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The surgical target for optimal implant positioning in robotic-assisted total knee arthroplasty remains the subject of ongoing discussion. One of the proposed targets is to recreate the knee’s functional behaviour as per its pre-diseased state. The aim of this study was to optimize implant positioning, starting from mechanical alignment (MA), toward restoring the pre-diseased status, including ligament strain and kinematic patterns, in a patient population.

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This study aimed to demonstrate the promoting effect of elastic fixation on fracture, and further explore its mechanism at the gene and protein expression levels.

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To determine whether obesity and malnutrition have a synergistic effect on outcomes from skeletal trauma or elective orthopaedic surgery.

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Rotator cuff tear (RCT) is the leading cause of shoulder pain, primarily associated with age-related tendon degeneration. This study aimed to elucidate the potential differential gene expressions in tendons across different age groups, and to investigate their roles in tendon degeneration.

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Endoprosthetic reconstruction following distal femur tumour resection has been widely advocated. In this paper, we present the design of an uncemented endoprosthesis system featuring a short, curved stem, with the goal of enhancing long-term survivorship and functional outcomes.

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The primary objective of this study was to develop a validated classification system for assessing iatrogenic bone trauma and soft-tissue injury during total hip arthroplasty (THA). The secondary objective was to compare macroscopic bone trauma and soft-tissues injury in conventional THA (CO THA) versus robotic arm-assisted THA (RO THA) using this classification system.

The April 2024 Research Roundup³⁶⁰ looks at: Prevalence and characteristics of benign cartilaginous tumours of the shoulder joint; Is total-body MRI useful as a screening tool to rule out malignant progression in patients with multiple osteochondromas?; Effects of vancomycin and tobramycin on compressive and tensile strengths of antibiotic bone cement: a biomechanical study; Biomarkers for early detection of Charcot arthropathy; Strong association between growth hormone therapy and proximal tibial physeal avulsion fractures in children and adolescents; UK pregnancy in orthopaedics (UK-POP): a cross-sectional study of UK female trauma and orthopaedic surgeons and their experiences of pregnancy; Does preoperative weight loss change the risk of adverse outcomes in total knee arthroplasty by initial BMI classification?.

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Despite limited clinical scientific backing, an additional trochanteric stabilizing plate (TSP) has been advocated when treating unstable trochanteric fractures with a sliding hip screw (SHS). We aimed to explore whether the TSP would result in less post operative fracture motion, compared to SHS alone.

The anterior cruciate ligament (ACL) is the connective tissue located at the end of long bones providing stability to the knee joint. After tear or rupture clinical reconstruction of the tissue remains a challenge due to the particular mechanical properties required for proper functioning of the tissue. The outstanding mechanical properties of the ACL are characterized by a viscoelastic behavior responsible of the dissipation of the loads that are transmitted to the bone. These mechanical properties are the result of a very specialized graded extracellular matrix that transitions smoothly between the heterotypic cells, stiffness and composition of the ACL and the adjacent bone. Thus, mimicking the zonal biochemical composition, cellular phenotype and organization are key to reset the proper functioning of the ACL. We have previously shown how the biochemical composition presented to cells in electrospun scaffolds results in haptokinesis, reverting contact-guidance effects. [1]. Here, we demonstrate that contact guidance can also be disrupted by structural parameters in aligned wavy scaffolds. The presentation of a wavy fiber arrangement affected the cell organization and the deposition of a specific ECM characteristic of fibrocartilage. Cells cultured in wavy scaffolds grew in aggregates, deposited an abundant ECM rich in fibronectin and collagen II, and expressed higher amounts of collagen II, X and tenomodulin as compared to aligned scaffolds. In-vivo implantation in rabbits of triphasic scaffolds accounting for aligned-wavy-aligned zones showed a high cellular infiltration and the formation of an oriented ECM, as compared to traditional aligned scaffolds. [2]

Tendinopathy is the most common form of chronic tendon disorders, accounting for up 30% of all musculoskeletal clinic visits [1]. In tendon disease, the largely avascular tendon tissue often becomes hypervascularized and fibrotic [2]. As blood vessel growth and angiogenic signaling molecules are often induced by the lack of adequate nutrients and oxygen, hypoxic signaling is speculated to be a root cause of tendon neovascularization and tendinopathy [3,4,5]. However, how the vascular switch is initiated in tendons, and how vascularization contributes to tendon pathology remains unknown. In this talk, we provide evidence that HIF-1α is implicated in tendon disease and HIF-1α stabilization in human tendon cells induces vascular recruitment of endothelial cells via VEGFa secretion. More interesting, HIF-1α stabilization in tendon cells in vivo, seems to recapitulate all main features of fibrotic human tendon disease, including vascular ingrowth, matrix disorganization, changes in tissue mechanics, cell proliferation and innervation. Surprisingly, in vivo knock-out of VEGFa rescued angiogenesis in the tendon core but it did not affect tendon mechanical properties and tissue pathophysiological changes, suggesting that blood vessels ingrowth might not be a primary cause but a consequence of HIF-1α activation

Tendons are characterised by an inferior healing capacity when compared to other tissues, ultimately resulting in the formation of a pathologically altered extracellular matrix structure. Although our understanding of the underlying causes for the development and progression of tendinopathies remains incomplete, mounting evidence indicates a coordinated interplay between tendon-resident cells and the ECM is critical. Our recent results demonstrate that the matricellular protein SPARC (Secreted protein acidic and rich in cysteine) is essential for regulating tendon tissue homeostasis and maturation by modulating the tissue mechanical properties and aiding in collagen fibrillogenesis [1,2]. Consequently, we speculate that SPARC may also be relevant for tendon healing. In a rat patellar tendon window defect model, we investigated whether the administration of recombinant SPARC protein can modulate tendon healing. Besides the increased mRNA expression of collagen type 1 and the downregulation of collagen type 3, a robust increase in the expression of pro-regenerative fibroblast markers in the repair tissue after a single treatment with rSPARC protein was observed. Additionally, pro-fibrotic markers were significantly decreased by the administration of rSPARC. Determination of structural characteristics was also assessed, indicating that the ECM structure can be improved by the application of rSPARC protein. Therefore, we believe that SPARC plays an important role for tendon healing and the application of recombinant SPARC to tendon defects has great potential to improve functional tendon repair

Articular cartilage is a multi-zonal tissue that coats the epiphysis of long bones and avoids its wear during motion. An unusual friction could micro-fracture this connective membrane and progress into an osteochondral defect (OD), where the affected cartilage suffers inflammation, fibrillation, and forfeiture of its anisotropic structure. Clinical treatment for ODs has been focused on micro-fracture techniques, where the defect area is removed and small incisions are performed in the subchondral bone, which allows the exudation of mesenchymal stem cells (hMSCs) to the abraded zone. However, hMSCs represent less than 0.01% of the total cell population and are not able to self-organise coherently, so the treatments fail in the long term. To select, support and steer hMSCs from the bone marrow into a specific differentiation stage, and recreate the cartilage anisotropic microenvironment, multilayer dual-porosity 3D-printed scaffolds were developed. Dual-porosity scaffolds were printed using prepared inks, containing specific ratios of poly-(d,l)lactide-co-caprolactone copolymer and gelatine microspheres of different diameters, which acted as sacrificial micro-pore templates and were leached after printing. The cell adhesion capability was investigated showing an increased cell number in dual-porosity scaffolds as compared to non-porous ones. To mimic the stiffness of the three cartilage zones, several patterns were designed, printed, and checked by dynamic-mechanical analysis under compression at 37 ºC. Three patterns with specific formulations were chosen as candidates to recreate the mechanical properties of the cartilage layers. Differentiation studies in the selected scaffolds showed the formation of mature cartilage by gene expression, protein deposition and biomolecular analysis. Given the obtained results, designed scaffolds were able to guide hMSC behaviour. In conclusion, biocompatible, multilayer and dual-porosity scaffolds with cell entrapment capability were manufactured. These anisotropic scaffolds were able to recreate the physical microenvironment of the natural cartilage, which in turn stimulated cell differentiation and the formation of mature cartilage. Acknowledgments: This work was supported by the EMAKIKER grant

Developments in the field of additive manufacturing have allowed significant improvements in the design and production of scaffolds with biologically relevant features to treat bone defects. Unfortunately, the workflow to generate personalized scaffolds is source of inaccuracies leading to a poor fit between the implant and patients' bone defects. In addition, scaffolds are often brittle and fragile, uneasing their handling by surgeons, with significant risks of fracture during their insertion in the defect. Consequently, we developed organo-mineral cementitious scaffolds displaying evolutive mechanical properties which are currently being evaluated to treat maxillofacial bone deformities in veterinary clinics. Treatment of dog patients was approved by ethic and welfare committees (CERVO-2022-14-V). To date, 8 puppies with cleft palate/lip deformities received the following treatment. Two weeks prior surgery, CT-scan of patient's skull was performed to allow for surgical planning and scaffold designing. Organo-mineral printable pastes were formulated by mixing an inorganic cement precursor (α-Ca3(PO4)2) to a self-reticulating hydrogel (silanized hyaluronic acid) supplemented with a viscosifier (hydroxymethylpropylcellulose). Scaffolds were produced by robocasting of these pastes. Surgical interventions included the reconstruction of soft tissues, and the insertion of the scaffold soaked with autologous bone marrow. Bone formation was monitored 3 and 6 months after reconstruction, and a biopsy at 6 months was performed for more detailed analyses. Scaffolds displayed great handling properties and were inserted within bone defects without significant issue with a relevant bone edges/scaffold contact. Osteointegration of the scaffolds was observed after 3 months, and regeneration of the defect at 6 months seemed quite promising. Preliminary results have demonstrated a potential of the set-up strategy to treat cleft lip/palate deformities in real, spontaneous clinical setting. Translation of these innovative scaffolds to orthopedics is planned for a near future

Achilles tendon mechanical properties depend on a complex hierarchical design, with collagen being the smallest load-bearing unit. At the nanoscale, collagen molecules are organized into fibrils, which at the microscale are assembled into fibers, followed by larger structures such as sub-tendons or fascicles. Degree of in vivo loading affects the collagen content, and organization and consequently the tissue's mechanical response. We aim to unravel how composition, structural organization, and mechanical response are affected by degree of in vivo loading at each length scale. The presentation will outline the results to date about to the use of high-resolution synchrotron-based tissue characterisation methods on several length scales in combination with in situ mechanical tests. We use a rat model, where the tendons are subjected to varying loading in vivo. To characterize the tissue microstructure, phase-contrast enhanced synchrotron micro-tomography is performed. The 3D fiber organization in fully loaded tendons is highly aligned, whereas the fibers in unloaded tendons are significantly more heterogeneously arranged and crimped. To characterize the collagen fibril response, Small Angle X-ray Scattering is performed. Two types of fibril organizations are found; a single population oriented towards the main load direction and two fibril subpopulations with clearly distinct orientations. Scattering during loading showed that the fibrils in unloaded tendons did not strain as much in fully loaded. In situ loading concurrently with high resolution synchrotron experiments show the complex tendon response to in situ load and its relation to in vivo loading and tendon hierarchical structure. Unloading seems to alter the organization of the fibrils and fibers, e.g. increased crimping and more pronounced sub-tendon twists. Acknowledgements: Funding from Knut and Alice Wallenberg Foundation and European Research Council (101002516). Paul Scherrer Institut, Switzerland for beamtime at cSAXS and TOMCAT

The aim of this study is to print 3D polycaprolactone (PCL) scaffolds at high and low temperature (HT/LT) combined with salt leaching to induced porosity/larger pore size and improve material degradation without compromising cellular activity of printed scaffolds. PCL solutions with sodium chloride (NaCl) particles either directly printed in LT or were casted, dried, and printed in HT followed by washing in deionized water (DI) to leach out the salt. Micro-Computed tomography (Micro-CT) and scanning electron microscope (SEM) were performed for morphological analysis. The effect of the porosity on the mechanical properties and degradation was evaluated by a tensile test and etching with NaOH, respectively. To evaluate cellular responses, human bone marrow-derived mesenchymal stem/stromal cells (hBMSCs) were cultured on the scaffolds and their viability, attachment, morphology, proliferation, and osteogenic differentiation were assessed. Micro-CT and SEM analysis showed that porosity induced by the salt leaching increased with increasing the salt content in HT, however no change was observed in LT. Structure thickness reduced with elevating NaCl content. Mass loss of scaffolds dramatically increased with elevated porosity in HT. Dog bone-shaped specimens with induced porosity exhibited higher ductility and toughness but less strength and stiffness under the tension in HT whereas they showed decrease in all mechanical properties in LT. All scaffolds showed excellent cytocompatibility. Cells were able to attach on the surface of the scaffolds and grow up to 14 days. Microscopy images of the seeded scaffolds showed substantial increase in the formation of extracellular matrix (ECM) network and elongation of the cells. The study demonstrated the ability of combining 3D printing and particulate leaching together to fabricate porous PCL scaffolds. The scaffolds were successfully printed with various salt content without negatively affecting cell responses. Printing porous thermoplastic polymer could be of great importance for temporary biocompatible implants in bone tissue engineering applications

Several synthetic polymers have been widely investigated for their use in bone tissue engineering applications, but the ideal material is yet to be engineered. Triazine-trione (TATO) based materials and their derivatives are novel in the field of biomedical engineering but have started to draw interest. Different designs of the TATO monomers and introduction of different chemical linkages and end-groups widens the scope of the materials due to a range of mechanical properties. The aim of our work is to investigate novel TATO based materials, with or without hydroxyapatite filler, for their potential in bone tissue engineering constructs. Initially the biocompatibility of the materials was tested, indirectly and directly, according to ISO standards. Following this the osteoconductive properties were investigated with primary osteoblasts and an osteoblastic cell line. Bone marrow derived mesenchymal stem cells were used to evaluate the osteogenic differentiation and consequently the materials potential in bone tissue engineering applications

Decreasing the bulk weight without losing the biomechanical properties of commercial pure titanium (Cp-Ti) medical implants is now possible by using Laser Powder Bed Fusion (L-PBF) technology. Gyroid lattice structures that have precious mechanical and biological advantages because of similarity to trabecular bone. The aim of the study was to design and develop L-PBF process parameter optimization for manufacturing gyroid lattice Cp-Ti structures. The cleaning process was then optimized to remove the non-melted powder from the gyroid surface without mechanical loss. Gyroid cubic designs were created with various relative densities by nTopology. L-PBF process parameter optimization was progressed using with Cp-Ti (EOS TiCP Grade2) powder in the EOS M290 machine to achieve parts that have almost full dense and dimensional accuracy. The metallography method was made for density. Dimensional accuracy at gyroid wall thicknesses was investigated between designed and manufactured via stereomicroscope, also mechanical tests were applied with real time experiment and numerical analysis (ANSYS). Mass loss and strut thickness loss were investigated for chemical etching cleaning process. Gyroid parts had 99,5% density. High dimensional accuracy was achieved during L-PBF process parameters optimization. Final L-PBF parameters gave the highest 19% elongation and 427 MPa yield strength values at tensile test. Mechanical properties of gyroid were controlled with changing relative density. A minute chemical etching provided to remove non-melted powders. Compression test results of gyroids at numerical and real-time analysis gave unrelated while deformation behaviors were compatible with each other. Gyroid Cp-Ti osteosynthesis mini plates will be produced with final L-PBF process parameters. MTT cytotoxicity test will be characterized for cell viability. Acknowledgements This project is granted by TUBITAK (120N943). Feza Korkusuz MD is a member of the Turkish Academy of Sciences (TÜBA)

Biomaterials with mechanical or biological competence are ubiquitous in musculoskeletal disorders, and understanding the inflammatory response they trigger is key to guide tissue regeneration. While macrophage role has been widely investigated, immune response is regulated by other immune cells, including neutrophils, the most abundant leukocyte in human blood. As first responders to injury, infection or material implantation, neutrophils recruit other immune cells, and therefore influence the onset and resolution of chronic inflammation, and macrophage polarization. This response depends on the physical and chemical properties of the biomaterials, among other factors. In this study we report an in vitro culture model to describe the most important neutrophil functions in relation to tissue repair. We identified neutrophil survival and death, neutrophils extracellular trap formation, release of reactive oxygen species and degranulation with cytokines release as key functions and introduced a corresponding array of assays. These tests were suitable to identify clear differences in the response by neutrophils that were cultured on material of different origin, stiffness and chemical composition. Overall, substrates from biopolymers of natural origin resulted in increased survival, less neutrophil extracellular trap formation, and more reactive oxygen species production than synthetic polymers. Within the range of mechanical properties explored (storage modulus below 5 k Pa), storage modulus of covalently crosslinked hyaluronic acid hydrogels did not significantly alter neutrophils response, whereas polyvinyl alcohol gels of matching mechanical properties displayed a response indicating increased activation. Additionally, we present the effect of material stiffness, charge, coating and culture conditions in the measured neutrophils response. Further studies are needed to correlate the neutrophil response to tissue healing. By deciphering how neutrophils initiate and modulate the immune response to material implantation, we aim at introducing new principles to design immunomodulatory biomaterials for musculoskeletal disorders. Acknowledgments. This work was supported by the AO Foundation, AO CMF, grant AOCMF-21-04S

According to the latest report from the German Arthroplasty Registry, aseptic loosening is the primary cause of implant failure following primary hip arthroplasty. Osteolysis of the proximal femur due to the stress-shielding of the bone by the implant causes loss of fixation of the proximal femoral stem, while the distal stem remains fixed. Removing a fixed stem is a challenging process. Current removal methods rely on manual tools such as chisels, burrs, osteotomes, drills and mills, which pose the risk of bone fracture and cortical perforation. Others such as ultrasound and laser, generate temperatures that could cause thermal injury to the surrounding tissues and bone. It is crucial to develop techniques that preserve the host bone, as its quality after implant removal affects the outcome of a revision surgery. A gentler removal method based on the transcutaneous heating of the implant by induction is proposed. By reaching the glass transition temperature (T. G. ) of the periprosthetic cement, the cement is expected to soften, enabling the implant to be gently pulled out. The in-vivo environment comprises body fluids and elevated temperatures, which deteriorate the inherent mechanical properties of bone cement, including its T. G. We aimed to investigate the effect of fluid absorption on the T. G. (ASTM E2716-09) and Vicat softening temperature (VST) (ISO 306) of Palacos R cement (Heraeus Medical GmbH) when dry and after storage in Ringer's solution for up to 8 weeks. Samples stored in Ringer's solution exhibited lower T. G. and VST than those stored in air. After 8 weeks, the T. G. decreased from 95.2°C to 81.5°C in the Ringer's group, while the VST decreased from 104.4°C to 91.9°C. These findings will be useful in the ultimate goal of this project which is to design an induction-based system for implant removal. Acknowledgements: Funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – SFB/TRR-298-SIIRI – Project-ID 426335750