TY - JOUR A1 - Lenich, Andreas A1 - Bachmeier, S. A1 - Dendorfer, Sebastian A1 - Mayr, E. A1 - Nerlich, Michael A1 - Füchtmeier, Bernd T1 - Development of a test system to analyze different hip fracture osteosyntheses under simulated walking JF - Biomedizinische Technik. Biomedical engineering N2 - The mechanical complications of osteosyntheses after hip fractures are previously investigated by mostly static or dynamic uniaxial loading test systems. However, the physiologic loading of the hip joint during a normal gait is a multiplanar, dynamic movement. Therefore, we constructed a system to test osteosyntheses for hip fractures under physiologic multiplanar loading representative of normal gait. To evaluate the testing system, 12 femora pairs were tested under 25,000 cycles with two standard osteosyntheses (Proximal Femoral Nail Antirotation/Gamma3 Nail). For angular movement, the varus collapse to cut out (∝CO) (∝CO=4.8°±2.1° for blade and ∝CO=7.8°±3.8° for screw) was the dominant failure mode, and only slight rotational angle shifts (∝Rot) (∝Rot=1.7°±0.4° for blade and ∝Rot=2.4°±0.3° for screw) of the femoral head around the implant axis were observed. Angular displacements in varus direction and rotation were higher in specimens reinforced with screws. Hence, the cut out model and the migration directions showed a distinction between helical blade and hip screw. However, there were no significant differences between the different implants. The new setup is able to create clinical failures and allows to give evidence about the anchorage stability of different implant types under dynamic gait motion pattern. KW - biomechanical implant test KW - dynamic multiplanar loading KW - hip fractureg KW - implant migration KW - patient specific loading KW - Hüftgelenk KW - Knochenbruch KW - Osteosynthese KW - Bewegungsanalyse KW - Simulation Y1 - 2012 U6 - https://doi.org/10.1515/bmt-2011-0999 VL - 57 IS - 2 SP - 113 EP - 119 ER - TY - JOUR A1 - Weber, Tim A. A1 - Dendorfer, Sebastian A1 - Grifka, Joachim A1 - Verkerke, Gijsbertus Jacob A1 - Renkawitz, Tobias ED - Takagi, Michiaki T1 - Does Computer-Assisted Femur First THR Improve Musculoskeletal Loading Conditions? JF - BioMed Research International N2 - We have developed a novel, computer-assisted operation method for minimal-invasive total hip replacement (THR) following the concept of “femur first/combined anteversion,” which incorporates various aspects of performing a functional optimization of the prosthetic stem and cup position (CAS FF). The purpose of this study is to assess whether the hip joint reaction forces and patient’s gait parameters are being improved by CAS FF in relation to conventional THR (CON). We enrolled 60 patients (28 CAS FF/32 CON) and invited them for gait analysis at three time points (preoperatively, postop six months, and postop 12 months). Data retrieved from gait analysis was processed using patient-specific musculoskeletal models. The target parameters were hip reaction force magnitude (hrf), symmetries, and orientation with respect to the cup. Hrf in the CAS FF group were closer to a young healthy normal. Phase-shift symmetry showed an increase in the CAS FF group. Hrf orientation in the CAS FF group was closer to optimum, though no edge or rim-loading occurred in the CON group as well. The CAS FF group showed an improved hrf orientation in an early stage and a trend to an improved long-term outcome. KW - Hüftgelenkprothese KW - Operationstechnik KW - Computerunterstütztes Verfahren KW - Bewegungsapparat KW - Mechanische Belastung Y1 - 2015 U6 - https://doi.org/10.1155/2015/625317 VL - 2015 SP - ID 625317 ER - TY - JOUR A1 - Pfeifer, Christian A1 - Müller, Michael A1 - Prantl, Lukas A1 - Berner, Arne A1 - Dendorfer, Sebastian A1 - Englert, Carsten T1 - Cartilage labelling for mechanical testing in T-peel configuration JF - International Orthopaedics N2 - PURPOSE: The purpose of this study was to find a suitable method of labelling cartilage samples for the measurement of distraction distances in biomechanical testing. METHODS: Samples of bovine cartilage were labelled using five different methods: hydroquinone and silver nitrate (AgNO3), potassium permanganate (KMnO4) with sodium thiosulphate (Na2S2O3), India ink, heat, and laser energy. After the labelling, we analysed the cartilage samples with regard to cytotoxity by histochemical staining with ethidiumbromide homodimer (EthD-1) and calcein AM. Furthermore, we tested cartilages labelled with India ink and heat in a T-peel test configuration to analyse possible changes in the mechanical behaviour between marked and unlabelled samples. RESULTS: Only the labelling methods with Indian ink or a heated needle showed acceptable results in the cytotoxity test with regard to labelling persistence, accuracy, and the influence on consistency and viability of the chondrocytes. In the biomechanical T-peel configuration, heat-labelled samples collapsed significantly earlier than unlabelled samples. CONCLUSION: Labelling bovine cartilage samples with Indian ink in biomechanical testing is a reliable, accurate, inexpensive, and easy-to-perform method. This labelling method influenced neither the biomechanical behaviour nor the viability of the tissue compared to untreated bovine cartilage. KW - Bovine cartilage KW - Cartilage samples KW - Indian ink KW - T-peel configuration KW - Method labeling KW - Knorpel KW - Rind KW - Kennzeichnung KW - Tinte KW - Biomechanik KW - Prüfung Y1 - 2012 U6 - https://doi.org/10.1007/s00264-011-1468-3 VL - 36 IS - 7 SP - 1493 EP - 1499 PB - Springer 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 - Roldán, J.C. A1 - Moralis, A. A1 - Dendorfer, Sebastian A1 - Witte, J. A1 - Reicheneder, C. T1 - Controlled central advancement of the midface after Le Fort III osteotomy by a 3-point skeletal anchorage JF - The Journal of craniofacial surgery N2 - A 3-point skeletal anchorage with taping screws for distraction osteogenesis after a Le Fort III osteotomy was applied for the first time in a severely mentally impaired patient where intraoral devices had to be avoided. All 3-force application points included the center of resistance, which allowed an optimal control on the resulting moment. A novel device for skeletal long-term retention into the nasal dorsum prevented a relapse, whereas adjustment of the midface position was observed. Fusioned three-dimensional computed tomography analysis revealed real movements not accessible by a conventional cephalometry. KW - Mund-Kiefer-Gesichts-Chirurgie KW - Le Fort III KW - distraction KW - vector KW - anchorage KW - three-dimensional computed tomography analysis KW - Distraktion KW - Knochenbildung KW - Osteotomie KW - Dreidimensionale Bildverarbeitung KW - Computertomografie Y1 - 2011 U6 - https://doi.org/10.1097/SCS.0b013e318231fc8d VL - 22 IS - 6 SP - 2384 EP - 2386 ER - TY - CHAP A1 - Dendorfer, Sebastian A1 - Maier, Hans Jürgen A1 - Hammer, Josef T1 - How do age and anisotropy affect the fatigue behaviour of cancellous bone? T2 - Medicine Meets Engineering N2 - The fatigue behaviour of materials is of particular interest for the failure prediction of materials and structures exposed to cyclic loading. For trabecular bone structures only a few sets of lifetime data have been reported in the literature and structural measures are commonly not considered. The influence of load contributions not aligned with the main physiological axis remains unclear. Furthermore age effects on the fatigue behaviour are not well described. In the present study, different groups of human vertebral cancellous bone were exposed to cyclic compression. The inital modulus and therefore lifetimes were found to be highly dependent on age. The decrease in both with increasing age was much more pronounced in specimens which were not aligned with the main physiological axis. This implies that old bone is much more sensitive to (cyclic) failure loads in general but particularly to loads which are not coincident with the physiological main axis. KW - Knochenbruch KW - Spongiosa KW - Alter KW - Anisotropie Y1 - 2008 SP - 68 EP - 74 PB - IOS Press ER - TY - GEN A1 - Auer, Simon A1 - Reinker, Lukas A1 - Süß, Franz A1 - Dendorfer, Sebastian T1 - Comparing calculated and measured muscle activity of thigh muscles in dynamic motion. T2 - 27th Congress of the European Society of Biomechanics, 26 - 29 June 2022, Porto, Portugal Y1 - 2022 UR - https://drive.google.com/uc?id=1RBguxyHZE-Wr2y6ktOWK06_3lQg2M9Rb&export=download&confirm=t SP - 640 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 - Morag, Sarah A1 - Kieninger, Martin A1 - Eissnert, Christoph A1 - Auer, Simon A1 - Dendorfer, Sebastian A1 - Popp, Daniel A1 - Hoffmann, Johannes A1 - Kieninger, Bärbel T1 - Comparison of different techniques for prehospital cervical spine immobilization: Biomechanical measurements with a wireless motion capture system JF - PLOS ONE Y1 - 2023 U6 - https://doi.org/10.1371/journal.pone.0292300 VL - 18 IS - 11 SP - 1 EP - 14 PB - PLOS CY - San Francisco, California 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 -