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Foot orthotics for low back pain: The state of our understanding and recommendations for future research
Accepted Manuscript Title: Foot orthotics for low back pain: The state of our understanding and recommendations for future research Author: Mark Owen Papuga Jerrilyn Cambron PII: DOI: Reference:
S0958-2592(15)00116-9 http://dx.doi.org/doi:10.1016/j.foot.2015.12.002 YFOOT 1418
To appear in:
The Foot
Received date: Revised date: Accepted date:
3-4-2015 9-12-2015 14-12-2015
Please cite this article as: Papuga MO, Cambron J, Foot orthotics for low back pain: The state of our understanding and recommendations for future research, The Foot (2015), http://dx.doi.org/10.1016/j.foot.2015.12.002 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
TITLE PAGE
Word count for structured abstract (approx 250 words or less)
199
Word count for text (excludes abstract, figure legends, references)
3546
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Key Words – only use MeSH terms that are found at http://www.nlm.nih.gov/mesh/meshhome.html
Fill in information in each box below Foot orthotics for low back pain: The state of our understanding and recommendations for future research Foot Orthoses; Foot Arch Supports; Foot Orthosis; Foot Orthotic Devices; Orthotic Insoles; Back Pain; Low Back Pain
ARTICLE INFORMATION Article Title
CORRESPONDING AUTHOR CONTACT INFORMATION
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Fill in information in each box below Mark, Owen, Papuga [email protected] 2360 State Route 89 Seneca Falls, NY 13148 315-568-3858 315-568-3204
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For the corresponding author (responsible for correspondence, proofreading, and reprints) First name, middle initial, last name and degrees Email address – this is where your proofs will be sent Postal mailing address – this is where your complimentary copy will be shipped Phone number Fax number
Mark, Owen, Papuga. PhD
Assistant Professor, New York Chiropractic College Research Department, New York Chiropractic College
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First author First name, middle initial, last name of author. Include highest academic degree(s). Title, academic or professional position (eg, Professor, University of Illinois) Name of department(s) and institution(s) to which work should be attributed for this author (eg, Kinesiology Department)
Jerrilyn, Cambron. DC, PhD Professor, National University of Health Sciences Department of Research, National University of Health Sciences
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Second author First name, middle initial, last name of author. Include highest academic degree(s). Title, academic or professional position (eg, Professor, University of Illinois) Name of department(s) and institution(s) to which work should be attributed for this author (eg, Kinesiology Department)
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Foot orthotics for low back pain: The state of our understanding
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and recommendations for future research
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ABSTRACT: Purpose: The purpose of the article is to summarize the literature on the use of foot orthotics for
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low back pain and to make specific recommendations for future research. Methods: Database searches were conducted using PubMed, EBSCO, GALE, Google Scholar,
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and clinicaltrials.gov. The biomedical literature was reviewed to determine the current state of
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knowledge on the benefits of foot orthotics for low back pain related to biomechanical mechanisms and clinical outcomes.
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Results: It may be argued that foot orthotics are experimental, investigational, or unproven for low back pain due to lack of sufficient evidence for their clinical effectiveness. This conclusion
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is based upon lack of high quality randomized controlled trials (RCTs). However, there is extensive research on biomechanical mechanisms underlying the benefits of orthotics that may
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be used to address this gap. Additionally, promising pilot studies are beginning to emerge in the
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back pain.
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literature and ongoing large-scale RCTs are addressing effects of foot orthotics on chronic low
Conclusions: Based upon the critical evaluation of the current research on foot orthotics related to biomechanical mechanisms and clinical outcomes, recommendations for future research to address the evidence-practice gaps on the use of foot orthotics for low back pain are presented.
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INTRODUCTION: There is wide spread clinical use of foot orthotics in the developed nations to treat a variety of
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musculoskeletal conditions. Surveys indicate both chiropractors and podiatrists have high rates of utilization[1-3] and patients report high levels of compliance and satisfaction.[4] Industry
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analysts have estimated the world-wide market for orthotic devices to be 4.7 billion USD for
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2015.[5] Previous recommendations regarding the use of orthotic intervention as a treatment for those with low back pain (LBP) are varied. The United States Veterans Administration
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recommends the use of orthotics for treatment of those with work related LBP,[6] yet the European Guidelines for the Management of Chronic Non-Specific Low Back Pain does not
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mention foot orthotics.[7]
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The purpose of this article is to highlight the current state of knowledge regarding the clinical use
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of foot orthotics to treat and/or prevent the occurrence of LBP, and to review the biomechanical
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mechanisms underlying the effectiveness of such treatment. We also have identified gaps in the literature that exist based on the findings of studies on foot orthotics. Here we provide a summary of the most influential studies conducted during the past decade and make recommendations that may prove useful in directing future clinical research initiatives involving foot orthotics for back pain.
METHODS: The biomedical literature was searched to identify key articles that reveal the current state of knowledge on the benefits of foot orthotics for LBP related to biomechanical mechanisms and clinical outcomes. Database searches were conducted using PubMed, EBSCO , GALE, Google Scholar, and clinicaltrials.gov. The following search terms were used for each database (“foot Page 4 of 21
orthotics”, insoles, “foot orthoses”, “shoe inserts”, excluding “foot ankle”). In addition, reference lists from key articles were searched for relevant literature. Articles for use in this review were identified based on the level of evidence[8] as well as clinical relevance to orthotic use in
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treating LBP. Preference was given to recent meta-analyses and randomized controlled trials in
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the area of interest, where available.
Biomechanical mechanisms of foot orthotics for LBP:
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RESULTS:
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The high impact forces and repetitive stress associated with heel strike during gait has been implicated as a contributing factor in the development of both lower limb pain and LBP.[9] The
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added shock absorption properties of orthotics have been proposed as a significant source of pain relief. An early study of viscoelastic insoles showed a decrease of 42% in the peak vertical
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impact forces at heel strike.[10] Subsequent studies found strikingly positive effects of shock
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absorbing insoles alone to treat LBP with approximately 80% of subjects reporting significant
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improvement in both pain and mobility after one year of use. Forty five percent of patients from this study whom discontinued the intervention were found to have significant improvement in pain and mobility with conservative care alone, illustrating the wide variability experienced by those treated for LBP.[9]
Impaired or abnormal foot function has been implicated as a possible mechanism that may contribute to the development of LBP. Excessive pronation of the foot during gait has been proposed to induce prolonged and/or excessive internal rotation of the lower limb resulting in abnormal forward progression.[11] This hampered progression can result in a significant increase in strain at both the sacroiliac and lumbosacral joints. [11-13] These increased strains theoretically lead to increased pain and muscular dysfunction. Page 5 of 21
Ball and Afheldt 2002 highlighted the differences between rigid orthotics based on “Root theory” foot classification, where the focus of intervention is to maintain subtalar neutral position
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and semi-rigid orthotics with the intention of “supporting” the three arches of the foot.[14] This review, relying on several studies of biomechanical analysis of normal subjects,[15,16] cast
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some doubt on the utility of the Root approach. Three areas of criticisms were described: the
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poor reliability of clinical identification of subtalar neutral position, the unrealistic representation of non-weight bearing identification subtalar neutral position, and the lack of demonstrated
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functional significance of this position during normal gait.[14]
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The effect that static standing foot posture has on the incidence of injury or pathology has been a topic of much debate.[9,17-20] Predisposition to injury based on static arch height during
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standing has been proposed with several studies finding that those individuals with high arches
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had a higher incidence of lower limb pathology when compared to low arched
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individuals.[9,21,22] Natural shock absorption of the foot was addressed through biomechanical testing, those with higher arches were found to have more internal rotation of the tibia at heel strike and absorb shock earlier in stance phase.[23,24] Theoretically, this increases the capacity for shock absorption and should lead to a protective effect.
A recent study by Menz et al 2013 found that increased dynamic foot pronation, as measured with center of pressure excursion, was significantly associated with LBP in women, while the static posture of the foot was not. However, no such association was found in the male subjects. The implications of this finding are limited, as the back pain was only indicated on a body chart and not described in severity, duration, or frequency.[17]
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A recent review by Kendal et al 2014 summarizes the current understanding of dynamic aspects of functional foot kinematics associated with lumbopelvic muscular dysfunction.[25] The authors point to recent findings of increased navicular drop associated with LBP,[26] and
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decreased shock absorption found in those with a pronated static foot posture as evidence for the relationship.[23] The review however goes on to conclude that the changes in foot posture are
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associated with relatively small magnitude changes in pelvic posture, have little evidence of
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clinical significance.[25] The relationship between lumbopelvic muscular dysfunction and altered foot mechanics is puzzling. There is evidence of association between the two,[18,27] also
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there is evidence that each is associated with LBP.[28-30] In a review of both foot and lumbopelvic-hip motion Barwick et al 2012 summarizes nicely several key elements of the
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proposed mechanisms of orthotic intervention: affecting foot pronation,[31-33] internal tibial rotation,[32,34,35] joint moments,[32,36,37] muscular activation,[38-40] neuromuscular
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control,[41,42] and sensory feedback.[32,41,43,44] The authors concluded that evidence of
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coupling of the foot and lumbopelvic-hip complex suggests that the use of foot orthotics may
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have an effect on more proximal structures. [45]
Contradictory evidence is reported in the description of the kinematic effects of orthotic intervention, where multi-segment biomechanical models of the foot are able to give a more complete indication of the kinematic effects of orthotic introduction. Sinclair et al 2014 found that the introduction of custom orthotics acted to reduce motion in the coronal and transverse plane during running[46] opposing earlier work in this area that found no such reductions. [47,48] The authors hypothesize that the composition of the medial arch support may explain the discrepancy.[46] This area of research is rife with inconsistent results stemming from the comparison of studies describing custom interventions. The proprietary nature of many orthotic
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interventions hinders the ability of researchers to directly compare specific mechanisms of action, and has been identified as a barrier to research. [49]
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Small and widely disparate kinematic and kinetic changes have been documented with the use of foot orthotics; to date the clinical implications of these changes are unclear. The direct link from
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documented prolonged kinematic or kinetic changes to clinical efficacy has not been made.
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Clinical studies lack the rigorous biomechanical analysis needed while detailed biomechanical studies do not provide a longitudinal view of intervention and generally lack clinically relevant
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outcome measures. A truly translational approach is needed to address the evidence gaps that are
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currently present in this area of research.
Recommendations for studies on biomechanical mechanisms:
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There is a clear need for the dynamic biomechanical characterization of foot function prior to an
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intervention. The static characterization of foot posture falls short of giving a clear indication of
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foot dysfunction during gait. Interventions based on a clearly defined set of kinematic and/or kinetic variables would produce improved specificity of treatment effects. However, this approach is thwarted by the need for clinically available equipment, processes, and protocols by which to produce such a characterization.
Future research in the area of biomechanical consequences of foot orthotic intervention should focus on the systematic alteration of foot kinematics and/or kinetics during the stance phase of gait. These systematic changes should then be correlated to patient outcomes. It has been shown that the use of custom orthotics can have a variety of effects on both the kinematics and kinetics of the foot during the stance phase of gait. Placebo/Sham controlled trials should be developed to isolate specific kinematic or kinetic changes and relate those specific isolated changes to Page 8 of 21
outcomes of pain and/or function. With the wide availability of 3D scanning and printing technologies the possibilities for innovation are no longer hampered by the high costs and time consuming processes of casting/fitting and precision manufacturing. This technology advance
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might be most useful in the development of orthotic conditions that control specific kinematic or kinetic features of the foot during the stance phase of gait. This should help to highlight what
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biomechanical aspects of orthotic intervention are most important in the reduction of pain.
Additionally, future research should investigate the hypothesis of an individualized preferred
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movement pattern[33], where patient feedback combined with biomechanical principles drives the customization of the orthotic intervention. Again, with the growing availability and cost
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savings of 3D printing, an intervention may be modified based on feedback or can be
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systematically modified throughout a treatment plan to facilitate biological adaptation.
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Meta-analyses and RCTs on foot orthotics for the prevention of back pain
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Two meta-analyses of foot orthotic intervention used both in the treatment and prevention of LBP have been published.[50,51] When regarding the use of orthotics in for the prevention of LBP the Chuter et al 2014 meta-analysis revealed a 22% reduction in the risk of developing LBP with the use of orthotics compared to the control group, however this seemingly large decreased risk was not statistically significant.[50] Similarly, Sahar et al 2009 found no significant change in the pooled Risk Ratio associated with the use of foot orthotics versus sham or no intervention from three studies (Milgrom, Larsen, Schwellnus) including 2061 subjects.[51] Chutter et al 2014 go on to address the weak generalizability of this analysis based on the demographics and specific settings of the subject population, as all of the subjects included in their meta-analysis were male military recruits under 20 years of age. The external validity of such trials was also questioned as this age group would not be at great risk for developing LBP in the general Page 9 of 21
population (Chutter et al 2014).[50] One study[52] found that there was no statistical difference in the incidence of back pain among recruits provided with two different types of orthotic when compared to those provided with a simple shoe inserts. These findings are complicated by a high
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drop-out rate where only 67.5%, 45.5%, and 48.6% of subjects completed 14 weeks of training in the soft-custom, semi-rigid, or simple shoe insert groups respectively. The authors concluded
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that, neither the intention-to-treat analysis of all subjects given orthotics nor analysis of those
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completing training revealed significant differences in the incidence of LBP; therefore, prophylactic use of orthotics is not supported.[52] Mattila et al 2011 in a study of 228 military
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conscripts found no significant difference in risk of LBP requiring a physician visit between those given a custom orthotic vs no treatment over 6 months of military service.[53] They found
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that 33% of those given orthotics had at least one incidence of LBP compared to 27% of control subjects, a difference of 4.3% was found and an 80% compliance rate was reported for those in
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the orthotic group. The authors drew narrow conclusions based on the demographics of the
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subject population stating that “…we recommend that orthotic insoles not be used with an aim
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toward preventing LBP episodes in young male adults”.
The results of the meta-analysis itself due to the low number of high-quality studies was unable to provide conclusive evidence for or against the use of foot orthotics for the prevention of LBP. There was a recommendation for increased research in this area overall and for a focus on specific inclusion criteria that might provide homogeneous populations and identification of traits in those LBP patients that are most likely to benefit from foot orthotic intervention. Another limitation of the studies included in this analysis is the short time scales over which the effectiveness of intervention is assessed with an average intervention of 6.7 weeks with a range between 4 and 12 weeks.
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While the there is wide-spread agreement that there is lack of evidence for foot orthotic use in the prevention of LBP, the supporting literature cited is almost exclusively based on military recruits. This population allows for control of independent variables, such as equipment and
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activity level that would otherwise be difficult to achieve, providing excellent information. However, prospective RCTs that use a military setting may not reflect how these devices
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perform in the general population. As these studies were conducted in the context of military
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training, the limited age range and a dramatic increase in physical demands placed on the subjects may have had great implications as to the prophylactic effectiveness of the orthotic
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intervention.
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Recommendations for future studies on foot orthotics for the prevention of back pain: There are very few well-constructed prospective studies dealing with the ability of foot orthotics
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to prevent LBP. The RCTs that do exist are military based and are not widely generalizable to
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the public at large as they were done under conditions the average person is not likely to be
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exposed and in populations that are not likely to incur LBP if not for those conditions. There is therefore a need to identify means by which to enroll a large number of young to middle-aged subjects from the general public into a long-term prevention study. There are several challenges with this type of approach, including the high associated costs of a lengthy trial period, accurate dynamic characterization of foot function, reliable documentation of orthotic use, and reliable and systematic means of reporting incidence and duration of LBP.
Meta-analyses and RCTs on foot orthotics for the treatment of back pain Chutter et al 2014 assessed studies on the treatment of LBP (5 studies) and found a positive outcome trend in those using orthotics vs. those in a control group.[50] However, not all studies included in the analysis found statistically significant improvements, and the clinical significance Page 11 of 21
of these this trend was not addressed. It was noted that the most significant treatment effect was found in a study that limited the subject population to those with a pronated standing foot posture.[19] It was proposed that this finding may be due to a more homogeneous population
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only including subjects with LBP due to a similar etiology of LBP.[50] The implication is that impaired foot function may play a role in the development of LBP as discussed above. Other
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studies included in the meta-analysis concluded that there was significant evidence that the
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introduction of foot orthotics for those individuals with current LBP was beneficial. Almeida et al 2009 found that both custom and prefabricated insoles resulted in statistically significant
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reduction in back pain found in female workers performing mostly static standing duties.[54] However, this study lacked an adequate control group (“sham” or “no treatment”) for proper
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comparison. Shabat et al 2005 also looked at a working population (long-distance walking) using the MILLION questionnaire and found that patients reported a greater reduction (5.46 to 3.96 out
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of 10) in LBP when using true foot orthotics compared to 5.46 to 5.11 out of 10 with a placebo
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insole.[55] In the original study this reduction was found to be both statistically (p < 0.0001) and
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clinically significant (30% reduction in pain). The authors issued a strongly worded conclusion stating “In conclusion, it was proven that insoles causes improvement of LBP for subjects with repetitive loading such as walking long distances everyday”. However, Sahar et al 2009 in their systematic review using a different set of criteria did not find clinical significance in these results, and go on to point out several flaws in the study including unclear inclusion criteria, inappropriate randomization, missing data, and incomplete analysis.[51] Cambron et al 2011 focused on the feasibility of collecting LBP and disability data in patients with LBP treated with foot orthotics and those “wait-listed” for 6 weeks.[56] A significant reduction in both LBP and disability was found in the treatment group when compared to those in the wait-listed group at the 6-week time point, no further decrease in LBP or disability was found after 12 weeks of intervention. As this was designed as a feasibility study with a limited number of subjects in each Page 12 of 21
group the conclusions drawn by the authors were limited to the confirmed feasibility of such a study and the need for a larger study of similar design to confirm the initially positive
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results.[56]
It is generally accepted that the highest level of evidence for scientific discovery is the result of
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meta-analysis of aggregate data from high quality RCTs. In the absence of sufficiently
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homogeneous high quality studies to conduct such meta-analysis we must not discount the general trends of agreement of the high quality RCTs published in the past decade. Of those
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reviewed here, an overwhelming majority of the studies point toward effectiveness of foot orthotic intervention as having an ability to decrease LBP. While analysis of aggregate data was
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not possible due to the heterogeneity of the studies, the positive findings for the use of orthotics in each of the studies may point to a robust response independent of inclusion criteria or outcome
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measure.
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Two randomized control studies that are currently enrolling patients will hopefully add to the understanding of treatment effects of orthotic intervention. Dougherty et al[57] are collecting data in veteran population with LBP to assess the effect of orthotic treatment alone compared to that of a sham insole. The outcomes used will be visual analog scale (VAS) rating of back pain along with the modified Oswestry Disability Index (mODI) and the Patient Reported Measurement Information system (PROMIS) physical function assessment. The use of a sham control, multiple time points over a 24 week intervention, and clinically relevant outcome measures are key elements. Cambron et al.,[58] building on their previous pilot study, are currently collecting data in a chronic LBP population to assess the effect of orthotic treatment alone compared to that of orthotic intervention plus chiropractic care or no treatment (wait-list group). The outcomes used will be numeric pain scale rating of back pain along with the Page 13 of 21
Oswestry Disability Index (ODI). The use of a wait-list group, multiple time points over a 12 month intervention, and clinically relevant outcome measures are key elements.
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Recommendations for future RCTs on use of foot orthotic for the treatment of back pain: To ensure homogeneity in RCT studies and increase comparability in future work three key
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aspects have been identified: (1) the classification of LBP, (2) the treatment group(s) and control
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group(s), and (3) the intervention duration and outcome measures used. A more rigorous approach needs to be taken to the classification and sub-classification of LBP prior to enrollment
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in a RCT. The varied and mostly unknown etiologies of generalized LBP do not allow for definitive diagnosis and precise biomedical classification. There are many proposed clinical
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means by which to classify patients with LBP.[59] It has been proposed that comprehensive biopsychosocial approaches be used in order to delineate treatment paradigms.[59] The
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biopsychosocial sub-classification of patients enrolled into future RCTs would act to identify
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those characteristics likely to impact the effectiveness of the intervention. Future RCTs should
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make use of multiple control groups that include a well-defined sham and/or no treatment (waitlist), as well as multiple treatment groups that include “real world” adjunctive use. Both the proprietary nature of the orthotics industry and the customization of orthotics themselves lead to a heterogeneity of intervention between studies. The use of a “black box” model where the biomechanical mechanisms of the intervention are unknown is problematic if a mechanistic understanding of the intervention is the goal. However, if the goal is to demonstrate clinical effectiveness, the customized intervention should make use of patient feedback much in line with Nigg et al 2001 and the hypothesis of an individualized preferred movement pattern,[33] where a systematic approach to customization is documented. In addition accurate quantification of customization would allow for correlation to the aforementioned biopsychosocial (including biomechanical) classification of patients, helping to identify which aspects are crucial for Page 14 of 21
orthotic design. The use of validated outcome measures that include pain, physical function/disability, and psychosocial aspects of LBP should be collected during both early
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(weeks to months) and long term (years) time points during the intervention period.
Conclusions: Based upon the critical evaluation of the current research on foot orthotics related
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to biomechanical mechanisms and clinical outcomes, recommendations for future research to
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address the evidence-practice gaps on the benefits of foot orthotics for LBP include: 1) Mechanistic studies focused on clinical outcomes and that make use of dynamic
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characterization of foot function at baseline.
2) Controlled and systematic alteration of orthotic interventions based on this characterization.
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3) Utilization of patient feedback in the customization processes.
4) Prevention studies focused on well-defined subject populations most likely to benefit from
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prophylactic orthotic intervention.
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5) Treatment studies focused on biopsychosocial classification of LBP prior to orthotic
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intervention with sufficient treatment and control groups, examined over longer periods and utilizing validated clinical outcome measures.
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[22] D. N. Cowan, B. H. Jones, and J. R. Robinson, Foot morphologic characteristics and risk of exercise-related injury, Arch Fam. Med, 2 (1993) 773-777. [23] M. Ogon, A. R. Aleksiev, M. H. Pope, C. Wimmer, and C. L. Saltzman, Does arch height affect impact loading at the lower back level in running?, Foot Ankle Int, 20 (1999) 263266. [24] B. M. Nigg, G. K. Cole, and W. Nachbauer, Effects of arch height of the foot on angular motion of the lower extremities in running, J Biomech, 26 (1993) 909-916. [25] J. C. Kendall, A. R. Bird, and M. F. Azari, Foot posture, leg length discrepancy and low back pain--their relationship and clinical management using foot orthoses--an overview, Foot, 24 (2014) 75-80. [26] J. W. Brantingham, G. J. Lee, J. Shaik, and G. Globe, Sagittal plane blockage of the foot, ankle and hallux and foot alignment-prevalence and association with low back pain, J Chiropr. Med, 5 (2006) 123-127. [27] T. R. Souza, R. Z. Pinto, R. G. Trede, R. N. Kirkwood, A. E. Pertence, and S. T. Fonseca, Late rearfoot eversion and lower-limb internal rotation caused by changes in the
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interaction between forefoot and support surface, J Am Podiatr. Med Assoc, 99 (2009) 503-511. [28] M. Kankaanpaa, S. Taimela, D. Laaksonen, O. Hanninen, and O. Airaksinen, Back and hip extensor fatigability in chronic low back pain patients and controls, Arch Phys Med Rehabil, 79 (1998) 412-417.
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[29] S. F. Nadler, G. A. Malanga, J. H. Feinberg, M. Prybicien, T. P. Stitik, and M. DePrince, Relationship between hip muscle imbalance and occurrence of low back pain in collegiate athletes: a prospective study, Am J Phys Med Rehabil, 80 (2001) 572-577.
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[30] E. Nelson-Wong, D. E. Gregory, D. A. Winter, and J. P. Callaghan, Gluteus medius muscle activation patterns as a predictor of low back pain during standing, Clin Biomech, 23 (2008) 545-553. [31] N. Collins, L. Bisset, T. McPoil, and B. Vicenzino, Foot orthoses in lower limb overuse conditions: a systematic review and meta-analysis, Foot Ankle Int., 28 (2007) 396-412.
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[32] A. Mundermann, B. M. Nigg, R. N. Humble, and D. J. Stefanyshyn, Orthotic comfort is related to kinematics, kinetics, and EMG in recreational runners, Med. Sci. Sports Exerc., 35 (2003) 1710-1719. [33] B. M. Nigg, The role of impact forces and foot pronation: a new paradigm, Clin J Sport Med., 11 (2001) 2-9.
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[34] A. Mundermann, B. M. Nigg, R. N. Humble, and D. J. Stefanyshyn, Foot orthotics affect lower extremity kinematics and kinetics during running, Clin Biomech, 18 (2003) 254262.
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[35] K. Mills, P. Blanch, A. R. Chapman, T. G. McPoil, and B. Vicenzino, Foot orthoses and gait: a systematic review and meta-analysis of literature pertaining to potential mechanisms, Br. J Sports Med., 44 (2010) 1035-1046. [36] B. M. Nigg, P. Stergiou, G. Cole, D. Stefanyshyn, A. Mundermann, and N. Humble, Effect of shoe inserts on kinematics, center of pressure, and leg joint moments during running, Med. Sci. Sports Exerc., 35 (2003) 314-319. [37] C. L. Maclean, I. S. Davis, and J. Hamill, Short- and long-term influences of a custom foot orthotic intervention on lower extremity dynamics, Clin J Sport Med, 18 (2008) 338343. [38] A. Mundermann, J. M. Wakeling, B. M. Nigg, R. N. Humble, and D. J. Stefanyshyn, Foot orthoses affect frequency components of muscle activity in the lower extremity, Gait. Posture., 23 (2006) 295-302. [39] G. S. Murley, K. B. Landorf, and H. B. Menz, Do foot orthoses change lower limb muscle activity in flat-arched feet towards a pattern observed in normal-arched feet?, Clin Biomech, 25 (2010) 728-736.
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[40] G. S. Murley, K. B. Landorf, H. B. Menz, and A. R. Bird, Effect of foot posture, foot orthoses and footwear on lower limb muscle activity during walking and running: a systematic review, Gait Posture, 29 (2009) 172-187.
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[41] K. Mills, P. Blanch, and B. Vicenzino, Comfort and midfoot mobility rather than orthosis hardness or contouring influence their immediate effects on lower limb function in patients with anterior knee pain, Clin Biomech, 27 (2012) 202-208. [42] C. J. Nester, M. L. van der Linden, and P. Bowker, Effect of foot orthoses on the kinematics and kinetics of normal walking gait, Gait Posture, 17 (2003) 180-187.
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[43] A. Mundermann, B. M. Nigg, D. J. Stefanyshyn, and R. N. Humble, Development of a reliable method to assess footwear comfort during running, Gait. Posture., 16 (2002) 3845.
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[44] S. Payehdar, H. Saeedi, A. Ahmadi, M. Kamali, M. Mohammadi, and V. Abdollah, Comparing the immediate effects of UCBL and modified foot orthoses on postural sway in people with flexible flatfoot, Prosthet. Orthot. Int, [ePub ahead of print] (2014).
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[45] A. Barwick, J. Smith, and V. Chuter, The relationship between foot motion and lumbopelvic-hip function: a review of the literature, Foot, 22 (2012) 224-231.
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[46] J. Sinclair, J. Isherwood, and P. J. Taylor, The Effects of Orthotic Intervention on MultiSegment Foot Kinematics and Plantar Fascia Strain in Recreational Runners, J Appl Biomech, 31 (2015) 28-34.
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[47] S. C. Cobb, L. L. Tis, J. T. Johnson, Y. T. Wang, and M. D. Geil, Custom-molded footorthosis intervention and multisegment medial foot kinematics during walking, J Athl. Train., 46 (2011) 358-365.
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[48] R. Ferber and B. Benson, Changes in multi-segment foot biomechanics with a heatmouldable semi-custom foot orthotic device, J Foot Ankle Res, 4 (2011) 18. [49] K. A. Ball and M. J. Afheldt, Evolution of foot orthotics--part 2: research reshapes longstanding theory, J Manipulative Physiol Ther, 25 (2002) 125-134. [50] V. Chuter, M. Spink, A. Searle, and A. Ho, The effectiveness of shoe insoles for the prevention and treatment of low back pain: a systematic review and meta-analysis of randomised controlled trials, BMC Musculoskelet Disord., 15 (2014) 140. [51] T. Sahar, M. J. Cohen, V. Uval-Ne'eman, L. Kandel, D. O. Odebiyi, I. Lev, M. Brezis, and A. Lahad, Insoles for prevention and treatment of back pain: a systematic review within the framework of the Cochrane Collaboration Back Review Group, Spine (Phila Pa 1976. ), 34 (2009) 924-933. [52] C. Milgrom, A. Finestone, O. Lubovsky, D. Zin, and A. Lahad, A controlled randomized study of the effect of training with orthoses on the incidence of weight bearing induced back pain among infantry recruits, Spine (Phila Pa 1976. ), 30 (2005) 272-275.
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[53] V. M. Mattila, P. Sillanpaa, T. Salo, H. J. Laine, H. Maenpaa, and H. Pihlajamaki, Orthotic insoles do not prevent physical stress-induced low back pain, Eur. Spine J, 20 (2011) 100-104.
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[54] Almeida J, Carvalho Filho G, Pastre C, Padovani C, and Martins R, Comparison of plantar pressure and musculoskeletal symptoms with the use of custom and prefabricated insoles in the work environment, Revista Brasileira de Fisioterapia, 13 (2009) 542-548.
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[55] S. Shabat, T. Gefen, M. Nyska, Y. Folman, and R. Gepstein, The effect of insoles on the incidence and severity of low back pain among workers whose job involves long-distance walking, Eur. Spine J, 14 (2005) 546-550.
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[56] J. A. Cambron, M. Duarte, J. Dexheimer, and T. Solecki, Shoe orthotics for the treatment of chronic low back pain: a randomized controlled pilot study, J Manipulative Physiol Ther, 34 (2011) 254-260.
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[57] Dougherty P. Efficacy of Foot Orthotics in Veterans with Chronic Low Back Pain. www.clincaltrials.gov NCT01865539. 2-12-2015. Ref Type: Online Source
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[58] Cambron J. Orthotic Use for Low Back Pain. www.clinicaltrials.gov NCT02089750. 212-2015. Ref Type: Online Source
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[59] E. V. Billis, C. J. McCarthy, and J. A. Oldham, Subclassification of low back pain: a cross-country comparison, Eur. Spine J, 16 (2007) 865-879.
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A review the biomechanical mechanisms underlying the effectiveness of foot orthotic treatment. A review of the current state of knowledge regarding the clinical use of foot orthotics to treat and/or prevent the occurrence of Low Back Pain. A discussion of the most influential studies in the area of foot orthotic conducted during the past decade. Recommendations based on our review that may prove useful in directing future clinical research are provided.
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S0958-2592(15)00116-9 http://dx.doi.org/doi:10.1016/j.foot.2015.12.002 YFOOT 1418
To appear in:
The Foot
Received date: Revised date: Accepted date:
3-4-2015 9-12-2015 14-12-2015
Please cite this article as: Papuga MO, Cambron J, Foot orthotics for low back pain: The state of our understanding and recommendations for future research, The Foot (2015), http://dx.doi.org/10.1016/j.foot.2015.12.002 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
TITLE PAGE
Word count for structured abstract (approx 250 words or less)
199
Word count for text (excludes abstract, figure legends, references)
3546
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Key Words – only use MeSH terms that are found at http://www.nlm.nih.gov/mesh/meshhome.html
Fill in information in each box below Foot orthotics for low back pain: The state of our understanding and recommendations for future research Foot Orthoses; Foot Arch Supports; Foot Orthosis; Foot Orthotic Devices; Orthotic Insoles; Back Pain; Low Back Pain
ARTICLE INFORMATION Article Title
CORRESPONDING AUTHOR CONTACT INFORMATION
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Fill in information in each box below Mark, Owen, Papuga [email protected] 2360 State Route 89 Seneca Falls, NY 13148 315-568-3858 315-568-3204
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For the corresponding author (responsible for correspondence, proofreading, and reprints) First name, middle initial, last name and degrees Email address – this is where your proofs will be sent Postal mailing address – this is where your complimentary copy will be shipped Phone number Fax number
Mark, Owen, Papuga. PhD
Assistant Professor, New York Chiropractic College Research Department, New York Chiropractic College
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First author First name, middle initial, last name of author. Include highest academic degree(s). Title, academic or professional position (eg, Professor, University of Illinois) Name of department(s) and institution(s) to which work should be attributed for this author (eg, Kinesiology Department)
Jerrilyn, Cambron. DC, PhD Professor, National University of Health Sciences Department of Research, National University of Health Sciences
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Second author First name, middle initial, last name of author. Include highest academic degree(s). Title, academic or professional position (eg, Professor, University of Illinois) Name of department(s) and institution(s) to which work should be attributed for this author (eg, Kinesiology Department)
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Foot orthotics for low back pain: The state of our understanding
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and recommendations for future research
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ABSTRACT: Purpose: The purpose of the article is to summarize the literature on the use of foot orthotics for
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low back pain and to make specific recommendations for future research. Methods: Database searches were conducted using PubMed, EBSCO, GALE, Google Scholar,
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and clinicaltrials.gov. The biomedical literature was reviewed to determine the current state of
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knowledge on the benefits of foot orthotics for low back pain related to biomechanical mechanisms and clinical outcomes.
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Results: It may be argued that foot orthotics are experimental, investigational, or unproven for low back pain due to lack of sufficient evidence for their clinical effectiveness. This conclusion
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is based upon lack of high quality randomized controlled trials (RCTs). However, there is extensive research on biomechanical mechanisms underlying the benefits of orthotics that may
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be used to address this gap. Additionally, promising pilot studies are beginning to emerge in the
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back pain.
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literature and ongoing large-scale RCTs are addressing effects of foot orthotics on chronic low
Conclusions: Based upon the critical evaluation of the current research on foot orthotics related to biomechanical mechanisms and clinical outcomes, recommendations for future research to address the evidence-practice gaps on the use of foot orthotics for low back pain are presented.
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INTRODUCTION: There is wide spread clinical use of foot orthotics in the developed nations to treat a variety of
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musculoskeletal conditions. Surveys indicate both chiropractors and podiatrists have high rates of utilization[1-3] and patients report high levels of compliance and satisfaction.[4] Industry
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analysts have estimated the world-wide market for orthotic devices to be 4.7 billion USD for
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2015.[5] Previous recommendations regarding the use of orthotic intervention as a treatment for those with low back pain (LBP) are varied. The United States Veterans Administration
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recommends the use of orthotics for treatment of those with work related LBP,[6] yet the European Guidelines for the Management of Chronic Non-Specific Low Back Pain does not
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mention foot orthotics.[7]
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The purpose of this article is to highlight the current state of knowledge regarding the clinical use
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of foot orthotics to treat and/or prevent the occurrence of LBP, and to review the biomechanical
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mechanisms underlying the effectiveness of such treatment. We also have identified gaps in the literature that exist based on the findings of studies on foot orthotics. Here we provide a summary of the most influential studies conducted during the past decade and make recommendations that may prove useful in directing future clinical research initiatives involving foot orthotics for back pain.
METHODS: The biomedical literature was searched to identify key articles that reveal the current state of knowledge on the benefits of foot orthotics for LBP related to biomechanical mechanisms and clinical outcomes. Database searches were conducted using PubMed, EBSCO , GALE, Google Scholar, and clinicaltrials.gov. The following search terms were used for each database (“foot Page 4 of 21
orthotics”, insoles, “foot orthoses”, “shoe inserts”, excluding “foot ankle”). In addition, reference lists from key articles were searched for relevant literature. Articles for use in this review were identified based on the level of evidence[8] as well as clinical relevance to orthotic use in
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treating LBP. Preference was given to recent meta-analyses and randomized controlled trials in
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the area of interest, where available.
Biomechanical mechanisms of foot orthotics for LBP:
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RESULTS:
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The high impact forces and repetitive stress associated with heel strike during gait has been implicated as a contributing factor in the development of both lower limb pain and LBP.[9] The
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added shock absorption properties of orthotics have been proposed as a significant source of pain relief. An early study of viscoelastic insoles showed a decrease of 42% in the peak vertical
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impact forces at heel strike.[10] Subsequent studies found strikingly positive effects of shock
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absorbing insoles alone to treat LBP with approximately 80% of subjects reporting significant
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improvement in both pain and mobility after one year of use. Forty five percent of patients from this study whom discontinued the intervention were found to have significant improvement in pain and mobility with conservative care alone, illustrating the wide variability experienced by those treated for LBP.[9]
Impaired or abnormal foot function has been implicated as a possible mechanism that may contribute to the development of LBP. Excessive pronation of the foot during gait has been proposed to induce prolonged and/or excessive internal rotation of the lower limb resulting in abnormal forward progression.[11] This hampered progression can result in a significant increase in strain at both the sacroiliac and lumbosacral joints. [11-13] These increased strains theoretically lead to increased pain and muscular dysfunction. Page 5 of 21
Ball and Afheldt 2002 highlighted the differences between rigid orthotics based on “Root theory” foot classification, where the focus of intervention is to maintain subtalar neutral position
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and semi-rigid orthotics with the intention of “supporting” the three arches of the foot.[14] This review, relying on several studies of biomechanical analysis of normal subjects,[15,16] cast
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some doubt on the utility of the Root approach. Three areas of criticisms were described: the
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poor reliability of clinical identification of subtalar neutral position, the unrealistic representation of non-weight bearing identification subtalar neutral position, and the lack of demonstrated
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functional significance of this position during normal gait.[14]
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The effect that static standing foot posture has on the incidence of injury or pathology has been a topic of much debate.[9,17-20] Predisposition to injury based on static arch height during
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standing has been proposed with several studies finding that those individuals with high arches
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had a higher incidence of lower limb pathology when compared to low arched
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individuals.[9,21,22] Natural shock absorption of the foot was addressed through biomechanical testing, those with higher arches were found to have more internal rotation of the tibia at heel strike and absorb shock earlier in stance phase.[23,24] Theoretically, this increases the capacity for shock absorption and should lead to a protective effect.
A recent study by Menz et al 2013 found that increased dynamic foot pronation, as measured with center of pressure excursion, was significantly associated with LBP in women, while the static posture of the foot was not. However, no such association was found in the male subjects. The implications of this finding are limited, as the back pain was only indicated on a body chart and not described in severity, duration, or frequency.[17]
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A recent review by Kendal et al 2014 summarizes the current understanding of dynamic aspects of functional foot kinematics associated with lumbopelvic muscular dysfunction.[25] The authors point to recent findings of increased navicular drop associated with LBP,[26] and
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decreased shock absorption found in those with a pronated static foot posture as evidence for the relationship.[23] The review however goes on to conclude that the changes in foot posture are
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associated with relatively small magnitude changes in pelvic posture, have little evidence of
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clinical significance.[25] The relationship between lumbopelvic muscular dysfunction and altered foot mechanics is puzzling. There is evidence of association between the two,[18,27] also
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there is evidence that each is associated with LBP.[28-30] In a review of both foot and lumbopelvic-hip motion Barwick et al 2012 summarizes nicely several key elements of the
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proposed mechanisms of orthotic intervention: affecting foot pronation,[31-33] internal tibial rotation,[32,34,35] joint moments,[32,36,37] muscular activation,[38-40] neuromuscular
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control,[41,42] and sensory feedback.[32,41,43,44] The authors concluded that evidence of
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coupling of the foot and lumbopelvic-hip complex suggests that the use of foot orthotics may
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have an effect on more proximal structures. [45]
Contradictory evidence is reported in the description of the kinematic effects of orthotic intervention, where multi-segment biomechanical models of the foot are able to give a more complete indication of the kinematic effects of orthotic introduction. Sinclair et al 2014 found that the introduction of custom orthotics acted to reduce motion in the coronal and transverse plane during running[46] opposing earlier work in this area that found no such reductions. [47,48] The authors hypothesize that the composition of the medial arch support may explain the discrepancy.[46] This area of research is rife with inconsistent results stemming from the comparison of studies describing custom interventions. The proprietary nature of many orthotic
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interventions hinders the ability of researchers to directly compare specific mechanisms of action, and has been identified as a barrier to research. [49]
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Small and widely disparate kinematic and kinetic changes have been documented with the use of foot orthotics; to date the clinical implications of these changes are unclear. The direct link from
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documented prolonged kinematic or kinetic changes to clinical efficacy has not been made.
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Clinical studies lack the rigorous biomechanical analysis needed while detailed biomechanical studies do not provide a longitudinal view of intervention and generally lack clinically relevant
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outcome measures. A truly translational approach is needed to address the evidence gaps that are
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currently present in this area of research.
Recommendations for studies on biomechanical mechanisms:
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There is a clear need for the dynamic biomechanical characterization of foot function prior to an
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intervention. The static characterization of foot posture falls short of giving a clear indication of
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foot dysfunction during gait. Interventions based on a clearly defined set of kinematic and/or kinetic variables would produce improved specificity of treatment effects. However, this approach is thwarted by the need for clinically available equipment, processes, and protocols by which to produce such a characterization.
Future research in the area of biomechanical consequences of foot orthotic intervention should focus on the systematic alteration of foot kinematics and/or kinetics during the stance phase of gait. These systematic changes should then be correlated to patient outcomes. It has been shown that the use of custom orthotics can have a variety of effects on both the kinematics and kinetics of the foot during the stance phase of gait. Placebo/Sham controlled trials should be developed to isolate specific kinematic or kinetic changes and relate those specific isolated changes to Page 8 of 21
outcomes of pain and/or function. With the wide availability of 3D scanning and printing technologies the possibilities for innovation are no longer hampered by the high costs and time consuming processes of casting/fitting and precision manufacturing. This technology advance
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might be most useful in the development of orthotic conditions that control specific kinematic or kinetic features of the foot during the stance phase of gait. This should help to highlight what
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biomechanical aspects of orthotic intervention are most important in the reduction of pain.
Additionally, future research should investigate the hypothesis of an individualized preferred
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movement pattern[33], where patient feedback combined with biomechanical principles drives the customization of the orthotic intervention. Again, with the growing availability and cost
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savings of 3D printing, an intervention may be modified based on feedback or can be
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systematically modified throughout a treatment plan to facilitate biological adaptation.
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Meta-analyses and RCTs on foot orthotics for the prevention of back pain
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Two meta-analyses of foot orthotic intervention used both in the treatment and prevention of LBP have been published.[50,51] When regarding the use of orthotics in for the prevention of LBP the Chuter et al 2014 meta-analysis revealed a 22% reduction in the risk of developing LBP with the use of orthotics compared to the control group, however this seemingly large decreased risk was not statistically significant.[50] Similarly, Sahar et al 2009 found no significant change in the pooled Risk Ratio associated with the use of foot orthotics versus sham or no intervention from three studies (Milgrom, Larsen, Schwellnus) including 2061 subjects.[51] Chutter et al 2014 go on to address the weak generalizability of this analysis based on the demographics and specific settings of the subject population, as all of the subjects included in their meta-analysis were male military recruits under 20 years of age. The external validity of such trials was also questioned as this age group would not be at great risk for developing LBP in the general Page 9 of 21
population (Chutter et al 2014).[50] One study[52] found that there was no statistical difference in the incidence of back pain among recruits provided with two different types of orthotic when compared to those provided with a simple shoe inserts. These findings are complicated by a high
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drop-out rate where only 67.5%, 45.5%, and 48.6% of subjects completed 14 weeks of training in the soft-custom, semi-rigid, or simple shoe insert groups respectively. The authors concluded
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that, neither the intention-to-treat analysis of all subjects given orthotics nor analysis of those
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completing training revealed significant differences in the incidence of LBP; therefore, prophylactic use of orthotics is not supported.[52] Mattila et al 2011 in a study of 228 military
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conscripts found no significant difference in risk of LBP requiring a physician visit between those given a custom orthotic vs no treatment over 6 months of military service.[53] They found
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that 33% of those given orthotics had at least one incidence of LBP compared to 27% of control subjects, a difference of 4.3% was found and an 80% compliance rate was reported for those in
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the orthotic group. The authors drew narrow conclusions based on the demographics of the
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subject population stating that “…we recommend that orthotic insoles not be used with an aim
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toward preventing LBP episodes in young male adults”.
The results of the meta-analysis itself due to the low number of high-quality studies was unable to provide conclusive evidence for or against the use of foot orthotics for the prevention of LBP. There was a recommendation for increased research in this area overall and for a focus on specific inclusion criteria that might provide homogeneous populations and identification of traits in those LBP patients that are most likely to benefit from foot orthotic intervention. Another limitation of the studies included in this analysis is the short time scales over which the effectiveness of intervention is assessed with an average intervention of 6.7 weeks with a range between 4 and 12 weeks.
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While the there is wide-spread agreement that there is lack of evidence for foot orthotic use in the prevention of LBP, the supporting literature cited is almost exclusively based on military recruits. This population allows for control of independent variables, such as equipment and
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activity level that would otherwise be difficult to achieve, providing excellent information. However, prospective RCTs that use a military setting may not reflect how these devices
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perform in the general population. As these studies were conducted in the context of military
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training, the limited age range and a dramatic increase in physical demands placed on the subjects may have had great implications as to the prophylactic effectiveness of the orthotic
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intervention.
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Recommendations for future studies on foot orthotics for the prevention of back pain: There are very few well-constructed prospective studies dealing with the ability of foot orthotics
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to prevent LBP. The RCTs that do exist are military based and are not widely generalizable to
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the public at large as they were done under conditions the average person is not likely to be
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exposed and in populations that are not likely to incur LBP if not for those conditions. There is therefore a need to identify means by which to enroll a large number of young to middle-aged subjects from the general public into a long-term prevention study. There are several challenges with this type of approach, including the high associated costs of a lengthy trial period, accurate dynamic characterization of foot function, reliable documentation of orthotic use, and reliable and systematic means of reporting incidence and duration of LBP.
Meta-analyses and RCTs on foot orthotics for the treatment of back pain Chutter et al 2014 assessed studies on the treatment of LBP (5 studies) and found a positive outcome trend in those using orthotics vs. those in a control group.[50] However, not all studies included in the analysis found statistically significant improvements, and the clinical significance Page 11 of 21
of these this trend was not addressed. It was noted that the most significant treatment effect was found in a study that limited the subject population to those with a pronated standing foot posture.[19] It was proposed that this finding may be due to a more homogeneous population
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only including subjects with LBP due to a similar etiology of LBP.[50] The implication is that impaired foot function may play a role in the development of LBP as discussed above. Other
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studies included in the meta-analysis concluded that there was significant evidence that the
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introduction of foot orthotics for those individuals with current LBP was beneficial. Almeida et al 2009 found that both custom and prefabricated insoles resulted in statistically significant
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reduction in back pain found in female workers performing mostly static standing duties.[54] However, this study lacked an adequate control group (“sham” or “no treatment”) for proper
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comparison. Shabat et al 2005 also looked at a working population (long-distance walking) using the MILLION questionnaire and found that patients reported a greater reduction (5.46 to 3.96 out
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of 10) in LBP when using true foot orthotics compared to 5.46 to 5.11 out of 10 with a placebo
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insole.[55] In the original study this reduction was found to be both statistically (p < 0.0001) and
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clinically significant (30% reduction in pain). The authors issued a strongly worded conclusion stating “In conclusion, it was proven that insoles causes improvement of LBP for subjects with repetitive loading such as walking long distances everyday”. However, Sahar et al 2009 in their systematic review using a different set of criteria did not find clinical significance in these results, and go on to point out several flaws in the study including unclear inclusion criteria, inappropriate randomization, missing data, and incomplete analysis.[51] Cambron et al 2011 focused on the feasibility of collecting LBP and disability data in patients with LBP treated with foot orthotics and those “wait-listed” for 6 weeks.[56] A significant reduction in both LBP and disability was found in the treatment group when compared to those in the wait-listed group at the 6-week time point, no further decrease in LBP or disability was found after 12 weeks of intervention. As this was designed as a feasibility study with a limited number of subjects in each Page 12 of 21
group the conclusions drawn by the authors were limited to the confirmed feasibility of such a study and the need for a larger study of similar design to confirm the initially positive
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results.[56]
It is generally accepted that the highest level of evidence for scientific discovery is the result of
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meta-analysis of aggregate data from high quality RCTs. In the absence of sufficiently
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homogeneous high quality studies to conduct such meta-analysis we must not discount the general trends of agreement of the high quality RCTs published in the past decade. Of those
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reviewed here, an overwhelming majority of the studies point toward effectiveness of foot orthotic intervention as having an ability to decrease LBP. While analysis of aggregate data was
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not possible due to the heterogeneity of the studies, the positive findings for the use of orthotics in each of the studies may point to a robust response independent of inclusion criteria or outcome
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measure.
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Two randomized control studies that are currently enrolling patients will hopefully add to the understanding of treatment effects of orthotic intervention. Dougherty et al[57] are collecting data in veteran population with LBP to assess the effect of orthotic treatment alone compared to that of a sham insole. The outcomes used will be visual analog scale (VAS) rating of back pain along with the modified Oswestry Disability Index (mODI) and the Patient Reported Measurement Information system (PROMIS) physical function assessment. The use of a sham control, multiple time points over a 24 week intervention, and clinically relevant outcome measures are key elements. Cambron et al.,[58] building on their previous pilot study, are currently collecting data in a chronic LBP population to assess the effect of orthotic treatment alone compared to that of orthotic intervention plus chiropractic care or no treatment (wait-list group). The outcomes used will be numeric pain scale rating of back pain along with the Page 13 of 21
Oswestry Disability Index (ODI). The use of a wait-list group, multiple time points over a 12 month intervention, and clinically relevant outcome measures are key elements.
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Recommendations for future RCTs on use of foot orthotic for the treatment of back pain: To ensure homogeneity in RCT studies and increase comparability in future work three key
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aspects have been identified: (1) the classification of LBP, (2) the treatment group(s) and control
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group(s), and (3) the intervention duration and outcome measures used. A more rigorous approach needs to be taken to the classification and sub-classification of LBP prior to enrollment
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in a RCT. The varied and mostly unknown etiologies of generalized LBP do not allow for definitive diagnosis and precise biomedical classification. There are many proposed clinical
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means by which to classify patients with LBP.[59] It has been proposed that comprehensive biopsychosocial approaches be used in order to delineate treatment paradigms.[59] The
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biopsychosocial sub-classification of patients enrolled into future RCTs would act to identify
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those characteristics likely to impact the effectiveness of the intervention. Future RCTs should
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make use of multiple control groups that include a well-defined sham and/or no treatment (waitlist), as well as multiple treatment groups that include “real world” adjunctive use. Both the proprietary nature of the orthotics industry and the customization of orthotics themselves lead to a heterogeneity of intervention between studies. The use of a “black box” model where the biomechanical mechanisms of the intervention are unknown is problematic if a mechanistic understanding of the intervention is the goal. However, if the goal is to demonstrate clinical effectiveness, the customized intervention should make use of patient feedback much in line with Nigg et al 2001 and the hypothesis of an individualized preferred movement pattern,[33] where a systematic approach to customization is documented. In addition accurate quantification of customization would allow for correlation to the aforementioned biopsychosocial (including biomechanical) classification of patients, helping to identify which aspects are crucial for Page 14 of 21
orthotic design. The use of validated outcome measures that include pain, physical function/disability, and psychosocial aspects of LBP should be collected during both early
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(weeks to months) and long term (years) time points during the intervention period.
Conclusions: Based upon the critical evaluation of the current research on foot orthotics related
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to biomechanical mechanisms and clinical outcomes, recommendations for future research to
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address the evidence-practice gaps on the benefits of foot orthotics for LBP include: 1) Mechanistic studies focused on clinical outcomes and that make use of dynamic
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characterization of foot function at baseline.
2) Controlled and systematic alteration of orthotic interventions based on this characterization.
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3) Utilization of patient feedback in the customization processes.
4) Prevention studies focused on well-defined subject populations most likely to benefit from
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prophylactic orthotic intervention.
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5) Treatment studies focused on biopsychosocial classification of LBP prior to orthotic
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intervention with sufficient treatment and control groups, examined over longer periods and utilizing validated clinical outcome measures.
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A review the biomechanical mechanisms underlying the effectiveness of foot orthotic treatment. A review of the current state of knowledge regarding the clinical use of foot orthotics to treat and/or prevent the occurrence of Low Back Pain. A discussion of the most influential studies in the area of foot orthotic conducted during the past decade. Recommendations based on our review that may prove useful in directing future clinical research are provided.
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