Context

•Persons with acute or subacute neck pain often turn to chiropractors and other practitioners of spinal manipulation for pain relief.

Contribution

•This trial demonstrates that 12 weeks of spinal manipulation therapy (SMT) led to greater pain relief than medication up to 1 year after treatment. However, trial participants had as much pain relief with home exercise with advice (HEA) as with SMT over the same period.

Caution

•Participants were unblinded to interventions.

Implication

•For relief of acute or subacute neck pain, SMT and HEA seemed to be similarly effective and both were more effective than medication.—The EditorsNeck pain is a prevalent condition that nearly three quarters of persons experience at some point in their lives (1, 2). One of the most commonly reported symptoms in primary care settings (3, 4), neck pain results in millions of ambulatory health care visits each year and increasing health care costs (5–8). Although it is not life-threatening, neck pain can have a negative effect on productivity and overall quality of life (1, 9–11).Chiropractors, physical therapists, osteopaths, and other health care providers commonly apply spinal manipulation, a manual therapy, for neck pain conditions (12), and home exercise programs and medications are also widely used (13). Recent Cochrane reviews (13, 14) report insufficient evidence to assess the effectiveness of commonly used medications or home exercise programs for the treatment of acute neck pain. The evidence for spinal manipulation is similarly limited, with only low-quality evidence supporting its use for neck pain of short duration (15).Our goal was to test the hypothesis that spinal manipulation therapy (SMT) is more effective than medication or home exercise with advice (HEA) for acute and subacute neck pain.

Methods

Setting

The trial was conducted from 2001 to 2007 in Minneapolis, Minnesota. Eligibility screening, randomization, and short-term data collection occurred at a university-affiliated research center; long-term data collection took place by mail. A university-affiliated outpatient clinic provided SMT and instruction for home exercise. Medical treatment was provided at a pain management clinic. The institutional review boards of Northwestern Health Sciences University and Hennepin County Medical Center approved our study, and all participants gave written informed consent.

Participants

Participants were recruited by using mailings targeted to persons with neck pain who were registered with Blue Cross/Blue Shield Minnesota and through newspaper and radio advertisements. Interested persons were screened for eligibility at 2 baseline appointments by clinicians who were blinded to the randomization schedule. Inclusion criteria were age 18 to 65 years; primary symptom of mechanical, nonspecific neck pain equivalent to grades I or II according to the Bone and Joint Decade 2000–2010 Task Force on Neck Pain and Its Associated Disorders classification (16, 17); current neck pain of 2 to 12 weeks' duration; and a neck pain score of 3 or greater on a scale of 0 to 10. Participants were asked to refrain from seeking additional treatment for neck pain from nonstudy health care providers during the 12-week intervention.Exclusion criteria were cervical spine instability, fracture, neck pain referred from peripheral joints or viscera, progressive neurologic deficits, existing cardiac disease requiring medical treatment, blood clotting disorders, diffuse idiopathic hyperostosis, inflammatory or destructive tissue changes of the cervical spine, infectious disease or other severe disabling health problems, substance abuse, pregnancy or breastfeeding, previous cervical spine surgery, and pending or current litigation. In addition, participants were excluded if they had received any of the study treatments in the past 3 months.

Randomization and Interventions

Participants were randomly assigned at the second baseline appointment by using permutated blocks of different sizes (18). The randomization schedule was prepared off-site by the study statistician before enrollment and was concealed from the investigators, treatment providers, and research staff by using consecutively numbered, sealed, opaque envelopes. As participants became eligible, envelopes were opened in consecutive order by a research staff member in the presence of the participant.The intervention protocol was tested in a pilot study by our research team (19). Maximum treatment duration was 12 weeks. Treatment providers were trained in the study intervention protocols and were required to document treatment activities in standardized clinical records, which were routinely monitored by research staff to ensure protocol adherence.

SMT Group

Six chiropractors with a minimum of 5 years' experience served as the primary providers of treatment. Visits lasted 15 to 20 minutes and included a brief history and examination of the cervical and thoracic spine. The primary focus of treatment was manipulation of areas of the spine with segmental hypomobility by using diversified techniques, including low-amplitude spinal adjustments (a high-velocity type of joint thrust manipulation) and mobilization (a low-velocity type of joint oscillation) (20). The specific spinal level to be treated and the number of treatment sessions over the 12 weeks was left to the discretion of the provider, based on manual palpation of the spine and associated musculature and the participant's response to treatment (21). Adjunct therapy common to clinical practice included limited light soft-tissue massage, assisted stretching, and hot and cold packs to facilitate the manipulation treatment. Advice to stay active or modify activity was recommended as needed.

Medication Group

A licensed medical physician provided care to participants, with the focus of treatment on prescription medication. Visits lasted 15 to 20 minutes and included a brief history and examination. The first line of therapy was nonsteroidal anti-inflammatory drugs, acetaminophen, or both (22, 23). Participants who did not respond to or could not tolerate first-line therapy received narcotic medications. Muscle relaxants were also used. Advice to stay active or modify activity was issued as needed. The choice of medications and number of visits was made by the physician on the basis of the participant's history and response to treatment.

HEA Group

Home exercise with advice was provided in two 1-hour sessions, 1 to 2 weeks apart, at the university-affiliated outpatient clinic. Six therapists provided instruction to participants. The primary focus was simple self-mobilization exercise (gentle controlled movement) of the neck and shoulder joints, including neck retraction, extension, flexion, rotation, lateral bending motions, and scapular retraction, with no resistance (Supplement). The delivery method was 1-on-1, and the program was individualized to each participant's abilities, tolerance, and activities of daily living. Participants were instructed to do 5 to 10 repetitions of each exercise up to 6 to 8 times per day. A booklet (24) and laminated cards of prescribed exercises were provided. Sessions were supplemented with information about the basic anatomy of the cervical spine and advice, including postural instructions and practical demonstrations of lifting, pushing, pulling, and other daily actions.

Outcomes and Measurements

We collected participant demographic and clinical characteristics at the initial baseline appointment by using self-report questionnaires, clinical history, and physical examinations. Self-reported outcomes (such as pain) were measured 6 times during the 12-week treatment period (at the 2 baseline appointments and 2, 4, 8, and 12 weeks after randomization). Outcomes were also collected twice during the posttreatment period (at weeks 26 and 52) by using a mailed questionnaire. All self-report questionnaires were completed by participants independent of influence from investigator, study staff, or treatment provider. Participants were asked in each questionnaire if anyone had attempted to influence their responses. Objective measures of cervical spine motion were measured at 4 and 12 weeks by 7 trained examiners who were masked to treatment assignment (25). Blinding was maintained by systematically instructing participants not to reveal treatment information and by ensuring that examiners had no exposure to activities in the outpatient clinics.We chose participant-rated pain as the primary outcome measure a priori and used an 11-box numerical rating scale (range, 0 [no symptoms] to 10 [highest severity of pain]) (26–29). Secondary outcomes included the Neck Disability Index (30), global improvement (31–33), medication use (34), satisfaction with care (25, 34), the Short Form-36 Health Survey (SF-36) (35), and cervical spine motion (measured with a CA 6000 Spine Motion Analyzer [Orthopedic Systems, Union City, California]) (36, 37).Before random assignment, participants were asked in the self-report questionnaire how they expected their neck pain to change in response to treatment, with choices of much better, better, no change, worse, and much worse. Participants were also asked to report additional health care use visits to nonstudy providers in the self-report questionnaires at all time points.Participants were asked standardized questions at each treatment visit to assess side effects since the last visit, and responses were documented in the clinical record.

Statistical Analysis

Our sample size calculation was based on an ability to detect a 0.8-point difference between the highest and lowest group means in participant-rated neck pain (the primary outcome) at the end of 12 weeks of treatment. This difference was informed by previous neck pain trials conducted by our group (19, 25) and the ability to detect a small to medium effect size. We used an SD of 1.8 for our pain scale on the basis of our pilot study and estimates from the literature (25, 38). With a power of 0.90 and a 3-group design tested at an α level of 0.05 (2-tailed test), 75 participants per group were required (SPSS SamplePower 1.0, International Business Machines, Armonk, New York). To allow for a loss to follow-up rate of up to 15%, we aimed to recruit 90 participants per group for a total of 270 participants.In primary analyses, we evaluated changes in neck pain between baseline and week 12 and performed longitudinal analyses by using data from weeks 2, 4, 8, and 12 (short-term outcome). In secondary (exploratory) analyses of both primary and secondary outcomes, we evaluated changes in participant-rated outcomes between baseline and weeks 2, 4, 8, 12, 26, and 52 and performed longitudinal analyses by using data from weeks 2, 4, 8, 12, 26, and 52 (long-term outcome). Both analyses were conducted by using linear mixed-model analysis with the MIXED procedure in SAS, version 9.1 (SAS Institute, Cary, North Carolina), with baseline values as outcomes (39–42). Clinical and demographic variables showing group differences at baseline were used as covariates in the analysis if they were at least moderately correlated with changes in outcomes (43, 44).The study database was prepared by data managers who were blinded to study allocation. The intention-to-treat principle was adhered to by including all participants with baseline data in the analyses, regardless of loss to follow-up. To protect against increased risk for type I errors, we used the Fisher (protected) least-significant-difference test (45, 46). The mixed-model analysis included all participants who had at least baseline assessments. In the event of missing data, the reasons were explored and the pattern of the missing data was determined to select the best method of data imputation. The original analyses were then repeated as sensitivity analyses with fully imputed data by using the MI procedure in SAS, to assess the effect of the missing data (47–51). No prespecified thresholds for clinically important group differences were set because none has been established in the literature. To facilitate interpretation of the magnitude of group differences, responder analyses were conducted by group for pain reduction (absolute risk reduction) of 50%, 75%, and 100% (including 95% CIs) at the end of treatment and at 26- and 52-week follow-up (52–55).

Role of the Funding Source

Our trial was funded by the National Center for Complementary and Alternative Medicine, National Institutes of Health. The funding source had no role in the study design, collection, analysis, data interpretation, or writing of this article.

Results

We evaluated 504 persons for eligibility, of whom 272 were randomly assigned: 90 to the medication group, 91 to the SMT group, and 91 to the HEA group. The Figure summarizes recruitment, participation, and attrition.