A study published in The Spine Journal examines placebos used during lumbar and pelvic joint thrust manipulation clinical trials.
The researchers included data from the Medline, Embase, Cochrane Central Register of Controlled Trials, Index to Chiropractic Literature and relevant bibliographies to gather data. The studies included were randomized, placebo/sham-controlled trials. There were two independent reviewers who assessed the study quality and data for 25 trials included in the study.
The researchers found:
1. Eighteen trials included sham manual spinal manipulation therapy for the placebo control. The most common way to approach the SMT was with the SMT set-up, but without applying any thrust.
2. Two studies used a validated insert a priori placebo.
3. Eight studies highlighted the success of subject blinding. However, the researchers found "strong potential" for unmasking control subjects due to imperfect placebos.
4. The study authors recommended further trials include an assessment of the subject blinding to determine whether it was successful.