TY - JOUR A1 - Wiesent, Lisa A1 - Spear, Ashley A1 - Nonn, Aida T1 - Computational analysis of the effects of geometric irregularities on the interaction of an additively manufactured 316L stainless steel stent and a coronary artery JF - Journal of the Mechanical Behavior of Biomedical Materials N2 - Customized additively manufactured (laser powder bed fused (L-PBF)) stents could improve the treatment of complex lesions by enhancing stent-artery conformity. However, geometric irregularities inherent for L-PBF stents are expected to influence not only their mechanical behavior but also their interaction with the artery. In this study, the influence of geometrical irregularities on stent-artery interaction is evaluated within a numerical framework. Thus, computed arterial stresses induced by a reconstructed L-PBF stent model are compared to those induced by the intended stent model (also representing a stent geometry obtained from conventional manufacturing processes) and a modified CAD stent model that accounts for the increased strut thickness inherent for L-PBF stents. It was found that, similar to conventionally manufactured stents, arterial stresses are initially related to the basic stent design/topology, with the highest stresses occurring at the indentations of the stent struts. Compared to the stent CAD model, the L-PBF stent induces distinctly higher and more maximum volume stresses within the plaque and the arterial wall. In return, the modified CAD model overestimates the arterial stresses induced by the L-PBF stent due to its homogeneously increased strut thickness and thus its homogeneously increased geometric stiffness compared with the L-PBF stent. Therefore, the L-PBF-induced geometric irregularities must be explicitly considered when evaluating the L-PBF stent-induced stresses because the intended stent CAD model underestimates the arterial stresses, whereas the modified CAD model overestimates them. The arterial stresses induced by the L-PBF stent were still within the range of values reported for conventional stents in literature, suggesting that the use of L-PBF stents is conceivable in principle. However, because geometric irregularities, such as protruding features from the stent surface, could potentially damage the artery or lead to premature stent failure, further improvement of L-PBF stents is essential. KW - Laser powder bed fusion (L-PBF) KW - Cardiovascular stents KW - Finite element analysis (FEA) KW - Geometrical imperfections KW - Stent-artery interaction Y1 - 2022 U6 - https://doi.org/10.1016/j.jmbbm.2021.104878 SN - 1751-6161 VL - 125 PB - Elsevier ER - TY - JOUR A1 - Wong, Christian A1 - Rasmussen, John A1 - Simonsen, Erik B. A1 - Hansen, Lone A1 - de Zee, Mark A1 - Dendorfer, Sebastian T1 - The Influence of Muscle Forces on the Stress Distribution in the Lumbar Spine JF - The Open Spine Journal N2 - Introduction: Previous studies of bone stresses in the human lumbar spine have relied on simplified models when modeling the spinal musculature, even though muscle forces are likely major contributors to the stresses in the vertebral bones. Detailed musculoskeletal spine models have recently become available and show good correlation with experimental findings. A combined inverse dynamics and finite element analysis study was conducted in the lumbar spine to investigate the effects of muscle forces on a detailed musculoskeletal finite element model of the 4th lumbar vertebral body. Materials and Methodology: The muscle forces were computed with a detailed and validated inverse dynamics musculoskeletal spine model in a lifting situation, and were then applied to an orthotropic finite element model of the 4th lumbar vertebra. The results were compared with those from a simplified load case without muscles. Results: In general the von Mises stress was larger by 30%, and even higher when looking at the von Mises stress distribution in the superio-anterior and central part of the vertebral body and in the pedicles. Conclusion: The application of spine muscles to a finite element model showed markedly larger von Mises stress responses in the central and anterior part of the vertebral body, which can be tolerated in the young and healthy spine, but it would increase the risk of compression fractures in the elderly, osteoporotic spine. KW - Lumbar spine KW - Muscle influence KW - Inverse dynamics KW - Finite element analysis KW - Lendenwirbelsäule KW - Muskelkraft KW - Belastung KW - Finite-Elemente-Methode Y1 - 2011 U6 - https://doi.org/10.2174/1876532701103010021 VL - 3 IS - 1 SP - 21 EP - 26 ER - TY - JOUR A1 - Zellner, Johannes A1 - Hierl, Katja A1 - Mueller, Michael A1 - Pfeifer, Christian A1 - Berner, Arne A1 - Dienstknecht, Thomas A1 - Krutsch, Werner A1 - Geis, Sebastian A1 - Gehmert, Sebastian A1 - Kujat, Richard A1 - Dendorfer, Sebastian A1 - Prantl, Lukas A1 - Nerlich, Michael A1 - Angele, Peter ED - Gilbert, Jeremy T1 - Stem cell-based tissue-engineering for treatment of meniscal tears in the avascular zone JF - Journal of Biomedical Materials Research Part B Applied Biomaterials N2 - Meniscal tears in the avascular zone have a poor self-healing potential, however partial meniscectomy predisposes the knee for early osteoarthritis. Tissue engineering with mesenchymal stem cells and a hyaluronan collagen based scaffold is a promising approach to repair meniscal tears in the avascular zone. 4 mm longitudinal meniscal tears in the avascular zone of lateral menisci of New Zealand White Rabbits were performed. The defect was left empty, sutured with a 5-0 suture or filled with a hyaluronan/collagen composite matrix without cells, with platelet rich plasma or with autologous mesenchymal stem cells. Matrices with stem cells were in part precultured in chondrogenic medium for 14 days prior to the implantation. Menisci were harvested at 6 and 12 weeks. The developed repair tissue was analyzed macroscopically, histologically and biomechanically. Untreated defects, defects treated with suture alone, with cell-free or with platelet rich plasma seeded implants showed a muted fibrous healing response. The implantation of stem cell-matrix constructs initiated fibrocartilage-like repair tissue, with better integration and biomechanical properties in the precultured stem cell-matrix group. A hyaluronan-collagen based composite scaffold seeded with mesenchymal stem cells is more effective in the repair avascular meniscal tear with stable meniscus-like tissue and to restore the native meniscus. KW - biomechanics KW - meniscus KW - scaffolds KW - stem cells KW - tissue engineering KW - Meniskusschaden KW - Tissue Engineering KW - Mesenchymzelle KW - Hyaluronsäure Y1 - 2013 U6 - https://doi.org/10.1002/jbm.b.32922 VL - 101 IS - 7 SP - 1133 EP - 1142 ER - TY - GEN ED - Hammer, Joachim ED - Nerlich, Michael ED - Dendorfer, Sebastian T1 - Medicine Meets Engineering: Proceedings of the 2nd Conference on Applied Biomechanics Regensburg N2 - Biomedical Engineering is defined as the science that integrates medical and engineering sciences to improve diagnosis and treatment of patients. Only by this integration progress can be achieved. Both medical and engineering sciences comprise a huge diversity in topics, so it is imaginable that Biomedical Engineering, combining these two science areas, is even more huge. Thanks to this megadisciplinary approach many breakthroughs can be achieved. More and more research groups realize this and start new research projects, which results in a rapid increase in knowledge in Biomedical Engineering. This will only benefit the main goal of Biomedical Engineering; improving diagnosis and treatment of patients when it is spread and applied. The 2nd Regensburg Applied Biomechanics conference is special in that it realized both the distribution of new knowledge and the essential integration of medical and engineering specialists. The conference dealt with the latest results in applied biomechanics, ranging from fundamental bone strength properties via bone remodeling phenomena to new implants that replace lost human functions. Also new research areas like robot surgery and tissue engineering were discussed. KW - Biomechanik Y1 - 2008 SN - 978-1586038281 PB - IOS Press, US ET - 1. Aufl. ER - TY - GEN ED - Frommeld, Debora ED - Scorna, Ulrike ED - Haug, Sonja ED - Weber, Karsten T1 - Gute Technik für ein gutes Leben im Alter? BT - Akzeptanz, Chancen und Herausforderungen altersgerechter Assistenzsysteme N2 - Längst gibt es altersgerechte digitale Assistenzsysteme. Doch sind Umfang und Geschwindigkeit ihrer Verbreitung sowohl in Pflegeeinrichtungen als auch in privaten Haushalten weitgehend unbekannt. Informationen zu tatsächlich eingesetzten Systemen, realisierten Umsätzen und Marktvolumen sind kaum zu finden. Obwohl es viele Vermutungen hinsichtlich der Hindernisse bei der Einführung altersgerechter Assistenzsysteme gibt, sind auch hier verlässliche Aussagen rar. Die Beiträge des Bandes liefern auf Basis empirischer Untersuchungen und theoretischer Überlegungen Antworten und zeigen auf, wie vielgestaltig die Faktoren sind, die die Diffusion altersgerechter Assistenzsysteme hemmen oder fördern. KW - Alter KW - Altenpflege KW - Assistenzsystem KW - Künstliche Intelligenz KW - Medizintechnik KW - Arbeitshilfe Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-149 SN - 978-3-8376-5469-1 PB - transcript Verlag CY - Bielefeld ER -