Analysis of a Motocross Knee Brace: From the Real Model to the Numerical Finite Element Model via 3D Scanning and Reverse Engineering

Featured Application: This study outlines a novel procedure for the Finite Element Modelling and Analysis of motocross knee braces under race conditions. The aim is to quantitatively evaluate the effectiveness of such stabilisers in reducing the risk and consequences of musculoskeletal injuries, considering the current lack of industrial standards and dedicated scientific research works. Musculoskeletal injuries often occur when performing motocross; almost half of the overall ligamentous injuries (42%) are knee ligaments injuries. Lesions can be greatly reduced with knee braces. Commercial knee braces are expected to oppose and limit unwanted and potentially harmful movements such as hyperextension and excessive rotation of the knee joint. However, this aspect has not been fully investigated from a biomechanical point of view. This would require proper Finite Element Modelling (FEM) and Analysis (FEA). However, to perform FEA and evaluate the efficacy of the brace simulating sportive conditions, numerical models need to be built. It requires a dedicated setup and several preprocessing steps, for which no industrial standard or widely accepted better practise is available as of today. Firstly, the brace and the lower limb are scanned using a 3D scanner. The geometry is reconstructed using reverse engineering techniques. These allow us to obtain a smooth, reliable 3D model starting from the points cloud acquired during scanning. A lower limb model was created using a mixed approach, combining MRI data and 3D scanning. Finally, a simulation of the impact condition after a jump using the developed model was carried out

Mechanical Properties of Animal Tendons: A Review and Comparative Study for the Identification of the Most Suitable Human Tendon Surrogates

The mechanical response of a tendon to load is strictly related to its complex and highly organized hierarchical structure, which ranges from the nano-to macroscale. In a broader context, the mechanical properties of tendons during tensile tests are affected by several distinct factors, due in part to tendon nature (anatomical site, age, training, injury, etc.) but also depending on the experimental setup and settings. This work aimed to present a systematic review of the mechanical properties of tendons reported in the scientific literature by considering different anatomical regions in humans and several animal species (horse, cow, swine, sheep, rabbit, dog, rat, mouse, and foal). This study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method. The literature research was conducted via Google Scholar, PubMed, PicoPolito (Politecnico di Torino’s online catalogue), and Science Direct. Sixty studies were selected and analyzed. The structural and mechanical properties described in different animal species were reported and summarized in tables. Only the results from studies reporting the strain rate parameter were considered for the comparison with human tendons, as they were deemed more reliable. Our findings showed similarities between animal and human tendons that should be considered in biomechanical evaluation. An additional analysis of the effects of different strain rates showed the influence of this parameter

3d printing and testing of rose thorns or limpet teeth inspired anchor device for tendon tissue repair

Purposes: Advancements in medical technology have enabled medical specialists to resolve significant problems concerning tendon injuries. However, despite the latest improvements, surgical tendon repair remains challenging. This study aimed to explore the capabilities of the current state-of-the-art technologies for implantable devices. Methods: After performing extensive patent landscaping and literature review, an anchored tissue fixation device was deemed the most suitable candidate. This design was firstly investigated numerically, realizing a Finite Element Model of the device anchored to two swine tendons stumps, to simulate its application on a severed tendon. Two different hook designs, both bio-inspired, were tested while retaining the same device geometry and anchoring strategy. Then, the applicability of a 3D-printed prototype was tested on swine tendons. Finally, the device-tendon stumps ensemble was subjected to uniaxial tensile tests. Results: The results show that the investigated device enables a better load distribution during the immobilized limb period in comparison to standard suture-based approaches, yet it still presents several design flaws. Conclusions: The current implantable solutions do not ensure an optimal result in terms of strength recovery. This and other weak points of the currently available proposals will serve as a starting point for future works on bio-inspired implantable devices for tendon repair

Finite element analysis of the flexor digitorum profundus tendon during a passive rehabilitation protocol

The present study aims to create a patient-specific hand model to simulate the passive rehabilitation on the index finger, quantifying the flexor digitorum profundus (FDP) tendon excursion and the stress experienced during simulated flexion. The computational model used in this analysis was created from an unknown patient dataset available in the Embodi3d online library. The segmentation, three-dimensional reconstruction, and modeling of the structures involved were performed using Materialise Mimics and Rhino3D. The FDP tendon excursion and stress values present in the model were calculated in the ANSYS environment. Based on the finite-element simulation, the FDP tendon presents an excursion of 10.1 mm during passive postoperative flexion. The highest-stress values were observed between the pulleys-FDP tendon contact surfaces. In particular, the pulley A1 exhibited the maximum principal stress of the model with a 58.7 MPa. The pulley A3 showed the same stress distribution pattern that A1 Pulley, but with the lowest values. The FDP Tendon excursion obtained is consistent with the results reported in the literature, which vary from 8 to 11 mm. The stress values found in the model explain the importance of the pulley mechanism keeping the FDP tendon attached to the finger bone during the range of motion experienced. The silico model proposed may potentially be used in the assessment of new medical device proposals in the field of hand reconstructive surgery

Mechanical properties of animal ligaments: a review and comparative study for the identification of the most suitable human ligament surrogates

: The interest in the properties of animal soft tissues is often related to the desire to find an animal model to replace human counterparts due to the unsteady availability of human tissues for experimental purposes. Once the most appropriate animal model is identified, it is possible to carry out ex-vivo and in-vivo studies for the repair of ligamentous tissues and performance testing of replacement and support healing devices. This work aims to present a systematic review of the mechanical properties of ligaments reported in the scientific literature by considering different anatomical regions in humans and several animal species. This study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method. Moreover, considering the lack of a standard protocol for preconditioning of tissues, this aspect is also addressed. Ninety-six studies were selected for the systematic review and analysed. The mechanical properties of different animal species are reported and summarised in tables. Only results from studies reporting the strain rate parameter were considered for comparison with human ligaments, as they were deemed more reliable. Elastic modulus, ultimate tensile stress, and ultimate strain properties are graphically reported identifying the range of values for each animal species and to facilitate comparison between values reported in the scientific literature in animal and human ligaments. Useful similarities between the mechanical properties of swine, cow, and rat and human ligaments have been found

Effect of nanoscale curvature sign and bundle structure on supercritical H(2) and CH(4) adsorptivity of single wall carbon nanotube

The adsorptivities of supercritical CH(4) and H(2) of the external and internal tube walls of single wall carbon nanotube (SWCNT) were determined. The internal tube wall of the negative curvature showed the higher adsorptivities for supercritical CH(4) and H(2) than the external tube wall of the positive curvature due to their interaction potential difference. Fine SWCNT bundles were prepared by the capillary force-aided drying treatment using toluene or methanol in order to produce the interstitial pore spaces having the strongest interaction potential for CH(4) or H(2); the bundled SWCNT showed the highest adsorptivity for supercritical CH(4) and H(2). It was clearly shown that these nanostructures of SWCNTs are crucial for supercritical gas adsorptivity.ArticleADSORPTION-JOURNAL OF THE INTERNATIONAL ADSORPTION SOCIETY. 17(3):643-651 (2011)journal articl

Characterization of deposits formed on diesel injectors in field test and from thermal oxidative degradation of n-hexadecane in a laboratory reactor

Solid deposits from commercially available high-pressure diesel injectors (HPDI) were analyzed to study the solid deposition from diesel fuel during engine operation. The structural and chemical properties of injector deposits were compared to those formed from the thermal oxidative stressing of a diesel fuel range model compound, n-hexadecane at 160°C and 450 psi for 2.5 h in a flow reactor. Both deposits consist of polyaromatic compounds (PAH) with oxygen moieties. The similarities in structure and composition of the injector deposits and n-hexadecane deposits suggest that laboratory experiments can simulate thermal oxidative degradation of diesel in commercial injectors. The formation of PAH from n-hexadecane showed that aromatization of straight chain alkanes and polycondensation of aromatic rings was possible at temperatures as low as 160°C in the presence of oxygen. A mechanism for an oxygen-assisted aromatization of cylcoalkanes is proposed

Formation of Nanoclusters and Nanopillars in Nonequilibrium Surface Growth for Catalysis Applications: Growth by Diffusional Transport of Matter in Solution Synthesis

Growth of nanoclusters and nanopillars is considered in a model of surface deposition of building blocks (atoms) diffusionally transported from solution to the forming surface structure. Processes of surface restructuring are also accounted for in the model, which then yields morphologies of interest in catalysis applications. Kinetic Monte Carlo numerical approach is utilized to explore the emergence of FCC-symmetry surface features in Pt-type metal nanostructures. Available results exemplify evaluation of the fraction of the resulting active sites with desirable properties for catalysis, such as (111)-like coordination, as well as suggest optimal growth regimes

Where myth and archaeology meet: Discovering the Gorgon Medusa's Lair.

Here we report the discovery of ceramic fragments that form part of a Gorgoneion, a ceramic image representation of the Gorgon Medusa. The fragments were found in a deep part of Gorham's Cave, well known to ancient mariners as a natural shrine, between the 8th and 2nd century BCE. We discuss the context of this discovery, both within the inner topography of the cave itself, and also the broader geographical context. The discovery is situated at the extreme western end of the Mediterranean Sea, where it meets the Atlantic Ocean. The location was known to ancient mariners as the northern Pillar of Herakles, which marked the end of the known world. We relate the discovery, and its geographical and chronological context, to Greek legends that situated the lair of the Gorgon sisters at a location which coincides with the physical attributes and geographical position of Gorham's Cave. We thus provide, uniquely, a geographical and archaeological context to the myth of Perseus and the slaying of the Gorgon Medusa