Role of Insole Material in Treatment of Plantar Fasciitis: A Randomized Clinical Trial

Abstract

Category: Hindfoot; Other Introduction/Purpose: Plantar fasciitis (PF), a leading cause of persistent heel pain, results in almost a million physician visits annually. Conservative treatment is often the first line of management with insoles being frequently prescribed. While multiple studies have compared insoles based on the degree of customization to foot contour, the literature is lacking in data comparing insoles based on their material. In this randomized clinical trial, we compared the early effects of foam, polyurethane, and carbon fiber insoles in the treatment of PF, using a robust set of PROMS. Methods: A randomized clinical trial was designed at the foot and ankle research center of a tertiary care hospital in Massachusetts. Adult patients diagnosed with PF who had not received injectable or surgical treatment for it were included. Participants who consented were randomly allocated one of the three prefabricated insoles – carbon fiber insole (Group 1, n=13), polyurethane insole (Group 2, n=13), or foam insole (Group 3, n=9) for regular use. Their response was recorded using PROMIS 3a (for pain intensity), PROMIS 4a (for pain interference), FAOS (Foot and Ankle Outcome Score), and VAS for pain at baseline (T0), two (T2), six (T6) and twelve weeks (T12). A per-proto analysis was undertaken using Kruskal Wallis and Friedman tests. P< 0.05 was set as the level of significance. Results: Among groups 1, 2 and 3, the mean age of participants was 51.9±13.2, 51±12.5, and 47.9±13.5 years respectively and baseline weight varied as 211.6±32.7 lbs, 193.6±59.3 lbs, and 180.7±33 lbs respectively (p>0.05 for both). The group-wise distribution of participants based on sex and laterality of the affected foot showed no difference. Participants in each group reported similar intensity of the pain (VAS) at baseline and at all follow-up time points (p>0.05). A comparison of outcomes between baseline and subsequent timepoints showed significant improvement in quality of life (FAOS) at T12 (p=0.047) for carbon fibre insole users (Figure 1), significant pain relief on PROMIS Pain intensity and Pain Interference questionnaires for foam insoles at T3 and T12 (p=0.0003, 0.036 respectively). Conclusion: Carbon fiber insoles offered slightly better pain relief as early as six weeks into treatment and improved quality of life after twelve weeks of use. A possible link between the material of insole used and effective treatment of PF may exist. Conducting further analyses on the position of the foot during gait while using insoles and designing the insoles based on patient-specific criteria should be considered for future research.