title: Sham surgical procedures for pain intervention result in significant improvements in pain: systematic review and meta-analysis.
abstract: OBJECTIVE
  To perform a systematic review and meta-analysis to study the magnitude of the placebo effect associated with sham surgery procedures.
  
  
  METHODS
  We conducted a systematic search for randomized controlled clinical trials comparing any type of surgery to a corresponding sham placebo group and compared improvements in the sham treatment arms in subjective, objective, categorical, and continuous outcomes, as well as complication rates and mortality. Effect sizes were reported as standardized mean differences (SMDs). This is a systematic review and meta-analysis.
  
  
  RESULTS
  The overall effect size for pain improvement after sham surgery was SMD = 0.22 (95% confidence interval [CI] = 0.08-0.35) with improvement most marked at 1 month (SMD = 0.34, 95% CI = 0.26-0.43). There was a higher rate of improvement in subjective outcomes compared to objective outcomes for both dichotomized (number of patients with improvement) (42.8% compared to 27.1%) and continuous outcomes (SMD = 0.12, 95% CI = -0.05, 0.30 vs. SMD = -0.01, 95% CI = -0.05, 0.03). There were no deaths in the sham treatment arms and major complications were very rare (0.2%, 95% CI = 0.0-0.6%).
  
  
  CONCLUSIONS
  Sham surgery is associated with a large improvement in pain and other subjective patient-reported outcomes but with relatively small effect on objective outcomes. Sham surgeries are overwhelmingly safe. The magnitude of this effect should be used when planning future sham-controlled surgery trials.
authors.affiliation: University of Tennessee Health Sciences Center, School of Medicine, 920 Madison Ave, Memphis, TN 38163, USA.
authors.forename: Alice P
authors.initials: AP
authors.lastname: Gu
authors.affiliation: Department of Radiology, Mayo Clinic, 200 1st Street SW, Rochester, MN 55905, USA. Electronic address: gu.chris@mayo.edu.
authors.forename: Chris N
authors.initials: CN
authors.lastname: Gu
authors.affiliation: Center for Science of Healthcare Delivery, Mayo Clinic, 200 1st Street SW, Rochester, MN 55905, USA.
authors.forename: Ahmed T
authors.initials: AT
authors.lastname: Ahmed
authors.affiliation: Center for Science of Healthcare Delivery, Mayo Clinic, 200 1st Street SW, Rochester, MN 55905, USA.
authors.forename: Mohammad H
authors.initials: MH
authors.lastname: Murad
authors.affiliation: Center for Science of Healthcare Delivery, Mayo Clinic, 200 1st Street SW, Rochester, MN 55905, USA.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Radiology, Mayo Clinic, 200 1st Street SW, Rochester, MN 55905, USA; Department of Neurosurgery, Mayo Clinic, 200 1st Street SW, Rochester, MN, USA 55905.
authors.forename: David F
authors.initials: DF
authors.lastname: Kallmes
authors.affiliation: Department of Radiology, Mayo Clinic, 200 1st Street SW, Rochester, MN 55905, USA.
authors.forename: Waleed
authors.initials: W
authors.lastname: Brinjikji
mesh_terms: D006801:Humans; D010146:Pain / Q000175:diagnosis / Q000601:surgery*; D010147:Pain Measurement; D015990:Placebo Effect; D010919:Placebos
chemical_list: D010919:Placebos
keywords: Meta-analysis; Pain; Placebo; Placebo effect; Randomized; Sham; Sham effect; Sham surgical; Surgery; Systematic review