Research Review By Dr. Michael Haneline©

Date Posted:

July 2010

Study Title:

Mechanical vs. manual manipulation for low back pain: An observational cohort study


Schneider M et al.

Author's Affiliations:

School of Health and Rehabilitation Sciences, University of Pittsburgh, Penn. USA.

Publication Information:

Journal of Manipulative & Physiological Therapeutics 2010; 33: 193-200.

Background Information:

According to a survey conducted by the National Board of Chiropractic Examiners, the Diversified and Activator Techniques are the two most common forms of spinal manipulation used by chiropractors. In the management of lower back conditions, Diversified involves a side posture manual thrust, whereas Activator involves the delivery of mechanical impulses via a handheld device. Other manual therapists also use these techniques.

Even though the Activator technique is reported to be the second most commonly used manipulative method among chiropractors, the evidence supporting its use for patients with lower back pain (LBP) is unclear. On the other hand, the evidence is strong in support of side posture manipulation for this condition.

Very few studies have contrasted the effectiveness of the various chiropractic techniques. Therefore, the purpose of this study was to discover whether the clinical outcomes of LBP patients would be different using the Activator instrument versus Diversified manual thrust manipulation for treatment.

The study also had two secondary aims:
  1. To contrast the clinical practice style and patient characteristics between chiropractic offices where the practitioners used a “treatment-as-usual” approach; and
  2. to explore the effect of treatment expectancy on clinical outcomes and see if there was an interaction effect with treatment method.

Pertinent Results:

There was a significant difference between the unadjusted mean Numeric Pain Rating Scale (NPRS) scores of the 2 cohorts at 4-weeks (mean difference = 1.2, P = 0.011), with scores in those patients who received Diversified manipulation being lower.

There was no significant difference between the unadjusted mean Oswestry LBP Disability Index (ODI) scores of the 2 cohorts at 4-weeks (mean difference = 2.9, P = 0.29), though the scores were lower for those who received Diversified manipulation.

The authors commented on the clinical patterns of care that was provided to the patients in both cohorts as follows:
  • The Activator patients had significantly more applications of electrical muscle stimulation, laser therapy, intersegmental traction (roller) table, and postural education.
  • The manual manipulation patients had significantly more applications of heat/ice packs.
  • The number of patients that required the maximum number of 8 treatments was higher in the Activator group (70%) than the Diversified manipulation group (15%).
  • 78% of the patients who received Activator continued receiving chiropractic care after the study was completed, whereas only 18% did so in the Diversified manipulation group.
  • Quite a few of the patients in the Activator group received lumbar radiographs (54%) or magnetic resonance imaging (5%), whereas none (0%) of the patients in the Diversified manipulation group did. However, significantly more patients in the Activator group had buttock and thigh pain, as well as moderate to severe limitation of lumbar flexion.
The treatment expectancy scores were significantly higher in the Diversified manipulation cohort and the authors suggested that the expectancy variable strongly pointed to expectation as a confounder between the relationships of the treatment method cohorts to the respective NPRS score outcomes.

The majority of patients in both groups received electrical muscle stimulation; even though it has shown been shown to provide little or no independent treatment effect.

Education about posture and home exercises (handout literature only) was provided to a majority of the patients in both groups, which is consistent with the best current evidence for the management of LBP.

Clinical Application & Conclusions:

One might be tempted to conclude from the results of this study that patients who receive Diversified manipulation for LBP will have better clinical outcomes than those who receive Activator manipulation. However, there are many limitations to this study (outlined below) that render this conclusion erroneous. In fact, the authors make no such statement. Also bear in mind that there were only a few chiropractors involved and positive outcomes may have merely been the result of better doctoring expertise than the type of treatment that was provided.

One can reasonably conclude from the study that there was wide variation between the clinical practice patterns and management styles between the participating chiropractors. This tendency has also been observed in other studies; for example, an observational study of chiropractic care for acute neck pain patients (1).

Treatment expectancy was found to be a surprisingly strong predictor variable. Moreover, the pretreatment beliefs in the success of treatment in pain patients have been shown in numerous studies to be one of the strongest predictors of final treatment outcomes (2). Therefore, asking new LBP patients about their treatment expectations would likely facilitate planning their care and setting realistic treatment goals.

Study Methods:

LBP patients were recruited from 3 private chiropractic clinics over a period that spanned approximately 2 years and 4 months.

Patients were included in the study if they:
  • were more than 18 years of age,
  • had acute onset LBP that had developed within the previous 12 weeks,
  • NPRS score between 4 and 8 points, and
  • ODI score between 20 and 70 percentage points.
Patients were excluded from the study if they were pregnant or had:
  • red flags of serious pathology (e.g., history of cancer, previous lumbar surgery, stenosis, instability),
  • absolute contraindications to manipulation (e.g., severe osteoporosis and prolonged use of steroids),
  • positive nerve root tension signs or sensory or motor deficit in the lower extremities, or
  • received any physical therapy or chiropractic treatment for LBP within the past 3 months.
Patients were treated in 1 of 3 private chiropractic clinics. Two Activator Methods proficiency-certified chiropractors who used the Activator Instrument exclusively to treat the study patients were in 1 of the clinics. Two other chiropractors in 2 additional offices used Diversified side posture thrust manipulation exclusively.

The participating chiropractors were instructed to treat the research patients the same way as they would normally treat any other LBP patient (i.e., using a “treatment-as-usual” approach).

The treatment period in the study started at the initial baseline visit and ended at the eighth office visit or after 4 weeks, whichever occurred first. However, if the clinicians thought the patients needed additional care beyond the eighth visit or 4 weeks, they were permitted to continue treating.

The primary outcome measure was the NPRS, and the secondary outcome measure was the ODI. Data on both were collected at baseline and at 4 weeks.

Study Strengths / Weaknesses:

The study was not a true experiment, which involves randomization to groups as well as blinding. Therefore, be very cautious about applying its findings to other populations of chiropractors and patients because much different findings could possibly be observed.

A “treatment-as-usual” research design was used in this study, which has some benefits, but limits one from drawing firm conclusions. Furthermore, patients were not randomly assigned to groups, and they self-selected their treating chiropractor as well as the method of chiropractic care they received.

Because patients were allowed to self-select their treatment method, neither the treating chiropractors nor the patients were blinded.

A control group was not utilized; only 2 groups who received different methods of treatment. This type of study design does not permit the estimation of which part of the treatment effect was caused by non-specific factors, such as the placebo effect and natural history.

Additional References:

  1. Haneline MT, Cooperstein R. Chiropractic care for patients with acute neck pain: results of a pragmatic practice-based feasibility study. J Chiropr Med. Dec 2009; 8(4):143-155.
  2. Goossens M, Vlaeyen J, Hidding A, Kole-Snijders A, Evers S. Treatment expectancy affects the outcome of cognitive-behavioral interventions in chronic pain. Clin J Pain. 2005; 21(1):18-26; discussion 69-72.