Flexor hallucis longus tendon morphology in dancers clinically diagnosed with tendinopathy.

PURPOSE: The unique demands of dance technique make dancers more prone to certain pathologies especially of the foot and ankle. Flexor hallucis longus (FHL) tendinopathy, colloquially known as "dancer's tendinopathy," is common in dancers and not well studied. The purpose of this study was to assess if morphological alterations in tendon structure occur as an adaptive response to dance activity by comparing the FHL tendon in dancers to non-dancers, and if pathology further alters tendon morphology in dancers clinically diagnosed with tendinopathy. METHODS: Three groups of ten participants were recruited (healthy non-dancers, healthy dancers, and dancers with FHL tendinopathy). Ultrasound images of the FHL tendons were analyzed for macromorphology by measuring the tendon thickness. The micromorphology was analyzed by determining the peak spatial frequency radius of the tendon. Our study did find increased tendon proper and composite tendon thickness in dancers with tendinopathy but no difference between asymptomatic dancers and non-dancers. RESULTS: There was no significant difference in micromorphology found between any of the groups. As expected, dancers with tendinopathy demonstrated increased composite tendon and tendon proper thickness however, there was no evidence of adaptive thickening of the FHL tendon as might be expected for the dance population. There was also no evidence of micromorphological changes in the presence of clinically diagnosed FHL tendinopathy. CONCLUSION: Because of the limited normative data for this pathology, these results can help improve diagnosis and therefore treatment for dancers to decrease the impact of this injury on their careers.

Biomimetic Soft Underwater Robot Inspired by the Red Muscle and Tendon Structure of Fish.

Underwater robots are becoming increasingly important in various fields. Fish robots are attracting attention as an alternative to the screw-type robots currently in use. We developed a compact robot with a high swimming performance by mimicking the anatomical structure of fish. In this paper, we focus on the red muscles, tendons, and vertebrae used for steady swimming of fish. A robot was fabricated by replacing the red muscle structure with shape memory alloy wires and rigid body links. In our previous work, undulation motions with various phase differences and backward quadratically increasing inter-vertebral bending angles were confirmed in the air, while the swimming performance in insulating fluid was poor. To improve the swimming performance, an improved robot was designed that mimics the muscle contractions of mackerel using a pulley mechanism, with the robot named UEC Mackerel. In swimming experiments using the improved robot, a maximum swimming speed of 25.8 mm/s (0.11 BL/s) was recorded, which is comparable to that of other soft-swimming robots. In addition, the cost of transport (COT), representing the energy consumption required for robot movement, was calculated, and a minimum COT of 0.08 was recorded, which is comparable to that of an actual fish.

Características del tendón rotuliano y de Aquiles en jugadores senior de bádminton / Characteristics of the patellar and Achilles tendon in senior badminton players

Los objetivos del estudio fueron describir las propiedades estructurales y mecánicas de los tendones rotuliano y de Aquiles en jugadores senior (>35 años) de bádminton y detectar posibles asimetrías entre el lado dominante y no dominante. La muestra estuvo compuesta por 206 jugadores senior de bádminton (Edad: 52.2±9.6 años) que participaron en el campeonato de Europa Senior en 2018. Se evaluaron las propiedades estructurales (grosor, anchura y área de sección transversal) por medio de un ecógrafo Logiq® S8 y las propiedades mecánicas (elasticidad, tono, rigidez e índice de elastografía) con miotonometría y sonoelastografía de los tendones rotuliano y de Aquiles. Los resultados mostraron que fueron mayores el grosor (5.34±19.90%, p = 0.027) y la anchura (1.57±8.52%, p=0.036) en el tendón de Aquiles no dominante mientras que el tendón rotuliano dominante mostró unos valores mayores para el tono (2.09±12.96%, p=0.002) y para la rigidez (4.41±21.11%, p=0.002) respecto al no dominante. (AU)

The purposes of the study were to describe the structural and mechanical properties of the patellar and Achilles tendons in senior badminton players (>35 years) and to detect possible asymmetries between dominant and non-dominant lower limb. Two hundred and six senior badminton players (52.2±9.6 years old) who participated in the 2018 Senior European Championship volunteered to participate in the study. The structural properties (thickness, width and cross-sectional area) by a Logiq® S8 ultrasound system and the mechanical properties (elasticity, tone, stiffness and elastography index) with myotonometry and sonoelastography of the patellar and Achilles tendons were assessed. Non-dominant Achilles tendon showed greater values for the thickness (5.34±19.90%, p=0.027) and width (1.57±8.52%, p=0.036) than those of the dominant tendon, while the dominant patellar tendon showed higher values for tone (2.09±12.96%, p=0.002) and stiffness (4.41±21.11%, p=0.002) compared to the non-dominant one. (AU)

An AFM study of the nanostructural response of New Zealand white rabbit Achilles tendons to cyclic loading.

The nanostructural response of New Zealand white rabbit Achilles tendons to a fatigue damage model was assessed quantitatively and qualitatively using the endpoint of dose assessments of each tendon from our previous study. The change in mechanical properties was assessed concurrently with nanostructural change in the same non-viable intact tendon. Atomic force microscopy was used to study the elongation of D-periodicities, and the changes were compared both within the same fibril bundle and between fibril bundles. D-periodicities increased due to both increased strain and increasing numbers of fatigue cycles. Although no significant difference in D-periodicity lengthening was found between fibril bundles, the lengthening of D-periodicity correlated strongly with the overall tendon mechanical changes. The accurate quantification of fibril elongation in response to macroscopic applied strain assisted in assessing the complex structure-function relationship in Achilles tendons.

The influence of glycosaminoglycan proteoglycan side chains on tensile force transmission and the nanostructural properties of Achilles tendons.

This study investigates the nanostructural mechanisms that lie behind load transmission in tendons and the role of glycosaminoglycans (GAGs) in the transmission of force in the tendon extracellular matrix. The GAGs in white New Zealand rabbit Achilles tendons were enzymatically depleted, and the tendons subjected to cyclic loading at 6% strain for up to 2 hr. A nanoscale morphometric assessment of fibril deformation under strain was linked with the decline in the tendon macroscale mechanical properties. An atomic force microscope (AFM) was employed to characterize the D-periodicity within and between fibril bundles (WFB and BFB, respectively). By the end of the second hour of the applied strain, the WFB and BFB D-periodicities had significantly increased in the GAG-depleted group (29% increase compared with 15% for the control, p < .0001). No statistically significant differences were found between WFB and BFB D-periodicities in either the control or GAG-depleted groups, suggesting that mechanical load in Achilles tendons is uniformly distributed and fairly homogenous among the WFB and BFB networks. The results of this study have provided evidence of a cycle-dependent mechanism of damage accumulation. The accurate quantification of fibril elongation (measured as the WFB and BFB D-periodicity lengths) in response to macroscopic applied strain has assisted in assessing the complex structure-function relationship in Achilles tendon.

Introduction.

Just like the first edition of this widely successful book the second edition provides latest updates of our understanding of pathophysiology, pathology, clinical presentation and treatment of heritable soft connective tissue diseases. In addition, new knowledge of not only structures but also of functions of basic components of connective tissues (e.g., collagen), and of organs such as tendons has been added as well. Moreover, readers will learn more about new syndromes and new subgroups of previously described syndromes and disorders as well. The authors are not only prominent investigators in their field, but they are also good writers and that should provide an additional incentive for interested readers.

Contribution of glycosaminoglycans to the structural and mechanical properties of tendons - A multiscale study.

Tendinopathy of the Achilles tendon contributes to a large range of disorders, including mechanical damage and degenerative diseases. Glycosaminoglycans (GAGs), are thought to play a role in the mechanical strength of tendons by forming cross-links between collagen molecules and allowing the transmission of forces between fibrils. This study assessed the response of GAG-depleted tendons to damage induced by fatigue loading, investigating the mechanical damage (stiffness, hysteresis and maximum load), macrostructural changes (tenocyte morphology, fiber anisotropy and waviness) assessed by confocal imaging and nanostructural changes (fibril D-periodicity length) within the same non-viable intact tendons. Changes in fiber waviness and tenocyte shape are strongly correlated to mechanical and nano-structural (D-periodicity elongation) properties in both Control and GAG-depleted tendons. This study supports firstly, the vital role GAGs play as mechanical connectors facilitating the load transfer between the fibrils and their hydrophilic role in facilitating fibril sliding. Secondly, that observed changes in tenocyte shape and fiber waviness correlate with tendon stiffness and other mechanical profiles.

A multiscale study of morphological changes in tendons following repeated cyclic loading.

The response of white New Zealand rabbit Achilles tendons to load was assessed using mechanical measures and confocal arthroscopy (CA). The progression of fatigue-loading-induced damage of the macro- (tenocyte morphology, fiber anisotropy and waviness), as well as the mechanical profile, were assessed within the same non-viable intact tendon in response to prolonged cyclic and static loading (up to four hours) at different strain levels (3%, 6% and 9%). Strain-mediated repeated loading induced a significant decline in mechanical function (p < 0.05) with increased strain and cycles. Mechanical and structural resilience was lost with repeated loading (p < 0.05) at macroscales. The lengthening of D-periodicity correlated strongly with the overall tendon mechanical changes and loss of spindle shape in tenocytes. This is the first study to provide a clear concurrent assessment of form (morphology) and function (mechanics) of tendons undergoing different strain-mediated repeated loading at multiple-scale assessments. This study identifies a variety of multiscale properties that may contribute to the understanding of mechanisms of tendon pathology.

Chronic Nicotine Exposure Minimally Affects Rat Supraspinatus Tendon Properties and Bone Microstructure.

Cigarette smoking is the largest cause of preventable deaths, and a known risk factor for musculoskeletal issues including rotator cuff tendon tears. Tendon degeneration is believed to be due in part to changes in tendon cell health and collagen structure. Several studies have demonstrated that exposure to nicotine negatively impacts tendon healing, but surprisingly, nicotine exposure was shown to increase rat supraspinatus tendon stiffness. In order to address this seeming contradiction, the objective of this study was to comprehensively investigate the effects of long-term (18 weeks) exposure of nicotine on tendon-to-bone microstructural properties in a rat model. We hypothesized that long term subcutaneous nicotine delivery would lead to diminished tendon mechanical properties, decreased bone microstructure in the humeral head, and altered tendon cell morphology compared to age-matched control rats receiving saline. Results demonstrated a small decrease in tendon size and stiffness, with decreased cell density in the tendon midsubstance. However, no differences were found in the enthesis fibrocartilage or in the underlying subchondral or trabecular bone. In conclusion, our study revealed limited effects of nicotine on the homeostatic condition of the supraspinatus tendon, enthesis, and underlying bone. Future studies are needed to ascertain effects of other components of tobacco products.

Collagen XI regulates the acquisition of collagen fibril structure, organization and functional properties in tendon.

Collagen XI is a fibril-forming collagen that regulates collagen fibrillogenesis. Collagen XI is normally associated with collagen II-containing tissues such as cartilage, but it also is expressed broadly during development in collagen I-containing tissues, including tendons. The goals of this study are to define the roles of collagen XI in regulation of tendon fibrillar structure and the relationship to function. A conditional Col11a1-null mouse model was created to permit the spatial and temporal manipulation of Col11a1 expression. We hypothesize that collagen XI functions to regulate fibril assembly, organization and, therefore, tendon function. Previous work using cho mice with ablated Col11a1 alleles supported roles for collagen XI in tendon fibril assembly. Homozygous cho/cho mice have a perinatal lethal phenotype that limited the studies. To circumvent this, a conditional Col11a1flox/flox mouse model was created where exon 3 was flanked with loxP sites. Breeding with Scleraxis-Cre (Scx-Cre) mice yielded a tendon-specific Col11a1-null mouse line, Col11a1Δten/Δten. Col11a1flox/flox mice had no phenotype compared to wild type C57BL/6 mice and other control mice, e.g., Col11a1flox/flox and Scx-Cre. Col11a1flox/flox mice expressed Col11a1 mRNA at levels comparable to wild type and Scx-Cre mice. In contrast, in Col11a1Δten/Δten mice, Col11a1 mRNA expression decreased to baseline in flexor digitorum longus tendons (FDL). Collagen XI protein expression was absent in Col11a1Δten/Δten FDLs, and at ~50% in Col11a1+/Δten compared to controls. Phenotypically, Col11a1Δten/Δten mice had significantly decreased body weights (p < 0.001), grip strengths (p < 0.001), and with age developed gait impairment becoming hypomobile. In the absence of Col11a1, the tendon collagen fibrillar matrix was abnormal when analyzed using transmission electron microscopy. Reducing Col11a1 and, therefore collagen XI content, resulted in abnormal fibril structure, loss of normal fibril diameter control with a significant shift to small diameters and disrupted parallel alignment of fibrils. These alterations in matrix structure were observed in developing (day 4), maturing (day 30) and mature (day 60) mice. Altering the time of knockdown using inducible I-Col11a1-/- mice indicated that the primary regulatory foci for collagen XI was in development. In mature Col11a1Δten/Δten FDLs a significant decrease in the biomechanical properties was observed. The decrease in maximum stress and modulus suggest that fundamental differences in the material properties in the absence of Col11a1 expression underlie the mechanical deficiencies. These data demonstrate an essential role for collagen XI in regulation of tendon fibril assembly and organization occurring primarily during development.

Achilles tendon morphology assessed using image based spatial frequency analysis is altered among healthy elite adolescent athletes compared to recreationally active controls.

OBJECTIVES: Although expected, tendon adaptations in adolescent elite athletes have been underreported. Morphologically, adaptations may occur by an increase in collagen fiber density and/or organization. These characteristics can be captured using spatial frequency parameters extracted from ultrasound images. This study aims to compare Achilles tendon (AT) morphology among sports-specific cohorts of elite adolescent athletes and to compare these findings to recreationally active controls by use of spatial frequency analysis. DESIGN: Cross-sectional observational study. METHOD: In total, 334 healthy adolescent athletes from four sport categories (ball, combat, endurance, explosive strength) and 35 healthy controls were included. Longitudinal ultrasound scans were performed at the AT insertion and midportion. Intra-tendinous-morphology was quantified by performing spatial frequency analysis assessing eight parameters at standardized ROIs. Increased values in five parameters suggest a higher structural organization, and in two parameters higher fiber density. One parameter represents a quotient combining both organization and fiber density. RESULTS: Among athletes, only ball sport athletes exhibited an increase in one summative parameter at pre-insertion site compared to athletes from other sport categories. When compared to athletes, controls had significantly higher values of four parameters at pre-insertion and three parameters at midportion site reflecting differences in both, fiber organization and density. CONCLUSIONS: Intra-tendinous-morphology was similar in all groups of adolescent athletes. Higher values found in non-athletes might suggest higher AT fiber density and organization. It is yet unclear whether the lesser structural organization in young athletes represents initial AT pathology, or a physiological adaptive response at the fiber cross-linking level.

The impact of loading, unloading, ageing and injury on the human tendon.

A tendon transfers force from the contracting muscle to the skeletal system to produce movement and is therefore a crucial component of the entire muscle-tendon complex and its function. However, tendon research has for some time focused on mechanical properties without any major appreciation of potential cellular and molecular changes. At the same time, methodological developments have permitted determination of the mechanical properties of human tendons in vivo, which was previously not possible. Here we review the current understanding of how tendons respond to loading, unloading, ageing and injury from cellular, molecular and mechanical points of view. A mechanistic understanding of tendon tissue adaptation will be vital for development of adequate guidelines in physical training and rehabilitation, as well as for optimal injury treatment.

Nicotine impairs intra-substance tendon healing after full thickness injury in a rat model.

Nicotine is harmful to many bodily systems; however, the effects of nicotine on intra-substance tendon healing remain largely unexplored. The purpose of this study was to examine the functional, structural, and biomechanical effects of nicotine on the healing of Achilles tendons in rats after an acute full-thickness injury. Sixty Sprague-Dawley rats were enrolled in this study. Half were exposed to 0.9% saline and half to 61 ng/mL of nicotine for 3 months via subcutaneous osmotic pumps. At 3 months, all rats underwent blunt full thickness transection of the left Achilles tendon and were immobilized for one week in plantarflexion. In-vivo assays were conducted prior to injury, at 21 days, and at 42 days post-injury and included the following: Functional limb assessment, passive joint mechanics, and vascular evaluation. Rats were sacrificed at 21 and 42 days for biomechanical testing and histologic evaluation. Rats exposed to nicotine demonstrated decreased vascularity, greater alteration in gait mechanics, and increased passive ROM of the ankle joint. Biomechanically, the nicotine tendons failed at lower maximum loads, were less stiff, had smaller cross-sectional areas and had altered viscoelastic properties. Histologically, nicotine tendons demonstrated decreased vessel density at the injury site. This study demonstrates that nicotine leads to worse functional outcomes and biomechanical properties in tendons. The decreased vascularity in the nicotine group may suggest an underlying mechanism for inferior tendon healing. Patients should be counseled that using nicotine products increase their risk of poor tendon healing and may predispose them to tendon re-rupture. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

THE DEGREE OF TENDINOSIS IS RELATED TO SYMPTOM SEVERITY AND PHYSICAL ACTIVITY LEVELS IN PATIENTS WITH MIDPORTION ACHILLES TENDINOPATHY.

BACKGROUND: Achilles tendinopathy negatively affects a person's ability to be physically active. However, remaining physically active during the rehabilitation process does not impact clinical outcomes when a pain-monitoring model is followed. There are several factors, such as the progression of pain and structural changes, kinesiophobia, functional impairments, or medical advice, which may explain why some patients become physically inactive while others maintain a physically active lifestyle. PURPOSE: The purposes of this study were 1) to compare the clinical presentation of patients with Achilles tendinopathy with high and low activity levels 2) to examine the relationship between tendon thickening and symptom severity in patients with Achilles tendinopathy and 3) to determine the proportion of patients with Achilles tendinopathy who have a high degree of kinesiophobia and if this proportion differs based on activity level. STUDY DESIGN: Cross-sectional. METHODS: Fifty-three patients with Achilles tendinopathy were dichotomized into low activity (n=30) and high activity (n=23) groups based on their physical activity level. Patient characteristics, symptom severity, kinesiophobia, tendon thickening, and lower leg function were quantified and analyzed to test the study hypotheses. RESULTS: Patients with low activity levels had greater tendon thickening and a larger body mass compared to patients with high activity levels. There were no differences in symptom severity, kinesiophobia, or lower leg function between groups. A negative relationship (r=-0.491; p<0.001) was found between tendon thickening and symptom severity. Thirty-eight percent of patients demonstrated a high degree of kinesiophobia, but the proportion did not differ between groups. CONCLUSION: Patients with Achilles tendinopathy who have low physical activity levels demonstrate greater tendinosis than patients who are highly active. These structural changes are negatively associated with symptom severity. However, symptom severity, kinesiophobia, and functional deficits do not differ between patients with different activity levels. LEVEL OF EVIDENCE: Level 3.

EVALUATING THE PROGRESS OF MID-PORTION ACHILLES TENDINOPATHY DURING REHABILITATION: A REVIEW OF OUTCOME MEASURES FOR MUSCLE STRUCTURE AND FUNCTION, TENDON STRUCTURE, AND NEURAL AND PAIN ASSOCIATED MECHANISMS.

INTRODUCTION: Alterations in tendon structure and muscle performance have been suggested as mechanisms driving improvement in pain and function with mid-portion Achilles tendinopathy (AT). However, few trials have used consistent outcome measures to track differences in muscle structure and function, tendon structure and neural and pain associated mechanisms. OBJECTIVES: 1) Identify the outcomes measures used in trials utilising loading protocols for mid-portion AT that assess muscle structure and function, tendon structure and neural and pain associated mechanisms in order to report on the reliability of the identified measures, and 2) Propose a summary of measures for assessment of muscle structure and function, tendon structure and neural and pain associated mechanisms in patients with AT. DESIGN: Literature Review. DATA SOURCES: Three electronic databases were searched from inception until May 2016 for studies using loading protocols for mid-portion AT. ELIGIBILITY CRITERIA: Randomized and non-randomized trials of loading protocols for mid-portion AT. RESULTS: Twenty-eight studies were included; seven assessed muscle, 21 assessed tendon and two assessed neural and pain associated mechanisms. Evidence suggests that isokinetic dynamometry, eccentric-concentric heel raise tests, single leg drop counter-movement jumps or hopping are the most reliable ways to assess muscular adaptation. Assessment of tendon structure is unlikely to have any benefit given it does not appear to correlate to clinical outcomes. The neural and pain associated mechanisms have not been thoroughly investigated. CONCLUSION: Further research needs to be done to determine the role of muscle, tendon and neural adaptations using reliable outcome measures during the management of mid-portion AT. LEVEL OF EVIDENCE: Level Five.

A Reliable Method for Quantification of Tendon Structure Using B-Mode Ultrasound.

Structure is an important clinical marker of tendon health; however, current standards use qualitative scores that are not strongly reliable. Therefore, the purpose of this study was to establish the reliability of an image-processing technique that quantifies tendon collagen structure using B-mode ultrasound images. Longitudinal images of the Achilles tendon were collected in 12 healthy young adults, and intra- and inter-rater reliability was assessed over multiple image selections and multiple days. Intraclass correlation coefficients were strong (r ≥ 0.71) for all comparisons. These findings demonstrate that quantitative assessments of tendon structure using B-mode ultrasound are reliable.

Different Achilles Tendon Pathologies Show Distinct Histological and Molecular Characteristics.

Reasons for the development of chronic tendon pathologies are still under debate and more basic knowledge is needed about the different diseases. The aim of the present study was therefore to characterize different acute and chronic Achilles tendon disorders. Achilles tendon samples from patients with chronic tendinopathy (n = 7), chronic ruptures (n = 6), acute ruptures (n = 13), and intact tendons (n = 4) were analyzed. The histological score investigating pathological changes was significantly increased in tendinopathy and chronic ruptures compared to acute ruptures. Inflammatory infiltration was detected by immunohistochemistry in all tendon pathology groups, but was significantly lower in tendinopathy compared to chronic ruptures. Quantitative real-time PCR (qRT-PCR) analysis revealed significantly altered expression of genes related to collagens and matrix modeling/remodeling (matrix metalloproteinases, tissue inhibitors of metalloproteinases) in tendinopathy and chronic ruptures compared to intact tendons and/or acute ruptures. In all three tendon pathology groups markers of inflammation (interleukin (IL) 1ß, tumor necrosis factor α, IL6, IL10, IL33, soluble ST2, transforming growth factor ß1, cyclooxygenase 2), inflammatory cells (cluster of differentaition (CD) 3, CD68, CD80, CD206), fat metabolism (fatty acid binding protein 4, peroxisome proliferator-activated receptor γ, CCAAT/enhancer-binding protein α, adiponectin), and innervation (protein gene product 9.5, growth associated protein 43, macrophage migration inhibitory factor) were detectable, but only in acute ruptures significantly regulated compared to intact tendons. The study gives an insight into structural and molecular changes of pathological processes in tendons and might be used to identify targets for future therapy of tendon pathologies.

Plantaris Excision and Ventral Paratendinous Scraping for Achilles Tendinopathy in an Athletic Population.

BACKGROUND: Achilles tendinopathy is a frequent problem in high-level athletes. Recent research has proposed a combined etiologic role for the plantaris tendon and neovascularization. Both pathologies can be observed on ultrasound imaging.(1,13) However, little is known about the change in structure of the Achilles tendon following the surgical treatment of these issues. The purpose of the study was to assess if excising the plantaris and performing ventral paratendinous "scraping" of the neovascularization improved symptoms of Achilles tendinopathy and whether there was a change in the fibrillar structure of the tendon with ultrasound tissue characterization (UTC) following this operation. METHODS: This prospective consecutive case series included 15 professional/semiprofessional athletes (17 Achilles tendons) who underwent plantaris excision and paratendinous scraping to treat noninsertional Achilles tendinopathy. The plantaris tendon was excised if adherent to the Achilles tendon, and the area of neovascularization for scraping was demarcated on preoperative imaging. Preoperative and postoperative Victorian Institute of Sports Assessment-Achilles (VISA-A) scores were taken. UTC was performed on 11 of 17 tendons preoperatively and postoperatively. The mean follow-up was for 25 months. RESULTS: Fourteen of 15 patients had a successful outcome after the surgery. The mean VISA-A improved from 51 to 95 (p=.0001). There was a statistically significant (p=.04) improvement in the aligned fibrillar structure of the tendon confirmed with UTC scanning following surgery from 90% (±8) to 96% (±5). CONCLUSION: This group of high-level athletes derived an excellent clinical result from this operation. Furthermore, UTC scanning offered an objective method to evaluate the healing of Achilles tendons. LEVEL OF EVIDENCE: Level IV, case series.

Evaluation of Achilles and patellar tendinopathy with greyscale ultrasound and colour Doppler: using a four-grade scale.

PURPOSE: In tendon research, using ultrasound (US), studies often refer to tendon thickness, structural abnormalities and neovascularisation. The reliability concerning these measurements and evaluations is seldom reported. The aim of this study was to assess the intra- and inter-observer reliability for quantitative measures (thickness) and qualitative evaluations (structure and neovascularisation) of symptomatic and asymptomatic Achilles and patellar tendons with US and colour Doppler using a modified Öhberg score. METHODS: Twenty-eight consecutive patients with symptomatic and asymptomatic Achilles (n = 27) and patellar tendons (n = 26) were included. Tendon anteroposterior thickness was measured. Tendon structure and neovascularisation were evaluated using a modified Öhberg score. US-images were evaluated twice by four independent observers. RESULTS: Mean thickness for Achilles and patellar tendons was 8.4 mm (±2.0) and 5.5 mm (±1.7), respectively. The reliability for measures of distance was high all over (ICC = 0.963-0.999). A moderate-strong correlation was found between observers concerning evaluation of neovascularisation (r = 0.767-0.992) and poor-moderate correlation concerning evaluation of structural changes (r = 0.379-0.837). Intra-observer reliability was moderate strong for evaluations of both tendon structure (k = 0.537-0.873) and neovascularisation (k = 0.639-0.864). CONCLUSIONS: With a strict method for how to measure tendon thickness and set criteria for evaluating structural changes and amount and distribution of neovascularisation, US and colour Doppler is a reliable method for evaluating Achilles and patellar tendons. The modified, 4-graded, Öhberg score was found to be a reproducible instrument for assessment of tendon structure and neovascularisation.

Gelatin yarns inspired by tendons--structural and mechanical perspectives.

Tendons are among the most robust structures in nature. Using the structural properties of natural tendon as a foundation for the development of micro-yarns may lead to innovative composite materials. Gelatin monofilaments were prepared by casting and spinning and small yarns--with up to ten filaments--were assembled into either parallel or 15° twisted yarns. The latter were intended as an attempt to generate mechanical effects similar to those arising from the crimp pattern in tendon. The mechanical properties of parallel and 15° twisted gelatin yarns were compared. The effect of an increasing number of filaments per yarn was also examined. The mechanical properties were mostly affected by the increasing number of filaments, and no benefit arose from twisting small yarns by 15°. However, since gelatin filaments are elasto-plastic rather than fully elastic, much increased toughness (by up to a factor of five for a ten filament yarn) can be achieved with yarns made of elasto-plastic filaments, as demonstrated by experiments and numerical simulations. The resulting effect shows some resemblance to the effect of crimp in tendons. Finally, we developed a dependable procedure to measure the toughness of single filaments based on the test of a yarn rather than on a large number of individual filament tests.