Search Results (2,093)

Orthobiologic treatments such as platelet-rich plasma and stem cell therapies are increasingly used to support the healing of tendons, ligaments, and joints. This perspective proposes applying periodization—a structured, progressive model borrowed from athletic training—to rehabilitation following orthobiologic interventions in order to improve functional outcomes. The framework is organized into sequential phases that align with biological stages of healing. Early phases emphasize pain control, inflammation management, and safe, controlled mobility. Rehabilitation then progresses toward gradually increasing load bearing and strength, and toward more specific exercises to promote tissue regeneration while reducing the risk of re-injury. In later phases (mesocycles), the model highlights the importance of neuroplastic adaptations for sustained functional recovery, including neurogenesis, synaptic plasticity, and functional remodeling to safer RTP for athletes. A key advantage of this approach is its adaptability: progression can be individualized according to a patient’s recovery trajectory and response to loading. By aligning rehabilitation progression with intrinsic healing processes and integrating physiological and neuromuscular goals, the proposed model aims to maximize regenerative potential across both athletic and non-athletic populations. Overall, this neuroplastic periodized approach offers a practical, evidence-informed structure to guide clinicians in delivering patient-centered regenerative rehabilitation and may help standardize care after orthobiologic procedures. Full article

Background: Chronic Achilles tendon ruptures present a major surgical challenge due to tendon retraction, degeneration, and large defects. Autologous hamstring tendon grafts have emerged as a reliable reconstructive option, yet their biomechanical consequences remain poorly understood. This study investigated whether Achilles tendon reconstruction with semitendinosus and gracilis autografts alters the plantar flexor moment arm and whether such changes affect muscle strength. Methods: A cohort of 25 patients (mean age: 44.5 years) underwent minimally invasive endoscopic reconstruction using hamstring autografts. This secondary salvage procedure was performed in patients with neglected ruptures or failed primary treatment. Five patients were excluded from the original intervention group due to inadequate radiographic quality. Radiographic measurements of the Achilles tendon moment arm and isometric plantar flexor strength assessments were performed at 12 and 24 months postoperatively. Statistical analyses included paired t-tests, Wilcoxon signed-rank tests, and correlation analyses. Results: Results showed a significant shortening of the Achilles tendon moment arm after reconstruction compared with the preoperative imaging length (mean reduction: 6.6 mm; p < 0.0001). Despite this, plantar flexor strength in the operated limb improved significantly over time at 12 and 24 months (+388.6 N at 24 months; p = 0.0067) and did not correlate with the degree of moment arm shortening (p > 0.3). By 24 months, the operated limb demonstrated comparable or greater strength than the contralateral side, with nearly half of the patients achieving substantial clinically meaningful improvements. Conclusions: In conclusion, Achilles tendon reconstruction with hamstring autografts leads to consistent moment arm shortening, yet this does not impair long-term restoration of plantar flexor strength. A progressive rehabilitation program extending up to two years appears essential to optimize recovery and compensate for biomechanical alterations. Full article

Background/Objectives: Platelet-rich plasma (PRP) has become a therapeutic option for tendinopathies. Its clinical efficacy depends on several factors, including the target tendon. The aim of this study was to evaluate the PRP efficacy for tendinopathies in the rotator cuff (RC), Achilles tendon (AT), and patellar tendon (PT). Methods: We conducted a prospective cohort study including patients with RC, AT and PT tendinopathies. Each patient received three multitarget PRP (intratendinous and peritendinous) treatments at intervals of two weeks. Clinical outcomes were assessed at baseline and 6 months using tendon-specific scores (DASH for RC, VISA-A for AT and VISA-P for PT). Responders were identified based on the Minimal Clinically Important Improvement (MCII). Comparative statistical tests and multivariate regression were performed for the analysis. Results: A total of 49 patients were included (RC: 15, AT: 18, PT: 16). The number of responders at 6 months was 33 (67.4%), with 11 (73.3%) in the RC Group, 14 (75.0%) in the AT Group and 8 (50.0%) in the PT Group. The RC and AT patients experienced a significant improvement according to their scores (p < 0.001), which was not seen in the PT group (p = 0.065). The percentage of responders was higher in women (12/13, 92.3%) than men (21/36, 58.3%) (p = 0.025). Conclusions: Repeated intratendinous and peritendinous PRP injections in RC, AT, and PT tendinopathy improved joint-related function six months after treatment. This improvement was less pronounced in patients with PT and the proportion of responders was higher among women. Full article

Background: Surgical tendon rupture repair suffers from scar formation, leading to tendons with inferior mechanics and consequently to re-ruptures, as well as from adhesion formation to the surrounding tissue, reducing the range of motion. In an approach of re-purposing the phytochemical Bakuchiol to be incorporated in the polymer DegraPol^® (DP), we fabricated a novel implant material by emulsion electrospinning. Methods: To characterize the emulsion electrospun novel materials, we used Scanning Electron Microscopy (SEM) to determine the fiber diameter and pore size. In addition, we used Fourier Transformed Infrared Spectroscopy (FTIR). Finally, we planted the materials onto the chorioallantoic membrane of the chicken embryo (CAM assay) to assess tissue integration and collagen expression. Results: While the pure DP meshes were very well integrated in the CAM assay and showed a significantly higher collagen deposition within the scaffold, the DP + Bakuchiol meshes exhibited poor tissue integration, showing rather the beginning of a fibrous encapsulation. Conclusions: The novel electrospun material DP + Bakuchiol could be used as an anti-adhesion barrier to prevent tendon adhesion. Full article

Background/Objectives: Tendon injuries are a common cause of emergency department presentation and impose a substantial socioeconomic burden. Despite advances in surgical techniques, rupture rates after primary repair remain at 3.1–11.7%. Contemporary repairs typically combine at least four core strands with epitenon sutures to achieve sufficient tensile strength while limiting bulk. Increasing the number of core strands improves strength but may impair gliding and healing. Looped core sutures increase the effective strand number without additional knots or passes, potentially allowing omission of the epitenon suture and thus limiting repair complexity and bulk. The objective was to determine whether six- or eight-strand looped core suture techniques provide sufficient tensile strength to allow omission of an epitenon suture without excessive repair bulk, compared with a conventional four-strand Adelaide repair. Methods: One hundred and twenty human flexor digitorum profundus tendons were harvested from fresh-frozen anatomical specimens and allocated to six groups: Adelaide (four-strand) ± epitenon suture, six-strand ± epitenon suture, and eight-strand ± epitenon suture. Repairs were performed in zone II. The cross-sectional area (CSA) was measured before and after repair to quantify bulkiness. Tendons were tested to failure using axial tensile loading, and the failure mode was recorded. Results: The Adelaide with epitenon suture, six-strand with epitenon suture, and eight-strand with epitenon suture demonstrated significantly higher load to failure than the Adelaide without epitenon suture. The eight-strand without epitenon suture achieved a load to failure comparable to the Adelaide with epitenon suture, while also resulting in a smaller increase in CSA. The Adelaide with epitenon suture showed the greatest increase in CSA, while the six-strand without epitenon suture showed the smallest increase in CSA. Suture breakage was the predominant failure mode. Conclusions: An eight-strand looped core suture without epitenon suture provides comparable tensile strength to the conventional Adelaide repair with epitenon suture while minimizing repair bulk. The six-strand with epitenon suture demonstrated similar tensile strength to higher-strand techniques and may represent a mechanically adequate alternative with less tissue manipulation. These findings support a more individualized approach to flexor tendon repair, in which the choice of repair construct can be tailored to biomechanical demands and clinical context rather than applying a single uniform technique. Full article

Objectives: To investigate the association between calcaneal bump height and hindfoot radiographic parameters on weight-bearing lateral radiographs in adult males with Progressive Collapsing Foot Deformity (PCFD), and to determine whether posterior calcaneal morphology differs between feet with and without PCFD-related flatfoot alignment. Materials: We retrospectively reviewed 583 men (1166 feet), aged 17–46 years, who underwent standing weight-bearing lateral foot radiographs between 1 January 2024 and 31 August 2025. Radiographic measurements included calcaneal pitch, Meary’s angle, navicular height, tibiocalcaneal angle, Böhler’s angle, Fowler–Philip angle, calcaneal bump height, and additional calcaneal morphological indices. A flatfoot alignment consistent with PCFD was defined as a calcaneal pitch < 18°. Receiver operating characteristic (ROC) analysis and multivariable logistic regression were performed to assess diagnostic performance and identify parameters independently associated with flatfoot alignment. Results: Flatfoot alignment was identified in 232 feet (19.9%) from 153 patients (26.2%). Compared with normally aligned feet, the flatfoot group demonstrated significantly lower navicular height, calcaneal bump height, and Böhler’s angle, along with higher tibiocalcaneal and Meary’s angles (all p < 0.001). ROC analysis showed navicular height to be the most accurate diagnostic parameter (AUC = 0.75), followed by the tibiocalcaneal angle (AUC = 0.69). Multivariable logistic regression revealed that navicular height ≤ 52.7 mm, tibiocalcaneal angle > 64.6°, Böhler’s angle ≤ 32.9°, Meary’s angle > 4.9°, calcaneal bump height ≤ 3.9 mm, and Fowler–Philip angle > 61.1° were independently associated with flatfoot alignment (Nagelkerke R² = 0.293, p < 0.001). Conclusions: Calcaneal bump height is reduced in PCFD and reflects posterior calcaneal remodelling associated with hindfoot malalignment and medial arch collapse. Although not a primary diagnostic parameter, calcaneal bump height provides complementary morphological information that may inform surgical planning and osteotomy strategy aimed at restoring physiologic hindfoot biomechanics and Achilles tendon loading in patients with PCFD. Full article

Objectives: We aimed to evaluate Achilles tendon stiffness characteristics in asymptomatic patients with psoriatic arthritis (PsA) using shear wave elastography (SWE). Methods: In this prospective case–control study, 34 asymptomatic PsA patients and 34 age- and sex-matched healthy controls underwent bilateral Achilles tendon evaluation with grayscale ultrasonography and SWE. Tendon thickness was measured 3 cm proximal to the calcaneal insertion. Shear-wave velocity (m/s) and Young’s modulus (kPa) were obtained under standardized acquisition conditions, including five-star motion stability and ≥90% reliability. Results: Achilles tendon morphology and thickness did not differ between PsA patients and controls (p > 0.05). In contrast, SWE demonstrated higher tendon stiffness in the PsA group. Mean shear-wave velocity was significantly greater in PsA patients for both the left (4.89 ± 2.52 m/s vs. 3.23 ± 0.41 m/s; p < 0.001) and right tendons (4.88 ± 1.94 m/s vs. 3.12 ± 0.30 m/s; p < 0.001), with corresponding increases in Young’s modulus (all p < 0.001). SWE demonstrated good group discrimination, with shear-wave velocity achieving AUC values of up to 0.90 in differentiating PsA patients from healthy controls. Conclusions: SWE may reflect biomechanical tendon alterations in PsA, even in the absence of clinical symptoms, and may serve as a complementary imaging tool in the assessment of tendon involvement. Full article

Achilles tendon rupture often leads to poor functional recovery due to limited self-healing, with mitochondrial dysfunction in tendon stromal cells (TSCs) being a key factor in disease progression. Here, we developed adipose-derived stromal cell (ADSC) membrane-coated mitochondria (Mito-NPs) to target this dysfunction and evaluate their therapeutic potential for tendon repair. Mito-NPs exhibited uniform size, stable surface charge, and effective membrane coating. In lipopolysaccharide-induced inflammatory TSCs, Mito-NPs enhanced oxidative phosphorylation, improved mitochondrial metabolic homeostasis, and reshaped gene expression profiles to normalize TSC functional phenotypes, including inflammation, migration, and collagen synthesis. When encapsulated in a reactive oxygen species (ROS)-responsive hydrogel (Mito-NPs@HG) and implanted into rat Achilles tendon injuries, Mito-NPs@HG improved gait function, decreased local inflammation, and promoted histological repair of damaged tendons by enhancing collagen organization and reducing inflammation. Our findings demonstrate that ADSC membrane-coated mitochondria effectively rescue TSC dysfunction and facilitate tendon regeneration, providing a promising translational strategy for treating tendon injuries. Full article

This work introduces an integrated Material Point Method (MPM) framework for optimizing tendon-driven hyperelastic robots under extreme 3D deformations. To overcome the mesh distortion limitations of the traditional FEM at large strains, we develop a coupled MPM–tendon hyperelastic model that integrates Yeoh constitutive laws with discrete tendon actuation forces. The model enables robust simulation of anisotropic stress propagation through Lagrangian particle tracking and Eulerian grid discretization, eliminating mesh entanglement artifacts. A strain-gradient-driven tendon path algorithm ensures mechanical efficiency using Fréchet distance-based similarity metrics and curvature smoothness screenin, enforcing spatial continuity in complex topologies. Validation demonstrates: (1) Sub 3 mm geometric errors and about 89% volumetric overlap in worm-inspired deformations; (2) optimal computational efficiency at 0.4–0.6 mm grid densities, balancing accuracy and resource overhead; and (3) projected alignment errors of 0.8 mm (XY), 1.3 mm (XZ), and 2.9 mm (YZ) in multi-view spatial analyses. The framework achieves about 89% ± 2% volumetric overlap in quadrupedal morphing via agonist–antagonist tendon optimization, demonstrating efficacy for extreme 3D deformation control. Full article

The exceptional mechanical strength and toughness of collagen arise from its well-defined hierarchical architecture. Conventional methods for obtaining collagen aggregates (CAs), such as direct extraction from native tissues or acid swelling followed by mechanical processing, offer limited control over dimensional uniformity and provide little insight into the underlying exfoliation mechanisms. To overcome these challenges, this study introduces a novel strategy that leverages insights into the hierarchical interactions within collagen. We employ the ionic liquid 1-allyl-3-methylimidazolium chloride ([AMIM]Cl) as an exfoliating agent to successfully isolate fibrous CAs from native bovine tendon. By precisely modulating temperature and processing time, we achieve CAs with tunable mesoscale dimensions (diameter 0.9–1.1 μm, length > 160 μm). Molecular dynamics simulations reveal that [AMIM]Cl disrupts the intramolecular hydrogen-bonding network within collagen, thereby facilitating controlled exfoliation. These exfoliated aggregates serve as fundamental building blocks for fabricating collagen films. The resulting materials exhibit robust mechanical integrity, high transparency, reversible pH-responsive behavior, and excellent biocompatibility as verified by cytotoxicity assays, which together underscore their potential as versatile biomaterial platforms. Furthermore, the integration of single-walled carbon nanotubes yields conductive composites with confirmed electrical functionality. This study thus presents an innovative pathway for the precision processing of collagen and advances the design of high-performance collagen-based biomaterials. Full article

Backgrounds/Objectives: Fatty infiltration (FI) of rotator cuff (RC) muscles is a critical prognostic factor after surgical repair. While the Goutallier–Fuchs grading system is widely used, its reproducibility is often debated. This study aimed to validate a previously reported three-dimensional (3D) magnetic resonance imaging (MRI)-based volumetric quantification method by comparing it with histologic findings in a chronic rotator cuff tear (RCT) rabbit model. Methods: Eighteen shoulders from nine rabbits were randomly assigned to three groups (n = 6 each): repair (A), chronic tear (B), and control (C). In groups A and B, a chronic RCT model was established by detaching the supraspinatus tendon, with group A receiving repair after six weeks. At 12 weeks after repair, 7.0T MRI was performed, and volumetric quantification of intra-muscular fat was performed using semi-automated 3D Slicer software. Histologic fat proportion was measured via Oil Red O staining and ImageJ analysis. Results: The muscle weight and MRI-based muscle volume were significantly lower in group B than group C (p < 0.05). The radiologically measured fat proportion was significantly higher in groups A (1.8 ± 0.8) and B (2.8 ± 0.7) compared to group C (0.5 ± 0.4, p < 0.001). Histologic analysis showed a corresponding pattern (3.0 ± 1.2%, 5.2 ± 1.0%, 1.7 ± 1.0% for groups A, B, and C, respectively; p < 0.001). A strong positive correlation was identified between the radiologic and histologic measurements of FI (r = 0.784, p < 0.001). Conclusions: Direct histologic comparison validates the reliability of 3D MRI-based volumetric quantification for evaluating FI of the RC muscle in a chronic RCT rabbit model. This objective approach may address the inherent limitations of the conventional qualitative grading system. Full article

This systematic review focuses on the effect of concurrent high-intensity interval training (HIIT) and resistance training on musculoskeletal function in adult individuals. Four electronic databases (PubMed, Web of Science Core Collection, Scopus, and PsycINFO) were searched for controlled trials in older or middle-aged adults, in recreationally exercising adults, and in athletic or tactical populations, which completed parallel HIIT and resistance training and described musculoskeletal responses to the intervention up to 30 November 2025. A total of 18 trials fulfilled the eligibility criterion and were synthesized narratively across the domains of maximal strength, explosive performance, neuromuscular activity, muscle morphology and architecture, tendon-related outcomes, and adherence and safety. Most 8- to 12-week interventions maintained two to three weekly resistance sessions and were designed in time-effective HIIT formats, increasing or preserving maximal strength in older subjects as well as younger ones that were trained. Explosive performance metrics, including both jump and sprint tasks, were usually preserved or even improved by the maintenance of the power-oriented component in resistance-based exercise sessions. The limited electromyography data indicated improved neuromuscular activation during submaximal tasks, particularly in older subjects, whereas some studies reported subtle increases or maintenance of muscle size and selective architectural patterns during application of progressive loading. Tendon-specific adaptations are difficult to measure, as imaging was seldom available, but functional tasks influenced by the muscle–tendon unit have been studied in multiple studies. Adherence was good, and adverse events were rare in all studies. Overall, the evidence suggests that well-designed concurrent HIIT and resistance training programs can improve or maintain musculoskeletal performance, although the magnitude and expression of these adaptations vary according to population characteristics and intervention design. Importantly, by integrating neuromuscular, morphological, and performance-related outcomes across diverse adult populations, this review provides a musculoskeletal-centered synthesis that extends prior concurrent training reviews beyond cardiorespiratory or interference-focused perspectives. Full article

Stroke-induced hand motor dysfunction severely limits activities of daily living (ADL). While conventional systems face challenges in portability and sustained actuation accuracy, this work addresses these limitations through an integrated adaptive control framework and a lightweight 10-degrees-of-freedom (DoFs) tendon-driven exoskeleton. The system employs a rigid–flexible coupling design with a wearable mass under 300 g, ensuring compatibility across various finger lengths. The system is implemented via a motor imagery-based brain–computer interface (MI-BCI); by processing 64-channel electroencephalogram (EEG) signals, the system adaptively maps motor intent into three discrete grasp intensity levels (20%, 50%, and 80% maximum voluntary contraction). To reduce cognitive load and enhance system stability during rehabilitation, we propose a novel “Force–Topology Coupling” control paradigm. This paradigm functions as a synergistic filter, leveraging the correlation between intended effort level (IEL) and grasp taxonomy to map intensity levels to ADL-specific grasps (lateral, precision, and power). Validation with healthy subjects demonstrated 0° to 90° joint mobility and the successful execution of 9 ADL tasks. The results verify the efficacy of utilizing adaptive MI-BCI modulation to trigger biomechanically precise assistance, establishing a foundational computational paradigm with significant potential for clinical stroke rehabilitation. Full article

Shoulder calcific tendinopathy is a common condition affecting adults and is has a higher incidence in women. This condition is due to a multifactorial process and is characterized by the deposition of hydroxyapatite crystals in the rotator cuff tendons. The disease shows a phenotypic transformation of tenocytes into chondrocyte-like cells, likely caused by metabolic and inflammatory changes and mechanical stress. Risk factors promoting this pathology include hyperlipidemia, advanced age, diabetes, female gender, and thyroid dysfunction. Recent studies highlight that metalloproteinases, oxidative stress, inflammatory mediators, bone morphogenetic proteins (BMPs), genetic and post-transcriptional alterations play a significant role in the pathogenesis of the disease. New therapeutic strategies are currently available that aim to modulate inflammation, osteogenic differentiation, and calcium homeostasis, showing promising results, especially in preclinical models. The aim of this review is to explore the different pathogenetic mechanisms and highlight future therapeutic developments for the treatment of shoulder calcification. Full article

Background: Well-known risk factors for soft tissue heterotopic ossification (HO) include aging and mechanical stress, which may be linked to oxidative stress and downstream nucleotide metabolites. Thus, we investigated the involvement of extracellular ATP (ex-ATP) and its metabolites in the oxidative stress-induced mineralization of TT-D6 cells and primary mouse tendon cells. Methods: An osteogenic culture with the intermittent addition of hydrogen peroxide was monitored for two weeks using metabolomic and gene expression analyses. Results: Calcium deposition was significantly enhanced by 0.3 mM hydrogen peroxide in the osteogenic media after 2 weeks, with minimal calcification in its absence. Similar results were observed in a medium transfer experiment using 3-day-old hydrogen peroxide-treated conditioned medium, which led to an increased expression of osterix and alkaline phosphatase. Metabolomic analysis revealed a gradual increase in ex-ATP and its metabolites, including ADP, AMP, and adenosine, in the medium. The metabolite increase was enhanced by hydrogen peroxide after 12 h. Moreover, exogenous adenosine (100 μM) increased mineralization in osteogenic media. Additionally, 1 μM dipyridamole, an inhibitor of equilibrative nucleoside transporter 1 (Ent1), also increased it in response to low-dose (0.1 mM) hydrogen peroxide. Conclusions: The enhanced osteogenic calcification of the tendon cell culture by hydrogen peroxide was associated with an increase in extracellular nucleotide metabolites, especially adenosine, with some evidence of causality. Full article