Impaired tensile strength after shock-wave application in an animal model of tendon calcification

Effect of Extracorporeal Shockwave Therapy on Passive Ankle Stiffness in Patients With Plantar Fasciopathy

Plantar fasciopathy (PF) is the most common cause of heel pain. Extracorporeal shockwave therapy (ESWT) improves the gait pattern in patients with PF. However, the effects of ESWT on the biomechanics of the ankle in these patients remains unclear. Sixteen participants were included in the present study. Of the 16 participants, 8 patients with PF were assigned to receive extracorporeal shockwave therapy, and 8 healthy participants served as an external control group. ESWT was applied to the PF group for 1500 pulses at an energy flux of 0.26 mJ/mm² every 3 weeks for 3 sessions. The biomechanics of the ankle joints were then assessed using an isokinetic dynamometer, and a health-related quality of life questionnaire was administered at baseline and at the final follow-up session 12 weeks after the initial treatment. Passive stiffness was calculated and compared between the foot affected with PF, the opposite foot, and both feet of those in the healthy control group. The Kruskal-Wallis 1-way analysis of variance with repeated measures was performed, and statistical significance was considered present at the 5% (p ≤ .05) level. Ankle dorsiflexion in the affected limb increased from 14° ± 3° to 17° ± 2° after ESWT (p < .05). No statistically significant differences were noted in the strength of dorsiflexion or plantarflexion at baseline and after ESWT. However, a statistically significant increase in the ratio of strength in ankle dorsiflexion versus plantarflexion was found after ESWT (p < .05). No differences in the passive stiffness of the ankle joint were demonstrated. Patients reported an improved physical function score after ESWT (p < .05). An increased dorsiflexion/plantarflexion torque ratio and maximal dorsiflexion associated with decreased pain might contribute to the improved physical function after ESWT for PF.

In-vitro cell treatment with focused shockwaves-influence of the experimental setup on the sound field and biological reaction

Background

To improve understanding of shockwave therapy mechanisms, in vitro experiments are conducted and the correlation between cell reaction and shockwave parameters like the maximum pressure or energy density is studied. If the shockwave is not measured in the experimental setup used, it is usually assumed that the device’s shockwave parameters (=manufacturer’s free field measurements) are valid. But this applies only for in vitro setups which do not modify the shockwave, e.g., by reflection or refraction. We hypothesize that most setups used for in vitro shockwave experiments described in the literature influence the sound field significantly so that correlations between the physical parameters and the biological reaction are not valid.

Methods

To reveal the components of common shockwave in vitro setups which mainly influence the sound field, 32 publications with 37 setups used for focused shockwave experiments were reviewed and evaluated regarding cavitation, cell container material, focal sound field size relative to cell model size, and distance between treated cells and air. For further evaluation of the severity of those influences, experiments and calculations were conducted.

Results

In 37 setups, 17 different combinations of coupling, cell container, and cell model are described. The setup used mainly is a transducer coupled via water to a tube filled with a cell suspension. As changes of the shockwaves’ maximum pressure of 11 % can already induce changes of the biological reaction, the sound field and biological reactions are mainly disturbed by use of standard cell containers, use of coupling gel, air within the 5 MPa focal zone, and cell model sizes which are bigger than half the −6 dB focal dimensions.

Conclusions

Until now, correct and sufficient information about the shockwave influencing cells in vitro is only provided in 1 of 32 publications. Based on these findings, guidelines for improved in vitro setups are proposed which help minimize the influence of the setup on the sound field.

Electronic supplementary material

The online version of this article (doi:10.1186/s40349-016-0053-z) contains supplementary material, which is available to authorized users.

Clinical application of extracorporeal shock wave therapy in orthopedics: focused versus unfocused shock waves

For the past decade extracorporeal shock wave therapy has been applied to a wide range of musculoskeletal disorders. The many promising results and the introduction of shock wave generators that are less expensive and easier to handle has added to the growing interest. Based on their nature of propagation, shock waves can be divided into two types: focused and unfocused. Although several physical differences between these different types of shock waves have been described, very little is known about the clinical outcome using these different modalities. The aim of the present review is to investigate differences in outcome in select orthopaedic applications using focused and unfocused shock waves.

Mechanisms of primary blast-induced traumatic brain injury: insights from shock-wave research

Traumatic brain injury caused by explosive or blast events is traditionally divided into four phases: primary, secondary, tertiary, and quaternary blast injury. These phases of blast-induced traumatic brain injury (bTBI) are biomechanically distinct and can be modeled in both in vivo and in vitro systems. The primary bTBI injury phase represents the response of brain tissue to the initial blast wave. Among the four phases of bTBI, there is a remarkable paucity of information about the cause of primary bTBI. On the other hand, 30 years of research on the medical application of shockwaves (SW) has given us insight into the mechanisms of tissue and cellular damage in bTBI, including both air-mediated and underwater SW sources. From a basic physics perspective, the typical blast wave consists of a lead SW followed by supersonic flow. The resultant tissue injury includes several features observed in bTBI, such as hemorrhage, edema, pseudoaneurysm formation, vasoconstriction, and induction of apoptosis. These are well-described pathological findings within the SW literature. Acoustic impedance mismatch, penetration of tissue by shock/bubble interaction, geometry of the skull, shear stress, tensile stress, and subsequent cavitation formation, are all important factors in determining the extent of SW-induced tissue and cellular injury. Herein we describe the requirements for the adequate experimental set-up when investigating blast-induced tissue and cellular injury; review SW physics, research, and the importance of engineering validation (visualization/pressure measurement/numerical simulation); and, based upon our findings of SW-induced injury, discuss the potential underlying mechanisms of primary bTBI.

Extracorporeal shock wave therapy in the treatment of chronic tendinopathies

Many clinical trials have evaluated the use of extracorporeal shock wave therapy for treating patients with chronic tendinosis of the supraspinatus, lateral epicondylitis, and plantar fasciitis. Although extracorporeal shock wave therapy has been reported to be effective in some trials, in others it was no more effective than placebo. The multiple variables associated with this therapy, such as the amount of energy delivered, the method of focusing the shock waves, frequency and timing of delivery, and whether or not anesthetics are used, makes comparing clinical trials difficult. Calcific tendinosis of the supraspinatus and plantar fasciitis have been successfully managed with extracorporeal shock wave therapy when nonsurgical management has failed. Results have been mixed in the management of lateral epicondylitis, however, and this therapy has not been effective in managing noncalcific tendinosis of the supraspinatus. Extracorporeal shock wave therapy has consistently been more effective with patient feedback, which enables directing the shock waves to the most painful area (clinical focusing), rather than with anatomic or image-guided focusing, which are used to direct the shock wave to an anatomic landmark or structure.

[New bone formation by extracorporeal shock waves. Dependence of induction on energy flux density]

BACKGROUND

The purpose of this study was to test the hypothesis that shock waves can induce new bone formation even without cortical fractures and periosteal detachment as suggested in the literature.

METHODS

Extracorporeal shock waves with energy flux densities between 0 mJ/mm(2) (sham treatment) and 1.2 mJ/mm(2) were applied in vivo to the distal femoral region of rabbits (1500 pulses at 1 Hz frequency each). Oxytetracycline was injected on days 5-9 and the animals were sacrificed on day 10. Sections of both femora of all animals were investigated with broadband fluorescence microscopy and contact microradiography for new periosteal and endosteal bone, periosteal detachment, cortical fractures, and trabecular bone with callus.

RESULTS

Shock waves with energy flux densities of 0.9 mJ/mm(2) and 1.2 mJ/mm(2) resulted in new periosteal bone formation in the presence of cortical fractures and periosteal detachment. After application of shock waves with energy flux density of 0.5 mJ/mm(2), clearly detectable signs of new periosteal bone formation were observed without cortical fractures or periosteal detachment.

CONCLUSIONS

The results of this study challenge the current view in the literature that the creation of cortical fractures and periosteal detachment are prerequisites for new bone formation mediated by extracorporeal shock waves.

Extracorporeal shock waves promote healing of collagenase-induced Achilles tendinitis and increase TGF-beta1 and IGF-I expression

Extracorporeal shock waves (ESW) have recently been used in resolving tendinitis. However, mechanisms by which ESW promote tendon repair is not fully understood. In this study, we reported that an optimal ESW treatment promoted healing of Achilles tendintis by inducing TGF-beta1 and IGF-I. Rats with the collagenease-induced Achilles tendinitis were given a single ESW treatment (0.16 mJ/mm(2) energy flux density) with 0, 200, 500 and 1000 impulses. Achilles tendons were subjected to biomechanical (load to failure and stiffness), biochemical properties (DNA, glycosaminoglycan and hydroxyproline content) and histological assessment. ESW with 200 impulses restored biomechanical and biochemical characteristics of healing tendons 12 weeks after treatment. However, ESW treatments with 500 and 1000 impulses elicited inhibitory effects on tendinitis repair. Histological observation demonstrated that ESW treatment resolved edema, swelling, and inflammatory cell infiltration in injured tendons. Lesion site underwent intensive tenocyte proliferation, neovascularization and progressive tendon tissue regeneration. Tenocytes at the hypertrophied cellular tissue and newly developed tendon tissue expressed strong proliferating cell nuclear antigen (PCNA) after ESW treatment, suggesting that physical ESW could increase the mitogenic responses of tendons. Moreover, the proliferation of tenocytes adjunct to hypertrophied cell aggregate and newly formed tendon tissue coincided with intensive TGF-beta1 and IGF-I expression. Increasing TGF-beta1 expression was noted in the early stage of tendon repair, and elevated IGF-I expression was persisted throughout the healing period. Together, low-energy shock wave effectively promoted tendon healing. TGF-beta1 and IGF-I played important roles in mediating ESW-stimulated cell proliferation and tissue regeneration of tendon.

The effects of extracorporeal shock-wave therapy on the ultrasonographic and histologic appearance of collagenase-induced equine forelimb suspensory ligament desmitis

Extracorporeal shock-wave therapy (ESWT) may stimulate healing of desmitis in multiple species. The objective of this study was to evaluate the ultrasonographic and histologic appearance of collagenase-induced suspensory ligament (SUL) desmitis in untreated ligaments and ligaments treated with ESWT in horses. Four mature horses had SUL desmitis induced in both forelimbs. Beginning 3 weeks after induction of the lesions, one ligament per horse was treated 3 times at 3-week intervals with ESWT. The percent lesion, echogenicity and fiber alignment scores of the SULs were evaluated at 3-week intervals for a total of 15 weeks. At the completion of the study, the horses were euthanized and the SULs collected, fixed and processed for histopathologic evaluation. Ultrasonography showed treated SULs had a smaller percent lesion at the maximal injury zone (p = 0.001), and the total percent lesion (p = 0.01), total fiber alignment score (p = 0.0167) and total echogenicity (p = 0.0023) were all smaller in the treated ligaments. The fiber alignment score and echogenicity were not statistically different at the maximal injury zone. The treated SULs had a more concentrated area of metachromasia associated with healing than the untreated ligaments, where metachromasia appeared more diffuse throughout the ligament. ESWT improved the rate of healing as assessed ultrasonographically.