In the treatment of plantar fasciopathy, a conservative approach is typically chosen, focusing on addressing the risk factors that contribute to the development of this condition. A key risk factor is an abnormal foot posture and altered gait pattern. A commonly used intervention to address these risk factors is the use of custom-made insoles, created by specialized paramedics such as podiatrists. Custom-made insoles are typically created using a three-dimensional representation of the individual’s foot intended to influence a patient’s foot anatomy and gait pattern.  Despite the widespread use of this conservative treatment, there is uncertainty about their effectiveness in the treatment of plantar fasciopathy. In this section, the role of different types of custom-made insoles in terms of their effectiveness in the treatment of plantar fasciopathy is explored.

Summary of Findings

Custom-made insoles as treatment for plantar fasciopathy?

Population: Patients with plantar fasciopathy

Intervention: Custom-made insoles

Comparison: Placebo / sham

_{¹ Imprecision: very serious. Due to low number of participants (-1 level), due to population without deviated foot position (-1 level).}

_{² Imprecision: very serious. Due to overlap of the upper limit of the 95% confidence interval with the minimal clinically important difference (-1 level), due to population without deviated foot position (-1 level).}

_{³ Indirectness: serious. Due to an indirect measurement for the outcome, resulting from measuring discomfort instead of patient reported satisfaction (-1 level), due to population without deviated foot position (-1 level).}

   _{Imprecision: very serious. Due to low number of participants (-1 level), due to population without deviated foot position (-1 level).}

Description of studies

A total of two studies (one systematic review and one RCT) were included in the analysis of the literature (one systematic review and one randomized controlled trial) . Important study characteristics are summarized in table 2. The assessment of the risk of bias is summarized in the risk of bias tables (under the tab ‘Evidence tabellen’).

Rasenberg (2018) performed a systematic review with meta-analysis to assess the effect of different foot orthoses on pain, function, and self-reported recovery in participants with plantar heel pain and compare them with other conservative interventions. Twenty studies were included in the review covering data of a total of 1756 participants. Eight different types of foot orthoses were investigated. Three studies compared a custom-made orthosis with a sham orthosis in a randomized controlled setting and were included in this summary of literature (Landorf, 2006; Oliveira, 2015; Wrobel, 2015). These three studies had a low risk of bias and covered data of 207 participants. Short-term pain and short-term function were reported in all three studies. Midterm pain and function were reported in one study (Oliveira, 2015) and long-term pain and function were reported in another study (Landorf 2006). Wrobel (2015) also assessed quality of life.

Rasenberg (2021) performed a double-blind three-armed randomized controlled trial in the Netherlands, to compare custom-made insoles to sham insoles and usual care in terms of pain at rest and during activity. In this study, 185 participants with a clinical diagnosis of plantar heel plain for two weeks to two years were randomized into the custom-made insole group (n=70), sham insole (n=69) or usual care (n=46). Duration of follow-up was six months. The primary study outcome was pain severity at 12 weeks of follow-up. The risk of bias for this study was considered low as randomization and blinding were performed accurately, there were no conflicts of interest reported, and the funder had no role in any part of the study.

Table 2. Characteristics of included studies

_{¹Assessed by the authors of the systematic review.}

_{² For further details, see risk of bias table in the appendix.}

_{Abbreviations: FFI(-R): Foot Function Index(-Revised). FSHP: Foot Health Status Questionnaire. NRS: Numeric Rating Scale. SF-36 / SF-12: Short Form Health Survey with 36 or 12 items. VAS: Visual Analogue Scale}

Results

1. Pain (crucial)

All four studies assessed pain scores. Landorf (2006) and Oliveira (2015) measured it with the pain domains of the Foot Health Status Questionnaire which ranges from 0 to 100 and a higher score indicates better foot status. Rasenberg (2021) and Wrobel (2015) used the pain subscale of the (Revised) Foot Function Index which ranges from 0 to 100, a higher score indicates a worse foot status. Because of differences in directionality of the outcomes (e.g., higher scores reflecting better or worse outcomes), the data of Landorf (2006) and Oliveira (2015) were inversed in order to set to the same direction.

In addition, the Visual Analogue Scale (VAS) was used by Oliveira (2015) and Wrobel (2015) and the Numerical Rating Scale (NRS) was by used Rasenberg (2021). These scales range from 0 to 10 and a higher score indicates more pain.

1.1 Short-term (at 3 months)

All studies assessed pain after three months of follow-up including data of 346 participants. Based on the pain scores measured with the FHSQ or FFI-(R) questionnaire, the standardized mean difference for short-term pain when comparing custom-made insoles to sham insoles was -0.14 (95% CI -0.35 to 0.07), in favor of custom-made insoles (figure 1). This difference is not considered clinically relevant. 

_{Figure 1. Forest plot of short-term pain measured with the pain domains of the FHSQ or FFI(-R) questionnaires in the comparison of custom-made insoles versus sham insoles among participants with plantar heel pain}

When analyzing pain in rest on the VAS or NRS scale (both scales range 0-10), the mean difference for short-term pain was -0.10 (95% CI -0.75 to 0.55), in favor of custom-made insoles (figure 2). This difference is not considered clinically relevant. 

_{Figure 2. Forest plot of short-term pain in rest measured with the VAS or NRS scale in the comparison of custom-made insoles versus sham insoles among participants with plantar heel pain}

1.2 Mid-term (6 months)

Pain at 6 months was assessed in two studies with data of 210 participants (Oliveira 2015, Rasenberg 2021). Based on the pain scores measured with the FHSQ or FFI questionnaire, the standardized mean difference for mid-term pain when comparing custom-made insoles to sham insoles was -0.04 (95% CI -0.31 to 0.23), in favor of custom-made insoles (figure 3). This difference is not considered clinically relevant. 

_{Figure 3. Forest plot of short-term pain measured with the pain domains of the FHSQ or FFI questionnaires in the comparison of custom-made insoles versus sham insoles among participants with plantar heel pain}

When analyzing pain in rest on the VAS or NRS scale, the mean difference for mid-term pain was -0.14 (95% CI -0.84 to 0.57), in favor of custom-made insoles (figure 4). This difference is not considered clinically relevant. 

_{Figure 4. Forest plot of mid-term pain in rest measured with the VAS or NRS scale in the comparison of custom-made insoles versus sham insoles among participants with plantar heel pain}

1.3 Long-term (12 months)

Pain at 12 months was reported by Landorf (2006). The adjusted estimate of effect was -0.1 (95% CI -7.8 to 7.7) in favor of sham insoles. It was reported to not be statistically significantly different. The effect was not clinically relevant.

2. Function (crucial)

All four studies assessed function scores. Landorf (2006) and Oliveira (2015) measured it with the function domains of the Foot Health Status Questionnaire which ranges from 0 to 100 and a higher score indicates better foot status. Rasenberg (2021) used the function subscale of the Foot Function Index which ranges from 0 to 100, a higher score indicates a worse foot status. Wrobel (2015) only reported the total Foot Function Index-Revised score and not the score of the function subscale. Therefore, data of Wrobel (2015) could not be pooled. Because of differences in directionality of the outcomes (e.g., higher scores reflecting better or worse outcomes), the data of Landorf (2006) and Oliveira (2015) were inversed in order to set to the same direction. 

2.1 Short-term (at 3 months)

All studies assessed function after three months of follow-up. Based on three studies with 298 participants, the standardized mean difference for short-term pain when comparing custom-made insoles to sham insoles was -0.12 (95% CI -0.37 to 0.12), in favor of custom-made insoles (figure 5). This difference is not considered clinically relevant.

Wrobel (2015) reported no statistically significant differences in total FFI-R score.

_{Figure 5. Forest plot of short-term function measured with the function domains of the FHSQ or FFI questionnaire in the comparison of custom-made insoles versus sham insoles among participants with plantar heel pain}

2.2 Mid-term (6 months)

Function at 6 months was assessed in two studies (Oliveira 2015, Rasenberg 2021). The standardized mean difference for mid-term pain when comparing custom-made insoles to sham insoles was -0.10 (95% CI -0.42 to 0.22), in favor of custom-made insoles (figure 6). This difference is not considered clinically relevant. 

_{Figure 6. Forest plot of short-term function measured with the function domains of the FHSQ or FFI questionnaire in the comparison of custom-made insoles versus sham insoles among participants with plantar heel pain}

A systematic review of the literature was performed to answer the following question(s):

Wat is de effectiviteit van op maat gemaakte op maat gemaakte zolen in vergelijking met sham/placebo als behandeling van patiënten met fasciopathie plantaris?

Table 1. PICO

Relevant outcome measures

The guideline panel considered pain and function as a crucial outcome measure for decision making; and return to sport, patient satisfaction and quality of life as an important outcome measure for decision making.

The guideline panel defined 10% as a minimal clinically important difference for both continuous as well as dichotomous outcome measures. This includes a 10% difference on the outcome measurement on a continuous scale or a Relative Risk (RR ≤ 0 .90 and ³ 1.1). In case a standardized mean difference was reported, the previously used GRADE default was used, ≤-0.5 SMD ≥ 0.5 as minimal clinically (patient) important differences. 

Search and select (Methods)

The databases Medline (via OVID) and Embase (via Embase.com) were searched with relevant search terms until 23 May 2024. The detailed search strategy is listed under the tab ‘Literature search strategy’. The systematic literature search resulted in 382 hits. Studies were selected based on the PICO criteria. 15 studies were initially selected based on title and abstract screening. After reading the full text, 13 studies were excluded (see the exclusion table under the tab ‘Evidence tabellen’) and two studies were included.