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.

Study design and setting: 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%).

Conclusion: 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.

Keywords: Meta-analysis; Pain; Placebo; Placebo effect; Randomized; Sham; Sham effect; Sham surgical; Surgery; Systematic review.