TY - JOUR A1 - Lazarev, I.A. A1 - Ryabokon, P.V. A1 - Haller, M. A1 - Dendorfer, Sebastian T1 - Effect of the fractured calcaneus's peripheral fragment displacement on the triceps surae function JF - ЖУРНАЛ «ТРАВМА» Ukrainian Trauma Journal Y1 - 2015 VL - 2, TOM 16 ER - TY - CHAP A1 - Aurbach, Maximilian A1 - Wagner, Kilian A1 - Süß, Franz A1 - Dendorfer, Sebastian ED - Badnjevic, Almir T1 - Implementation and Validation of Human Kinematics Measured Using IMUs for Musculoskeletal Simulations by the Evaluation of Joint Reaction Forces T2 - CMBEBIH 2017, Proceedings of the International Conference on Medical and Biological Engineering 2017, Sarajevo, Bosnia and Herzegovina N2 - The gold standard for the analysis of human kinematics and kinetics is a camera-based motion capture system in combination with force measurement platforms. Alternatively, inertial measurement units can be utilized to obtain human kinematics, while ground reaction forces are computed from full body dynamics. This setup represents a system independent from the spatial confinement of a gait laboratory. The aim of this study is the comparison of the two methods by the investigation of lower limb kinematics and the resulting joint reaction forces within the ankle-, knee- and hip joints. For this purpose, human motion during gait was captured simultaneously by both measurement techniques. 13 trials from 8 different test subjects were evaluated in total. IMU data was processed with a quaternion based Kalman Filter. The data sets were implemented into a musculoskeletal simulation program in order to drive a virtual human body model. Each sensor was aligned to the gravitational and magnetic field vectors of the earth. The angles of flexions, extensions and rotations were analyzed to determine kinematic differences. Joint reaction forces defined kinetic dissimilarities. The overall kinematic differences of both models yielded root mean square errors of 7.62°, 6.02°, 4.95°, 2.79°, 2.38° and 3.56° for ankle flexion, subtalar eversion, knee flexion, hip external rotation, hip abduction and hip flexion, respectively. The proximo-distal differences in force peaks between the models yielded overall for the ankle, 57.33 %Bodyweight(BW) ± 46.86 %BW (16.66 %(Maximum peak to peak) ± 13.62 %) for the knee 37.09 %BW ± 29.33 %BW (17.65 % ± 15.44 %) and 32.03 %BW ± 24.33 %BW (15.6 % ± 12.54 %) for the hip. The overall outcome of this work investigated an approach independent of the common setup of the gait laboratory, thus enabling a cheaper and more flexible technology as an alternative. However, kinematic and thus kinetic differences remain rather large. Future work aims to improve the contact criterion for the calculation of the ground reaction forces and the implementation of a full-body calibration algorithm for the IMU system in order to counteract magnetic field disturbances. KW - Inertial Measurement Units KW - Multibody Simulation KW - Musculoskeletal Simulation KW - AnyBody KW - Motion Capture KW - Bewegungsapparat KW - Biomechanik KW - Motion Capturing KW - Mehrkörpersimulation KW - Ground Reaction Force Prediction KW - Gait KW - IMU KW - Joint Reaction Forces Y1 - 2017 U6 - https://doi.org/10.1007/978-981-10-4166-2_31 VL - Vol. 62 SP - 205 EP - 211 PB - Springer CY - Singapore ER - TY - JOUR A1 - De Pieri, Enrico A1 - Atzori, Federica A1 - Ferguson, Stephen J. A1 - Dendorfer, Sebastian A1 - Leunig, Michael A1 - Aepli, Martin T1 - Contact force path in total hip arthroplasty: effect of cup medialisation in a whole-body simulation JF - HIP International N2 - Background: Cup medialisation down to the true acetabular floor in total hip arthroplasty with a compensatory femoral offset increase seems to be mechanically advantageous for the abductor muscles due to the relocation of the lever arms (body weight lever arm decreased, abductor lever arm increased). However, limited information is currently available about the effects of this reconstruction type at the head cup interface, compared to an anatomical reconstruction that maintains the natural lever arms. Through a whole-body simulation analysis, we compared medialised versus anatomical reconstruction in THA to analyse the effects on: (1) contact force magnitude at the head cup interface; (2) contact force path in the cup; and (3) abductor activity. Methods: Musculoskeletal simulations were performed to calculate the above-mentioned parameters using inverse dynamics analysis. The differences between the virtually implanted THAs were calculated to compare the medialised versus anatomical reconstruction. Results: Cup medialisation with compensatory femoral offset increase led to: (1) a reduction in contact force magnitude at the head cup interface up to 6.6%; (2) a similar contact force path in the cup in terms of sliding distance and aspect ratio; and (3) a reduction in abductor activity up to 17.2% (gluteus medius). Conclusions: In our opinion, these potential biomechanical gains do not generally justify a fully medialised reconstruction, especially in younger patients that are more likely to undergo revision surgery in their lifetime. Cup medialisation should be performed until sufficient press fit and bony coverage of a properly sized and oriented cup can be achieved. KW - Cup medialisation KW - femoral offset KW - hip contact force KW - total hip anthroplasty KW - total hip replacement KW - Hüftgelenkprothese KW - Kontaktkraft KW - Biomechanische Analyse KW - Simulation Y1 - 2020 U6 - https://doi.org/10.1177/1120700020917321 VL - 31 IS - 5 SP - 624 EP - 631 PB - Sage 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 - JOUR A1 - Renkawitz, Tobias A1 - Dendorfer, Sebastian T1 - Orthopedic navigation technology and biomechanical evaluation for total hip replacement JF - Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine KW - Hüftgelenkprothese KW - Orthopädische Chirurgie KW - Computerunterstütztes Verfahren KW - Biomechanische Analyse Y1 - 2012 U6 - https://doi.org/10.1177/0954411912458746 VL - 226 IS - 12 SP - 897 EP - 898 ER - TY - CHAP A1 - Weber, Tim A1 - Stezowski, P. A1 - Dullien, Silvia A1 - Dendorfer, Sebastian T1 - Eine biomechanische Bewertung verschiedener Belastungsszenarios nach der Implantierung einer Hüft-Totalendoprothese T2 - 89. Jahrestagung der Vereinigung der Bayerischen Chirurgen e.V., 25. - 27. Juli 2012, Regensburg T2 - A biomechanical evaluation of different load scenarios after implantation of a total hip replacement Y1 - 2012 ER - TY - CHAP A1 - Weber, Tim A1 - Dendorfer, Sebastian A1 - Renkawitz, Tobias A1 - Dullien, Silvia A1 - Grifka, Joachim T1 - Clinical gait analysis combined with musculoskeletal modelling – coding a new generation of evaluation instruments T2 - Deutsche Gesellschaft für Biomechanik, Murnau, 2011 Y1 - 2011 ER - TY - CHAP A1 - Pilling, A. A1 - Süß, Franz A1 - Kubowitsch, Simone A1 - Dendorfer, Sebastian T1 - Experimental workflow for determining psychological stress from physiological biosignals T2 - Jahrestagung der BIOMEDIZINISCHEN TECHNIK und Dreiländertagung der MEDIZINISCHEN PHYSIK, Dresden, Germany, 2017 Y1 - 2017 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 - CHAP A1 - Weber, Tim A1 - Dendorfer, Sebastian A1 - Grifka, Joachim A1 - Weber, Markus A1 - Wörner, Michael A1 - Dullien, Silvia A1 - Verkerke, Gijsbertus Jacob A1 - Renkawitz, Tobias T1 - Verbessert die computerassistierte Femur First Operationstechnik für die Hüftendoprothetik den muskuloskelettalen Lastfall auf das Hüftgelenk? T2 - DKOU 2015, Deutscher Kongress für Orthopädie und Unfallchirurgie 2015 Y1 - 2015 UR - https://www.researchgate.net/publication/283259007_Verbessert_die_computerassistierte_Femur_First_Operationstechnik_fur_die_Huftendoprothetik_den_muskuloskelettalen_Lastfall_auf_das_Huftgelenk ER - TY - CHAP A1 - Weber, Tim A1 - Renkawitz, Tobias A1 - Grifka, Joachim A1 - Bulstra, Sjoerd K. A1 - Verkerke, Gijsbertus Jacob A1 - Dendorfer, Sebastian T1 - The musculoskeletal load scenario of computer-assisted Femur-First THR up to one year after surgery T2 - VI International Conference on Computational Bioengineering, Barcelona, Sept. 2015 Y1 - 2015 UR - https://www.researchgate.net/publication/281745827_The_musculoskeletal_load_scenario_of_computer-assisted_Femur-First_THR_up_to_one_year_after_surgery ER - TY - CHAP A1 - Gross, Simon A1 - Süß, Franz A1 - Verkerke, Gijsbertus Jacob A1 - Dendorfer, Sebastian T1 - Simulating fatigue in musculoskeletal models using surface electromyography, ECCOMAS Congress, Crete, Greece, 201 T2 - ECCOMAS Congress, Crete, Greece, 2016 Y1 - 2016 ER - TY - CHAP A1 - Süß, Franz A1 - Kubowitsch, Simone A1 - Verkerke, Gijsbertus Jacob A1 - Dendorfer, Sebastian T1 - The influence of stress on spinal loading T2 - ESEM webconference, Dez. 2017 Y1 - 2016 ER - TY - CHAP A1 - Dendorfer, Sebastian A1 - Kubowitsch, Simone T1 - The interaction of mental stress and biomechanics T2 - Health Technology Triangle, Weiden, 2016 Y1 - 2016 ER - TY - CHAP A1 - Al-Munajjed, Amir Andreas A1 - Nolte, Daniel A1 - Rasmussen, John A1 - Dendorfer, Sebastian T1 - Force distribution in the foot during braking – a musculoskeletal approach T2 - Human Modeling Symposium 2014, Munich, Germany N2 - High loads can appear in the individual joints of the human foot while the driver uses the pedals, in particular, during breaking. Measuring these internal forces is very difficult or almost impossible; therefore, advanced models are necessary to perform musculoskeletal simulations. The objective of this investigation was to see what loads are acting in the individual foot joints from the phalanges to calcaneus and talus during different brake scenarios. The Glasgow-Maastricht AnyBody Foot Model with 26 separate segments, connected by joints, ligaments and muscles was used inside the AnyBody Modeling System to compute individual mid foot joint loads. The amount, the direction of the force and additionally also the load insertion point was varied for several simulations. Figure 1: Seated musculoskeletal body model with applied brake force and forces for the lateral, intermediate and medial cuneiform-navicular joint for two different brake forces. The simulation showed that for the different brake scenarios, different muscles will be activated in the human and therefore different loads are apply in the fore-and mid-foot, respectively. The torso of the subject was assumed to be fixed in the seat. Further studies are ongoing to simulate the seat as an elastic element that allows different H-point locations according to the different loadings in the foot from the brake pedal using a new inverse dynamics analysis method called force-dependent kinematics. Y1 - 2014 UR - https://www.researchgate.net/publication/281229902_Force_distribution_in_the_foot_during_braking_-a_musculoskeletal_approach 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 - CHAP A1 - Weber, Tim A1 - Dendorfer, Sebastian A1 - Bulstra, Sjoerd K. A1 - Verkerke, Gijsbertus Jacob A1 - Renkawitz, Tobias T1 - Biomechanical Outcome after computer-assisted vs. Conventional THR T2 - ANSYS Conference & 32th CADFEM Users' Meeting 2014, 04.-06. Juni, Nürnberg Y1 - 2014 UR - https://www.researchgate.net/publication/264547774_Biomechanical_outcome_after_computer-assisted_vs_conventional_THR ER - TY - CHAP A1 - Dendorfer, Sebastian T1 - Virtuelle Menschmodelle – von der Bewegung zur Belastung T2 - Medbo Bezirksklinikum Regensburg, April 2016 Y1 - 2016 ER - TY - CHAP A1 - Dendorfer, Sebastian T1 - Biomechanik des Alterns T2 - Kolpingfortbildung Lambach, April 2016 Y1 - 2016 ER - TY - CHAP A1 - Gross, Simon A1 - Verkerke, Gijsbertus Jacob A1 - Dendorfer, Sebastian T1 - Combined Experimental and Numerical Approach to Investigate Changes in Muscle Recruitment Pattern of the Back Muscles during Exhausting Exercise T2 - World Congress Biomechanics Dublin, 2018 N2 - In recent years, musculoskeletal computation has become a widely used tool to investigate joint and muscle forces within the human body. However, the issue of muscle fatigue is not considered adequately in most models and is a challenging task. One aspect that needs to be examined is the interaction of muscles during an exhausting task. Therefore, an experimental study was designed to analyze the changes of back muscle recruitment pattern during such exercises. In this study 38 subjects (27 male, 11 female, height = 177±8.5 cm, weight = 74.0±13.6 kg) participated. Each subject had to perform three static and three dynamic exhausting exercises where the back muscles were loaded with subject specific forces using a dynamometer adapter especially designed for the trunk muscles. To collect the muscle activity, twelve surface electromyography sensors were applied on the back, and four on the abdominal muscles. Muscle activity and fatigue were analyzed by calculating the maximum voluntary contraction normalized signal and the median frequency. At first the fatigue of m. erector spinae and m. multifidi was analyzed, since these muscles carry the main load during the exercises. Subsequently the activity of the m. trapezius, m. rectus abdominis and m. obliquus externus were investigated to determine recruitment patterns. To gain more detailed information of these patterns a numerical model was built using the AnyBody Modeling System™. Analyzing the measurements, we can observe an increasing muscle activity during isokinetic exercises while the force is constant. Since the activity in the simulation is defined as the current force output divided by the strength of the muscle, the strength parameter was scaled down based on the measured data, assuming a linear force – activity correlation, and using a numerical algorithm considering the influence of cross talk. The results show, that changes in recruitment pattern can be divided into three major subgroups. Prior to total exhaustion, some of the subjects show additional activation of muscles in the trapezius region, while other subjects show an additional activation of abdominal muscles, increasing the intra-abdominal pressure which supports the spine. In the third group an activation in both regions can be observed. The numerical simulations show an increasing activity of abdominal muscles as well as muscles in the upper back. Especially the m. latissimus dorsi shows a significantly higher activity. The results lead to the conclusion that prior to total exhaustion, additional muscles are recruited to support the main muscles. It was shown that abdominal muscles are activated to support back muscles by pressurizing the trunk cavity to delay total exhaustion as long as possible. In conclusion, the results show that changes in muscle recruitment pattern need to be considered when introducing muscle fatigue to musculoskeletal models. Y1 - 2018 ER -