Leg Tendon Research Articles

Diagnostic Accuracy of Magnetic Resonance Imaging (MRI) Knee in detecting Anterior Cruciate Ligament (ACL) Tears assuming Arthroscopy as Gold Standard

Background: Anterior cruciate ligament is a core ligament of the knee joint and is vulnerable to injuries in sports and athletics. Timely diagnosis of ACL injuries can result in better management and fast repair. This study explores the diagnostic accuracy of Magnetic resonance imaging (MRI) of knee joint in ACL complete tear. Patients and methods: To decide the diagnostic efficiency awareness, particularity, positive predictive values (PPV), negative predictive values (NPV) worth and demonstrative precision of X-ray in contrast with arthroscopy for identification of upper leg tendon tears of the knee. A total 78 patients were considered in this study with suspicion of ACL rupture. Patients underwent both MRI and arthroscopy for the detection of ACL tears. The outcomes of the MRI were compared with the accepted gold standard, arthroscopy. Results: The mean age of the patients enrolled in the study turned out as 45.1 ± 12.8 (p<0.001). ACL tears were presented in 52.6% of the patients according to both arthroscopy and MRI. According to MRI, there were 39 true positives (TP), 2 false positives (FP), 2 false negatives (FN), and 35 true negatives (TN). It was found out that PPV was 90.3%, NPV was 97.2%, sensitivity was 95.12%, specificity was 94.59%, while accuracy was observed as 94.87%. Conclusion: MRI can serve the patients in diagnosis such that it is non-invasive, cheap and can avoid unwanted arthroscopies in case of ACL tears diagnosis. These results also support the fact that MRI can be used as an alternative to arthroscopy in the Pakistani population. These findings can serve to better plan medical facilities in Pakistan.

Effects of mineralization on the hierarchical organization of collagen-a synchrotron X-ray scattering and polarized second harmonic generation study.

The process of mineralization fundamentally alters collagenous tissue biomechanics. While the structure and organization of mineral particles have been widely studied, the impact of mineralization on collagen matrix structure, particularly at the molecular scale, requires further investigation. In this study, synchrotron X-ray scattering (XRD) and polarization-resolved second harmonic generation microscopy (pSHG) were used to study normally mineralizing turkey leg tendon in tissue zones representing different stages of mineralization. XRD data demonstrated statistically significant differences in collagen D-period, intermolecular spacing, fibril and molecular dispersion and relative supramolecular twists between non-mineralizing, early mineralizing and late mineralizing zones. pSHG analysis of the same tendon zones showed the degree of collagen fibril organization was significantly greater in early and late mineralizing zones compared to non-mineralizing zones. The combination of XRD and pSHG data provide new insights into hierarchical collagen-mineral interactions, notably concerning possible cleavage of intra- or interfibrillar bonds, occlusion and reorganization of collagen by mineral with time. The complementary application of XRD and fast, label-free and non-destructive pSHG optical measurements presents a pathway for future investigations into the dynamics of molecular scale changes in collagen in the presence of increasing mineral deposition.

Fast dual-echo estimation of apparent long T2 fraction using ultrashort echo time magnetic resonance imaging in tibialis tendons and its osteoporosis-related differences in women.

Tendon and bone comprise a critical interrelating unit. Bone loss, including that seen with osteopenia (OPe) or osteoporosis (OPo), may be associated with a reduction in tendon quality, though this remains incompletely investigated. Clinical magnetic resonance imaging (MRI) sequences cannot directly detect signals from tendons because of the very short T2. Clinical MRI may detect high-graded abnormalities by changes in the adjacent structures like bone. However, ultrashort echo time MRI (UTE-MRI) can capture high signals from all tendons. To determine if the long T2 fraction, as measured by a dual-echo UTE-MRI sequence, is a sensitive quantitative technique to the age- and bone-loss-related changes of the lower leg tendons. This is a cross-sectional study conducted between January 2018 to February 2020 in the lower legs of 14 female patients with OPe [72±6 years old, body mass index (BMI) =25.8±6.2 kg/m2] and 31 female patients with OPo (73±6 years old, BMI=22.0±3.8 kg/m2), as well as 30 female subjects with normal bone (Normal, 35±18 years old, BMI =23.2±4.3 kg/m2), were imaged on a 3T clinical scanner using a dual-echo 3D Cones UTE sequence. We defined the apparent long T2 signal fraction (aFrac-LongT2) of tendons as the ratio between the signal at the second echo time (TE =2.2 ms) to the UTE signal. The average aFrac-LongT2 and the cross-sectional area were calculated for the anterior tibialis tendons (ATTs) and the posterior tibialis tendons (PTTs). The Kruskal-Wallis rank test was used to compare the differences in aFrac-LongT2 and the cross-sectional area of the tendons between the groups. The aFrac-LongT2 of the ATTs and PTTs were significantly higher in the OPo group compared with the Normal group (22.2% and 34.8% in the ATT and PTT, respectively, P<0.01). The cross-sectional area in the ATTs was significantly higher for the OPo group than in the Normal group (Normal/OPo difference was 28.7, P<0.01). Such a difference for PTTs did not reach the significance level. Mean aFrac-LongT2 and cross-sectional area in the OPe group were higher than the Normal group and lower than the OPo group. However, the differences did not show statistical significance, likely due to the higher BMI in the OPe group. Dual-echo UTE-MRI is a rapid quantification technique, and aFrac-LongT2 values showed significant differences in tendons between Normal and OPo patients.

Relationship between tendon elastography and clinical and ultrasound enthesitis scores in patients with psoriasis or psoriatic arthritis

Aim: To determine the existence of a correlation between the elastographic study of the patellar and Achilles tendons and the enthesis evaluation in patients with psoriasis with or without psoriatic arthritis. Methods: Observational, cross-sectional study. Patients with psoriasis, psoriatic arthritis and healthy controls were included. The elastography results of the patellar and Achilles tendons of the non-dominant leg of the three groups were compared and tested for correlation with the Madrid Sonographic Enthesis Index (MASEI) score, as well as an entheses clinical evaluation score [Spondyloarthritis Research Consortium of Canada (SPARCC)]. Results: Forty-eight patients were included, 24 with psoriasis and 24 with psoriatic arthritis, as well as 48 healthy controls. Patients with psoriatic arthritis had a higher clinical enthesitis score than patients with psoriasis (8.0 vs. 1.0, P &lt; 0.001). The mean (standard deviation) or median (25–75 percentile) of control subjects patellar and Achilles’ tendon stiffness, 127.8 kPa (18.5 kPa) and 198.0 kPa (183.2–212.0 kPa) were significantly higher than observed in patients with psoriatic arthritis, 119.2 kPa (19.7 kPa) and 184.8 kPa (175.5–193.9 kPa; P &lt; 0.001 and P = 0.018, respectively). A strong inverse correlation between MASEI score and the patellar and Achilles’ tendon stiffness was also detected (Spearman’s Rho coefficient of –0.813 and –0.941, respectively). Conclusions: Patients with psoriatic arthritis present less stiffness in those load-bearing tendons than healthy controls. There is an inverse correlation between the enthesis involvement demonstrated by ultrasound and the elastography of these tendons. Tendon elastography can be considered a useful quantitative tool in assessing patients with psoriatic disease.

Systemic epigenome-wide association study of elk treponeme-associated hoof disease

Treponeme-associated hoof disease (TAHD) is an emerging disease of elk (Cervus canadensis) in the U.S. Pacific West. Because environmental epigenetics is the primary molecular process that mediates environmental factor impacts on a host organism and disease, the role of epigenetics in TAHD etiology was examined. The current study was designed to examine potential effects of TAHD on systemic epigenetic modifications in infected elk over a range of TAHD lesion severity. Leg tendons that contain predominantly fibroblast connective tissue cells were used to isolate fibroblast cells for epigenetic analysis in unaffected and TAHD-positive male and female Roosevelt and Rocky Mountain elk. Differential DNA methylation regions (DMRs) between the unaffected and TAHD-positive elk were identified for both female and male elk. The presence of TAHD was associated with alteration of the connective tissue cell epigenetics, and DMR associated genes identified. Therefore, the infected elk were found to have a systemic epigenetic alteration that was associated with the disease, despite pathology being generally limited to feet. If the elk germline epigenetics is altered then generational transmission of susceptibility to TAHD may impact subsequent generations through epigenetic inheritance. This first study of epigenetic changes associated with disease in elk suggests that TAHD promotes a systemic effect on the elk epigenetics which could exert health impacts on the elk.

Challenging the Perceptions of Human Tendon Allografts: Influence of Donor Age, Sex, Height, and Tendon on Biomechanical Properties

Background: The use of allograft tendons has increased for primary and revision anterior cruciate ligament reconstruction, but allograft supply is currently limited to a narrow range of tendons and donors up to the age of 65 years. Expanding the range of donors and tendons could help offset an increasing clinical demand. Purpose: To investigate the effects of donor age, sex, height, and specific tendon on the mechanical properties of a range of human lower leg tendons. Study Design: Descriptive laboratory study. Methods: Nine tendons were retrieved from 39 fresh-frozen human cadaveric lower legs (35 donors [13 female, 22 male]; age, 49-99 years; height, 57-85 inches [145-216 cm]) including: Achilles tendon, tibialis posterior and anterior, fibularis longus and brevis, flexor and extensor hallucis longus, plantaris, and flexor digitorum longus. Tendons underwent tensile loading to failure measuring cross-sectional area (CSA), maximum load, strain at failure, ultimate tensile strength, and elastic modulus. Results from 332 tendons were analyzed using mixed-effects linear regression, accounting for donor age, sex, height, and weight. Results: Mechanical properties were significantly different among tendons and were substantially greater than the effects of donor characteristics. Significant effects of donor sex, age, and height were limited to specific tendons: Achilles tendon, tibialis posterior, and tibialis anterior. All other tendons were unaffected. The Achilles tendon was most influenced by donor variables: greater CSA in men (β = 15.45 mm2; Šidák adjusted P < .0001), decreased maximum load with each year of increased age (β = −17.20 N per year; adjusted P = .0253), and increased CSA (β = 1.92 mm2 per inch; adjusted P < .0001) and maximum load (β = 86.40 N per inch; adjusted P < .0001) with each inch of increased height. Conclusion: Mechanical properties vary significantly across different human tendons. The effects of donor age, sex, and height are relatively small, are limited to specific tendons, and affect different tendons uniquely. The findings indicate that age negatively affected only the Achilles tendon (maximum load) and challenge the exclusion of donors aged >65 years across all tendon grafts. Clinical Relevance: The findings support including a broader range of tendons for use as allografts for anterior cruciate ligament reconstruction and reviewing the current exclusion criterion of donors aged >65 years.

Transcriptomic and Genetic Analyses Identify the Krüppel-Like Factor Dar1 as a New Regulator of Tube-Shaped Long Tendon Development.

To ensure locomotion and body stability, the active role of muscle contractions relies on a stereotyped muscle pattern set in place during development. This muscle patterning requires a precise assembly of the muscle fibers with the skeleton via a specialized connective tissue, the tendon. Like in vertebrate limbs, Drosophila leg muscles make connections with specific long tendons that extend through different segments. During the leg disc development, cell precursors of long tendons rearrange and collectively migrate to form a tube-shaped structure. A specific developmental program underlies this unique feature of tendon-like cells in the Drosophila model. We provide for the first time a transcriptomic profile of leg tendon precursors through fluorescence-based cell sorting. From promising candidates, we identified the Krüppel-like factor Dar1 as a critical actor of leg tendon development. Specifically expressed in the leg tendon precursors, loss of dar1 disrupts actin-rich filopodia formation and tendon elongation. Our findings show that Dar1 acts downstream of Stripe and is required to set up the correct number of tendon progenitors.

Multiscale and multimodal X-ray analysis: Quantifying phase orientation and morphology of mineralized turkey leg tendons

Fibrous biocomposites like bone and tendons exhibit a hierarchical arrangement of their components ranging from the macroscale down to the molecular level. The multiscale complex morphology, together with the correlated orientation of their constituents, contributes significantly to the outstanding mechanical properties of these biomaterials. In this study, a systematic road map is provided to quantify the hierarchical structure of a mineralized turkey leg tendon (MTLT) in a holistic multiscale evaluation by combining micro-Computed Tomography (micro-CT), small-angle X-ray scattering (SAXS), and wide-angle X-ray diffraction (WAXD). We quantify the interplay of the main MTLT components with respect to highly ordered organic parts such as fibrous collagen integrating inorganic components like hydroxyapatite (HA). The microscale fibrous morphology revealing different types of porous features and their orientation was quantified based on micro-CT investigations. The quantitative analysis of the alignment of collagen fibrils and HA crystallites was established from the streak-like signal in SAXS using the Ruland approach and the broadening of azimuthal profiles of the small and wide-angle diffraction peaks. It has been in general agreement that HA crystallites are co-aligned with the nanostructure of mineralized tissue. However, we observe relatively lower degree of orientation of HA crystallites compared to the collagen fibrils, which supports the recent findings of the structural interrelations within mineralized tissues. The generic multiscale characterization approach of this study is relevant to any hierarchically structured biomaterials or bioinspired materials from the μm-nm-Å scale. Hence, it gives the basis for future structure-property relationship investigations and simulations for a wide range of hierarchically structured materials. Statement of significanceMany fibrous biocomposites such as tendon, bone, and wood possess multiscale hierarchical structures, responsible for their exceptional mechanical properties. In this study, the 3-dimensional hierarchical structure, the degree of orientation and composition of mineralized tendon extracted from a turkey leg were quantified using a multimodal X-ray based approach combining small-angle X-ray scattering and wide-angle X-ray diffraction with micro-Computed Tomography. We demonstrate that hydroxyapatite (HA) domains are co-aligned with the nanostructure of mineralized tissue. However, the lower degree of orientation of HA crystallites was observed when compared to the collagen fibrils. The generic multiscale characterization approach of this study is relevant to any hierarchically structured biomaterials or bioinspired materials from the micrometer over the nanometer to the Angström scale level.

Spatial survey of non-collagenous proteins in mineralizing and non-mineralizing vertebrate tissues ex vivo

Bone biomineralization is a complex process in which type I collagen and associated non-collagenous proteins (NCPs), including glycoproteins and proteoglycans, interact closely with inorganic calcium and phosphate ions to control the precipitation of nanosized, non-stoichiometric hydroxyapatite (HAP, idealized stoichiometry Ca10(PO4)6(OH)2) within the organic matrix of a tissue. The ability of certain vertebrate tissues to mineralize is critically related to several aspects of their function. The goal of this study was to identify specific NCPs in mineralizing and non-mineralizing tissues of two animal models, rat and turkey, and to determine whether some NCPs are unique to each type of tissue. The tissues investigated were rat femur (mineralizing) and tail tendon (non-mineralizing) and turkey leg tendon (having both mineralizing and non-mineralizing regions in the same individual specimen). An experimental approach ex vivo was designed for this investigation by combining sequential protein extraction with comprehensive protein mapping using proteomics and Western blotting. The extraction method enabled separation of various NCPs based on their association with either the extracellular organic collagenous matrix phases or the inorganic mineral phases of the tissues. The proteomics work generated a complete picture of NCPs in different tissues and animal species. Subsequently, Western blotting provided validation for some of the proteomics findings. The survey then yielded generalized results relevant to various protein families, rather than only individual NCPs. This study focused primarily on the NCPs belonging to the small leucine-rich proteoglycan (SLRP) family and the small integrin-binding ligand N-linked glycoproteins (SIBLINGs). SLRPs were found to be associated only with the collagenous matrix, a result suggesting that they are mainly involved in structural matrix organization and not in mineralization. SIBLINGs as well as matrix Gla (γ-carboxyglutamate) protein were strictly localized within the inorganic mineral phase of mineralizing tissues, a finding suggesting that their roles are limited to mineralization. The results from this study indicated that osteocalcin was closely involved in mineralization but did not preclude possible additional roles as a hormone. This report provides for the first time a spatial survey and comparison of NCPs from mineralizing and non-mineralizing tissues ex vivo and defines the proteome of turkey leg tendons as a model for vertebrate mineralization.

Visualization of microstructural change affected by mechanical stimulation in tendon healing with a novel tensionless model.

Since the majority of a tendon's dry weight is collagen fibers, tendon healing consists mainly of collagen repair and observing three-dimensional networks of collagen fibers with scanning electron microscopy (SEM) is optimal for investigating this process. In this report, a cell-maceration/SEM method was used to investigate extrasynovial tendon (unwrapped tendon in synovial tissue such as the tendon sheath) healing of an injured Achilles tendon in a rat model. In addition, since mechanical stimulation is important for tendon healing, a novel, tensionless, rat lower leg tendon injury model was established and verified by visualizing the structural change of collagen fibers under tensionless conditions by SEM. This new model was created by transplanting the leg of a rat with a tendon laceration to the back, removing mechanical stimulation. We then compared the process of tendon healing with and without tension using SEM. Under tension, collagen at the tendon stump shows axial alignment and repair that subsequently demarcates the paratenon (connective tissue on the surface of an extrasynovial tendon) border. In contrast, under tensionless conditions, the collagen remains randomly arranged. Our findings demonstrate that mechanical stimulation contributes to axial arrangement and reinforces the importance of tendon tension in wound healing.

Three-dimensional structural interrelations between cells, extracellular matrix, and mineral in normally mineralizing avian leg tendon

The spatial-temporal relationship between cells, extracellular matrices, and mineral deposits is fundamental for an improved understanding of mineralization mechanisms in vertebrate tissues. By utilizing focused ion beam-scanning electron microscopy with serial surface imaging, normally mineralizing avian tendons have been studied with nanometer resolution in three dimensions with volumes exceeding tens of micrometers in range. These parameters are necessary to yield sufficiently fine ultrastructural details while providing a comprehensive overview of the interrelationships between the tissue structural constituents. Investigation reveals a complex lacuno-canalicular network in highly mineralized tendon regions, where ∼100 nm diameter canaliculi emanating from cell (tenocyte) lacunae surround extracellular collagen fibril bundles. Canaliculi are linked to smaller channels of ∼40 nm diameter, occupying spaces between fibrils. Close to the tendon mineralization front, calcium-rich deposits appear between the fibrils and, with time, mineral propagates along and within them. These close associations between tenocytes, tenocyte lacunae, canaliculi, small channels, collagen, and mineral suggest a concept for the mineralization process, where ions and/or mineral precursors may be transported through spaces between fibrils before they crystallize along the surface of and within the fibrils.

Neglected lumbar traumatic spine injury after falling from a tree

This 48-year-old man, previously healthy, presented with a six-month history of progressive low back pain and bilateral pseudo-sciatica of the lower extremities without sphincter disturbances. Physical examination revealed fixed kyphotic posture of the lumbar spine. Straight leg test and tendon reflexes were normal without any neurologic deficits. He reported sustaining a traumatic injury two years earlier secondary to a fall from a tree. At that time, he did not seek medical treatment. Plain radiograph (A) demonstrated regional lumbar kyphosis from L1 to L3 as well as a healed burst fracture of L2 vertebra (star). Spinal lumbar computed tomography scan (B-C) confirmed traumatic kyphotic deformity at L1-L2-L3 and moderate central stenosis at L2. There was also a new joint surface formation and vacuum phenomenon between the anterior vertebral bodies of L1 and L3. The patient was counseled on the need for surgery, but he refused any surgical intervention and insisted on conservative management. Neglected lumbar spinal injuries are rare but serious clinical situations. Their etiologies vary from missed injuries, delayed presentation for treatment, and wrong initial management. The clinical symptoms include spinal and/or radicular pain, scoliotic and/or kyphotic deformity, and neurological deficits. Management of these neglected injuries is difficult with respect to intraoperative difficulties, higher incidence of surgical complications, and subsequent rehabilitation.

Age-related decrease in collagen proton fraction in tibial tendons estimated by magnetization transfer modeling of ultrashort echo time magnetic resonance imaging (UTE-MRI)

Clinical magnetic resonance imaging (MRI) sequences are not often capable of directly visualizing tendons. Ultrashort echo time (UTE) MRI can acquire high signal from tendons thus enabling quantitative assessments. Magnetization transfer (MT) modeling combined with UTE-MRI—UTE-MT-modeling—can indirectly assess macromolecular protons in the tendon. This study aimed to determine if UTE-MT-modeling is a quantitative technique sensitive to the age-related changes of tendons. The legs of 26 young healthy (29 ± 6 years old) and 22 elderly (75 ± 8 years old) female subjects were imaged using UTE sequences on a 3T MRI scanner. Institutional review board approval was obtained, and all recruited subjects provided written informed consent. T1 and UTE-MT-modeling were performed on anterior tibialis tendons (ATT) and posterior tibialis tendons (PTT) as two representative human leg tendons. A series of MT pulse saturation powers (500–1500°) and frequency offsets (2–50 kHz) were used to measure the macromolecular fraction (MMF) and macromolecular T2 (T2MM). All measurements were repeated by three independent readers for a reproducibility study. MMF demonstrated significantly lower values on average in the elderly cohort compared with the younger cohort for both ATT (decreased by 16.8%, p = 0.03) and PTT (decreased by 23.0%, p < 0.01). T2MM and T1 did not show a significant nor a consistent difference between the young and elderly cohorts. For all MRI parameters, intraclass correlation coefficient (ICC) was higher than 0.98, indicating excellent consistency between measurements performed by independent readers. MMF serving as a surrogate measure for collagen content, showed a significant decrease in elderly leg tendons. This study highlighted UTE-MRI-MT techniques as a useful quantitative method to assess the impact of aging on human tendons.

Extrafibrillar matrix yield stress and failure envelopes for mineralised collagen fibril arrays

Bone metabolic diseases such as osteoporosis constitute a major socio-economic challenge. A detailed understanding of the structure-property relationships of bone's underlying hierarchical levels has the potential to improve diagnosis and the ability to treat those diseases, especially with regards to the onset of failure. Therefore, elastic and yield properties of mineralised turkey leg tendon (MTLT), a mineralised tissue that is similar to bone but has a simpler multiscale structure, were investigated. Elastic properties were identified using a multiscale micromechanical model. The input parameters include constituent mechanical properties, volume fractions and inclusion aspect ratios and these were obtained from a wide variety of literature sources. The determined elastic properties were used to formulate micromechanically informed yield surfaces and to identify yield properties of MTLT at the nanometre length scale where failure is first reported to occur. This was done in conjunction with experimental results from the compression of micropillars extracted from individual mineralised collagen fibres. This data was then used to identify micromechanically informed failure envelopes. The shear yield stress of the extrafibrillar matrix, associated with interfibrillar sliding, was identified as 137.65 MPa. The ratio between tensile and compressive yield stress in the Drucker-Prager yield criterion was 0.65. For both criteria apparent yield stress of the mineralised collagen fibril decreased to 25.3–31.4% when varying fibril orientation from 0° to 90°. This study identified yield properties of extrafibrillar matrix using an aligned mineralised tissue. The ability to obtain yield stress data and unloading stiffness from micropillar compression tests of MTLT at the level of the mineralised collagen fibril array and downscaling these into the EM mitigates against possible errors associated with macroscopic stiffness predictions and proved to be an invaluable advantage compared to similar modelling approaches. Results may help to improve computational models that may then be used in pre-clinical testing or development of personalised treatment strategies.

External mechanical work in the galloping racehorse.

Horse locomotion is remarkably economical. Here, we measure external mechanical work of the galloping horse and relate it to published measurements of metabolic cost. Seven Thoroughbred horses were galloped (ridden) over force plates, under a racing surface. Twenty-six full strides of force data were recorded and used to calculate the external mechanical work of galloping. The mean sum of decrements of mechanical energy was -876 J (±280 J) per stride and increments were 2163 J (±538 J) per stride as horses were accelerating. Combination with published values for internal work and metabolic costs for galloping yields an apparent muscular efficiency of 37-46% for galloping, which would be reduced by energy storage in leg tendons. Knowledge about external work of galloping provides further insight into the mechanics of galloping from both an evolutionary and performance standpoint.

Correlations between gene expression and mineralization in the avian leg tendon.

Certain avian tendons have been studied previously as a model system for normal mineralization of vertebrates in general. In this regard, the gastrocnemius tendon in the legs of turkeys mineralizes in a well defined temporal and spatial manner such that changes in the initial and subsequent events of mineral formation can be associated with time and specific locations in the tissue. In the present investigation, these parameters and mineral deposition have been correlated with the expression of several genes and the synthesis and secretion of their related extracellular matrix proteins by the composite tenocytes of the tendon. Quantitative polymerase chain reaction analysis demonstrates that mRNA expression of the non-collagenous genes of bone sialoprotein, osteopontin, and osteocalcin corresponds well with the temporal and spatial onset and progression of mineralization. Immunolocalization separately confirms the synthesis and secretion of these matrix molecules. The expression of other non-collagenous genes such as decorin does not show strong correlation with turkey leg tendon mineralization, and expression of vimentin, a cytoskeletal component which may be regulated by biomechanical factors in the tendon, may lead to inhibition of osteocalcin expression during the development and mineralization of the tissue. The overall results of this work provide insight into direct temporal and spatial relations between the genes and proteins of interest as well as the formation and deposition of mineral in the avian tendon model.

Shear Wave Elastography Measures of the Achilles Tendon: Influence of Time of Day, Leg Dominance and the Impact of an Acute 30-Minute Bout of Running

The mechanical properties of human tendons are likely to be influenced by factors known to affect elastic structures, including patterns of loading and unloading during the day. However, the exact scale and relevance of these variables to tendon stiffness remains unclear. The aim of this study was to (1) measure Achilles tendon (AT) stiffness over the course of the day, (2) examine AT stiffness between dominant and non-dominant standing leg tendons and (3) assess the impact of previous activity on AT stiffness. To assess the impact of time of day and leg dominance, 15 healthy participants (6 females, 9 males; mean age 28 ± 4 year, mean VISA-A score 99.0 ± 1.2) had shear wave elastography (SWE) measures taken at 08:00 h, 12:30 h and 17:00 h on both dominant and non-dominant legs. To assess the impact of exercise, 24 tendons were analysed (7 females, 5 males; mean age 27 ± 4 year, mean VISA-A Score 99.1 ± 1.1) with participants randomly assigned to either a control (CONT) group or a running (RUN) group. The RUN group performed a 30-min run at a subjective intensity of 13–15 on rating of perceived exertion (RPE) scale and had SWE measures taken before, immediately after, 6 h 24 h, 48 h and 72 h following the run. There were no significant differences in AT stiffness over the course of a day or between dominant and non-dominant leg. Significant increases in AT stiffness were noted pre-post run (0.27 m/s, 2.95%, p = 0.037). Leg dominance does not affect SWE values from asymptomatic ATs or change throughout a day, but a 30-min run significantly increases AT stiffness. Leg dominance and timing of clinical appointments are unlikely to affect SWE results, however a prior bout of physical activity may cause changes within the AT resulting in a significantly different SWE measure. Clinicians and researchers should be cautious of interpreting SWE results if weight bearing exercise has been performed beforehand.

Can a continuous mineral foam explain the stiffening of aged bone tissue? A micromechanical approach to mineral fusion in musculoskeletal tissues

Recent experimental data revealed a stiffening of aged cortical bone tissue, which could not be explained by common multiscale elastic material models. We explain this data by incorporating the role of mineral fusion via a new hierarchical modeling approach exploiting the asymptotic (periodic) homogenization (AH) technique for three-dimensional linear elastic composites. We quantify for the first time the stiffening that is obtained by considering a fused mineral structure in a softer matrix in comparison with a composite having non-fused cubic mineral inclusions. We integrate the AH approach in the Eshelby-based hierarchical mineralized turkey leg tendon model (Tiburtius et al 2014 Biomech. Model. Mechanobiol. 13 1003–23), which can be considered as a base for musculoskeletal mineralized tissue modeling. We model the finest scale compartments, i.e. the extrafibrillar space and the mineralized collagen fibril, by replacing the self-consistent scheme with our AH approach. This way, we perform a parametric analysis at increasing mineral volume fraction, by varying the amount of mineral that is fusing in the axial and transverse tissue directions in both compartments. Our effective stiffness results are in good agreement with those reported for aged human radius and support the argument that the axial stiffening in aged bone tissue is caused by the formation of a continuous mineral foam. Moreover, the proposed theoretical and computational approach supports the design of biomimetic materials which require an overall composite stiffening without increasing the amount of the reinforcing material.

Is the Collagen Primed for Mineralization in Specific Regions of the Turkey Tendon? An Investigation of the Protein-Mineral Interface Using Raman Spectroscopy.

The tendons in the turkey leg have specific well-defined areas which become mineralized as the animal ages and they are a thoroughly characterized model system for studying the mineralization process of bone. In this study, nondestructive Raman spectroscopic analysis was used to explore the hypothesis that regions of the turkey tendon that are associated with mineralization exhibit distinct and observable chemical modifications of the collagen prior to the onset of mineralization. The Raman spectroscopy features associated with mineralization were identified by probing (on the micrometer scale) the transition zone between mineralized and nonmineralized regions of turkey leg tendons. These features were then measured in whole tendons and identified in regions of tendon which are destined to become rapidly mineralized around 14 weeks of age. The data show there is a site-specific difference in collagen prior to the deposition of mineral, specifically the amide III band at 1270 cm(-1) increases as the collagen becomes more ordered (increased amide III:amide I ratio) in regions that become mineralized compared to collagen destined to remain nonmineralized. If this mechanism were present in materials of different mineral fraction (and thus material properties), it could provide a target for controlling mineralization in metabolic bone disease.

Curative analysis of suture anchors in repairing delayed Achilles tendon rupture

Objective To summarize the clinical efficacy of suture anchors in repairing the delayed Achilles tendon rupture. Methods From January 2010 to December 2013, 23 patients with delayed Achilles tendon rupture were treated using the suture anchors. There were 19 males and 4 females, at mean age of 43 years (range, 35-53 years). Injury on the left side occurred in 5 patients and right side in 18 patients. Mean time from injury to operation was 26.3 days (range, 21-40 days). Ten patients were diagnosed by ultrasound and the other by MRI. All patients underwent suture anchor fixation without external support. Functional training started at the early stage. Incision complications were detected. Ankle flextion-extension range, American Orthopedic Foot and Ankle Society (AOFAS) score, maximum bilateral leg circumference, tendon rerupture and walking posture were recorded at postoperative 6, 12, 18 and 24 months. Achilles tendon muscular strength was measured with the Lunsford-Perry heel-rise test. Results Follow-up was 24 months. All incisions healed by first intention without sural nerve injury, adherence with skin and deep infection. Six months after operation, the ankle range of motion was dorsiflexion 10.8° (range, 9-15°) and plantar flexion 43.8° (range, 40-48°), with no significant difference in comparison to the health side (P>0.05). AOFAS score differed significantly before and after operation (P<0.01). Maximal leg circumference was 38.2 cm in the health side versus 35.8 cm in the injury side (P<0.05), but the difference was no more than 3 cm. All patients completed 25 times heel raising without difficulty. Four patients walked with a slight limp and recovered from the limp 12 months after operation. No Achilles tendon ruptured again during the follow-up time. Conclusions Repairing the old Achilles tendon rupture with suture anchors can supply strongly strain between broken ends of the tendon, and the outer cast is not needed after operation. Complications are less and functional practice can be commenced in the early postoperative period for better function restoration. Key words: Achilles tendon; Ligaments; Suture anchor