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The Role of Extracorporeal Shock Wave on Plantar Fasciitis
Foot Ankle Clin N Am 10 (2005) 699 – 712
The Role of Extracorporeal Shock Wave on Plantar Fasciitis Gregory J. Roehrig, MD, Judith Baumhauer, MD*, Benedict F. DiGiovanni, MD, Adolph S. Flemister, MD Department of Orthopaedics, University of Rochester, Strong Memorial Hospital, 601 Elmwood Avenue, Box 665, Rochester, NY 14642, USA
Shock waves are acoustic waves that are capable of transmitting mechanical energy through a medium. As with many physical and chemical principles, scientists have sought and found ways in which this phenomenon affects the human body. The concept that shock waves can be used to alter the material structure of an object is well-established; the classic example is the in vivo destruction of renal calculi. With such knowledge, the scientific and medical communities continue to research and develop therapeutic methods to better the quality of life. Recent focus has been on the role of shock wave treatment for certain foot and ankle musculoskeletal conditions, specifically chronic plantar fasciitis. As more investigators delve into the questions of indication, administration, and therapeutic effect, the interest and enthusiasm for this modality continue to grow.
Historical background The first observation of shock waves affecting the human body occurred during World War II. Capsized, drifting sailors were found to have damaged lung tissue after being exposed to nearby depth charges [1]. Subsequent experiments revealed that electrohydraulically generated shock waves were capable of
* Corresponding author. E-mail address: [email protected] (J. Baumhauer). 1083-7515/05/$ – see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.fcl.2005.06.002
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breaking underwater ceramic plates [2]. Years later, an experimenter mistakenly touched a target plate at the instant that a high-velocity projectile struck, causing an electric shock-like sensation throughout his body [3]. These findings prompted the German government to sponsor investigations into the consequences of shock waves on human tissue. They discovered that the energy transmitted from an external source (even from long distances) resulted in damage to internal organs, such as the brain and lung, but relative sparing of muscle, fat, connective tissue, and bone [1]. Around that time, German scientists began to speculate whether shock waves could be used to fragment renal calculi. In 1971, Haeusler and Kiefer [4] were the first to report successful in vitro disintegration of a kidney stone. As the practice of lithotripsy began to blossom, researchers wondered about its effects on the nearby bones. In 1986, Haupt not only determined an absence of negative effect on osseous tissue, but also showed that shock waves seemed to stimulate bone formation. By 1988, he reported the first successful treatment of a fracture nonunion with shock wave therapy [5]. The same success was achieved by Valchanov and Michailov [6]. The 1990s saw German physicians expand the existing indications and begin treating soft tissue conditions, such as calcific rotator cuff tendonitis, lateral epicondylitis, and plantar fasciitis [7–9]. These new approaches necessitated modification of the shock wave generators into a more user-friendly and efficient orthopedic treatment tool. In 1993, such a device became available [1]. The US Food and Drug Administration (FDA) recognized the potential of extracorporeal shock wave therapy (ESWT), and authorized its use for chronic plantar fasciitis in October 2000. The OssaTron (HealthTronics Inc., Marietta, Georgia) was the pioneer electrohydraulic device that was approved for use on adult patients with at least 6 months of symptoms that were refractory to conservative measures [10].
Basic science of extracorporeal shock wave therapy A shock wave is a transient pulse of pressure transmitted rapidly through a medium in three dimensions. Some of the physical properties of these waves include amplitude, frequency, and rise time. The amplitudes can exceed 100 MPa, the frequencies can range from audible to ultrasonic, and the rise times can be on the order of nanoseconds. The key to harnessing this explosion of energy for clinical benefit is to control and focus its effects [11]. To do so, the approved devices concentrate the shock waves into an area on the order of a few square millimeters. Therefore, a useful descriptive unit of ‘‘dosage’’ is mJ/mm2, termed energy flux density (EFD) [12]. Three principle methods by which clinically applicable shock waves are produced include electrohydraulic, electromagnetic, and piezoelectric. The electrohydraulic method was the first to be developed. A high-voltage discharge
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between the tips of an electrode bathed in water results in vaporization of, and explosion within, that water. A pressure wave is produced, which is focused by a reflector for accurate administration [11]. Electromagnetic devices create a shock wave by sending a strong electric current through a coil and creating a magnetic field. This field creates current flow and deformation in a metal membrane bathed in medium. The deformation results in compression of this medium and propagation of a shock wave [11]. The third mechanism involves piezoelectric crystals. More than 1000 of these crystals are mounted geometrically on the inside of a sphere surrounded by water. The applied electric discharge causes expansion and contraction of the crystals, and subsequently, a pressure wave in the water. This wave is focused precisely by the geometric positioning of the crystals [11]. During shock wave therapy, the waves propagate through the applied contact medium (usually a coupling gel) and reach interfaces of different tissue types. The physical properties of the waves change and energy is released. This release of mechanical and thermal energy affects change, possibly at the cellular and subcellular level. Exactly how these acoustic waves exert their effects has not been elucidated. Mechanical energy transfer to the tissue medium at the wave front is postulated to be the primary mechanism of change [11]. Alterations in cell membranes and their permeabilities have been reported [13]. The ability of the cell (neuron) to generate membrane potentials may be altered and affect how neurons transmit signals and pain stimuli. There also may be a direct suppressive effect on nociceptors along with hyperstimulation that result in a reflex analgesic phenomenon [14–16]. A proposed secondary mechanism involves cavitation—the phenomenon by which shock waves lead to the formation and subsequent implosion of interstitial water bubbles [17]. The energy released during this process may contribute to the disruption of tissue at interfaces like that of the plantar fascia and its inferomedial calcaneal insertion. Some investigators believe that this initiates an inflammatory response: the release of cytokines, nitric oxide synthase, and substance P; followed by inflammation, neovascularization, and the recruitment of precursor cells for regeneration and healing [18,19]. Because this mechanism of repair involves the creation of an acute wound environment, ESWT is likely to be more effective in chronic conditions than acute [20]. Patients who have long-standing symptoms have histologic evidence that supports fibrous changes rather than inflammatory changes. Therefore, some investigators believe that ‘‘fasciosis’’ is a more accurate descriptor than ‘‘fasciitis’’ [21].
Indications Plantar fasciitis is a common orthopedic problem, particularly in middle-aged patients. The typical presentation includes pain at the medial insertion of the
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plantar fascia, sometimes along its course, that often is worse upon arising in the morning or after prolonged rest. Obesity and lifestyles involving long periods of standing or walking (especially on hard surfaces) are believed to be risk factors [22]. In addition, abnormal pronation may contribute to excessive forces at the plantar fascia insertion, exerted through the windlass mechanism of the foot [23]. These factors may lead to repetitive partial tearing and chronic inflammation [24]. The natural history of this heel pain syndrome is that of gradual resolution in most patients within 12 months of onset of symptoms [25,26]. Approximately 10% of patients experience persistent, disabling symptoms [25]. Although the existing comparative studies have not isolated a universally effective therapy for plantar fasciitis, most practitioners advocate an initial, conservative approach. The goals of nonsurgical interventions are to modify biomechanical factors that lead to the increased stress on the involved tissues, and to quell the inflammatory response to the microtrauma that is occurring. Some of the biomechanical modalities that are used to accomplish this are heel pads, heel cups, noncustom and custom orthoses, and night splints. A structure-specific plantar fascia stretching program has demonstrated excellent results at our institution, superior to weight-bearing Achilles tendon stretching [27]. Examples of anti-inflammatory interventions are icing, rest, activity modification, nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroid injection, dexamethasone iontophoresis, and nonweight-bearing or walking casts. Surgical options are available and include partial or complete plantar fasciotomy (open versus endoscopic) with or without calcaneal exostectomy. The potential problems with these procedures include destabilization of the arch, scarring, metatarsalgia, recurrence, stress reaction of the calcaneus [28], and prolonged recovery time [29]. The ideal candidate for ESWT is believed to be a person who has longstanding plantar heel pain that is unresponsive to conservative therapy for longer than 6 months [14,20,30]; this is the FDA’s definition of chronic plantar fasciitis. Some investigators believe that patients are less likely to see a benefit with a shorter history of pain [31]. Other potential causes of heel pain include ruptured plantar fascia, tarsal tunnel syndrome, entrapment neuropathy, calcaneal stress fracture, and apophysitis; these must be ruled out before pursuing any treatment that has significant risks.
Administration of extracorporeal shock wave treatment The basic requirements of any shock wave delivery device are adequate, controllable power for generating effective shock waves, and the capability of targeting this energy accurately. The ‘‘dosage’’ of shock waves delivered varies in the literature. Most protocols are described as ‘‘low-energy’’ or ‘‘high-energy’’, and no consistent value exists for the EFD that corresponds to these descriptive terms.
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Preoperative and postoperative protocol ESWT is an outpatient procedure; some investigators advocate the discontinuation of anticoagulants and aspirin before the initiation of treatment. The procedure may be painful depending on the amount of energy delivered; therefore, local, regional, or general anesthesia can be used after the symptomatic points are identified and marked. Coupling gel is placed on the affected heel, which is moved in a slow circular motion within the focal zone as the shock waves are delivered (Fig. 1). Most physicians permit the patient to ambulate immediately after the procedure. Some advocate activity restrictions for the first 2 to 4 weeks [32]. The patients can be encouraged to continue with any existing shoe-wear modifications and stretching programs at the treating physician’s discretion.
Complications The adverse effects of ESWT seem to be few and minor. Reports of adverse effects include transient postprocedure pain, warm/burning sensations, edema, numbness, tingling, petechiae, and ecchymoses. Patients who have coagulopathies or those taking anticoagulants may be at increased risk for bleeding. Shock waves are known to cause lung parenchyma damage, and animal studies have
Fig. 1. Firm coupling of the foot to the therapy head to ensure effective transmission of the wave. (From Strash WW, Perez RR. Extracorporeal shockwave therapy for chronic plantar fasciitis. Clin Podiatr Med Surg 2002;19:474; with permission.)
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seen the induction of cardiac arrhythmias; however, no reports of these complications exist in human studies of ESWT. One study reported that a single patient sustained a rupture of the plantar fascia after shock wave therapy, but this patient had received multiple corticosteroid/lidocaine injections before treatment [32].
Food and Drug Administration–approved devices Two shock wave delivery devices are approved for use in the treatment of chronic plantar fasciitis that has not responded to conservative management. The OssaTron operates using the electrohydraulic mechanism (first to be approved in 2000) and is capable of producing a range of peak pressures. The Dornier Epos Ultra (Dornier MedTech, Kennesaw, Georgia), approved in 2001, uses electromagnetic technology for shock wave production with the advantage of precise focusing. A third shock wave delivery device, the Sonocur Plus (Siemens Medical Solutions, Inc., Iselin, New Jersey), approved in 2002 for the treatment of lateral epicondylitis has appeared in plantar fasciitis literature. As a new, technology-heavy procedure, ESWT is more expensive than the typically prescribed conservative therapies. The OssaTron and Dornier Epos Ultra are of comparable cost. The Sonocur, which is approved only for tennis elbow, is an in-office device, and therefore, is significantly less expensive. An example from one specialist’s practice approximates the cost per case (including staff, facility, and supplies) at $2250. The average charge for facility and device services is $4500 [33].
Discussion Since the early 1990s, ESWT has been used as an alternative and an adjunct to the currently accepted forms of conservative therapy. The advent of musculoskeletal-specific shock wave devices spawned numerous investigations into their effects on plantar fasciitis, a common and painful condition. These studies have provided data that help to answer important protocol and efficacy related questions (Table 1). Weil and colleagues [48] compared patient outcomes after high-energy ESWT with those of patients who had undergone percutaneous partial fasciotomy and found them to be comparable. The group that underwent ESWT was able to return to activities of daily living sooner. Chen and colleagues [35] enrolled 80 patients (86 heels) who had symptoms for longer than 6 months and inadequate response to conservative measures in a study that administered a single session (1000 impulses) of electrohydraulically generated high-energy shock waves. Their results demonstrated that 86.3% had partial to complete resolution of symptoms at 6 weeks after the procedure. None of the participants experienced worsening of their symptoms or local
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Table 1 Extracorporeal shock wave therapy and plantar fasciRtis: clinical series and trials Investigators [Ref]
Year
Device
Outcome
Clinical series Maier et al [34]
2000
Multiple devices
Chen et al [35]
2001
Dornier Medtech [36] Hammer et al [37]
2002
Strash and Perez [22] Alvarez et al [38] Lee et al [39]
2002
Ogden et al [40]
2004
Ossatron High Medical Technology Epos Ultra Dornier Medical Systems Piezoson 300 Richard Wolf (piezoelectric Ossatron High Medical Technology Ossatron High Medical Technology Ossatron High Medical Technology Ossatron High Medical Technology
No correlation between MRI findings and outcome 87% complete or near complete relief
2002
2003 2003
Randomized controlled trials Ogden et al [33] 2001 Rompe et al [41]
2002
Ossatron High Medical Technology Sonocur Plus Siemens
Rompe et al [42]
2003
Sonocur Plus Siemens
Theodore et al [43]
2004
Epos Ultra Dornier Medical Systems
Ogden et al [44]
2004
Buchbinder et al [45] Haake et al [46]
2002
Speed et al [47]
2003
Ossatron High Medical Technology Epos Ultra Dornier Medical Systems Epos Ultra Dornier Medical Systems Sonocur Plus Siemens
2003
Efficacy results for FDA approval Better results than diclofenac iontophoresis Increasing clinical improvement out to 12 weeks No correlation between symptom duration and outcome No correlation between presence of heel spur and outcome Bilateral involvement—83% satisfied at 1 year Decreased pain and increased activity in treated group Better results with 3 applications of 1000 impulses versus 3 applications of 10 impulses Decreased self-assessed pain in running athletes Clinical benefit increased in those with greater baseline pain and longer duration of symptoms 76.8% of treated patients had good to excellent results No significant difference in outcome between the groups No significant difference in outcome between the groups No significant difference in outcome between the groups
complications. Seventeen patients did not see initial improvement, underwent a second treatment session, and responded favorably. The study volunteers were followed out to 6 months, at which time 87% had complete or nearly complete relief; the remaining 13% had partial improvement. Strash and Perez [22] reported similar results in 48 heels that were treated with high-energy ESWT; the patients experienced increasing clinical improvement out to 12 weeks. These results underscore the safety of this procedure and suggest that patients may continue to see clinical benefits 6 months after treatment, and therefore, should be followed for at least that length of time.
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In 2004, Wilner and Strash [18] published data on a larger study population (264 patients treated with OssaTron high-energy ESWT). In this study, 87% of patients rated their results as good-to-excellent, 11% rated their results as fair, and 2% had no improvement; this re-emphasized previously published success. Some patients are unfortunate enough to suffer bilateral chronic heel pain. If conservative therapy fails and surgical intervention is considered, the postoperative weight-bearing restrictions may preclude simultaneous treatment of both heels. For these patients, ESWT can be a reasonable alternative and allows full weight bearing immediately after the bilateral procedure, with only a single exposure to anesthesia. Ogden and colleagues [40] demonstrated that 83% of their participants (23 patients; 46 heels) were satisfied with their results from this treatment approach at 1 year. The above-mentioned studies used electrohydraulic devices, which deliver high-energy shock waves (eg, OssaTron). Piezoelectric and electromagnetic devices produce lower energy pulses. Some investigators believe that highenergy pulses have a bimodal response with initial suppression of nociceptors followed by target-tissue remodeling, whereas low-energy devices may affect only nociceptor activity [38]. All three mechanisms are represented in the literature to varying degrees. Hammer and colleagues [37] randomized 48 patients into two groups: group 1 received three sessions of piezoelectric low-energy shock waves (3000 shock waves/session) and group 2 continued with NSAIDs and diclofenac iontophoresis. Group 1 saw significant improvement in symptoms compared with group 2. At 12 weeks, group 2 was administered the same ESWT protocol and experienced similar positive results. At 2-year follow-up, both groups had at least 90% improvement in pain during activities of daily living. As part of the FDA approval process, the Dornier Epos Ultra electromagnetic shock wave device was tested in an active versus sham treatment study design [36]. Approximately 62% of those in the low-energy treatment group reported good-to-excellent results compared with approximately 40% in the sham group; this provided the efficacy and safety data that were needed for device approval. Not only is it important to determine which ESWT devices and treatment protocols are successful, but it also is useful to know if certain patient variables are predictive of outcome. For example, Alvarez and colleagues [38] compared symptom duration in 262 patients who had plantar fasciitis with their clinical outcomes after shock wave therapy. All patients had heel pain for a minimum of 6 months. They found no strong correlation between duration of symptoms and clinical benefit from ESWT. Other investigators have sought to connect radiographic and MRI findings with clinical symptoms and effects of ESWT. For example, Lee and colleagues [39] looked at 435 patients who had chronic plantar fasciitis; 65% had radiographically evident inferior calcaneal heel spurring. After administering ESWT to some and placebo to others, no patient demonstrated significant radiographic change in the existing spur, nor was there any correlation between presence or absence of heel spur and clinical outcome.
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A prospective study of 48 heels with chronic plantar fasciitis was conducted during which a pretreatment MRI was performed which focused specifically on plantar aponeurosis thickness, soft tissue signal intensity and contrast uptake, and calcaneal bone marrow edema. No correlation was found between clinical outcome and the presence of aponeurosis thickness or soft tissue signal intensity and uptake; however, the presence of calcaneal bone marrow edema was predictive for symptom improvement after low-energy ESWT [34]. This suggests distinct different morphologic subtypes of chronic plantar fasciitis. As more is learned about the pathophysiology of this condition, MRI may help to guide physicians in patient selection for ESWT. MRI has been used to aid in the diagnosis of plantar fasciitis, and a recent study used this tool to observe the acute changes in the heel after high-energy shock wave therapy [49]. Twelve patients underwent MRI within 24 hours before and after the ESWT procedure. Increased soft tissue edema was the most common acute change seen. An investigation into long-term MRI findings, mechanism of effect, and correlation with clinical response is underway.
Prospective, randomized controlled trials An abundance of literature on ESWT exists; however, prospective, randomized controlled trials provide the strongest evidence of efficacy. These studies provide the evidence that is needed to draw conclusions and formulate treatment algorithms. Ogden and colleagues [33] enrolled 260 randomized patients in their doubleblinded, placebo-controlled trial to shed light on the safety and effectiveness of ESWT with the OssaTron machine. They found improvement in investigatorassessed pain, self-assessed pain, and self-assessed activity in the treatment arm of the study, and concluded that ESWT should be considered before surgical intervention. Low-energy ESWT was used in a two-tailed trial that compared three applications of 1000 impulses (group I) with three applications of 10 impulses (group II) in 112 patients [41]. The goal was to determine which treatment protocol provided a superior clinical outcome. The investigators found a higher rate of good-to-excellent results in group I at 6 months. In addition, group I had significant improvement in pain on manual pressure and the ability to walk without pain; no side effects were reported. Group II demonstrated improvement in all measured parameters when followed out to 5 years. The fact that plantar fasciitis often is a self-limiting condition and that patients may seek new treatment modalities after poor short-term success makes long-term assessment of ESWT difficult. Rompe and colleagues [42] determined the efficacy and safety of low-energy ESWT in a randomized, placebo-controlled trial that involved running athletes (N 30 miles/wk). Plantar fasciitis is one of the most common painful foot con-
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ditions in this population [50] and can plague their active lifestyles. Participants in the treatment arm received three applications of 2100 electromagnetically generated impulses (Sonocur Plus), whereas the sham group had a sound reflector placed between their heel and the device. The investigators measured pain with first walking in the morning as their primary outcome. They found a statistically significant difference in the mean reduction of self-assessed pain on first walking between the treatment and sham groups at 6 months (P = 0.0004) and 1 year (P b 0.0001). Another interesting outcome measure would have been the level of activity/running to which these patients had returned after ESWT. A more recent and larger trial was undertaken to evaluate high-energy shock wave therapy in a single therapeutic session. Theodore and colleagues [43] randomized 150 patients who had chronic plantar fasciitis in a double-blinded, placebo-controlled trial. All participants received a medial calcaneal nerve block before administration of 3800 shocks (Dornier Epos Ultra) or an air cushion that prevented shock wave penetration. Ultrasound guidance and patient feedback were used to focus the treatment to the epicenter of pain. A visual analog scale (VAS) was used to measure pain with first walking in the morning. The active group reported 56% success at 3 months and 94% at 12 months, whereas the control group reported 47% success at 3 months (unblinded and offered treatment at that time). Those who entered the crossover treatment group met with similar success. Their data suggest that patients who had a higher baseline pain score, longer duration of symptoms, and greater body weight experienced a greater improvement in their pain score as measured on a VAS. The most common adverse advents reported after receiving the high-energy pulses were pain during treatment (73%) and pain after treatment (37%) which were resolved in 3 to 5 days. In contrast to the above-mentioned studies, some published clinical trials have not demonstrated a significant beneficial effect of ESWT when compared with placebo. Buchbinder and colleagues [45] randomized 166 patients to receive ultrasound-guided low-energy ESWT (Dornier EPOS Ultra) weekly for 3 weeks for a total dose of at least 1000 mJ/mm2, or an identical placebo for a total dose of 6.0 mJ/mm2. At 6 and 12 weeks, both groups saw significant reduction in symptoms; the investigators concluded that ESWT was not providing a statistically significant benefit when compared with placebo. Other investigators have questioned the usefulness of these results, and have pointed out a few potential flaws in the study design, such as the inclusion of patients with as few as 8 weeks of symptoms, the lack of a minimum baseline pain requirement, and the treatment group receiving a range of shock wave ‘‘doses’’ with the control group also being exposed to shock waves (albeit at a lower dose) [42]. A well-designed trial of 272 patients was performed by Haake and colleagues [46] in which the patients had at least 6 months of symptoms and the control group did not receive any shock waves. The Dornier Epos Ultra was used to administer 4000 low-energy shock waves over three sessions for a higher total dose delivered than in any of the other trials [8,9]. They reported a 3.6% difference in success rates between the two study groups (P = 0.5927), and
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concluded that ESWT did not impart a meaningful clinical improvement compared with placebo controls. Critics of this study point out that fewer than 50% of the enrolled participants had received minimal conservative care (eg, splinting, casting, stretching) before inclusion in the trial. In addition, 36% of the treatment group and 56% of the placebo group had sought additional therapies by 1 year of follow-up which may have compromised the interpretation of the results. The investigators administered shock waves every 2 weeks for 3 sessions, whereas other investigators have chosen to do so in 1-week intervals; this highlights another variable that makes study comparison difficult. Speed and colleagues [47] performed a double-blinded, randomized, controlled trial with electromagnetically generated shock waves of moderate dose (1500 shocks at 0.12 mJ/mm2; Sonocur Plus) monthly for 3 months in 88 patients who had plantar fasciitis for at least 3 months. The treatment and control groups showed improvement during the trial, but again, there was no statistical difference in the amount of day pain or night pain between the two groups. Speed and colleagues used yet another different treatment regime with 1-month intervals between applications and moderate-dose shock waves. They used ultrasound localization along with patient feedback modification at the initiation of therapy to determine the point of maximal pain. Some investigators believe that this technique is inadequate and that to achieve effective focusing, patient feedback must be reassessed every 200 to 300 shocks. In addition, patients may not be able to tolerate this energy level at the site of pathology without anesthesia which calls into question the accuracy of shock wave delivery [51]. Perhaps the most convincing evidence arises from the randomized, placebocontrolled, multiple blinded, crossover trial that was conducted by Ogden and colleagues [44]. Phase 1 of this trial involved 20 nonrandomized patients who were treated with high-energy ESWT, to assess the phase 2 protocol. In phase 2, 293 patients were randomized to receive 1400 high-energy shocks or none (placebo). At 3 months, all patients were given the choice to discontinue treatment, receive further treatment, or (for placebo patients) to crossover into the treatment arm. All patients were followed for 1 year. Of the phase 1 participants, 19 of 20 patients achieved successful outcomes by 1 year. In phase 2 at 3 months, 47% of the treated patients and 30% of placebo patients had a completely successful result (P = 0.008). By 1 year, 65 of the 67 actively treated patients had a successful result. In total, 222 of the 289 patients (76.8%) that received at least one application of ESWT had a good or excellent result. The strength of this study lies not only in its randomized, controlled, and blinded design, but it includes several aspects that have been missing in other studies. First, the patients all had symptoms for a minimum of 6 months and they had failed to respond to conservative measures on at least three attempts: at least two trials of physical therapy and orthotic devices and at least one trial of pharmacologic treatment (aspirin, acetaminophen, NSAIDs). In addition, all treated patients received the same shock wave ‘‘dosage.’’ No shock waves were delivered to the placebo group, and trained orthopedists were involved in the evaluation and treatment of the patients.
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Summary The current body of evidence addressing the role of ESWT in plantar fasciitis supports its safety and promising potential for treatment of this common foot disorder. Further studies will aid in defining the most effective treatment variables. High-energy devices have achieved better results after a single application than the low-energy devices; however, the ideal intensity and number of shock waves is yet to be determined. Low-energy ESWT has the advantage of not requiring anesthesia but the most effective number of applications and the time between treatments has not been proven. Additional, well-designed, prospective, randomized, controlled trials are needed to shed light on these questions. A meta-analysis of the existing and future studies would be a big step in that direction. Because ESWT has not resulted in excessive morbidity, its cautious use as an alternative to surgical release should continue, coupled with effective adjuncts like structure-specific stretching. Patient selection is important, and the patients that are most likely to see a benefit are those who have persistent symptoms that have not responded to less expensive conservative therapies. It is hoped that the knowledge gained from future investigations will help to harness this energy effectively for the treatment of chronic plantar fasciitis as it has been for nephrolithiasis.
References [1] Thiel M. Application of shock waves in medicine. Clin Orthop 2001;387:18 – 21. [2] Krause H. Physics and technology of medical shockwave systems. In: Rompe JD, editor. Extraforporale Stogwellentherapie. Weinheim (Germany)7 Chapman & Hall, GmbH; 1997. p. 15 – 34 [in German]. [3] Hepp W, Grunewald M, Brendel W. Extracorporal shockwave lithotripsy. Spektrum der Wissenschaft 1991;7:44 – 53 [in German]. [4] Haeusler E, Kiefer W. Stimulation of shockwaves in fluids through high-speed water droplets. Verhand Dtsch Physikal Gesellschaft 1971;6:786 [in German]. [5] Haupt G. Use of extracorporeal shock waves in the treatment of pseudarthrosis, tendinopathy, and other orthopaedics diseases. J Urol 1997;158:4 – 11. [6] Vachalnov VD, Michailov P. High energy shock waves in the treatment of delayed and nonunion of fractures. Int Orthop 1991;15:181 – 4. [7] Loew M, Jurgowski W, Mau HC, et al. Treatment of calcifying tendonitis of the rotator cuff by extracorporeal shock waves: a preliminary report. J Shoulder Elbow Surg 1995;4:101 – 6. [8] Rompe JD, Hopf C, Kullmer K, et al. Analgesic effect of extracorporeal shockwave therapy on chronic tennis elbow. J Bone Joint Surg Br 1996;78:233 – 7. [9] Rompe JD, Hopf C, Nafe B, et al. Low-energy extracorporeal shock wave therapy for painful heel: a prospective, controlled single-blind study. Arch Orthop Trauma Surg 1996;115:75 – 9. [10] Henney JE. Shockwave for heel pain. From the Food and Drug Administration. JAMA 2000;284:2711. [11] Ogden JA, Toth-Kischkat A, Schultheiss R. Principles of shock wave therapy. Clin Orthop 2001;387:8 – 17. [12] Wess O, Ueberle F, Durhben RN, et al. Working group technical developments: consensus re-
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[13] [14] [15] [16] [17] [18]
[19] [20] [21] [22] [23] [24] [25] [26] [27]
[28] [29] [30] [31] [32] [33] [34]
[35] [36] [37]
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port in high energy shock waves in medicine. In: Chaussy C, Eisenberger F, Jocham D, et al, editors. High energy shock waves in medicine. Stuttgart (Germany)7 Thieme; 1997. Steinbach P, Hofstadter F, Nicolai H, et al. In vitro investigations on cellular damage induced by high energy shock waves. Ultrasound Med Biol 1992;18:691 – 9. Schelling G, Delius M, Gschwender M, et al. Extracorporeal shock waves stimulate frog sciatic nerves indirectly via a cavitation mediated mechanism. Biophys J 1994;66:133 – 40. Speed CA. Extracorporeal shock-wave therapy in the management of chronic soft-tissue conditions. J Bone Joint Surg Br 2004;86B:165 – 71. Melzack R. Prolonged relief of pain by brief, intense transcutaneous somatic stimulation. Pain 1975;1:357 – 73. Delius M. Medical applications and biological effects of extracorporeal shock waves. Shock Waves 1994;4:55 – 72. Wilner JM, Strash WW. Extracorporeal shockwave therapy for plantar fasciitis and other musculoskeletal conditions utilizing the Ossatron—an update. Clin Podiatr Med Surg 2004; 21:441 – 7. Wang CJ, Huang HY, Pai CH. Shockwave enhanced neovascularization at the tendon bone junction: an experiment in dogs. J Foot Ankle Surg 2001;41:16 – 22. Perez M, Weiner R, Gilley JC. Extracorporeal shock wave therapy for plantar fasciitis. Clin Podiatr Med Surg 2003;20:323 – 34. Lemont H, et al. Plantar fasciitis: a degenerative process (fasciosis) without inflammation. Journal of the American Podiatric Medical Association 2003;93:234. Strash WW, Perez RR. Extracorporeal shockwave therapy for chronic plantar fasciitis. Clin Podiatr Med Surg 2002;19:467 – 76. Fuller EA. The windlass mechanism of the foot. A mechanical model to explain pathology. J Am Podiatr Med Assoc 2000;90(1):35 – 46. Schepsis AA, Leach RE, Gorzyca J. Plantar fasciitis. Etiology, treatment, surgical results, and review of the literature. Clin Orthop 1991;266:185 – 96. Davis PF, Severud E, Baxter DE. Painful heel syndrome: results of nonoperative treatment. Foot Ankle Int 1994;15:531 – 5. Wolgin M, Cook C, Graham C, et al. Conservative treatment of plantar heel pain: long-term follow-up. Foot Ankle Int 1994;15:97 – 102. DiGiovanni BF, Nawoczenski DA, Lintal ME, et al. Tissue-specific plantar fascia-stretching exercise enhances outcomes in patients with chronic heel pain. J Bone Joint Surg 2003; 85A(7):1270 – 7. Jerosch J. Endoscopic release of the plantar fasciitis—a benign procedure? Foot Ankle Int 2000;21(6):511 – 3. Davies MS, Weiss GA, Saxby TS. Plantar fasciitis: how successful is surgical intervention? Foot Ankle Int 1999;20(12):803 – 7. Theodore GH. Shock wave therapy for treatment of plantar fasciitis. JAMA 2003;289:172. Helbig K, Herbert C, Schostok T, et al. Correlations between the durations of pain and the success of shock wave therapy. Clin Orthop 2001;387:68 – 71. Alvarez RG. Plantar fasciitis: perspectives on the most common adult foot problem. Orthopaedics Today 2004;24(10):46. Ogden JA, Alvarez RG, Levitt R, et al. Shock wave therapy for chronic proximal plantar fasciitis. Clin Orthop 2001;387:47 – 59. Maier M, Steinborn M, Schmitz C, et al. Extracorporeal shock wave application for chronic plantar fasciitis associated with heel spurs: prediction of outcome by magnetic resonance imaging. J Rheum 2000;27(10):2455 – 62. Chen HS, Chen LM, Huang TW. Treatment of painful heel syndrome with shock waves. Clin Orthop 2001;387:41 – 6. Dornier MedTech, Inc. FDA approved summary of safety and effectiveness. Dornier Epos Ultra, P000048, January 2002. Hammer DS, Rupp S, Kreutz A, et al. Extracorporeal shockwave therapy (ESWT) in patients with chronic proximal plantar fasciitis. Foot Ankle Int 2002;23(4):309 – 13.
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[38] Alvarez RG, Ogden JA, Jaakkola J, et al. Symptom duration of plantar fasciitis and the effectiveness of orthotripsy. Foot Ankle Int 2003;24(12):916 – 21. [39] Lee GP, Ogden JA, Cross GL. Effect of extracorporeal shock waves on calcaneal bone spurs. Foot Ankle Int 2003;24(12):927 – 30. [40] Ogden JA, Cross GL, Williams SS. Bilateral chronic proximal plantar fasciopathy: treatment with electrohydraulic orthotripsy. Foot Ankle Int 2004;25(5):298 – 302. [41] Rompe JD, Schoellner C, Nafe B. Evaluation of low-energy extracorporeal shock-wave application for treatment of chronic plantar fasciitis. J Bone Joint Surg 2002;84A(3):335 – 41. [42] Rompe JD, Decking J, Schoellner C, et al. Shock wave application for chronic plantar fasciitis in running athletes. Am J Sports Med 2003;31(2):268 – 74. [43] Theodore GH, Buch M, Amendola A, et al. Extracorporeal shock wave therapy for the treatment of plantar fasciitis. Foot Ankle Int 2004;25(5):290 – 7. [44] Ogden JA, Alvarez RG, Levitt RL, et al. Electrohydraulic high-energy shock-wave treatment for chronic plantar fasciitis. J Bone Joint Surg 2004;86A(10):2216 – 28. [45] Buchbinder R, Ptasznik R, Gordon J, et al. Ultrasound-guided extracorporeal shock wave therapy for plantar fasciitis. JAMA 2002;288(11):1364 – 72. [46] Haake M, Buch M, Schoellner C, et al. Extracorporeal shock wave therapy for plantar fasciitis: randomized controlled mulitcentre trial. BMJ 2003;327(7406):75. [47] Speed CA, Nichols D, Wies J, et al. Extracorporeal shock wave therapy for plantar fasciitis. A double blind randomized controlled trial. J Orthop Res 2003;21(5):937 – 40. [48] Weil Jr LS, Roukis TS, Weil LS, et al. Extracorporeal shock wave therapy for the treatment of chronic plantar fasciitis: indications, protocol, intermediate results, and a comparison of results to fasciotomy. J Foot Ankle Surg 2002;41:166 – 72. [49] Zhu F, Johnson JE, Hirose CB, et al. Chronic plantar fasciitis: acute changes in the heel after extracorporeal high-energy shock wave therapy—observations at MR imaging. Radiology 2005; 234(1):206 – 10. [50] Leach RE, Dilorio E, Harney RA. Pathologic hindfoot conditions in the athlete. Clin Orthop 1983;177:116 – 21. [51] Day B. Comment on: Extracorporeal shock wave therapy for plantar fasciitis. A double blind randomized controlled trial (J Orthop Res. 2003; 21(5): 937–40). J Orthop Res 2004;22(6):1365.
The Role of Extracorporeal Shock Wave on Plantar Fasciitis Gregory J. Roehrig, MD, Judith Baumhauer, MD*, Benedict F. DiGiovanni, MD, Adolph S. Flemister, MD Department of Orthopaedics, University of Rochester, Strong Memorial Hospital, 601 Elmwood Avenue, Box 665, Rochester, NY 14642, USA
Shock waves are acoustic waves that are capable of transmitting mechanical energy through a medium. As with many physical and chemical principles, scientists have sought and found ways in which this phenomenon affects the human body. The concept that shock waves can be used to alter the material structure of an object is well-established; the classic example is the in vivo destruction of renal calculi. With such knowledge, the scientific and medical communities continue to research and develop therapeutic methods to better the quality of life. Recent focus has been on the role of shock wave treatment for certain foot and ankle musculoskeletal conditions, specifically chronic plantar fasciitis. As more investigators delve into the questions of indication, administration, and therapeutic effect, the interest and enthusiasm for this modality continue to grow.
Historical background The first observation of shock waves affecting the human body occurred during World War II. Capsized, drifting sailors were found to have damaged lung tissue after being exposed to nearby depth charges [1]. Subsequent experiments revealed that electrohydraulically generated shock waves were capable of
* Corresponding author. E-mail address: [email protected] (J. Baumhauer). 1083-7515/05/$ – see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.fcl.2005.06.002
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breaking underwater ceramic plates [2]. Years later, an experimenter mistakenly touched a target plate at the instant that a high-velocity projectile struck, causing an electric shock-like sensation throughout his body [3]. These findings prompted the German government to sponsor investigations into the consequences of shock waves on human tissue. They discovered that the energy transmitted from an external source (even from long distances) resulted in damage to internal organs, such as the brain and lung, but relative sparing of muscle, fat, connective tissue, and bone [1]. Around that time, German scientists began to speculate whether shock waves could be used to fragment renal calculi. In 1971, Haeusler and Kiefer [4] were the first to report successful in vitro disintegration of a kidney stone. As the practice of lithotripsy began to blossom, researchers wondered about its effects on the nearby bones. In 1986, Haupt not only determined an absence of negative effect on osseous tissue, but also showed that shock waves seemed to stimulate bone formation. By 1988, he reported the first successful treatment of a fracture nonunion with shock wave therapy [5]. The same success was achieved by Valchanov and Michailov [6]. The 1990s saw German physicians expand the existing indications and begin treating soft tissue conditions, such as calcific rotator cuff tendonitis, lateral epicondylitis, and plantar fasciitis [7–9]. These new approaches necessitated modification of the shock wave generators into a more user-friendly and efficient orthopedic treatment tool. In 1993, such a device became available [1]. The US Food and Drug Administration (FDA) recognized the potential of extracorporeal shock wave therapy (ESWT), and authorized its use for chronic plantar fasciitis in October 2000. The OssaTron (HealthTronics Inc., Marietta, Georgia) was the pioneer electrohydraulic device that was approved for use on adult patients with at least 6 months of symptoms that were refractory to conservative measures [10].
Basic science of extracorporeal shock wave therapy A shock wave is a transient pulse of pressure transmitted rapidly through a medium in three dimensions. Some of the physical properties of these waves include amplitude, frequency, and rise time. The amplitudes can exceed 100 MPa, the frequencies can range from audible to ultrasonic, and the rise times can be on the order of nanoseconds. The key to harnessing this explosion of energy for clinical benefit is to control and focus its effects [11]. To do so, the approved devices concentrate the shock waves into an area on the order of a few square millimeters. Therefore, a useful descriptive unit of ‘‘dosage’’ is mJ/mm2, termed energy flux density (EFD) [12]. Three principle methods by which clinically applicable shock waves are produced include electrohydraulic, electromagnetic, and piezoelectric. The electrohydraulic method was the first to be developed. A high-voltage discharge
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between the tips of an electrode bathed in water results in vaporization of, and explosion within, that water. A pressure wave is produced, which is focused by a reflector for accurate administration [11]. Electromagnetic devices create a shock wave by sending a strong electric current through a coil and creating a magnetic field. This field creates current flow and deformation in a metal membrane bathed in medium. The deformation results in compression of this medium and propagation of a shock wave [11]. The third mechanism involves piezoelectric crystals. More than 1000 of these crystals are mounted geometrically on the inside of a sphere surrounded by water. The applied electric discharge causes expansion and contraction of the crystals, and subsequently, a pressure wave in the water. This wave is focused precisely by the geometric positioning of the crystals [11]. During shock wave therapy, the waves propagate through the applied contact medium (usually a coupling gel) and reach interfaces of different tissue types. The physical properties of the waves change and energy is released. This release of mechanical and thermal energy affects change, possibly at the cellular and subcellular level. Exactly how these acoustic waves exert their effects has not been elucidated. Mechanical energy transfer to the tissue medium at the wave front is postulated to be the primary mechanism of change [11]. Alterations in cell membranes and their permeabilities have been reported [13]. The ability of the cell (neuron) to generate membrane potentials may be altered and affect how neurons transmit signals and pain stimuli. There also may be a direct suppressive effect on nociceptors along with hyperstimulation that result in a reflex analgesic phenomenon [14–16]. A proposed secondary mechanism involves cavitation—the phenomenon by which shock waves lead to the formation and subsequent implosion of interstitial water bubbles [17]. The energy released during this process may contribute to the disruption of tissue at interfaces like that of the plantar fascia and its inferomedial calcaneal insertion. Some investigators believe that this initiates an inflammatory response: the release of cytokines, nitric oxide synthase, and substance P; followed by inflammation, neovascularization, and the recruitment of precursor cells for regeneration and healing [18,19]. Because this mechanism of repair involves the creation of an acute wound environment, ESWT is likely to be more effective in chronic conditions than acute [20]. Patients who have long-standing symptoms have histologic evidence that supports fibrous changes rather than inflammatory changes. Therefore, some investigators believe that ‘‘fasciosis’’ is a more accurate descriptor than ‘‘fasciitis’’ [21].
Indications Plantar fasciitis is a common orthopedic problem, particularly in middle-aged patients. The typical presentation includes pain at the medial insertion of the
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plantar fascia, sometimes along its course, that often is worse upon arising in the morning or after prolonged rest. Obesity and lifestyles involving long periods of standing or walking (especially on hard surfaces) are believed to be risk factors [22]. In addition, abnormal pronation may contribute to excessive forces at the plantar fascia insertion, exerted through the windlass mechanism of the foot [23]. These factors may lead to repetitive partial tearing and chronic inflammation [24]. The natural history of this heel pain syndrome is that of gradual resolution in most patients within 12 months of onset of symptoms [25,26]. Approximately 10% of patients experience persistent, disabling symptoms [25]. Although the existing comparative studies have not isolated a universally effective therapy for plantar fasciitis, most practitioners advocate an initial, conservative approach. The goals of nonsurgical interventions are to modify biomechanical factors that lead to the increased stress on the involved tissues, and to quell the inflammatory response to the microtrauma that is occurring. Some of the biomechanical modalities that are used to accomplish this are heel pads, heel cups, noncustom and custom orthoses, and night splints. A structure-specific plantar fascia stretching program has demonstrated excellent results at our institution, superior to weight-bearing Achilles tendon stretching [27]. Examples of anti-inflammatory interventions are icing, rest, activity modification, nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroid injection, dexamethasone iontophoresis, and nonweight-bearing or walking casts. Surgical options are available and include partial or complete plantar fasciotomy (open versus endoscopic) with or without calcaneal exostectomy. The potential problems with these procedures include destabilization of the arch, scarring, metatarsalgia, recurrence, stress reaction of the calcaneus [28], and prolonged recovery time [29]. The ideal candidate for ESWT is believed to be a person who has longstanding plantar heel pain that is unresponsive to conservative therapy for longer than 6 months [14,20,30]; this is the FDA’s definition of chronic plantar fasciitis. Some investigators believe that patients are less likely to see a benefit with a shorter history of pain [31]. Other potential causes of heel pain include ruptured plantar fascia, tarsal tunnel syndrome, entrapment neuropathy, calcaneal stress fracture, and apophysitis; these must be ruled out before pursuing any treatment that has significant risks.
Administration of extracorporeal shock wave treatment The basic requirements of any shock wave delivery device are adequate, controllable power for generating effective shock waves, and the capability of targeting this energy accurately. The ‘‘dosage’’ of shock waves delivered varies in the literature. Most protocols are described as ‘‘low-energy’’ or ‘‘high-energy’’, and no consistent value exists for the EFD that corresponds to these descriptive terms.
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Preoperative and postoperative protocol ESWT is an outpatient procedure; some investigators advocate the discontinuation of anticoagulants and aspirin before the initiation of treatment. The procedure may be painful depending on the amount of energy delivered; therefore, local, regional, or general anesthesia can be used after the symptomatic points are identified and marked. Coupling gel is placed on the affected heel, which is moved in a slow circular motion within the focal zone as the shock waves are delivered (Fig. 1). Most physicians permit the patient to ambulate immediately after the procedure. Some advocate activity restrictions for the first 2 to 4 weeks [32]. The patients can be encouraged to continue with any existing shoe-wear modifications and stretching programs at the treating physician’s discretion.
Complications The adverse effects of ESWT seem to be few and minor. Reports of adverse effects include transient postprocedure pain, warm/burning sensations, edema, numbness, tingling, petechiae, and ecchymoses. Patients who have coagulopathies or those taking anticoagulants may be at increased risk for bleeding. Shock waves are known to cause lung parenchyma damage, and animal studies have
Fig. 1. Firm coupling of the foot to the therapy head to ensure effective transmission of the wave. (From Strash WW, Perez RR. Extracorporeal shockwave therapy for chronic plantar fasciitis. Clin Podiatr Med Surg 2002;19:474; with permission.)
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seen the induction of cardiac arrhythmias; however, no reports of these complications exist in human studies of ESWT. One study reported that a single patient sustained a rupture of the plantar fascia after shock wave therapy, but this patient had received multiple corticosteroid/lidocaine injections before treatment [32].
Food and Drug Administration–approved devices Two shock wave delivery devices are approved for use in the treatment of chronic plantar fasciitis that has not responded to conservative management. The OssaTron operates using the electrohydraulic mechanism (first to be approved in 2000) and is capable of producing a range of peak pressures. The Dornier Epos Ultra (Dornier MedTech, Kennesaw, Georgia), approved in 2001, uses electromagnetic technology for shock wave production with the advantage of precise focusing. A third shock wave delivery device, the Sonocur Plus (Siemens Medical Solutions, Inc., Iselin, New Jersey), approved in 2002 for the treatment of lateral epicondylitis has appeared in plantar fasciitis literature. As a new, technology-heavy procedure, ESWT is more expensive than the typically prescribed conservative therapies. The OssaTron and Dornier Epos Ultra are of comparable cost. The Sonocur, which is approved only for tennis elbow, is an in-office device, and therefore, is significantly less expensive. An example from one specialist’s practice approximates the cost per case (including staff, facility, and supplies) at $2250. The average charge for facility and device services is $4500 [33].
Discussion Since the early 1990s, ESWT has been used as an alternative and an adjunct to the currently accepted forms of conservative therapy. The advent of musculoskeletal-specific shock wave devices spawned numerous investigations into their effects on plantar fasciitis, a common and painful condition. These studies have provided data that help to answer important protocol and efficacy related questions (Table 1). Weil and colleagues [48] compared patient outcomes after high-energy ESWT with those of patients who had undergone percutaneous partial fasciotomy and found them to be comparable. The group that underwent ESWT was able to return to activities of daily living sooner. Chen and colleagues [35] enrolled 80 patients (86 heels) who had symptoms for longer than 6 months and inadequate response to conservative measures in a study that administered a single session (1000 impulses) of electrohydraulically generated high-energy shock waves. Their results demonstrated that 86.3% had partial to complete resolution of symptoms at 6 weeks after the procedure. None of the participants experienced worsening of their symptoms or local
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Table 1 Extracorporeal shock wave therapy and plantar fasciRtis: clinical series and trials Investigators [Ref]
Year
Device
Outcome
Clinical series Maier et al [34]
2000
Multiple devices
Chen et al [35]
2001
Dornier Medtech [36] Hammer et al [37]
2002
Strash and Perez [22] Alvarez et al [38] Lee et al [39]
2002
Ogden et al [40]
2004
Ossatron High Medical Technology Epos Ultra Dornier Medical Systems Piezoson 300 Richard Wolf (piezoelectric Ossatron High Medical Technology Ossatron High Medical Technology Ossatron High Medical Technology Ossatron High Medical Technology
No correlation between MRI findings and outcome 87% complete or near complete relief
2002
2003 2003
Randomized controlled trials Ogden et al [33] 2001 Rompe et al [41]
2002
Ossatron High Medical Technology Sonocur Plus Siemens
Rompe et al [42]
2003
Sonocur Plus Siemens
Theodore et al [43]
2004
Epos Ultra Dornier Medical Systems
Ogden et al [44]
2004
Buchbinder et al [45] Haake et al [46]
2002
Speed et al [47]
2003
Ossatron High Medical Technology Epos Ultra Dornier Medical Systems Epos Ultra Dornier Medical Systems Sonocur Plus Siemens
2003
Efficacy results for FDA approval Better results than diclofenac iontophoresis Increasing clinical improvement out to 12 weeks No correlation between symptom duration and outcome No correlation between presence of heel spur and outcome Bilateral involvement—83% satisfied at 1 year Decreased pain and increased activity in treated group Better results with 3 applications of 1000 impulses versus 3 applications of 10 impulses Decreased self-assessed pain in running athletes Clinical benefit increased in those with greater baseline pain and longer duration of symptoms 76.8% of treated patients had good to excellent results No significant difference in outcome between the groups No significant difference in outcome between the groups No significant difference in outcome between the groups
complications. Seventeen patients did not see initial improvement, underwent a second treatment session, and responded favorably. The study volunteers were followed out to 6 months, at which time 87% had complete or nearly complete relief; the remaining 13% had partial improvement. Strash and Perez [22] reported similar results in 48 heels that were treated with high-energy ESWT; the patients experienced increasing clinical improvement out to 12 weeks. These results underscore the safety of this procedure and suggest that patients may continue to see clinical benefits 6 months after treatment, and therefore, should be followed for at least that length of time.
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In 2004, Wilner and Strash [18] published data on a larger study population (264 patients treated with OssaTron high-energy ESWT). In this study, 87% of patients rated their results as good-to-excellent, 11% rated their results as fair, and 2% had no improvement; this re-emphasized previously published success. Some patients are unfortunate enough to suffer bilateral chronic heel pain. If conservative therapy fails and surgical intervention is considered, the postoperative weight-bearing restrictions may preclude simultaneous treatment of both heels. For these patients, ESWT can be a reasonable alternative and allows full weight bearing immediately after the bilateral procedure, with only a single exposure to anesthesia. Ogden and colleagues [40] demonstrated that 83% of their participants (23 patients; 46 heels) were satisfied with their results from this treatment approach at 1 year. The above-mentioned studies used electrohydraulic devices, which deliver high-energy shock waves (eg, OssaTron). Piezoelectric and electromagnetic devices produce lower energy pulses. Some investigators believe that highenergy pulses have a bimodal response with initial suppression of nociceptors followed by target-tissue remodeling, whereas low-energy devices may affect only nociceptor activity [38]. All three mechanisms are represented in the literature to varying degrees. Hammer and colleagues [37] randomized 48 patients into two groups: group 1 received three sessions of piezoelectric low-energy shock waves (3000 shock waves/session) and group 2 continued with NSAIDs and diclofenac iontophoresis. Group 1 saw significant improvement in symptoms compared with group 2. At 12 weeks, group 2 was administered the same ESWT protocol and experienced similar positive results. At 2-year follow-up, both groups had at least 90% improvement in pain during activities of daily living. As part of the FDA approval process, the Dornier Epos Ultra electromagnetic shock wave device was tested in an active versus sham treatment study design [36]. Approximately 62% of those in the low-energy treatment group reported good-to-excellent results compared with approximately 40% in the sham group; this provided the efficacy and safety data that were needed for device approval. Not only is it important to determine which ESWT devices and treatment protocols are successful, but it also is useful to know if certain patient variables are predictive of outcome. For example, Alvarez and colleagues [38] compared symptom duration in 262 patients who had plantar fasciitis with their clinical outcomes after shock wave therapy. All patients had heel pain for a minimum of 6 months. They found no strong correlation between duration of symptoms and clinical benefit from ESWT. Other investigators have sought to connect radiographic and MRI findings with clinical symptoms and effects of ESWT. For example, Lee and colleagues [39] looked at 435 patients who had chronic plantar fasciitis; 65% had radiographically evident inferior calcaneal heel spurring. After administering ESWT to some and placebo to others, no patient demonstrated significant radiographic change in the existing spur, nor was there any correlation between presence or absence of heel spur and clinical outcome.
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A prospective study of 48 heels with chronic plantar fasciitis was conducted during which a pretreatment MRI was performed which focused specifically on plantar aponeurosis thickness, soft tissue signal intensity and contrast uptake, and calcaneal bone marrow edema. No correlation was found between clinical outcome and the presence of aponeurosis thickness or soft tissue signal intensity and uptake; however, the presence of calcaneal bone marrow edema was predictive for symptom improvement after low-energy ESWT [34]. This suggests distinct different morphologic subtypes of chronic plantar fasciitis. As more is learned about the pathophysiology of this condition, MRI may help to guide physicians in patient selection for ESWT. MRI has been used to aid in the diagnosis of plantar fasciitis, and a recent study used this tool to observe the acute changes in the heel after high-energy shock wave therapy [49]. Twelve patients underwent MRI within 24 hours before and after the ESWT procedure. Increased soft tissue edema was the most common acute change seen. An investigation into long-term MRI findings, mechanism of effect, and correlation with clinical response is underway.
Prospective, randomized controlled trials An abundance of literature on ESWT exists; however, prospective, randomized controlled trials provide the strongest evidence of efficacy. These studies provide the evidence that is needed to draw conclusions and formulate treatment algorithms. Ogden and colleagues [33] enrolled 260 randomized patients in their doubleblinded, placebo-controlled trial to shed light on the safety and effectiveness of ESWT with the OssaTron machine. They found improvement in investigatorassessed pain, self-assessed pain, and self-assessed activity in the treatment arm of the study, and concluded that ESWT should be considered before surgical intervention. Low-energy ESWT was used in a two-tailed trial that compared three applications of 1000 impulses (group I) with three applications of 10 impulses (group II) in 112 patients [41]. The goal was to determine which treatment protocol provided a superior clinical outcome. The investigators found a higher rate of good-to-excellent results in group I at 6 months. In addition, group I had significant improvement in pain on manual pressure and the ability to walk without pain; no side effects were reported. Group II demonstrated improvement in all measured parameters when followed out to 5 years. The fact that plantar fasciitis often is a self-limiting condition and that patients may seek new treatment modalities after poor short-term success makes long-term assessment of ESWT difficult. Rompe and colleagues [42] determined the efficacy and safety of low-energy ESWT in a randomized, placebo-controlled trial that involved running athletes (N 30 miles/wk). Plantar fasciitis is one of the most common painful foot con-
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ditions in this population [50] and can plague their active lifestyles. Participants in the treatment arm received three applications of 2100 electromagnetically generated impulses (Sonocur Plus), whereas the sham group had a sound reflector placed between their heel and the device. The investigators measured pain with first walking in the morning as their primary outcome. They found a statistically significant difference in the mean reduction of self-assessed pain on first walking between the treatment and sham groups at 6 months (P = 0.0004) and 1 year (P b 0.0001). Another interesting outcome measure would have been the level of activity/running to which these patients had returned after ESWT. A more recent and larger trial was undertaken to evaluate high-energy shock wave therapy in a single therapeutic session. Theodore and colleagues [43] randomized 150 patients who had chronic plantar fasciitis in a double-blinded, placebo-controlled trial. All participants received a medial calcaneal nerve block before administration of 3800 shocks (Dornier Epos Ultra) or an air cushion that prevented shock wave penetration. Ultrasound guidance and patient feedback were used to focus the treatment to the epicenter of pain. A visual analog scale (VAS) was used to measure pain with first walking in the morning. The active group reported 56% success at 3 months and 94% at 12 months, whereas the control group reported 47% success at 3 months (unblinded and offered treatment at that time). Those who entered the crossover treatment group met with similar success. Their data suggest that patients who had a higher baseline pain score, longer duration of symptoms, and greater body weight experienced a greater improvement in their pain score as measured on a VAS. The most common adverse advents reported after receiving the high-energy pulses were pain during treatment (73%) and pain after treatment (37%) which were resolved in 3 to 5 days. In contrast to the above-mentioned studies, some published clinical trials have not demonstrated a significant beneficial effect of ESWT when compared with placebo. Buchbinder and colleagues [45] randomized 166 patients to receive ultrasound-guided low-energy ESWT (Dornier EPOS Ultra) weekly for 3 weeks for a total dose of at least 1000 mJ/mm2, or an identical placebo for a total dose of 6.0 mJ/mm2. At 6 and 12 weeks, both groups saw significant reduction in symptoms; the investigators concluded that ESWT was not providing a statistically significant benefit when compared with placebo. Other investigators have questioned the usefulness of these results, and have pointed out a few potential flaws in the study design, such as the inclusion of patients with as few as 8 weeks of symptoms, the lack of a minimum baseline pain requirement, and the treatment group receiving a range of shock wave ‘‘doses’’ with the control group also being exposed to shock waves (albeit at a lower dose) [42]. A well-designed trial of 272 patients was performed by Haake and colleagues [46] in which the patients had at least 6 months of symptoms and the control group did not receive any shock waves. The Dornier Epos Ultra was used to administer 4000 low-energy shock waves over three sessions for a higher total dose delivered than in any of the other trials [8,9]. They reported a 3.6% difference in success rates between the two study groups (P = 0.5927), and
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concluded that ESWT did not impart a meaningful clinical improvement compared with placebo controls. Critics of this study point out that fewer than 50% of the enrolled participants had received minimal conservative care (eg, splinting, casting, stretching) before inclusion in the trial. In addition, 36% of the treatment group and 56% of the placebo group had sought additional therapies by 1 year of follow-up which may have compromised the interpretation of the results. The investigators administered shock waves every 2 weeks for 3 sessions, whereas other investigators have chosen to do so in 1-week intervals; this highlights another variable that makes study comparison difficult. Speed and colleagues [47] performed a double-blinded, randomized, controlled trial with electromagnetically generated shock waves of moderate dose (1500 shocks at 0.12 mJ/mm2; Sonocur Plus) monthly for 3 months in 88 patients who had plantar fasciitis for at least 3 months. The treatment and control groups showed improvement during the trial, but again, there was no statistical difference in the amount of day pain or night pain between the two groups. Speed and colleagues used yet another different treatment regime with 1-month intervals between applications and moderate-dose shock waves. They used ultrasound localization along with patient feedback modification at the initiation of therapy to determine the point of maximal pain. Some investigators believe that this technique is inadequate and that to achieve effective focusing, patient feedback must be reassessed every 200 to 300 shocks. In addition, patients may not be able to tolerate this energy level at the site of pathology without anesthesia which calls into question the accuracy of shock wave delivery [51]. Perhaps the most convincing evidence arises from the randomized, placebocontrolled, multiple blinded, crossover trial that was conducted by Ogden and colleagues [44]. Phase 1 of this trial involved 20 nonrandomized patients who were treated with high-energy ESWT, to assess the phase 2 protocol. In phase 2, 293 patients were randomized to receive 1400 high-energy shocks or none (placebo). At 3 months, all patients were given the choice to discontinue treatment, receive further treatment, or (for placebo patients) to crossover into the treatment arm. All patients were followed for 1 year. Of the phase 1 participants, 19 of 20 patients achieved successful outcomes by 1 year. In phase 2 at 3 months, 47% of the treated patients and 30% of placebo patients had a completely successful result (P = 0.008). By 1 year, 65 of the 67 actively treated patients had a successful result. In total, 222 of the 289 patients (76.8%) that received at least one application of ESWT had a good or excellent result. The strength of this study lies not only in its randomized, controlled, and blinded design, but it includes several aspects that have been missing in other studies. First, the patients all had symptoms for a minimum of 6 months and they had failed to respond to conservative measures on at least three attempts: at least two trials of physical therapy and orthotic devices and at least one trial of pharmacologic treatment (aspirin, acetaminophen, NSAIDs). In addition, all treated patients received the same shock wave ‘‘dosage.’’ No shock waves were delivered to the placebo group, and trained orthopedists were involved in the evaluation and treatment of the patients.
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Summary The current body of evidence addressing the role of ESWT in plantar fasciitis supports its safety and promising potential for treatment of this common foot disorder. Further studies will aid in defining the most effective treatment variables. High-energy devices have achieved better results after a single application than the low-energy devices; however, the ideal intensity and number of shock waves is yet to be determined. Low-energy ESWT has the advantage of not requiring anesthesia but the most effective number of applications and the time between treatments has not been proven. Additional, well-designed, prospective, randomized, controlled trials are needed to shed light on these questions. A meta-analysis of the existing and future studies would be a big step in that direction. Because ESWT has not resulted in excessive morbidity, its cautious use as an alternative to surgical release should continue, coupled with effective adjuncts like structure-specific stretching. Patient selection is important, and the patients that are most likely to see a benefit are those who have persistent symptoms that have not responded to less expensive conservative therapies. It is hoped that the knowledge gained from future investigations will help to harness this energy effectively for the treatment of chronic plantar fasciitis as it has been for nephrolithiasis.
References [1] Thiel M. Application of shock waves in medicine. Clin Orthop 2001;387:18 – 21. [2] Krause H. Physics and technology of medical shockwave systems. In: Rompe JD, editor. Extraforporale Stogwellentherapie. Weinheim (Germany)7 Chapman & Hall, GmbH; 1997. p. 15 – 34 [in German]. [3] Hepp W, Grunewald M, Brendel W. Extracorporal shockwave lithotripsy. Spektrum der Wissenschaft 1991;7:44 – 53 [in German]. [4] Haeusler E, Kiefer W. Stimulation of shockwaves in fluids through high-speed water droplets. Verhand Dtsch Physikal Gesellschaft 1971;6:786 [in German]. [5] Haupt G. Use of extracorporeal shock waves in the treatment of pseudarthrosis, tendinopathy, and other orthopaedics diseases. J Urol 1997;158:4 – 11. [6] Vachalnov VD, Michailov P. High energy shock waves in the treatment of delayed and nonunion of fractures. Int Orthop 1991;15:181 – 4. [7] Loew M, Jurgowski W, Mau HC, et al. Treatment of calcifying tendonitis of the rotator cuff by extracorporeal shock waves: a preliminary report. J Shoulder Elbow Surg 1995;4:101 – 6. [8] Rompe JD, Hopf C, Kullmer K, et al. Analgesic effect of extracorporeal shockwave therapy on chronic tennis elbow. J Bone Joint Surg Br 1996;78:233 – 7. [9] Rompe JD, Hopf C, Nafe B, et al. Low-energy extracorporeal shock wave therapy for painful heel: a prospective, controlled single-blind study. Arch Orthop Trauma Surg 1996;115:75 – 9. [10] Henney JE. Shockwave for heel pain. From the Food and Drug Administration. JAMA 2000;284:2711. [11] Ogden JA, Toth-Kischkat A, Schultheiss R. Principles of shock wave therapy. Clin Orthop 2001;387:8 – 17. [12] Wess O, Ueberle F, Durhben RN, et al. Working group technical developments: consensus re-
plantar fasciitis: extracorporeal shock wave
[13] [14] [15] [16] [17] [18]
[19] [20] [21] [22] [23] [24] [25] [26] [27]
[28] [29] [30] [31] [32] [33] [34]
[35] [36] [37]
711
port in high energy shock waves in medicine. In: Chaussy C, Eisenberger F, Jocham D, et al, editors. High energy shock waves in medicine. Stuttgart (Germany)7 Thieme; 1997. Steinbach P, Hofstadter F, Nicolai H, et al. In vitro investigations on cellular damage induced by high energy shock waves. Ultrasound Med Biol 1992;18:691 – 9. Schelling G, Delius M, Gschwender M, et al. Extracorporeal shock waves stimulate frog sciatic nerves indirectly via a cavitation mediated mechanism. Biophys J 1994;66:133 – 40. Speed CA. Extracorporeal shock-wave therapy in the management of chronic soft-tissue conditions. J Bone Joint Surg Br 2004;86B:165 – 71. Melzack R. Prolonged relief of pain by brief, intense transcutaneous somatic stimulation. Pain 1975;1:357 – 73. Delius M. Medical applications and biological effects of extracorporeal shock waves. Shock Waves 1994;4:55 – 72. Wilner JM, Strash WW. Extracorporeal shockwave therapy for plantar fasciitis and other musculoskeletal conditions utilizing the Ossatron—an update. Clin Podiatr Med Surg 2004; 21:441 – 7. Wang CJ, Huang HY, Pai CH. Shockwave enhanced neovascularization at the tendon bone junction: an experiment in dogs. J Foot Ankle Surg 2001;41:16 – 22. Perez M, Weiner R, Gilley JC. Extracorporeal shock wave therapy for plantar fasciitis. Clin Podiatr Med Surg 2003;20:323 – 34. Lemont H, et al. Plantar fasciitis: a degenerative process (fasciosis) without inflammation. Journal of the American Podiatric Medical Association 2003;93:234. Strash WW, Perez RR. Extracorporeal shockwave therapy for chronic plantar fasciitis. Clin Podiatr Med Surg 2002;19:467 – 76. Fuller EA. The windlass mechanism of the foot. A mechanical model to explain pathology. J Am Podiatr Med Assoc 2000;90(1):35 – 46. Schepsis AA, Leach RE, Gorzyca J. Plantar fasciitis. Etiology, treatment, surgical results, and review of the literature. Clin Orthop 1991;266:185 – 96. Davis PF, Severud E, Baxter DE. Painful heel syndrome: results of nonoperative treatment. Foot Ankle Int 1994;15:531 – 5. Wolgin M, Cook C, Graham C, et al. Conservative treatment of plantar heel pain: long-term follow-up. Foot Ankle Int 1994;15:97 – 102. DiGiovanni BF, Nawoczenski DA, Lintal ME, et al. Tissue-specific plantar fascia-stretching exercise enhances outcomes in patients with chronic heel pain. J Bone Joint Surg 2003; 85A(7):1270 – 7. Jerosch J. Endoscopic release of the plantar fasciitis—a benign procedure? Foot Ankle Int 2000;21(6):511 – 3. Davies MS, Weiss GA, Saxby TS. Plantar fasciitis: how successful is surgical intervention? Foot Ankle Int 1999;20(12):803 – 7. Theodore GH. Shock wave therapy for treatment of plantar fasciitis. JAMA 2003;289:172. Helbig K, Herbert C, Schostok T, et al. Correlations between the durations of pain and the success of shock wave therapy. Clin Orthop 2001;387:68 – 71. Alvarez RG. Plantar fasciitis: perspectives on the most common adult foot problem. Orthopaedics Today 2004;24(10):46. Ogden JA, Alvarez RG, Levitt R, et al. Shock wave therapy for chronic proximal plantar fasciitis. Clin Orthop 2001;387:47 – 59. Maier M, Steinborn M, Schmitz C, et al. Extracorporeal shock wave application for chronic plantar fasciitis associated with heel spurs: prediction of outcome by magnetic resonance imaging. J Rheum 2000;27(10):2455 – 62. Chen HS, Chen LM, Huang TW. Treatment of painful heel syndrome with shock waves. Clin Orthop 2001;387:41 – 6. Dornier MedTech, Inc. FDA approved summary of safety and effectiveness. Dornier Epos Ultra, P000048, January 2002. Hammer DS, Rupp S, Kreutz A, et al. Extracorporeal shockwave therapy (ESWT) in patients with chronic proximal plantar fasciitis. Foot Ankle Int 2002;23(4):309 – 13.
712
roehrig et al
[38] Alvarez RG, Ogden JA, Jaakkola J, et al. Symptom duration of plantar fasciitis and the effectiveness of orthotripsy. Foot Ankle Int 2003;24(12):916 – 21. [39] Lee GP, Ogden JA, Cross GL. Effect of extracorporeal shock waves on calcaneal bone spurs. Foot Ankle Int 2003;24(12):927 – 30. [40] Ogden JA, Cross GL, Williams SS. Bilateral chronic proximal plantar fasciopathy: treatment with electrohydraulic orthotripsy. Foot Ankle Int 2004;25(5):298 – 302. [41] Rompe JD, Schoellner C, Nafe B. Evaluation of low-energy extracorporeal shock-wave application for treatment of chronic plantar fasciitis. J Bone Joint Surg 2002;84A(3):335 – 41. [42] Rompe JD, Decking J, Schoellner C, et al. Shock wave application for chronic plantar fasciitis in running athletes. Am J Sports Med 2003;31(2):268 – 74. [43] Theodore GH, Buch M, Amendola A, et al. Extracorporeal shock wave therapy for the treatment of plantar fasciitis. Foot Ankle Int 2004;25(5):290 – 7. [44] Ogden JA, Alvarez RG, Levitt RL, et al. Electrohydraulic high-energy shock-wave treatment for chronic plantar fasciitis. J Bone Joint Surg 2004;86A(10):2216 – 28. [45] Buchbinder R, Ptasznik R, Gordon J, et al. Ultrasound-guided extracorporeal shock wave therapy for plantar fasciitis. JAMA 2002;288(11):1364 – 72. [46] Haake M, Buch M, Schoellner C, et al. Extracorporeal shock wave therapy for plantar fasciitis: randomized controlled mulitcentre trial. BMJ 2003;327(7406):75. [47] Speed CA, Nichols D, Wies J, et al. Extracorporeal shock wave therapy for plantar fasciitis. A double blind randomized controlled trial. J Orthop Res 2003;21(5):937 – 40. [48] Weil Jr LS, Roukis TS, Weil LS, et al. Extracorporeal shock wave therapy for the treatment of chronic plantar fasciitis: indications, protocol, intermediate results, and a comparison of results to fasciotomy. J Foot Ankle Surg 2002;41:166 – 72. [49] Zhu F, Johnson JE, Hirose CB, et al. Chronic plantar fasciitis: acute changes in the heel after extracorporeal high-energy shock wave therapy—observations at MR imaging. Radiology 2005; 234(1):206 – 10. [50] Leach RE, Dilorio E, Harney RA. Pathologic hindfoot conditions in the athlete. Clin Orthop 1983;177:116 – 21. [51] Day B. Comment on: Extracorporeal shock wave therapy for plantar fasciitis. A double blind randomized controlled trial (J Orthop Res. 2003; 21(5): 937–40). J Orthop Res 2004;22(6):1365.