Are invasive procedures effective for chronic pain? A systematic review

Key points

1. 0125 RCTs (2,000 participants) compared invasive procedures directly against identical sham procedures across 7 chronic pain conditions
2. 02For low back pain, the pooled effect over sham was not statistically significant (SMD 0.18, 95% CI -0.14 to 0.51, P=0.26)
3. 03For knee osteoarthritis, the pooled effect over sham was negligible (SMD 0.04, 95% CI -0.11 to 0.19, P=0.63)
4. 04Sham procedures accounted for 87% of the improvement seen with active invasive treatments across all conditions
5. 05Real invasive procedures had a significantly higher adverse event rate (12%) than sham procedures (4%)

How it was conducted

Design

Systematic review with meta-analysis of randomised sham-controlled trials

Databases searched

PubMed, EMBASE, CINAHL, Cochrane Central, PILOTS, PsycInfo, DoD Biomedical Research, ClinicalTrials.gov (through January 2018)

Participants

2,000 patients across 25 RCTs published between 1959 and 2013

Conditions covered

Low back pain (7 trials), knee osteoarthritis (4), angina (4), abdominal pain (3), endometriosis (3), biliary pain (2), migraine (2)

Primary outcome

Reduction in pain intensity (invasive procedure vs. identical sham procedure)

Quality assessment

Cochrane risk of bias tool; overall evidence quality rated by GRADE

What they found

• Pooled SMD for low back pain (7 studies, N=445): 0.18 (95% CI -0.14 to 0.51, P=0.26, I2=62%) - not statistically significant, equating to a 4.5-point reduction on a 0-100 VAS
• Pooled SMD for knee osteoarthritis (3 studies, N=496): 0.04 (95% CI -0.11 to 0.19, P=0.63, I2=36%) - not statistically significant, equating to a 1-point VAS reduction
• Adverse events were significantly more frequent with real invasive procedures (12%) than sham procedures (4%); risk difference 0.05 (95% CI 0.01 to 0.09, P=0.01, I2=65%)
• Sham procedures accounted for 87% of the improvement seen with active treatments across all conditions combined
• For low back pain specifically, sham accounted for 73% of improvement; for knee osteoarthritis, average improvement was actually greater in the sham group than after real surgery
• Study dropout rates did not differ between real and sham groups: risk difference 0.01 (95% CI -0.01 to 0.03, P=0.38, I2=9%)
• Only 13 of 25 trials (52%) had adequate allocation concealment; 21 (84%) had adequate patient and assessor blinding

Limitations

• Very few studies exist for any single pain condition, creating substantial clinical heterogeneity across populations and interventions
• Many types of invasive procedures have never been tested in sham-controlled trials, so findings may not generalise beyond the studied procedures
• No studies were fully double-blind because surgeons always knew which procedure was performed, limiting the rigour of the evaluation
• Sham-controlled trials are ethically contentious and logistically difficult, which restricts the evidence base and may introduce publication bias

Why it matters

For patients

Patients considering surgery or invasive procedures for chronic back or knee pain should know the current evidence does not show these procedures work better than a placebo (sham) operation, and the real procedure carries a higher risk of side effects.

For clinicians

Clinicians should use caution before recommending invasive procedures for chronic pain, particularly for back and knee conditions, as pooled evidence from sham-controlled trials shows no statistically significant benefit beyond placebo, while adverse event rates are higher with real procedures.

For readers

This review highlights that much of the perceived benefit from invasive pain procedures may be driven by placebo and contextual effects rather than the specific physical intervention, underscoring the need for more rigorous sham-controlled trials before widespread adoption.