EXTRACORPOREAL SHOCK WAVE THERAPY IN SPORTS MEDICINE. Review paper: Dr Ivor Berman

Introduction: Extracorporeal shock wave therapy (ESWT) is a non-invasive form of therapy which has been shown

to be effective in treating certain musculoskeletal conditions including non – union of long bones,

calcific tendinosis, lateral epicondylitis at the elbow, plantar fasciitis and Achilles tendinitis. Slowly,

more uses have been found. ESWT is widely used as it is non-invasive, enables fast recovery and

without the necessity to restrict weight-bearing or limit mobilisation.

Most frequent use of ESWT is in the treatment of plantar fasciitis and mid to late stage

tendinopathies

This article aims to give an overview of ESWT with respect to its mechanism of action and current clinical applications.

Physics and Biology of ESWT

A shockwave (Fig1, 2) is an intense, but very short energy wave traveling faster than the speed of sound. The word "extra-corporeal" means "outside the body" and refers to the fact that the shockwaves are generated outside the body.

Like an ordinary wave, it carries energy and can propagate through a medium (solid, liquid or gas). Shock waves are characterized by an abrupt, nearly discontinuous change in the characteristics of the medium. Across a shock there is always an extremely rapid rise in pressure, temperature and density of the flow (1). Shock waves differ from sound waves in that the wave front, in which compression takes place, is a region of sudden and violent change in stress, density, and temperature. Because of this, shock waves propagate in a manner different from that of ordinary acoustic waves. In particular, shock waves travel faster than sound, and their speed increases as the amplitude is raised; but the intensity of a shock wave also decreases faster than does that of a sound wave, because some of the energy of the shock wave is expended to heat the medium in which it travels (2) Extracorporeal Shock Wave Therapy (ESWT), is a technology using shockwaves to treat chronic, painful conditions of the musculoskeletal system.

The technique of using shockwaves to break up kidney stones has been around for a nearly a quarter century. In the process of treating patients, it was found that many people undergoing the procedure had improvement in varied musculoskeletal causes of pain. It was at this point that scientists began to investigate whether shockwaves may have an effect to heal other areas.

Specialized machines were then developed with this being the origin of ESWT. The type of shockwave therapy we now use, is specialized to specifically help treat musculoskeletal conditions.

Physics of shock wave therapy / Mechanism of action:

Fig1. Typical form of a therapeutic shock wave (3)

Fig2: Typical form of a therapeutic shock wave used in pain management (4)

A shock wave (Fig 1, 2) is a sonic pulse that has certain physical characteristics. There is a high peak pressure (Fig 3), sometimes more than 100 MPa (500 bar), but more often approximately 50 to 80 MPa, a fast initial rise in pressure during a period of less than 10 ns, a low tensile (Fig.4) amplitude (up to 10 MPa), a short life cycle of approximately 10 µs, and a broad frequency spectrum, typically in the range of 16 Hz to 20 MHz (5, 6)

The tensile forces produced by the negative phase lead to transition of water molecules into cavitation bubbles (Fig. 4) which, as they expand are immediately compressed. This leads to an increase in the temperature of the gas contained in the bubble until it implodes, generating spherical shockwaves and vapour micro jets called “jet streams”(7). This energy induces modification to the cell membrane and functional changes in the cytoplasm organelles, which ultimately stimulate the nucleus. Consequently the production of proteins, nitric oxide and specific growth factors contribute to activation of the biological processes (8, 9).

(Fig: 3) Pressure component (11) (Fig: 4) Tensile component, with cavitation (11) Small bubbles (black dots) represents the cavitation.

Dr Ching-Jen Wang etal in 2006 (Fig 5), in a paper, described the proposed biological responses to shock-wave therapy. They proposed that the shockwave therapy induced antigenic growth indicators include: bone morphological protein (BMP), endothelial nitic oxide synthase (eNOS), vessel endothelial growth factor (VEGF) and proliferating cell nuclear antigen (PCNA). These factors improve the blood supply/ neovascularization and tissue regeneration within tendon and bone (12).

Fig: 5. A proposed cascade of biological mechanism of extracorporeal shock waves in musculoskeletal tissues. In addition to the healing properties shockwaves also relieve pain. There is discomfort during treatment, but usually pain reduction immediately post treatment, and then over the next 24 – 72 hours. After each treatment the pain relief period lengthens. Mechanisms involved are thought to include hyper-stimulation analgesia, release of substance P from the treated region leading to the immediate and subsequent lasting relief from pain and the cessation of substance P induced neurogenic inflammations (13-17). Bioeffects of shock waves on nervous tissue appear to result from cavitation. It is suggested that cavitation is also the underlying mechanism of shock wave-related pain during ESWT in clinical medicine (10). Overall the method of action is thought to relate to inciting hyperaemia, neovascularity and growth

factors leading to healing as well as the inhibition of pain perception (16).

There are several manufacturers and types of shockwave therapy available in the clinical sphere. A typical shock wave therapy device and one through which many studies have been performed is the Swiss Dolorclast system (Fig 6). In this device air is used to fire a projectile within a guiding tube that strikes a metal applicator placed on the skin. The projectile generates stress waves in the applicator that transmit pressure waves into tissue. This is provided to the clinician in the form of a handpiece attached to an air compression system (11).

Fig: 6. Swiss Dolorclast Extracorporeal Shock Wave System Handpiece

Contraindications of ESWT

Children (pre-puberty), pregnancy, infection, focal hot inflammation, steroid injection in the prior 6 weeks, neoplasm, patients with clotting disorders or on anticoagulants, cardiac pacemaker, and air filled cavities/tissue such as lung/bowel (11).

Complications of ESWT.

Schmitz et al in 2015 (18) reviewed the Pedro database to assess the efficacy and safety of ESWT.

They found that the safety of ESWT was clearly supported by the cumulative data. There were no

reports of serious adverse events in any of the studies included in this analysis. Focal issues are

uncommon and relate to local bruising and swelling. No systemic effects were found.

Therapeutic Uses of Extracorporeal Shock Wave Therapy

Plantar Fasciitis

There is considerable controversy regarding its effectiveness (19), however a review article by Yin

MC et al (20), which identified 108 potentially relevant articles, of which seven studies with 550

participants met inclusion criteria was examined, demonstrated substantive evidence that low

intensity ESWT is of benefit.

In support of this therapy, Malliaropoulos N, et al (21) treated 68 patients with plantar fasciopathy,

demonstrating significant improvement in discomfort, with a 98% success rate with significant pain

reduction at one year. Their one year recurrence rate was 8%.

Ibrahim M, et al (22) performed a study where a total of 50 patients with unilateral, chronic PF were

randomly assigned to either ESWT or placebo treatment. Each group 25 patients. ESWT was applied

in two sessions 1 week apart. Endpoints were changes in the Visual Analog Scale (VAS) score and the

modified Roles & Maudsley (RM) score from baseline to 4 weeks, 12 weeks and 24 weeks follow-up.

Statistical analysis in this study demonstrated that ESWT resulted in significantly reduced mean VAS

scores and mean RM scores at all follow-up intervals compared to placebo treatment.

Gluteal Tendons

There are very few studies looking at the effectiveness of ESWT in the treatment of gluteus medius

and minimus insertional tendinosis.

Two studies performed in 2009 by Rompe etal (23) and Furia etal (24) suggested that SWT was of

value as 64% and 76% of patients respectively were able to return to normal physical activity.

Rompe et al (23), separated patients into separate groups including home training, local

corticosteroid injection, or radial shock wave therapy for greater trochanteric pain syndrome. They

found the difference in pain and recovery at 1 month and 15 months of follow-up was not

statistically significant when comparing SWT with the home training group.

Furia et al (24), demonstrated that SWT was superior to the traditional therapy used in the control

group. Traditional therapy in the control group included traditional therapies including rest, anti-

inflammatory medications, ice, gluteal and tensa fascia lata muscle stretching and strengthening,

iontophoresis and corticosteroid injections.

Calcific Tendinitis of the Shoulder

Hsu et al ( 25) in 2008, in a study of 46 patients ( 33 patients treated with shock wave therapy and 13

receiving sham treatment) demonstrated significantly better results when measured on the

Constant-Murley score (CMS) which looks at pain, range of motion, activity and strength. Reduction

of calcium deposits was significantly better in those treated. Assessment of this was per Gartner

classification. Gartner Type 1: clearly circumscribed and dense, formative, Type 2: clearly

circumscribed, translucent, cloudy and dense, Type 3: Cloudy and translucent, resorptive (26).There

were no significant adverse effects with treatment.

Gerdesmeyer et al (27) in 2003 published the largest study. 144 patients in total were allocated to either shock wave therapy or placebo treatment in a randomized, double-blinded study. Patient’s results were measured on the CMS. In addition, radiographs were performed at 3, 6, and 12 months. 10 patients were lost to follow-up. Significant improvements were seen compared to the sham treatment 6 months after treatment. The improvement was shown across all endpoints, namely 3, 6, 12 and 24 months.

Wang et al (28) also in 2003 demonstrated similar results in a similar study with 33 patients receiving SWT and 6 patients included in the control group. (The rest of the sham group dropped out once they found they were not having treatment). The CMS and pain on the VAS (Visual analogue Score) were recorded at 2 and 4 weeks, 3, 6, and 12 months, and yearly thereafter. Those treated showing improvement across all end points.

Lateral Epicondylitis

There are several papers looking at the effectiveness of SWT in the management of lateral epicondylitis (tennis elbow).Outcomes variable.

Capan N et al (29) in 2016 performed a double-blind, randomized, placebo-controlled trial where 56 patients were randomised to ESWT or sham treatment. Each group 28 patients. Once a week for three weeks 2000 pulses of 10 Hz frequency at a 1.8 bar of air pressure was administered.

Patients were assessed at baseline and at 1 and 3 months after treatment for the amount of pain and degree function. Grip strength of the affected extremity was also measured using a hand dynamometer. They found that both groups demonstrated improvement over the timeframe, however there was no significant difference between the two groups. The conclusion was that ESWT does not appear to be more effective in reducing pain or improving function or grip strength when compared to sham treatment. A potential reason for the treatment not being effective was the relatively low air pressure administered during treatment

Other studies, however, have shown shock-wave therapy to be effective.

Caruli C et al (30) in 2016 a study of 80 subjects demonstrated positive outcomes. Each patient had 3 applications with a monthly interval, and was followed up at 1, 6, and 12 months after treatment. Results were evaluated by the numeric rating scale (NRS) and the Oxford Elbow Score. There was statistical improvement in symptomatology at one year post treatment, with almost complete resolution of symptoms.

Trentini R et al (31) in 2015. Treated 36 patients, with a mean follow-up time of 24.8 months. Focal

ESWT was administered weekly for 3–4 week. They found a positive response in 75.7% of patients

post treatment.

Patella Tendinosis

Furia, J.P et al (32) in 2013, in their study divided 66 patients into two equal groups. First group treated with ESWT and the second group other forms of non-operative therapy. Patients followed up over 12 months. Evaluation was by change in Visual Analogue Scale (VAS), Victoria Institute of Sport Assessment score for patellar tendinopathy (VISA-P) score and by Roles and Maudsley Score. They found a statically significant degree of improvement in those treated with ESWT at 1 year. Van der Worp H, Zwerver J, et al (33) in 2014 compared the effectiveness of focused shockwave therapy (FSWT) and radial shockwave therapy (RSWT) for treating patellar tendinopathy in 43 patients. Although this study compared two different forms of therapy the outcomes demonstrated significant improvement in symptomatology with both forms of shock wave therapy. Outcomes similar for both.

Achilles Tendinosis

Rompe JD, Nafe B et al (34) in 2007 compared the effectiveness of 3 management strategies-group 1, eccentric loading; group 2, repetitive low-energy shock-wave therapy (ESWT); and group 3, wait and see-in patients with chronic tendinopathy of the main body of tendo Achilles. Seventy-five patients with a chronic recalcitrant (>6 months) non insertional Achilles tendinopathy were enrolled in a randomized controlled study. At 4-month follow-up, eccentric loading and ESWT showed comparable results. The wait-and-see strategy was shown to be ineffective.

Rompe JD, Fauria J and Manfully N (35) in 2009 compared the effectiveness of eccentric loading vs eccentric loading plus repetitive low-energy shock-wave therapy. Sixty-eight patients with chronic recalcitrant (>6 months) non insertional Achilles tendinopathy were enrolled in a randomized controlled study. At 4-month follow-up, eccentric loading alone was less effective when compared with a combination of eccentric loading and repetitive low-energy shock-wave treatment.

Rompe JD , Furia J, Maffulli N (36) in 2008 compared eccentric loading compared with shock wave treatment for chronic insertional Achilles tendinopathy. Fifty patients with chronic (>6 months) recalcitrant insertional Achilles tendinopathy were enrolled in a randomized, controlled study. This study showed that eccentric loading had inferior results to ESWT at four months of follow-up. Notarnicola, A., Maccagnano, G., Tafuri, S. et al.(37) in 2014 compared cold air and High Energy Laser Therapy (CHELT) vs ESWT in the treatment of Achilles tendinopathy. 60 subjects affected by insertional Achilles tendinopathy were enrolled and randomized into two equal groups. Both groups of participants performed stretching and eccentric exercises over a 2-month period. The visual analogue scale (VAS), the Ankle–Hindfoot Scale, and the Roles and Maudsley Score were measured before treatment, at end of the treatment session and at 6 months. Both groups, were found to have a statistically significant improvement at the 6 month review.

Bone Non-union

The treatment for chronic fracture non-union is internal fixation. Over the past few years research is

showing evidence that ESWT can be used as an alternative treatment option.

Cacchio A et al (38) in 2009 showed that ESWT is as effective as surgery in stimulating union of long bone non-union, yielding better short term clinical outcomes. They randomly assigned 126 patients with a long bone non-union to receive either extracorporeal shock-wave therapy or surgical treatment. The patients in the shock-wave groups received four treatments. The patients in the groups had similar demographic characteristics, durations of non-union, and durations of follow-up. Radiographic and clinical results were determined before and three, six, twelve, and twenty-four months after treatment. At six months, 70% of the nonunions having shock wave therapy and 73% of the nonunions undergoing surgery had healed. At three and six months after treatment, the clinical outcomes in the two shock-wave groups were significantly better than those in the surgical group. At twelve and twenty-four months after treatment, there were no differences among the groups. Furia J, Juliano, P et al (39) in 2010 in a similar study also found that ESWT to be as effective as surgery in the treatment of chronic fracture nonunion in the metaphyseal-diaphyseal region of the fifth metatarsal. Twenty-three patients received ESWT and twenty patients were treated with intramedullary screw fixation. Twenty of the twenty-three nonunions in the shock wave group and eighteen of the twenty nonunions in the screw fixation group were healed at three months after treatment. One of the three nonunions that had not healed by three months in the shock wave group was healed by six months In 2010, Zelle B, Gollwitzer H et al (40) did a review of the literature from 1966 to 2008. 924 patients undergoing ESWT for delayed union/nonunion were extracted from 10 studies. The overall union rate was 76% (95% confidence interval 73%-79%).

Pre and in-Competition and Acute Phase Tendinosis

Usually and historically ESWT has been used in chronic tendinopathies (>6 months duration).

However, many elite sporting teams and athletes are now using ESWT pre and in competition for its

pain reduction effect; examples include Fiorentina in the Italian Serie A, many countries/athletes in

the last two Olympics, AFL and A league soccer teams.

In addition, over the last few years, ESWT has been trialled and used earlier in the management of

tendinopathy.

Some research is starting to emerge in the more acute setting. As an example of this Köksal İ, Güler

O et al (41) in 2015 evaluated and compared the results of ESWT in the treatment of acute (<3

months) and chronic (> 6 months) lateral epicondylitis. Fifty-four patients in total. Twenty-four

patients who had symptoms for <3 months were defined as the acute group and 30 patients who

had symptoms for >6 months were defined as the chronic group. All cases were evaluated pre

therapy and at weeks 2, 12, and 24 post therapy according to pain while resting, pain while

stretching, pain when pressed, pain while lifting chair, pain while working and night time pain. They

found that both groups demonstrated significant improvement across almost all values at each

evaluation time point compared to the baseline values. This demonstrating that ESWT may well be

equally effective in the treatment of acute and chronic lateral epicondylitis. In addition, the data

suggested that the progression from the acute phase to the chronic phase may be prevented by

treatment with ESWT.

Information sources and search strategy:

The databases of PubMed, PEDro database, Google Scholar, Web of Science, Cochrane Library, University of Queensland library and Monash Health library were searched without any date limits. First search addressed the terms shock wave, shock waves, shockwave, shockwaves and treatment. Second search was performed on the key terms: tendinosis, tendinitis, plantar fascia, plantar fasciitis, Achilles, patellar tendon, epicondylitis, calcification, bone, non-union, orthopaedic.

Conclusion:

Extracorporeal shock-wave (ESWT) is a useful adjunct in the management of patients with tendinosis

and those with bone non-union. It is effective, safe, and has the potential to replace surgery in

several orthopaedic pathologies.

This form of treatment has typically been utilised in patients who have chronic injuries not

responding to traditional means of therapy. Slowly ESWT is being used in the more acute setting and

during/pre competition.

Overall, ESWT appears to work best when an injury reaches the chronic, non-healing state. ESWT in both biologic studies and clinically appears to be able to jump start the healing process in chronic, non-healing injuries. Like all forms of therapy not everybody responds to every particular form of treatment, however ESWT appears to be a valuable treatment option which can be used in conjunction with other forms of therapy and which is non-invasive and readily available.

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