Research Review By Special Guest Reviewer Dr. Mitchell Haas©


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Date Posted:

January 2014

Study Title:

Dose-response and efficacy of spinal manipulation for care of chronic low back pain


Haas M, Vavrek D, Peterson D, Polissar N, Neradilek MB

Author's Affiliations:

Center for Outcomes Studies, University of Western States, Portland, OR, USA.

Publication Information:

Spine Journal 2014; 14: 1106-1114.

Background Information:

Chronic low back pain (cLBP) is a prevalent and costly condition that is commonly treated by chiropractors, physiotherapists and other manual medicine providers. Yet, there has been no consensus on the total number of visits, duration of care, and frequency of spinal manipulation provided by a clinician for the care of this condition. A previous pilot study investigating spinal manipulation in the treatment of cervicogenic headache evaluated the effects of three to 12 visits and gave preliminary support to the superiority of a greater number of visits for pain outcomes (1).

The purpose of this full-scale randomized controlled trial was:
  1. To identify the optimal dose (number of visits) of spinal manipulation for the care of cLBP; and
  2. to determine the efficacy of spinal manipulation dose by comparison to a light massage control intervention.

Pertinent Results:

Study Population:

The mean age of study participants was 41.3 years. Half were women and 15% were non-white or Hispanic. About half had a college degree and a third were married. Half reported at least one comorbid condition. Mean baseline pain was 51.6 and mean functional disability was 45.3 on 0 to 100 scales. Participants reported a mean duration of 12 years for their low back pain. They were experiencing low back pain about six days per week and taking nonprescription pain medication twice per week at baseline prior to randomization.

Primary Outcomes:
  • Mean pain and functional disability improved 20 points (0 to 100 scale) by 12 weeks after randomization, six weeks after completion of care, and was sustainable to 52 weeks.
  • At 12 weeks (1st primary endpoint), the greatest differences from the no-manipulation control were found for 12 sessions (pain: mean difference = 8.6, 95% CI = 3.2 to 14.0, P < .025; disability: mean = 7.6, 95% CI = 1.7 to 13.3, P < .025).
  • At 24 weeks (2nd primary endpoint), differences were negligible. At 52 weeks, the greatest group differences were seen for 18 visits (pain mean difference = 5.9, P < .025; disability mean difference = 8.8, P < .025).
  • The dose-response effects for pain and disability scores were small. There was about a two-point better score for each additional six manipulation sessions observed at 12 and 52 weeks for both variables (P < .025).
  • We conducted a responder analysis where the outcome was a 50% improvement from baseline scores. About 30% to 50% of participants achieved 50% improvement in pain at the 6-week to 52-week follow-ups. Also, about 40% to 60% of individuals achieved 50% improvement in disability scores.
Secondary Outcomes:
  • These outcomes showed improvement within each group that was sustainable for the duration of the study. However, the control group improvement was of such magnitude that there were few meaningful differences between study dose groups and control group. Pain unpleasantness was reduced by about 20 points, similar to pain magnitude. There was a reduction of one to two days per week with pain. There was also a small reduction in pain medication use after completion of study care at six weeks. It took three to six months for the physical health component of the SF-12 to return to US population norms.

Clinical Application & Conclusions:

For chronic, non-specific low back pain, the best results in terms of pain intensity and functional disability were found for 12 sessions of spinal manipulation from a chiropractor in a six-week period of time. Average improvement for participants receiving this dose was substantial at the end of care and sustainable to one year. Half of patients were able to achieve 50% improvement in pain/disability. However, a recommendation of 12 visits must be made with caution because the gradient of treatment effects across dose groups was too small to clearly distinguish 12 visits from adjacent dose levels.

The effect of continuity of care is still unknown, so both ongoing patient monitoring and clinical judgment are required for determining the total number of spinal manipulations. More than 12 visits in six weeks are unlikely to improve patient outcomes.

Finally, it must be noted that the effect of spinal manipulation above and beyond the effect of a brief, focused light massage (control) was at best modest.

Study Methods:

This was a practice-based, prospective, open-label, parallel groups randomized controlled trial. A total of 400 participants were randomized to receive 0, 6, 12, or 18 visits to a chiropractor for spinal manipulation.

All participants were assigned three visits per week for six weeks. Spinal manipulation was performed at the assigned number of visits, and a brief, light massage was performed at non-manipulation visits as a hands-on control. Follow-up by mail questionnaire or blinded phone interview was conducted after 6, 12, 18, 24, 39, and 52 weeks.

The primary outcomes were specified in advance as pain intensity and functional disability at the 12-week (short-term) and 24-week (long-term) follow-ups.

Study Participants:
Participants were 18 years and older. They had to have at least 30 days of nonspecific back pain of mechanical origin in the previous 6 weeks, with the current episode of low back pain lasting at least three months. A minimum pain index of 25 on a 100-point scale was required.

Participants were excluded if they had received manual therapy in the previous three months, and for contraindications to spinal manipulation and complicating conditions such as cancer, inflammatory arthropathies, neurodegenerative disease, and referred back pain of organic origin.

All study care was provided by 12 chiropractors with four to 24 years of practice experience. The participant chose their study chiropractic clinic for convenience to help optimize adherence to scheduled study visits. All visits were 15 minutes in duration, starting with 5 minutes of patient interview and hot pack to relax the participant’s back. Treatment was then administered for 5 minutes. The final 5 minutes included low-dose, pulsed ultrasound (20% duty cycle with 0.5 watts/cm2) as a quasi-sham to augment treatment credibility.

The study intervention was high velocity low amplitude, thrust manipulation of the lumbar spine, predominantly in side posture. The light massage control was 5 minutes of gentle effleurage and petrissage focused on symptomatic areas of the low back.

Outcome Measures:
The primary outcomes were the self-reported Modified Von Korff pain and disability scales (2). The pain score is the average of three 0 to 10 numeric rating scales converted to a100-point scale: back pain today, worst back pain in the last four weeks, and average back pain in the last four weeks.

The disability score is the average of interference with daily activities, social and recreational activities, and the ability to work. Secondary outcomes included pain unpleasantness, SF-12 physical and mental summary scales, number of low back pain days and disability days, and medication use.

Regression models were used to determine the linear effect of dose across the four study groups (0, 6, 12, and 18 manipulation sessions) and to compare the manipulation groups with the no-manipulation control group. All comparisons were adjusted for six baseline covariates. A longitudinal analysis of the outcomes profile across all follow-up was conducted using generalized estimating equations. A responder analysis using binomial regression was used to compare groups in terms of achieving 50% improvement in outcomes. The sample size was chosen to give 80% power to detect a 10-point difference between groups in pain and disability scores at the .025 level of significance (to correct for two outcome measures).

Study Strengths / Weaknesses:

The major strength and weakness of this study is one and the same. The extensive control of contact in terms of number and length of visits, hands on with a very light massage, and doctor-patient interaction permitted the study to isolate the efficacy of spinal manipulation above and beyond other contextual effects of care. However, this came at the expense of generalizability to practice because the study did not include all the effects of the care encounter as part of the intervention and did not include physical and other modalities used by clinicians.

Additional References:

  1. Haas M, Spegman A, Peterson DH, Aickin M, Vavrek D. Dose-response and efficacy of spinal manipulation for chronic cervicogenic headache: a pilot randomized controlled trial. Spine J 2010; 10(2): 117-28.
  2. Underwood MR, Barnett AG, Vickers MR. Evaluation of two time-specific back pain outcome measures. Spine 1999; 24: 1104-12.