Strength Of Tendon Research Articles

The Impact of Hypercholesterolemia on Tendon Injury Repair

Background Hypercholesterolemia is a condition characterized by high blood cholesterol levels and is associated with tendon xanthomas (cholesterol deposits found on superficial tendons). Lipid accumulation in the tendon's extracellular spaces1 may disrupt the parallel organization of collagen substructures within the tendon, and negatively affect its mechano-sensing and mechanical properties, which may lead to injury. We hypothesized that tendon strength and metabolism would be inferior in a high cholesterol environment and attenuate the tendon's ability to repair after injury. Methods 50 Sprague-Dawley (SD, control) and 50 apolipoprotein E knock-out rats (ApoE, Envigo, IL, USA) rats bred in-house were subject to a unilateral patellar tendon (PT) injury at 12 weeks of age; the uninjured limb served as a control. Animals were euthanased at 3, 14 or 42 days post-injury, time-points chosen to represent tendon inflammatory, reparative and remodelling repair phases, respectively. Animals were randomly assigned for investigating gene expression (SD/ApoE per timepoint n=4/4), tissue histology (n=6/6), biomechanical testing (n=10/10; 14 and 42 days only). Equal male/female ratios were used where possible (total SD M23/F27, ApoE M23/F26). Results ApoE total cholesterol was over double that of SD rats (mean 2.12 vs 0.99 mg/ml, p<0.001). Despite this, there was little histological evidence of lipid content (Oil Red-O staining) in tendons of either group, and no apparent differences in tendon mechanical or material properties (Fig. 1). However, there were differences in gene expression (Fig. 2). ApoE rats demonstrated significantly greater COX2 expression than SD; other inflammatory markers (TGFβ, IL-1, IL-6) did not differ between groups. COL1A1, SCX, LOXα were significantly upregulated 14 days post injury in SD compared to ApoE. A greater COL3A1 response was also observed in ApoE compared to SD rats. Discussion We found differences in injury repair at the cellular level, using an ApoE high cholesterol model. There was little evidence of lipid accumulation at the tissue level, therefore the PT may have been a poor choice for an injury study in this instance and it is not surprising that biomechanical differences were not found. Moreover, ApoE rats were recently found to demonstrate only modest early atherosclerotic characteristics2, thus the young age of our cohort may be a primary factor in the lack of physical evidence of lipid accumulation. Nonetheless, our results indicate that even with a mild phenotype, high cholesterol significantly modulates tendon inflammatory and healing cellular activity, as indicated by altered mRNA levels, which may contribute to the known consequences of tendon cholesterol on tendons in humans. References 1Grewal et al. 2014. Accumulation of oxidized LDL in the tendon tissues of C57BL/6 or apolipoprotein E knock-out mice that consume a high fat diet: potential impact on tendon health. PLoS One 9(12): e114214. 2Rune et al., 2018. Long-term Western diet fed apolipoprotein E-deficient rats exhibit only modest early atherosclerotic characteristics. Sci Rep 8(1): 5416.

The effects of using a combination of static stretching and aerobic exercise on muscle tendon unit stiffness and strength in ankle plantar-flexor muscles

ABSTRACT The purpose of the present study was to investigate the effects of using a combination of static stretching and aerobic exercise on muscle tendon unit stiffness and muscle strength in the ankle plantar-flexor muscles. Fifteen healthy males (23.3 ± 2.7 years, 170.3 ± 6.5 cm, 64.9 ± 8.7 kg) received three different interventions, in random order. Intervention 1 received 10 min of aerobic exercise after five cycles of one minute of static stretching. Intervention 2 received 10 min of aerobic exercise before the static stretching. Intervention 3 received 5 min of aerobic exercise both before and after the static stretching. The range of motion of ankle dorsiflexion, stretch tolerance, muscle tendon unit stiffness, peak torque of ankle plantarflexion, and the amplitude of electromyography were measured. In all interventions, the range of motion and stretch tolerance significantly increased (p < 0.05), but muscle tendon unit stiffness decreased significantly for all interventions (p < 0.05). Peak torque of ankle plantar flexion and amplitude of electromyography significantly increased for Interventions 1 and 3 (p < 0.05), while these significantly decreased for Intervention 2 (p < 0.05). These data indicated that range of motion and stretch tolerance were increased, but muscle tendon unit stiffness was decreased regardless of the order of static stretching and aerobic exercise. Aerobic exercise after static stretching increased the peak torque and amplitude of electromyography.

Nanoparticle-coated sutures providing sustained growth factor delivery to improve the healing strength of injured tendons

Tendon injuries are common diseases. The healing capacity of tendon is limited due to its special composition of extra-cellular matrix and hypocellularity and hypovascularity. The purpose of this study was to evaluate the effectiveness of nanoparticle-coated sutures carrying growth factors for accelerating tendon repair. A variety of experimental methods had been used to investigate the characteristics and therapeutic effects of the modified sutures. Nanoparticles could adhere uniformly to the surface of the suture through polydopamine. Even sutured in the tendon, most of nanoparticles were still remained on the surface of suture, and the loaded proteins could spread into the tendon tissues. In vivo study, the ultimate strength of repaired tendons treated with bFGF and VEGFA-releasing sutures was significantly greater than the tendons repaired with control sutures at multiple time-points, whether in the chicken model of flexor tendon injury or the rat model of Achilles tendon injury. At week 6, the adhesion score in the bFGF and VEGFA-releasing suture group was significantly lower than those of the control suture group. Tendon gliding excursion was significantly longer in the bFGF and VEGFA-releasing suture group than that in the control bare sutures. Work of digital flexion was significantly decreased in the bFGF and VEGFA-releasing suture group. In a word, we developed a platform for local and continuous delivery of growth factors based on the nanoparticle-coated sutures, which could effectively deliver growth factors to tissues and control the release of growth factors. This growth factors delivery system is an attractive therapeutic tool to repair injured tendons. Statement of significanceTendon rupture is a common clinical injury, due to the special character of the tendon with mainly extra cellular matrix and hypocellularity and hypovascularity, the healing capacity of the injured tendon is limited. In this study, nanoparticle-coated surgical sutures carrying growth factors were prepared to accelerate tendon repair. After treatment, bFGF and VEGFA loaded nanoparticle-coated sutures can significantly enhance tendon healing, and significantly improve tendon gliding function and effectively inhibit the formation of adhesion. Moreover, these nanoparticle-coated sutures have good biocompatibility and no obvious tissue reaction, which provides more guarantee for further clinical application. This is an attractive and promising approach that uses surgical suture as a growth factor delivery tool to repair tendon injury, which can simplify the treatment. And this kind of bioactive sutures may be applied to other tissue repair, such as muscle, nerve, intestinal canal, blood vessel, skin, and so on.

Research on Anchorage of GFRP Anchor Bolts and Heads

GFRP is an abbreviation of Glass Fiber Reinforced Polymer. It is an inorganic non-metallic material made of glass fiber reinforced material, synthetic resin as matrix material, and compounded by a certain process. Although the glass fiber reinforced polymer anchor can fundamentally solve the problem of poor corrosion resistance of the steel bar anchor, in the anchor system, the force on the surface layer or the waist beam needs to be transmitted to the shaft through the anchor head. At present, the pull-out strength of domestic GFRP anchors is far away from the tensile strength of GFRP tendons. This may cause the anchorage system of anchors to fail due to anchorage failure, and the tensile strength of GFRP tendons cannot be fully exerted. When ordinary clip-type anchorages are used, there is a huge clamping force on the ribs in the anchorage zone, which may result in the shear failure of ribs.Based on this, this article uses a high-strength impregnated reinforcement material to carry out the tensile failure test of a GFRP anchored anchorage with a diameter of 18cm. The study found that the use of high-strength reinforced concrete can make the GFRP anchor achieve the maximum tensile strength, and with the increase of curing time, the ability of the high-strength reinforcement to limit the displacement of the anchorage end is stronger.

Mathematical modelling of collagen fibres rearrangement during the tendon healing process

Tendon injuries present a significant clinical challenge to modern medicine as they heal slowly and rarely recover the structure and mechanical strength of a healthy tendon. Moreover, tendon represents a highly under-researched tissue with the process of healing not fully elucidated. To improve the understanding of tendon function and healing process we propose a new model of collagen fibers rearrangement during tendon 1 healing. The model consists of integro-differential equation describing the dynamics of collagen fibers distribution. We further reduce the model in a suitable asymptotic regime leading to a nonlinear non-local Fokker-Planck type equation for the spatial and orientation distribution of col-lagen fiber bundles. The reduced model allows for possible parameter estimation based on data due to its simplicity. We showcase some of the qualitative properties of this model simulating its long time asymptotic behavior and the total time for tendon fibers to align in terms of the model parameters. A possible biological interpretation of the numerical experiments performed leads us to the working hypothesis of the importance of the tendon cell size in patients' recovery.

Tenogenic effects of silymarin following experimental Achilles tendon transection in rats.

Tendon healing is prolonged due to the small number of cells, poor circulation, and low metabolism. The optimal tendon healing and its complete functional recovery have always been a challenge for researchers. Silymarin possesses anti-inflammatory, anti-oxidant, analgesic, and regenerative properties. The present study aimed to investigate the effects of silymarin on healing the Achilles tendon in rats. Twenty-four male Wistar rats were divided into two groups of control and treatment. After surgical preparation, a complete transverse incision was made in the middle part of the Achilles tendon, and then a modified Kessler suture was placed. The control group received 1.00 mL normal saline for five consecutive days, and the treatment group received 50.00 mg kg-1 of silymarin suspended in 1.00 mL normal saline for five days, orally. During the experimental period, Achilles functional index (AFI) was recorded. Six weeks after surgery, sampling was done. Histopathologically, a significant increase in the density of collagen fibers and reduction in neovascularization and inflammatory cells infiltration were observed in the treatment group. The biomechanical evaluation showed a significant increase in tensile strength of the tendon in the treatment group compared to the control group. The AFI results were concomitant with the results stated above, indicating an improvement in the AFI of rats in the treatment group. The present study results showed that oral administration of silymarin improved tissue healing indices, biomechanical properties, and functional index, leading to optimal healing of experimental Achilles tendon injury in the rat.

Nanoparticle-Coated Sutures Providing Sustained Growth Factor Delivery to Improve the Healing Strengths of Injured Tendons

Tendon injuries are more common, and due to the lack of adequate growth factors, the healing capacity of the injured tendon is limited. The objective of this study is to evaluate the effectiveness of Nanoparticle-coated sutures carrying growth factors on accelerating tendon repair. We found that nanoparticles can adhere uniformly to the surface of the suture modified with polydopamine. After stitching, the nanoparticles remain on the surface of the suture, and its loaded proteins can spread in the tendon tissues. After treatment, in the chicken flexor tendon healing model and the rat Achilles healing model, the ultimate strengths of repaired tendons treated with bFGF and VEGFA-releasing sutures was significantly greater than the tendons repaired with control sutures at multiple time-points. At 6 weeks, adhesion scores in the bFGF and VEGFA-releasing suture group were significantly smaller than those of the control suture group. Tendon gliding excursions were significantly greater in the bFGF and VEGFA-releasing suture group than in the unmodified control sutures. Work of digital flexion was significantly decreased in the bFGF and VEGFA-releasing suture group than in the control group. In a word, we developed a novel platform for local and sustained delivery of growth factors based on the Nanoparticle-coated sutures, which can effectively deliver growth factors to tissues and control the release of growth factors. Dual growth factors loaded Nanoparticle-coated sutures can significantly promote tendon healing. This growth factors delivery system is an attractive therapeutic tool to repair injured tendons.

Evidence-Based Physiatry: Treatment of Midportion Achilles Tendinopathy.

Achilles tendinopathy (AT) is a common musculoskeletal disorder that affects both the general population and athletes. Patients present with a combination of features, including tendon pain, swelling, morning stiffness, and restricted weight-bearing. The injury can be classified as midportion (noninsertional) and insertional AT based on primary location of pathology. Although both types of AT are often managed conservatively, insertional AT tends to be less responsive to nonsurgical treatments. Furthermore, coexisting conditions such as Haglund deformity should be considered in treatment protocols.1 Eccentric exercises (ECCs) have been the mainstay in treatment of mid-portion AT based on the landmark study by Alfredson et al.2 Eccentric loading may stimulate tendon healing through multiple mechanisms including improving tendon strength and disrupting pain from neovascularization. However, a subset of patients may not respond to ECC and consider additional treatments. A limited number of direct comparisons among interventions create a challenge to clinical decision making for midportion AT. The Victorian Institute of Sports Assessment-Achilles is considered a valid outcome measure for Achilles tendon function. Two published network meta-analyses may help physiatrists determine the best evidence-based treatment using the Victorian Institute of Sports Assessment–Achilles to measure effectiveness between treatments.3,4 WHAT IS A NETWORK META-ANALYSIS? Whereas traditional meta-analysis (pairwise meta-analysis) focuses on a single treatment comparison, a network meta-analysis (NMA) allows for comparisons among all treatment options using both direct and indirect results from studies that use a common measure. For example, intervention A was shown to be superior to intervention B in one study, and intervention B was superior to intervention C in a separate study. The NMA can help determine the relative effectiveness of interventions A, B, and C using mathematical models to determine effect size. The NMA specific to midportion AT identified 22 studies with 978 patients that used the Victorian Institute of Sports Assessment–Achilles to measure outcomes divided into time frames of 3 mos or less and 3 to 12 mos.3 WHAT TREATMENT IS AVAILABLE FOR EARLY MANAGEMENT (≤3 MOS)? Across interventions, acupuncture and ECC combined with high-volume injection with steroid were each shown to improve pain and function. However, because high-volume injection is composed of saline and anesthetic and can have steroid added, safety concerns such as atrophy and tendon rupture should be considered. ECC alone did not have predictable gains, suggesting synergy in combining treatment for functional improvements in early treatment. WHAT TREATMENTS ARE MOST EFFECTIVE FOR LONGER-TERM MANAGEMENT OF 3–12 MOS? Natural history (wait-and-see) was inferior to all other treatment options. ECC does demonstrate benefits after 3 mos. However, greater effects of ECC were identified when combined with high-volume injection with steroid and extracorporeal shockwave therapy. Although findings suggest that platelet-rich plasma as a monotherapy and platelet-rich plasma combined with ECC improve outcomes compared with a wait-and-see approach, results from the NMA suggest that these interventions do not have favorable outcomes above ECC. Tolerability and safety in adverse outcomes were similar across interventions studied. LIMITATIONS IN INTERPRETING NMA Limitations in NMA should be considered when interpreting findings, including differences in methodology, inclusion criteria, and choice of outcome measures. As a result, other available treatment options such as glyceryl trinitrate patch, prolotherapy, or adipose-derived stromal vascular fraction injection may not have qualified to be included within the recent NMAs. Furthermore, results from a single study can influence overall results. Acupuncture was shown effective in both short- and longer-terms based on the results of a single study. Furthermore, injection therapies were grouped together in one NMA.4 HOW DOES THIS CHANGE PHYSIATRY PRACTICE? Despite its limitations, the findings from the NMA provide guidance for evidence-based practice in the management of midportion AT. The wait-and-see approach is not recommended. Acupuncture was shown to be effective in both short- and longer-term outcomes, but the results derived from a single study. Both platelet-rich plasma alone and platelet-rich plasma combined with ECC did not have favorable outcomes compared with ECC. Because of wide availability and low cost, ECC should be considered for initial management but may more reliably demonstrate improvement after 3 mos. The NMA showed that all interventions for midportion AT have a comparable safety profile while providing effective treatment over wait and see to 1 yr. The effects of each intervention and safety concerns, including tenotoxicity in high-volume injection with corticosteroids and anesthetics, should be considered when interpreting studies limited to 12 mos. Consequently, when treating midportion AT, physiatrists should offer treatment above the wait-and-see approach. This should include physical therapy with progressive tendon loading as an initial treatment. In the authors’ opinion, offering combined ECC with extracorporeal shockwave therapy is reasonable given good safety profile and the mechanisms for action of combined treatment to stimulate tendon healing, address pain, and restore function.

Isokinetic Evaluation of Knee Strength and Endurance in Hemodialysis Patients Treated with the Transpatellar Tunnel Technique for Bilateral Spontaneous Quadriceps Tendon Ruptures.

There are numerous surgical techniques described for treating acute quadriceps tendon rupture. We aim to evaluate the strength of the quadriceps tendon using isokinetic tests in hemodialysis patients treated with the transpatellar tunnel technique for bilateral spontaneous quadriceps tendon ruptures. Additionally, functional and clinical results were investigated and compared with hemodialysis patients without a history of quadriceps tendon rupture. We retrospectively reviewed hemodialysis patients diagnosed with quadriceps tendon rupture who were operated between 2005 and 2015 at our institution. Eight patients with simultaneous bilateral quadriceps tendon rupture treated with the transpatellar tunnel technique (group 1; the operated group) and 10 patients with chronic renal failure without a history of quadriceps tendon rupture who underwent hemodialysis (group 2; the control group) were included in this study. The active range of motion (ROM), Lysholm and Tegner scores, knee flexor and extensor muscle strengths, and endurances were measured using an isokinetic dynamometer for each group and compared between the groups. The mean age was 44.6 and 40.2 years in groups 1 and 2, respectively. The mean follow-up was 58.6 (range, 24-140) months in group 1. The active ROM was 113.7 ± 9.7 degrees in group 1 and 130 ± 4.8 degrees in group 2 (p < 0.001). The mean Tegner score was not significantly different between the groups (1.87 ± 1.1 in group 1 vs. 2.6 ± 0.9 in group 2; p = 0.212). However, the Lysholm score was significantly higher in group 2 (93.2 ± 7.3 vs. 76.7 ± 13.8; p = 0.009). The mean extensor strength and endurance were significantly higher in group 2 than in group 1. The mean flexor strength and endurance were higher in group 1 than in group 2, but no significant difference was found. Although using the transpatellar tunnel technique for bilateral spontaneous quadriceps tendon ruptures in hemodialysis patients can provide acceptable functional results, the ROM and strength particularly in extensor muscle might be significantly lower than control group. Level of evidence is Level III therapeutic case-control study.

Effect of partial vs complete circumferential epitendinous suture placement on the biomechanical properties and gap formation of canine cadaveric tendons.

To determine the effect of partial vs complete circumferential epitendinous suture (ES) placement in addition to a core suture on the biomechanical strength and gapping characteristics of repaired canine tendinous constructs. Ex vivo, biomechanical study. Thirty-six canine superficial digital flexor tendons. Superficial digital flexor tendons were randomly assigned to three groups (n = 12), sharply transected and repaired with a core locking-loop suture with Group 1 a partial circumferential ES, 180° on the palmar side; Group 2 a complete circumferential ES, 360° and double knotting technique; or Group 3 a complete circumferential ES, 360° and single knotting technique. After preloading, constructs were distracted to monotonic failure. Failure mode, gap formation, yield, peak, and failure forces were analyzed. Mean yield (group 1 = 68.6 N, group 2 = 106.5 N, group 3 = 114 N, P < .013), peak (group 1 = 92.8 N, group 2 = 134.6 N, group 3 = 147.3 N; P < .001), and failure (group 1 = 88.7 N, group 2 = 133.0 N, group 3 = 145.5 N, P < .001) loads differed between groups. No difference in yield (P = .874), peak (P = .434), or failure load (P = .434) was detected between complete circumferential ES groups. Force to create 1-mm (P < .001) and 3-mm (P < .038) gap formation was greater in specimens with complete vs partial circumferential ES placement. Complete circumferential ES repairs failed primarily by suture pull-through compared with suture breakage in most partial circumferential ES constructs. Addition of a complete circumferential ES with a single or double knotting technique increased the biomechanical strength of normal tendon repairs while reducing gap formation compared with partial ES placement alone. Complete circumferential ES is recommended over partial ES placement.

Evaluation of the Effect of Freezing and Gamma Irradiation on Different Types of Tendon Allografts by DIC Assisted Tensile Testing

This study aimed to evaluate the changes in the endurance properties of four types of tendons caused by freezing and gamma irradiation. Four types of grafts were harvested: quadriceps, semitendinosus + gracilis, tibialis anterior, and peroneus longus. These were put into three groups: Group A was the control group, tested without freezing or irradiation. Grafts in Group B were frozen and irradiated (target dose: 21 kGy), while grafts in Group C were again frozen and irradiated (target dose: 42 kGy). Maximum load, tensile modulus, tensile strength, strain at maximum force and fracture strain were calculated from the force-elongation graphs of cyclic load tests. The higher gamma irradiation dose (Group C) significantly decreased the strains at tensile strength of the quadriceps tendons (p = 0.0004–0.0237), compared to the other two groups. In the case of the quadricep tendons (p = 0.0151), there is a significant decrease in Young’s modulus after gamma irradiation with the dose of 42 kGy. According to the results of the study, the tibialis anterior and the peroneus longus are recommended in ACL reconstruction when gamma irradiation is required, while quadricep tendons, which are usually used for an autograph, are not suitable for allograft reconstruction after gamma irradiation from the viewpoint of mechanical properties.

Interface bond behavior of tensioned glass fiber-reinforced polymer (GFRP) tendons embedded in cemented soils

This paper presents, evaluates, and interprets element pullout tests conducted to investigate the interface bond behavior of Glass Fiber-Reinforced Polymer (GFRP) tendons embedded in cemented soils. Pullout tests were conducted in conjunction with unconfined compression tests to characterize the strength of the cemented soils in which GFRP tendons were embedded. The effects of water content, cement content, and curing time of the cemented soil on the interface bond strength were investigated. Bond-slip curves of the tested specimens were developed considering a multi-segment function defined by characteristic points of interface bond stress peaks and troughs. Two sets of bond-slip curves were identified based on behavior trends observed in the residual strength phase. The ultimate bond strength of the GFRP tendons in cemented soils was found to strongly correlate with the compressive strength of the cemented soil. Ultimately, the bond-slip behavior was modeled using the cemented soil’s unconfined compressive strength and the GFRP tendon’s rib spacing. The proposed bond-slip model was developed using correlations of bond strength and against the parameters governing the behavior of cemented soil.

Mechanical properties of pultruded high-temperature-resistant carbon-fiber-reinforced polymer tendons at elevated temperatures

Cable roof structures built with carbon-fiber-reinforced polymer (CFRP) cables instead of steel cables, which are called CFRP cable roofs, represent a new structure with great development potential. However, as one of the main stressed components of structures, CFRP cables are required to have better fire resistance. In this paper, the fire resistance of a type of high-temperature-resistant (HTR) CFRP tendon is studied. A total of 39 specimens with a diameter of 5 mm are performed in this study, among which 33 specimens are for steady-state tensile tests and 6 for transient state tests. Steady-state tensile tests are conducted over in the 20–600 °C range, and transient state tests are conducted for stress levels ranging from 0.19 to 0.57. The steady-state test results show that HTR CFRP tendons have excellent room-temperature and high-temperature mechanical properties. The strength remained 78% at 200 °C and the elastic modulus remained 82% at 300 °C, indicating the effectiveness of high-temperature resistant resin matrix. When the temperature reaches 600 °C, the strength remains 19%. The transient state test results show that the high initial stress (stress level of 0.57) can aggravate damage to CFRP tendons at high temperatures. Finally, a high-temperature equation is obtained for the temperature dependence of the strength and modulus of HTR CFRP tendons by developing a mathematical model that is fitted to the test data.

Comparison of shoulder muscle strength, cross-sectional area, acromiohumeral distance, and thickness of the supraspinatus tendon between symptomatic and asymptomatic patients with rotator cuff tears

The purpose of this study was to demonstrate the differences in shoulder muscle strength, cross-sectional area of the rotator cuff muscles, acromiohumeral distance, and supraspinatus tendon thickness between symptomatic and asymptomatic patients with rotator cuff tears. Thirty-two symptomatic patients and 23 asymptomatic patients with rotator cuff tears participated in this study. Data of the patients with any type of tear and supraspinatus tear were analyzed. We evaluated the isometric torque, cross-sectional area of the rotator cuff muscles, supraspinatus tendon thickness, acromiohumeral distance, range of motion, and Western Ontario Rotator Cuff Index. Asymptomatic patients showed greater isometric torque of shoulder abduction and internal rotation than symptomatic patients with any type of tear (P ≤ .01). Asymptomatic patients also demonstrated greater cross-sectional area of the supraspinatus (P < .01); however, there was no significant difference in the cross-sectional area of the other cuff muscles. There was also no significant difference in the supraspinatus tendon thickness (P = .10). The acromiohumeral distance at 90° of shoulder abduction was larger (P = .04) in asymptomatic patients. Additionally, similar tendencies were observed in the results of patients with supraspinatus tears, except for the isometric torque of shoulder external rotation. This torque was greater (P < .01) in asymptomatic patients. Asymptomatic patients showed greater shoulder range of motion, muscle strength of shoulder abduction and internal rotation, small occupation ratio of supraspinatus tendon thickness as a percentage of acromiohumeral distance, and large cross-sectional area of supraspinatus.

Parathyroid Hormone‐Loaded Microneedle Promotes Tendon Healing Through Activation of mTOR

AbstractTendon rupture/defects may impose a huge economic and mental burden on patients and society. At present, neither surgery nor conservative treatment regimens can provide long‐term therapeutic benefits, and the prognosis is often disappointing owing to the loss of tendon function and strength. There is an urgent need for innovative strategies to treat defective tendons. Here, a microneedle patch is developed for the efficient transdermal delivery of parathyroid hormone (PTH). The microneedle tip is made up of polyvinyl alcohol (PVA) and is water swellable, but insoluble, thereby ensuring the accurate and efficient release of PTH, while evacuating the skin without any tip material deposition. The PTH‐loaded microneedle patch is replaced daily in a rat tendon defect‐healing model. Results from histology, biomechanics, and gene expression analysis confirm that this newly developed microneedle patch accelerates tendon healing following the subcutaneous delivery of PTH and activates the transforming growth factor (TGF)‐β1/mothers against decapentaplegic homolog 3 (Smad3)/mammalian target of rapamycin (mTOR) signaling cascade, which may be involved in the underlying mechanism. These results suggest that the PTH‐loaded microneedle patch developed herein may serve as a novel therapeutic strategy for the treatment of injured tendons.

Downregulation of type I collagen expression in the Achilles tendon by dexamethasone: a controlled laboratory study

BackgroundSpontaneous Achilles tendon rupture associated with long-term dexamethasone (Dex) use has been reported. However, few studies have investigated the potential mechanism. The aim of this study was to evaluate the effects of oral Dex on type I collagen in humans and rats and its association with tendon rupture.MethodsFirst, six Achilles tendons from patients who received long-term Dex treatment, and another six normal tendons were harvested for histological evaluation. Secondly, 8-week-old rats (n = 72) were randomly assigned to a Dex group or a control group. Type I collagen was studied at the mechanical, histological, and molecular levels after 3 and 5 weeks. Tenocytes isolated from normal human and rat tendon were used to investigate the effect of Dex on cellular scale.ResultsHistological analysis of human and rat tendon tissue revealed an irregular, disordered arrangement of type I collagen in the Dex group compared with the control group. In addition, In the Dex+ group, type I collagen expression decreased in comparison with the Dex− group in both human and rat tenocytes. The mechanical strength of tendons was significantly reduced in the Dex group (68.87 ± 11.07 N) in comparison with the control group (81.46 ± 7.62 N, P = 0.013) after 5 weeks. Tendons in the Dex group were shorter with smaller cross-sectional areas (10.71 ± 0.34 mm2, 1.44 ± 0.22 mm2, respectively) after 5 weeks than those in the control group (11.13 ± 0.50 mm2, P = 0.050, 2.74 ± 0.34 mm2, P < 0.001, respectively).ConclusionsThis finding suggests long-term use of Dex that decreases the expression of type I collagen at molecular and tissue levels both in human and rat Achilles tendons. Furthermore, Dex decreases the mechanical strength of the tendon, thereby increasing the risk of Achilles tendon rupture.

Improved tendon healing by a combination of Tanshinone IIA and miR-29b inhibitor treatment through preventing tendon adhesion and enhancing tendon strength.

Background: Despite significant advances in the materials and methods development used in surgical repair and postoperative rehabilitation, the adhesion formation remains the most common clinical problem in tendon injuries. Therefore, the development of novel therapies is necessary for targeting at preventing tendon adhesion formation and improving tendon strength.Methods: We used rat fibroblasts for in vitro experiments to determine the optimal concentration of TSA in rats, and then set up negative control group, TSA intervention group, mir-29b interference adenovirus intervention group and TSA and mir-29b interference adenovirus co-intervention group. By comparing cell proliferation and protein expression in different group, we verified the effect and mechanism of drugs on fibroblast function. At the same time, the Sprague-Dawley rat Achilles tendon model in vivo was established in this study, which was divided into sham operation group and operation group. Afterwards in the operation group, mir-29b inhibitor and placebo were injected every 3 days respectively. Then the injection inhibitor group was divided into 5 groups which mean TSA was injected into the marked area at 0, 6, 24 and 72 hours after operation for 1 week, finally all of the rats were died at 3 weeks after operation. Through the observation of general properties, histological observation of Achilles tendon injury, biomechanical test and cell and protein expression in rats' tendon cell, the effect of drugs on tendon adhesion formation was analyzed.Results: We demonstrated that the combination of miR-29b inhibitor and tanshinone IIA(TSA) could prevent tendon adhesion and also enhance tendon strength. Mechanically, the miR-29b inhibitor could activate the TGF-β/Smad3 pathway to trigger endogenous pathways and induce a high proliferation of fibroblast. Subsequently, we also found adding TSA after 6 hours of miR-29b treatment gave less cell cytotoxicity in our rat model with better outcome of less tendon adhesion and enhanced strength.Conclusion: We conclude that the use of miR-29b inhibitor at the end of the tendon break could initiate endogenous repair mechanism and subsequently use of TSA should be able to inhibit the exogenous repair mechanism. Therefore, the combination of both treatments could prevent tendon adhesion and ensure tendon strength. Our findings suggested that this approach would be a feasible approach for tendon repair.

A practical design approach for an improved resin-anchored tendon

The use of resin-grouted tendons is a common ground support practice within the mining industry and various tendon designs are available. The support strength of a resin-grouted tendon is often constrained by the resin annulus between the tendon and the borehole. Effective mixing of the resin is typically achieved by ensuring the resin annulus does not exceed a specified maximum limit. Therefore, in some cases, the diameter of the tendon is dictated by the maximum allowable resin annulus and minimum diameter borehole that can be drilled and not by the support design requirements. The installation of tendons with mastic resin capsules is prone to gloving of the installed tendon by the capsule packaging, thereby debonding the tendon from the borehole, and compromising the mixing of the resin surrounding the tendon. This paper documents a practical investigation into the effectiveness of typical resin tendon designs in large annulus installations and the development of an improved tendon design for such cases.

A Horse of a Different Color?: Tensile Strength and Elasticity of Sloth Flexor Tendons.

Tendons must be able to withstand the tensile forces generated by muscles to provide support while avoiding failure. The properties of tendons in mammal limbs must therefore be appropriate to accommodate a range of locomotor habits and posture. Tendon collagen composition provides resistance to loading that contributes to tissue strength which could, however, be modified to not exclusively confer large strength and stiffness for elastic energy storage/recovery. For example, sloths are nearly obligate suspenders and cannot run, and due to their combined low metabolic rate, body temperature, and rate of digestion, they have an extreme need to conserve energy. It is possible that sloths have a tendon "suspensory apparatus" functionally analogous to that in upright ungulates, thus allowing for largely passive support of their body weight below-branch, while concurrently minimizing muscle contractile energy expenditure. The digital flexor tendons from the fore- and hindlimbs of two-toed (Choloepus hoffmanni) and three-toed (Bradypus variegatus) sloths were loaded in tension until failure to test this hypothesis. Overall, tensile strength and elastic (Young's) modulus of sloth tendons were low, and these material properties were remarkably similar to those of equine suspensory "ligaments." The results also help explain previous findings in sloths showing relatively low levels of muscle activation in the digital flexors during postural suspension and suspensory walking.

Effect of bite distance of an epitendinous suture from the repair site on the tensile strength of canine tendon constructs.

To evaluate effects of bite distance of an interlocking horizontal mattress epitendinous suture (IHMES) from the repair site on tensile strength of canine tendon repairs. 72 canine cadaveric superficial digital flexor tendons (SDFTs). Transverse tenotomy was performed, and SDFTs were repaired with a locking-loop construct (LL construct) or 3 LL constructs with IHMES suture bites placed 5 (LL + 5ES construct), 10 (LL + 10ES construct), or 15 (LL + 15ES construct) mm from the transection site (18 SDFTs/group). Constructs were loaded to failure. Load at 1- and 3-mm gapping, yield force, failure load, and failure mode were evaluated. Mean ± SD yield force and failure load for LL constructs were significantly lower than for IHMES constructs. Load at 1- and 3-mm gapping was significantly higher for IHMES constructs. Increasing the bite distance significantly increased construct strength (134.4 ± 26.1 N, 151.0 ± 16.8 N, and 182.1 ± 23.6 N for LL + 5ES, LL + 10ES, and LL + 15ES constructs, respectively), compared with strength for the LL construct. Failure mode differed significantly among constructs when an IHMES was used. Addition of an IHMES to an LL construct led to increased ultimate tensile strength by 2.5 times and significantly reduced gap formation. Increasing the IHMES bite distance increased yield force by 2.1, 2.3, and 2.7 times for bites placed 5, 10, and 15 mm from the tenotomy, respectively. Positioning an IHMES at a greater distance from the repair site provided superior biomechanical strength for tendon repairs in dogs.