title: A randomized trial investigating a chiropractic manual placebo: a novel design using standardized forces in the delivery of active and control treatments.
abstract: OBJECTIVE
  To evaluate the proposed manual placebo in terms of success in blinding patients to treatment group assignment and outcomes between the treatment groups.
  
  
  METHODS
  Randomized controlled trial.
  
  
  METHODS
  A chiropractic college research clinic in the midwestern United States.
  
  
  METHODS
  One hundred and eleven (111) individuals aged 18 years and over with subacute or chronic lowback pain.
  
  
  METHODS
  The active treatment consisted of flexion-distraction chiropractic manipulation and trigger point therapy and the control treatment of sham manipulation and effleurage; both groups received eight treatments over a 3-week period. The application of prescribed ranges of biomechanical forces for each treatment was standardized using specialized computerized equipment. "Nontreatment" aspects of the clinical encounter were to be standardized across groups. A primary clinician blinded to treatment assignment provided interpersonal interactions and treating clinicians delivered treatments with a minimum of interaction.
  
  
  METHODS
  The accuracy of the patient's perception of group assignment at visit 4 and the mean change in the Pain Disability Index (PDI) over the treatment period were the primary outcome variables.
  
  
  RESULTS
  Patients in the control group were more likely to perceive their treatment assignment accurately than those in the active group (78% versus 54%, respectively). Patients in both treatment groups improved on the PDI and the Roland-Morris Questionnaire; there were no significant differences in improvement between the groups. Age, gender, prior chiropractic experience and expectation of treatment at baseline had no effect on outcomes.
  
  
  CONCLUSIONS
  Patients in the control group were not successfully blinded; however, patients' perceptions of treatment group assignment did not significantly affect outcomes. The clinically significant improvement in both groups, independent of patient or clinician expectations, suggests the presence of therapeutic factors common to both groups, other than biomechanical force. Further studies examining other aspects of the clinical encounter, considered separately from biomechanical force, are warranted before arbitrarily designating any intervention as a "placebo."
authors.affiliation: Parker Research Institute, Dallas, TX 75229, USA. hawkcheryl@aol.com
authors.forename: Cheryl
authors.initials: C
authors.lastname: Hawk
authors.forename: Cynthia R
authors.initials: CR
authors.lastname: Long
authors.forename: Robert M
authors.initials: RM
authors.lastname: Rowell
authors.forename: M Ram
authors.initials: MR
authors.lastname: Gudavalli
authors.forename: James
authors.initials: J
authors.lastname: Jedlicka
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000628:therapy*; D008297:Male; D026882:Manipulation, Chiropractic / Q000379:methods* / Q000592:standards*; D008875:Middle Aged; D015146:Midwestern United States; D010147:Pain Measurement / Q000379:methods; D015990:Placebo Effect; D012720:Severity of Illness Index; D013314:Stress, Mechanical; D016896:Treatment Outcome; D014481:United States; D016474:Weight-Bearing