A Literature Review done for my Masters in Sports Medicine (MsSpMed), University of Queensland, Australia 2017

Introduction

Heel pain is a common complaint heard in the physician’s room and plantar fasciitis has been found to be the most common culprit, contributing to 15% of all foot complaints2,19 . It is also a very common injury among runners, with 12.7% of them9 suffering from it at certain points in their career.

The classic history of plantar fasciitis is that of excruciating pain felt at the heel or bottom of the foot on the first step each morning. This pain subsequently subsides with activity throughout the day. In severe cases, the pain may be felt on weightbearing activities throughout the day.

Its aetiology has been found to be multi-factorial, involving both intrinsic and extrinsic factors. Intrinsic factors include high body mass index, tight gastrocnemius-soleus complex14 and weak hip abductors10. The myriad of extrinsic factors which may cause this condition include choice of shoes, type of sport and even training methodologies.

Plantar fasciitis is a self limiting condition that resolves spontaneously with time13, with 80 percent of patients experiencing resolution of symptoms within 12 months19.  Thus, the goal of Sports Medicine is to provide treatment in an effective, time-efficient manner that allows patients to return to their activities as soon as possible. Plantar fasciitis has conventionally been treated conservatively, such as with the use of analgesia, plantar fascia-specific stretching, orthotics, corticosteroid injections and physiotherapy.

It was only in 1995 when the use of Extracorporeal Shock Wave Therapy (ESWT), Focused ESWT in particular, was first reported to be used in the treatment of plantar fasciitis, together with other musculoskeletal conditions such as lateral epicondylitis. During its infancy, this technology was used under local anaesthesia over a small targeted area of 0.5-1.0 cm in diameter which is localised under fluoroscopy and later by ultrasound. Two recent meta-analyses16,17 reported ESWT as an effective treatment of chronic plantar fasciitis and it is not uncommon to see ESWT being recommended to patients who have failed conservative treatment in Sports Medicine clinics today.

In 2001, Radial Extracorporeal Shock Wave Therapy (RSWT) was introduced in the treatment of musculoskeletal conditions. The key difference is that RSWT has a longer rise time (50μsec vs 0.01μsec), pulse duration (200-2000μsec vs 0.3μsec), lower peak pressure (0.1-1MPa vs up to 120MPa) and smaller depth of penetration (0-3cm vs up to 12cm)3. In addition, its focal point of energy is on the tip of the applicator with radial emission in the tissues11,12, unlike ESWT which is focused to the target zone. These differences results in several advantages of using RSWT including ease of application, no need for ultrasound guidance, as well as a smaller risk of adverse effects3. On top of that, the cost of RSWT is also much lower than ESWT.

This literature review aims to evaluate the effectiveness of  RSWT as a treatment modality for plantar fasciitis.

Results

A literature search was done on PubMed and of the eight studies identified from the literature research, two of them were RCTs involving sham designs while five others compared RSWT to other treatment modalities. One of them was a observational study with no comparisons to any other modalities. The details of each study are summarized in Table 1.

Discussion

Outcome Measurements

The study by Gerdesmeyer et al.1 is a double blinded randomised controlled trial involving 245 patients for the Food and Drug Administration of the United States. It has a robust study design that compares RSWT with a sham treatment that is not distinguishable by the patient, thus effectively removing the placebo effect. The study by Ibrahim et al.2 also has a similar study design.  However, both studies have limitations in the area of outcome measurements.

There is no consensus on the ideal instrument which should be used for outcome measurement. Outcome evaluation following RSWT has frequently been based on subjective findings such as the Visual Analogue Scores to measure pain levels,  standardised questionnaires such as the Short Form (36) Health Survey (SF-36), Roles-Maudsley Score (RMS) and the Foot Function Index9. Subjectivity is inevitable among individuals in the use of these scores and as such can affect the reliability of results. Lohrer et al9. attempted to get around this limitation by introducing objective neuromuscular performance assessments on the patients. However, these tests are strongly limited by the patient’s motivation and abilities. In addition, these tests include complex movements such as single leg long jump and single leg drop jumps which may be too challenging for some.

One possible objective measure could be the use of ultrasound to measure the plantar fascia thickness. It has been shown that a thinner plantar fascia can predict less pain for the patient post-treatment9,18. A recent systemic review on the application of ultrasound in the assessment of plantar fascia in patients with plantar fasciitis found that it can provide reliable imaging needs for the monitoring of intervention effectiveness20.

Use of rescue medications during trials

Another weakness in study design that is present in all of these studies is the lack of standardisation in the use of rescue medications. Two studies4,7 allowed patients to use any analgesia of their choice, another two 5,6 provided diclofenac while one provided acetaminophen1 for patient’s use.  Some studies did not mention indicate whether rescue medications2,3,9 were used. Despite the allowance of analgesia, none of the studies attempted to avoid the confounding effects of the rescue medications. Only one study2 prohibited the use of other conservative treatment such as analgesia during the entire period of the trial.

The use of rescue medications is well discussed in scientific trials involving osteoarthritis and it is recognised that their use can alleviate and reduce symptoms in patients and thus bias the difference between the placebo and active treatment group, with the US FDA attempting to publish guidelines to standardise this among research trials15.

Similarly, with the ability of analgesia to mask the true extent of pain of plantar fasciitis that the patients are experiencing during follow-up evaluations, and with no standardised protocol in place, there is a chance that the results can be affected. Perhaps one way of standardisation is to enforce a period of no analgesia for  a fixed duration before each follow up. In addition, there are also several methods of analysis which can take into account the use of rescue medications to provide a more meaningful comparison of randomized interventions21.

Comparing to Physiotherapy

It is logical to compare physiotherapy, which is a common treatment modality used in plantar fasciitis, with RSWT alone. 2 studies4,7 did so and showed that in both the short and long term, there is no difference between conventional physiotherapy and RSWT in the outcome of plantar fasciitis. However, more can be done to the both study designs to allow fairer comparisons. In both studies, the physiotherapy arm involved a strict protocol which involved ultrasound at a standard frequency and intensity, stretching of the posterior leg muscles, tibialis anterior strengthening and home exercises4,7. However, in reality, treatment instituted by a physiotherapist is highly dependant on his or her assessment of the patient and can differ from patient to patient.  For example, it has been found that patients with plantar fasciitis may have weakness of the hip abductors10. As such, if treatment does not address the hip abductor weakness, but instead follow a rigid protocol of US and lower limb stretching, their recovery may be affected. Therefore, removing the physiotherapist’s professional assessment of the patients’ needs may render the treatment ineffective.

Perhaps, another method would be to create a more holistic protocol with a team of physiotherapists which allows for specific treatment plans to be instituted for common biomechanical deficiencies so that patients get targetted, individualised treatments.

RSWT in the treatment of acute Plantar Fasciitis

Shock wave therapy in general has been found to be effective in the treatment of chronic plantar fasciitis5. This is hypothesised to be due to its ability to initiate healing through the enhancement of cell proliferation and changes to mRNA expression for collagen I and III5 during the presence of a failed healing response.

Only one study5 investigated its effectiveness in the acute setting, comparing it to plantar fascia specific stretching. Interestingly, there is a significant difference at 2 and 4 months with stretching found to be superior to RSWT. However by 15 months, there is no difference between both groups. This is likely due to the fact that a failed healing response is not yet present and thus there is no role for RSWT5.

These results suggest that RSWT should not be used in the initial treatment of acute plantar fasciitis.

Adverse Effects

A positive finding of these studies is that there are no reported significant adverse effects found in the use of RSWT for the treatment for RSWT. In the large multi-center randomised controlled trial done over 3 study centers in the United States and 5 study centers in Europe, involving 254 participants for the Food and Drug Administration (FDA) did not find any adverse effects with regards to tendon rupture, Monofilament assessment and toe clawing observation for neurological damage and Ankle-Brachial assessment for vascular damage1.

Recommendations

Technique of Application

Several of the studies described different techniques with applying RSWT to the patient. One of them is to locate the tip of the applicator to the most tender point by the medial calcaneal tubercle, adjusting based on patient-controlled feedback1. In the study by Ilieva et al.3, the technique involved having 500 shockwaves of 10Hz along the insertion of the plantar fascia at the maximum point of pain, 1000 shock waves of 10Hz on the most painful points, 500 shockwaves along the plantar fascia and finally 500 shockwaves of 15Hz on the insertion of the plantar fascia.

With so many variables such as pressure, frequency, total number of impulses and direction of the shock wave, it is possible that they may lead to different results in the treatment of plantar fasciitis. More research is required in this area to determine the optimum settings for the treatment of plantar fasciitis.

RSWT vs Focused ESWT in the treatment of Plantar Fasciitis

It is of the Sports Physician’s interest to know if RSWT, with its advantages of ease of use and lower costs, can yield effective results like its older, more established cousin, ESWT. The study by Lohrer et al.9, found ESWT to be slightly superior to RSWT. However, in a meta-analysis8, it was found that best treatment success was found in the use of RSWT as compared to ESWT however, the results are limited by the small number (only 2) of RCTs done for RSWT. Hence, the evidence is still conflicting.

Due to the economic superiority of RSWT to ESWT, more RCTs should be done to prove its effectiveness in the treatment of plantar fasciitis.

Conclusion

Despite two double blinded randomized controlled trials and the numerous studies comparing RSWT and other treatment modalities, there were several limitations to the study designs as discussed that limits our interpretation and generalisation of the results. Thus, it can only be concluded that RSWT shows promising potential to be a cost effective treatment modality for chronic plantar fasciitis.

In my practice, I will still utilise the conventional approach of a holistic, multidisciplinary management which also involves treating the patient’s risk factors. I will reserve RSWT for patients suffering from chronic plantar fasciitis who have exhausted all treatment modalities as a cost effective option. When instituting RSWT, it will be crucial to enforce and continue other conventional treatment modalities such as plantar fascia specific stretching on a regular basis.

References

1. Gerdesmeyer L, Frey C, Vester J, Maier M, Weil L Jr, Weil L Sr, et al. Radial shock wave therapy is safe and effective in the treatment of chronic recalcitrant plantar fasciitis. Am J Sports Med. 2008; 36(11):2100-9
2. Ibrahim MI, Donatelli RA, Schmitz C, et al. Chronic plantar fasciitis treated with two sessions of radial extracorporeal shock wave therapy. Foot Ankle Int 2010; 31(5):391-7
3. Ilieva EM, Minchev R, Gonkova M. Radial shock wave therapy in patients with plantar fasciitis: One-year follow-up study. Annals of Physical and Rehabilitation Medicine. 2014;57:e325-e326.
4. Greve, D’Andréa JM, Vinicius M, Roberto P. Comparison of radial shockwaves and conventional physiotherapy for treating plantar fasciitis. Clinics. 64(2):97.
5. Rompe JD, Cacchio A, Weil L Jr, Furia JP, et al. Plantar fascia-specific stretching versus radial shock-wave therapy as initial treatment of plantar fasciopathy. J Bone Joint Surg Am. 2010; 3;92(15):2514-22
6. Rompe JD, Furia J, Cacchio A, Schmitz C, Maffulli N. Radial shock wave treatment alone is less efficient than radial shock wave treatment combined with tissue-specific plantar fascia-stretching in patients with chronic plantar heel pain. International Journal of Surgery. 2015.
7. Grecco MV, Brech GC, Greve JM. One-year treatment follow-up of plantar fasciitis: radial shockwaves vs conventional physiotherapy. Clinics (Sao Paulo) 2013;68(8):1089-95
8. Chank KV, Chen SY, Chen WS, et al. Comparative effectiveness of focused shock wave therapy of different intensity levels and radial shock wave therapy for treating plantar fasciitis: a systemic review and network meta-analysis. Arch Phys Med Rehabil 2012;93(7):1259-68
9. Lohrer H, Nauck T, Dorn-Lange NV, Schöll J, Vester JC. Comparison of Radial Versus Focused Extracorporeal Shock Waves in Plantar Fasciitis Using Functional Measures. Foot & Ankle International. 2010;31(01):1-9.
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13. Victor R. Prisk Commentary on an article by J.D Rompe MD, et a.: “Plantar Fascia-Specific Stretching versus Radial Shock-Wave Therapy as Initial Treatment of Plantar Fasciopathy”. J Bone Joint Surg Am Anov 2010, 92(15)e26
14. League AC. Current Concepts Review: Plantar Fasciitis. Foot Ankle Int. 2008; 29:358-66
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17. Dizon JNC, Gonzalez-Suarez C, Zamora MTG, Gambito EDV. Effectiveness of Extracorporeal Shock Wave Therapy in Chronic Plantar Fasciitis. American Journal of Physical Medicine & Rehabilitation. 2013;92(7):606-620.
18. Liang H-W, Wang T-G, Chen W-S, Hou S-M. Thinner Plantar Fascia Predicts Decreased Pain After Extracorporeal Shock Wave Therapy. Clinical Orthopaedics and Related Research. 2007;PAP.
19. Buchbinder R. Plantar Fasciitis. New England Journal of Medicine. 2004;350(21):2159-2166.
20. Mohseni-Bandpei MA, Nakhaee M, Mousavi ME, Shakourirad A, Safari MR, Vahab Kashani R. Application of Ultrasound in the Assessment of Plantar Fascia in Patients With Plantar Fasciitis: A Systematic Review. Ultrasound in Medicine & Biology. 2014;40(8):1737-1754.
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