In computational biomechanics, two separate types of models have been used predominantly to enhance the understanding of the mechanisms of action of the lumbosacral spine (LSS): Finite element (FE) and musculoskeletal multibody (MB) models. To combine advantages of both models, hybrid FE-MB models are an increasingly used alternative. The aim of this paper is to develop, calibrate, and validate a novel passive hybrid FE-MB open-access simulation model of a ligamentous LSS using ArtiSynth. Based on anatomical data from the Male Visible Human Project, the LSS model is constructed from the L1-S1 rigid vertebrae interconnected with hyperelastic fiber-reinforced FE intervertebral discs, ligaments, and facet joints. A mesh convergence study, sensitivity analyses, and systematic calibration were conducted with the hybrid functional spinal unit (FSU) L4/5. The predicted mechanical responses of the FSU L4/5, the lumbar spine (L1-L5), and the LSS were validated against literature data from in vivo and in vitro measurements and in silico models. Spinal mechanical responses considered when loaded with pure moments and combined loading modes were total and intervertebral range of motions, instantaneous axes and centers of rotation, facet joint contact forces, intradiscal pressures, disc bulges, and stiffnesses. Undesirable correlations with the FE mesh were minimized, the number of crisscrossed collagen fiber rings was reduced to five, and the individual influences of specific anatomical structures were adjusted to in vitro range of motions. Including intervertebral motion couplings for axial rotation and nonlinear stiffening under increasing axial compression, the predicted kinematic and structural mechanics responses were consistent with the comparative data. The results demonstrate that the hybrid simulation model is robust and efficient in reproducing valid mechanical responses to provide a starting point for upcoming optimizations and extensions, such as with active skeletal muscles.

In recent years, bioinspired lightweight design has become a high priority in technology. An important source is the musculoskeletal system, which achieves a light construction by the interplay of different effects, which have the aim of minimizing bending stresses. In this paper the potentials for technology and the challenges for a transfer are discussed using kinematic chains as an example. An iterative approach is presented, which represents a solution to integrate the simultaneous optimization process of the musculoskeletal system into the technical product development process.

Kurzfassung Der Digitale Zwilling gewinnt in der Produktentwicklung zunehmend an Bedeutung. Während der Fokus bislang auf der digitalen Abbildung von Eigenschaften technischer Produkte oder Prozesse liegt, greift diese Interpretation für solche Systeme zu kurz, die mit dem Menschen interagieren. Im vorliegenden Beitrag werden anhand ausgewählter Forschungsprojekte Potentiale der Kopplung menschbezogener Modelle mit Digitalen Zwillingen aufgezeigt und aktuelle Herausforderungen diskutiert.

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Inhalt: Der bioinspirierte Strukturleichtbau nimmt in den letzten Jahren einen hohen Stellenwert in der Technik ein. Viele umgesetzte Prinzipien stammen dabei aus dem Muskel-Skelett-System des Menschen, wo ein Leichtbau durch das Zusammenwirken mehrerer beanspruchungsminimierender Effekte erreicht wird. In diesem Artikel wird das Leichtbaupotential für die Technik am Beispiel der Auslegung eines Gelenkarmroboters untersucht. Dabei wird die klassische Auslegung durch ein bioinspiriertes iteratives Verfahren ergänzt, das durch Kopplung von Mehrkörper- simulation und Strukturoptimierung realisiert wird. Anhand eines Vergleichs des berechneten Konstruktionsgewichts und der dynamischen Eigenschaften gegenüber eines klassisch ausgelegten Roboters werden die Vor- und Nachteile diskutiert.

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