TY - CHAP A1 - Weiß, Roman A1 - Großmann, Benjamin A1 - Leibold, Marion A1 - Schlegl, Thomas A1 - Wollherr, Dirk A1 - Weiss, Roman A1 - Grossmann, Benjamin T1 - Modeling and nonlinear control of antagonistically actuating pneumatic artificial muscles T2 - 2017 IEEE International Conference on Advanced Intelligent Mechatronics (AIM), 3-7 July 2017, Munich, Germany N2 - This paper discusses modeling and nonlinear control of a joint antagonistically actuated by two pneumatic, artificial muscles. A single model of the whole system is obtained by a combined physical and phenomenological modeling approach. The combined model for the joint, the muscles and the proportional valves results in a nonlinear, affine-in-control system description. The model is used to derive control laws for an input/output linearization approach to linearize the plant. Modeling and parametrization errors are covered via an outer control loop consisting of a state-feedback which is extended by an additional feedback of error integral. Extensive experimental results show the quality of the model and the performance of the respective control laws. KW - FORCE KW - Muscles KW - Pulleys KW - Robot sensing systems KW - Transfer functions KW - Valves Y1 - 2017 U6 - https://doi.org/10.1109/AIM.2017.8014001 SP - 94 EP - 99 PB - IEEE ER - TY - THES A1 - Putzer, Michael T1 - Development of subject-specific musculoskeletal models for studies of lumbar loading N2 - Anatomical differences between individuals are often neglected in musculoskeletal models, but they are necessary in case of subject-specific questions regarding the lumbar spine. A modification of models to each subject is complex and the effects on lumbar loading are difficult to assess. One objective of this work is to create a validated musculoskeletal human model, which facilitates a subject-specific modification of the lumbar geometry. In a second step, important parameters are identified in sensitivity studies and at last, a case study regarding multifidus muscle atrophy after a disc herniation is conducted. The results of the studies indicate that lumbar motion and loading is dependent on lumbar ligament stiffness. Furthermore, subject-specific modelling of the lumbar spine should include at least the vertebral height, disc height and lumbar lordosis. The results of the case study suggest that an overloading of the multifidus muscle could follow disc herniation. Additionally, a subsequent atrophy of the muscles could expose adjacent levels to an increased loading, but these findings are highly dependent on the individual. KW - ligaments KW - lumbar geometry KW - lumbar spine KW - multifidus KW - musculoskeletal simulation KW - sensitivity study Y1 - 2019 SN - 978-3-8440-6695-1 U6 - https://doi.org/10.2370/9783844066951 N1 - Kooperative Promotion an der Universität der Bundeswehr München und an der OTH Regensburg PB - Shaker Verlag CY - Düren ER - TY - JOUR A1 - Hoenicka, Markus A1 - Kaspar, Marcel A1 - Schmid, Christof A1 - Liebold, Andreas A1 - Schrammel, Siegfried T1 - Contact-free monitoring of vessel graft stiffness - proof of concept as a tool for vascular tissue engineering JF - Journal of tissue engineering and regenerative medicine N2 - Tissue-engineered vessel grafts have to mimic the biomechanical properties of native blood vessels. Manufacturing processes often condition grafts to adapt them to the target flow conditions. Graft stiffness is influenced by material properties and dimensions and determines graft compliance. This proof-of-concept study evaluated a contact-free method to monitor biomechanical properties without compromising sterility. Forced vibration response analysis was performed on human umbilical vein (HUV) segments mounted in a buffer-filled tubing system. A linear motor and a dynamic signal analyser were used to excite the fluid by white noise (0-200 Hz). Vein responses were read out by laser triangulation and analysed by fast Fourier transformation. Modal analysis was performed by monitoring multiple positions of the vessel surface. As an inverse model of graft stiffening during conditioning, HUV were digested proteolytically, and the course of natural frequencies (NFs) was monitored over 120 min. Human umbilical vein showed up to five modes with NFs in the range of 5-100 Hz. The first natural frequencies of HUV did not alter over time while incubated in buffer (p = 0.555), whereas both collagenase (-35%, p = 0.0061) and elastase (-45%, p < 0.001) treatments caused significant decreases of NF within 120 min. Decellularized HUV showed similar results, indicating that changes of the extracellular matrix were responsible for the observed shift in NF. Performing vibration response analysis on vessel grafts is feasible without compromising sterility or integrity of the samples. This technique allows direct measurement of stiffness as an important biomechanical property, obviating the need to monitor surrogate parameters. Copyright (C) 2016 John Wiley & Sons, Ltd. KW - ANEURYSMS KW - ARTERIES KW - Biomechanics KW - BIOREACTOR KW - BLOOD-VESSELS KW - BYPASS GRAFTS KW - CONSTRUCTS KW - design KW - extracellular matrix KW - human umbilical vein KW - IN-VITRO KW - MECHANICAL-PROPERTIES KW - proteolysis KW - small calibre graft KW - vascular tissue engineering Y1 - 2017 U6 - https://doi.org/10.1002/term.2186 VL - 11 IS - 10 SP - 2828 EP - 2835 PB - Wiley ER - TY - JOUR A1 - Sellmer, Andreas A1 - Stangl, Hubert A1 - Beyer, Mandy A1 - Grünstein, Elisabeth A1 - Leonhardt, Michel A1 - Pongratz, Herwig A1 - Eichhorn, Emerich A1 - Elz, Sigurd A1 - Striegl, Birgit A1 - Jenei-Lanzl, Zsuzsa A1 - Dove, Stefan A1 - Straub, Rainer H. A1 - Krämer, Oliver H. A1 - Mahboobi, Siavosh T1 - Marbostat-100 Defines a New Class of Potent and Selective Antiinflammatory and Antirheumatic Histone Deacetylase 6 Inhibitors JF - Journal of medicinal chemistry N2 - Epigenetic modifiers of the histone deacetylase (HDAC) family contribute to autoimmunity, cancer, HIV infection, inflammation, and neurodegeneration. Hence, histone deacetylase inhibitors (HDACi), which alter protein acetylation, gene expression patterns, and cell fate decisions, represent promising new drugs for the therapy of these diseases. Whereas pan-HDACi inhibit all 11 Zn2+-dependent histone deacetylases (HDACs) and cause a broad spectrum of side effects, specific inhibitors of histone deacetylase 6 (HDAC6i) are supposed to have less side effects. We present the synthesis and biological evaluation of Marbostats, novel HDAC6i that contain the hydroxamic acid moiety linked to tetrahydro-β-carboline derivatives. Our lead compound Marbostat-100 is a more potent and more selective HDAC6i than previously established well-characterized compounds in vitro as well as in cells. Moreover, Marbostat-100 is well tolerated by mice and effective against collagen type II induced arthritis. Thus, Marbostat-100 represents a most selective known HDAC6i and the possibility for clinical evaluation of a HDAC isoform-specific drug. KW - Animals KW - anti-Inflammatory agent KW - chemical synthesis KW - pharmacology KW - therapeutic use KW - toxicity Y1 - 2018 U6 - https://doi.org/10.1021/acs.jmedchem.7b01593 VL - 61 IS - 8 SP - 3454 EP - 3477 PB - ACS Publications ER - TY - JOUR A1 - Kummerlin, Jana A1 - Fabro, Hannah Katharina A1 - Pedersen, Peter Heide A1 - Jensen, Kenneth Krogh A1 - Pedersen, Dennis A1 - Andersen, Michael Skipper T1 - Measuring Knee Joint Laxity in Three Degrees-of-Freedom In Vivo Using a Robotics- and Image-Based Technology JF - Journal of Biomechanical Engineering N2 - Accurate and reliable information about three-dimensional (3D) knee joint laxity can prevent misdiagnosis and avoid incorrect treatments. Nevertheless, knee laxity assessments presented in the literature suffer from significant drawbacks such as soft tissue artifacts, restricting the knee within the measurement, and the absence of quantitative knee ligament property information. In this study, we demonstrated the applicability of a novel methodology for measuring 3D knee laxity, combining robotics- and image-based technology. As such technology has never been applied to healthy living subjects, the aims of this study were to develop novel technology to measure 3D knee laxity in vivo and to provide proof-of-concept 3D knee laxity measurements. To measure tibiofemoral movements, four healthy subjects were placed on a custom-built arthrometer located inside a low dose biplanar X-ray system with an approximately 60 deg knee flexion angle. Anteroposterior and mediolateral translation as well as internal and external rotation loads were subsequently applied to the unconstrained leg, which was placed inside a pneumatic cast boot. Bone contours were segmented in the obtained X-rays, to which subject-specific bone geometries from magnetic resonance imaging (MRI) scans were registered. Afterward, tibiofemoral poses were computed. Measurements of primary and secondary laxity revealed considerable interpersonal differences. The method differs from those available by the ability to accurately track secondary laxity of the unrestricted knee and to apply coupled forces in multiple planes. Our methodology can provide reliable information for academic knee ligament research as well as for clinical diagnostics in the future. KW - ANTERIOR CRUCIATE LIGAMENT KW - COMPLEX KW - COORDINATE SYSTEM KW - INJURY KW - INSTABILITY KW - MOTION KW - OSTEOARTHRITIS KW - QUANTIFICATION KW - STIFFNESS Y1 - 2022 U6 - https://doi.org/10.1115/1.4053792 SN - 1528-8951 VL - 144 IS - 8 PB - The American Society of Mechanical Engineers (ASME) ER - TY - JOUR A1 - Baldwin, Andrew A1 - Hartl, Maximilian A1 - Tschaikowsky, Mathaeus A1 - Balzer, Bizan N. A1 - Booth, Brian W. T1 - Degradation and release of tannic acid from an injectable tissue regeneration bead matrix in vivo JF - Journal of biomedical materials research, part B - Applied Biomaterials N2 - The development of multifunctional biomaterials as both tissue regeneration and drug delivery devices is currently a major focus in biomedical research. Tannic Acid (TA), a naturally occurring plant polyphenol, displays unique medicinal abilities as an antioxidant, an antibiotic, and as an anticancer agent. TA has applications in biomaterials acting as a crosslinker in polymer hydrogels improving thermal stability and mechanical properties. We have developed injectable cell seeded collagen beads crosslinked with TA for breast reconstruction and anticancer activity following lumpectomy. This study determined the longevity of the bead implants by establishing a degradation time line and TA release profile in vivo. Beads crosslinked with 0.1% TA and 1% TA were compared to observe the differences in TA concentration on degradation and release. We found collagen/TA beads degrade at similar rates in vivo, yet are resistant to complete degradation after 16 weeks. TA is released over time in vivo through diffusion and cellular activity. Changes in mechanical properties in collagen/TA beads before implantation to after 8 weeks in vivo also indicate loss of TA over a longer period of time. Elastic moduli decreased uniformly in both 0.1% and 1% TA beads. This study establishes that collagen/TA materials can act as a drug delivery system, rapidly releasing TA within the first week following implantation. However, the beads retain TA long term allowing them to resist degradation and remain in situ acting as a cell scaffold and tissue filler. This confirms its potential use as an anticancer and minimally invasive breast reconstructive device following lumpectomy. KW - Antioxidant KW - APOPTOSIS KW - biomaterial KW - cancer KW - Cancer-cells KW - collagen KW - EARLY OSTEOARTHRITIS KW - HYDROGELS KW - IMMEDIATE BREAST RECONSTRUCTION KW - MECHANICAL PROPERTIES KW - MEDICINAL PLANTS KW - POLYPHENOLS KW - tannic acid KW - tissue regeneration Y1 - 2021 U6 - https://doi.org/10.1002/jbm.b.34990 SN - 1552-4981 VL - 110 IS - 5 SP - 1165 EP - 1177 PB - Wiley ER - TY - JOUR A1 - Chatterjee, Subhomoy A1 - Kobylinski, Sabine A1 - Basu, Bikramjit T1 - Finite Element Analysis to Probe the Influence of Acetabular Shell Design, Liner Material, and Subject Parameters on Biomechanical Response in Periprosthetic Bone JF - Journal of Biomechanical Engineering N2 - The implant stability and biomechanical response of periprosthetic bone in acetabulum around total hip joint replacement (THR) devices depend on a host of parameters, including design of articulating materials, gait cycle and subject parameters. In this study, the impact of shell design (conventional, finned, spiked, and combined design) and liner material on the biomechanical response of periprosthetic bone has been analyzed using finite element (FE) method. Two different liner materials: high density polyethylene-20% hydroxyapatite-20% alumina (HDPE-20%HA-20%Al2O3) and highly cross-linked ultrahigh molecular weight polyethylene (HC-UHMWPE) were used. The subject parameters included bone condition and bodyweight. Physiologically relevant load cases of a gait cycle were considered. The deviation of mechanical condition of the periprosthetic bone due to implantation was least for the finned shell design. No significant deviation was observed at the bone region adjacent to the spikes and the fins. This study recommends the use of the finned design, particularly for weaker bone conditions. For stronger bones, the combined design may also be recommended for higher stability. The use of HC-UHMWPE liner was found to be better for convensional shell design. However, similar biomechanical response was captured in our FE analysis for both the liner materials in case of other shell designs. Overall, the study establishes the biomechanical response of periprosthetic bone in the acetabular with preclinically tested liner materials together with new shell design for different subject conditions. KW - Acetabulum/physiology KW - Biomechanical Phenomena KW - Body Weight KW - Finite element analysis KW - GAIT KW - Hip Prosthesis KW - Humans KW - Linear Models KW - Mechanical Phenomena KW - Prosthesis Design KW - Stress, Mechanical Y1 - 2018 U6 - https://doi.org/10.1115/1.4040249 SN - 1528-8951 VL - 140 IS - 10 PB - ASME ER - TY - CHAP A1 - Geith, Markus A. A1 - Wagner, Marcus T1 - Numerical Analysis Of Stent Delivery Systems During Pre- And Intraoperative Processes T2 - Deutsches LS-DYNA Forum 2018, Bamberg Y1 - 2018 ER - TY - JOUR A1 - Schmidt, Ulf A1 - Penzkofer, Rainer A1 - Bachmaier, Samuel A1 - Augat, Peter T1 - Implant Material and Design Alter Construct Stiffness in Distal Femur Locking Plate Fixation: A Pilot Study JF - Clinical Orthopaedics and Related Research® N2 - BACKGROUND: Construct stiffness affects healing of bones fixed with locking plates. However, variable construct stiffness reported in the literature may be attributable to differing test configurations and direct comparisons may clarify these differences. QUESTIONS/PURPOSES: We therefore asked whether different distal femur locking plate systems and constructs will lead to different (1) axial and rotational stiffness and (2) fatigue under cyclic loading. METHODS: We investigated four plate systems for distal femur fixation (AxSOS, LCP, PERI-LOC, POLYAX) of differing designs and materials using bone substitutes in a distal femur fracture model (OTA/AO 33-A3). We created six constructs of each of the four plating systems. Stiffness under static and cyclic loading and fatigue under cyclic loading were measured. RESULTS: Mean construct stiffness under axial loading was highest for AxSOS (100.8 N/mm) followed by PERI-LOC (80.8 N/mm) and LCP (62.6 N/mm). POLYAX construct stiffness testing showed the lowest stiffness (51.7 N/mm) with 50% stiffness of AxSOS construct testing. Mean construct stiffness under torsional loading was similar in the group of AxSOS and PERI-LOC (3.40 Nm/degree versus 3.15 Nm/degree) and in the group of LCP and POLYAX (2.63 Nm/degree versus 2.56 Nm/degree). The fourth load level of > 75,000 cycles was reached by three of six AxSOS, three of six POLYAX, and two of six PERI-LOC constructs. All others including all LCP constructs failed earlier. CONCLUSIONS: Implant design and material of new-generation distal femur locking plate systems leads to a wide range of differences in construct stiffness. CLINICAL RELEVANCE: Assuming construct stiffness affects fracture healing, these data may influence surgical decision-making in choosing an implant system. Y1 - 2013 U6 - https://doi.org/10.1007/s11999-013-2867-0 VL - 471 IS - 9 SP - 2808 EP - 2814 PB - The Association of Bone and Joint Surgeons ER - TY - CHAP A1 - Geith, Markus A. A1 - Sommer, Gerhard A1 - Schratzenstaller, Thomas A1 - Holzapfel, Gerhard A. T1 - First Approaches in Quantifying Acute Vascular Damage due to Stenting T2 - 23rd Congress of the European Society of Biomechanics, July 2-5,2017, Seville, Spain KW - Stent KW - Implantation KW - Gefäßverletzung Y1 - 2017 ER - TY - JOUR A1 - Geith, Markus A. A1 - Eckmann, Jakob D. A1 - Haspinger, Daniel Ch. A1 - Agrafiotis, Emmanouil A1 - Maier, Dominik A1 - Szabo, Patrick A1 - Sommer, Gerhard A1 - Schratzenstaller, Thomas A1 - Holzapfel, Gerhard A. T1 - Experimental and mathematical characterization of coronary polyamide-12 balloon catheter membranes JF - PLoS One N2 - The experimental quantification and modeling of the multiaxial mechanical response of polymer membranes of coronary balloon catheters have not yet been carried out. Due to the lack of insights, it is not shown whether isotropic material models can describe the material response of balloon catheter membranes expanded with nominal or higher, supra-nominal pressures. Therefore, for the first time, specimens of commercial polyamide-12 balloon catheters membranes were investigated during uniaxial and biaxial loading scenarios. Furthermore, the influence of kinematic effects on the material response was observed by comparing results from quasi-static and dynamic biaxial extension tests. Novel clamping techniques are described, which allow to test even tiny specimens taken from the balloon membranes. The results of this study reveal the semi-compliant, nonlinear, and viscoelastic character of polyamide-12 balloon catheter membranes. Above nominal pressure, the membranes show a pronounced anisotropic mechanical behavior with a stiffer response in the circumferential direction. The anisotropic feature intensifies with an increasing strain-rate. A modified polynomial model was applied to represent the realistic mechanical response of the balloon catheter membranes during dynamic biaxial extension tests. This study also includes a compact set of constitutive model parameters for the use of the proposed model in future finite element analyses to perform more accurate simulations of expanding balloon catheters. KW - Catheters KW - Anisotropy KW - Polymers KW - Viscoelasticity KW - Coronary stenting KW - Finite element analysis KW - Deformation KW - Adhesives Y1 - 2020 U6 - https://doi.org/10.1371/journal.pone.0234340 VL - 15 IS - 6 SP - 1 EP - 22 PB - PLOS ER - TY - JOUR A1 - Geith, Markus A. A1 - Swidergal, Krzysztof A1 - Hochholdinger, Bernd A1 - Schratzenstaller, Thomas A1 - Wagner, Marcus A1 - Holzapfel, Gerhard A. T1 - On the importance of modeling balloon folding, pleating, and stent crimping: An FE study comparing experimental inflation tests JF - International Journal for Numerical Methods in Biomedical Engineering N2 - Finite element (FE)–based studies of preoperative processes such as folding,pleating, and stent crimping with a comparison with experimental inflation tests are not yet available. Therefore, a novel workflow is presented in which residual stresses of balloon folding and pleating, as well as stent crimping, and the geometries of all contact partners were ultimately implemented in an FE code to simulate stent expansion by using an implicit solver. The numerical results demonstrate that the incorporation of residual stresses and strains experienced during the production step significantly increased the accuracy of the subsequent simulations, especially of the stent expansion model. During the preoperative processes, stresses inside the membrane and the stent material also reached a rather high level. Hence, there can be no presumption that balloon catheters or stents are undamaged before the actual surgery. The implementation of the realistic geometry, in particular the balloon tapers, and the blades of the process devices improved the simulation of the expansion mech-anisms, such as dogboning, concave bending, or overexpansion of stent cells. This study shows that implicit solvers are able to precisely simulate the mentioned preoperative processes and the stent expansion procedure without a preceding manipulation of the simulation time or physical mass. KW - Catheter KW - Coronary KW - Crimping KW - Finite element KW - Stent KW - Stent KW - Implantation KW - Simulation KW - Finite-Elemente-Methode Y1 - 2019 U6 - https://doi.org/10.1002/cnm.3249 N1 - This study was funded by the Bavarian Research Foundation within the project “PIZ‐225‐18” VL - 35 IS - 11 PB - Wiley 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 - 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 - 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 - 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 - TY - JOUR A1 - Hölscher, Thomas A1 - Weber, Tim A. A1 - Lazarev, Igor A1 - Englert, Carsten A1 - Dendorfer, Sebastian T1 - The influence of rotator cuff tears on glenohumeral stability during abduction tasks JF - Journal of Orthopaedic Research N2 - One of the main goals in reconstructing rotator cuff tears is the restoration of glenohumeral joint stability, which is subsequently of utmost importance in order to prevent degenerative damage such as superior labral anterior posterior (SLAP) lesion, arthrosis, and malfunction. The goal of the current study was to facilitate musculoskeletal models in order to estimate glenohumeral instability introduced by muscle weakness due to cuff lesions. Inverse dynamics simulations were used to compute joint reaction forces for several static abduction tasks with different muscle weakness. Results were compared with the existing literature in order to ensure the model validity. Further arm positions taken from activities of daily living, requiring the rotator cuff muscles were modeled and their contribution to joint kinetics computed. Weakness of the superior rotator cuff muscles (supraspinatus; infraspinatus) leads to a deviation of the joint reaction force to the cranial dorsal rim of the glenoid. Massive rotator cuff defects showed higher potential for glenohumeral instability in contrast to single muscle ruptures. The teres minor muscle seems to substitute lost joint torque during several simulated muscle tears to maintain joint stability. Joint instability increases with cuff tear size. Weakness of the upper part of the rotator cuff leads to a joint reaction force closer to the upper glenoid rim. This indicates the comorbidity of cuff tears with SLAP lesions. The teres minor is crucial for maintaining joint stability in case of massive cuff defects and should be uprated in clinical decision-making. KW - Abduction tasks KW - Glenohumeral stability KW - Musculoskeletal Modeling KW - Muscle weakness KW - Rotator cuff tears KW - Rotatorenmanschettenriss KW - Schultergelenk KW - Stabilität Y1 - 2016 U6 - https://doi.org/10.1002/jor.23161 VL - 34 IS - 9 SP - 1628 EP - 1635 ER - TY - CHAP A1 - Auer, Simon A1 - Kubowitsch, Simone A1 - Krutsch, Werner A1 - Renkawitz, Tobias A1 - Süß, Franz A1 - Dendorfer, Sebastian T1 - Effect of mental demand on knee forces in professional youth soccer players T2 - ISBS Proceedings Archive N2 - Soccer is one of the most popular sports all around the world. It is an injurious type of sport with a focus on lower extremities and high psychological pressure during matches. The stressor is linked with injuries and an increased musculoskeletal loading. This study investigates the influence of cognitive stress on the load profile of the knee joint. Twelve professional youth soccer players performed highly dynamic runs with and without additional cognitive stress. The runs were analysed with a musculoskeletal simulation software. The data analysis shows no difference in knee joint reaction loading under additional mental stress compared to the baseline. Yet running times are significantly lower in the baseline. While there is no increase in the joint loads, the running times indicate an altered movement behaviour when the subjects are exposed to additional mental demand. KW - Kniegelenk KW - Körperliche Belastung KW - Stress KW - Computersimulation Y1 - 2020 UR - https://commons.nmu.edu/isbs/vol38/iss1/28 VL - 38 IS - 1, Art. 28 ER - TY - JOUR A1 - Dendorfer, Sebastian T1 - Älterwerden muss auch mal wehtun! JF - Gesunde Hochschule, OTH Regensburg, 4.7.2016 Y1 - 2016 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 - Aurbach, Maximilian A1 - Špička, Jan A1 - Süß, Franz A1 - Vychytil, J. A1 - Havelková, Leonard A1 - Ryba, T. A1 - Dendorfer, Sebastian T1 - Torus obstacle method as a wrapping approach of the deltoid muscle group for humeral abduction in musculoskeletal simulation JF - Journal of Biomechanics N2 - Musculoskeletal models of the shoulder complex are valuable research aids to investigate tears of the supraspinatus and the resulting mechanical impact during abduction of the humerus. One of the major contributors to this motion is the deltoid muscle group and for this, an accurate modeling of the lines of action is indispensable. The aim of this work was to utilize a torus obstacle wrapping approach for the deltoids of an existing shoulder model and assess the feasibility of the approach during humeral abduction. The shoulder model from the AnyBody™ modeling system was used as a platform. The size of the tori is based on a magnetic resonance imaging (MRI) approach and several kinematic couplings are implemented to determine the trajectories of the tori during abduction. To assess the model behavior, the moment arms of the virtual muscle elements and the resultant glenohumeral joint reaction force (GHJF) were compared with reference data from the literature during abduction of the humerus in the range 20°–120°. The root mean square error for the anterior, lateral and posterior part between the simulated muscle elements and reference data from the literature was 3.9, 1.7 and 5.8 mm, respectively. The largest deviation occurred on the outer elements of the muscle groups, with 12.6, 10.4 and 20.5 mm, respectively. During abduction, there is no overlapping of the muscle elements and these are in continuous contact with the torus obstacles, thus enabling a continuous force transmission. This results in a rising trend of the resultant GHJF. The torus obstacle approach as a wrapping method for the deltoid muscles provides a guided muscle pathing by simultaneously approximating the curvature of the deltoid muscle. The results from the comparison of the simulated moment arms and the resultant GHJF are in accordance with those in the literature in the range 20°–120° of abduction. Although this study shows the strength of the torus obstacle as a wrapping approach, the method of fitting the tori according to MRI data was not suitable. A cadaver study is recommended to better validate and mathematically describe the torus approach. KW - Muscoloskeletal model KW - AnyBody Modeling System KW - MRI KW - Shoulder joint complex KW - Muscle trajectory KW - Torus KW - Wrapping Y1 - 2020 U6 - https://doi.org/10.1016/j.jbiomech.2020.109864 VL - 109 IS - August PB - Elsevier ER - TY - JOUR A1 - Aurbach, Maximilian A1 - Spicka, Jan A1 - Süß, Franz A1 - Dendorfer, Sebastian T1 - Evaluation of musculoskeletal modelling parameters of the shoulder complex during humeral abduction above 90° JF - Journal of Biomechanics N2 - Based on electromyographic data and force measurements within the shoulder joint, there is an indication that muscle and resulting joint reaction forces keep increasing over an abduction angle of 90°. In inverse dynamics models, no single parameter could be attributed to simulate this force behaviour accordingly. The aim of this work is to implement kinematic, kinetic and muscle model modifications to an existing model of the shoulder (AnyBody™) and assess their single and combined effects during abduction up to 140° humeral elevation. The kinematics and the EMG activity of 10 test subjects were measured during humeral abduction. Six modifications were implemented in the model: alternative wrapping of the virtual deltoid muscle elements, utilization of a three element Hill model, strength scaling, motion capture driven clavicle elevation/protraction, translation of the GH joint in dependency of the acting forces and an alteration of the scapula/clavicle rhythm. From the six modifications, 16 different combinations were considered. Parameter combinations with the Hill model changed the resultant GH joint reaction force and led to an increase in force during abduction of the humerus above 90°. Under the premise of muscle activities and forces within the GH joint rising after 90° of humeral abduction, we propose that the Hill type muscle model is a crucial parameter for accurately modelling the shoulder. Furthermore, the outcome of this study indicates that the Hill model induces the co-contraction of the muscles of the shoulder without the need of an additional stability criterion for an inverse dynamics approach. KW - Shoulder joint KW - Musculoskeletal modelling KW - EMG KW - Glenohumeral joint reaction force KW - Muscle model KW - Schultergelenk KW - Bewegungsapparat KW - Biomechanik KW - Simulation Y1 - 2020 U6 - https://doi.org/10.1016/j.jbiomech.2020.109817 VL - 106 IS - June PB - Elsevier 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 - CHAP A1 - Horner, Marc A1 - Dendorfer, Sebastian A1 - Kiis, Arne A1 - Lawrenchuk, Mike A1 - Verma, Gunjan T1 - A Patient based simulation workflow for orthopedic device design and analysis T2 - SBC Ortho Workshop, June 2011 Y1 - 2011 ER - TY - CHAP A1 - Dendorfer, Sebastian T1 - The effect of multifidus muscles atrophy following disc herniation on disc loading T2 - Deutsche Gesellschaft für Biomechanik, Murnau, 2011 Y1 - 2011 ER - TY - GEN A1 - Melzner, Maximilian A1 - Ismail, Khaled A1 - Rušavý, Zdeněk A1 - Kališ, Vladimír A1 - Süß, Franz A1 - Dendorfer, Sebastian T1 - Musculoskeletal Lower Back Load of Accoucheurs During Delivery T2 - 26th Congress of the European Society of Biomechanics, July 11-14, 2021, Milan, Italy N2 - With the progress in modern medicine, it was possible to significantly reduce the risks of birth for mother and child. One aspect that has received less attention so far is the risk of injury to the accoucheurs (obstetricians and midwives) during the birth process. Indeed, studies indicate that 92% of midwives suffer from musculoskeletal disorders, with the lower back being the main cause of complaints (72%). The aim of this study was to investigate two commonly used postural techniques used by accoucheurs during childbirth and to analyze the resulting load on the lower back using the AnyBodyTM musculoskeletal simulation software. Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-20208 CY - Milan ER - TY - CHAP A1 - Aurbach, Maximilian A1 - Jungtäubl, Dominik A1 - Spicka, Jan A1 - Dendorfer, Sebastian T1 - EMG-based validation of musculoskeletal models considering crosstalk T2 - World Congress Biomechanics, 28-30 June 2018, Dublin N2 - BACKGROUND: Validation and verification of multibody musculoskeletal models sEMG is a difficult process because of the reliability of sEMG data and the complex relationship of muscle force and sEMG. OBJECTIVE: This work aims at comparing experimentally recorded and simulated muscle activities considering a numerical model for crosstalk. METHODS: For providing an experimentally derived reference data set, subjects were performing elevations of the arm, where the activities of the contemplated muscle groups were measured by sEMG sensors. Computed muscle activities were further processed and transformed into an artificial electromyographical signal, which includes a numerical crosstalk model. In order to determine whether the crosstalk model provides a better agreement with the measured muscle activities, the Pearson correlation coefficient has been computed as a qualitative way of assessing the curve progression of the data sets. RESULTS: The results show an improvement in the correlation coefficient between the experimental data and the simulated muscle activities when taking crosstalk into account. CONCLUSIONS: Although the correlation coefficient increased when the crosstalk model was utilized, it is questionable if the discretization of both, the crosstalk and the musculoskeletal model, is accurate enough. Y1 - 2018 U6 - https://doi.org/10.1109/BIOMDLORE.2018.8467211 ER - TY - VIDEO A1 - Auer, Simon A1 - Reinker, Lukas A1 - Süß, Franz A1 - Kubowitsch, Simone A1 - Krutsch, Werner A1 - Weber, Markus A1 - Renkawitz, Tobias A1 - Dendorfer, Sebastian T1 - Webcast: Effect of mental demand on leg loading in highly dynamic motion N2 - Football players have a high risk of leg muscle injuries, especially when exposed to mental stress. Injuries to muscles of the thigh are common in amateur and professional football, representing almost a third of all injuries. These injuries occur primarily in non-contact situations and from overuse. They can lead to a range of costs, including financial costs associated with treatment as well as those associated with long-term recovery, and absence from training and/or competition. Further, there is a high risk of injury recurrence and subsequent injury. KW - Webcast KW - AnyBody KW - Stress KW - Football KW - Speedcourt Y1 - 2020 UR - https://www.youtube.com/watch?v=uSc_9XlnkaA ER - TY - GEN A1 - Englert, Carsten A1 - Dendorfer, Sebastian T1 - Einfluss der Rotatorenmanschette auf die glenohumerale Stabilität T2 - 20. Intensivkurs Schulterendoprothetik Marburg KW - Biomechanik Y1 - 2022 CY - Marburg ER - TY - GEN A1 - Dendorfer, Sebastian T1 - The influence of modeling parameters in the AnyBody Modeling System on muscle and joint loading in the shoulder T2 - International Shoulder Group Meeting Y1 - 2021 VL - 05 ER - TY - GEN A1 - Dendorfer, Sebastian T1 - Biomechanische Aspekte bei Sportverletzungen T2 - OT World Leipzig, Internationale Fachmesse und Weltkongress für Orthopädie und Rehatechnik, 10.-13. Mai 2022 Y1 - 2022 ER - TY - GEN A1 - Dendorfer, Sebastian T1 - KI-basierte mechanische Modelle für Prävention, Diagnostik und Rehabilitation T2 - Serien-Webmeeting zu AI - KI-basierte Bildanalyse zur computer-unterstützten Frakturerkennung, 09.11.22 Y1 - 2022 ER - TY - VIDEO A1 - Melzner, Maximilian A1 - Engelhardt, Lucas T1 - AnyBody Webcast - A new musculoskeletal AnyBody™ detailed hand model Y1 - 2020 UR - https://www.youtube.com/watch?v=E4xnbjRJYm8&t=631s ER - TY - GEN A1 - Eger, Maximilian A1 - Bergstraesser, Marcel A1 - Dendorfer, Sebastian A1 - Lenich, Andreas A1 - Pfeifer, Christian T1 - Influence of radial head prosthetic design on humeroradial stability: Validation of a test rig therefore T2 - DOKU2022, Deutscher Kongress für Orthopädie und Unfallchirurgie, 25.-28. 10.2022, Berlin KW - radial head prostheses KW - humeroradial stability KW - radial head arthroplasty KW - subluxation Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:0183-22dkou6115 PB - German Medical Science GMS Publishing House CY - Düsseldorf ER - TY - THES A1 - Putzer, Michael T1 - Development of subject-specific musculoskeletal models for studies of lumbar loading N2 - Anatomical differences between individuals are often neglected in musculoskeletal models, but they are necessary in case of subject-specific questions regarding the lumbar spine. A modification of models to each subject is complex and the effects on lumbar loading are difficult to assess. The objective of this thesis is to create a validated musculoskeletal model of the human body, which facilitates a subject-specific modification of the geometry of the lumbar spine. Furthermore, important parameters are identified in sensitivity studies and a case study regarding multifidus muscle atrophy after a disc herniation is conducted. Therefore, a generic model is heavily modified and a semi-automatic process is implemented. This procedure remodels the geometry of the lumbar spine to a subject-specific one on basis of segmented medical images. The resulting five models are validated with regard to the lumbar loading at the L4/L5 level. The influence of lumbar ligament stiffness is determined by changing the stiffness values of all lumbar ligaments in eleven steps during a flexion motion. Sensitivities of lumbar loading to an altered geometry of the lumbar spine are identified by varying ten lumbar parameters in simulations with each model in four postures. The case study includes an analysis of the loading of the multifidus muscle and of the lumbar discs throughout various stages of disc herniation. This time each model performs four motions with two different motion rhythms. The results indicate that lumbar motion and loading is dependent on lumbar ligament stiffness. Furthermore, subject-specific modelling of the lumbar spine should include at least the vertebral height, disc height and lumbar lordosis. The results of the case study suggest that an overloading of the multifidus muscle could follow disc herniation. Additionally, a subsequent atrophy of the muscles could expose adjacent levels to an increased loading, but these findings are highly dependent on the individual. KW - Lendenwirbelsäule KW - Geometrie KW - Lendenwirbelsäulenkrankheit KW - Computertomografie KW - Modell KW - Hochschulschrift Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:706-5924 N1 - Kooperative Promotion an der Fakultät Maschinenbau der Ostbayerischen Technischen Hochschule Regensburg (OTH.R) im Labor für Biomechanik (LBM) bei Prof. Dr.-Ing. Sebastian Dendorfer und Labor für Faserverbundtechnik (LFT) bei Prof. Dr.-Ing. Ingo Ehrlich ER - TY - CHAP A1 - Putzer, Michael A1 - Penzkofer, Rainer A1 - Ehrlich, Ingo A1 - Rasmussen, John A1 - Gebbeken, Norbert A1 - Dendorfer, Sebastian T1 - Musculoskeletal simulations to investigate the influence of vertebral geometrical parameters on lumbar spine loading T2 - 7th World Congress of Biomechanics, Boston, United States, 04/07/14 -11/07/14 Y1 - 2014 ER - TY - JOUR A1 - Grad, Marius A1 - Nadammal, Naresh A1 - Schultheiss, Ulrich A1 - Lulla, Philipp A1 - Noster, Ulf T1 - An Integrative Experimental Approach to Design Optimization and Removal Strategies of Supporting Structures Used during L-PBF of SS316L Aortic Stents JF - Applied Sciences N2 - One of the fundamental challenges in L-PBF of filigree geometries, such as aortic stents used in biomedical applications, is the requirement for a robust yet easily removable support structure that allows each component to be successfully fabricated without distortion. To solve this challenge, an integrative experimental approach was attempted in the present study by identifying an optimal support structure design and an optimized support removal strategy for this design. The specimens were manufactured using four different support structure designs based on the geometry exposed to the laser beam during the L-PBF. Support removal procedures included sand blasting (SB), glass bead blasting (GB), and electrochemical polishing (ECP). The two best-performing designs (line and cross) were chosen due to shorter lead times and lower material consumption. As an additional factor that indicates a stable design, the breaking load requirement to remove the support structures was determined. A modified line support with a 145° included angle was shown to be the best support structure design in terms of breaking load, material consumption, and manufacturing time. All three procedures were used to ensure residue-free support removal for this modified line support design, with ECP proving to be the most effective. Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-25612 N1 - Corresponding author: Marius Grad VL - 11 IS - 19 SP - 1 EP - 22 PB - MPDL ER - TY - JOUR A1 - Weber, Markus A1 - Merle, Christian A1 - Nawabi, Danyal H. A1 - Dendorfer, Sebastian A1 - Grifka, Joachim A1 - Renkawitz, Tobias T1 - Inaccurate offset restoration in total hip arthroplasty results in reduced range of motion JF - Scientific Reports N2 - Offset restoration in total hip arthroplasty (THA) is associated with postoperative range of motion (ROM) and gait kinematics. We aimed to research into the impact of high offset (HO) and standard stems on postoperative ROM. 121 patients received cementless THA through a minimally-invasive anterolateral approach. A 360° hip ROM analysis software calculated impingement-free hip movement based on postoperative 3D-CTs compared to ROM values necessary for activities of daily living (ADL). The same model was then run a second time after changing the stem geometry between standard and HO configuration with the implants in the same position. HO stems showed higher ROM for all directions between 4.6 and 8.9° (p < 0.001) compared with standard stems but with high interindividual variability. In the subgroup with HO stems for intraoperative offset restoration, the increase in ROM was even higher for all ROM directions with values between 6.1 and 14.4° (p < 0.001) compared to offset underrestoration with standard stems. Avoiding offset underrestoration resulted in a higher amount of patients of over 20% for each ROM direction that fulfilled the criteria for ADL (p < 0.001). In contrast, in patients with standard stems for offset restoration ROM did increase but not clinically relevant by offset overcorrection for all directions between 3.1 and 6.1° (p < 0.001). Offset overcorrection by replacing standard with HO stems improved ROM for ADL in a low number of patients below 10% (p > 0.03). Patient-individual restoration of offset is crucial for free ROM in THA. Both over and underrestoration of offset should be avoided. KW - Adaptive clinical trial KW - Bone imaging Y1 - 2020 U6 - https://doi.org/10.1038/s41598-020-70059-1 VL - 10 IS - 13208 SP - 9 PB - Nature ER - TY - GEN A1 - Melzner, Maximilian A1 - Dendorfer, Sebastian T1 - Biomechanik und muskuloskeletale Simulation T2 - Jahreskongress des ISPO Deutschland e.V., 2./3. Juni 2022, Hedelberg Y1 - 2022 ER - TY - GEN A1 - Melzner, Maximilian A1 - Pfeifer, Christian A1 - Süß, Franz A1 - Dendorfer, Sebastian T1 - Muskuloskeletal analysis of elbow stability for common injury patterns 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 - 654 ER - TY - JOUR A1 - Heine, Norbert A1 - Eigenberger, Andreas A1 - Brebant, Vanessa A1 - Hoesl, Vanessa A1 - Brix, Eva A1 - Prantl, Lukas A1 - Kempa, Sally T1 - Comparison of skin sensitivity following breast reconstruction with three different techniques: Autologous fat grafting, DIEP flap and expander/implant JF - Clinical Hemorheology and Microcirculation N2 - BACKGROUND: Autologous fat grafting (AFG) has been established over the past two decades as an additive technique during and after breast reconstruction. Complete reconstruction of the breast mound with AFG alone represents an exceptional technique that has been published mostly in case reports or in studies with limited cases.The purpose of this study is to investigate the influence of three different techniques for breast reconstruction on the recovery of skin sensitivity at the reconstructed breast. METHODS: The study included 30 patients after mastectomy following breast cancer. Three groups were examined: A) breast reconstruction by autologous fat grafting (AFG), B) breast reconstruction by deep inferior epigastric artery perforator flap (DIEP) and C) breast reconstruction by expander/implant (TE).Biometric data were compared; sensitivity tests were performed using Semmes-Weinstein monofilaments.The non-operated, healthy contralateral breasts of the patients were used as a reference. RESULTS: While the traditional reconstruction techniques by microsurgical anastomosed perforator flap or expander/implant showed a strongly decreased or completely missing sensitivity of the skin, the tests after reconstruction by AFG represented high values of sensory recovery, which came close to the reference group of non-operated breasts. CONCLUSION: To our knowledge, this is the first study to compare skin sensitivity after AFG-based reconstruction to established techniques for breast reconstruction. We could demonstrate in a limited group of patients, that breast reconstruction by autologous fat grafting can achieve higher values of skin sensitivity compared to traditional techniques. KW - Mammoplastik KW - Brusterhaltende Therapie KW - Haut KW - Empfindlichkeit Y1 - 2022 U6 - https://doi.org/10.3233/ch-219203 SN - 1875-8622 SN - 1386-0291 VL - 80 IS - 4 SP - 389 EP - 397 PB - IOS Press ER - TY - JOUR A1 - Prantl, Lukas A1 - Eigenberger, Andreas A1 - Reinhard, Ruben A1 - Siegmund, Andreas A1 - Heumann, Kerstin A1 - Felthaus, Oliver T1 - Cell-Enriched Lipotransfer (CELT) Improves Tissue Regeneration and Rejuvenation without Substantial Manipulation of the Adipose Tissue Graft JF - Cells N2 - The good availability and the large content of adult stem cells in adipose tissue has made it one of the most interesting tissues in regenerative medicine. Although lipofilling is one of the most frequent procedures in plastic surgery, the method still struggles with high absorption rates and volume losses of up to 70%. Therefore, many efforts have been made to optimize liposuction and to process the harvested tissue in order to increase fat graft retention. Because of their immunomodulatory properties, their cytokine secretory activity, and their differentiation potential, enrichment with adipose tissue-derived stem cells was identified as a promising tool to promote transplant survival. Here, we review the important parameters for lipofilling optimization. Finally, we present a new method for the enrichment of lipoaspirate with adipose tissue-derived stem cells and discuss the parameters that contribute to fat graft survival. Y1 - 2022 U6 - https://doi.org/10.3390/cells11193159 VL - 11 IS - 19 SP - 1 EP - 11 PB - MDPI ER - TY - CHAP A1 - Galibarov, Pavel E. A1 - Al-Munajjed, Amir Andreas A1 - Dendorfer, Sebastian A1 - Christensen, Soeren Toerholm A1 - Rasmussen, John T1 - The effect of varying the stiffness of spinal fusion devices on the adjacent levels using multibody dynamics simulation T2 - Orthopaedic Proceedings N2 - INTRODUCTION Several clinical studies demonstrated long-term adjacent-level effects after implantation of spinal fusion devices[1]. These effects have been reported as adjacent joint degeneration and the development of new symptoms correlating with adjacent segment degeneration[2] and the trend has therefore gone to motion preservation devices; however, these effects have not been understood very well and have not been investigated thoroughly[3]. The aim of this study is to investigate the effect of varying the stiffness of spinal fusion devices on the adjacent vertebral levels. Disc forces, moments and facet joint forces were analyzed. METHODS The AnyBody Modeling System was used to compute the in-vivo muscle and joint reaction forces of a musculoskeletal model. The full body model used in this study consists of 188 muscle fascicles in the lumbar spine and more than 1000 individual muscle branches in total. The model has been proposed by de Zee et al.[3], validated by Rasmussen et al.[4] and by Galibarov et al.[5]. The new model[5] determines the individual motions between vertebrae based on the equilibrium between forces acting on the vertebrae from muscles and joints and the passive stiffness in disks and ligaments, figure 1a. An adult of 1.75 m and 75 kg with a spinal implant in L4L5 was modeled. This model was subjected to a flexion-extension motion using different elastic moduli to analyze and compare to a non-implanted scenario. The analyzed variables were vertebral motion, the disc reaction forces and moments, as well as facet joint forces in the treated and the adjacent levels: L2L3, L3L4, L4L5 and L5-Sacrum. RESULTS When introducing a spinal fusion device in the L4L5 joint the reaction forces and moments decreased in this joint with stiffer devices leading to lower joint loads. However, in the adjacent joints, L3L4 and L5Sacrum, an increase was observed when implanting stiffer devices. Similar trends could be found for the L2L3 joint. The loads in the facet joints showed the same trends. While introducing a spinal fusion device reduced the facet joint forces in the treated joint, the loads in the adjacent facet joints were increased according to the stiffness of the implanted device, figure 1b. DISCUSSION While the treated disc joint showed reduced motion and loads, the adjacent levels demonstrated a significant increase. In particular, the increased facet joint forces in the adjacent levels can lead to adjacent level facet pain or accelerated facet joint degeneration. Introducing a device resulted in preventing facet contact and therefore facet joint loads, even using the device with the lowest stiffness. CONCLUSION The presented model shows that clinical complications such as facet joint degeneration in adjacent levels after implantation of spinal fusion device are consistent with the change in the mechanical-stimulus distribution in the system. Y1 - 2011 VL - 94-B IS - SUPP_XL01 Sep 2012 SP - 2 ER - TY - CHAP A1 - Galibarov, Pavel E. A1 - Dendorfer, Sebastian A1 - Christensen, Soeren Toerholm T1 - On modelling spine curvature dependent on muscular and external forces in multibody dynamics system T2 - International Society of Biomechanics (ISB), 13th congress, 2011, Brussels, Belgium N2 - This paper presents a computational approach for investigating effect of muscular and external forces on curvature of the lumbar spine. Multibody dynamics system is used to compute the lumbar spine curvature using a force-dependent kinematics facility, e.g. this method allows releasing some degrees of freedom in order to be computed based on the current load configuration. Y1 - 2011 UR - https://paperpile.com/shared/63VCBY/download/2608c6d1-adef-0330-86f8-7996e623c627 SP - 2 ER - TY - CHAP A1 - Rasmussen, John A1 - Bichler, R. A1 - Christensen, Soeren Toerholm A1 - Wirix-Speetjens, Roel A1 - Dendorfer, Sebastian A1 - Renkawitz, Tobias T1 - Subject-specific Musculoskeletal Simulation of Hip Dislocation Risk in Activities of Daily Living T2 - Proceedings of the 2011 ORS Annual Meeting, Long Beach, CA. Y1 - 2011 UR - http://www.ors.org/Transactions/57/0306.pdf IS - Paper No. 306 ER - TY - CHAP A1 - Robie, Bruce A1 - Dendorfer, Sebastian A1 - Rasmussen, John A1 - Christensen, Soeren Toerholm T1 - Axial Rotation Requires Greatest Load in Multifidus Muscle – Potential Association with Low Back Pain? T2 - Annual Meeting of the AANS/CNS Section on Disorders of the Spine and Peripheral Nerves, 2011, Phoenix, Arizona Y1 - 2011 UR - https://paperpile.com/shared/o0LQEG ER - TY - CHAP A1 - Galibarov, Pavel E. A1 - Dendorfer, Sebastian A1 - Rasmussen, John T1 - Two Computational Models of the Lumbar Spine: BT - Comparison and Validation T2 - Proceedings of the 2011 ORS Annual Meeting, Long Beach, CA, vol. Marie Curie Initial Training Network "SpineFX" Y1 - 2011 UR - http://www.ors.org/Transactions/57/0786.pdf ER - TY - JOUR A1 - Hausleiter, Jörg A1 - Kastrati, Adnan A1 - Wessely, Rainer A1 - Dibra, Alban A1 - Mehilli, Julinda A1 - Schratzenstaller, Thomas A1 - Graf, Isolde A1 - Renke-Gluszko, Magdalena A1 - Behnisch, Boris A1 - Dirschinger, Josef A1 - Wintermantel, Erich A1 - Schömig, Albert T1 - Prevention of restenosis by a novel drug-eluting stent system with a dose-adjustable, polymer-free, on-site stent coating JF - European Heart Journal - Clinical research N2 - Aims Drug-eluting stents (DES) represent a major advance in interventional cardiology. Along with the success shown, current DES also present limitations related to the presence of polymer-coating, fixed drug, and dose used. With the ISAR (Individualized Drug-Eluting Stent System to Abrogate Restenosis) project, a DES system has been developed that permits individualized choice of the drug and dose to use for the given patient. The objective of this prospective dose finding study was to assess the feasibility, safety, and efficacy of a polymer-free on-site stent coating with increasing rapamycin doses. Methods and results In this dose finding study, 602 patients were sequentially enrolled in four groups: microporous bare metal stent (BMS), DES stents coated with a 0.5, 1.0, and 2.0% rapamycin solution. The angiographic in-segment restenosis rate at follow-up angiography was the primary study endpoint. In-segment restenosis was significantly reduced from 25.9% with BMS to 18.9, 17.2, and 14.7% with 0.5, 1.0, and 2.0% rapamycin-eluting stents, respectively (P=0.024). Similarly, the need for target lesion revascularization at 1 year follow-up was reduced from 21.5% with BMS to 16.4, 12.6, and 8.8% with 0.5, 1.0, and 2.0% rapamycin-eluting stents, respectively (P=0.006). Conclusion The placement of polymer-free stents coated on-site with rapamycin is feasible and safe. Furthermore, a dose-dependent efficacy in restenosis prevention is achievable with this new DES concept. KW - Restenosis KW - Stents KW - Randomized KW - Rapamycin KW - Polymer Y1 - 2005 U6 - https://doi.org/10.1093/eurheartj/ehi405 VL - 26 IS - 15 SP - 1475 EP - 1481 ER - TY - GEN A1 - Singh, Max Diamond T1 - MDR Implementation Status and Lessons Learned from the Past Months: A Notified Body Perspective T2 - Cambridge Healthtech Institute's 2nd Annual Medical Device Clinical Trial Design and Operations: Trial Design and Technology to Optimize Medical Device Trials, Orlando, Florida + Virtual, 02.-03.03.2021 Y1 - PB - Cambridge Innovation Institute ER - TY - GEN A1 - Singh, Max Diamond T1 - MDR implementation status & lessons learned BT - MDR-Audtis – Best Practive & Learning, Tuttlingen, 10.02.2021 Y1 - 2021 ER -