Plantar fasciitis (PF) is one of the most common causes of foot pain in adults. It presents clinically as pain in the internal process of the calcaneal tuberosity, the proximal insertion point of the plantar fascia.1 Its highest incidence is in the population aged between 40 and 60, and in a third of cases it is even bilateral. It presents in sedentary people and marathon runners alike, and therefore 10% of the population will suffer the condition at some time in their lives.2,3 Although its aetiology is not completely clear, it is likely that not a single but various factors contribute to its onset, most notably, being female, overweight, frequent standing as well as sedentariness, and anatomical conditions such as the architecture of the foot (pes cavus, forefoot valgus, with low hallux mobility), contracture of the posterior muscle chain of the lower limb and atrophied plantar fat.4,5

PF is a musculoskeletal disorder with clinical symptoms of pain that is more intense when starting to walk in the mornings or after a period of rest, and increases with prolonged standing or with high-impact activities.6

Diagnosis is made by clinical history and physical examination, and confirmed by ultrasound, which rules out micro-tears, and determines the thickness of the fascia. The diagnostic criterion is a thickness >4mm. Ultrasound and MRI are the first and second-line modalities respectively for diagnosing PF.7

Treatment of PF includes a change of lifestyle. Oral analgesics and NSAIDs, fascial stretching exercises, massages and local cold compressions constitute the first-line treatment. If there is no improvement with this first approach, rehabilitation should be considered: physiotherapy (eccentric stretching, myofascial massage, electrotherapy), plantar orthoses or local corticosteroid injections, PRP,8,9 or botulinum toxin.10,11

Extracorporeal shock wave therapy (SWT) is a treatment proposal that has recently been demonstrated as safe and effective. It is useful for patients with chronic plantar fasciitis (CPF) refractory to the abovementioned treatments.12–14 With the increasingly widespread use of ultrasound, locating the transducer application point in SWT is becoming more accurate.

This study presents the results recorded after one year of using piezoelectric focal waves to treat PF, with ultrasound support, in patients in our rehabilitation department.

With the favourable report of our hospital's clinical research ethics committee (Favourable Report of the Biomedical Research Project, C.P.-C.I. 17/327-E), we performed an analytical quasi-experimental study, for which we selected a non-randomised sample of 90 patients from June 2015 to July 2017.

All the patients, before they were treated with shock wave therapy, were duly informed of the objectives of the treatment, and its possible complications and advantages over other therapeutic options. All of the patients signed their informed consent.

Ninety patients were treated, 57 women and 33 men, with a mean age of 52 years. The mean length of time with the condition was 16 months. Fig. 1 specifies the characteristics of our sample with regard to the risk factors for developing PF and lifestyle habits. The principle variable is improvement of pain according to VAS score, and the following variables were analysed secondarily: presence or otherwise of calcaneal spur, having undergone physiotherapy beforehand, having undergone corticosteroid injection in the 3 previous months, prior use of custom-made plantar ortheses or heel pads, routinely practising high-impact sports or high-impact work, limited joint balance in the ankle (dorsi and plantar flexion tests), body mass index greater or less than 30, and in active employment or otherwise. No statistically significant relationship was found for any of these variables with greater or less reduction in pain intensity (VAS) (p>.05). Neither was a relationship found in an increase or reduction of pain (VAS) with the intensity of the energy used during the technique (p>.05). The effect was not analysed of the plantar ortheses prescription (3 months after the treatment) on the results obtained on the VAS at 6 months, but how it might have influenced a greater or lesser reduction of the VAS score before the review at 3 months following the treatment was analysed; this relationship was not statistically significant (p>.05).

Figure 1.

Risk factors and lifestyle habits in the sample.

(0.14MB).

With regard to the VAS score results, the patients of our sample started with a mean value of 3.5 (95%CI: 3.93–3.07) at rest, and 8.6 (95%CI: 8.86–8.34) as the maximum pain on weight bearing during the day. The means at 6 months following the treatment were 1.6 (95%CI: 2.09–1.11) at rest, and 3.1 (95%CI: 3.65–2.55) as the maximum pain on weight bearing during the day, respectively. On comparing the VAS values at rest and the maximum pain on weight bearing during the day between the 3 treatment sessions, and after 3 and 6 months following the SWT, a statistically significant improvement was see in all the scores (p<.05) (Fig. 2).

Figure 2.

Differences in mean VAS score (during activity and at rest) between the first session, successive sessions, and the follow-up at 3 and 6 months. From the bottom upwards it can be appreciated how the difference between the mean VAS scores increase, with a slight reduction at the 6-month follow-up.

(0.06MB).

According to the Roles and Maudsley scale, at 3 months, 36% of the patients reported that the treatment result was excellent; 33.7%, that it was good; 19.1% rated it as fair, and 11.2% of the sample considered it poor. The figures were similar at 6 months: 37.7% with an excellent result; 31.2%, good; 19.5%, fair, and 11.7%, poor. Eleven of the patients were lost to follow-up at the 6-month follow-up.

With this treatment, no adverse effects or complications were recorded using the technique in any of the cases.

In this analytical paper we present our experience with SWT with a piezoelectric generator: there are very few studies that have used this type of generator.

Numerous studies have examined the different treatment alternatives for PF.16–20 This is a very common condition with multiple risk factors, and therefore, in many cases, these therapeutic options are not effective.

PF is a self-limiting musculoskeletal disorder, since in 80%–90% of cases the symptoms will disappear within 10 months. However this time interval is frustrating for both the patients who suffer the condition, and for the specialist treating them. Therefore, the sooner the condition is diagnosed and treatment started, the better the likelihood of a cure.

In their systematic review on the effectiveness of the different conservative treatments (orthopaedic, physiotherapy – bandages, stretches-, electrotherapy-ultrasound, shock waves, iontophoresis, laser and magnetotherapy- and acupuncture), Díaz López and Guzmán Carrasco21 studied 32 articles, in which stretching and shock waves were the techniques used most frequently, although the best results were obtained by combining various techniques. Shock waves were effective when other techniques had failed.

The gold standard treatment for PF is conservative. The physical therapies used in our different studies were demonstrated as effective, to varying extents, in reducing pain or alleviating the symptoms of PF. Surgery is not usually resorted to as first-line treatment because it does not always give good results, and there is recurrence in 30% of cases.

Focal SWT has been proposed as an option for the treatment of PF, in addition to other musculoskeletal conditions. Wang et al., in a review published in 2012,22 conclude with regard to extracorporeal SWT for PF that, since there are so many confusing factors that influence the effects of the results of this therapy, the results obtained could be controversial. However the large majority of the studies reviewed are in favour of extracorporeal SWT, with a success rate ranging from 34% to 88%.

There is no consensus regarding the density of energy applied or the treatment parameters. In a meta-analysis, Dizon et al.23 reviewed various studies and analysed the results in terms of pain and function according to the intensity of the energy applied, and observed, in addition, the adverse events recorded in each. They concluded that shock waves at moderate and high frequency are effective in reducing pain and in improving function for CPF and, although the treatment could cause pain, it was well tolerated by the patients and of short duration. In terms of protocol, Rompe et al.24 propose 3 weekly sessions of 1000 pulses at low energy as effective therapy. However, in one of their papers Wang et al.25 gave one single treatment and reported good results up to 72 months afterwards.

There are 3 ways of generating the focal shock wave, with an electrohydraulic, electromagnetic or piezoelectric generator. The latter has high intensity focus, but this focus is the smallest of the 3, therefore the total energy is less. It has the advantage of being less painful and better tolerated by the patient.

In the study by Liang26 (piezoelectric device), 2 patient groups with PF were randomly treated: one received shock waves at high intensity (.56mJ/mm2) and the other at low intensity (.12mJ/mm2). They obtained similar results in improved pain and function with both high and low intensity, and although less pain was associated with high intensity, it did not provide more favourable success rates, which went from 67% at 3 months to 58% at the 6-month follow-up.

In our study, when the differences in the mean VAS scores between the first treatment session and the subsequent sessions were analysed, and with the post-treatment follow-ups at 3 and at 6 months, we can observe how the difference between the mean VAS scores increases, with a slight decrease at 6 months.

Comparing the mean VAS scores (maximum pain on weight-bearing during the day and at rest) reported by the patients between the first and the successive sessions (second-third), and later with the post-treatment scores at 3 and at 6 months, an increase in the differences of these values can be appreciated over time, which translates into improved pain for the patient, maintained medium and long term, according to the results of our study. The loss to follow up of 11 patients might have influenced this slight reduction at 6 months.

In their meta-analysis, Sun et al.27 compare the efficacy of extracorporeal shock waves in general, focal shock waves and radial shock waves with a placebo to assess their effectiveness for chronic PF. They conclude that focal shock wave therapy can alleviate pain in chronic PF as an ideal alternative option; whereas they cannot reach firm conclusions on the general effectiveness of shock waves or radial shock waves. Due to the variations in the studies included in this meta-analysis, additional trials are required to validate these conclusions.

There are few studies that analyse the efficacy of shock waves for PF with a piezoelectric-type device, therefore it would be interesting to establish which shock wave generator might be most effective, and whether less total energy density in the focus, as with the piezoelectric generator, influences the efficacy of this treatment.

The main limitations of this study are that we could not quantify whether or not the patients made changes to their lifestyle habits, which could mean that the favourable results obtained were influenced by these changes, by the natural evolution of the condition or by the use of custom-made plantar orthoses, and not due the use of extracorporeal SWT alone. It would be interesting to undertake a comparative study of the efficacy and tolerance of this treatment compared to plantar fascia injections or with a control group, which this study lacked. To that end, future studies are necessary to clarify the most effective solutions for treating PF.

Another limitation of this paper is that we did not study the number of patients who might have had morphological alterations of the foot, and what these were. We only recorded whether or not they wore an insole before the treatment, and therefore we did not study whether this factor might be linked to the results obtained on the VAS scale. This could also be another future line of research.

According to the results obtained in our study, focal piezoelectric SWT applied at high energy intensity reduces the pain of PF from the first session, improving and maintaining this result even at 6 months following the treatment, an improvement which is statistically significant. Similarly, the great majority of the patients treated considered that they had achieved a positive result with this therapy (Roles and Maudsley scale), and were satisfied.

Focal piezoelectric SWT is an effective therapeutic alternative for the resolution of PF for patients with the condition. It is safe because there are no recorded complications and very well tolerated compared to other interventionist techniques. Professionals working in the field of musculoskeletal entities should be aware of and consider using the treatment.

Level of evidence I.

The authors have no conflicts of interest to declare.