Research Review By Dr. Kent Stuber©

Date Posted:

June 2009

Study Title:

Effectiveness of prefabricated and customized foot orthoses made from low-cost foam for noncomplicated plantar fasciitis: a randomized controlled trial

Authors:

Baldassin V, Gomes CR, Beraldo PS

Author's Affiliations:

Postgraduate Rehabilitation Sciences/SARAH Rehabilitation Hospital Network, Sarah, Brazil

Publication Information:

Archives of Physical Medicine & Rehabilitation 2009; 90: 701-706.

Background Information:

Plantar fasciitis (PF) is largely believed to be due to repetitive trauma or microtrauma at the origin of the plantar fascia or aponeurosis. The natural history of PF indicates that it should usually resolve within one year of onset; however the pain can be quite disabling, particularly in the first few months.

As with most other musculoskeletal conditions, a useful intervention for PF should temporally improve the natural history of the condition and reduce pain and its impact on quality of life and ability to complete activities of daily living. Numerous treatments have emerged as possible options for plantar fasciitis including stretching, ice, chiropractic manipulation, orthotics, and NSAIDs, among others. Orthotics provide arch support and cushioning when walking and standing, thus theoretically reducing strain on the fascia. Orthotics are one of the more studied interventions for plantar fasciitis, both pre-fabricated and custom made varieties, although the ones generally employed in research studies have been made of rubber of varying thicknesses and densities.

Previous studies comparing pre-fabricated and custom made orthotics have not shown one to be clearly superior over the other. As the authors of this paper elucidate, EVA is a feasible option for manufacturing orthotics. EVA is a low-cost foam with appropriate properties for use in orthotics (to date this material has not been well studied in the literature on PF). This paper reported on an RCT comparing pre-fabricated and custom made orthotics made of EVA for the treatment of uncomplicated PF.

Pertinent Results:

125 subjects completed at least one of the 2 follow-up sessions, 63 in the pre-fabricated orthotic group and 62 in the custom made orthotic group. The only differences of note between groups at baseline were in BMI and symptom duration. The subjects were mostly female, sedentary, walked on cement and wore low-heeled shoes. There was a 12% drop-out rate (these subjects did not attend a single follow-up session). Both groups noted similar levels of improvement on the Functional Foot Index (FFI) and palpation throughout the follow-up period. On the FFI pain subscale both groups significantly improved but without significant difference between groups.

Scores on the FFI were slightly higher for the pre-fabricated group at both follow-up points, but not significantly. Participants in both groups largely believed that they received a custom orthotic. 67% of subjects received some type of co-intervention (no differences between groups in terms of number receiving co-interventions), 40% did Achilles tendon stretches, 28% used ice or NSAIDs. There were no side effects from the intervention noted in either group.

Clinical Application & Conclusions:

The authors note that the cost of supplying pre-fabricated EVA orthotics is approximately half that of the custom made ones used in this study. As pre-fabricated EVA orthotics were essentially as effective as the custom made EVA orthotics over the 8 week course of this study, the authors concluded that the pre-fabricated orthotics should be selected in the treatment of uncomplicated PF, particularly when taking a cost analysis into account.

This study provides some options for clinicians who see patients with PF. The reader could consider the use of EVA-composed orthotics in the future, however it should be noted that this is the first study that has evaluated EVA-made orthotics for PF and one should not likely completely re-vamp their approach to orthotics based on the results of one study. One of the biggest issues in the orthotic industry is differences in materials used and methods employed (with respect to casting and manufacturing). These differences within the industry make it difficult for clinicians to make a truly evidence-informed decision.

There are no studies comparing EVA-composed orthotics with more conventional orthotic materials (rubber and the like). A suggested future study would compare pre-fabricated and custom made orthotics made of EVA with those made of rubber (a 4 group RCT for example). Having said that, the improvements that subjects in both groups in this study experienced were statistically significant indicating that EVA orthotics are worth consideration, particularly given how cost effective they are compared with their rubber counterparts (and particularly the pre-manufactured orthotics).

However, there is no evaluation or mention made of the durability of EVA orthotics and frequently PF patients who are prescribed orthotics wear them on a fairly continuous basis and do not always discontinue their use once symptoms abate. These are all factors that require further inquiry and based on the successful use of EVA orthotics in this study, it is hopeful that EVA orthotics will receive more attention in plantar fasciitis trials.

Study Methods:

Inclusion criteria for this study consisted of subjects 18 years of age or more with plantar fasciitis (first-step pain, tenderness of the medial calcaneal tuberosity). Complicated PF was excluded as were pregnant women, those with a history of cancer, inflammatory arthritides, and those who had previously tried orthotic therapy. 142 subjects were admitted to the study and randomized into either a group that received pre-fabricated orthotics (made of 95% EVA) or custom made orthotics (made of 95% EVA).

Baseline data was obtained and only one foot was included in the analysis of patients with bilateral symptoms (either the more symptomatic foot, or the right one if they were equally symptomatic). Subjects were given orthotics for both feet according to their group allocation. The custom made orthotic was made using an EVA foam impression (readers are likely familiar with the use of such foam to create foot impressions). All subjects (in both the pre-fabricated and custom made orthotic groups) went through the process of having foam impressions made of their feet to aid with blinding. Steps were taken to make the custom and pre-fabricated orthotics as similar as possible. Subjects were asked to show the orthotics to the evaluating physiotherapist, who was blinded.

Subjects and physiotherapists were asked to guess which type of orthotic they received to see how well the blinding had worked. Subjects who noted discomfort from the orthotic were asked to use the orthotic for at least one week. Subjects were allowed to use any co-intervention that they pleased but asked to report use of co-interventions to the authors to aid with analysis.

The main outcome measure used in this study was the Functional Foot Index (FFI) pain subscale, which looks at foot pain in various situations using visual analog scales completed by the subject. The authors modified the FFI pain subscale by adding an additional question (bringing the subscale up to 10 questions) on pain on getting up in the morning (very useful in a study of PF). Subjects completed the FFI with a blinded physiotherapist at baseline, 4 and 8 week follow-ups.

The total of the FFI was also analyzed as was pain on palpation of the medial calcaneal tuberosity using a visual analog scale. Outcomes were analyzed using an intention to treat principle. A difference of less than 13-15 points (or mm on the VAS) was deemed to be insignificant regardless of the initial pain level (depending on the sample size). Subjects who attended at least one of the follow-up sessions were included in the analysis; those who did not were considered drop outs. 117 of the 142 subjects attended follow-up at 4 weeks, 105 attended the 8 week follow-up session.

Study Strengths / Weaknesses:

This study had a fairly high degree of internal validity (actual correctness of the results in the study), the assessor blinding was of particular value in increasing the validity of this study. Both subjects and blinded assessors were unable to guess the allocation of subjects with any great degree of accuracy, indicating that the blinding was successful.

Creating custom molds for all subjects may have assisted the blinding. It is also helpful that the subjects in this study showed similarities with other subjects in PF studies. The randomization produced nearly equivalent groups at baseline.

The authors also conducted this study in a pragmatic fashion by allowing co-interventions, which is reasonable because patients with PF will often use more than one intervention to relieve their foot/heel pain.

Study weaknesses include the differences between groups at baseline mentioned previously (BMI, symptom duration), indicating that the randomization did not create equal groups, although the authors did adjust for this in their analysis. The 12% drop out rate was fairly high but was essentially equal between groups and the drop outs did not differ greatly from those who remained in the study.

The authors could not completely explain away the potential for Hawthorne effects (the effect of being studied) or the impact of co-interventions to produce improvements in findings, although they did analysis to see if subjects who received co-interventions had improved results over those who did not receive co-interventions and did not find this to be the case.

One issue that the authors do not bring up is that subjects may have under-reported their use of co-interventions as they may have been concerned about the authors being displeased with them, etc. The authors concede that the study is likely underpowered but felt that it was not so underpowered that increasing the power would lead to a different conclusion. In addition, the lack of long-term follow-up is a weakness to this study, even though as the authors point out, the condition has a somewhat short natural history.

Additional References:

  1. Stuber K, Kristmanson K. Conservative therapy for plantar fasciitis: a narrative review of randomized controlled trials. Journal of the Canadian Chiropractic Association 2006; 50(2): 118-133.
  2. Hawke F, Burns J, Radford JA, du Toit V. Custom-made foot orthoses for the treatment of foot pain. Cochrane Database of Systematic Reviews 2008, Issue 3. Art. No.: CD006801. DOI: 10.1002/14651858.CD006801.pub2.