relatively uncommon,
such as progression of neurological deficits resulting
from lumbar disc herniation.  The third category
consists of irreversible complications, which appear to be
extremely rare. The risk of irreversible cauda equina syndrome
is estimated to be as low as 1 in 100 million lumbar
spine manipulations. [5, 138] Additionally, misdiagnosis
leading to delay in optimal treatment (eg, cancer presenting
as a spinal pain syndrome) falls into this category. There are
currently 46 RCTs published on spinal manipulation for LBP
involving over 5,000 patients. No serious adverse events
have been reported in these trials.  A systematic review
of the literature to date on the second and third categories of
complications consists mainly of single cases or a series
of case reports totaling approximately 300 cases, of which
the vast majority are related to manipulation of the cervical
spine.  Individual estimates and the results of the
retrospective surveys consistently suggest a risk of serious
cerebrovascular complication of approximately 1 per 1 million
cervical manipulations.  Overall, serious or severe
complications from spinal manipulation seem to be very
rare. Although underreporting in the literature is a likely
phenomenon, some reports may have wrongly attributed
side effects to spinal manipulation.  Thus, the existing
estimates are associated with substantial uncertainty and
will only improve when more data become available from
well-designed prospective studies. 
Cost-effectiveness is defined as the cost associated with a
specified clinical intervention per unit of a selected health
outcome, such as pain reduction or improvement in disability
and functional status.  One Canadian health economist
considers the available evidence of cost-effectiveness of chiropractic
SMT overwhelming compared with medical and
other forms of therapy  and made recommendations to
health policy makers that chiropractic inclusion in public
health-care plans would result in substantial health-care
cost savings in the area of LBP. This conclusion is almost
exclusively based on analysis of retrospective and nonrandomized
studies, which do not allow conclusions about clinical
effectiveness. Cost comparisons have been performed
alongside a few of the randomized studies. Based on retrospective
cost estimations in the British Meade trial , the
authors argued that the potential cost savings over a 3–
year period were higher for patients with LBP managed by
chiropractors than for patients managed by hospital outpatient
departments. [56, 57] In the trial by Cherkin et al. , the
mean costs of care over a 2–year period were very similar
for the physical therapy and chiropractic groups but about
three times higher than for the booklet group. Skargren et al.  found no difference in the cost-effectiveness ratio between
chiropractic and physical therapy in the management
of neck and back pain in Sweden.
The most comprehensive cost-effectiveness analysis to
date was performed by Hoving et al.  The trial compared
MOB, physical therapy and general practitioner care
for a case mix of acute and chronic NP. MOB was more costeffective
than the other two interventions both in the short and
long term. However, if the limitations of the existing studies
addressing cost-effectiveness are carefully considered, and
the premise that clinical efficacy and its relationship to cost
is best addressed in prospective randomized studies, then,
at present, the weight of evidence is still insufficient to
make any clear conclusions regarding the relative costeffectiveness
of SMT in comparison with other health-care
choices for LBP.
For acute LBP, there is moderate evidence that SMT
provides more short-term pain relief than mobilization and
detuned diathermy, and limited evidence of faster recovery
than a commonly used physical therapy treatment strategy.
For chronic LBP, there is moderate evidence that SMT
has an effect similar to an efficacious prescription NSAID,
SMT/MOB is effective in the short term when compared
with placebo and general practitioner care, and SMT/MOB
is effective in the long term compared to physical therapy.
There is limited to moderate evidence that SMT is better
than physical therapy and home back exercise in both the
short and long term. There is limited evidence that SMT
is superior to sham SMT in the short term and superior to
chemonucleolysis for disk herniation in the short term. There
is limited evidence thatMOBis inferior to back exercise after
disc herniation surgery.
For a mix of acute and chronic LBP, SMT/MOB provides
either similar or better pain outcomes in the short and long
term when compared with placebo and with other treatments,
such as McKenzie therapy, medical care, management by
physical therapists, soft tissue treatment and back school.
For acute NP, there are few studies and the evidence is
For chronic NP, there is moderate evidence that SMT/
MOB is superior to general practitioner management for
short-term pain reduction but that SMT offers at most
similar pain relief to high-technology rehabilitative exercise
in the short and long term.
For a mix of acute and chronic NP, the overall evidence
is not clear. There is moderate evidence thatMOB is superior
to physical therapy and family physician care, and similar to
SMT in both the short and long term. There is limited evidence
that SMT, in both the short and long term, is inferior
to physical therapy.
Our data synthesis suggests that recommendations can
be made with some confidence regarding the use of SMT
and/or MOB as a viable option for the treatment of both
LBP and NP. There have been few high-quality trials distinguishing
between acute and chronic patients, and most are
limited to shorter-term follow-up. Future trials should examine
well-defined subgroups of patients, further address the
value of SMT and MOB for acute patients, establish optimal
number of treatment visits and consider the cost-effectiveness
Operational definitions of items included in the Critical Evaluation List for Randomized Clinical Trials
The critical evaluation list contains eight items
with three choices: yes (+), partial (P) and no (–). One
point is awarded for a yes rating, a half point is assigned
for a partial rating, and 0 points is given for a no rating.
The quality score is determined by dividing the point total
by 8 and multiplying the result by 100 to create a 100–point scale.
Similarity of baseline characteristics or adjusted effects
Comparability established by tabulating important
predictor variables, including baseline value
of outcome variables. If not comparable, adjusted
between-groups effects computed (eg, analysis of covariance).
P: Baseline comparability established for
some but not all of the important predictor variables.
Baseline comparability not established, and appropriate
statistical adjustments not made or not
Concealment of treatment allocation
The randomization process and allocation concealment
established explicitly and appropriate. P:
Incomplete description of randomization/concealment.
Only randomization established.
Blinding of patients
Patient blinded to treatment. P: Patient partially
blinded or blinding not clearly documented.
blinding not established.
Blinding of provider/attention bias
Provider blinded to treatment. P: Partial blinding
achieved or documentation that provider enthusiasm/
attention equivalent among groups. For example, two
providers used such that a blinded provider interacts
with the patient and an unblinded provider renders
Provider not blinded and provider enthusiasm/
attention not controlled.
Blinding of assessor/unbiased outcome assessment
Outcomes assessor blinded to treatment. For selfadministered
outcomes, patients not influenced by
study personnel (eg, mailed questionnaire). P: Partial
blinding or influence unclear.
blinded. For self-administered outcomes, patients
likely influenced by providers or investigators during
Dropouts reported and accounted for in the analysis
Described for each group separately and impact
on outcomes analyzed, or dropout rate less than 5%.
P: Incomplete description/analysis.
or omission not justified.
Missing data reported and accounted for in the analysis
Described for each group separately and impact
on outcomes analyzed, or missing data rate less than
5%. P: Incomplete description/analysis.
or omission not justified.
Intension-to-treat analysis/balanced cointervention
All patient data analyzed according to group of
initial random allocation. In studies with documented
full compliance with allocated treatments, no differential
co-intervention between groups. P: Unclear from
article whether intention-to-treat analysis was used
No intention-to-treat analysis used
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