This paper aims to review the State of the Art in metal self-expanding stents made from nitinol (NiTi), showing shape memory and superelastic behaviors, to identify the challenges and the opportunities for improving patient outcomes. A significant contribution of this paper is its extensive coverage of multidisciplinary aspects, including design, simulation, materials development, manufacturing, bio/hemocompatibility, biomechanics, biomimicry, patency, and testing methodologies. Additionally, the paper offers in-depth insights into the latest practices and emerging trends, with a special emphasis on the transformative potential of additive manufacturing techniques in the development of metal stents. By consolidating existing knowledge and highlighting areas for future innovation, this review provides a valuable roadmap for advancing nitinol stents.

This review paper is related to the biomechanics of additively manufactured (AM) metallic scaffolds, in particular titanium alloy Ti6Al4V scaffolds. This is because Ti6Al4V has been identified as an ideal candidate for AM metallic scaffolds. The factors that affect the scaffold technology are the design, the material used to build the scaffold, and the fabrication process. This review paper includes thus a discussion on the design of Ti6A4V scaffolds in relation to how their behavior is affected by their cell shapes and porosities. This is followed by a discussion on the post treatment and mechanical characterization including in-vitro and in-vivo biomechanical studies. A review and discussion are also presented on the ongoing efforts to develop predictive tools to derive the relationships between structure, processing, properties and performance of powder-bed additive manufacturing of metals. This is a challenge when developing process computational models because the problem involves multi-physics and is of multi-scale in nature. Advantages, limitations, and future trends in AM scaffolds are finally discussed. AM is considered at the forefront of Industry 4.0, the fourth industrial revolution. The market of scaffold technology will continue to boom because of the high demand for human tissue repair.

Knee–ankle–foot orthoses (KAFOs) are prescribed to improve abnormal ambulation caused by quadriceps weakness. There are three major types of KAFOs: passive KAFOs, semidynamic KAFOs, and dynamic KAFOs. Dynamic KAFOs are the only type that enables to control knee motions throughout the entire walking gait cycle. However, those available in the market are heavy, bulky, and have limited functionality. The UT dynamic KAFO is developed to allow knee flexion and assist knee extension over the gait cycle by using a superelastic nitinol actuator, which has the potential to reduce volume and weight and reproduce normal knee behavior. In order to match the normal knee stiffness profile, the dynamic actuator consists of two actuating parts that work in the stance and swing phases, respectively. Each actuating part combines a superelastic torsional rod and a torsional spring in parallel. Geometries of the two superelastic rods were determined by matlab-based numerical simulations. The simulation response of the dynamic actuator was compared with the normal knee stiffness, verifying that the proposed design is able to mimic the normal knee performance. The surrounding parts of the dynamic knee joint have then been designed and modeled to house the two actuating parts. The dynamic knee joint was fabricated and mounted on a conventional passive KAFO, replacing its original knee joint on the lateral side. Motion analysis tests were conducted on a healthy subject to evaluate the feasibility of the UT dynamic KAFO. The results indicate that the UT dynamic KAFO allows knee flexion during the swing phase of gait and provides knee motion close to normal.

Background: Osteoarthritis of the acromioclavicular joint is one of the most common sources of shoulder pain. One of the current standard clinical physical examination tests is the cross body adduction test which has been shown to signal the presence of osteoarthritis. Another test referred to as the hand behind the back test has been described to provide a more accurate diagnosis than the CBA test for some patients. Through this work, both the CBA and the HBB tests were modeled in order to determine if there is merit for the HBB test to be used as a diagnostic tool for clinicians. Methods: Both tests were modeled using the zygote solid 3D 50th percentile male human anatomy model and MSC-ADAMS Software to compile and run the simulations. Within MSC-ADAMS the bones were outfitted with joints. During simulation, the bones were moved from the anatomical position to the final position for each test and the corresponding minimum distances between the bones at the acromioclavicular joint were then determined. Results: It was found that the distance between the acromioclavicular joint articulating surfaces decreased by 0.3 mm from the anatomical position during the CBA test and by 1.65 mm from the anatomical position during the HBB. This shows that the minimum space decreased from the anatomical position by more than 5 folds during the HBB test than during the CBA test. Conclusions: These results indicate that the HBB test may be a better diagnostic test due to the greater stress and irritation it places upon the acromioclavicular joint.

Acromioclavicular joint osteoarthritis is prevalent in middle-aged and older people, causing shoulder pain and functional limitations. Despite its prevalence, there are inconsistencies in the physical diagnosis procedures practiced in clinical tests. A recent study introduced a novel hand-behind-the-back (HBB) test, a promising alternative to the traditional cross-body adduction (CBA) test. However, further study was suggested to validate the results obtained. So, this study predicted muscle forces for the cross-body adduction and hand-behind-the-back tests using OpenSim and the AnyBody Modeling System™. This work redefined the joint kinematics for the tests and performed an inverse dynamics analysis to solve the muscle redundancy problem using the generic upper extremity dynamic models available in OpenSim and AnyBody Modeling System™. The results revealed some agreements and significant discrepancies in most muscle force predictions between the OpenSim and AnyBody Modeling System^TM. Thus, this study underscores the necessity of integrating multiple modeling approaches and comprehensive validation, including experimental data, to enhance the accuracy and reliability of muscle force predictions in shoulder biomechanics during CBA and HBB tests.