TY - GEN A1 - Aurbach, Maximilian A1 - Spicka, Jan A1 - Süß, Franz A1 - Dendorfer, Sebastian T1 - Musculoskeletal modelling of the shoulder – effects on muscle recruitment and joint reaction force T2 - European Society of Biomechanics meeting 2019, Vienna, Austria Y1 - 2019 UR - https://owncloud.tuwien.ac.at/index.php/s/dovqqcj02VeZHze ER - TY - GEN A1 - Kubowitsch, Simone A1 - Süß, Franz A1 - Jansen, Petra A1 - Dendorfer, Sebastian T1 - Effect of dual tasking on muscular imbalances T2 - European Society of Biomechanics meeting 2019, Vienna, Austria Y1 - 2019 UR - https://owncloud.tuwien.ac.at/index.php/s/dovqqcj02VeZHze ER - TY - GEN A1 - Auer, Simon A1 - Reinker, Lukas A1 - Dendorfer, Sebastian T1 - Evaluation of muscle recruitment and muscle models in musculoskeletal simulation of dynamic motion T2 - 26th Congress of the European Society of Biomechanics, July 11-14, 2021, Milan, Italy N2 - Musculoskeletal simulation plays an increasingly important role in sports biomechanics. In the last years, the field of application widened from orthopaedics and ergonomics to sports [1]. A muscle recruitment algorithm with a quadratic objective function is usually used to calculate muscle activity in dynamic movements. The agreement of calculated and measured thigh muscle activity has already been investigated [2]. They found a strong agreement for sprinting and running, while the correlation decreased for side-cutting manoeuvres. Nevertheless, the influence of different muscle recruitment criteria on muscle activity in dynamic musculoskeletal simulations is currently unknown. Hence, this study aimed to analyse the effect of different muscle recruitment criteria and muscle models on the correlation of numerical and measured muscle activity in highly dynamic movements. KW - esb KW - biomechanics KW - muscle recruitment Y1 - 2021 UR - https://esbiomech.org/conference/archive/2021milan/Contribution_1719.pdf CY - Milan ER - TY - GEN A1 - Melzner, Maximilian A1 - Pfeifer, Christian A1 - Alt, V. A1 - Süß, Franz A1 - Dendorfer, Sebastian T1 - Änderung der Gelenkreaktionskraft bei Schädigung des medialen Bandapparates im Ellenbogen T2 - Zeitschrift fur Orthopadie und Unfallchirurgie KW - Muskuloskelettale Simulation KW - Ellenbogenstabilität Y1 - 2020 U6 - https://doi.org/10.1055/s-0040-1717270 N1 - Poster VL - 158 IS - S01 PB - Thieme ER - TY - JOUR A1 - Auer, Simon A1 - Schiebl, Jonas A1 - Iversen, Kristoffer A1 - Subhash Chander, Divyaksh A1 - Damsgaard, Michael A1 - Dendorfer, Sebastian T1 - Biomechanical assessment of the design and efficiency of occupational exoskeletons with the AnyBody Modeling System JF - Zeitschrift für Arbeitswissenschaften N2 - Exoskeletons were invented over 100 years ago but have only become popular in the last two decades, especially in the working industry as they can decrease work-related loads significantly. The most often used exoskeletons are for the lower back and shoulder since these are commonly affected body regions. All devices have in common that their purpose is to reduce internal loads of vulnerable body regions. Nevertheless, there is still little understanding on how biomechanical loading in the human body changes when exoskeletons are used. Therefore, further analyses are needed. A promising candidate for these are musculoskeletal models, which are based on an inverse dynamics approach and can calculate external parameters such as ground reaction forces or other interaction forces as well as internal parameters such as joint reaction forces or muscle activities. The various examples in the literature show that these models are increasingly used for assessing the biomechanical effects of exoskeletons on the human body. Furthermore, musculoskeletal models can calculate biomechanical loadings of humans with and without exoskeletons for all kinds of applications and allow an evaluation of their purpose. Practical Relevance: This article highlights the possibilities of musculoskeletal models for assessing the design and efficiency of occupational exoskeletons. Several practical use cases are described along with distinct descriptions of common implications of musculoskeletal and exoskeleton modeling. KW - Biomechanics KW - Ergonomics KW - Motion capture KW - Inverse dynamics Y1 - 2022 U6 - https://doi.org/10.1007/s41449-022-00336-4 N1 - Corresponding author: Sebastian Dendorfer VL - 76 IS - 4 SP - 440 EP - 449 PB - Springer Nature ER - TY - JOUR A1 - Melzner, Maximilian A1 - Pfeiffer, Christian A1 - Suess, Franz A1 - Dendorfer, Sebastian T1 - Musculoskeletal simulation of elbow stability for common injury patterns JF - Journal of Orthopaedic Research N2 - Elbow stability is derived from a combination of muscular, ligamentous, and bony structures. After an elbow trauma the stability of the joint is an important decision criterion for the subsequent treatment. The decision regarding non-operative/operative care depends mostly on subjective assessments of medical experts. Therefore, the aim of this study is to use musculoskeletal simulations as an objective assessment tool to investigate the extent to which failure of different stabilizers affects the elbow stability and how these observations correspond to the assessment from clinical practice. A musculoskeletal elbow simulation model was developed for this aim. To investigate the stability of the elbow, varus/valgus moments were applied under 0°, 45°and 90° flexion while the respective cubital angle was analyzed. This was performed for nine different injury scenarios, which were also evaluated for stability by clinical experts. With the results, it can be determined by which injury pattern and under which flexion angle the elbow stability is impaired regarding varus/valgus moments. The scenario with a complete failure of the medial and lateral ligaments and a fracture of the radial head was identified as having the greatest instability. The study presented a numerical determination of elbow stability against varus/valgus moments regarding clinical injury patterns, as well as a comparison of the numerical outcome with experience gained in clinical practice. The numerical predictions agree well with the assessments of the clinical specialists. Thus, the results from musculoskeletal simulation can make an important contribution to a more objective assessment of the elbow stability. KW - AnyBody KW - musculoskeletal simulation KW - elbow stability Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-54819 SN - 1554-527X N1 - Corresponding author: Maximilian Melzner VL - 41 IS - 6 SP - 1356 EP - 1364 PB - Wiley ER - TY - JOUR A1 - Reinker, Lukas A1 - Dendorfer, Sebastian T1 - Evaluation of acceleration patterns during high-impact jumping exercises JF - Gait & Posture Y1 - 2023 U6 - https://doi.org/10.1016/j.gaitpost.2022.11.051 VL - 100 IS - Supplement 1, March SP - 93 EP - 94 PB - Elsevier CY - Amsterdam [u.a.] ER - TY - JOUR A1 - Reinker, Lukas A1 - Bläsing, Dominic A1 - Bierl, Rudolf A1 - Ulbricht, Sabina A1 - Dendorfer, Sebastian T1 - Correlation of Acceleration Curves in Gravitational Direction for Different Body Segments during High-Impact Jumping Exercises JF - sensors N2 - Osteoporosis is a common disease of old age. However, in many cases, it can be very well prevented and counteracted with physical activity, especially high-impact exercises. Wearables have the potential to provide data that can help with continuous monitoring of patients during therapy phases or preventive exercise programs in everyday life. This study aimed to determine the accuracy and reliability of measured acceleration data at different body positions compared to accelerations at the pelvis during different jumping exercises. Accelerations at the hips have been investigated in previous studies with regard to osteoporosis prevention. Data were collected using an IMU-based motion capture system (Xsens) consisting of 17 sensors. Forty-nine subjects were included in this study. The analysis shows the correlation between impacts and the corresponding drop height, which are dependent on the respective exercise. Very high correlations (0.83–0.94) were found between accelerations at the pelvis and the other measured segments at the upper body. The foot sensors provided very weak correlations (0.20–0.27). Accelerations measured at the pelvis during jumping exercises can be tracked very well on the upper body and upper extremities, including locations where smart devices are typically worn, which gives possibilities for remote and continuous monitoring of programs. KW - osteoporosis KW - inertial measurement units KW - wearable motion-tracking sensors KW - high-impact exercisess Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-58217 N1 - Corresponding author: Lukas Reinker N1 - This work was supported by the Bavarian Academic Forum [BayWISS-Verbundkolleg Gesundheit] and the DHZK fond for behavioral cardiovascular diseases [Behaviorale kardiovaskuläre Erkrankungen; grand number: 81Z0400105]. VL - 23 IS - 4 PB - MDPI CY - Basel ER - TY - JOUR A1 - Mühling, Mischa A1 - Sandriesser, Sabrina A1 - Dendorfer, Sebastian A1 - Augat, Peter T1 - Assessment of implant internal stresses under physiological femoral loading: Translation to a simplified bending load model JF - Journal of Biomechanics N2 - The success of surgical treatment for fractures hinges on various factors, notably accurate surgical indication. The process of developing and certifying a new osteosynthesis device is a lengthy and costly process that requires multiple cycles of review and validation. Current methods, however, often rely on predecessor standards rather than physiological loads in specific anatomical locations. This study aimed to determine actual loads experienced by an osteosynthesis plate, exemplified by a standard locking plate for the femoral shaft, utilizing finite elements analysis (FEA) and to obtain the bending moments for implant development standard tests. A protocol was developed, involving the creation and validation of a fractured femur model fixed with a locking plate, mechanical testing, and FEA. The model’s validation demonstrated exceptional accuracy in predicting deformations, and the FEA revealed peak stresses in the fracture bridging zone. Results of a parametric analysis indicate that larger fracture gaps significantly impact implant mechanical behavior, potentially compromising stability. This study underscores the critical need for realistic physiological conditions in implant evaluations, providing an innovative translational approach to identify internal loads and optimize implant designs. In conclusion, this research contributes to enhancing the understanding of implant performance under physiological conditions, promoting improved designs and evaluations in fracture treatments. KW - bone biomechanics KW - finite elements analysis KW - femoral fracture KW - Euler-Bernoulli-Beam-Theory KW - simplified loading model Y1 - 2024 U6 - https://doi.org/10.1016/j.jbiomech.2024.112229 SN - 1873-2380 IS - 112229 PB - Elsevier ER - TY - INPR A1 - Förstl, Nikolas A1 - Adler, Ina A1 - Süß, Franz A1 - Dendorfer, Sebastian T1 - Technologies for Evaluation of Pelvic Floor Functionality: A Systematic Review N2 - Pelvic floor dysfunction is a common problem in women and has a negative impact ontheir quality of life. The aim of this review was to provide a general overview of the current state oftechnology used to assess pelvic floor functionality. It also provides literature research of the phys-iological and anatomical factors that correlate with pelvic floor health. The systematic review wasconducted according to the PRISMA guidelines. PubMed, ScienceDirect, Cochrane Library andIEEE databases were searched for publications on sensor technology for the assessment of pelvicfloor functionality. Anatomical and physiological parameters were identified through a manualsearch. In the systematic review 115 publications were included. 12 different sensor technologieswere identified. Information on the obtained parameters, sensor position, test activities and subjectcharacteristics were prepared in tabular form from each publication. 16 anatomical and physiologi- cal parameters influencing pelvic floor health were identified in 17 published studies and rankedfor their statistical significance. Taken together, this review could serve as a basis for the develop-ment of novel sensors which could allow for quantifiable prevention and diagnosis, as well as par-ticularized documentation of rehabilitation processes related to pelvic floor dysfunctions. KW - pelvic floor KW - sensors KW - functionality KW - influence parameters Y1 - 2024 U6 - https://doi.org/10.31219/osf.io/dcqyg N1 - Der Aufsatz wurde peer-reviewd veröffentlich und ist ebenfalls in diesem Repositorium verzeichnet unter: https://opus4.kobv.de/opus4-oth-regensburg/frontdoor/index/index/docId/7321 PB - Center for Open Science ER - TY - JOUR A1 - Auer, Simon A1 - Kubowitsch, Simone A1 - Dendorfer, Sebastian T1 - Kombinierter Einfluss von psychologischen und biomechanischen Faktoren auf die muskulären Belastungen beim Fußballspielen JF - Die Orthopädie N2 - When mental stress and musculoskeletal loading interact, the risk for injury increases due to altered body kinematics and increased muscle tension. These changes can be detected with musculoskeletal models, and mental loading and stress must be analyzed at emotional, cognitive, and behavioral levels. To investigate these kinematic and loading changes under stress, competitive athletes were subjected to mental stress during highly dynamic movements, and musculoskeletal models were used to analyze the biomechanical loading. It was shown that under mental stress, independent of the subjective perception, a strong change in muscle forces can occur. Accordingly, competitive athletes should undergo screenings to assess individual movement patterns and promote general stress resilience. N2 - Für Fußballer:innen stellen muskuläre Verletzungen der unteren Extremitäten ein großes Problem dar. Ein Beispiel hierfür liefert die Nationalmannschaftsstürmerin Alexandra Popp, die aufgrund muskulärer Probleme das EM-Finale 2022 in Wembley kurzfristig verpasste. Oftmals stehen gerade hohe Anspannungssituationen in zeitlichem Zusammenhang mit Verletzungen, der Einfluss der psychischen Beanspruchung auf die biomechanischen Belastungen wird jedoch meist nur wenig beachtet. KW - Biologische Modelle KW - Biomechanik KW - Leistungssportler KW - Bewegung KW - Resilienz, psychologische KW - Biological models KW - Biomechanics KW - Elite athletes KW - Movement KW - Resilience, psychological Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-65113 N1 - Corresponding author: Sebastian Dendorfer VL - 52 IS - 11 SP - 1 EP - 6 PB - Springer ER - TY - JOUR A1 - Dendorfer, Sebastian A1 - Gschoßman, Lukas T1 - Hightech in der Rehabiliation JF - BVOU Infobrief: Hightech in Orthopädie und Unfallchirurgie N2 - Aufgrund der steigenden Lebenserwartung und dem damit einhergehenden demographischen Wandel wird der Bedarf an Rehabilitations-Behandlungen in absehbarer Zukunft stark ansteigen. Ein Beispiel für diesen Trend ist die physiotherapeutische Behandlung nach Erhalt einer Knie-Totalendoprothese (Knie-TEP). So gehen Modellrechnungen basierend auf dem Bevölkerungswachstum und der bisherigen Prävalenz von Knie-TEPs davon aus, dass die Anzahl an durchgeführten Eingriffen in einkommensstarken Ländern wie Deutschland weiter zunehmen wird. Weiterhin stoßen traditionelle Rehabilitationsverfahren, gerade in strukturschwachen Regionen, schon heute an ihre Grenzen. Deutlich zu sehen war das während den Hochphasen der aktuellen Covid-19-Pandemie, als der Kontakt zwischen Therapeut*in und Patient*in flächendeckend eingeschränkt war. Eine erhöhte Nachfrage nach neuartigen Reha-Angeboten ist die logische Konsequenz. Innovative Konzepte sind daher dringend notwendig, um die daraus resultierenden technischen, sozialen und ökonomischen Herausforderungen zu bewältigen. Y1 - 2023 UR - https://www.bvou.net/infobrief-1-23/ SN - 2747-5913 IS - 1 SP - 9 EP - 11 PB - BVOU – Berufsverband für Orthopädie und Unfallchirurgie e.V. CY - Berlin ER - TY - JOUR A1 - Rusavy, Zdenek A1 - Cechova, Hana A1 - Dendorfer, Sebastian A1 - Kalis, Vladimir A1 - Ismail, Khaled M. T1 - Is the Finnish grip tight enough? A manometric study of two manual perineal protection techniques JF - Acta Obstetricia et Gynecologica Scandinavica Y1 - 2024 U6 - https://doi.org/10.1111/aogs.15033 PB - Wiley ET - Early view ER - TY - JOUR A1 - Schaeffer, Leon A1 - Herrmann, David A1 - Schratzenstaller, Thomas A1 - Dendorfer, Sebastian A1 - Böhm, Valter T1 - Preliminary theoretical considerations on the stiffness characteristics of a tensegrity joint for the use in dynamic orthoses JF - Journal of Medical Robotics Research N2 - Early motion therapy plays an important role for effective long-term healing of joint injuries. In many cases, conventional dynamic orthoses fail to address the intricate movement possibilities of the underlying joints, limited by their simplistic joint representations, often represented by revolute joints, enabling rotations by only one axis. In this paper, a two-dimensional compliant tensegrity joint for use in biomedical applications is investigated. It consists of two compressed members and five compliant tensioned members. Relative movement possibilities are realized by the intrinsic compliance of the structure. In the development of these systems, the first step is the determination of the static stable equilibrium. This analysis is conducted in this paper by considering the potential energy approach or by using the geometric nonlinear finite element method. The mechanical behavior of the structure is assessed with a specific emphasis on its mechanical compliance. The primary objective of this study is the investigation of the influence of structural parameters on the overall stiffness and movability of the structure. The results underscore the significant effect of member parameters on the stiffness and movability of the compliant tensegrity joint, particularly under varying load magnitudes. These findings provide insights for optimizing the joint’s performance, contributing to its potential application in advanced orthotic and exoskeleton devices. KW - mechanical compliance KW - flexibility ellipsis KW - form-finding KW - tensegrity joint Y1 - 2023 U6 - https://doi.org/10.1142/S2424905X23400081 PB - World Scientific ER - TY - CHAP A1 - Dendorfer, Sebastian A1 - Feldotto, Benedikt A1 - Walch, Blasius A1 - Koch, Patrick A1 - Knoll, Alois T1 - Co-Development of an Infant Prototype in Hardware and Simulation based on CT Imaging Data T2 - IEEE International Conference on Cyborg and Bionic Systems (CBS), 2019, Munich N2 - The development of biomimetic robots has gained research interest in the last years as it may both help under-standing processes of motion execution in biological systems as well as developping a novel generation of intelligent and energy efficient robots. However, exact model generation that builds up on observations and robot design is very time intensive. In this paper we present a novel pipeline for co-development of biomimetic hardware and simulation models based on biological Computer Tomography (CT) data. For this purpose we exploit State of the Art rapid prototyping technologies such as 3D Printing and the Neurorobotics Platform for musculoskeletal simulations in virtual environments. The co-development integrates both advantages of virtual and physical experimental models and is expected to increase development speed of controllers that can be tested on the simulated counterpart before application to a printed robot model. We demonstrate the pipeline by generating a one year old infant model as a musculoskeletal simulation model and a print-in-place 3D printed skeleton as a single movable part. Even though we hereonly introduce the initial body generation and only a first testsetup for a modular sensory and control framework, we can clearly spot advantages in terms of rapid model generation and highly biological related models. Engineering costs are reducedand models can be provided to a wide research community for controller testing in an early development phase. KW - Biomechanische Analyse KW - Robotik KW - Computertomographie KW - 3D-Druck Y1 - 2019 UR - http://mediatum.ub.tum.de/doc/1520042/985669104579.pdf ER - TY - JOUR A1 - Schmitz, Paul A1 - Neumann, Christoph Cornelius A1 - Neumann, Carsten A1 - Nerlich, Michael A1 - Dendorfer, Sebastian T1 - Biomechanical analysis of iliac crest loading following cortico-cancellous bone harvesting JF - Journal of Orthopaedic Surgery and Research N2 - Background Iliac crest bone harvesting is a frequently performed surgical procedure widely used to treat bone defects. The objective of this study is to assess the biomechanical quantities related to risk for pelvic fracture after harvesting an autologous bone graft at the anterior iliac crest. Methods Finite element models with a simulated harvest site (sized 15 × 20 mm, 15 × 35 mm, 30 × 20 mm and 30 × 35 mm) in the iliac wing are created. The relevant loading case is when the ipsilateral leg is lifted off the ground. Musculoskeletal analysis is utilized to compute the muscle and joint forces involved in this motion. These forces are used as boundary conditions for the finite element analyses. Bone tissue stress is analyzed. Results Critical stress peaks are located between the anterior superior iliac spine (ASIS) and the anterior edge of the harvest site. Irrespective of the graft size, the iliac wing does not show any significant stress peaks with the harvest site being 20 to 25 mm posterior to the ASIS. The harvest area itself inhibits the distribution of the forces applied on the ASIS to extend to the posterior iliac wing. This leads to a lack of stress posterior to the harvest site. A balanced stress distribution with no stress peaks appears when the bone graft is taken below the iliac crest. Conclusion A harvest site located at least 20 to 25 mm posterior to the ASIS should be preferred to minimize the risk of iliac fatigue fracture. KW - Bone harvesting KW - Autologous bone graft KW - Iliac crest KW - Fatigue fracture KW - Pelvis KW - ASIS KW - FEA KW - Biomechanical investigation KW - Beckenkammknochen KW - Knochenentnahme KW - Spongiosa KW - Biomechanische Analyse Y1 - 2018 U6 - https://doi.org/10.1186/s13018-018-0822-1 VL - 13 IS - 108 SP - 1 EP - 8 PB - Springer Nature ER - TY - JOUR A1 - Völlner, Florian A1 - Weber, Tim A. A1 - Weber, Markus A1 - Renkawitz, Tobias A1 - Dendorfer, Sebastian A1 - Grifka, Joachim A1 - Craiovan, Benjamin T1 - A simple method for determining ligament stiffness during total knee arthroplasty in vivo JF - Scientific Reports N2 - A key requirement in both native knee joints and total knee arthroplasty is a stable capsular ligament complex. However, knee stability is highly individual and ranges from clinically loose to tight. So far, hardly any in vivo data on the intrinsic mechanical of the knee are available. This study investigated if stiffness of the native ligament complex may be determined in vivo using a standard knee balancer. Measurements were obtained with a commercially available knee balancer, which was initially calibrated in vitro. 5 patients underwent reconstruction of the force-displacement curves of the ligament complex. Stiffness of the medial and lateral compartments were calculated to measure the stability of the capsular ligament complex. All force-displacement curves consisted of a non-linear section at the beginning and of a linear section from about 80 N onwards. The medial compartment showed values of 28.4 ± 1.2 N/mm for minimum stiffness and of 39.9 ± 1.1 N/mm for maximum stiffness; the respective values for the lateral compartment were 19.9 ± 0.9 N/mm and 46.6 ± 0.8 N/mm. A commercially available knee balancer may be calibrated for measuring stiffness of knee ligament complex in vivo, which may contribute to a better understanding of the intrinsic mechanical behaviour of knee joints. KW - Biomechanische Analyse KW - Kniegelenkband KW - Steifigkeit Y1 - 2019 U6 - https://doi.org/10.1038/s41598-019-41732-x VL - 9 SP - 1 EP - 8 PB - Nature ER - TY - JOUR A1 - Benditz, Achim A1 - Auer, Simon A1 - Spörrer, J.F. A1 - Wolkerstorfer, S. A1 - Grifka, Joachim A1 - Süß, Franz A1 - Dendorfer, Sebastian T1 - Regarding loads after spinal fusion, every level should be seen separately: a musculoskeletal analysis JF - European Spine Journal N2 - The number of spinal fusion surgeries is steadily increasing and biomechanical consequences are still in debate. The aim of this study is to provide biomechanical insights into the sagittal balance of the spine and to compare spinal load before and after spinal fusion. METHOD: The joint reaction forces of 52 patients were analyzed in proximo-distal and antero-posterior direction from the levels T12-L1 to L5-S1 using musculoskeletal simulations. RESULTS: In 104 simulations, pre-surgical forces were equal to post-surgical. The levels L4-L5 and T12-L1, however, showed increased spinal forces compression forces with higher sagittal displacement. Improved restauration of sagittal balance was accompanied by lower spinal load. AP shear stress, interestingly decreased with sagittal imbalance. CONCLUSION: Imbalanced spines have a risk of increased compression forces at Th12-L1. L4-L5 always has increased spinal loads. These slides can be retrieved under Electronic Supplementary Material. KW - AnyBody Modeling System KW - Musculoskeletal analysis KW - Sagittal balance KW - Spinal fusion KW - Spine biomechanics KW - Biomechanische Analyse KW - Wirbelsäulenversteifung KW - Vergleichende Anatomie Y1 - 2018 U6 - https://doi.org/10.1007/s00586-018-5476-5 VL - 27 IS - 8 SP - 1905 EP - 1910 PB - Springer-Verlag ER - TY - CHAP A1 - Jungtäubl, Dominik A1 - Schmitz, Paul A1 - Gross, Simon A1 - Dendorfer, Sebastian ED - Badnjevic, Almir T1 - FEA of the transiliacal internal fixator as an osteosynthesis of pelvic ring fractures T2 - CMBEBIH 2017, Proceedings of the International Conference on Medical and Biological Engineering 2017 N2 - Common Schanz screw systems can be used to stabilize pelvic ring fractures. In order to accommodate for different patient’s requirements, implants can be placed in cranio-caudal direction into the os ilium (T1), or into the supraacetabular bone canal, and thus, in dorso-ventral direction (T2). Whereas both techniques are currently used, no data of the biomechanical behavior is available up to this date. The aim of this study is to analyze, whether T2 shows biomechanical advantages with respect to tissue and implant stresses due to the enlarged bone-implant interface. Forces acting on the pelvis were analyzed using motion capture data of a gait cycle obtained by the utilization of a musculoskeletal simulation program. A three dimensional finite element (FE) model of the pelvis with grayscale-based material properties was generated. The muscle and joint reaction forces at toe-off were applied to the FE model and instable pelvis fractures were implemented. The osteosynthesis systems were positioned within the model in order to enable the comparison between the two different surgical techniques. Stresses and displacements were analyzed for bone tissue, fracture zone and implant. T2 lead to approx. 30% larger displacements in the fracture zone. Von-Mises stresses were larger for T2 in the implant (80 MPa vs. 227 MPa), whereas T1 leads to larger stresses in the bone tissue (200 MPa vs. 140 MPa). Both implantation techniques showed a good biomechanical behavior. Differences could be found with respect to tissue strains and deformations in the fracture zone. If bone quality or fracture healing are of concern, T2 or T1 should be used, respectively. However, both techniques seem to be applicable for cases with no special requirements. Further analyses aim to investigate the behavior under cyclic loading. KW - Finite element analysis KW - Musculoskeletal simulation KW - Internal fixator KW - Pelvic ring fracture KW - Beckenbruch KW - Operationstechnik KW - Finite-Elemente-Methode KW - Biomechanik KW - Simulation Y1 - 2017 SN - 978-981-10-4165-5 U6 - https://doi.org/10.1007/978-981-10-4166-2_32 SP - 212 EP - 217 PB - Springer CY - Singapore ER - TY - JOUR A1 - Renkawitz, Tobias A1 - Weber, Tim A. A1 - Dullien, Silvia A1 - Woerner, Michael A1 - Dendorfer, Sebastian A1 - Grifka, Joachim A1 - Weber, Markus T1 - Leg length and offset differences above 5 mm after total hip arthroplasty are associated with altered gait kinematics JF - Gait & Posture N2 - We aimed to investigate the relationship between postoperative leg length/offset (LL/OS) reconstruction and gait performance after total hip arthroplasty (THA). In the course of a prospective randomized controlled trial, 60 patients with unilateral hip arthrosis received cementless THA through a minimally-invasive anterolateral surgical approach. One year post-operatively, LL and global OS restoration were analyzed and compared to the contralateral hip on AP pelvic radiographs. The combined postoperative limb length/OS reconstruction of the operated hip was categorized as restored (within 5 mm) or non-restored (more than 5 mm reduction or more than 5 mm increment). The acetabular component inclination, anteversion and femoral component anteversion were evaluated using CT scans of the pelvis and the femur. 3D gait analysis of the lower extremity and patient related outcome measures (HHS, HOOS, EQ-5D) were obtained pre-operatively, six months and twelve months post-operatively by an observer blinded to radiographic results. Component position of cup and stem was comparable between the restored and non-restored group. Combined LL and OS restoration within 5 mm resulted in higher Froude number (p < 0.001), normalized walking speed (p < 0.001) and hip range-of-motion (ROM) (p = 0.004) during gait twelve months postoperatively, whereas gait symmetry was comparable regardless of LL and OS reconstruction at both examinations. Clinical scores did not show any relevant association between the accuracy of LL or OS reconstruction and gait six/twelve months after THA. In summary, postoperative LL/OS discrepancies larger than 5 mm relate to unphysiological gait kinematics within the first year after THA. DRKS00000739, German Clinical Trials Register. KW - THA KW - Leg length KW - Offset KW - Gait analysis KW - Biomechanics Y1 - 2016 U6 - https://doi.org/10.1016/j.gaitpost.2016.07.011 VL - vol. 49 SP - 196 EP - 201 ER - TY - JOUR A1 - Putzer, Michael A1 - Auer, Stefan A1 - Malpica, William A1 - Süß, Franz A1 - Dendorfer, Sebastian T1 - A numerical study to determine the effect of ligament stiffness on kinematics of the lumbar spine during flexion JF - BMC Musculoskeletal Disorders N2 - Background There is a wide range of mechanical properties of spinal ligaments documented in literature. Due to the fact that ligaments contribute in stabilizing the spine by limiting excessive intersegmental motion, those properties are of particular interest for the implementation in musculoskeletal models. The aim of this study was to investigate the effect of varying ligament stiffness on the kinematic behaviour of the lumbar spine. Methods A musculoskeletal model with a detailed lumbar spine was modified according to fluoroscopic recordings and corresponding data files of three different subjects. For flexion, inverse dynamics analysis with a variation of the ligament stiffness matrix were conducted. The influence of several degrees of ligament stiffness on the lumbar spine model were investigated by tracking ligament forces, disc forces and resulting moments generated by the ligaments. Additionally, the kinematics of the motion segments were evaluated. Results An increase of ligament stiffness resulted in an increase of ligament and disc forces, whereas the relative change of disc force increased at a higher rate at the L4/L5 level (19 %) than at the L3/L4 (10 %) level in a fully flexed posture. The same behaviour applied to measured moments with 67 % and 45 %. As a consequence, the motion deflected to the lower levels of the lumbar spine and the lower discs had to resist an increase in loading. Conclusions Higher values of ligament stiffness over all lumbar levels could lead to a shift of the loading and the motion between segments to the lower lumbar levels. This could lead to an increased risk for the lower lumbar parts. KW - Lumbar spine KW - Ligament stiffness KW - Musculoskeletal Modeling KW - Biomechanics Y1 - 2016 U6 - https://doi.org/10.1186/s12891-016-0942-x VL - 17 IS - 95 ER - TY - JOUR A1 - Weber, Tim A. A1 - Dendorfer, Sebastian A1 - Bulstra, Sjoerd K. A1 - Grifka, Joachim A1 - Verkerke, Gijsbertus Jacob A1 - Renkawitz, Tobias T1 - Gait six month and one-year after computer assisted Femur First THR vs. conventional THR. Results of a patient- and observer- blinded randomized controlled trial JF - Gait & Posture N2 - A prospective randomized controlled trial is presented that is used to compare gait performance between the computer assisted Femur First (CAS FF) operation method and conventional THR (CON). 60 patients underwent a 3D gait analysis of the lower extremity at pre-operative, 6 months post-operative and twelve months post-operative. Detailed verification experiments were facilitated to ensure the quality of data as well as to avoid over-interpreting of the data. The results confirm a similar data-quality as reported in the literature. Walking speed, range of motion and symmetry thereof improved over the follow-up period, without significant differences between the groups. While all parameters do significantly increase over the follow-up period for both groups, there were no significant differences between them at any given time-point. Patients undergoing CAS FF showed a trend to improved hip flexion angle indicating a possible long-term benefit. KW - Biomechanics KW - Combined anteversion KW - Computer-assisted surgery KW - Femur first KW - Gait analysis Y1 - 2016 U6 - https://doi.org/10.1016/j.gaitpost.2016.06.035 VL - vol. 49 SP - 418 EP - 425 ER - TY - CHAP A1 - Dendorfer, Sebastian A1 - Kubowitsch, Simone A1 - Süß, Franz T1 - How to determine the effect of working conditions on the human body T2 - 11th International Scientific Conference on Production Engineering DEVELOPMENT AND MODERNIZATION OF PRODUCTION (RIM 2017), Sarajevo, Bosnia and Herzegovina N2 - Work places and conditions strains the human body, both psychologically and biomechanically. In order to analyse working conditions and in the following to improve them, detailed knowledge about the effect of the different stressors on the body is needed. This manuscript discusses methods on how to evaluate biomechanical and mental loading and its effect on the musculoskeletal system. A possible workflow for the analysis is presented. KW - Arbeitsbedingungen KW - Körper KW - Mensch Y1 - 2017 UR - https://tfb.ba/repozitorij/2/RIM/RIM2017/01A-Sebastian%20Dendorfer,%20Simone%20Kubowitsch,%20Franz%20S%C3%BC%C3%9F-HOW%20TO%20DETERMINE%20THE%20EFFECT%20OF%20WORKING%20CONDITIONS%20ON%20THE%20HUMAN%20BODY.pdf ER - TY - JOUR A1 - Ignasiak, Dominika A1 - Dendorfer, Sebastian A1 - Ferguson, Stephen J. T1 - Thoracolumbar spine model with articulated ribcage for the prediction of dynamic spinal loading JF - Journal of Biomechanics N2 - Musculoskeletal modeling offers an invaluable insight into the spine biomechanics. A better understanding of thoracic spine kinetics is essential for understanding disease processes and developing new prevention and treatment methods. Current models of the thoracic region are not designed for segmental load estimation, or do not include the complex construct of the ribcage, despite its potentially important role in load transmission. In this paper, we describe a numerical musculoskeletal model of the thoracolumbar spine with articulated ribcage, modeled as a system of individual vertebral segments, elastic elements and thoracic muscles, based on a previously established lumbar spine model and data from the literature. The inverse dynamics simulations of the model allow the prediction of spinal loading as well as costal joints kinetics and kinematics. The intradiscal pressure predicted by the model correlated well (R2=0.89) with reported intradiscal pressure measurements, providing a first validation of the model. The inclusion of the ribcage did not affect segmental force predictions when the thoracic spine did not perform motion. During thoracic motion tasks, the ribcage had an important influence on the predicted compressive forces and muscle activation patterns. The compressive forces were reduced by up to 32%, or distributed more evenly between thoracic vertebrae, when compared to the predictions of the model without ribcage, for mild thoracic flexion and hyperextension tasks, respectively. The presented musculoskeletal model provides a tool for investigating thoracic spine loading and load sharing between vertebral column and ribcage during dynamic activities. Further validation for specific applications is still necessary. KW - Inverse dynamics KW - Musculoskeletal model KW - Thoracolumbar spine KW - Brustwirbelsäule KW - Brustkorb KW - Biomechanik KW - Mechanische Belastung KW - Prognose Y1 - 2016 U6 - https://doi.org/10.1016/j.jbiomech.2015.10.010 VL - vol. 49 IS - 6 SP - 959 EP - 966 PB - Elsevier Science ER -