Osseointegrated Percutaneous Devices (OPDs) are designed to restore the function of a missing limb. They are implanted inside the medullary cavity of long bones with a pylon that penetrates the skin, which is attached to an external prosthetic device. Soft tissue down-growth and bacterial infection at the skin-implant interface are the two main complications associated with these implants and occur because of poor adhesion of keratinocytes and fibroblasts to the implant surface. A pocket forms between the implant surface and the skin, allowing bacterial colonisation and proliferation, leading to infection, and therefore a “smart” resurfacing of the pylon that improves cell adhesion has the potential to reduce soft tissue down-growth and bacterial infection. It has been shown that TiO2 nanotubes can improve cell attachment. Therefore, this study aimed to compare the effect of three different nanotube diameters with smooth titanium surfaces on cell viability, attachment and morphology of human keratinocytes and fibroblasts. We hypothesised that TiO2 nanotubes would improve cell adhesion and viability compared to smooth titanium surfaces. The number of vinculin markers was significantly higher for fibroblasts attached to 80 nm and 110 nm diameter nanotube diameters. Gene expression of vinculin and collagen XVII was higher for cells on all nanotubes compared with polished titanium surfaces. The morphology of cells on the nanotubes was also different from that observed on control surfaces: for both keratinocytes and fibroblasts, the number and length of filopodia were greater for cells on nanotube surfaces.The results supported our hypothesis: large-diameter nanotubes promoted significantly greater cell viability and expression of adhesion-associated proteins compared with smooth titanium control surfaces.

Dental implants have become common for restoring function and aesthetics after edentulism, with titanium (Ti) remaining the most widely used material due to its excellent mechanical properties and biocompatibility. Despite their clinical success, long-term performance is strongly influenced by surface characteristics, which regulate osseointegration and susceptibility to bacterial colonisation. Consequently, surface modification approaches have become critical strategies to enhance implant stability, bioactivity and longevity. This review critically evaluates conventional, advanced, and hybrid surface modification strategies. Subtractive methods, such as sandblasting and acid etching, increase microroughness (Ra 1.5–3 μm), enhancing osteoblast attachment and differentiation, but may promote bacterial adhesion and surface contamination. Combined treatments like SLA and SLActive generate hierarchical micro–nano topographies, improving protein adsorption, early-stage osteoblast proliferation (up to 2-fold), and clinical stability. Laser ablation and photofunctionalisation further modulate surface chemistry and wettability, accelerating osseointegration and epithelial cell adhesion. Coating approaches, including layer-by-layer self-assembly, nanospray drying, plasma spraying, and piezoelectric nanocomposites, introduce antimicrobial activity (>95% reduction in Escherichia coli or Staphylococcus aureus) and enhanced osteogenic differentiation with mechanical stability, with adhesion values reaching 49 MPa. Hybrid techniques such as sol–gel, hydrothermal, and anodisation provide controlled topography, chemical composition, and bioactivity, promoting early bone-to-implant contact (BIC increase of 10%–25%) in preclinical models. Notwithstanding promising in vitro and in vivo outcomes, variability in processing parameters and limited standardisation restrict large-scale clinical translation. Overall, contemporary Ti surface engineering emphasises a synergistic balance of topography, chemistry, wettability, and hierarchical structuring to optimise biological performance for dental implant applications.

Resorbable magnesium (Mg) alloys are attractive for orthopaedic and cardiovascular implants but can degrade rapidly in physiological electrolytes, and combined corrosion-mechanical loading may trigger premature failure. Electrochemical oxidation (ECO) coatings can reduce corrosion by forming a ceramic-like surface enriched with fluoride and phosphate species, yet their brittleness raises concerns regarding integrity under concurrent corrosion and loading. Here, we investigate how ECO coating thickness influences corrosion behaviour and mechanical response under physiologically relevant conditions. AZ31 and X0 alloys were coated with 5 & micro;m and 15 & micro;m ECO layers and tested under static and cyclic three-point bending (3PB) in Hank's balanced salt solution (HBSS). 3PB fatigue tests revealed that cracks in the alloy initiate at the tensile surface and are associated with coating defects such as pits and cracks in the coating, or localised Ca-P deposits. Under non-corroded conditions and after 1-week of corrosion, uncoated alloy rods demonstrated slightly higher fatigue resistance and delayed crack initiation compared to coated counterparts. After 3 weeks of immersion, only the coated rods retained loadbearing capacity, with the 15 & micro;m coating showing the longest fatigue life. Under static sustained loading, all coatings reduced crack initiation under elastic stress, whereas the 15 & micro;m coating suppressed through-thickness crack propagation under plastic loading and thereby prevented catastrophic stress corrosion cracking (SCC)style failure over the test duration. Overall, ECO coatings do not universally eliminate corrosion-mechanical interactions; rather, their protective efficacy is strongly condition-dependent and increases for the thicker coating under the environment-load combination examined.

Enthesis calcified fibrocartilage (CFC) is a specialized structure anchoring tendon or ligament to bone and transmitting stresses from joint motion or muscle forces. Understanding the CFC 3D microstructure–mechanics relationship is key to explaining its mechanical behaviour, failure, and regeneration after injury. Such insights can guide biomaterial design and regenerative therapies. However, current methods cannot non-invasively measure localized mechanical behaviour within this anisotropic, heterogeneous insertion. In this research, full-field micromechanical structural analysis of a murine enthesis (n = 3) was conducted to understand the mechanics underlying its structural attributes using high-resolution in-situ micro-computed tomography with deep learning reconstruction and digital volume correlation. Our findings reveal that, depending on stress angle, the central region of the CFC lacunar morphology deforms more than other regions. We also identified that CFC microstructure organization and thickness strongly correlate with strain distribution at the interface, with regions of higher lacunar density experiencing greater deformation. Calcified fibrocartilage is a key component of the enthesis in mammals, where tendons interface with bone. Here, in-situ micro-computed tomography reveals morphology and strain distribution in the Achilles enthesis of a mouse.

Transmission of strain across the tendon-bone interface otherwise known as the enthesis, is crucial to the movement of the skeleton. Imaging the inner structure and understanding the way that strain is transmitted across this interface is crucial to understanding the way it responds to load, how it becomes injured through trauma and how intervention and materials can be used to repair the enthesis after injury. Micro-CT imaging and digital volume correlation (DVC) have been widely used for musculoskeletal biomechanics analysis. However, there are limitations for soft tissue visualization. Contrast agents (CA) are used to address this, but understanding their potential effects is essential to ensure accurate and reliable characterization of musculoskeletal tissues biomechanics. In this research, four different contrast-enhanced staining solutions (CESS) including Iodine (I2) in Dulbecco’s modified eagle medium (DMEM), Phosphotungstic acid (PTA) in deionized water, PTA in ethanol, and Mercury II Chloride (HgCl2) in deionized water were used to visualize the tendon-to-bone interface using a combination of high resolution in-situ micro-computed tomography (micro-CT) imaging. The imaging was combined with DVC, nanoindentation, and quantitative 3D structural analysis to evaluate the effects of the CESS on the mechanical properties of the enthesis. The findings revealed significant alterations in mechanical behaviour and structural features of soft-to-hard tissue interfaces treated by CESS. The findings suggest that I₂ in DMEM provides a better balance between visualization and mechanical analysis. However, none of the CESSs completely preserved both structural and mechanical integrity.

Anterior cruciate ligament (ACL) injuries are common and often require surgical reconstruction. Autografts remain the clinical standard for ACL reconstruction (ACLR) but are limited by donor site morbidity, inconsistent outcomes, and supply constraints. Here, we report the development of electrospun ligament (ES-Lig), a fully degradable, electrospun scaffold composed of poly(ε-caprolactone) (PCL) designed to mimic the extracellular matrix (ECM) of the native ACL. A scalable manufacturing process was established, incorporating electrospinning, filament stretching, alignment, and braiding. ES-Lig demonstrated controlled in vitro degradation over 12 months while retaining sufficient mechanical strength for early-stage healing. Mechanical characterisation revealed tensile properties and fixation stability comparable to autografts. In vitro biocompatibility was confirmed through cytotoxicity assays, patient-derived ACL explants, and direct cell growth onto the material. In an ovine ACLR model, ES-Lig enabled functional recovery, tissue infiltration throughout its length, and joint stability within 10 weeks post-implantation. Histological and imaging analyses confirmed graft-bone integration, vascularisation, and early ligamentisation. These findings establish ES-Lig as a promising, clinically translatable scaffold for next-generation ACL repair.

Mesenchymal stem cells (MSCs) can differentiate into chondrocytes provided with the appropriate environmental cues. In this study, we loaded human adipose-derived stem cells (hAdMSCs) into collagen/alginate hydrogels, which have been shown to induce chondrogenesis in ovine bone marrow stem cells without the use of any exogenous chondrogenic growth factors. We examined the influence of hydrogel stiffness (5.75 and 6.85 kPa) and cell seeding density (1, 2, 4, and 16 × 106 cells/mL) on the chondrogenic induction of hAdMSCs, without exogenous differentiation growth factors. Over time, the behaviour of the hAdMSCs in the scaffolds was investigated by analysing the amount of DNA; their morphology; their cell viability; the expression of chondrogenic genes (RT-qPCR); and the deposition of collagen I, collagen II, and aggrecan. The results showed that all scaffolds supported the acquisition of a rounded morphology and the formation of cell aggregates, which were larger with higher cell seeding densities. Furthermore, the cells were viable within the hydrogels throughout the experiment, indicating that high cell density did not have a detrimental effect on viability. All the conditions supported the upregulation of chondrogenic genes (SOX9, COL2A1, SOX5, and ACAN). By comparison, only the highest cell seeding density (16 × 106 cells/mL) promoted a superior extracellular matrix deposition composed of collagen II and aggrecan with limited production of collagen I. These molecules were deposited in the pericellular space. Furthermore, no histological difference was noted between the two stiffnesses.

Clinical evidence for externally delivered electrical/mechanical stimulation in bone healing is mixed: proponents describe large benefits, while others report no difference. This may be because inconsistent targeting, anatomical differences, and physical phenomena (e.g., attenuation, reflection) mean cells experience highly variable stimulation doses. This study aimed to overcome this by developing implants that stimulate directly at the bone-implant interface. A bioelectronic implant (Fig. 1a; Ø8×16 mm) was developed to provide controlled electromechanical stimulation at the bone-implant interface. These implants had a rough titanium fixation surface (Ra: 75 µm) akin to contemporary cementless arthroplasty devices, but had electronics and sensors sealed inside. Eight were inserted into surgical defects (Fig. 1b; Ø8 mm) in the femoral condyles of four skeletally mature ewes (License P16F4AA0A). Half were activated intraoperatively by a mobile phone app such that they delivered electromechanical stimulus postoperatively (active) and half were left off (passive), with a double-blind paired-limb study design. Samples were retrieved after six weeks. Bone growth was analysed using fluorochrome histomorphometry (day 7: oxytetracycline; 21: alizarin red; 42: calcein blue). Microcomputed tomography (µCT) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) assessed mineralisation. Histology (H&E) was analysed by two blinded reviewers. Temperature was measured daily with onboard sensing. Bone growth at the implant interface was 58% faster with stimulation between days 7–21 (Fig. 1c; 5.4±1.2 vs. 3.5±0.9 µm/day; p=0.001) and 47% faster between days 21–42 (Fig. 1c; 3.3±0.6 vs. 2.3±0.7 µm/day; p=0.005). Remodeling within three trabeculae of the interface increased by 14% between days 7–42 (p = 0.017); no differences were observed beyond this, confirming effects were localised. µCT revealed mineralised bone within 100 µm of all implants, which was consistently high for the active samples (Fig. 1e&g vs. 1f&i); SEM/EDX confirmed mineralisation (Ca:P ratio ~1.7). Histology (Fig. 1h vs. 1j) found moderate-to-strong osseointegration around all active implants, but only half the passive controls. Temperature sensing indicated a beneficial short-sharp inflammatory response for the active implants relative to controls (Fig. 1d; p<0.05). Controlled, locally-targeted electromechanical stimulation from a bioelectronic implant leads to osseointegration that is >50% faster and twice as reliable as contemporary clinical technology. This first-of-its-kind technological advance could lead to a more digital future for orthopaedics whereby implant fixation is controlled and sensed postoperatively. Acknowledgements: UKRI (EP/W524323/1, EP/X52556X/1, EP/R042721/1), Wellcome Trust (223797/Z/21/Z), Imperial (DT-prime, FILM). For any figures or tables, please contact the authors directly.

Strain patterns across the osteochondral unit play a key role in the early pathological changes that lead to osteoarthritis (OA). X-ray computed tomography and digital volume correlation compared residual strain distribution across the osteochondral unit during OA progression.Osteochondral plugs (& Oslash; = 4 mm) from Dunkin-Hartley guinea pig tibias aged 2, 4 and 24 months (n = 6; representing pre-OA, early-stage OA and late-stage OA) were stained with a 1:2 hafnium-substituted Wells-Dawson polyoxometalate. Residual strains (epsilon p1, epsilon p3 and gamma) were computed following unconfined compression. Applied loads corresponded to twice body weight (BW; L1; n = 3) or four times BW (L2; n = 3). OA severity was confirmed histologically.Under L1, peak strains were low in pre-OA (similar to 200,000 mu epsilon, epsilon p3; similar to 160,000 mu epsilon gamma) and distributed evenly throughout the cartilage, calcified cartilage (CC) and subchondral bone (SB). In early OA, strain was localised to the cartilage surface (where degradative changes were also observed) and intensified with disease progression (similar to 300,000 mu epsilon epsilon p3; similar to 200,000 mu epsilon gamma). Under L2, increased compressive and shear strain (peak epsilon p3 = 258,395 +/- 36,076 mu epsilon; peak gamma = 174,075 +/- 32,522 mu epsilon) were detected at the cartilage surface and in CC during pre-OA. Strain in the middle and deep zones increased as CC thickness increased. Microcracks in the SB in severe OA specimens were associated with high gamma and high epsilon p1.Changes in strain distribution are depth dependent and may be linked to the progressive thickening of CC during early OA development, which may even promote the disease.

Magnesium-based implants offer significant benefits for biomedical applications due to their excellent biocompatibility and ability to biodegrade in physiological environments. However, their rapid corrosion can compromise mechanical integrity and hinder clinical translation. This study investigates the corrosion resistance and mechanical integrity of novel soft-sparking electrochemical oxidation (ECO) coatings on AZ31 magnesium alloys, highlighting their potential for biomedical applications. Unlike conventional plasma electrolytic oxidation (PEO), the soft-sparking ECO process operates under milder conditions and avoids dielectric breakdown, producing more uniform, adherent coatings even on complex geometries. Coatings measuring 5, 10, and 15 mu m thick were made from five distinct electrolytes: phosphate (P), high phosphate (P(H)), phosphate-silicate (PS), phosphate-fluoride (PF), and phosphate-fluoride-silicate (PFS). These were evaluated regarding porosity, roughness, adherence, and corrosion performance in a 5 M NaCl solution. The most promising coating (PF) was selected for further electrochemical and mechanical analysis, including screw insertion, four-point bending, and scratch testing. Our findings reveal that the coatings reduce corrosion rates by up to 35 times compared to the uncoated alloy while maintaining excellent adhesion even under plastic deformation. Notably, this work presents the first systematic study integrating mechanical integrity assessments with corrosion analysis of soft-sparking ECO coatings on complex magnesium geometries, offering a novel surface modification approach for nextgeneration biodegradable Mg-based implants.

Enthesis calcified fibrocartilage (CFC) is a highly specialized structure that has an important role in anchoring the tendon or ligament to the bone and transmitting mechanical stresses associated with either joint motion or with muscle forces. The CFC 3D microstructure–mechanics relationship is invaluable for understanding the enthesis structure that impacts the mechanical behavior and how this is related to the failure and regeneration of the enthesis after injury. This can provide valuable information for developing biomaterials and for regenerative therapies. However, current approaches are unable to attain a non-invasive measurement of the localized mechanical behavior within this anisotropic and heterogenous insertion. In this research, full-field micromechanical structural analysis of the enthesis was investigated to understand the fundamental mechanics underlying its structural attributes using high-resolution in-situ micro-computed tomography combined with deep learning reconstruction and digital volume correlation. Our findings reveal that depending on the angle of the applied stress, the central region of the CFC lacunar morphology deforms more than other regions. Furthermore, we identified that the CFC microstructure organization and thickness have a strong positive correlation with the strain distribution at the interface. Regions with higher lacunar density were found to experience greater deformation, suggesting that the local microstructure plays a crucial role in modulating the mechanical response of the CFC. This study highlights the correlation between the structure and mechanical response of CFC at the microscopic level showing the anisotropic strain behavior in different regions of the enthesis calcified fibrocartilage.

The muscle-tendon junction (MTJ) is a specialized interface that facilitates the transmission of force from the muscle to the tendon which has been implicated in muscle strains and tears. Understanding the transmission of forces and the strain generated in the MTJ is therefore important. For the first time, we report the 3D full-field strain distribution across the muscle-tendon junction (MTJ) using in-situ tensile testing and confocal microscopy coupled with digital volume correlation (DVC). This approach allowed us to measure the mechanical behaviour of the MTJ at the fibre/fascicle level. Acridine orange (AO) in 70% ethanol was used to enhance the contrast of the mouse Achilles-gastrocnemius MTJ, and the specimens were rehydrated prior to the tensile testing, which was performed using custom made tensile rig that fitted under the confocal microscopy. The 3D full-field strain distribution was obtained using DVC, where the strain changes were measured from confocal images taken with the MTJ under preload (0.4 N) and loaded (0.8 N and 1.2 N) representing 2.7- and 4-times body weight. High strain concentration was observed at the junction for both 0.8 N and 1.2 N loads. At the junction, the first principal stain (εp1), shear strain (γ) and von Mises strain (εVM) reached 15.2, 34.2 and 19.2% respectively. This study allowed us to measure fascicle level strain distribution at the MTJ. Using histology, microtears at the MTJ were seen in specimens loaded with 1.2 N which were associated with von Mises strain concentration in the adjacent region. The microtears occurred in regions where the strain level was between 8 and 15%. This study developed a methodology to determine high-resolution strain distribution at the MTJ and has the potential to be used to analyse the strain at the cellular level using higher magnification objectives.

The muscle tendon junction (MTJ) plays a crucial role in transmitting the force generated by muscles to the tendon and then to the bone. Injuries such as tears and strains frequently happen at the MTJ, where the regenerative process is limited due to poor vascularization and the complex structure of the tissue. Current solutions for a complete tear at the MTJ have not been successful and therefore, the development of a tissueengineered MTJ may provide a more effective treatment. In this study, decellularised extracellular matrix (DECM) derived from sheep MTJ was used to provide a scaffold for the MTJ with the relevant mechanical properties and differentiation cues such as the relase of growth factors. Human mesenchymal stem cells (MSCs) were seeded on DECM and 10 % cyclic strain was applied using a bioreactor. MSCs cultured on DECM showed significantly higher gene and protein expression of MTJ markers such as collagen 22, paxillin and talin, than MSCs in 2D culture. Although collagen 22 protein expression was higher in the cells with strain than without strain, reduced gene expression of other MTJ markers was observed when the strain was applied. DECM combined with 10 % strain enhanced myogenic differentiation, while tenogenic differentiation was reduced when compared to static cultures of MSCs on DECM. For the first time, these results showed that DECM derived from the MTJ can induce MTJ marker gene and protein expression by MSCs, however, the effect of strain on the MTJ development in DECM culture needs further investigation.

ABSTRACT Introduction Percutaneous Osseointegrated Implants (POIs) influence the load transfer path to the host bone. In turn, mechano-regulatory processes (strain adaptive bone remodeling) drive periprosthetic bone changes that influence implant stability and fixation outcome. These bone changes have not yet been reported for the Intraosseous Transcutaneous Amputation Prosthesis (ITAP) clinical trial. Objectives This study will first standardize the zoning and reporting of periprosthetic bone change in POI radiographs. Second, it will retrospectively measure periprosthetic bone change from radiographs of 12 participants with an ITAP up to 11 years. Finally, the results will be qualitatively compared with those from participants with different POI designs. Materials and Methods Twenty participants with unilateral transfemoral amputations received an ITAP in a 2-center UK clinical trial in either 2008/09 or 2013/14. Participant radiographs from one center were available (n = 12) over 11 years and have been collated and processed in a repeatable way. Transverse plane periprosthetic bone change measurements at 3 equidistant points along the implant stem were measured in AP and ML. Results Total median bone growth in AP was double that in ML (57.6 mm and 31.12 mm, respectively). Median lateral and posterior bone change (1.44 mm and 1.09 mm) was greater than median medial and anterior (0.83 mm and −0.005 mm) bone changes, respectively. The greatest change in radial bone growth was observed distally and the least proximally. Conclusions Bone changes were similar to other collared pressfit POIs in the literature. We demonstrate the influence of stem design and mechano-regulatory remodeling in stable fixation; however, additional influences on periprosthetic bone change were inferred from the results and further investigations are necessary. Clinical Relevance To identify ITAP design features and fixations that minimize endosteal resorption, thus promoting implant stability and contributing to clinical guidelines for rehabilitation and future design and fixation choices.

Focal cartilage defects are a prevalent knee problem affecting people of all ages. Articular cartilage (AC) possesses limited healing potential, and osteochondral defects can lead to pain and long-term complications such as osteoarthritis. Autologous chondrocyte implantation (ACI) has been a successful surgical approach for repairing osteochondral defects over the past two decades. However, a major drawback of ACI is the dedifferentiation of chondrocytes during their in vitro expansion. In this study, we isolated ovine chondrocytes and cultured them in a two-dimensional environment for ACI procedures. We hypothesized that 3D scaffolds would support the cells' redifferentiation without the need for growth factors so we encapsulated them into soft collagen and alginate (col/alg) hydrogels. Chondrocytes embedded into the hydrogels were viable and proliferated. After 7 days, they regained their original rounded morphology (aspect ratio 1.08) and started to aggregate. Gene expression studies showed an upregulation of COL2A1, FOXO3A, FOXO1, ACAN, and COL6A1 (37, 1.13, 22, 1123, and 1.08-fold change expression, respectively) as early as day one. At 21 days, chondrocytes had extensively colonized the hydrogel, forming large cell clusters. They started to replace the degrading scaffold by depositing collagen II and aggrecan, but with limited collagen type I deposition. This approach allows us to overcome the limitations of current approaches such as the dedifferentiation occurring in 2D in vitro expansion and the necrotic formation in spheroids. Further studies are warranted to assess long-term ECM deposition and integration with native cartilage. Though limitations exist, this study suggests a promising avenue for cartilage repair with col/alg hydrogel scaffolds.

Large bone reconstruction following trauma poses significant challenges for reconstructive surgeons, leading to a healthcare burden for health systems, long-term pain for patients, and complex disorders such as infections that are difficult to resolve. The use of bone substitutes is suboptimal for substantial bone loss, as they induce localized atrophy and are generally weak, and unable to support load. A combination of strong polycaprolactone (PCL)-based scaffolds, with an average channel size of 330 µm, enriched with 20% w/w of hydroxyapatite (HA), β-tricalcium phosphate (TCP), or Bioglass 45S5 (Bioglass), has been developed and tested for bone regeneration in a critical-size ovine femoral condyle defect model. After 6 weeks, tissue ingrowth was analyzed using X-ray computed tomography (XCT), Backscattered Electron Microscopy (BSE), and histomorphometry. At this point, all materials promoted new bone formation. Histological analysis showed no statistical difference among the different biomaterials (p > 0.05), but PCL-Bioglass scaffolds enhanced bone formation in the center of the scaffold more than the other types of materials. These materials show potential to promote bone regeneration in critical-sized defects on load-bearing sites.

This study evaluated the use of silica/poly(tetrahydrofuran)/poly(ε-caprolactone) (SiO2/PTHF/PCL-diCOOH) 3D-printed scaffolds, with channel sizes of either 200 (SC-200) or 500 (SC-500) µm, as biomaterials to support the chondrogenesis of sheep bone marrow stem cells (oBMSC), under in vitro conditions. The objective was to validate the potential use of SiO2/PTHF/PCL-diCOOH for prospective in vivo ovine studies. The behaviour of oBMSC, with and without the use of exogenous growth factors, on SiO2/PTHF/PCL-diCOOH scaffolds was investigated by analysing cell attachment, viability, proliferation, morphology, expression of chondrogenic genes (RT-qPCR), deposition of aggrecan, collagen II, and collagen I (immunohistochemistry), and quantification of sulphated glycosaminoglycans (GAGs). The results showed that all the scaffolds supported cell attachment and proliferation with upregulation of chondrogenic markers and the deposition of a cartilage extracellular matrix (collagen II and aggrecan). Notably, SC-200 showed superior performance in terms of cartilage gene expression. These findings demonstrated that SiO2/PTHF/PCL-diCOOH with 200 µm pore size are optimal for promoting chondrogenic differentiation of oBMSC, even without the use of growth factors.

We report, for the first time, the full-field 3D strain distribution of the muscle-tendon junction (MTJ). Understanding the strain distribution at the junction is crucial for the treatment of injuries and to predict tear formation at this location. Three-dimensional full-field strain distribution of mouse MTJ was measured using X-ray computer tomography (XCT) combined with digital volume correlation (DVC) with the aim of understanding the mechanical behavior of the junction under tensile loading. The interface between the Achilles tendon and the gastrocnemius muscle was harvested from adult mice and stained using 1% phosphotungstic acid in 70% ethanol. In situ XCT combined with DVC was used to image and compute strain distribution at the MTJ under a tensile load (2.4 N). High strain measuring 120,000 µε, 160,000 µε, and 120,000 µε for the first principal stain (εp1), shear strain (γ), and von Mises strain (εVM), respectively, was measured at the MTJ and these values reduced into the body of the muscle or into the tendon. Strain is concentrated at the MTJ, which is at risk of being damaged in activities associated with excessive physical activity.