Manual and Mechanically Assisted Adjustment Methods: Are They Therapeutically Equal?
RESEARCH REVIEW
Michael Schneider
The use of mechanical devices such as the Activator instrument for adjusting patients has become very popular. According to job analysis surveys by the National Board of Chiropractic Examiners (1,2), about 70% of chiropractors now report that they use the Activator or some other type of handheld adjusting instrument. Many chiropractors use mechanical devices to adjust the spine and extremities as a substitute for manual adjustments, especially with pediatric and geriatric patients. This substitution is based on an assumption that both methods of adjusting aie equally effective and that handheld mechanically assisted adjustments are somehow safer in these special populations of patients. The purpose of this article is to stimulate thought and discussion about the use of mechanical devices in chiropractic practice, and to review the research evidence about handheld mechanical adjusting methods.
The various types of handheld adjusting devices fall into two broad categories: spring-loaded or electromechanical. The most popular handheld spring-loaded adjusting device is the Activator adjusting instrument (AAI), models I, II, III and IV. Popular handheld electromechanical devices include the PulStar and the Impulse adjusting instruments. There is also an electromechanical version of the Activator instrument, the AAI V. These handheld devices, whether spring-loaded or electromechanical, differ with respect to the force generated and whether single or multiple thrusts are generated. All five models of the Activator instrument deliver a single thrust, whereas the PulStar and Impulse adjusting instruments deliver multiple thrusts.
Contrary to what is generally assumed, there is not a lot of high-quality research evidence to support the notion that manual and mechanically assisted types of spinal adjusting are clinically equivalent methods. Although it is common to see and hear reports that more than a hundred research studies have been conducted on mechanically assisted adjusting methods, the vast majority of that research did not use rigorous, controlled experimental designs. In fact, there are only five randomized controlled trials that have made a comparison between the use of an Activator device and a manual adjusting method—two trials for patients with neck
^Contrary to what is generally assumed, there is not a lot of high-quality research evidence to support the notion that manual and mechanically assisted types of spinal adjusting are clinically equivalent methods. ï Ï
pain(3>4) and three trials for patients with low back pain (5-6-7). However, there have not been any clinical trials published that compare the clinical effectiveness of an electromechanical adjusting device with an Activator instrument, or with any manual adjusting methods.
The majority of research studies on handheld mechanical adjusting devices have been conducted in the laboratory, or in the form of single case reports or case series.
Most of the early research studies on handheld adjusting devices were performed on animals in the laboratory setting, measuring the speed and amount of force generated by the devices. Measuring the forces and vertebral motions produced in the spines of rats, pigs, or sheep by a handheld adjusting device is not the same as measuring clinical outcomes, such as reductions in pain or improvement of physical function in human patients.
Research on manual adjusting methods differs in some very important ways. Like the handheld instruments, there is a large amount of basic science and laboratory research measuring the speed and force produced by manual thrust techniques. However, there is also substantial research evidence from multiple clinical trials showing that manual adjusting methods lead to significant reductions in human patients with neck and low back pain. The vast majority of these
^Measuring the forces and vertebral motions produced in the spines of rats, pigs, or sheep by a handheld adjusting device is not the same as measuring clinical outcomes, such as reductions in pain or improvement of physical function in human patients. J J
research studies involve a comparison between manual manipulation and another type of treatment, such as usual medical care, which provides strong evidence for the clinical effectiveness of manual adjusting methods(8).
To date, there are very few well-designed research studies that compare the clinical effects of manual versus mechanically assisted types of adjusting. Furthermore, there are virtually no clinical trials comparing the effectiveness of spring-loaded versus electromechanical types of adjusting devices. Many of the previous clinical trials involving Activator could be characterized as exploratory pilot studies, with an extremely small number of patients and inconclusive findings. These studies typically found that patients in both groups improved, regardless of the type of adjusting (manual or Activator), and that there was no statistically significant difference between manual and Activator adjustments. It is tempting—but erroneous—to draw the conclusion that these results suggest that Activator and manual adjustments lead to therapeutically equivalent results.
■ "The first is that manual adjustments lead to much better short-term outcomes for acute and subacute back pain, compared to medical care. J Ï
There are several challenges with the design of most previous studies comparing Activator with manual adjusting techniques. The first challenge is that most trials did not include a control or usual medical care group. This is a critical part of research design because patients may improve due to the natural history of back and neck pain, and not due to either the manual or Activator adjustments. In fact, only the most recent trial comparing Activator with manual adjustments has a control group that didn’t receive any type of chiropractic adjustment.
The second challenge has to do with the extremely small number of patients (sample size) enrolled in these studies, typically fewer than 15 patients per group. To detect clinically meaningful differences between the two adjusting methods in these small studies, there would need to be extremely large differences in the outcomes between the groups. Even if a clinically meaningful difference were found between the two groups, it likely would not achieve statistical significance with such a small sample size. Researchers call this being “underpowered,” and most of the previous Activator clinical trials suffered from being underpowered. Most researchers like to see sample sizes on the order of 30 to 50 patients per group (or more), as well as some type of control treatment, in order for the study’s results to be considered meaningful.
The largest randomized clinical trial ever conducted on the topic of instrument versus manual adjustments for low back pain was recently published in Spine(7). This study involved 107 patients with acute and subacute low back pain who were assigned to one of three treatment groups:
1) manual side-posture adjustments;
2) Activator adjustments; and
3) usual medical care. The two chiropractic groups received eight adjustments during a four-week period (twice a week) and the medical group received three office visits during four weeks. The results showed that patients in all three treatment groups improved at four weeks compared to baseline. There was no significant difference in treatment outcomes between the Activator and medical care groups. However, the surprising result was that at the end of four weeks, a significantly greater proportion of patients in the manual adjusting group achieved clinically important reduction in pain and improved function, compared to either the Activator or medical care groups. At
six months, the differences between groups slowly faded, and there was no longer any statistical difference between the three groups.
There are several important clinical implications to be gleaned from this new study. The first is that manual adjustments lead to much better short-term outcomes for acute and subacute back pain, compared to medical care. When a patient asks his or her medical doctor about whether chiropractic care is indicated and an effective treatment option, the honest answer must be, “Yes.” The second important finding is that we need to question the assumption that manual adjusting methods and adjustments with the Activator device have therapeutically equal results. When a patient asks about whether the Activator has the same treatment effect as a manual adjustment, the honest answer must be, “No”; at least for acute and subacute low back pain, manual adjustments appear to be more effective. The third important implication is that Activator did as well as or slightly better than usual medical care, so it could still be a reasonable treatment option for patients who do not want a manual type of adjustment and are not interested in taking medications.
There seems to be a pervasive attitude in the chiropractic profession that “all techniques work the same, so just pick one that works for you.” Is it a reasonable assumption that all techniques are equally effective for all patients and for all conditions? It would seem more reasonable to expect that certain patients may do better with certain techniques. For example, although Activator did not seem to be as clinically effective as manual adjusting for patients with low back pain, it may be as effective as manual adjustments for patients with neck pain. In addition, future research may show that manual adjustments work better for patients with neck pain as compared to Activator adjustments, but at this point, we just don’t know.
When we think about all of our other chiropractic techniques, there are many clinical questions waiting to be answered from well-designed research studies. For example, is flexion-distraction better than side-posture adjusting for patients with lumbar disc protrusions and sciatica? Are the socalled “decompression” tables better than flexion-distraction or manual adjusting techniques for disc patients? What is the effectiveness of nonthrust techniques, such as pelvic blocking, when compared with manual adjusting techniques for low back or sacroiliac joint dysfunction? These types of “comparative effectiveness” research questions ai e probably going to require funding from chiropractic sources because federal agencies, such as the National Institutes of Health, are not likely to use taxpayer money on studies of such specialized interest to just one profession.
It’s time for the chiropractic profession to stop assuming that all techniques are equivalent. Given the lack of research comparing different techniques, it is difficult to make choices about which method to use with which patient. Ultimately, the
decision should come down to the three pillars of evidencebased practice (9):
1) using the best current evidence combined with
2) the clinical experience of the provider, and blended with
3) the patient’s preferences. So it’s important for chiropractors to have several adjusting techniques in their clinical toolbox, based upon different clinical presentations and different patient preferences. However, let’s recognize that the clinical evidence for mechanical adjusting instruments is not very strong as this time. More clinically relevant research studies need to be conducted that compare both singleand multiple-thrust adjusting instruments with manual adjusting techniques.
References:
1. Christensen MG, Kerkhoff D, Kollash MW. Job Analysis of Chiropractic. 2000, Greeley, CO: National Board of Chiropractic Examiners.
2. Christensen MG, Kollash M, Ward R, Webb K, Day M, zum Brunnen J. Job Analysis of Chiropractic. 2005, Greeley, CO: National Board of Chiropractic Examiners.
3. Yurlciw D, Mior S. Comparison of two chiropractic techniques on pain and lateral flexion in neck pain patients: a pilot study. Chiropractic Technique. 1996.8:155-162.
4. Wood TG, Colloca CJ, Mathews R. A pilot randomized clinical trial on the relative effect of instrumental (MFMA) versus manual (HVLA) manipulation in the treatment of cervical spine dysfunction. J Manipulative Physiol Ther. 2001;24:260-271.
5. Gemmell HA, Jacobson BH. The immediate effect of Activator vs. Meric adjustment on acute low back pain: a randomized controlled trial. J Manipulative Physiol Ther. 1995; 18(7):453—456.
6. Shearer KA, Colloca C, White H. A randomized clinical trial of manual versus mechanical force manipulation in the treatment of sacroiliac joint syndrome. J Manipulative Physiol Ther. 2005;28:493-501.
7. Schneider M, Haas M, Glick R, Stevans J, Landsittel D. Comparison of spinal manipulation methods and usual medical care for acute and subacute low back pain: a randomized clinical trial. Spine. 2015;40(4):209-17.
8. Bronfort G, Haas M, Evans R, Leininger B, Triano J. Effectiveness of manual therapies: the UK evidence report. Chiropr Osteopat. 2010; 18:3.
9. Straus SE, Glasziou P, Richardson W, Haynes RB. EvidenceBased Medicine. Churchill Livingstone Elsevier. Fourth edition. 2011.
Dr. Schneider is a graduate of Palmer College of Chiropractic. He completed a PhD in Rehabilitation Science at the University of Pittsburgh, where he is an Associate Professor in the School of Health and Rehabilitation Sciences. He is the recipient of several Federal research grants and is a full-time clinical researcher. He can be reached at 412.383.6640.
