This article discusses the available evidence for the
efficacious use of custom-made foot orthoses and is limited to custom-made
products defined as “manufactured from raw materials and molded over a
three-dimensional (volumetric) cast of the foot, which captures bony alignment and
shape”.
Orthotic Efficacy
It is not uncommon for professors, professional
association representatives and clinicians to claim, “foot orthoses are an
effective treatment for low back pain and a variety of other musculoskeletal
and postural complaints.”
In this era of evidence-based medicine, however, where
conscientious care depends upon our ability to make clinical decisions, which
have been confirmed by sound scientific enquiry, practitioners cannot make such
claims about foot orthoses just yet.
Perhaps it is the empirical observation that patients
“respond favorably” to foot orthoses that has slowed the pursuit of hard
evidence for the efficacy of custom-made foot orthoses. Regardless, third party
payors may soon require stronger evidence before letting the current trend of
increasing foot orthotic use continue.
Journals primarily for foot care professionals publish
very few randomized clinical trials (RCTs). A review of the podiatric
literature arbitrarily choosing 1998 and 1993, found that a mere 1% of the
articles were RCTs. Instead of testing hypotheses, the majority of the articles
generated hypotheses. To compound the problem, those articles published in
podiatric journals were of a lesser quality than those published in mainstream
medical journals. A Cochrane database
review (1997 to 2004), concerning the efficacy of foot orthoses, revealed only
6 RCTs. The studies were deemed to be of variable quality according to the
Consolidated Standards of Reporting Trials
(CONSORT-http://www.consort-statement.org/) guidelines with only one rating as
high as a Sackett’s grading of B – provides some support for clinical practice.
The range of research outcomes regarding orthotic
efficacy varies from inconclusive to supportive with one study suggesting that
customs were inferior to off-the-shelf products. A significant concern with research
on custom-made foot orthoses, prior to the last few years, is the absence of
“subject-specific design” in those studies and the lack thereof being a
confounder of results. Without adequate research to provide an evidence-based
platform, professionals vary considerably in what they prescribe and it is
difficult to develop guidelines for orthotic prescriptions.
Four retrospective studies regarding custom-made foot
orthoses, between 1985 and 1993, revealed patient satisfaction ratings between
70% and 91%. A recent questionnaire of 275 patients indicated the majority felt
that custom-made foot orthoses had provided relief of their symptoms to a level
of 60-100%. Criticisms of these studies however, include that they were
retrospective, did not control for other forms of treatment during the course
of orthotic therapy and were unclear in their classification of orthotic
device. Furthermore, it has been documented that “patient satisfaction”
indicates service satisfaction and not necessarily treatment outcome
satisfaction.
The traditional notion that foot orthoses optimally align the skeleton is being
critically challenged by the scientific community as well. Repeated research
efforts show that skeletal movement changes due to foot orthoses are small,
subject-specific and non-systematic.
Not
All the News is Bad…
Replacing the traditional “re-aligning the skeleton” theory, are
several plausible alternatives to explain why custom-made foot orthoses seem to
provide symptomatic relief
of common musculoskeletal (MSK) complaints:
• the biomechanical theory suggests that full contact
orthoses, (whereby there is complete orthotic-medial-arch contact) maximally
control the pronatory moment (also described as assisting midfoot
re-supination) and allow for functional first ray plantarflexion in the overpronating
foot.
• The neuro-muscular theory for using full-contact
custom-made orthoses suggests that the medial and lateral arches of the foot
are the most sensitive regions to changes in pressure and vibration and that enhanced
proprioceptive feedback allows for a movement pattern that minimizes muscle
activities. This accounts for the decrease in symptoms where kinetic changes
are minimal and unsystematic.
There is some research using these alternative
theories, to indicate that full-contact custom-made foot orthoses may decrease
lower limb musculoskeletal symptoms within 4 weeks and that there may be improvements
in efficiency of gait by way of reducing centre of mass oscillation. These
results however are generalizable only to custom-made foot orthoses used in
that study. Another recent investigation using the same full-contact
custom-made foot orthoses compared them to a group wearing traditional
custom-made foot orthoses. The EMED system (a multi-sensor pressure mapping
device) was used to assess changes in plantar pressure in the two groups over a
6-week period. The researchers found that patients wearing the full-contact
orthoses more effectively approximated the ideal force curve, which included
decreased pressure over the lateral metatarsal head with increased pressure
under the 1st metatarsal heads at toe-off.
What
Can We Say?
There is some recent objective and subjective evidence
in support of custom-made foot orthoses for reducing MSK complaints and moving gait
towards more idealized and efficient patterns. There is however, not enough
consistency in the research or volume of peer-reviewed research to claim that
all foot orthoses will resolve the variety of complaints seen in most health
care facilities. The responsibility rests with the individual practitioner to
ensure that the orthotic devices they recommend meet the criteria of
custom-made and that claims of efficacy are restricted to those within the
mandate of evidence-based medicine.
Guidelines
for the Conscientious Practitioner
As new research is published each month, it behooves
clinicians to critically assess the quality of that research before making
statements regarding the efficacy of any treatment. Here are some suggestions:
1. Ensure that the literature claiming orthotic
efficacy is not promotional material distributed by an orthotic manufacturing
company. However, note that some orthotic companies do fund research. If they
do, look for a statement that they funded the study in the context of signing
an “arms-length agreement” which states that both positive and negative results
will be published. This is a risk most orthotics manufacturers are not willing to
take and it is a good litmus test of their product confidence. Ask if
your company has funded “arms-length” research.
2. Ensure that the peer-reviewed literature is not
being misquoted. I recently read a headline within some marketing literature
distributed by an orthotic company. The referenced literature was indeed good
work, however, the “revised” company headline completely misquoted the author’s
conclusions to imply an endorsement of their product.
3. Lastly, and probably most importantly, not all
professional journals are stringently peer-reviewed. Some function, more or
less, as professional trades magazines. Unless the research is published in a
peer-reviewed journal be cautious of quoting any conclusions.
By the way, poster presentations at chiropractic
conferences using underpowered sample sizes and sponsored by orthotic companies
are not consider peer-reviewed (recently a colleague insisted that I must be incorrect
about this). CONSORT provides an excellent 22-point checklist for practitioners
to judge the quality of any research.
(http://www.consort-statement.org/?o=1011)
Good luck, happy practicing and remember;
“Education
is a progressive discovery of our own ignorance.” - Will Durant
Leslie
Trotter, BSc, MBA, CPed(C), MSc
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