Spinal manipulative therapy and exercise for older adults with chronic low back pain: a randomized clinical trial

The trial was conducted at Northwestern Health Sciences University (Minneapolis, Minnesota). Participants were recruited through newspaper advertisements, direct mail, and community posters. Interested individuals were initially screened by telephone interview, followed by two in-person baseline evaluation visits.

As individuals became eligible, study staff masked to upcoming treatment assignments used sequentially numbered opaque envelopes prepared by an independent study statistician to allocate participants to an intervention group. The blocked randomization scheme used a 1:1:1 allocation ratio with randomly permuted block sizes that were concealed from the study team to ensure they were masked to the sequence of treatment assignments.

All participants received 12 weeks of care in one of three treatment groups: 1) Home Exercise Program (HEP); 2) Supervised Exercise (SEP) + HEP; or 3) Spinal Manipulative Therapy (SMT) + HEP. Individuals were asked to refrain from seeking any additional treatment for their back pain during the treatment period. The three treatment programs are described in detail in Table 1, and in a previous publication [19]. The HEP and SEP programs were delivered by 9 exercise therapists and 2 chiropractors, and the SMT was delivered by 11 licensed chiropractors with a minimum of 5 years practice experience. All providers underwent training and certification with study investigators to standardize delivery. Intervention activities were documented on standardized forms and monitored for compliance.

Outcomes were measured by patient self-report questionnaires, blinded objective assessment, and in- person and telephone interviews. Patient self-report questionnaires were collected at baseline, and 4, 12, 26, and 52 weeks post-randomization. Participant flow, study visits, and evaluations are outlined in Fig. 1.

An intention-to-treat approach was used, analyzing all observed data from participants according to their randomized treatment assignment. Data analyses were performed in STATA, version 13.0 (StataCorp 2013, Stata Statistical Software: Release 13, College Station, TX; StataCorp LP). The statistician was blinded to group allocation for all analyses. The primary and secondary outcomes were analyzed using linear mixed effect models including fixed effects for time, treatment, and a time-by-treatment interaction, and a random intercept to account for within-subject correlation. The model included the baseline outcome as a covariate (when appropriate).

A summary of patient recruitment, participation, treatment adherence, and attrition during the study is shown in Fig. 1. Participants were recruited between 2004 and 2006, with follow-up data collection completed in 2007. A total of 550 individuals were evaluated for the study, of which 241 were randomized. Demographic and baseline clinical characteristics of all randomized participants are displayed in Table 2. Randomization resulted in three groups comparable on most baseline variables with four potentially important exceptions: age, gender, duration of LBP and treatment effect expectation (Table 2). None of these variables were more than weakly correlated with the primary outcome (absolute values from 0.04 to 0.23), and thus were not included as covariates in the analyses.

Detailed results from the responder analyses are provided in Table 4. The proportion of participants reporting reductions in pain severity across all possible thresholds is shown in Fig. 3. Differences in proportions for reduction of LBP severity were mostly below 10%. The largest differences were for SMT + HEP over HEP alone at week 12 where 16 and 18% more participants had pain severity reductions of 30 and 50%, respectively.

The secondary outcomes followed a similar pattern with no important group differences. The exception was satisfaction with care, where the two combination groups (SMT + HEP, SEP + HEP) were superior to home exercise alone at all time points (see Table 3). Except for a few small differences favoring SEP + HEP over SMT + HEP for flexion static endurance and hand grip strength, the objective outcomes showed the same pattern as the patient rated outcomes (see Table 5). Health care and societal cost comparisons along with cost-utility and cost-effectiveness analyses will be addressed in a separate publication.

Six serious adverse events occurred during the trial, all were determined to be unrelated to study interventions. These include: one hospitalization for cholecystectomy and one death due to lung cancer in the HEP group; one hospitalization for acute cardiac symptoms, one new diagnosis of prostate cancer, one injury attending a hockey game, and one transient ischemic attack during follow up phase (not actively in intervention) in the SMT + HEP group; and none in the SEP + HEP group.

A limited number of trials have assessed non-pharmacological treatments for the management of low back pain in older adults and to our knowledge, this is the first randomized trial assessing the effectiveness of adding spinal manipulation or a supervised exercise program to a home exercise program in this population. Our primary analysis showed that adding spinal manipulation or a supervised exercise program to a home exercise program did not result in significant or meaningful advantages in pain severity over the course of one year (differences in long-term pain profiles between 0 and 2 percentage points). Secondary analyses showed that at the end of the 12-week treatment phase, group differences favored the addition of SMT or SEP to HEP by 8 and 4 percentage points, respectively. Group differences following the end of treatment were smaller (0 to 3 percentage points) and favored HEP alone over the combined groups. Differences in secondary patient-rated outcomes were small and did not show any clear pattern in favor of one treatment group over another. An exception was satisfaction with care, where participants in both SMT + HEP and SEP + HEP consistently reported greater satisfaction than those in the HEP group throughout the year.

A number of factors beyond the magnitude of group differences must be considered when interpreting clinical importance. This includes the magnitude of group differences, proportion of responders, consistency of outcomes, durability of treatment effects, intervention safety and tolerability, treatment adherence, and costs [42]. The magnitude of group differences in pain severity were below the threshold of a moderate effect size (8 percentage points) that was used to power the study, with the exception of SMT + HEP compared to HEP alone at the end of treatment. Responder analyses for reductions in pain severity showed a similar pattern with most group differences falling below 10%. The exception was also at the end of treatment where approximately 15% more participants in the SMT + HEP group reported at least some, 30%, or 50% reductions in pain severity relative to the HEP group. Importantly, following the end of the treatment phase, differences in pain severity favoring SMT + HEP over HEP were not maintained and a higher number of participants in the SMT + HEP group sought additional care. In addition, no clear and consistent pattern favoring one treatment over another was noted in key secondary outcomes that would be expected to be similar to pain severity (e.g. disability, improvement). Satisfaction was consistently higher in the combined groups relative to HEP alone. Overall, adherence to treatment regimens was high and no treatment-related serious adverse events occurred. Considering these factors in aggregate, the moderate effect at the end of treatment favoring SMT + HEP over HEP alone should be viewed with great caution. This effect was not durable over time, was not supported by other important secondary outcomes, and may not be clinically important. Differences in healthcare and societal costs are also important factors for assessing clinical importance, and will be reported in a separate publication.

Our rationale for including HEP was that it was a minimal but promising self-management intervention that would be credible to patients [19]. Self-management has been variably defined in the literature, with no commonly accepted definition [14]. Importantly, self-management (and exercise) have become recognized as types of behavior change interventions, which are a coordinated set of activities aimed at changing specified behavior patterns [46]. This is important as the science of behavior change is advancing rapidly with the development of validated reliable taxonomies of behavior change techniques [47‐49]. This contemporary understanding allows for the characterization of active ingredients of interventions, like self-management, which may have so far, gone unidentified. This leads us to surmise that our control intervention, HEP, might not have been as inert or minimal as originally anticipated and may explain at least in part, the lack of observed group differences. This issue will be further examined in future analyses.

The most recent systematic review to address non-pharmacologic treatments for chronic LBP has found evidence of modest short-term improvements in function and/or pain for both exercise and spinal manipulation when compared to usual care, attention control, sham, or placebo, and no clear differences between exercise and spinal manipulation [11]. The results of our study found no difference between SMT + HEP and SEP + HEP and thus appear to confirm the lack of appreciable difference between exercise and SMT as individual modalities. In addition, we found that adding SEP or SMT to HEP does not result in clinically meaningful improvements for older adults with chronic LBP.

A systematic review of manual therapies for older adults found evidence to support its use based on a small number of studies [15]. Not included in that review were three noteworthy studies evaluating SMT for older adults with LBP. The study by Hondras et al. [16] compared two types of SMT (low and high velocity thrust) to medical management in 241 patients 55 years older with subacute and chronic LBP (mean duration more than 12 years). There was no important difference in effectiveness of the two types of SMT, and the low velocity manipulation resulted in small but clinically important short and mid-term improvement in functional status when compared to medical management. Goertz et al. [17] conducted a randomized controlled trial with 131 community-dwelling, ambulatory older adults ages 65 and older with subacute or chronic LBP (84% reporting current LBP episode duration > 1 year). Participants were randomly allocated to 12 weeks of individualized primary medical care (medical care), concurrent medical and chiropractic care consisting primarily of SMT (dual care), or medical and chiropractic care with enhanced interprofessional collaboration (shared care). There were no statistically significant or important differences found between the three groups on the primary measures of low back pain and disability. Finally, a randomized trial by Maiers et al. [50] compared 12 weeks of SMT plus supervised exercise to 36 weeks of the same treatment in 182 adults 65 years of age and older with concurrent low back and neck pain. No significant group differences were observed in low back related disability, the primary outcome measure.

Our trial has several strengths, including adequate sample size, and a rigorous design with emphasis on internal validity. We also had excellent engagement and follow up rates. Limitations of the study include inability to blind patients and providers to the nature of the interventions. We also did not measure potentially important outcomes or mediators of outcome, including pain catastrophizing, self-efficacy, and therapeutic alliance which are potentially important for older individuals suffering from pain. Also, while we were unable to control for contextual effects which may explain differences in satisfaction, the interventions did approximate what could occur in clinical practice, and are therefore more readily applicable for dissemination.

When considered in aggregate, the findings of this study suggest that a four-session home exercise program is a viable treatment option for seniors with chronic LBP. This is supported by the observation that individuals in the HEP group had a similar course of pain over a one-year period to a comparable population of older adults managed in primary medical care [51]. For patients requiring more support, adding spinal manipulation or supervised exercise may be prudent next step.

Our findings, especially when considered in light of the cumulative research on non-pharmacologic treatments, including SMT and exercise for low back pain [11, 12] suggest that it may be time to take a step back and re-evaluate how to study this prevalent and costly condition. One such approach may be to learn from the advances in behavioral research focused on the promotion of healthy behaviors, and start focusing more on adaptive pain management behaviors (e.g. more physical activity, self-efficacy and adaptive coping, and less health care utilization, medication use, etc.) and less on the pain symptoms [52]. Further, a more clear delineation of the behavioral components that are likely embedded, but currently unrecognized, in the experimental and control interventions is warranted.