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perceived and interpreted by patients and can generate
positive or negative expectations (15). A placebo re-
sponse occurs when a medical treatment and its context
trigger specific expectations about a positive thera-
peutic outcome. Pre-existing optimistic expectations
can amplify the positive effects of treatments (placebo
effects), but negative expectations can also worsen
treatment in the form of side-effects or a decrease in
treatment-typical improvements (nocebo effects) (16).
Studies have shown that modifying the shape, colour
or price of a placebo drug can produce different pla-
cebo responses (17, 18), yet there are few studies that
explore and identify the contextual elements involved
in placebo and nocebo effects; this is highly relevant,
since the therapeutic effect of many treatments is inse-
parable from the context in which they are administered.
However, there are other phenomena that can explain
patients’ clinical improvement, such as the Hawthorne
effect, natural fluctuations in diseases, and regression to
the mean (19–21). The placebo effect can be overesti-
mated if these are not taken into account (22).
This randomized controlled trial (RCT) aimed to as-
sess whether a contextual element, such as the external
appearance of the rESW device, would influence clini-
cal outcomes in patients with chronic plantar fasciitis.
METHODS
Study design
This randomized controlled parallel assessor-blinded clinical
trial was conducted in a private rehabilitation and physioth-
erapy centre, “Salut i Esport”, in Santa Perpètua de Mogoda,
Barcelona province, Spain. Patients were recruited from this
centre and other private centres (n = 122) and from public cen-
tres (n = 13). A total of 135 patients were enrolled in the study
during 2014–15.
Study participants
Patients were referred to the lead investigator and considered for
participation in the study according to the inclusion and exclu-
sion criteria summarized in Table I. A total of 135 participants
were recruited and 128 completed the study (Fig. 1).
After providing written informed consent, patients with
chronic plantar fasciitis (more than 6 months’ duration) were
randomly assigned to the following 3 groups:
• Group I: standard device: therapy applied with a standard
rESW device (n = 45).
• Group II: sophisticated device: therapy applied with a modi-
fied standard rESW device designed to give a more attractive,
high-tech appearance, with a larger external component
(n = 45).
• Group III: austere device: therapy applied with a modified
standard rESW device designed to give a more austere,
unattractive, low-tech appearance, with a smaller external
component (n = 45).
Three Swiss Doloclast rESW devices (EMS Electro Medical
Systems, Nyon, Switzerland), which comply with all of the
www.medicaljournals.se/jrm
Table I. Inclusion and exclusion criteria for patients with chronic
plantar fasciitis enrolled in the present study
Inclusion criteria
Age over 18 years.
Able to understand the explanations about the potential benefits and risks
of participating in the study.
Diagnosis of chronic plantar fasciitis. Tested by clinical examination, meeting
at least 2 criteria:
• Pain on palpation of the proximal insertion of the plantar fascia (area of
the medial tuberosity of the calcaneus).
• Pain with the first weight-bearing step in the morning and/or after a
period of time sitting.
Duration of symptoms equal or superior to 6 months at the time of
enrolment.
Have received conservative therapy without success, at least 2 treatments.
The treatments may have been performed in isolation, in combination, or
consecutively.
Non-pharmacological treatments
• Physical therapy, such as ice, heat, iontophoresis or ultrasound.
• Physiotherapy, massage or stretching.
• Orthosis.
• Heel pads or bandages.
• Immobilization.
• Night splints.
Pharmacological treatments
• Topical application of analgesic or anti-inflammatory gels.
• Analgesics or oral anti-inflammatories.
• Local anaesthetic injection.
• Local corticosteroid injection.
Minimum period of time after receiving other treatments:
• 6 weeks from the last cortisone injection.
• 4 weeks from the last iontophoresis session.
Exclusion criteria
Neurological or vascular insufficiency in the painful heel.
Any inflammation at the level of the ankle.
History of rheumatic disease, collagenosis or metabolic diseases.
History of hypo- or hyperthyroidism.
Malignant disease with or without metastases.
Paget’s disease or calcaneal fat-pad atrophy.
Osteomyelitis (acute, subacute or chronic).
History of calcaneus fracture.
Patients on immunosuppressive therapy.
Patients on corticosteroid treatment longer than 3 months.
Patients with diabetes mellitus or cardiac or respiratory disease.
Patients on anticoagulant drugs.
Previous surgery on the painful heel.
Previous treatments with shock wave devices.
Significant abnormalities in liver function.
Pregnancy.
Infection in the treated area.
History or documented evidence of sciatica, peripheral neuropathy, such as
nerve compression or tarsal tunnel syndrome.
History or documented evidence of systemic inflammatory disease, such
as rheumatoid arthritis, ankylosing spondylitis, aseptic bone necrosis, or
Reiter’s syndrome.
History or documented proof of labour compensation or litigation for medical
conditions.
Patients who, in the opinion of the researcher, may be inappropriate for
inclusion in the study or would not comply with the study requirements.
Neurological deficits: sensory or motor deficits, abnormal tendon reflexes.
Bilateral plantar fasciitis.
European safety regulations for health equipment (Registra-
tion: EN-60601-1, Class I. Type BF IP40. 93/42 EEC) were
used. Two of the 3 devices (corresponding to groups II and III),
which were initially standard, were modified to change only
the external part of the device without affecting the safety of
the treatment or the technical performance of the equipment.
The same therapeutic radial extracorporeal shock waves were
used in all cases.
The study was approved by the Ethics and Research Com-
mission of Blanquerna School of Health Science, Ramon Llull
University (Barcelona, Spain). This study was carried out in