A new meta-analysis shows little evidence to support the use of invasive interventional procedures for chronic knee and low back pain — although the analysis has several limitations that preclude firm conclusions, researchers say. In 2014, Americans spent an estimated $45 billion on surgery for chronic low back pain and $41 billion for arthroplasty for chronic knee pain

"Opioid use is a problem. We need nonpharmacological approaches to pain; but there is very little research out there that is rigorous on interventional procedures for chronic pain, despite the fact that they are used a lot," lead author Wayne Jonas, MD, from Georgetown University, Washington, DC, and executive director of Samueli Integrative Health Programs, told Medscape Medical News.

"Even more surprising, when we were able to find adequate research to really do a meta-analysis for the two most common pain conditions, low back pain and knee pain, the effects of the placebo made up the vast majority of the effect," said Jonas. The findings were published online September 10 in Pain Medicine.

No Statistical Differences

Quantitative pooling of outcomes for seven studies on chronic low back pain and three on knee pain from osteoarthritis showed no difference in pain at 6 months compared with sham procedures, the investigators report.

The knee procedures, performed in a total of 496 adults, included arthroscopic lavage/debridement, arthroscopic knee irritation, and arthroscopic partial meniscectomy.

The pooled standardized mean difference (SMD) for reduction of knee pain was 0.04 (95% confidence interval [CI], -0.11 to 0.19; P = .63), equating to a 1-point reduction in the 0- to 100-point visual analogue scale (VAS) score. The average improvement was greater in the sham surgery group than in the group that underwent real surgery.

The seven studies of invasive procedures for chronic low back pain included a total of 445 adults. Procedures included percutaneous lumbar facet denervation, percutaneous articular denervation, transcatheter intradiscal electrothermal therapy, percutaneous radiofrequency neurotomy, percutaneous lateral branch neurotomy, and percutaneous vertebroplasty.

The overall pooled SMD for reduction of low back pain was 0.18 (95% CI, -0.14 to 0.51; P = .26), which translates into a 4.5-point reduction in VAS pain score. The proportion of improvement due to sham treatment in low back pain was 73%.

However, the authors note that none of the studies were double-blind, precluding full rigor in the evaluation of these procedures for chronic pain. They also question whether it's even possible to adequately test invasive procedures against sham treatments because blinding of both patients and clinicians is challenging.

Interpret Cautiously

Commenting on the study for Medscape Medical News, Charles Kim, MD, NYU Langone's Rusk Rehabilitation, urged caution in drawing any firm conclusions from this meta-analysis.

"The problem with this type of study is that there is so much subjectivity and selectivity bias on the part of the researchers, so essentially they are cherry-picking the studies. The analogy is like going to the grocery store and picking out all the most rotten fruit and saying since all these fruits are rotten, everything must be rotten. And this particular analysis includes small studies with low statistical power," Kim cautioned.