Spine J. 2012 (Nov); 12 (11): 1021–1028 ~ FULL TEXT
Howard Vernon, DC, PhD, John J. Triano, DC, PhD, Kim Ross, DC, PhD,
Steven Tran, BSc, David Soave, MSc, and Maricelle Dinulos, BIS, CCRP
Canadian Memorial Chiropractic College,
6100 Leslie Street,
Toronto, Ontario, M2H 3J1
BACKGROUND CONTEXT: No clinical trial of spinal manipulation for chronic neck pain (NP), for either single or multiple intervention session(s), has used an effective manual sham-manipulation control group.
PURPOSE: Validate a practical sham cervical high-velocity low-amplitude spinal manipulation.
STUDY DESIGN/SETTING: Randomized experimental validation study in an institutional clinical research laboratory.
PATIENT SAMPLE: Eligible subjects were males and females, 18 to 60 years of age with mechanical NP (as defined by the International Association for the Study of Pain Classification) of at least 3 months' duration. Subjects with arm pain, any pathologic cause of NP, or any contraindication to spinal manipulation were excluded.
OUTCOME MEASURES: The primary outcome was the patient's self-report or registration of group allocation after treatment. Secondary outcomes were numerical rating scale-101 for NP, range of motion (ROM; by goniometer), and tenderness (by pressure algometry).
METHODS: Eligible subjects were randomly allocated to one of two groups: real cervical manipulation (RM) or sham cervical manipulation (SM). All subjects were given two procedures in sequence, either RM+SM or SM+SM. Immediately after the two procedures, subjects were asked to register any pain experienced during the procedures and to identify their treatment group allocation. Force-time profiles were recorded during all procedures. Secondary clinical outcome measures were obtained at baseline, 5 and 15 minutes after the intervention, including ROM, self-report of pain, and local spinous process tenderness. Data for each variable were summarized and tested for normality in distribution. Summary statistics were obtained for each variable and statistically tested.
RESULTS: Sixty-seven subjects were randomized. Data from 64 subjects (32 per group) were available for analysis. There were no significant differences between the groups at baseline. One adverse event occurred in the "real" group, which was a mild posttreatment pain reaction lasting less than 24 hours. In the RM group, 50% of subjects incorrectly registered their treatment allocation; in the sham group, 53% did so. For the SM group, none of the procedures resulted in cavitation, whereas in the RM group, 87% of procedures resulted in cavitation. There were no significant changes between groups on pain, tenderness, or ROM. Force-time profiles of the RM and SM procedures demonstrated fidelity with significant differences between components as intended.
CONCLUSIONS: The novel sham procedure has been shown to be effective in masking subjects to group allocation and to be clinically inert with respect to common outcomes in the immediate posttreatment stage. Further research on serial applications and for multiple operators is warranted.
From the FULL TEXT Article:
Neck pain is a very common problem, second only to low back pain in its frequency both within the general population [1–6] and in musculoskeletal practice [7–9]. Approximately 15% of females and 10% of men suffer with chronic neck pain at any one time [4–6]. Chronic neck pain produces a high level of morbidity by affecting occupational and avocational activities of daily living and by affecting quality of life [10–18].
A variety of conservative treatments are available for chronic mechanical neck pain. One commonly used treatment, spinal manipulation (SM), is recommended by several evidenced-based guidelines for patients without severe or progressive neurological deficits [19–26]. There is a wide range of terms often grouped under the heading of SM that currently show limited differences with respect to clinical effectiveness, but are mechanically distinct. One classification system of procedures provides four clusters based on mechanisms of treatment delivery and include: continuous passive motion, mobilization, high-velocity low-amplitude (HVLA) and mechanically assisted . The differences in procedures rely upon cyclical repetition versus single impulse loading with user variability on frequency, force and postural displacement amplitudes. Mechanically assisted procedures couple use of segmented tables with moving sections that guide patient body segments in controlled cyclical ranges of motion or that drop under force control to assist in developing an impulse load during manual force applications. Other applications include hand held probes that direct a brief impulse to a target site.
Recently, Vernon et al.  identified clinical trials that had utilized control procedures. Twenty-one trials were identified, four of which employed some form of placebo or sham control [29–32]. None of the trials of manipulation for neck pain or for headache [28–32], employed an effective manual sham manipulation procedure. Sham/placebo/mimic procedures have been attempted, with limited success, for treatment in the lumbar spine [33–36].
Strong placebogenic effects have been hypothesized for manipulation [37–40] resulting from manual contact, personal attention and provider enthusiasm. Placebo or sham- controlled studies are necessary to determine whether results of treatment are related to the degree that the clinical outcomes are attributable to the intervention as an active factor rather than to non-specific effects. A valid sham manipulation procedure is critical for future studies in the efficacy of spinal manipulation through randomized clinical trials. We hypothesized that a novel sham cervical manipulation based on core elements of the patient experience during a procedure, would result in blinding of subjects so that their ability to accurately detect their group assignment would be no greater than chance.
To our knowledge, this is the first study to demonstrate the validity of a sham cervical manipulation procedure. The critical features of this procedure can be divided into two categories: intrinsic and extrinsic. The intrinsic features include: systematic accounting for multiple sensations that the subject may experience during treatment including auditory, movement and skin surface loading cues as well as the consistent application of procedural forces that are quantitatively different between groups. The extrinsic feature is that the sham manoeuvre was performed twice, once on each side in the SM group (double placebo manoeuvre). Both features are believed to act in concert to influence the subject’s ability to identify treatment allocation.
Machado et al.  described the ideal attributes of a placebo treatment as having two components: inertness, meaning no known or substantiated therapeutic mechanism; and, mimicry of the index treatment. An inert placebo which mimics the index treatment in all aspects, including the replication of any common side effects is termed “indistinguishable”. When side effects are absent, the placebo is said to have “structural equivalence”, where, at minimum, the registration of group allocation is no better than chance. When these criteria are applied to the sham treatment in this study, the lack of change in measures of pressure pain threshold, spontaneous pain by NRS101 (Table 2) and range of motion after a single treatment application suggest that the sham procedure is clinically inert. More patients reporting improvement in pain following treatment were in the RM group (38% vs 28% in the sham group); however, this study was not designed for nor did it have sufficient power for this comparison.
With regard to masking of group registration, the results are consistent with Machado et al.’s qualification of a “structurally equivalent”  placebo. This is especially noteworthy given that almost all participants had had prior experience with cervical manipulation, with many having current treatment. The use of a “double” administration of treatment that paired sham with real or sham with sham in a dual maneuver mimics the common occurrence in practice where more than one procedure may be applied to the neck. At the same time it holds a potential advantage of increasing the ambiguity in the subject’s experience as to which element the operator intends to be therapeutic. While the sensory input to the subject was comparable with respect to manual touch, head positioning, movement and sudden noise the force-time history of the applied loads demonstrate clearly the successful dampening of loads (Table 4) to a range of 10% to 50% of the treatment loads. The sole larger force in the antero-posterior direction matches the force necessary to trip the cam-drop mechanism and is independent of the treatment forces.
An obvious advantage of our procedure is that it is a manual sham maneuver making it a desirable comparison to other manual methods. Previous randomized clinical trials of manipulation have employed other forms of placebo or sham control [28–32]. Two studies employed a de-tuned therapy instrument [31, 32] whereas Sloop et al.  employed a manipulation under anamnestic valium administration, attempting to avoid all sensory cues. Only Vernon et al.’s trial  for manipulation and tension-type headache attempted a manual sham manipulation procedure , but this was in conjunction with a placebo version of a medication, creating a double-placebo condition that did not permit the identification of the separate effect of the manual sham.
An observation noted on secondary analysis, is the tendency of subjects, when their clinical findings improve to a minimum clinically important difference of 20%, to identify their group allocation as being RM, regardless of their actual group assignment. This happened in 83% and 23% of the subset of subjects who achieved a minimum clinically important improvement in the real and sham treatment groups, respectively. This may provide a means in future studies to begin understanding those who are sometimes called placebo responders [35–38, 40, 59].
The most important limitation of this study is that the findings apply only to a single treatment over a 24-hour investigative interval. It is not known if these procedures can sustain similar levels of blinding and, in the case of the sham manipulation procedure, the same levels of inertness over a series of treatments over intervals of many days. This is a critical topic for future research. Future studies should also address subject’s baseline clinical expectations as well as the reason(s) they give for their post- intervention group registration.
The double-treatment method of pairing real-sham and sham-sham procedures using carefully selected physical components that systematically account for patient experience during manipulation provides an effective and inert sham/placebo for manual manipulation of the cervical spine.