02 Fakultät Bau- und Umweltingenieurwissenschaften

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/3

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Institute: search.filters.UBSInstitut.Institut für Modellierung und Simulation Biomechanischer SystemeSubject: search.filters.subject.796

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    ItemOpen Access
    On the load limits of the muscle-tendon unit and their applications in musculoskeletal human body models
    (Stuttgart : Institut für Modellierung und Simulation Biomechanischer Systeme, Computational Biophysics and Biorobotics, 2024) Nölle, Lennart V.; Schmitt, Syn (Prof. Dr.)
    The human skeletal muscle fulfils many movement-related functions, simultaneously acting as the main motor, spring, strut and brake of the body. Equally important for human motion generation are the tendons, which provide passive joint stabilisation and transfer the muscle’s contraction forces to the skeletal structure. Together, muscle and tendon form the muscle-tendon unit (MTU). Despite its ability to withstand many different loading scenarios, the MTU is susceptible to numerous kinds of injury, the most prevalent being the muscle strain injury. The retrospective evaluation of observed injury scenarios and the prediction of injury outcomes and risks has been increasingly important in sports biomechanics, automotive safety and forensic traumatology. For this purpose, numerous injury criteria have been defined for the use with both physical and virtual representations of the human body. While significant efforts in the field of injury severity classification have been made, strain injuries of the MTU have not yet been taken into consideration. This might be because conventional methods of defining injury criteria are not applicable to MTU strain injuries as the properties of the MTU and the nature of MTU strain injuries pose numerous unresolved challenges so far. The primary objective of this dissertation is to overcome these challenges and to define and substantiate MTU strain injury criteria for the use in musculoskeletal human body model simulations. The overarching research question which the presented thesis aims to answer is how injury criteria for strain injuries of the MTU can be defined and which information can be derived from their application. Throughout, the following sub-questions are addressed: 1. How can a strain injury criterion for the muscle be defined and substantiated based on literature data? 2. How can a strain injury criterion for the tendon be defined and applied to the recreation of an injury load case? 3. Which other applications besides injury severity assessment exist for the proposed injury criteria? These questions were tackled consecutively in three journal publications which comprise this dissertation. Sub-question 1 was answered in Contribution 1, where a muscle strain injury criterion (MSIC) was defined based on experimental data from the literature. The resulting injury criterion can differentiate between three levels of injury severity and is easily applicable to the computational representation of any muscle. The injury thresholds were substantiated by comparison to the calculated maximum ultimate tensile strength of mammalian skeletal muscle and through the application of the MSIC in a sprinting gait cycle simulation. The MSIC was also used for a simulation study on the aetiology of muscle strain injuries in which it was shown that material inhomogeneities might cause localised strain injuries within a muscle. To tackle sub-question 2, Contribution 2 built on the findings of Contribution 1 by formulating the tendon strain injury criterion TSIC. This criterion was used to investigate the forces and strains acting on finger flexor tendons during jersey finger injury scenarios. For this purpose, a finite element neuromusculoskeletal hand model was created through the combination of two preexisting models. Additionally, new Hill-type muscle elements were inserted whose parameters were calibrated to fit experimental data. The newly created hand model was used to recreate a simplified jersey finger injury load case under varying muscle activity levels. This simulations study showed that a correlation between muscle activity and sustained injury severity exists. Finally, Contribution 3 set out to answer sub-question 3 and to demonstrate the usefulness of the MSIC and TSIC for applications other than injury severity assessment. For this, common modelling issues present in musculoskeletal human body models were first recreated and then detected using the proposed criteria. First, the deformation of a finite element model’s skeletal structure during model repositioning was identified through an MSIC assessment of muscles spanning a displaced joint. Second, an ill-tuned muscle parameter within an otherwise physiological model was found through applying the TSIC to a multibody gait cycle simulation. Additionally, a new method for determining minor TSIC thresholds for arbitrarily parameterised tendons was developed, thus improving the usability of the TSIC. The cumulative result of this thesis is a strain injury criterion for the MTU which, to the author’s knowledge, is the first of its kind. Additionally, a new method for evaluating the quality of musculoskeletal human body models was provided. Future studies should focus on the experimental validation of the proposed injury criteria and on expanding them by statistical metrics. Potential application scenarios of the MSIC and TSIC, besides injury evaluation, are as model assessment tools or in ergonomics.
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    A systematic review and meta-analysis on the longitudinal effects of unilateral knee extension exercise on muscle strength
    (2020) Altan, Ekin; Seide, Svenja; Bayram, Ismail; Gizzi, Leonardo; Ertan, Hayri; Röhrle, Oliver
    The aim of the study was to investigate the time-dependent increase in the knee extensors' isometric strength as a response to voluntary, unilateral, isometric knee extension exercise (UIKEE). To do so, a systematic review was carried out to obtain data for a Bayesian longitudinal model-based meta-analysis (BLMBMA). For the systematic review, PubMed, Web of Science, SCOPUS, Chochrane Library were used as databases. The systematic review included only studies that reported on healthy, young individuals performing UIKEE. Studies utilizing a bilateral training protocol were excluded as the focus of this review lied on unilateral training. Out of the 3,870 studies, which were reviewed, 20 studies fulfilled the selected inclusion criteria. These 20 studies were included in the BLMBMA to investigate the time-dependent effects of UIKEE. If compared to the baseline strength of the trained limb, these data reveal that UKIEE can increase the isometric strength by up to 46%. A meta-analysis based on the last time-point of each available study was employed to support further investigations into UIKEE-induced strength increase. A sensitivity analysis showed that intensity of training (%MVC), fraction of male subjects and the average age of the subject had no significant influence on the strength gain. Convergence of BLMBMA revealed that the peak strength increase is reached after ~4 weeks of UIKEE training.
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    3D ultrasound-based determination of skeletal muscle fascicle orientations
    (2024) Sahrmann, Annika S.; Vosse, Lukas; Siebert, Tobias; Handsfield, Geoffrey G.; Röhrle, Oliver
    Architectural parameters of skeletal muscle such as pennation angle provide valuable information on muscle function, since they can be related to the muscle force generating capacity, fiber packing, and contraction velocity. In this paper, we introduce a 3D ultrasound-based workflow for determining 3D fascicle orientations of skeletal muscles. We used a custom-designed automated motor driven 3D ultrasound scanning system for obtaining 3D ultrasound images. From these, we applied a custom-developed multiscale-vessel enhancement filter-based fascicle detection algorithm and determined muscle volume and pennation angle. We conducted trials on a phantom and on the human tibialis anterior (TA) muscle of 10 healthy subjects in plantarflexion (157 ± 7 ∘), neutral position (109 ± 7 ∘, corresponding to neutral standing), and one resting position in between (145 ± 6 ∘). The results of the phantom trials showed a high accuracy with a mean absolute error of 0.92 ± 0.59 ∘. TA pennation angles were significantly different between all positions for the deep muscle compartment; for the superficial compartment, angles are significantly increased for neutral position compared to plantarflexion and resting position. Pennation angles were also significantly different between superficial and deep compartment. The results of constant muscle volumes across the 3 ankle joint angles indicate the suitability of the method for capturing 3D muscle geometry. Absolute pennation angles in our study were slightly lower than recent literature. Decreased pennation angles during plantarflexion are consistent with previous studies. The presented method demonstrates the possibility of determining 3D fascicle orientations of the TA muscle in vivo.