Osteopathic Manipulative Treatment for
Chronic Low Back Pain
A Randomized Controlled Trial
from Spine
Posted
John C. Licciardone, DO,
Scott T. Stoll, DO, Kimberly G. Fulda,
Abstract and Introduction
Abstract
Study Design: A randomized controlled trial was conducted.
Objective: To determine the efficacy of osteopathic manipulative treatment as a
complementary treatment for chronic nonspecific low back pain.
Summary of Background Data: Osteopathic manipulative treatment may be useful for
acute or subacute low back pain. However, its role in
chronic low back pain is unclear.
Methods: This
trial was conducted in a university-based clinic from 2000 through 2001. Of the
199 subjects who responded to recruitment procedures, 91 met the eligibility
criteria. They were randomized, with 82 patients completing the 1-month
follow-up evaluation, 71 completing the 3-month evaluation, and 66 completing
the 6-month evaluation. The subjects were randomized to osteopathic
manipulative treatment, sham manipulation, or a no-intervention control group,
and they were allowed to continue their usual care for low back pain. The main outcomes
included the SF-36 Health Survey, a 10-cm visual analog scale for overall back
pain, the Roland-Morris Disability Questionnaire, lost work or school days
because of back pain, and satisfaction with back care.
Results: As
compared with the no-intervention control subjects, the patients who received
osteopathic manipulative treatment reported greater improvements in back pain,
greater satisfaction with back care throughout the trial, better physical
functioning and mental health at 1 month, and fewer cotreatments
at 6 months. The subjects who received sham manipulation also reported greater
improvements in back pain and physical functioning and greater satisfaction
than the no-intervention control subjects. There were no significant benefits
with osteopathic manipulative treatment, as compared with sham manipulation.
Conclusions: Osteopathic manipulative treatment and sham manipulation both appear to
provide some benefits when used in addition to usual care for the treatment of
chronic nonspecific low back pain. It remains unclear whether the benefits of
osteopathic manipulative treatment can be attributed to the manipulative
techniques themselves or whether they are related to other aspects of
osteopathic manipulative treatment, such as range of motion activities or time
spent interacting with patients, which may represent placebo effects.
Introduction
It is estimated that 15% to 20% of the U.S. population
experiences low back pain annually, and that at any given time, 2% of the
population is disabled because of back problems.[1] Historically, low back symptoms
have been the second leading cause of office visits to primary care physicians
and the most common reason for visits to osteopathic physicians.[2] The
total annual costs of back pain in the United States have been estimated at $20
to $50 billion,[3] despite efforts by managed care organizations to control access to
health care and to contain costs.[4]
A comprehensive evaluation of spinal manipulation for
low back pain was undertaken by the Agency for Healthcare Research and Quality.[5] This
organization recommended that spinal manipulation can be helpful for patients
with acute low back problems without radiculopathy
when used within the first month of symptoms.[5] A recent review of this clinical practice
guideline found that only minor updating is needed, involving primarily
recommendations for back schools, lumbar corsets, and epidural steroid
injections.[6]
Two major studies have investigated osteopathic
manipulative treatment (OMT) for low back pain in the United States
administered by osteopathic physicians who are fully qualified medical
practitioners. The first study, a randomized controlled trial involving
patients referred to a university-based back clinic in California from 1973 to
1979, found significant benefits with the first manipulative treatment, as
compared with a combined treatment involving soft tissue massage and a sham
manipulation technique.[7] However, no
significant benefits were attributed to manipulation at discharge, which occurred
an average of 30 days after the initial treatment.
Another randomized controlled trial, performed at two
medical offices of an Illinois-based health maintenance organization from 1992
to 1994, involved patients with "subacute"
low back pain lasting at least 3 weeks but less than 6 months.[8] This trial compared OMT using a
variety of techniques, each at the discretion of the treating provider, with
usual care for low back pain. There were no significant differences in primary
clinical outcomes between the OMT group and the usual-care group at 12 weeks.
However, the OMT group used significantly less medication and physical therapy.
Studies of spinal manipulation for chronic low back
problems are inconclusive.[9] Furthermore, no studies specifically address the use
of OMT for chronic low back pain. The purpose of this trial was to study the
efficacy of OMT in ambulatory subjects with chronic nonspecific low back pain.
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John C. Licciardone,
DO*; Scott T. Stoll, DO†; Kimberly
G. Fulda, Departments of *Family Medicine
and †Osteopathic Manipulative Medicine, Texas College of Osteopathic
Medicine, University of North Texas Health Science Center, Fort Worth, the ‡John
Peter Smith Health Network, Fort Worth, Texas, the §College
of Education and Health Professions, University of Arkansas, Fayetteville,
Arkansas, and the ||Mayo Clinic, Rochester, Minnesota Spine
28(13):1355-1362, 2003. © 2003 Lippincott Williams
& Wilkins |
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Osteopathic Manipulative Treatment
for Chronic Low Back Pain
from Spine
Methods
A randomized controlled trial was conducted at the
University of North Texas Health Science Center at
A clinical research technician performed a brief
telephone screening of recruitment responders. Screened subjects were excluded
from participation if they were younger than 21 years or older than 69 years,
had any of six possible underlying causes of low back symptoms in their history
(spinal osteomyelitis, spinal fracture, herniated
disc, ankylosing spondylitis, cauda
equina syndrome, or cancer, excluding nonmalignant
skin cancer), had undergone surgery involving the low back within the preceding
3 months, had received workers' compensation benefits within the preceding 3
months or were potentially involved in litigation relating to back problems,
were pregnant, had ever been a patient at the trial clinic site, were an
employee of the trial clinic site, or had received spinal manipulation for back
pain within the preceding 3 months or on more than three occasions during the
preceding year.
Eligible screened subjects were subsequently
interviewed by the clinical research technician, who explained the research
protocol and obtained verbal and written informed consent. These participating
subjects then underwent a more thorough clinical assessment adapted from the
Clinical Practice Guideline on Acute Low Back Problems in Adults.[5] This
baseline assessment included a focused medical history and physical
examination, including neurologic evaluation,
performed by a predoctoral osteopathic manipulative
medicine fellow. Subjects with "red flags" for any of the six
aforementioned underlying causes of low back symptoms were identified, given
appropriate recommendations for follow-up evaluation, and excluded from further
participation. The red flags for each of the six conditions were as follows[5]:
1.
spinal osteomyelitis: intravenous drug use, urinary tract
infection, or skin infection within the preceding year, or corticosteroid use
of more than 3 months duration within the preceding year
2.
spinal
fracture: spinal trauma within the preceding year or corticosteroid use
exceeding 3 months duration within the preceding year
3.
herniated disc:
history of leg pain radiating below the knee, history of persistent numbness or
weakness in the leg or legs, or history of claudication
4.
ankylosing spondylitis: morning back stiffness in persons younger than
40 years
5.
cauda equina
syndrome: history of bladder dysfunction, saddle anesthesia, or fecal
incontinence
6.
cancer: history
of previous cancer, excluding nonmalignant skin cancer, unexplained weight loss
of at least 10 pounds or 5% of body weight within the preceding year, or no
relief of low back symptoms with bed rest for persons older than 50 years.
Because approximately 12% of ambulatory patients with
back pain have symptoms of sciatica or leg pain without neurologic
compromise related to lumbar disc herniation,[5] the
authors sought to include such subjects in the trial. However, to minimize the
likelihood of including subjects with a lumbar disc herniation,
subjects with sciatica were included only if they tested negative for all of
the following: 1) ankle dorsiflexion weakness; 2)
great toe extensor weakness; 3) impaired ankle reflexes; 4) loss of light touch
sensation in the medial, dorsal, and lateral aspects of the foot; 5) ipsilateral straight-leg-raising test (positive result: leg
pain at <60°); 6) crossed straight-leg-raising test (positive result:
reproduction of contralateral pain).
These six neurologic tests
allow detection of most clinically significant nerve root compromises resulting
from L4-L5 or L5-S1 disc herniations, which together
make up more than 90% of all clinically significant radiculopathies
attributable to lumbar disc herniations.[5] All
eligible subjects then received an osteopathic structural evaluation performed
by a predoctoral osteopathic manipulative medicine
fellow to identify areas of somatic dysfunction that might potentially be
associated with low back pain, and to develop an initial treatment plan for
these areas.[10]
At the baseline assessment, data were collected on
each subject's age, gender, race and ethnicity, marital status, education,
occupation, type of insurance coverage, and comorbid
medical conditions within the preceding 3 months. The Medical Outcomes Study
Short Form-36 Health Survey (SF-36) was used to measure the self-reported
health status of the subjects. The SF-36 is a valid and reliable instrument widely
used to measure generic health status, particularly for monitoring clinical
outcomes after medical interventions.[11, 12] The SF-36 provides data on health
concepts using the following scales[11]: physical functioning, role
limitations because of physical problems, bodily pain, general health,
vitality, social functioning, role limitations because of emotional problems,
and mental health.
Each subject's overall perception of back pain was
assessed using a 10-cm horizontal visual analog scale. Findings have shown that
the data derived from such written scales among patients with chronic low back
pain are normally distributed, even when the scales are used without verbal
instructions.[13] Pain at the two extremes of this scale was labeled as "not noticeable
at all" and "worst pain possible." During clinic visits, OMT and
sham manipulation subject responses to this scale were collected before
treatment was received. The scale was scored by a blinded clinical research
technician using a standard ruler.
Functional status and disability resulting from back
pain were measured with the Roland-Morris Disability Questionnaire.[14] This
questionnaire is short and simple to complete, and appears to be well suited
for studies involving patients with mild to moderate disability.[15]
Empirical research suggests that the Roland-Morris Disability Questionnaire
poses fewer problems involving blank or multiple responses than either the Oswestry Disability Index or the Jan van Breemen Institute pain and functional capacity
questionnaire, and therefore may be the preferred instrument for assessing
change over time in patients with low back pain.[16] Additional data specific to back
pain also were collected on the number of current cotreatments
using a checklist of 12 possible treatments, current medication use, the number
of lost work or school days within the preceding 4 weeks, and global
satisfaction with back care as measured by Likert
scale responses. Together, the trial data include the five domains of
patient-based outcomes recommended for evaluating the treatment of spinal
disorders[17]: 1) generic health status, 2) pain, 3) back-specific function, 4) work
disability, 5) back-specific patient satisfaction.
After baseline assessment and data collection, the
subjects were assigned randomly to one of three treatment groups in an
approximate 2:1:1 ratio: OMT, sham manipulation, or no intervention as a
control condition. The intent of this allocation strategy was to enroll
comparable numbers of subjects receiving OMT and not receiving OMT, and
subsequently to combine the sham manipulation and no-intervention control
groups should no statistically significant differences be observed between the
latter groups.
Randomization was performed using sequential sealed
envelopes prepared by the clinical research technician before enrollment of the
subjects. The treating predoctoral osteopathic
manipulative medicine fellows subsequently opened the sealed envelopes and
recorded the allocation of subjects as they entered the trial. The osteopathic
manipulative medicine fellows responsible for the baseline assessments,
structural evaluations, initial treatment plans, randomization, and OMT and
sham manipulation interventions all were third- or fourth-year medical students
in the process of completing an additional year of medical training devoted
entirely to osteopathic theory and practice. All the trial personnel, with the
exception of these fellows, were blinded to treatment group assignments
throughout the trial.
Osteopathic and sham manipulation subjects were
treated for a total of seven visits over 5 months, including visits 1 week, 2
weeks, and 1 month after baseline assessment, and then monthly thereafter. Each
subject in these two groups was to receive his or her assigned treatment at all
seven visits regardless of previous treatment responses. The 6-month visit was
designed to collect exit data and did not include any treatment. Follow-up data
on the SF-36 scales, visual analog scale for back pain, Roland-Morris Disability
Questionnaire, and global satisfaction with back care were collected using each
at the 1-, 3-, and 6-month visits. Data on back-specific cotreatments,
current medication use, and lost work or school days were collected at the 1-
and 6-month visits. No-intervention control subjects provided these data on the
same timetable as the OMT and sham manipulation subjects, but did so through
postal questionnaires instead of during a clinic visit.
The following protocol was used for OMT treatments.
The OMT sessions lasted 15 to 30 minutes, and the OMT was performed by predoctoral osteopathic manipulative medicine fellows. The
techniques included one or a combination of the following: myofascial
release, strain-counterstrain, muscle energy, soft
tissue, high-velocity-low-amplitude thrusts, and cranial-sacral. The OMT was
aimed at somatic dysfunction in the low back or adjacent areas.
Because this trial was intended to assess the efficacy
of OMT as practiced in actual clinical encounters, the research protocol allowed
for discretion in OMT interventions and techniques across subjects and time.[10] Two
cohorts of predoctoral osteopathic manipulative
medicine fellows provided baseline structural evaluations and treatments for
3-month intervals on a rotating basis during the trial. A 1-hour trial-specific
training session for new and returning fellows was provided by an osteopathic
manipulative medicine specialist every 3 months to facilitate consistent
protocol implementation throughout the trial, including the provision of both
OMT and sham manipulation techniques.
Sham manipulation subjects received
"treatments" according to the same protocol guidelines and timetable
described previously for OMT subjects. These sham treatments included range of
motion activities, light touch, and simulated OMT techniques. The latter
consisted of manually applied forces of diminished magnitude aimed purposely to
avoid treatable areas of somatic dysfunction and to provide minimal likelihood
of therapeutic effect. The third group received no trial interventions. All the
subjects, regardless of group assignment, were allowed to receive usual or
other low back care to complement the trial interventions, with the exception
of other OMT or chiropractic manipulation. Data were collected on each
subject's use of cotreatments throughout the trial
including prescription and over-the-counter medications, physical therapy,
massage therapy, hydrotherapy, transcutaneous
electrical nerve stimulation, spinal and epidural injections, acupuncture,
herbal therapies, and meditation.
Baseline demographic and clinical characteristics were
summarized using descriptive statistics. Analysis of variance was used to test
for differences among the groups in continuous variables, and the 2 test was used for dichotomous or categorical
variables. Crude SF-36 data were transformed and standardized using recommended
procedures.[11] The Roland-Morris Disability Questionnaire was scored as the sum of
positive responses on each of its 24 items.[14] The Likert
scale responses for global satisfaction were transformed by assigning relative
weights to each of the possible response options. Repeated measures analysis of
variance[18] was used to identify significantly different changes over time among
the treatment groups in each of 14 primary outcomes: eight SF-36 health scale
scores, visual analog scale score for back pain, Roland-Morris Disability
score, number of cotreatments, current back
pain-specific medication use, lost work or school days related to back pain,
and global satisfaction with back care. Outcomes for which baseline data were
collected were tested for significance using the treatment group by time
interaction term. For a given outcome, such analysis compares the cumulative
experience of the treatment groups to the relevant point in time. The treatment
group main effects were used to test for significance related to global
satisfaction with back care because it was not possible to collect baseline
data for this variable. The 2 test was used to identify differences among the
treatment groups in the percentages of subjects currently using medication for
back pain.
The numbers of subjects receiving OMT and not
receiving OMT (the latter including the sham manipulation subjects and the
no-intervention control subjects combined) to be included in the trial to
achieve a power of approximately 80% in detecting moderate to large differences
between groups were determined using the SF-36 scales. The latter were used
because they comprised the majority of primary outcomes, and because extensive
data were available to estimate sample sizes for a repeated measures design.[11] All
hypotheses were tested at the 0.05 level of statistical significance. Data
management and analyses were performed using the SYSTAT software package (Systat Software,
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Spine 28(13):1355-1362, 2003. ©
2003 Lippincott Williams & Wilkins |
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Osteopathic Manipulative Treatment
for Chronic Low Back Pain
from Spine
Results
The flow of subjects through the trial is shown in
Figure 1. Altogether, 91 (46%) of the 199 persons who responded to recruitment
procedures were randomized. The three treatment groups were comparable with
regard to baseline characteristics (Table 1). At
trial entry, 46 (51%) subjects had experienced low back pain for more than 1
year, 22 (24%) were currently using multiple treatments for back pain, and 70
(77%) had used medication for back pain within the preceding 4 weeks. As
determined by mean SF-36 scale scores and available normative data,[11] the
subjects were comparable with the general U.S. population in terms of general
health (71 vs 72) and mental health (72 vs 75); had deficiencies involving role limitations
because of emotional problems (74 vs 81),
social functioning (73 vs 83), and vitality
(48 vs 61); and had substantial deficits
involving role limitations because of physical problems (36 vs
81), bodily pain (45 vs 75), and physical
functioning (62 vs 84). Nevertheless,
specifically with regard to low back pain, the mean Roland-Morris Disability score
of 7.5 ± 4.6 among the trial subjects suggests lower levels of functional
disability than reported by patients with nonspecific low back pain of more
than 6 weeks duration (normative mean, 12.1 ± 4.7).[15, 19]
|
Figure 1. (click image to zoom) Flow of subjects through the
clinical trial. |
Overall, 82 subjects (90%) completed the 1-month
follow-up assessment, 71 (78%) the 3-month assessment, and 66 (73%) the 6-month
assessment. There were no significant differences in attrition among the
treatment groups. Of the 25 patients who did not complete the study, two were
removed by trial personnel for medical reasons after randomization but before
receiving any treatment: one because of suspected spinal stenosis
and another because of broken ribs sustained during a fall.
As shown in Figure 2, there were significantly
different trends over time among the treatment groups on the SF-36 physical
functioning scale. At 1 month, the OMT subjects reported more improvement in
physical functioning than the no-intervention control subjects (P =
0.03). However, at 3 and 6 months, only sham manipulation subjects improved
more than the no-intervention controls subjects (P = 0.01 and P =
0.03, respectively). The only other significant findings with regard to the
SF-36 scales were that the OMT subjects reported greater mental health
improvement than no-intervention control subjects at 1 month (P = 0.04),
and that the sham manipulation subjects reported fewer role limitations because
of physical problems than the no-intervention control subjects at 6 months (P
= 0.04).
|
Figure 2. (click image to zoom) SF-36 physical functioning
scale scores over time (mean ± SE). The table entries represent P
values for the cumulative experience from baseline to the applicable point in
time. Higher scores represent better physical functioning. |
Figure 3 also demonstrates significantly different
trends over time among the treatment groups with regard to visual analog scale
scores for back pain. Both the OMT and sham manipulation subjects reported greater
improvements in back pain than the no-intervention control subjects at 1 (P
= 0.01 and P = 0.003, respectively), 3 (P = 0.001 and P =
0.01, respectively), and 6 (P = 0.02 and P = 0.02, respectively)
months. Despite these findings, there were no significant differences over time
among the treatment groups in the Roland-Morris Disability scores.
|
Figure 3. (click image to zoom) Visual analogue scale scores
for back pain over time (mean ± SE). The table entries represent P
values for the cumulative experience from baseline to the applicable point in
time. Higher scores represent greater pain. |
As shown in Figure 4, the OMT subjects used fewer cotreatments than the no-intervention control subjects at 6
months (P = 0.03). However, there were no significant differences among
the treatment groups in back pain-specific medication use or lost work or
school days over time. Figure 5 demonstrates that both OMT (P = 0.001)
and sham manipulation (P = 0.02) subjects reported significantly greater
satisfaction with their back care than the no-intervention control subjects.
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Figure 4. (click image to zoom) Number of cotreatments
for back pain over time (mean ± SE). The table entries represent P
values for the cumulative experience from baseline to the applicable point in
time. |
|
Figure 5. (click image to zoom) Global satisfaction with back
care over time (mean ± SE). Higher scores represent less satisfaction with
back care. Significant differences in main effects were observed between OMT
subjects and no intervention controls (P = 0.001) and between sham
manipulation subjects and no intervention controls (P = 0.02). |
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Spine 28(13):1355-1362, 2003. ©
2003 Lippincott Williams & Wilkins |
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Osteopathic Manipulative Treatment
for Chronic Low Back Pain
from Spine
Discussion
This trial is unique in being the first to address the
efficacy of OMT for chronic nonspecific low back pain. Despite several
favorable findings among comparisons of OMT subjects and no-intervention
controls subjects, the observation of similar favorable findings among
comparisons of sham manipulation subjects and no-intervention control subjects
and the lack of any significant differences in outcomes between the OMT and
sham manipulation subjects raise questions about the inherent effects of the
OMT techniques. In addition to the possibility of placebo effects, there are several
important methodologic considerations that may help
explain the findings of this trial.
The issue of appropriate control treatments in OMT
research is controversial. Clinical trials that include only a no-intervention
control condition are likely to bias their results in favor of OMT for at least
three reasons: 1) the "laying on of hands," 2) greater attention from
and interaction with the treating provider, and 3) expectation of a therapeutic
effect. Indeed, a recent systematic review found evidence that placebos had a
significant beneficial effect, as compared with no treatment, in trials that
used self-reported continuous outcomes,[20] such as those commonly used in this
trial.
This review further found that the significant
benefits of placebo were evident in studies that investigated pain as an
outcome, and estimated the placebo effect to be 0.65 cm on a 10-cm visual
analogue scale such as that used in this trial or one third the effect of nonsteroidal antiinflammatory
drugs.[20, 21]
Several factors may have attenuated the potential
benefits of OMT in this trial. First, the fellows used to provide OMT and sham
manipulation in this trial were third- and fourth-year medical students in the
process of completing an additional year of training devoted to osteopathic
theory and practice. It is possible that such predoctoral
fellows may not have had sufficient practical experience to provide OMT with
the same efficacy as more seasoned practitioners or to provide nontherapeutic sham manipulation. With regard to knee or
hip osteoarthritis, a randomized controlled trial using predoctoral
fellows to provide treatment failed to demonstrate any clinical benefits
attributable to OMT,[22] although previous studies using osteopathic residents
found such benefits.[23, 24]
Second, although the three treatment groups were
comparable with regard to back pain-specific cotreatments
and medication use at baseline, the no-intervention control group showed more
use of cotreatments than the OMT group at 6 months.
The use of more cotreatments may have improved the
outcomes of the no-intervention controls, thereby attenuating differences in
clinical outcomes in comparisons with the OMT subjects.
Third, to make the current findings more generalizable, the authors sought to include as many
subjects with chronic nonspecific low back pain as possible. Thus, 46% of the
recruits met eligibility criteria and were randomized to the trial, as compared
with 5%[7] and 15%[8] who met eligibility criteria in previous trials of OMT. The relatively
low baseline Roland-Morris Disability scores likely were manifestations of the
more inclusive criteria used in the current trial and suggest that the subjects
were not highly selected to demonstrate large clinical improvements in response
to treatment. When studies operate at the low (healthy) end of the
Roland-Morris Disability scale, smaller thresholds exist for determining
clinically important improvements over baseline scores.[25]
Consequently, larger sample sizes are needed to power a trial adequately for
such end points. The relatively small sample sizes in this clinical trial
impeded its ability to detect small to moderate treatment effects. It is
possible that such OMT benefits may exist and that they are clinically
relevant, but that larger trials will be needed to demonstrate them.
Fourth, 10% of the subjects were lost to follow-up
evaluation at 1 month, 22% at 3 months, and 27% at 6 months. This slightly
exceeds the criterion of 10% to 20% loss to follow-up evaluation used to assess
randomized controlled trials of manipulation for back and neck pain,[26, 27] although this criterion is somewhat arbitrary and does not allow for
greater losses to follow-up evaluation in lengthier trials such as this one. By
comparison, in the two OMT trials cited earlier, attrition was 27% at discharge
(mean of 30 and 20 days after baseline for OMT and control groups,
respectively), 39% at trial completion (mean of 51 and 41 days after baseline
for OMT and control groups, respectively),[7] and 13% at trial completion (mean
of 12 weeks after baseline).[8]
In summary, this clinical trial found that in
comparison with usual care alone, usual care and OMT provided better 1-month
outcomes in physical functioning, mental health, and back pain, but that only
the latter finding persisted over 6 months. Osteopathic manipulative treatment
also resulted in the use of fewer cotreatments at 6
months and provided greater satisfaction throughout the trial. Nevertheless,
usual care and sham manipulation also provided better outcomes than usual care
alone in back pain, greater satisfaction throughout the trial, and better
physical functioning at 3 and 6 months. Methodologically, larger and more
powerful studies with more experienced OMT providers and better control of cotreatments are needed to determine whether OMT benefits
in chronic nonspecific low back pain are inherently attributable to the
manipulation techniques or whether they may be the result of placebo effects.
The submitted manuscript does not contain information
about medical devices or drugs. Institutional and professional organization
funds were received in support of this work. No benefits in any form have been
or will be received from a commercial party related directly or indirectly to
the subject of this article.
Acknowledgements
The authors express their gratitude to the other
faculty, predoctoral fellows, clinic personnel, and
employees who assisted in this project.
Funding Information
Partially supported by Grant 99-11-487 from the
American Osteopathic Association.
Reprint Address
Address correspondence to John C. Licciardone,
DO, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard,
Fort Worth, TX 76107; E-mail: jlicciar@hsc.unt.edu
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Section 4 of 4 |
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Spine 28(13):1355-1362, 2003. ©
2003 Lippincott Williams & Wilkins |
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