Is radial extracorporeal shock wave therapy (rESWT), sham-rESWT or a standardised exercise programme in combination with advice plus customised foot orthoses more effective than advice plus customised foot orthoses alone in the treatment of plantar fasci…

Design

In this randomised controlled trial (RCT) with a four-arm parallel-group design, participants were blinded to rESWT and sham-rESWT treatments but not to other treatments. The trial was conducted at the Department of Physical Medicine and Rehabilitation at Oslo University Hospital from March 2018 to January 2023. The study’s protocol was previously published,23 (online supplemental file 2) and the trial is registered at ClinicalTrials.gov. The reporting follows the Consolidated Standards of Reporting Trials guidelines, the Template for Intervention Description and Replication checklist, the Consensus on Exercise Reporting Template checklist24–26 and the CHAMP statement.27

Participants

Patients between 18 and 70 years of age who were referred by local general practitioners (GPs) to the outpatient clinic for heel pain were eligible for inclusion in the study. Inclusion criteria were pain for greater than 3 months localised to the proximal insertion of the plantar fascia on the medial calcaneal tuberosity and tenderness to palpation corresponding to the painful area. Participants had to report a pain intensity during activity in the previous week on the Numeric Rating Scale (NRS) of 3 or higher, be residents of Norway and understand oral and written Norwegian. The exclusion criteria were treatment with rESWT within the last 3 months, spondyloarthropathy or rheumatoid arthritis, plantar fibromatosis, tarsal tunnel syndrome, polyneuropathy, previous surgery with osteosynthesis material remaining in the foot or ankle and presence of contraindications for rESWT (use of anticoagulant drugs, pregnancy, bleeding disorders, epilepsy or pacemaker).

Patient and public involvement

Patients were involved in the cross-cultural adaption of the Foot Function Index Revised Short form (FFI-RS) outcome measure.28 Interviews with 15 patients regarding their experiences to live with persistent plantar fasciopathy informed the present project.6 The results of this RCT have been presented and discussed with the service-user network at the Research Centre for Habilitation and Rehabilitation Models and Services (CHARM), University of Oslo.

Randomisation and blinding

After clinical examination and baseline assessments the patients were randomised to one of the four treatment groups in blocks of eight in a 1:1 ratio. A researcher not involved in the trial generated the allocation sequence using a computer-generated randomisation schedule which was electronically concealed. This researcher communicated the allocation to a physiotherapist (project coordinator) who further communicated the group allocation to the patients. The patients were blinded for the rESWT and sham-rESWT. The same physiotherapist, not blinded to treatment allocation, delivered the treatments to all four groups. All other researchers were blinded to group allocation. To evaluate the success of the blinding procedure, patients in the rESWT and sham-rESWT groups were asked after their final treatment if they believed they had received real or sham treatments or if they did not know.

Baseline assessments and interventions

During the first visit, all patients underwent a clinical examination and ultrasound scan performed by one of three physicians.23 The patients completed self-administered questionnaires covering sociodemographic and clinical factors and the primary and secondary outcome measures. After the first visit and before randomisation, the physiotherapist orally communicated standardised information on pathogenesis, aetiology and prognosis, advice to stay physically active within pain tolerance and to use proper footwear with cushioning. The participants also received a written handout containing the information (online supplemental appendix 1). The patients were then referred to a Certified Prosthetist/Orthotist (CPO) from Sophies Minde Ortopedi, who performed a 3D scan of the foot to prepare the customised foot orthoses. The orthoses were made of a semirigid material called Comfort-Line (online supplemental appendix 1). The patients were instructed to wear the orthoses as much as possible and were offered one follow-up consultation if the orthoses required further customisation. The physiotherapist providing the interventions had over 20 years of experience in treating patients with lower extremity musculoskeletal disorders. All patients were asked to refrain from any other treatment during the trial.

Advice plus customised foot orthoses

Patients randomised to this group received the above described information and advice, plus customised foot orthoses and had no other interventions or contacts provided throughout the trial except for the planned follow-ups. The intervention is comparable to the treatment we usually provide at the outpatient clinic for these patients and was labelled ‘usual care’ in the protocol (online supplemental file 2)23 and in ClinicalTrial.gov.

rESWT/sham rESWT

The rESWT and sham-rESWT treatments were administered by the physiotherapist once a week for a total of three treatments, which is in line with previously suggested treatment protocols for plantar fasciopathy.29 The sham-rESWT was administered in the exact same way as the real rESWT, with the patient lying in a prone position (online supplemental appendix 1). Details of the rESWT and sham-rESWT treatments are reported in the study’s protocol (online supplemental file 2).23

High-load exercise programme

The exercise programme administered to the patients allocated to the exercise group included two exercises: unilateral heel raises and unilateral leg squats. Patients in this group were instructed to perform the exercises three times a week for 12 weeks. The heel raise exercise was performed as in the study by Rathleff et al using a rolled-up towel or similar underneath the toes standing on a stairway or similar location21 and the leg squad was performed the same way but standing on the floor. The programme was similarly as reported by Kongsgaard et al
30 slowly progressing throughout the period, starting with 12 repetition maximum (RM) in week 1–3, progressing to 6 RM in week 9–12. We used three sets per exercise. The details of the programme are described in the protocol (online supplemental file 2).23 Each patient participated in a total of eight sessions supervised by a physiotherapist at the outpatient clinic. To increase motivation, self-management and adherence, the patients received a thorough explanation and clear demonstration of the exercises as well as a written manual for use at home. They were informed of common side effects, such as muscle soreness and transient pain. Any barriers to execution were evaluated and adjustments were provided (online supplemental appendix 1). Patients were encouraged to record their repetitions, sets, weight load and number of training sessions, which the physiotherapist monitored to ensure progression (online supplemental appendix 1).

Outcome measures

Outcomes were assessed at baseline and at 3, 6 and 12 months. Patients attended baseline, 6-month and 12-month follow-ups at the outpatient clinic. For the 3-month follow-up, a letter containing the outcome measures was sent to the patients to complete and return.

Primary outcome

The primary outcome was patient-rated heel pain during activity in the previous week as measured by the NRS (NRSa) at 6 months. The NRS is an 11-point numeric scale ranging from 0 (‘no pain’) to 10 (‘worst imaginable pain’).31 In cases of bilateral plantar fasciopathy, patients were asked to identify the most painful heel (right or left), and the same side was assessed at each follow-up.

Secondary outcomes and assessments

The secondary outcomes were heel pain at rest in the previous week (NRSr), RAND-12 Health Status Inventory (RAND-12) score, FFI-RS score and Patient Global Impression of Change (PGIC) scale.

The RAND-12 is a generic patient-reported outcome measurement (PROM) that evaluates health-related quality of life. It consists of 12 questions and generates two scores: the Mental Component Summary score (MCS12) and the Physical Component Summary score (PCS12). Scores range from 0 to 100, with higher scores indicating better health.32 The FFI-RS is a region-specific PROM that consists of 34 questions with five subscales: pain, stiffness, difficulty, activity limitations and social issues. The total score ranges from 0 to 100, with lower scores indicating better foot health.33 We used the translated and validated Norwegian version of the FFI-RS.28

Patients’ overall impression of change in their health status was assessed using a PGIC scale. The patients answered one PGIC question: ‘Compared with the start of the study, how is your general health status today?’. Possible responses ranged from 1 to 7, where 1 was ‘very much better’, 4 was ‘no change’ and 7 was ‘very much worse’.

Sample size calculation

The sample size was calculated based on the primary outcome measure (NRS) at 6 months, with a comparison between the intervention groups and the control group (three comparisons) with two-sided t-tests. To achieve a power of 90%, significance level of 5%, assumed mean difference of 2 on the NRS,34 estimated SD of 2.7 (based on previous clinical data from the Department of Physical Medicine and Rehabilitation) and dropout of 20%, the sample size was calculated to be 200, with 50 in each group.

Statistical analysis

A statistical analysis plan was developed in collaboration with a statistician (CB) and published in ClinTrials.gov before any analyses were performed. All authors remained blinded to treatment allocation until after the primary analysis at 6-month follow-up had been conducted and the results had been decided on. The effect analysis used the intention-to-treat (ITT) population including all patients in their originally assigned groups, regardless of what treatment, if any, they received. The primary and secondary outcomes were analysed using a linear mixed-effects model to account for repeated measures over the follow-up period (baseline and 3, 6 and 12 months). The model included fixed effects for time and treatment group×time interaction. Random intercept and slope models were used. Based on this model, the primary effectiveness outcome of between-group differences in change from baseline to 6-month follow-up with 95% CIs was estimated. Within-group changes from baseline to 6 months were calculated for all treatment groups. Between-group differences in mean change over 3, 6 and 12 months were also estimated. A statistical significance level of 5% was applied. Post hoc analysis was performed for the PGIC scale using the Mann-Whitney U test to assess differences between the groups at 6 months.

The per-protocol analysis included all patients who were randomised and received treatment without deviating from the protocol (for the rESWT/sham-rESWT treatments, completing at least two out of three treatments, and for the exercise programme, completing at least six out of eight sessions with the physiotherapist or at least 30 out of 36 exercise sessions), and outcomes were analysed according to treatment group.

Statistical analyses were performed using IBM SPSS Statistics for Windows V.29 (Armonk, NY: IBM Corp) and Stata V.17 (College Station, TC: StataCorp LLC).

Equality, diversity and inclusion statement

The author team consisted of six women and one man from different disciplines including junior and senior researchers. We included all eligible patients regardless of sex, race/ethnicity/culture and socioeconomic level. The analyses did not consider inequities regarding gender, race, socioeconomic status or marginalised groups.

Protocol deviations

Due to the COVID-19 restrictions no inclusions were made between 12 March 2020 and 24 April 2020 and between 13 March 2021 and 22 April 2021. Six-month and 12-month follow-ups were performed by phone and questionnaires sent by post in these periods. In the exercise group some of the sessions with the physiotherapist were done by phone or video and for two patients rESWT treatment was delayed for 2 months because of the COVID-19 restrictions. In the per protocol analysis timing of follow-up visits could not be included as a criterion as stated in the analysis plan, because of deficient registration. Ultrasound measurements of the plantar fascia was removed as a secondary outcome from ClinicalTrials.gov in November 2019 due to lack of reliability.

Enrolment and follow-up

Of 320 patients referred to the clinic with heel pain, 200 patients underwent randomisation for inclusion in the study. Patients were referred by local GPs. A few were referred from specialised care. Information about the study was available for the public on the web site of Oslo University Hospital, in addition GPs received information letters about the study on three occasions during the inclusion period. 184 (92%) patients attended the 6-month follow-up, and all patients who underwent randomisation were included in the ITT analysis (figure 1). The final 6-month follow-up was conducted in August 2022 and the final 12-month follow-up was completed in January 2023. Baseline demographic and clinical data are displayed in table 1. Any recorded concomitant treatments are provided in online supplemental appendix 1. 23 of 174 patients reported receiving treatments in addition to the allocated interventions while enrolled in the study at 6 months, between five and seven in each group. There were no major harms registered as a result of any of the study’s interventions except for treatment-related pain and discomfort in all treatment groups (online supplemental appendix 1).

Figure 1

Flowchart of participants included in the study. A & CO, advice plus customised foot orthoses; ITT, intention-to-treat; NRS, Numeric Rating Scale; rESWT, radial extracorporeal shock wave therapy.

Primary outcome

The results of the primary analysis revealed no statistically significant between-group differences in mean change in NRSa from baseline to 6 months in the rESWT, sham-rESWT and exercise groups compared with advice plus customised foot orthoses. At 6 months, patients in all treatment groups demonstrated statistically significant improvements in the primary outcome compared with baseline (table 2). At 6 months the mean change of NRS exceeded the minimally important change (MIC) of 234 in all groups. Analysis of the mean change in NRSa scores from baseline to 3-month, 6-month and 12-month follow-ups showed no statistically significant between-group differences (figure 2 and online supplemental appendix 1).

Figure 2

Intention-to-treat analysis of change in heel pain during activity in the four treatment groups. Whiskers represent 95% CI. Numeric Rating Scale during activity in the previous week (pain activity (NRSa)). Y axis shows scale from 0 to 10; higher scores indicate more pain. A & Co, advice plus customised foot orthoses; rESWT, radial extracorporeal shock wave therapy.

Secondary outcomes

The analysis of the secondary outcomes also showed no statistically significant between-group differences in mean change from baseline to 6 months in the rESWT, sham-rESWT and exercise groups compared with advice plus customised foot orthoses. Mean within-group changes in secondary outcome measures from baseline to 6-month follow-up showed statistically significant improvement in all intervention groups except for the MCS12 score derived from the RAND-12 in the sham-rESWT group (table 2). Analysis of the mean changes in secondary outcomes from baseline to 3, 6 and 12 months showed no statistically significant between-group differences (figure 3 and online supplemental appendix 1). On the PGIC scale, 12.5% reported ‘very much improved’, 30.5% ‘much improved’, 31% ‘minimally improved’, 19.5% ‘unchanged’, 3% ‘minimally worse’ and 3.5% ‘much worse’, with no significant between-group differences at 6-month follow-up. No participants categorised themselves as ‘very much worse’.

Figure 3

Intention-to-treat analysis of change in secondary outcome measures in the four treatment groups. Whiskers represent 95% CI. (A) Numeric Rating Scale at rest in the previous week (pain rest (NRSr)). Y axis shows scale from 0 to 10; higher scores indicate more pain. (B) Foot Function Index-Revised Short Form (FFI-RS). Y axis shows only scores from 10 to 60; lower scores indicate better foot function. (C) RAND-12 Health Status Inventory (RAND-12) Physical Component Summary score (PCS12). Y axis shows only scores from 30 to 60; higher scores indicate better physical health. (D) RAND-12 Mental Component Summary score (MCS12). Y axis shows only scores from 30 to 60; higher scores indicate better mental health. A & Co, advice plus customised foot orthoses; rESWT, radial extracorporeal shock wave therapy.

Per-protocol analysis

Compliance was high in the rESWT and sham-rESWT groups. Two patients in the rESWT group and one patient in the sham-rESWT group did not complete the treatment as per protocol. In the exercise group, slightly lower compliance was observed, with 37 of 50 patients (74%) completing treatment as per protocol. The results of the per-protocol analysis did not reveal between-group treatment effects (online supplemental appendix 1).

Blinding of rESWT groups

In the rESWT group, 79% (38 of 48) of patients correctly guessed that they received real rESWT treatment, 8% (4 of 48) guessed sham treatment and 13% (6 of 48) answered ‘I don’t know’. In the sham-rESWT group, 61% (30 of 49) guessed that they had received real rESWT, while 16% (8 of 49) correctly guessed that they had received sham treatment, and 22% (11 of 49) answered ‘I don’t know’.

Principal findings

In this trial evaluating patients with plantar fasciopathy, no additional benefit of rESWT, sham-rESWT or a high-load exercise programme over advice plus customised foot orthoses alone was observed in improving pain, foot function and health-related quality of life. All treatment groups improved significantly in all outcomes from baseline to 6 months, except for the Mental Component Summary score of RAND-12 in the sham-group. The ITT analysis of the mean changes in the primary and secondary outcomes at 3, 6 and 12 months revealed no significant between-group differences.

Ibrahim et al
16 and Gerdesmeyer et al
15 demonstrated that rESWT was superior compared with sham-rESWT, which contrasts with the results from the present trial. The previous studies are comparable methodologically to the present RCT, but neither assessed a patient evaluation of the blinding. The uncertainty regarding the success of blinding, may have affected the results. A recent systematic review and meta-analysis have revealed the powerful placebo effects of ESWT in the treatment of plantar fasciopathy35 and may be an explanation of the improvements in the sham-rESWT group in the present study. The present study complement the results of a recent systematic review including RCTs comparing radial or focused ESWT with placebo showing no superior effects of shock wave therapy.14

In contrast to previous trials21 22 36 the physiotherapist in the present study conducted multiple sessions with patients in the high-load strength training group to provide guidance and ensure adherence, as the ability to attain sufficient progressive loading can influence treatment outcomes.37 Most patients in the exercise group (74%) completed according to the per protocol, though the physiotherapist made individualised adjustments that deviated from the planned regimen. Few patients reached 6 RM at week 9–12. Individualisation is necessary in clinical practice, and Riel et al
36 found no differences in the effectiveness of self-dosed and predetermined exercise programmes for patients with plantar fasciopathy. The plantar fascia is not considered a regular tendon, as it has no direct in-line muscular attachment. This may cause a response to high-load strength training that differs from that of other tendons in the lower extremities, which may explain the lack of benefit of the training programme observed in this study. It is possible that future trials on other types of progressive strengthening programmes provide different results.38

The content of the ‘advice plus customised orthoses’ intervention was based on our experience and the latest research and was developed in late 2017 and close to the ‘usual care’ at our outpatient clinic. It is comparable to the core approach for plantar heel pain management published in 202112 except for the guideline’s recommendations to tape and stretch the plantar fascia. In addition, unlike the recommendations in the management guide, all patients in the present study were provided customised orthoses. The inclusion of orthoses was a topic of debate during the planning of the trial, as most patients referred to our outpatient clinic have already tried prefabricated foot orthoses, and some have also tried customised foot orthoses. In order to standardise this part of the treatment, we provided customised foot orthoses to all participants. A recent systematic review found moderate evidence supporting customised orthoses on pain in the short term.14 Future high-quality trials may establish the type and role of orthoses in the treatment of plantar fasciopathy.

Strengths and weaknesses

This RCT included a large sample of patients, unlike the small samples used in most studies included in previous systematic reviews.10 11 39 We compared the effectiveness of common treatments with placebo and an intervention including advice plus customised foot orthoses, which enhanced the study’s relevance and external validity. The harms associated with the interventions were regarded as minor and only 13% (23 of 172) of the patients reported additional treatment during the trial at 6 months.

The sample size was based on an assumed mean difference in pain during activity of 2 on the NRS.34 Varying MIC values for pain has been reported.23 40 Increasing the sample size in order to detect smaller between group differences may lead to increased type I errors.

The study was completed at one hospital and the treatments was delivered by one highly experienced physiotherapist. In addition, most patients had long-term symptoms suggesting a more severe spectrum of the condition, typically representing a specialised care setting41 which limits generalisability. Customised orthoses are not routinely provided for patients with plantar fasciopathy and limits the applicability of the trial findings in a primary care setting.

The higher number of patients believing that they received real rESWT compared with sham-rESWT could be a result of patients’ previous experience with rESWT or the lack of blinding of the physiotherapist. However, this appeared to not impact the study’s result.

Comprehensive process evaluation was not performed in the present study and might have shed more light on the important components of the treatment arms as well as confounding environmental factors.42 Participating in a study conducted in a specialised care setting with multidisciplinary healthcare involvement or the natural course of the condition may have influenced the outcome. The present study was not powered for subgroup analyses, but explorative analyses of predictive factors for the total sample will be provided in a future manuscript.