Evidence Against the Use of Shoe Insoles to Prevent Low Back Pain
Can putting a simple pair of insoles inside your shoes prevent low back pain? What about using them to treat back pain once it starts? After conducting a systematic review of all the evidence, the conclusion was No to prevention and Not enough evidence to say for treatment.
But can we trust the evidence? How do researchers come up with answers like these? In this case, a group of physicians from Israel searched four major electronic databases (Central, Medline, Embase, CINAHL) for any studies, reviews, or guidelines on this topic. The authors reviewing materials worked independently of one another in order to be blinded to the opinions of others. This research technique helps keep the results unbiased.
Some of the databases had information from as far back as 1966. Others started collecting data in the early 1980s. All four data banks were searched up to the present (October 2008). Part of the job of the independent reviewers was to look at how the studies were done and make sure only those with the highest quality were selected for inclusion in this review.
Considering the high cost of care for patients with low back pain (more than $100 billion each year in North America alone), finding something as simple and easy as shoe insoles as a prevention or treatment technique would be very helpful. But of the six randomized controlled trials involving more than 2,000 patients, there just wasn't the evidence needed to support the use of shoe insoles.
The next question was whether or not using custom-made versus off-the-shelf (prefab) insoles made a difference. There were some studies that compared the use of insoles with a placebo (sham inserts with no real effect) and with no treatment.
Any studies with insoles used to correct a leg-length difference were not included. The decision to exclude studies with special insoles to treat limb-length inequality was based on previous research showing a lack of evidence to support limb-length linked to back pain.
Part of a systematic review of evidence involves evaluation of the methods used in research on the topic. The reviewers looked at quality of research design, type of data collected in each study (e.g., patient age, gender, type of insoles used, how long patients were treated, occupation), and outcomes/results measured. Studies combined and analyzed have to be similar in all of these areas to be able to be of any value.
The authors used a well-known method of study review: the Cochrane Handbook. The Cochrane Collaboration is a group of over 15,000 volunteers in more than 90 countries. The group reviews the effects of health care interventions (treatment) tested in biomedical randomized controlled trials. The results of these systematic reviews are published as Cochrane Reviews in the Cochrane Library. Health care professionals rely on Cochrane Reviews as valid and accurate summaries on many topic of interest.
The results of this systematic review may have found a lack of evidence to support the use of insoles as a treatment for low back pain but that's not the end of the discussion. That lack of evidence was related to poor research design in some of the studies already done. Without clear criteria for the selection of patients included in studies, proper analysis of data, and the collection of complete data, the evidence can be presented as favorable when, in fact, the evidence is really limited. That was the case in studies reviewed using insoles for the treatment (vs. prevention) of low back pain.
Where does that leave us on the issue of shoe insoles for the prevention or treatment of low back pain? That's a good question. Right now, there are so many different kinds of insoles on the market, it's difficult to know if perhaps a specific insole might be the answer. Some are customized, others are not.
Most of the large studies were done on military (male) soldiers. We don't really have much information on women or older adults regarding this issue. And some of the studies reported a shift of pain from the back to the legs. So, in today's modern lingo, it might be appropriate to ask, What's up with that?
The authors concluded that there is strong evidence that insoles don't prevent back pain. More trials are needed to come to any conclusions about the use of insoles to treat back pain. And, the book is wide open on whether or not there's one single insole that's the best or if certain insoles work better for some problems than others.
Tali Sahar, MD, et al. Insoles for Prevention and Treatment of Back Pain. In Spine. April 20, 2009. Vol. 34. No. 9. Pp. 924-933.