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Chu Kwan W, Partanen A, Narayanan U, Waspe AC, Drake JM. Biomechanical testing of ex vivo porcine tendons following high intensity focused ultrasound thermal ablation. PLoS One 2024; 19:e0302778. [PMID: 38713687 DOI: 10.1371/journal.pone.0302778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2024] [Accepted: 04/12/2024] [Indexed: 05/09/2024] Open
Abstract
INTRODUCTION Magnetic resonance-guided focused ultrasound (MRgFUS) has been demonstrated to be able to thermally ablate tendons with the aim to non-invasively disrupt tendon contractures in the clinical setting. However, the biomechanical changes of tendons permitting this disrupting is poorly understood. We aim to obtain a dose-dependent biomechanical response of tendons following magnetic resonance-guided focused ultrasound (MRgFUS) thermal ablation. METHODS Ex vivo porcine tendons (n = 72) were embedded in an agar phantom and randomly assigned to 12 groups based on MRgFUS treatment. The treatment time was 10, 20, or 30s, and the applied acoustic power was 25, 50, 75, or 100W. Following each MRgFUS treatment, tendons underwent biomechanical tensile testing on an Instron machine, which calculated stress-strain curves during tendon elongation. Rupture rate, maximum treatment temperature, Young's modulus and ultimate strength were analyzed for each treatment energy. RESULTS The study revealed a dose-dependent response, with tendons rupturing in over 50% of cases when energy delivery exceeded 1000J and 100% disruption at energy levels beyond 2000J. The achieved temperatures during MRgFUS were directly proportional to energy delivery. The highest recorded temperature was 56.8°C ± 9.34 (3000J), while the lowest recorded temperate was 18.6°C ± 0.6 (control). The Young's modulus was highest in the control group (47.3 MPa ± 6.5) and lowest in the 3000J group (13.2 MPa ± 5.9). There was no statistically significant difference in ultimate strength between treatment groups. CONCLUSION This study establishes crucial thresholds for reliable and repeatable disruption of tendons, laying the groundwork for future in vivo optimization. The findings prompt further exploration of MRgFUS as a non-invasive modality for tendon disruption, offering hope for improved outcomes in patients with musculotendinous contractures.
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Affiliation(s)
| | | | - Unni Narayanan
- The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Adam C Waspe
- The Hospital for Sick Children, Toronto, Ontario, Canada
| | - James M Drake
- The Hospital for Sick Children, Toronto, Ontario, Canada
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Khandare S, Smallcomb M, Elliott J, Vidt ME, Simon JC. Focused ultrasound as an alternative to dry needling for the treatment of tendinopathies: A murine model. J Orthop Res 2024; 42:598-606. [PMID: 37804211 DOI: 10.1002/jor.25700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 05/26/2023] [Accepted: 10/05/2023] [Indexed: 10/09/2023]
Abstract
Tendinopathies account for 30% of 102 million annual musculoskeletal injuries occurring annually in the United States. Current treatments, like dry needling, induce microdamage to promote healing but produce mixed success rates. Previously, we showed focused ultrasound can noninvasively create microdamage while preserving mechanical properties in ex vivo murine tendons. This present study compared growth factor, histological, and mechanical effects after focused ultrasound or dry needling treatments in an in vivo murine tendon injury model. Partial Achilles tenotomy was performed in 26 rats. One-week postsurgery, tendons were treated with focused ultrasound (1.5 MHz, 1-ms pulses at 10 Hz for 106 s, p+ = 49 MPa, p- = 19 MPa) or dry needling (30 G needle, 5 fenestrations over 20 s) and survived for 1 additional week. Blood was collected immediately before and after treatment and before euthanasia; plasma was assayed for growth factors. Treated tendons and contralateral controls were harvested for histology or mechanical testing. No differences were found between treatments in release of insulin growth factor 1 and transforming growth factor beta; vascular endothelial growth factor A concentrations were too low for detection. Histologically, focused ultrasound and dry needling tendons displayed localized fibroblast infiltration without collagen proliferation with no detectable differences between treatments. Mechanically, stiffness and percent relaxation of dry needling tendons were lower than controls (p = 0.0041, p = 0.0441, respectively), whereas stiffness and percent relaxation of focused ultrasound tendons were not different from controls. These results suggest focused ultrasound should be studied further to determine how this modality can be leveraged as a therapy for tendinopathies.
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Affiliation(s)
- Sujata Khandare
- Biomedical Engineering, Pennsylvania State University, University Park, Pennsylvania, USA
| | - Molly Smallcomb
- Graduate Program in Acoustics, Pennsylvania State University, University Park, Pennsylvania, USA
| | - Jacob Elliott
- Graduate Program in Acoustics, Pennsylvania State University, University Park, Pennsylvania, USA
| | - Meghan E Vidt
- Biomedical Engineering, Pennsylvania State University, University Park, Pennsylvania, USA
- Physical Medicine and Rehabilitation, Penn State College of Medicine, Hershey, Pennsylvania, USA
| | - Julianna C Simon
- Biomedical Engineering, Pennsylvania State University, University Park, Pennsylvania, USA
- Graduate Program in Acoustics, Pennsylvania State University, University Park, Pennsylvania, USA
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Bader KB, Flores Basterrechea K, Hendley SA. In silico assessment of histotripsy-induced changes in catheter-directed thrombolytic delivery. Front Physiol 2023; 14:1225804. [PMID: 37449013 PMCID: PMC10336328 DOI: 10.3389/fphys.2023.1225804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 06/19/2023] [Indexed: 07/18/2023] Open
Abstract
Introduction: For venous thrombosis patients, catheter-directed thrombolytic therapy is the standard-of-care to recanalize the occluded vessel. Limitations with thrombolytic drugs make the development of adjuvant treatments an active area of research. One potential adjuvant is histotripsy, a focused ultrasound therapy that lyses red blood cells within thrombus via the spontaneous generation of bubbles. Histotripsy has also been shown to improve the efficacy of thrombolytic drugs, though the precise mechanism of enhancement has not been elucidated. In this study, in silico calculations were performed to determine the contribution of histotripsy-induced changes in thrombus diffusivity to alter catheter-directed therapy. Methods: An established and validated Monte Carlo calculation was used to predict the extent of histotripsy bubble activity. The distribution of thrombolytic drug was computed with a finite-difference time domain (FDTD) solution of the perfusion-diffusion equation. The FDTD calculation included changes in thrombus diffusivity based on outcomes of the Monte Carlo calculation. Fibrin degradation was determined using the known reaction rate of thrombolytic drug. Results: In the absence of histotripsy, thrombolytic delivery was restricted in close proximity to the catheter. Thrombolytic perfused throughout the focal region for calculations that included the effects of histotripsy, resulting in an increased degree of fibrinolysis. Discussion: These results were consistent with the outcomes of in vitro studies, suggesting histotripsy-induced changes in the thrombus diffusivity are a primary mechanism for enhancement of thrombolytic drugs.
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Affiliation(s)
- Kenneth B. Bader
- Department of Radiology, University of Chicago, Chicago, IL, United States
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Smallcomb M, Simon JC. Dual-frequency boiling histotripsy in an ex vivo bovine tendinopathy model. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2023; 153:3182. [PMID: 37279386 PMCID: PMC10247224 DOI: 10.1121/10.0019630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 04/19/2023] [Accepted: 05/16/2023] [Indexed: 06/08/2023]
Abstract
Histotripsy fractionates most soft tissues; however, healthy tendons have shown resistance to histotripsy fractionation. Prior work has shown that pre-heating tendons increases susceptibility to histotripsy fractionation; combining multiple driving frequencies may also allow successful fractionation of tendons. Here, we evaluate single- and dual-frequency histotripsy in four healthy and eight tendinopathic ex vivo bovine tendons. First, we evaluated single-frequency (1.07, 1.5, and 3.68 MHz) and dual-frequency (1.07 and 1.5 MHz or 1.5 and 3.68 MHz) bubble dynamics with high-speed photography in a tissue-mimicking phantom. Then, tendons were treated with histotripsy. Cavitation activity was monitored with a passive cavitation detector (PCD) and targeted areas were evaluated grossly and histologically. Results in tendinopathic tendons showed 1.5 MHz or 3.68 MHz single-frequency exposure caused focal disruption, whereas 1.5 and 3.68 MHz dual-frequency exposures caused fractionated holes; all treatments caused some thermal denaturation. Exposure to 1.07 MHz alone or combined with 1.5 MHz did not show fractionation in tendinopathic tendons. In healthy tendons, only thermal necrosis was observed for all tested exposures. PCD showed some differences in cavitation activity in tendinopathic tendons but did not predict successful fractionation. These results suggest that full histotripsy fractionation is possible using dual-frequency exposures in tendinopathic tendons.
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Affiliation(s)
- Molly Smallcomb
- Graduate Program in Acoustics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Julianna C Simon
- Graduate Program in Acoustics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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Tang J, Tang J, Li H, Zhou J, Tang N, Zhu Q, Wang X, Zhu B, Li N, Liu Z. Mechanical destruction using a minimally invasive Ultrasound Needle induces anti-tumor immune responses and synergizes with the anti-PD-L1 blockade. Cancer Lett 2023; 554:216009. [PMID: 36400312 DOI: 10.1016/j.canlet.2022.216009] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 11/09/2022] [Accepted: 11/10/2022] [Indexed: 11/17/2022]
Abstract
Immune checkpoint inhibitors (ICIs) have been widely used in treating various tumors; however, the objective response rate of ICIs is less than 40%. In this study, we attempted to induce anti-tumor immune responses using an improved ultrasonic horn device, Ultrasound Needle (UN). We tested its synergistic anti-tumor efficacy with an anti-PD-L1 antibody in a mouse tumor model. Under different parameters, UN treatment selectively induced mechanical destruction and thermal ablation effects on tumor tissues. The mechanical destruction effect of UN treatment increased the infiltration of CD8+ T cells in tumors and relieved the immunosuppressive tumor microenvironment. It also induced systemic anti-tumor immune responses and enhanced the therapeutic efficacy of the anti-PD-L1 antibody in both local and abscopal tumors. The mechanical destruction effect of UN treatment resulted in the release of damage-associated molecular patterns and promoted dendritic cells (DCs)-based antigen presentation. Depletion of DCs or CD8+ T cells eliminated the anti-tumor immune responses induced by UN treatment and weakened the synergistic anti-tumor efficacy with anti-PD-L1 antibody. Therefore, minimally invasive UN may provide a new therapeutic modality for ultrasound-assisted immunotherapy.
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Affiliation(s)
- Jiawei Tang
- Department of Ultrasound, Xinqiao Hospital, Army Medical University (Third Military Medical University), Chongqing, China
| | - Junhui Tang
- Department of Ultrasound, Xinqiao Hospital, Army Medical University (Third Military Medical University), Chongqing, China
| | - Hui Li
- Department of Ultrasound, Xinqiao Hospital, Army Medical University (Third Military Medical University), Chongqing, China
| | - Jing Zhou
- Institute of Immunology, PLA, Third Military Medical University, Chongqing, China
| | - Najiao Tang
- Zhongshan Hospital (Xiamen), Fudan University, Xiamen, China
| | - Qiong Zhu
- Department of Ultrasound, Xinqiao Hospital, Army Medical University (Third Military Medical University), Chongqing, China
| | - Xinxin Wang
- Institute of Cancer, Xinqiao Hospital, Third Military Medical University, Chongqing, China; Chongqing Key Laboratory of Immunotherapy, Chongqing, China
| | - Bo Zhu
- Institute of Cancer, Xinqiao Hospital, Third Military Medical University, Chongqing, China; Chongqing Key Laboratory of Immunotherapy, Chongqing, China
| | - Ningshan Li
- Department of Ultrasound, Xinqiao Hospital, Army Medical University (Third Military Medical University), Chongqing, China.
| | - Zheng Liu
- Department of Ultrasound, Xinqiao Hospital, Army Medical University (Third Military Medical University), Chongqing, China.
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Williams RP, Simon JC, Khokhlova VA, Sapozhnikov OA, Khokhlova TD. The histotripsy spectrum: differences and similarities in techniques and instrumentation. Int J Hyperthermia 2023; 40:2233720. [PMID: 37460101 PMCID: PMC10479943 DOI: 10.1080/02656736.2023.2233720] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 06/15/2023] [Accepted: 07/02/2023] [Indexed: 07/20/2023] Open
Abstract
Since its inception about two decades ago, histotripsy - a non-thermal mechanical tissue ablation technique - has evolved into a spectrum of methods, each with distinct potentiating physical mechanisms: intrinsic threshold histotripsy, shock-scattering histotripsy, hybrid histotripsy, and boiling histotripsy. All methods utilize short, high-amplitude pulses of focused ultrasound delivered at a low duty cycle, and all involve excitation of violent bubble activity and acoustic streaming at the focus to fractionate tissue down to the subcellular level. The main differences are in pulse duration, which spans microseconds to milliseconds, and ultrasound waveform shape and corresponding peak acoustic pressures required to achieve the desired type of bubble activity. In addition, most types of histotripsy rely on the presence of high-amplitude shocks that develop in the pressure profile at the focus due to nonlinear propagation effects. Those requirements, in turn, dictate aspects of the instrument design, both in terms of driving electronics, transducer dimensions and intensity limitations at surface, shape (primarily, the F-number) and frequency. The combination of the optimized instrumentation and the bio-effects from bubble activity and streaming on different tissues, lead to target clinical applications for each histotripsy method. Here, the differences and similarities in the physical mechanisms and resulting bioeffects of each method are reviewed and tied to optimal instrumentation and clinical applications.
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Affiliation(s)
- Randall P Williams
- Division of Gastroenterology, Department of Medicine, University of Washington, Seattle, WA, USA
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, WA, USA
| | - Julianna C Simon
- Graduate Program in Acoustics, The Pennsylvania State University, University Park, PA, USA
| | - Vera A Khokhlova
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, WA, USA
- Department of Acoustics, Physics Faculty, Moscow State University, Moscow, Russia
| | - Oleg A Sapozhnikov
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, WA, USA
- Department of Acoustics, Physics Faculty, Moscow State University, Moscow, Russia
| | - Tatiana D Khokhlova
- Division of Gastroenterology, Department of Medicine, University of Washington, Seattle, WA, USA
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, WA, USA
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Simon A, Robinson F, Anzivino A, Boyer M, Hendricks-Wenger A, Guilliams D, Casey J, Grider D, Valea F, Vlaisavljevich E. Histotripsy for the Treatment of Uterine Leiomyomas: A Feasibility Study in Ex Vivo Uterine Fibroids. ULTRASOUND IN MEDICINE & BIOLOGY 2022; 48:1652-1662. [PMID: 35641394 DOI: 10.1016/j.ultrasmedbio.2022.04.214] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 04/01/2022] [Accepted: 04/22/2022] [Indexed: 06/15/2023]
Abstract
Uterine fibroids (leiomyomas), the most common benign tumors in women of reproductive age, are a frequent cause of abnormal vaginal bleeding and other reproductive complaints among women. This study investigates the feasibility of using histotripsy, a non-invasive, non-thermal focused ultrasound ablation method, to ablate uterine fibroids. Human fibroid samples (n = 16) were harvested after hysterectomy or myomectomy procedures at Carilion Memorial Hospital. Histotripsy was applied to ex vivo fibroids in two sets of experiments using a 700-kHz clinical transducer to apply multicycle histotripsy pulses and a prototype 500-kHz transducer to apply single-cycle histotripsy pulses. Ultrasound imaging was used for real-time treatment monitoring, and post-treatment ablation was quantified histologically using hematoxylin and eosin and Masson trichrome stains. Results revealed that multicycle histotripsy generated diffuse cavitation in targeted fibroids, with minimal cellular ablative changes after treatment with 2000 pulses/point. Single-cycle pulsing generated well-confined bubble clouds with evidence of early coagulative necrosis on histological assessment in samples treated with 2000 pulses/point, near-complete ablation in samples treated with 4000 pulses/point and complete tissue destruction in samples treated with 10,000 pulses/point. This study illustrates that histotripsy is capable of fibroid ablation under certain pulsing parameters and warrants further investigation as an improved non-invasive ablation method for the treatment of leiomyomas.
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Affiliation(s)
- Alex Simon
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, Virginia, USA
| | - Faith Robinson
- Virginia Tech Carilion School of Medicine, Roanoke, Virginia, USA
| | - Anthony Anzivino
- Virginia Tech Carilion School of Medicine, Roanoke, Virginia, USA
| | - Maggie Boyer
- Department of Biological Systems Engineering, Virginia Tech, Blacksburg, Virginia, USA
| | - Alissa Hendricks-Wenger
- Department of Translational Biology, Medicine and Health, Virginia Tech, Blacksburg, VA, USA
| | - Danielle Guilliams
- Department of Research and Development, Carilion Clinic, Roanoke, Virginia, USA
| | - James Casey
- Virginia Tech Carilion School of Medicine, Roanoke, Virginia, USA; Department of Obstetrics and Gynecology, Carilion Clinic Gynecological Oncology, Roanoke, Virginia, USA
| | - Douglas Grider
- Virginia Tech Carilion School of Medicine, Roanoke, Virginia, USA; Dominion Pathology Associates, Roanoke, Virginia, USA
| | - Fidel Valea
- Virginia Tech Carilion School of Medicine, Roanoke, Virginia, USA; Department of Obstetrics and Gynecology, Carilion Clinic Gynecological Oncology, Roanoke, Virginia, USA
| | - Eli Vlaisavljevich
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, Virginia, USA.
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Arrizabalaga JH, Smallcomb M, Abu-Laban M, Liu Y, Yeingst TJ, Dhawan A, Simon JC, Hayes DJ. Ultrasound-Responsive Hydrogels for On-Demand Protein Release. ACS APPLIED BIO MATERIALS 2022; 5:3212-3218. [PMID: 35700312 PMCID: PMC10496416 DOI: 10.1021/acsabm.2c00192] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The development of tunable, ultrasound-responsive hydrogels that can deliver protein payload on-demand when exposed to focused ultrasound is described in this study. Reversible Diels-Alder linkers, which undergo a retro reaction when stimulated with ultrasound, were used to cross-link chitosan hydrogels with entrapped FITC-BSA as a model protein therapeutic payload. Two Diels-Alder linkage compositions with large differences in the reverse reaction energy barriers were compared to explore the influence of linker composition on ultrasound response. Selected physicochemical properties of the hydrogel construct, its basic degradation kinetics, and its cytocompatibility were measured with respect to Diels-Alder linkage composition. Focused ultrasound initiated the retro Diels-Alder reaction, controlling the release of the entrapped payload while also allowing for real-time visualization of the ongoing process. Additionally, increasing the focused ultrasound amplitude and time correlated with an increased rate of protein release, indicating stimuli responsive control.
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Affiliation(s)
- Julien H Arrizabalaga
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Molly Smallcomb
- Graduate Program in Acoustics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Mohammad Abu-Laban
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Yiming Liu
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Tyus J Yeingst
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Aman Dhawan
- Department of Orthopaedics and Rehabilitation, Penn State College of Medicine, Milton S. Hershey Medical Center, Hershey, Pennsylvania 17033, United States
| | - Julianna C Simon
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Graduate Program in Acoustics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Daniel J Hayes
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Materials Research Institute, Millennium Science Complex, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- The Huck Institute of the Life Sciences, Millennium Science Complex, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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Effects of focused ultrasound and dry needling on tendon mechanical properties. J Biomech 2022; 132:110934. [PMID: 34995989 PMCID: PMC8860888 DOI: 10.1016/j.jbiomech.2021.110934] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 12/11/2021] [Accepted: 12/18/2021] [Indexed: 02/03/2023]
Abstract
Tendon injuries are extremely common, resulting in mechanically weaker tendons that could lead to tendon rupture. Dry needling (DN) is widely used to manage pain and function after injury. However, DN is invasive and high inter-practitioner variability has led to mixed success rates. Focused ultrasound (fUS) is a non-invasive medical technology that directs ultrasound energy into a well-defined focal volume. fUS can induce thermal ablation or mechanical fractionation, with bioeffect type controlled through ultrasound parameters. Tendons must withstand high physiological loads, thus treatments maintaining tendon mechanical properties while promoting healing are needed. Our objective was to evaluate mechanical effects of DN and 3 fUS parameter sets, chosen to prioritize mechanical fractionation, on Achilles and supraspinatus tendons. Ex vivo rat Achilles and supraspinatus tendons (50 each) were divided into sham, DN, fUS-1, fUS-2, and fUS-3 (n = 10/group). Following treatment, tendons were mechanically tested. Elastic modulus of supraspinatus tendons treated with DN (126.64 ± 28.1 MPa) was lower than sham (153.02 ± 29.3 MPa; p = 0.0280). Stiffness and percent relaxation of tendons treated with DN (Achilles: 114.40 ± 31.6 N/mm; 49.10 ± 6.1%; supraspinatus: 109.53 ± 30.8 N/mm; 50.17 ± 7.6%) were lower (all p < 0.0334) than sham (Achilles: 141.34 ± 20.9 N/mm; 60.30 ± 7.7%; supraspinatus: 135.14 ± 30.2 N/mm; 60.85 ± 15.4%). Modulus of Achilles and supraspinatus tendons treated with fUS-1 (159.88 ± 25.7 MPa; 150.12 ± 22.0 MPa, respectively) were similar to sham (156.35 ± 23.0 MPa; 153.02 ± 29.3 MPa, respectively). These results suggest that fUS preserves mechanical properties better than DN, with fUS-1 performing better than fUS-2 and fUS-3. fUS should be studied further to fully understand its mechanical and healing effects to help evaluate fUS as an alternative, non-invasive treatment for tendon injuries.
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