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Advances in Microscopic Studies of Tendinopathy: Literature Review and Current Trends, with Special Reference to Neovascularization Process. J Clin Med 2022; 11:jcm11061572. [PMID: 35329898 PMCID: PMC8949578 DOI: 10.3390/jcm11061572] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 03/10/2022] [Accepted: 03/11/2022] [Indexed: 01/05/2023] Open
Abstract
Tendinopathy is a process of chaotic extracellular matrix remodeling followed by increased secretion of enzymes and mediators of inflammation. The histopathological assessment of tendinous tissue is crucial to formulate the diagnosis and establish the severity of tendon degeneration. Nevertheless, the microscopic analysis of tendinous tissue features is often challenging. In this review, we aimed to compare the most popular scales used in tendon pathology assessment and reevaluate the role of the neovascularization process. The following scores were evaluated: the Bonar score, the Movin score, the Astrom and Rausing Score, and the Soslowsky score. Moreover, the role of neovascularization in tendon degeneration was reassessed. The Bonar system is the most commonly used in tendon pathology. According to the literature, hematoxylin and eosin with additional Alcian Blue staining seems to provide satisfactory results. Furthermore, two observers experienced in musculoskeletal pathology are sufficient for tendinopathy microscopic evaluation. The control, due to similar and typical alterations in tendinous tissue, is not necessary. Neovascularization plays an ambiguous role in tendon disorders. The neovascularization process is crucial in the tendon healing process. On the other hand, it is also an important component of the degeneration of tendinous tissue when the regeneration is incomplete and insufficient. The microscopic analysis of tendinous tissue features is often challenging. The assessment of tendinous tissue using the Bonar system is the most universal. The neovascularization variable in tendinopathy scoring systems should be reconsidered due to discrepancies in studies.
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Cho Y, Kim HS, Kang D, Kim H, Lee N, Yun J, Kim YJ, Lee KM, Kim JH, Kim HR, Hwang YI, Jo CH, Kim JH. CTRP3 exacerbates tendinopathy by dysregulating tendon stem cell differentiation and altering extracellular matrix composition. SCIENCE ADVANCES 2021; 7:eabg6069. [PMID: 34797714 PMCID: PMC8604415 DOI: 10.1126/sciadv.abg6069] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 10/01/2021] [Indexed: 05/31/2023]
Abstract
Tendinopathy, the most common disorder affecting tendons, is characterized by chronic disorganization of the tendon matrix, which leads to tendon tear and rupture. The goal was to identify a rational molecular target whose blockade can serve as a potential therapeutic intervention for tendinopathy. We identified C1q/TNF-related protein-3 (CTRP3) as a markedly up-regulated cytokine in human and rodent tendinopathy. Overexpression of CTRP3 enhanced the progression of tendinopathy by accumulating cartilaginous proteoglycans and degenerating collagenous fibers in the mouse tendon, whereas CTRP3 knockdown suppressed the tendinopathy pathogenesis. Functional blockade of CTRP3 using a neutralizing antibody ameliorated overuse-induced tendinopathy of the Achilles and rotator cuff tendons. Mechanistically, CTRP3 elicited a transcriptomic pattern that stimulates abnormal differentiation of tendon stem/progenitor cells and ectopic chondrification as an effect linked to activation of Akt signaling. Collectively, we reveal an essential role for CTRP3 in tendinopathy and propose a potential therapeutic strategy for the treatment of tendinopathy.
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Affiliation(s)
- Yongsik Cho
- Center for RNA Research, Institute for Basic Science, 08826 Seoul, South Korea
- Department of Biological Sciences, College of Natural Sciences, Seoul National University, 08826 Seoul, South Korea
| | - Hyeon-Seop Kim
- Center for RNA Research, Institute for Basic Science, 08826 Seoul, South Korea
- Department of Biological Sciences, College of Natural Sciences, Seoul National University, 08826 Seoul, South Korea
| | - Donghyun Kang
- Center for RNA Research, Institute for Basic Science, 08826 Seoul, South Korea
- Department of Biological Sciences, College of Natural Sciences, Seoul National University, 08826 Seoul, South Korea
| | - Hyeonkyeong Kim
- Center for RNA Research, Institute for Basic Science, 08826 Seoul, South Korea
- Department of Biological Sciences, College of Natural Sciences, Seoul National University, 08826 Seoul, South Korea
| | - Narae Lee
- Center for RNA Research, Institute for Basic Science, 08826 Seoul, South Korea
- Department of Biological Sciences, College of Natural Sciences, Seoul National University, 08826 Seoul, South Korea
| | - Jihye Yun
- Department of Biological Sciences, College of Natural Sciences, Seoul National University, 08826 Seoul, South Korea
- School of Medicine, CHA University, 13496 Seongnam, South Korea
| | - Yi-Jun Kim
- Institute of Convergence Medicine, Ewha Womans University Mokdong Hospital, 07985 Seoul, South Korea
| | - Kyoung Min Lee
- Foot and Ankle Division, Department of Orthopedic Surgery, Seoul National University Bundang Hospital, 13620 Seongnam, South Korea
| | - Jin-Hee Kim
- Department of Anatomy and Cell Biology, Seoul National University College of Medicine, 03080 Seoul, South Korea
| | - Hang-Rae Kim
- Department of Anatomy and Cell Biology, Seoul National University College of Medicine, 03080 Seoul, South Korea
| | - Young-il Hwang
- Department of Anatomy and Cell Biology, Seoul National University College of Medicine, 03080 Seoul, South Korea
| | - Chris Hyunchul Jo
- Department of Orthopedic Surgery, Seoul Metropolitan Government–Seoul National University (SMG-SNU) Boramae Medical Center, Seoul National University College of Medicine, 07061 Seoul, South Korea
| | - Jin-Hong Kim
- Center for RNA Research, Institute for Basic Science, 08826 Seoul, South Korea
- Department of Biological Sciences, College of Natural Sciences, Seoul National University, 08826 Seoul, South Korea
- Interdisciplinary Program in Bioinformatics, Seoul National University, 08826 Seoul, South Korea
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Savva C, Karagiannis C, Korakakis V, Efstathiou M. The analgesic effect of joint mobilization and manipulation in tendinopathy: a narrative review. J Man Manip Ther 2021; 29:276-287. [PMID: 33769226 PMCID: PMC8491707 DOI: 10.1080/10669817.2021.1904348] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Objective: To summarize the available literature with regards to the potential analgesic effect and mechanism of joint mobilization and manipulation in tendinopathy. Results: The effect of these techniques in rotator cuff tendinopathy and lateral elbow tendinopathy, applied alone, compared to a placebo intervention or along with other interventions has been reported in some randomized controlled trials which have been scrutinized in systematic reviews. Due to the small randomized controlled trials and other methodological limitations of the evidence base, including short-term follow-ups, small sample size and lack of homogenous samples further studies are needed. Literature in other tendinopathies such as medial elbow tendinopathy, de Quervain's disease and Achilles tendinopathy is limited since the analgesic effect of these techniques has been identified in few case series and reports. Therefore, the low methodological quality renders caution in the generalization of findings in clinical practice. Studies on the analgesic mechanism of these techniques highlight the activation of the descending inhibitory pain mechanism and sympathoexcitation although this area needs further investigation. Conclusion: Study suggests that joint mobilization and manipulation may be a potential contributor in the management of tendinopathy as a pre-conditioning process prior to formal exercise loading rehabilitation or other proven effective treatment approaches.
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Affiliation(s)
- Christos Savva
- Department of Health Science, European University, Nicosia, Cyprus
| | | | | | - Michalis Efstathiou
- Department of Life and Health Sciences, University of Nicosia, Nicosia, Cyprus
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Sikes KJ, Andrie KM, McConnell A, Wist S, Smith S, Cole B, Frisbie DD, Santangelo KS. Clinical and Histologic Manifestations of a Novel Rectus Femoris Myotendinous Junction Injury in Rats. Muscles Ligaments Tendons J 2021; 11:600-613. [PMID: 38111789 PMCID: PMC10726684 DOI: 10.32098/mltj.04.2021.01] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Background Animal models of muscle injury have primarily relied on methods which do not mimic the chronic scarring that typically occurs adjacent to the myotendinous junction (MTJ). The goal of this study was three-fold: (i) to create a strain-induced in vivo model of rectus femoris MTJ injury in rats; (ii) to document clinical manifestations of injury using longitudinal tracking of individual animals via voluntary and compulsory (treadmill) mobility analyses and (iii) to validate and assess the model for persistent scarring through serial histologic assessment and development of a semi-quantitative grading scheme to characterize injury response over time. Methods Strain-induced MTJ injury was generated in male Sprague Dawley rats via needle tension directed along the transverse axis between the rectus femoris muscle and distal tendon that attaches to the patella. Animals received mobility assessments (gait analysis using a DigiGait Treadmill System and weight bearing using a Tekscan Rodent Walkway System) at days 0, 1, 3, 6, 13, 20, and 27 of the experimental protocol. Rats were euthanized at 1, 3, 7, 14, and 28 days post-injury (n = 6 rats per time-point) and hindlimbs were processed for histology. Results Significant changes in locomotor parameters included injured and contralateral limb paw area, max dA/dt (limb deceleration/breaking time), stride time, stance time, force time impulse, and fore/hind symmetry, and injured limb maximum force. The most significant and consistent histologic finding was a pathologic fibrotic adhesive lesion at the muscle and tendon interface along the proximal aspect of the patella just distal to the injury site. This lesion was composed of reactive fibroblasts, disorganized collagen fibers, vascular profiles, and a myxomatous ground substance stroma. Conclusions This work is the first to characterize the clinical and pathologic development of a chronic model of rectus femoris MTJ injury, which resulted in altered mobility likely caused by a strain-induced fibrotic scar along the anterior patella. Notably, both the functional and pathologic changes recapitulated the course of injury progression similar to what is described in humans. This work provides a unique model to study MTJ injury mechanisms for the identification of enhanced treatment options for patients who suffer from activity-related muscle conditions.
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Affiliation(s)
- K J Sikes
- Department of Clinical Sciences, Colorado State University, Fort Collins (CO), U.S.A
| | - K M Andrie
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins (CO), U.S.A
| | - A McConnell
- Department of Clinical Sciences, Colorado State University, Fort Collins (CO), U.S.A
| | - S Wist
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins (CO), U.S.A
| | - S Smith
- Department of Clinical Sciences, Colorado State University, Fort Collins (CO), U.S.A
| | - B Cole
- Department of Orthopaedic Surgery, Rush University Medical Center, Chicago (IL), U.S.A
| | - D D Frisbie
- Department of Clinical Sciences, Colorado State University, Fort Collins (CO), U.S.A
| | - K S Santangelo
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins (CO), U.S.A
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Wang C, Zhang Y, Zhang G, Yu W, He Y. Adipose Stem Cell-Derived Exosomes Ameliorate Chronic Rotator Cuff Tendinopathy by Regulating Macrophage Polarization: From a Mouse Model to a Study in Human Tissue. Am J Sports Med 2021; 49:2321-2331. [PMID: 34259608 DOI: 10.1177/03635465211020010] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND Chronic rotator cuff (RC) tendinopathy is one of the most prevalent causes of shoulder pain. Growing evidence suggests that macrophages play a significant role in the proinflammatory response, resolution of inflammation, and tissue healing of tendinopathy. In particular, enhancement of M2 macrophage (M2φ) activity contributes to the accelerated healing of tendinopathy. Therefore, a treatment that enhances M2φ polarization would be useful for patients with this common musculoskeletal disorder. PURPOSE To investigate whether adipose stem cell-derived exosomes (ASC-Exos) enhance M2φ polarization and ameliorate chronic RC tendinopathy. STUDY DESIGN Controlled laboratory study. METHODS First, we compared the effects of ASC-Exos on polarization of mouse bone marrow-derived macrophages between a classically activated phenotype (M1φ) and an alternatively activated phenotype (M2φ) in vitro. In total, 72 C57BL/6 mice were assigned to normal cage activity (n = 24) or 5 weeks of treadmill overuse (n = 48). The supraspinatus tendon of each treadmill overuse mouse was treated with ASC-Exos (n = 24) or saline (n = 24). Histological and biomechanical outcomes were assessed 4 weeks after treatment. Finally, tissue samples from human patients with RC tendinopathy were obtained to assay the effect of ASC-Exos on the M1φ/M2φ balance in tissue-resident macrophages. RESULTS ASC-Exos inhibited M1φ polarization and augmented M2φ polarization in vitro and in vivo. Mice in the ASC-Exos group showed less severe pathological changes than those in the saline group, including less cellular infiltration, disorganization of collagen, and ground substance deposition. The modified Bonar score of the ASC-Exos group (mean ± SD, 7.68 ± 1.03) was significantly lower than that of the saline group (9.81 ± 0.96; P < .05). Furthermore, the maximum failure load was significantly higher in the ASC-Exos group than in the saline group (4.23 ± 0.66 N vs 3.86 ± 0.65 N; P < .05), as was stiffness (3.38 ± 0.34 N/m vs 2.68 ± 0.49 N/m; P < .05). CONCLUSION ASC-Exos-mediated polarization balance of M1φ/M2φ contributes to the amelioration of chronic RC tendinopathy. Regulation of the M1φ/M2φ balance could be a new target for the treatment of chronic RC tendinopathy. CLINICAL RELEVANCE Administration of ASC-Exos is a cell-free approach that may become a novel treatment option for chronic RC tendinopathy and should be explored further.
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Affiliation(s)
- Chongyang Wang
- Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - Yao Zhang
- Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - Guangcheng Zhang
- Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - Weilin Yu
- Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - Yaohua He
- Jinshan Branch of Shanghai Sixth People's Hospital, Shanghai, China
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Sustained Exposure of Substance P Causes Tendinopathy. Int J Mol Sci 2020; 21:ijms21228633. [PMID: 33207770 PMCID: PMC7709031 DOI: 10.3390/ijms21228633] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 11/08/2020] [Accepted: 11/12/2020] [Indexed: 01/09/2023] Open
Abstract
Recently, neuromediators such as substance P (SP) have been found to be important factors in tendon homeostasis. Some studies have found SP to be the cause of inflammation and tendinopathy, whereas others have determined it to be a critical component of tendon healing. As demonstrated by these conflicting findings, the effects of SP on tendinopathy remain unclear. In this study, we hypothesized that the duration of SP exposure determines its effect on the tendons, with repetitive long-term exposure leading to the development of tendinopathy. First, we verified the changes in gene and protein expression using in vitro tenocytes with 10-day exposure to SP. SP and SP + Run groups were injected with SP in their Achilles tendon every other day for 14 days. Achilles tendons were then harvested for biomechanical testing and histological processing. Notably, tendinopathic changes with decreased tensile strength, as observed in the Positive Control, were observed in the Achilles in the SP group compared to the Negative Control. Subsequent histological analysis, including Alcian blue staining, also revealed alterations in the Achilles tendon, which were generally consistent with the findings of tendinopathy in SP and SP + Run groups. Immunohistochemical analysis revealed increased expression of SP in the SP group, similar to the Positive Control. In general, the SP + Run group showed worse tendinopathic changes. These results suggest that sustained exposure to SP may be involved in the development of tendinopathy. Future research on inhibiting SP is warranted to target SP in the treatment of tendinopathy and may be beneficial to patients with tendinopathy.
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Hsieh YL, Lin MT, Hong CZ, Chen HS. Percutaneous soft tissue release performed using a blunt cannula in rabbits with chronic collagenase-induced Achilles tendinopathy. Foot Ankle Surg 2019; 25:186-192. [PMID: 29409286 DOI: 10.1016/j.fas.2017.10.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 10/12/2017] [Accepted: 10/12/2017] [Indexed: 02/04/2023]
Abstract
BACKGROUND This study investigated the effects of percutaneous soft tissue release (PSTR) performed using a blunt cannula on (1) the inflammatory cells-count, (2) expressions of calcitonin gene-related peptide (CGRP) and (3) substance P (SP) in rabbits with chronic phase of collagenase-induced Achilles tendinopathy. METHODS Thirty-two adult male New Zealand rabbits were randomly divided into four groups: (1) collagenase and PSTR treatment; (2) collagenase and sham-operated PSTR treatment; (3) vehicle-only injection and PSTR treatment; and (4) vehicle-only injection and sham-operated PSTR treatment. Achilles tendon of adult male rabbits was injected with 10μl of collagenase under ultrasonography localization. After 30 days, PSTR was performed using an 18G beauty cosmetic blunt tip micro cannula needle to release the soft tissue and paratenon above the inflamed Achilles tendon. The treated tendons and spinal cords of L5-S2 were harvested 5days after treatment for histological assessment and immunohistochemical analysis. RESULTS Histopathological examination revealed that PSTR achieved significant reduction in hypercellularity with pronounced infiltration of immune cells at the site of paratenon in tendons injected with collagenase compared with sham operation (p<0.05). Immunohistochemical analysis also showed marked decrease in expression of CGRP in tendon and SP in dorsal horns after PSTR (p<0.05). CONCLUSIONS This study showed positive effects in an animal model of chronic tendinopathy, and can be considered a treatment option, but that further research is necessary to determine its role in clinical practice.
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Affiliation(s)
- Yueh-Ling Hsieh
- Department of Physical Therapy, Graduate Institute of Rehabilitation Science, China Medical University, Taichung 40402, Taiwan.
| | - Ming-Ta Lin
- Kuan-Ta Rehabilitation and Pain Clinic, Taichung 40652, Taiwan
| | | | - Hsin-Shui Chen
- Department of Physical Medicine and Rehabilitation, China Medical University, Bei-Gang Hospital, Yun-Lin 65152, Taiwan; Department of Rehabilitation Medicine, School of Medicine, College of Medicine, China Medical University, Taichung 40402, Taiwan.
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Titan A, Andarawis-Puri N. Tendinopathy: Investigating the Intersection of Clinical and Animal Research to Identify Progress and Hurdles in the Field. JBJS Rev 2018; 4:01874474-201610000-00002. [PMID: 27792676 DOI: 10.2106/jbjs.rvw.15.00088] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Biological treatments, surgical interventions, and rehabilitation exercises have been successfully used to treat tendinopathy, but the development of effective treatments has been hindered by the lack of mechanistic data regarding the pathogenesis of the disease. While insightful, clinical studies are limited in their capacity to provide data regarding the pathogenesis of tendinopathies, emphasizing the value of animal models and cell culture studies to fill this essential gap in knowledge. Clinical pathological findings from imaging studies or histological analysis are not universal across patients with tendinopathy and have not been clearly associated with the onset of symptoms. There are several unresolved controversies, including the cellular changes that accompany the tendinopathic disease state and the role of inflammation. Additional research is needed to correlate the manifestations of the disease with its pathogenesis, with the goal of reaching a field-wide consensus on the pathology of the disease state. Such a consensus will allow standardized clinical practices to more effectively diagnose and treat tendinopathy.
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Affiliation(s)
- Ashley Titan
- Leni and Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY
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Thampatty BP, Wang JHC. Mechanobiology of young and aging tendons: In vivo studies with treadmill running. J Orthop Res 2018; 36:557-565. [PMID: 28976604 PMCID: PMC5839954 DOI: 10.1002/jor.23761] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 09/13/2017] [Indexed: 02/04/2023]
Abstract
Tendons are unique in the sense that they are constantly subjected to large mechanical loads and that they contain tendon-specific cells, including tenocytes and tendon stem/progenitor cells. The responses of these cells to mechanical loads can be anabolic or catabolic and as a result, change the biological properties of the tendon itself that may be beneficial or detrimental. On the other hand, aging also induces aberrant changes in cellular expression of various genes and production of various types of matrix proteins in the tendon, and consequently lead to tendon degeneration and impaired healing in aging tendons; both could be improved by moderate physiological mechanical loading such as treadmill running. This article gives an overview on the mechanobiology research of young and aging animal tendons using treadmill running model. The challenges in such treadmill running studies are also discussed. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:557-565, 2018.
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Affiliation(s)
- Bhavani P. Thampatty
- MechanoBiology Laboratory, Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, 210 Lothrop street, BST, E1640, Pittsburgh, PA 15213, USA
| | - James H-C. Wang
- MechanoBiology Laboratory, Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, 210 Lothrop street, BST, E1640, Pittsburgh, PA 15213, USA
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Herod TW, Veres SP. Development of overuse tendinopathy: A new descriptive model for the initiation of tendon damage during cyclic loading. J Orthop Res 2018; 36:467-476. [PMID: 28598009 DOI: 10.1002/jor.23629] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 06/05/2017] [Indexed: 02/04/2023]
Abstract
Tendinopathic tissue has long been characterized by changes to collagen microstructure. However, initial tendon damage from excessive mechanical loading-a hallmark of tendinopathy development-could occur at the nanoscale level of collagen fibrils. Indeed, it is on this scale that tenocytes interact directly with tendon matrix, and excessive collagen fibril damage not visible at the microscale could trigger a degenerative cascade. In this study, we explored whether initiation of tendon damage during cyclic loading occurs via a longitudinal compression-induced buckling mechanism of collagen fibrils leading to nanoscale kinkband development. Two groups of tendons were cyclically loaded to equivalent peak stresses. In each loading cycle, tendons in one group were unloaded to the zero displacement mark, while those in the other group were unloaded to a nominal level of tension, minimizing the potential for fibril buckling. Tendons that were unloaded to the zero displacement mark ruptured significantly sooner during cyclic loading (1,446 ± 737 vs. 4,069 ± 1,129 cycles), indicating that significant fatigue damage is accrued in the low stress, toe region of the load-deformation response. Ultrastructural analysis using scanning electron microscopy of tendons stopped after 1,000 cycles showed that maintaining a nominal tension slowed the accumulation of kinkbands, supporting a longitudinal compression-induced buckling mechanism as the basis for kinkband development. Based on our results, we present a new descriptive model for the initiation of tendon damage during cyclic loading. The so-called Compression of Unrecovered Elongation or CUE Model may provide useful insight into the development of tendinopathy. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:467-476, 2018.
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Affiliation(s)
- Tyler W Herod
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Samuel P Veres
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada.,Division of Engineering, Saint Mary's University, 923 Robie Street, Halifax, Nova Scotia Canada B3H 3C3
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