Absence of spinal response to extracorporeal shock waves on the endogenous opioid systems in the rat

Molecular Mechanisms Underlying the Pain-Relieving Effects of Extracorporeal Shock Wave Therapy: A Focus on Fascia Nociceptors

In recent years, extracorporeal shock wave therapy (ESWT) has received increasing attention for its potential beneficial effects on various bone and soft-tissue pathologies, yielding promising outcomes for pain relief and functional recovery. In fact, ESWT has emerged as an alternative, non-invasive, and safe treatment for the management of numerous musculoskeletal disorders, including myofascial pain syndrome (MPS). In particular, MPS is a common chronic painful condition, accounting for the largest proportion of patients affected by musculoskeletal problems. Remarkably, sensory innervation and nociceptors of the fascial system are emerging to play a pivotal role as pain generators in MPS. At the same time, increasing evidence demonstrates that application of ESWT results in selective loss of sensory unmyelinated nerve fibers, thereby inducing long-lasting analgesia. The findings discussed in the present review are supposed to add novel viewpoints that may further enrich our knowledge on the complex interactions occurring between disorders of the deep fascia including changes in innervation, sensitization of fascial nociceptors, the pathophysiology of chronic musculoskeletal pain of MPS, and EWST-induced analgesia. Moreover, gaining mechanistic insights into the molecular mechanisms of pain-alleviating effects of ESWT may broaden the fields of shock waves clinical practice far beyond the musculoskeletal system or its original application for lithotripsy.

The Effects of the Exposure of Musculoskeletal Tissue to Extracorporeal Shock Waves

Extracorporeal shock wave therapy (ESWT) is a safe and effective treatment option for various pathologies of the musculoskeletal system. Many studies address the molecular and cellular mechanisms of action of ESWT. However, to date, no uniform concept could be established on this matter. In the present study, we perform a systematic review of the effects of exposure of musculoskeletal tissue to extracorporeal shock waves (ESWs) reported in the literature. The key results are as follows: (i) compared to the effects of many other forms of therapy, the clinical benefit of ESWT does not appear to be based on a single mechanism; (ii) different tissues respond to the same mechanical stimulus in different ways; (iii) just because a mechanism of action of ESWT is described in a study does not automatically mean that this mechanism is relevant to the observed clinical effect; (iv) focused ESWs and radial ESWs seem to act in a similar way; and (v) even the most sophisticated research into the effects of exposure of musculoskeletal tissue to ESWs cannot substitute clinical research in order to determine the optimum intensity, treatment frequency and localization of ESWT.

Analgesic Effect of Extracorporeal Shock-Wave Therapy in Individuals with Lateral Epicondylitis: A Randomized Controlled Trial

This study was conducted to investigate the effect of extracorporeal shock-wave therapy (ESWT) on pain, grip strength, and upper-extremity function in lateral epicondylitis. A sample of 40 patients with LE (21 males) was randomly allocated to either the ESWT experimental (n = 20) or the conventional-physiotherapy control group (n = 20). All patients received five sessions during the treatment program. The outcome measures used were the Visual Analog Scale (VAS), the Taiwan version of the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire, and a dynamometer (maximal grip strength). Forty participants completed the study. Participants in both groups improved significantly after treatment in terms of VAS (pain reduced), maximal grip strength, and DASH scores. However, the pain was reduced and upper-extremity function and maximal grip strength were more significantly improved after ESWT in the experimental group. ESWT has a superior effect in reducing pain and improving upper-extremity function and grip strength in people with lateral epicondylitis. It seems that five sessions of ESWT are optimal to produce a significant difference. Further studies are strongly needed to verify our findings.

[Extracorporal shock wave therapy for the treatment of pseudarthrosis : New experiences with an old technology]

BACKGROUND

Between 5 and 10 % of all fractures show disturbed healing or nonunion formation. Extracorporeal shock wave therapy (ESWT) has been described as a non-surgical treatment option. Even though the outcome has shown promising results, the procedure is not commonly used in clinical practice. The purpose of this study was to analyze the union rate of pseudarthrosis and the cost savings after ESWT.

METHODS

In this study 42 nonunions were treated with shock waves (LithSpaceOrtho, JenaMedtech). The follow up examinations were performed over a period of six months. Outcome measurement included radiological fracture union and pain (VAS). The study group contained 39 pseudarthrosis in the six-week follow-up (93 %), 41 after three months (98 %) and 41 after six months (98 %).

RESULTS

After six weeks, 13 % of patients showed fracture union. After three months 61 % and after six months 73 % of the fractures were completely healed. The fracture healing was significantly lower in older nonunions. All patients presented significantly lower pain levels six weeks after ESWT. Shock wave treatment of all 42 pseudarthrosis made up less than one quarter of the overall operative costs.

CONCLUSION

We established the ESWT as an important treatment option for fracture nonunion in our clinic. Considering the selection of patients in this study with a high mean time from injury to ESWT and multiple prior operations, the fracture healing rate of 73 % after ESWT is comparable with operative healing rates of nonunions. Further prospective, randomized and controlled studies are needed to show the effectiveness of ESWT in the treatment of nonunions on a higher level of evidence and to identify pseudarthrosis that particularly responds to the EWST.

A review of the cellular and molecular effects of extracorporeal shockwave therapy

Extracorporeal shockwave therapy (ESWT) is a novel therapeutic modality and its use in promoting connective tissue repair and analgesic effect has been advocated in the literature. It is convenient, cost-effective, and has negligible complications; it therefore bypasses many of the problems associated with surgical interventions. This paper reviews the proposed mechanisms of action in promoting tissue repair and regeneration as well as analysing its efficacy providing an analgesic effect in clinical applications. Further research will be required to not only identify the underlying mechanisms more precisely, but will also be critical for ensuring consistency across the literature so that the most beneficial treatment protocol can be developed. Extracorporeal shockwave therapy stands as a promising alternative modality in promoting tissue repair.

The Effect of Low Dose Extracorporeal Shock Wave Therapy (ESWT) on Plantar Fasciitis: A Trial Study in Queen Mary Hospital

Background/Purpose

To assess the efficacy of low-energy extracorporeal Shockwave therapy (ESWT) for the treatment of plantar fasciitis.

Methods

This was a prospective case series study that was performed at the Department of Orthopaedics, Queen Mary Hospital, Hong Kong. Twenty-one symptomatic feet in 16 patients with persistent symptoms of plantar fasciitis despite 3 months of conservative treatment were recruited in November 2008. All patients received five sessions of low energy ESWT and their corresponding 10-point visual analogue scale scores were recorded before and after each treatment sessions for each symptomatic foot. The patients were assessed for up to 6 months post-treatment.

Results

The mean visual analogue scale scores reduction for pain on first step in the morning, daily activities, and heel compression test were 2.62 (44.3%), 3 (38.3%), and 1.6 (36.8%), respectively, post-treatment. The analgesic effect was maintained in 52.3% (n = 11) of the patients at 6 months post treatment.

Conclusion

Low energy ESWT was shown to be an effective outpatient treatment option for patients with plantar fasciitis.

Comparison of different energy densities of extracorporeal shock wave therapy (ESWT) for the management of chronic heel pain

OBJECTIVE

To compare the effectiveness of different energy densities of extracorporeal shock wave therapy (ESWT) for managing chronic heel pain.

DESIGN

A randomized clinical trial.

SETTING

Hospital-based practice.

SUBJECTS

Fifty-seven patients with chronic heel pain were recruited; eight patients withdrew from the study.

INTERVENTIONS

Subjects were randomized into three groups receiving: (1) a 'fixed' energy density, (2) 'maximum tolerable' energy density, or (3) control treatment once a week for three weeks.

OUTCOME MEASURES

Pain on palpation, pain on tension, maximum tolerable walking/standing duration and Foot Function Index were assessed before treatment in each treatment session and at the three-week follow-up.

RESULTS

By week 3, the 'maximum tolerable' energy density group experienced a 66% cumulative reduction in pain from tension, a 65% reduction on palpation and a 112% cumulative increase in maximum tolerable walking/standing duration. The 'fixed' energy density group experienced a 45% cumulative reduction in pain from tension, a 32% reduction in pain on palpation, and a 45% increase in walking/standing tolerance. The 'maximum tolerable' energy density group also showed a significantly greater reduction in Foot Function Index scores than the other two groups. Therapeutic effects were maintained at least up to the three-week follow-up period. The control group had no significant changes in any outcome measures across time periods.

CONCLUSION

The delivery of ESWT with a maximum tolerable energy density is a more effective treatment protocol than a fixed energy density in terms of relieving pain and restoring the functional activity of people suffering from chronic heel pain. The analgesic effects were maintained at least up to the three-week follow-up.

Eccentric loading, shock-wave treatment, or a wait-and-see policy for tendinopathy of the main body of tendo Achillis: a randomized controlled trial

BACKGROUND

Few randomized controlled trials compare different methods of management in chronic tendinopathy of the main body of tendo Achillis.

PURPOSE

To compare the effectiveness of 3 management strategies-group 1, eccentric loading; group 2, repetitive low-energy shock-wave therapy (SWT); and group 3, wait and see-in patients with chronic tendinopathy of the main body of tendo Achillis.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

Seventy-five patients with a chronic recalcitrant (>6 months) noninsertional Achilles tendinopathy were enrolled in a randomized controlled study. All patients had received unsuccessful management for >3 months, including at least (1) peritendinous local injections, (2) nonsteroidal anti-inflammatory drugs, and (3) physiotherapy. A computerized random-number generator was used to draw up an allocation schedule. Analysis was on intention-to-treat basis.

RESULTS

At 4 months from baseline, the Victorian Institute of Sport Assessment (VISA)-A score increased in all groups, from 51 to 76 points in group 1 (eccentric loading), from 50 to 70 points in group 2 (repetitive low-energy SWT), and from 48 to 55 points in group 3 (wait and see). Pain rating decreased in all groups, from 7 to 4 points in group 1, from 7 to 4 points in group 2, and from 8 to 6 points in group 3. Fifteen of 25 patients in group 1 (60%), 13 of 25 patients in group 2 (52%), and 6 of 25 patients in Group 3 (24%) reported a Likert scale of 1 or 2 points ("completely recovered" or "much improved"). For all outcome measures, groups 1 and 2 did not differ significantly. For all outcome measures, groups 1 and 2 showed significantly better results than group 3.

CONCLUSION

At 4-month follow-up, eccentric loading and low-energy SWT showed comparable results. The wait-and-see strategy was ineffective for the management of chronic recalcitrant tendinopathy of the main body of the Achilles tendon.

Immunohistochemical evaluation of substance P and calcitonin gene-related peptide in skin and periosteum after extracorporeal shock wave therapy and radial pressure wave therapy in sheep

OBJECTIVE

To evaluate the effect of focused extracorporeal shock wave therapy (ESWT) and radial pressure wave therapy (RPWT) on immunohistochemical staining for substance P and calcitonin gene-related peptide (CGRP) in the skin and periosteum of sheep.

ANIMALS

36 sheep.

PROCEDURES

All 4 limbs of 36 sheep were treated with ESWT, RPWT, or a sham treatment. For 14 days after treatment, at least 2 sheep were euthanized daily and tissue was harvested for histologic evaluation of nerves via staining for substance P and CGRP in the skin and periosteum.

RESULTS

No effects of ESWT or RPWT were observed on the number of nerves with stain uptake for substance P or CGRP in the skin or periosteum.

CONCLUSIONS AND CLINICAL RELEVANCE

Substance P- and CGRP-containing nerve fibers are not disrupted by EWST or RPWT. Further studies are needed to identify the mechanism of analgesia observed in association with these treatment modalities.

Force platform evaluation of lameness severity following extracorporeal shock wave therapy in horses with unilateral forelimb lameness

OBJECTIVE

To measure alterations in lameness severity that occur following use of extracorporeal shock wave therapy (ESWT) in horses with naturally occurring unilateral forelimb lameness.

DESIGN

Nonrandomized clinical trial.

ANIMALS

9 horses with unilateral forelimb lameness.

PROCEDURES

Force platform gait analysis was performed prior to administration of any treatments (baseline) and after use of local anesthesia to eliminate the lameness. Extracorporeal shock wave therapy was then administered, and gait analysis was repeated 8 hours later and then daily for 7 days.

RESULTS

Compared with the baseline value, peak vertical force was significantly increased 8 hours and 2 days after ESWT, and peak vertical force on day 2 was not significantly different from force measured after use of local anesthesia to eliminate the lameness. Similarly, vertical impulse was significantly increased, compared with the baseline value, 8 hours and 2 days after ESWT, but at all times, it was significantly lower than vertical impulse measured after use of local anesthesia.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that in horses with naturally occurring lameness, use of ESWT results in a period of acute improvement in lameness severity that typically persists for 2 days. Thus, in horses undergoing ESWT, exercise should be controlled for a minimum of 2 days after treatment to prevent further injury.

Second application of low-energy shock waves has a cumulative effect on free nerve endings

Some physicians recommend treating tendinopathies with multiple sessions of shock waves. Some evidence, however, suggests shock wave application can induce nerve fiber degeneration. We questioned whether repeated shock wave application provides a cumulative effect on nerve fibers compared with the effect of one application. One thousand shock wave impulses of an energy flux density of 0.08 mJ/mm were applied to the foot pad of 32 rats. After 14 days, 16 rats received a second application. The foot pads were resected on Days 7, 14, 28, and 42. Sections were processed immunohistochemically using antibodies for sensory nerve. We compared the number of epidermal nerve fibers in rats that received one application of shock waves with the fibers in rats that received two applications. During the first 4 weeks, there was nearly complete degeneration of epidermal nerve fibers in both groups. By the end of 6 weeks, reinnervation of the epidermis began in the single-treatment group. Reinnervation occurred slower in the repeated-treatment group. These data show that a second application has a cumulative effect on nerve fibers. Our data suggest multiple applications of low-energy shock waves might a provide longer-lasting antinociceptive effect.

Evaluation of skin sensitivity after shock wave treatment in horses

OBJECTIVE

To evaluate the effects of shock wave treatment on cutaneous nerve function, compared with the effects of local nerve block and sedation.

ANIMALS

18 clinically sound Swiss Warmbloods.

PROCEDURE

Horses were randomly allocated to 3 groups and received different amounts and types of shock waves (extracorporeal shock wave treatment [ESWT] or radial pressure wave treatment [RPWT]). Horses were sedated with xylazine and levomethadone. Shock waves were applied to the lateral palmar digital nerve at the level of the proximal sesamoid bones on 1 forelimb. Skin sensitivity was evaluated by means of an electrical stimulus at the coronary band before and 5 minutes after sedation and at 4, 24, and 48 hours after application of ESWT or RPWT. On the contralateral forelimb, skin sensitivity was tested before and 10 minutes after an abaxial sesamoid nerve block.

RESULTS

No significant changes in skin sensitivity were detected, regardless of the shock wave protocol applied. Mean reaction thresholds after sedation were more than twice the baseline thresholds. After the abaxial sesamoid block, no reaction was recorded in any of the horses.

CONCLUSIONS AND CLINICAL RELEVANCE

Application of ESWT or RPWT to the palmar digital nerve had no effect on cutaneous sensation distal to the treated region for at least 2 days after application. The analgesic effect of sedation on reaction to electrical stimuli was distinct but varied among horses.

Evaluation of analgesia resulting from extracorporeal shock wave therapy and radial pressure wave therapy in the limbs of horses and sheep

OBJECTIVE

To identify the duration and potential mechanisms of analgesia following extracorporeal shock wave therapy (ESWT) and radial pressure wave therapy (RPWT) in limbs of horses and sheep.

ANIMALS

6 horses and 30 sheep.

PROCEDURE

An electrical stimulus was used to identify the nociceptive threshold for each horse daily for 3 days before treatment (baseline) with ESWT or RPWT, 8 hours after treatment, and at 24-hour intervals for 7 days after treatment. Testing was conducted for the treatment field (midmetacarpus or midmetatarsus) and nerve field (medial and lateral forelimb heel bulbs) distal to a treatment site that included the nerve on the abaxial surface of the proximal sesamoid bone. All 4 limbs of 30 sheep were treated with ESWT, RPWT, or a sham treatment. Two sheep were euthanatized daily and tissue harvested for histologic evaluation of nerves, and concentrations of substance P and calcitonin gene-related peptide were measured in the skin and periosteum.

RESULTS

Values did not differ significantly between baseline and after treatment for the treatment field or nerve field sensation. There was a large difference in the slope when data for horses were plotted for the first 3 days after treatment, compared with the slope for days 4 to 7 after treatment. No differences were found in neuropeptide concentrations after treatment of the sheep, but there was an inflammatory response in the treated nerves.

CONCLUSIONS AND CLINICAL RELEVANCE

A small cutaneous analgesic effect may exist at the treatment site for approximately 3 days after ESWT or RPWT in horses.

Extracorporeal shock wave therapy for calcific and noncalcific tendonitis of the rotator cuff: a systematic review

The authors conducted a systematic review to assess the effectiveness of extracorporeal shock wave therapy (ESWT) for the treatment of calcific and noncalcific tendonitis of the rotator cuff. Conservative treatment for rotator cuff tendonitis includes physiotherapy, nonsteroidal antiinflammatory drugs, and corticosteroid injections. If symptoms persist with conservative treatment, surgery is often considered. Extracorporeal shock wave therapy has been suggested as a treatment alternative for chronic rotator cuff tendonitis, which may decrease the need for surgery. Articles for this review were identified by electronically searching Medline, EMBASE, Cumulative Index to Nursing & Allied Health Literature (CINAHL), and Evidence Based Medicine (EBM) and hand-screening references. Two reviewers selected the trials that met the inclusion criteria, extracted the data, and assessed the methodological quality of the selected trials. Finally, the strength of scientific evidence was appraised. Evidence was classified as strong, moderate, limited, or conflicting. Sixteen trials met the inclusion criteria. There were only five randomized, controlled trials and all involved chronic (>/=3 months) conditions, three for calcific tendonitis and two for noncalcific tendonitis. For randomized, controlled trials, two (40%) were of high quality, one (33%) for calcific tendonitis and one (50%) for noncalcific tendonitis. The 11 nonrandomized trials included nine that involved calcific tendonitis and two that involved both calcific and noncalcific tendonitis. Common problem areas were sample size, randomization, blinding, treatment provider bias, and outcome measures. There is moderate evidence that high-energy ESWT is effective in treating chronic calcific rotator cuff tendonitis when the shock waves are focused at the calcified deposit. There is moderate evidence that low-energy ESWT is not effective for treating chronic noncalcific rotator cuff tendonitis, although this conclusion is based on only one high-quality study, which was underpowered. High-quality randomized, controlled trials are needed with larger sample sizes, better randomization and blinding, and better outcome measures.

Effectiveness of extracorporeal shock wave therapy in the treatment of previously untreated lateral epicondylitis: a randomized controlled trial

BACKGROUND

Extracorporeal shock wave therapy is a relatively new therapy used in the treatment of chronic tendon-related pain. Few randomized controlled trials have been performed on it, and no studies have examined the effectiveness of extracorporeal shock wave therapy as a frontline therapy for tendon-related pain.

HYPOTHESIS

Subjects treated with active extracorporeal shock wave therapy will have higher rates of treatment success than subjects treated with sham extracorporeal shock wave therapy.

DESIGN

Double-blind randomized controlled trial.

METHODS

Sixty subjects who had previously untreated lateral epicondylitis for less than 1 year and more than 3 weeks were included in this study. Subjects were randomly allocated to receive 1 session per week for 3 weeks of either sham or active extra-corporeal shock wave therapy. Subjects in the active therapy group received 2000 pulses (energy flux density, 0.03-0.17 mJ/mm(2)). All subjects were provided with a forearm-stretching program. After 8 weeks of therapy, subjects were classified as either treatment successes or treatment failures according to fulfillment of all 3 criteria: (1) at least a 50% reduction in the overall pain visual analog scale score, (2) a maximum allowable overall pain visual analog scale score of 4.0 cm, and (3) no use of pain medication for elbow pain for 2 weeks before the 8 week follow-up. Visual analog scale scores were also collected for pain at rest, during sleep, during activity, at its worst, and at its least, as well as for quality of life (using the EuroQoL questionnaire) and grip strength.

RESULTS

Success rates in the sham and active therapy groups were 31% and 39%, respectively. No significant difference was detected between groups (chi(2)(1)= 0.3880, P = .533). Mean change in quality of life over 8 weeks was an increase of 1.3 and 3.3 for sham and active therapy groups, respectively, and mean change in grip strength over 8 weeks was an increase of 7.4 kg and 6.8 kg for sham and active therapy groups, respectively.

CONCLUSIONS

Despite improvement in pain scores and pain-free maximum grip strength within groups, there does not appear to be a meaningful difference between treating lateral epicondylitis with extracorporeal shock wave therapy combined with forearm-stretching program and treating with forearm-stretching program alone, with respect to resolving pain within an 8-week period of commencing treatment.

Application of shock waves to rat skin decreases calcitonin gene-related peptide immunoreactivity in dorsal root ganglion neurons

There have been several reports on the use of extracorporeal shock waves in the treatment of pseudarthrosis, calcifying tendinitis, and tendinopathies of the elbow. However, the pathomechanism of pain relief has not been clarified. To investigate the analgesic properties of shock wave application, we analyzed changes in calcitonin gene-related peptide (CGRP)-immunoreactive (ir) dorsal root ganglion (DRG) neurons. In the nontreated group, fluorogold-labeled dorsal root ganglion neurons innervating the most middle foot pad of hind paw were distributed in the L4 and L5 dorsal root ganglia. Of these neurons, 61% were CGRP-ir. However, in the shock wave-treated group, the percentage of FG-labeled CGRP-ir DRG neurons decreased to 18%. These data show that relief of clinical pain after shock wave application may result from reduced CGRP expression in DRG neurons.

The influence of local steroid injections, body weight and the length of symptoms in the treatment of painful subcalcaneal spurs with extracorporeal shock wave therapy

OBJECTIVE

To evaluate the effectiveness of extracorporeal shock wave therapy (ESWT) for the treatment of painful subcalcaneal spurs and evaluate whether local steroid injections, body weight and the length of symptoms can affect the clinical results.

DESIGN

Subjects were selected through clinical examination and heel radiograms according to diagnosis of painful subcalcaneal spurs.

SUBJECTS

Sixty-four subjects were divided into two groups of treatment depending on their past history of previous local steroid injections.

INTERVENTIONS

Each subject received a three-session ESWT (performed weekly). A rehabilitative programme was instituted, consisting of self-assisted plantar fascia and plantar flexors stretching exercises.

MAIN OUTCOME MEASURES

The Mayo Clinical Scoring System (MCSS) was utilized to evaluate each subject before the treatment and at two- and ten-month follow-ups. In addition, standard radiograms were done both before the treatment and at the ten-month follow-up.

RESULTS

Patients with no past treatment using steroids did not show any statistically significant improvement of the MCSS at the two-month follow-up. The statistical significance was obtained at the ten-month follow-up. Patients with past treatment using steroids did not show any statistically significant improvement of the MCSS at either follow-up. At the radiogram check, none of the subjects showed any modification of the heel spurs.

CONCLUSIONS

According to the results of the present study ESWT should be considered as an effective treatment for painful subcalcaneal spurs. Previous local steroid injections may negatively affect the result of ESWT.

Extracorporeal shock wave therapy in the treatment of lateral epicondylitis : a randomized multicenter trial

BACKGROUND

On the basis of observational trials, numerous investigators have recommended extracorporeal shock wave therapy as an alternative treatment for chronic lateral epicondylitis of the elbow. However, there has been no evidence of its efficacy from well-designed randomized clinical trials. The objective of this study was to find out whether extracorporeal shock wave therapy in combination with local anesthesia was superior to placebo therapy in combination with local anesthesia.

METHODS

A randomized multicenter trial with a parallel-group design was conducted. Following administration of local anesthesia, either extracorporeal shock wave therapy with three treatments of 2000 pulses each and a positive energy flux density (ED+) of 0.07 to 0.09 mJ/mm (2) or placebo therapy was applied on an outpatient basis. Treatment allocation was blinded for patients and for observers. The primary end point was based on the rate of success, as determined with the Roles and Maudsley score and whether additional treatment was required, twelve weeks after the intervention. Crossover was possible after assessment of the primary end point. Secondary end points were the Roles and Maudsley score, subjective pain rating, and grip strength after six and twelve weeks and after twelve months. The planned number of 272 patients was included in the study.

RESULTS

The primary end point could be assessed for 90.8% of the patients. The success rate was 25.8% in the group treated with extracorporeal shock wave therapy and 25.4% in the placebo group, a difference of 0.4% with a 95% confidence interval of -10.5% to 11.3%. Similarly, there was no relevant difference between groups with regard to the secondary end points. Improvement was observed in two-thirds of the patients from both groups twelve months after the intervention. Few side effects were reported.

CONCLUSIONS

Extracorporeal shock wave therapy as applied in the present study was ineffective in the treatment of lateral epicondylitis. The previously reported success of this therapy appears to be attributable to inappropriate study designs. Different application protocols might improve clinical outcome. We recommend that extracorporeal shock wave therapy be applied only in high-quality clinical trials until it is proved to be effective.

No influence of low-energy extracorporeal shock wave therapy (ESWT) on spinal nociceptive systems

The analgesic effects of high-energy extracorporeal shock wave therapy (ESWT) were discovered by chance during its application for urolithiasis and for bone pseudarthrosis. Despite the extensive use of ESWT, the mechanisms of its antinociceptive effects are still unclear. A gate control mechanism and other antinociceptive mechanisms have been postulated. The aim of this study was to investigate the possible influence of low-energy ESWT on the expression of the transmitters substance P (SP) and calcitonin gene-related peptide (CGRP) in the lumbar spinal cord of the rat. Immunohistochemical analysis of the expression of the neuropeptides CGRP and SP was performed in rats treated either once with 1000 impulses or three times with 1000 impulses, with two different energy flux densities being used (0.043 and 0.11 mJ/mm2). The animals were killed either 4 or 72 h after the ESWT. No regulatory effect of ESWT on the expression of SP or CGRP in the dorsal horns was found. Because the application of ESWT showed no significant changes in the sensory system, it is unlikely that the application of ESWT triggers the endogenous pain control system of the rat through hyperstimulation analgesia. Furthermore, these results show that low-energy ESWT had no side effects on the rat spinal cord.