Osteopathic Manipulative Treatment for Chronic Low Back Pain

Spine 28(13):1355-1362, 2003. © 2003 Lippincott Williams & Wilkins

Methods
A randomized controlled trial was conducted at the University of North Texas Health Science Center at Fort Worth to study the efficacy of OMT for chronic nonspecific low back pain. Subjects were recruited from January 2000 through February 2001 using advertising in local newspapers and referrals from university-based clinics and other local physicians. Subjects with constant or intermittent, nonspecific low back pain for at least 3 months composed the target population. The research protocol was approved by the Institutional Review Board of the University of North Texas Health Science Center.

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]:

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

spinal fracture: spinal trauma within the preceding year or corticosteroid use exceeding 3 months duration within the preceding year

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

ankylosing spondylitis: morning back stiffness in persons younger than 40 years

cauda equina syndrome: history of bladder dysfunction, saddle anesthesia, or fecal incontinence

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, Richmond, CA).