@inproceedings{WeissGrossmannLeiboldetal., author = {Weiß, Roman and Großmann, Benjamin and Leibold, Marion and Schlegl, Thomas and Wollherr, Dirk and Weiss, Roman and Grossmann, Benjamin}, title = {Modeling and nonlinear control of antagonistically actuating pneumatic artificial muscles}, series = {2017 IEEE International Conference on Advanced Intelligent Mechatronics (AIM), 3-7 July 2017, Munich, Germany}, booktitle = {2017 IEEE International Conference on Advanced Intelligent Mechatronics (AIM), 3-7 July 2017, Munich, Germany}, publisher = {IEEE}, doi = {10.1109/AIM.2017.8014001}, pages = {94 -- 99}, abstract = {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.}, language = {en} } @phdthesis{Putzer, author = {Putzer, Michael}, title = {Development of subject-specific musculoskeletal models for studies of lumbar loading}, publisher = {Shaker Verlag}, address = {D{\"u}ren}, isbn = {978-3-8440-6695-1}, doi = {10.2370/9783844066951}, pages = {142}, abstract = {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.}, language = {en} } @article{HoenickaKasparSchmidetal., author = {Hoenicka, Markus and Kaspar, Marcel and Schmid, Christof and Liebold, Andreas and Schrammel, Siegfried}, title = {Contact-free monitoring of vessel graft stiffness - proof of concept as a tool for vascular tissue engineering}, series = {Journal of tissue engineering and regenerative medicine}, volume = {11}, journal = {Journal of tissue engineering and regenerative medicine}, number = {10}, publisher = {Wiley}, doi = {10.1002/term.2186}, pages = {2828 -- 2835}, abstract = {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.}, language = {en} } @article{SellmerStanglBeyeretal., author = {Sellmer, Andreas and Stangl, Hubert and Beyer, Mandy and Gr{\"u}nstein, Elisabeth and Leonhardt, Michel and Pongratz, Herwig and Eichhorn, Emerich and Elz, Sigurd and Striegl, Birgit and Jenei-Lanzl, Zsuzsa and Dove, Stefan and Straub, Rainer H. and Kr{\"a}mer, Oliver H. and Mahboobi, Siavosh}, title = {Marbostat-100 Defines a New Class of Potent and Selective Antiinflammatory and Antirheumatic Histone Deacetylase 6 Inhibitors}, series = {Journal of medicinal chemistry}, volume = {61}, journal = {Journal of medicinal chemistry}, number = {8}, publisher = {ACS Publications}, doi = {10.1021/acs.jmedchem.7b01593}, pages = {3454 -- 3477}, abstract = {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.}, language = {en} } @article{KummerlinFabroPedersenetal., author = {Kummerlin, Jana and Fabro, Hannah Katharina and Pedersen, Peter Heide and Jensen, Kenneth Krogh and Pedersen, Dennis and Andersen, Michael Skipper}, title = {Measuring Knee Joint Laxity in Three Degrees-of-Freedom In Vivo Using a Robotics- and Image-Based Technology}, series = {Journal of Biomechanical Engineering}, volume = {144}, journal = {Journal of Biomechanical Engineering}, number = {8}, publisher = {The American Society of Mechanical Engineers (ASME)}, issn = {1528-8951}, doi = {10.1115/1.4053792}, pages = {7}, abstract = {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.}, language = {en} } @article{BaldwinHartlTschaikowskyetal., author = {Baldwin, Andrew and Hartl, Maximilian and Tschaikowsky, Mathaeus and Balzer, Bizan N. and Booth, Brian W.}, title = {Degradation and release of tannic acid from an injectable tissue regeneration bead matrix in vivo}, series = {Journal of biomedical materials research, part B - Applied Biomaterials}, volume = {110}, journal = {Journal of biomedical materials research, part B - Applied Biomaterials}, number = {5}, publisher = {Wiley}, issn = {1552-4981}, doi = {10.1002/jbm.b.34990}, pages = {1165 -- 1177}, abstract = {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.}, language = {en} } @article{ChatterjeeKobylinskiBasu, author = {Chatterjee, Subhomoy and Kobylinski, Sabine and Basu, Bikramjit}, title = {Finite Element Analysis to Probe the Influence of Acetabular Shell Design, Liner Material, and Subject Parameters on Biomechanical Response in Periprosthetic Bone}, series = {Journal of Biomechanical Engineering}, volume = {140}, journal = {Journal of Biomechanical Engineering}, number = {10}, publisher = {ASME}, issn = {1528-8951}, doi = {10.1115/1.4040249}, abstract = {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.}, language = {en} } @inproceedings{GeithWagner, author = {Geith, Markus A. and Wagner, Marcus}, title = {Numerical Analysis Of Stent Delivery Systems During Pre- And Intraoperative Processes}, series = {Deutsches LS-DYNA Forum 2018, Bamberg}, booktitle = {Deutsches LS-DYNA Forum 2018, Bamberg}, language = {en} } @article{SchmidtPenzkoferBachmaieretal., author = {Schmidt, Ulf and Penzkofer, Rainer and Bachmaier, Samuel and Augat, Peter}, title = {Implant Material and Design Alter Construct Stiffness in Distal Femur Locking Plate Fixation: A Pilot Study}, series = {Clinical Orthopaedics and Related Research®}, volume = {471}, journal = {Clinical Orthopaedics and Related Research®}, number = {9}, publisher = {The Association of Bone and Joint Surgeons}, doi = {10.1007/s11999-013-2867-0}, pages = {2808 -- 2814}, abstract = {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.}, language = {en} } @inproceedings{GeithSommerSchratzenstalleretal., author = {Geith, Markus A. and Sommer, Gerhard and Schratzenstaller, Thomas and Holzapfel, Gerhard A.}, title = {First Approaches in Quantifying Acute Vascular Damage due to Stenting}, series = {23rd Congress of the European Society of Biomechanics, July 2-5,2017, Seville, Spain}, booktitle = {23rd Congress of the European Society of Biomechanics, July 2-5,2017, Seville, Spain}, subject = {Stent}, language = {en} } @article{GeithEckmannHaspingeretal., author = {Geith, Markus A. and Eckmann, Jakob D. and Haspinger, Daniel Ch. and Agrafiotis, Emmanouil and Maier, Dominik and Szabo, Patrick and Sommer, Gerhard and Schratzenstaller, Thomas and Holzapfel, Gerhard A.}, title = {Experimental and mathematical characterization of coronary polyamide-12 balloon catheter membranes}, series = {PLoS One}, volume = {15}, journal = {PLoS One}, number = {6}, publisher = {PLOS}, doi = {10.1371/journal.pone.0234340}, pages = {1 -- 22}, abstract = {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.}, language = {en} } @article{GeithSwidergalHochholdingeretal., author = {Geith, Markus A. and Swidergal, Krzysztof and Hochholdinger, Bernd and Schratzenstaller, Thomas and Wagner, Marcus and Holzapfel, Gerhard A.}, title = {On the importance of modeling balloon folding, pleating, and stent crimping: An FE study comparing experimental inflation tests}, series = {International Journal for Numerical Methods in Biomedical Engineering}, volume = {35}, journal = {International Journal for Numerical Methods in Biomedical Engineering}, number = {11}, publisher = {Wiley}, doi = {10.1002/cnm.3249}, abstract = {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.}, subject = {Stent}, language = {en} } @inproceedings{DendorferFeldottoWalchetal., author = {Dendorfer, Sebastian and Feldotto, Benedikt and Walch, Blasius and Koch, Patrick and Knoll, Alois}, title = {Co-Development of an Infant Prototype in Hardware and Simulation based on CT Imaging Data}, series = {IEEE International Conference on Cyborg and Bionic Systems (CBS), 2019, Munich}, booktitle = {IEEE International Conference on Cyborg and Bionic Systems (CBS), 2019, Munich}, pages = {6}, abstract = {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.}, subject = {Biomechanische Analyse}, language = {en} } @article{WeberDendorferBulstraetal., author = {Weber, Tim A. and Dendorfer, Sebastian and Bulstra, Sjoerd K. and Grifka, Joachim and Verkerke, Gijsbertus Jacob and Renkawitz, Tobias}, title = {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}, series = {Gait \& Posture}, volume = {vol. 49}, journal = {Gait \& Posture}, doi = {10.1016/j.gaitpost.2016.06.035}, pages = {418 -- 425}, abstract = {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.}, language = {en} } @article{RenkawitzWeberDullienetal., author = {Renkawitz, Tobias and Weber, Tim A. and Dullien, Silvia and Woerner, Michael and Dendorfer, Sebastian and Grifka, Joachim and Weber, Markus}, title = {Leg length and offset differences above 5 mm after total hip arthroplasty are associated with altered gait kinematics}, series = {Gait \& Posture}, volume = {vol. 49}, journal = {Gait \& Posture}, doi = {10.1016/j.gaitpost.2016.07.011}, pages = {196 -- 201}, abstract = {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.}, language = {en} } @article{IgnasiakDendorferFerguson, author = {Ignasiak, Dominika and Dendorfer, Sebastian and Ferguson, Stephen J.}, title = {Thoracolumbar spine model with articulated ribcage for the prediction of dynamic spinal loading}, series = {Journal of Biomechanics}, volume = {vol. 49}, journal = {Journal of Biomechanics}, number = {6}, publisher = {Elsevier Science}, doi = {10.1016/j.jbiomech.2015.10.010}, pages = {959 -- 966}, abstract = {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.}, subject = {Brustwirbels{\"a}ule}, language = {en} } @article{HoelscherWeberLazarevetal., author = {H{\"o}lscher, Thomas and Weber, Tim A. and Lazarev, Igor and Englert, Carsten and Dendorfer, Sebastian}, title = {The influence of rotator cuff tears on glenohumeral stability during abduction tasks}, series = {Journal of Orthopaedic Research}, volume = {34}, journal = {Journal of Orthopaedic Research}, number = {9}, doi = {10.1002/jor.23161}, pages = {1628 -- 1635}, abstract = {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.}, subject = {Rotatorenmanschettenriss}, language = {en} } @inproceedings{AuerKubowitschKrutschetal., author = {Auer, Simon and Kubowitsch, Simone and Krutsch, Werner and Renkawitz, Tobias and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Effect of mental demand on knee forces in professional youth soccer players}, series = {ISBS Proceedings Archive}, volume = {38}, booktitle = {ISBS Proceedings Archive}, number = {1, Art. 28}, abstract = {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.}, subject = {Kniegelenk}, language = {en} } @article{Dendorfer, author = {Dendorfer, Sebastian}, title = {{\"A}lterwerden muss auch mal wehtun!}, series = {Gesunde Hochschule, OTH Regensburg, 4.7.2016}, journal = {Gesunde Hochschule, OTH Regensburg, 4.7.2016}, language = {de} } @article{PutzerAuerMalpicaetal., author = {Putzer, Michael and Auer, Stefan and Malpica, William and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {A numerical study to determine the effect of ligament stiffness on kinematics of the lumbar spine during flexion}, series = {BMC Musculoskeletal Disorders}, volume = {17}, journal = {BMC Musculoskeletal Disorders}, number = {95}, doi = {10.1186/s12891-016-0942-x}, abstract = {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.}, language = {en} } @article{AurbachŠpičkaSuessetal., author = {Aurbach, Maximilian and Špička, Jan and S{\"u}ß, Franz and Vychytil, J. and Havelkov{\´a}, Leonard and Ryba, T. and Dendorfer, Sebastian}, title = {Torus obstacle method as a wrapping approach of the deltoid muscle group for humeral abduction in musculoskeletal simulation}, series = {Journal of Biomechanics}, volume = {109}, journal = {Journal of Biomechanics}, number = {August}, publisher = {Elsevier}, doi = {10.1016/j.jbiomech.2020.109864}, abstract = {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.}, language = {en} } @article{AurbachSpickaSuessetal., author = {Aurbach, Maximilian and Spicka, Jan and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Evaluation of musculoskeletal modelling parameters of the shoulder complex during humeral abduction above 90°}, series = {Journal of Biomechanics}, volume = {106}, journal = {Journal of Biomechanics}, number = {June}, publisher = {Elsevier}, doi = {10.1016/j.jbiomech.2020.109817}, abstract = {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.}, subject = {Schultergelenk}, language = {en} } @article{SchmitzNeumannNeumannetal., author = {Schmitz, Paul and Neumann, Christoph Cornelius and Neumann, Carsten and Nerlich, Michael and Dendorfer, Sebastian}, title = {Biomechanical analysis of iliac crest loading following cortico-cancellous bone harvesting}, series = {Journal of Orthopaedic Surgery and Research}, volume = {13}, journal = {Journal of Orthopaedic Surgery and Research}, number = {108}, publisher = {Springer Nature}, doi = {10.1186/s13018-018-0822-1}, pages = {1 -- 8}, abstract = {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.}, subject = {Beckenkammknochen}, language = {en} } @inproceedings{HornerDendorferKiisetal., author = {Horner, Marc and Dendorfer, Sebastian and Kiis, Arne and Lawrenchuk, Mike and Verma, Gunjan}, title = {A Patient based simulation workflow for orthopedic device design and analysis}, series = {SBC Ortho Workshop, June 2011}, booktitle = {SBC Ortho Workshop, June 2011}, language = {en} } @inproceedings{Dendorfer, author = {Dendorfer, Sebastian}, title = {The effect of multifidus muscles atrophy following disc herniation on disc loading}, series = {Deutsche Gesellschaft f{\"u}r Biomechanik, Murnau, 2011}, booktitle = {Deutsche Gesellschaft f{\"u}r Biomechanik, Murnau, 2011}, language = {en} } @misc{MelznerIsmailRušavyetal., author = {Melzner, Maximilian and Ismail, Khaled and Rušav{\´y}, Zdeněk and Kališ, Vladim{\´i}r and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Musculoskeletal Lower Back Load of Accoucheurs During Delivery}, series = {26th Congress of the European Society of Biomechanics, July 11-14, 2021, Milan, Italy}, journal = {26th Congress of the European Society of Biomechanics, July 11-14, 2021, Milan, Italy}, address = {Milan}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-20208}, abstract = {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.}, language = {en} } @inproceedings{AurbachJungtaeublSpickaetal., author = {Aurbach, Maximilian and Jungt{\"a}ubl, Dominik and Spicka, Jan and Dendorfer, Sebastian}, title = {EMG-based validation of musculoskeletal models considering crosstalk}, series = {World Congress Biomechanics, 28-30 June 2018, Dublin}, booktitle = {World Congress Biomechanics, 28-30 June 2018, Dublin}, doi = {10.1109/BIOMDLORE.2018.8467211}, abstract = {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.}, language = {en} } @misc{AuerReinkerSuessetal., author = {Auer, Simon and Reinker, Lukas and S{\"u}ß, Franz and Kubowitsch, Simone and Krutsch, Werner and Weber, Markus and Renkawitz, Tobias and Dendorfer, Sebastian}, title = {Webcast: Effect of mental demand on leg loading in highly dynamic motion}, abstract = {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.}, language = {en} } @misc{EnglertDendorfer, author = {Englert, Carsten and Dendorfer, Sebastian}, title = {Einfluss der Rotatorenmanschette auf die glenohumerale Stabilit{\"a}t}, series = {20. Intensivkurs Schulterendoprothetik Marburg}, journal = {20. Intensivkurs Schulterendoprothetik Marburg}, address = {Marburg}, language = {de} } @misc{Dendorfer, author = {Dendorfer, Sebastian}, title = {The influence of modeling parameters in the AnyBody Modeling System on muscle and joint loading in the shoulder}, series = {International Shoulder Group Meeting}, volume = {05}, journal = {International Shoulder Group Meeting}, language = {en} } @misc{Dendorfer, author = {Dendorfer, Sebastian}, title = {Biomechanische Aspekte bei Sportverletzungen}, series = {OT World Leipzig, Internationale Fachmesse und Weltkongress f{\"u}r Orthop{\"a}die und Rehatechnik, 10.-13. Mai 2022}, journal = {OT World Leipzig, Internationale Fachmesse und Weltkongress f{\"u}r Orthop{\"a}die und Rehatechnik, 10.-13. Mai 2022}, language = {de} } @misc{Dendorfer, author = {Dendorfer, Sebastian}, title = {KI-basierte mechanische Modelle f{\"u}r Pr{\"a}vention, Diagnostik und Rehabilitation}, series = {Serien-Webmeeting zu AI - KI-basierte Bildanalyse zur computer-unterst{\"u}tzten Frakturerkennung, 09.11.22}, journal = {Serien-Webmeeting zu AI - KI-basierte Bildanalyse zur computer-unterst{\"u}tzten Frakturerkennung, 09.11.22}, organization = {Deutsche Gesellschaft f{\"u}r Orthop{\"a}die und Orthop{\"a}dische Chirurgie}, language = {de} } @misc{MelznerEngelhardt, author = {Melzner, Maximilian and Engelhardt, Lucas}, title = {AnyBody Webcast - A new musculoskeletal AnyBody™ detailed hand model}, language = {en} } @misc{EgerBergstraesserDendorferetal., author = {Eger, Maximilian and Bergstraesser, Marcel and Dendorfer, Sebastian and Lenich, Andreas and Pfeifer, Christian}, title = {Influence of radial head prosthetic design on humeroradial stability: Validation of a test rig therefore}, series = {DOKU2022, Deutscher Kongress f{\"u}r Orthop{\"a}die und Unfallchirurgie, 25.-28. 10.2022, Berlin}, journal = {DOKU2022, Deutscher Kongress f{\"u}r Orthop{\"a}die und Unfallchirurgie, 25.-28. 10.2022, Berlin}, publisher = {German Medical Science GMS Publishing House}, address = {D{\"u}sseldorf}, doi = {10.3205/22dkou611}, url = {http://nbn-resolving.de/urn:nbn:de:0183-22dkou6115}, language = {en} } @phdthesis{Putzer, author = {Putzer, Michael}, title = {Development of subject-specific musculoskeletal models for studies of lumbar loading}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:706-5924}, pages = {140}, abstract = {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.}, subject = {Lendenwirbels{\"a}ule}, language = {en} } @inproceedings{PutzerPenzkoferEhrlichetal., author = {Putzer, Michael and Penzkofer, Rainer and Ehrlich, Ingo and Rasmussen, John and Gebbeken, Norbert and Dendorfer, Sebastian}, title = {Musculoskeletal simulations to investigate the influence of vertebral geometrical parameters on lumbar spine loading}, series = {7th World Congress of Biomechanics, Boston, United States, 04/07/14 -11/07/14}, booktitle = {7th World Congress of Biomechanics, Boston, United States, 04/07/14 -11/07/14}, language = {de} } @article{GradNadammalSchultheissetal., author = {Grad, Marius and Nadammal, Naresh and Schultheiss, Ulrich and Lulla, Philipp and Noster, Ulf}, title = {An Integrative Experimental Approach to Design Optimization and Removal Strategies of Supporting Structures Used during L-PBF of SS316L Aortic Stents}, series = {Applied Sciences}, volume = {11}, journal = {Applied Sciences}, number = {19}, publisher = {MPDL}, doi = {10.3390/app11199176}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-25612}, pages = {1 -- 22}, abstract = {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.}, language = {en} } @article{WeberMerleNawabietal., author = {Weber, Markus and Merle, Christian and Nawabi, Danyal H. and Dendorfer, Sebastian and Grifka, Joachim and Renkawitz, Tobias}, title = {Inaccurate offset restoration in total hip arthroplasty results in reduced range of motion}, series = {Scientific Reports}, volume = {10}, journal = {Scientific Reports}, number = {13208}, publisher = {Nature}, doi = {10.1038/s41598-020-70059-1}, pages = {9}, abstract = {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.}, language = {en} } @misc{MelznerDendorfer, author = {Melzner, Maximilian and Dendorfer, Sebastian}, title = {Biomechanik und muskuloskeletale Simulation}, series = {Jahreskongress des ISPO Deutschland e.V., 2./3. Juni 2022, Hedelberg}, journal = {Jahreskongress des ISPO Deutschland e.V., 2./3. Juni 2022, Hedelberg}, organization = {International Society for Prosthetics and Orthotics}, language = {de} } @misc{MelznerPfeiferSuessetal., author = {Melzner, Maximilian and Pfeifer, Christian and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Muskuloskeletal analysis of elbow stability for common injury patterns}, series = {27th Congress of the European Society of Biomechanics, 26 - 29 June 2022, Porto, Portugal}, journal = {27th Congress of the European Society of Biomechanics, 26 - 29 June 2022, Porto, Portugal}, pages = {654}, language = {en} } @article{HeineEigenbergerBrebantetal., author = {Heine, Norbert and Eigenberger, Andreas and Brebant, Vanessa and Hoesl, Vanessa and Brix, Eva and Prantl, Lukas and Kempa, Sally}, title = {Comparison of skin sensitivity following breast reconstruction with three different techniques: Autologous fat grafting, DIEP flap and expander/implant}, series = {Clinical Hemorheology and Microcirculation}, volume = {80}, journal = {Clinical Hemorheology and Microcirculation}, number = {4}, publisher = {IOS Press}, issn = {1875-8622}, doi = {10.3233/ch-219203}, pages = {389 -- 397}, abstract = {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.}, subject = {Mammoplastik}, language = {en} } @article{PrantlEigenbergerReinhardetal., author = {Prantl, Lukas and Eigenberger, Andreas and Reinhard, Ruben and Siegmund, Andreas and Heumann, Kerstin and Felthaus, Oliver}, title = {Cell-Enriched Lipotransfer (CELT) Improves Tissue Regeneration and Rejuvenation without Substantial Manipulation of the Adipose Tissue Graft}, series = {Cells}, volume = {11}, journal = {Cells}, number = {19}, publisher = {MDPI}, doi = {10.3390/cells11193159}, pages = {1 -- 11}, abstract = {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.}, language = {en} } @inproceedings{GalibarovAlMunajjedDendorferetal., author = {Galibarov, Pavel E. and Al-Munajjed, Amir Andreas and Dendorfer, Sebastian and Christensen, Soeren Toerholm and Rasmussen, John}, title = {The effect of varying the stiffness of spinal fusion devices on the adjacent levels using multibody dynamics simulation}, series = {Orthopaedic Proceedings}, volume = {94-B}, booktitle = {Orthopaedic Proceedings}, number = {SUPP_XL01 Sep 2012}, pages = {2}, abstract = {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.}, language = {en} } @inproceedings{GalibarovDendorferChristensen, author = {Galibarov, Pavel E. and Dendorfer, Sebastian and Christensen, Soeren Toerholm}, title = {On modelling spine curvature dependent on muscular and external forces in multibody dynamics system}, series = {International Society of Biomechanics (ISB), 13th congress, 2011, Brussels, Belgium}, booktitle = {International Society of Biomechanics (ISB), 13th congress, 2011, Brussels, Belgium}, pages = {2}, abstract = {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.}, language = {en} } @inproceedings{RasmussenBichlerChristensenetal., author = {Rasmussen, John and Bichler, R. and Christensen, Soeren Toerholm and Wirix-Speetjens, Roel and Dendorfer, Sebastian and Renkawitz, Tobias}, title = {Subject-specific Musculoskeletal Simulation of Hip Dislocation Risk in Activities of Daily Living}, series = {Proceedings of the 2011 ORS Annual Meeting, Long Beach, CA.}, booktitle = {Proceedings of the 2011 ORS Annual Meeting, Long Beach, CA.}, number = {Paper No. 306}, language = {en} } @inproceedings{RobieDendorferRasmussenetal., author = {Robie, Bruce and Dendorfer, Sebastian and Rasmussen, John and Christensen, Soeren Toerholm}, title = {Axial Rotation Requires Greatest Load in Multifidus Muscle - Potential Association with Low Back Pain?}, series = {Annual Meeting of the AANS/CNS Section on Disorders of the Spine and Peripheral Nerves, 2011, Phoenix, Arizona}, booktitle = {Annual Meeting of the AANS/CNS Section on Disorders of the Spine and Peripheral Nerves, 2011, Phoenix, Arizona}, language = {en} } @inproceedings{GalibarovDendorferRasmussen, author = {Galibarov, Pavel E. and Dendorfer, Sebastian and Rasmussen, John}, title = {Two Computational Models of the Lumbar Spine:}, series = {Proceedings of the 2011 ORS Annual Meeting, Long Beach, CA, vol. Marie Curie Initial Training Network "SpineFX"}, booktitle = {Proceedings of the 2011 ORS Annual Meeting, Long Beach, CA, vol. Marie Curie Initial Training Network "SpineFX"}, language = {en} } @article{HausleiterKastratiWesselyetal., author = {Hausleiter, J{\"o}rg and Kastrati, Adnan and Wessely, Rainer and Dibra, Alban and Mehilli, Julinda and Schratzenstaller, Thomas and Graf, Isolde and Renke-Gluszko, Magdalena and Behnisch, Boris and Dirschinger, Josef and Wintermantel, Erich and Sch{\"o}mig, Albert}, title = {Prevention of restenosis by a novel drug-eluting stent system with a dose-adjustable, polymer-free, on-site stent coating}, series = {European Heart Journal - Clinical research}, volume = {26}, journal = {European Heart Journal - Clinical research}, number = {15}, doi = {10.1093/eurheartj/ehi405}, pages = {1475 -- 1481}, abstract = {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.}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {MDR Implementation Status and Lessons Learned from the Past Months: A Notified Body Perspective}, series = {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}, journal = {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}, publisher = {Cambridge Innovation Institute}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {MDR implementation status \& lessons learned}, language = {en} } @article{SinghTerzidis, author = {Singh, Max Diamond and Terzidis, O.}, title = {Introducing Innovation Phase Transition}, series = {International Journal of Innovation Science}, volume = {7}, journal = {International Journal of Innovation Science}, number = {4}, publisher = {Emerald}, issn = {1757-2223}, doi = {10.1108/IJIS-07-04-2015-B003}, pages = {249 -- 262}, abstract = {Innovation diffusion points toward how innovations spread into the market after launch. This paper investigates diffusion dynamics at market entry time and proposes a new evolution pattern at the intersection between inventions and innovations. With this in mind, we initially prove that patent filings correlate with new product introductions in the U.S. spine market. Then we test our new theory supposing that certain patent filing threshold numbers accelerate strong economic returns in terms of innovations. We find that firms hitting certain patent filing thresholds significantly increase their product launches in the mentioned market. Moreover, the results seem to indicate that economic returns of inventions may be measured substantially. Thus, this paper suggests a new research area by utilizing our proposed concept about an Innovation Outcome Trigger Value (IOTV). Furthermore, the implications may also be interesting for practitioners, since we empirically prove that inventive activities turn out to be worthwhile, indeed.}, language = {en} } @article{SinghRussTerzidis, author = {Singh, Max Diamond and Russ, Jochen and Terzidis, Orestis}, title = {The Impact of the ObamaCare Excise Tax on Innovation and Entrepreneurship - Early Empirical Findings}, series = {International Journal of Innovation Science}, volume = {7}, journal = {International Journal of Innovation Science}, number = {2}, publisher = {Emerald}, doi = {10.1260/1757-2223.7.2.75}, pages = {75 -- 90}, abstract = {This study addresses aspects of governmental influence on innovation by analyzing the impact of the ObamaCare excise tax on the medical device industry. We initially give an overview of common approaches to measuring innovativeness and entrepreneurship, empirically assess whether existing metrics are suitable for investigating the innovation performance of the U.S. medical device industry, and define a new measure (firm innovation activity) for entrepreneurship. Then we perform a quantitative analysis to explore the impact of the tax. We analyze more than 60,000 product clearances from 1996 to 2013, using the FDA database. We find a significant relationship between product counts and revenues for one segment. Contrary to the present criticism of the excise tax, we find hardly any noteworthy response in either firm innovation activity or number of products launched in the year after the tax was introduced. The 2013 reduction of new product submissions is well within the limits of typical annual fluctuations observed in previous years. This provides a first indication that the excise tax act did not have a strong impact on innovative activities through the present.}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {European Union MDRs impact on device manufacturers: Reprocessing of surgical invasive devices, critical timeliness and technical documentation requirements under MDR}, series = {The validation of sterile medical devices: sterilization, packaging, biocompatibility, toxicology and reprocessing, Amsterdam, 26.03. - 28.03.2019 [Veranstalter: Nelson Labs ; Sterigenics]}, journal = {The validation of sterile medical devices: sterilization, packaging, biocompatibility, toxicology and reprocessing, Amsterdam, 26.03. - 28.03.2019 [Veranstalter: Nelson Labs ; Sterigenics]}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {Challenges to innovate in the medical device industry under the light of the new EU MDR : a notified body perspective}, series = {Intelligent medical devices - the next disruptor in healthcare ; challenges and oppoertunieties: technical, clinical, regulatory and health economics/market access}, journal = {Intelligent medical devices - the next disruptor in healthcare ; challenges and oppoertunieties: technical, clinical, regulatory and health economics/market access}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {Zus{\"a}tzliche Anforderungen an Produktdaten und technische Dokumentation durch die MDR}, series = {Medizintechnik Kongress 2018: Effizienz in der Medizinprodukteentwicklung vor dem Hintergrund von MDR und IVDR ; Frankfurt am Main, 08.11.2018, [Veranstalter: Velten Consulting \& ILC Consulting]}, journal = {Medizintechnik Kongress 2018: Effizienz in der Medizinprodukteentwicklung vor dem Hintergrund von MDR und IVDR ; Frankfurt am Main, 08.11.2018, [Veranstalter: Velten Consulting \& ILC Consulting]}, language = {de} } @misc{Singh, author = {Singh, Max Diamond}, title = {EU-MDR from a Notified Body Perspective - aktuelle Situation hinsichtlich der Anforderungen zum Lieferantenmanagement}, language = {de} } @misc{Singh, author = {Singh, Max Diamond}, title = {EU Medical Device Regulation: Top Challenges of Orthopedic Manufacturers}, series = {OMTEC 2019 : 15th Annual Orthopedic Manufacturing \& Technology Exposition and Conference, Chicago, 11.6.2019}, journal = {OMTEC 2019 : 15th Annual Orthopedic Manufacturing \& Technology Exposition and Conference, Chicago, 11.6.2019}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {Conformity Assessment Procedure MDR}, series = {MDR Training: Person Responsible for Regulatory Compliance Course, 24.-25.02.2020, Tel Aviv, Obelis Academy}, journal = {MDR Training: Person Responsible for Regulatory Compliance Course, 24.-25.02.2020, Tel Aviv, Obelis Academy}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {Managing Innovation from the Notified Body Perspective - Understanding the 3 C's of EU Regulations to Ensure Product Compliance: Changes, Challenges and Contributions}, series = {3rd annual european medical device and diagnostic product development and management meeting, 12-13 February 2019, Brussels}, journal = {3rd annual european medical device and diagnostic product development and management meeting, 12-13 February 2019, Brussels}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {Notified body feedback: PSUR Forms. Post Market Surveillance \& Vigilance}, series = {MedTech Summit 2020: EU MDR \& IVDR: the end is in sight, Dublin/virtual, 20.-26.06.2020}, journal = {MedTech Summit 2020: EU MDR \& IVDR: the end is in sight, Dublin/virtual, 20.-26.06.2020}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {MDR - Die neuen rechtlichen Bedingungen f{\"u}r H{\"a}ndler und Hersteller: aus der Sicht einer benannten Stelle}, series = {MEGRA Jahrestagung. - Wien, 18.05.2020 [Veranstalter: Mitteleurop{\"a}ische Gesellschaft f{\"u}r Regulatory Affairs]}, journal = {MEGRA Jahrestagung. - Wien, 18.05.2020 [Veranstalter: Mitteleurop{\"a}ische Gesellschaft f{\"u}r Regulatory Affairs]}, language = {de} } @misc{Singh, author = {Singh, Max Diamond}, title = {Innovation challenges for orthopedic device manufacturers under the new EU MDR}, series = {ORS (Orthopaedic Research Society) Annual Meeting. - Phoenix, Arizona, 08. - 11.02.2020}, journal = {ORS (Orthopaedic Research Society) Annual Meeting. - Phoenix, Arizona, 08. - 11.02.2020}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {KARL STORZ Navigation Panel Unit - Navigation for ENT surgery}, series = {FESS 2010 : International Workshop on FESS ; Lectures \& Live Surgery. - Royal Pearl Hospital, Tiruchirappalli (Indien), 10.-11.04.2010}, journal = {FESS 2010 : International Workshop on FESS ; Lectures \& Live Surgery. - Royal Pearl Hospital, Tiruchirappalli (Indien), 10.-11.04.2010}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {Medical Device Regulation}, series = {Forum MedTech Pharma: Start-ups in der Medizintechnik: Besonderheiten und Fallbeispiele, M{\"u}nchen, 17.7.2019}, journal = {Forum MedTech Pharma: Start-ups in der Medizintechnik: Besonderheiten und Fallbeispiele, M{\"u}nchen, 17.7.2019}, language = {de} } @misc{Singh, author = {Singh, Max Diamond}, title = {Market Access for Devices under MDD and MDR: Obligations for Manufacturers}, series = {OSMA - Orthopedic Surgical Manufacturers Association, Winter Educational Program - virtual}, journal = {OSMA - Orthopedic Surgical Manufacturers Association, Winter Educational Program - virtual}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {Innovationsmanagement}, language = {de} } @misc{Singh, author = {Singh, Max Diamond}, title = {General Overview of the Medical Device Regulation}, series = {MDR-Roadshow - T{\"U}V S{\"U}D MHS, India}, journal = {MDR-Roadshow - T{\"U}V S{\"U}D MHS, India}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {Stakeholder view on Post Market Surveillance under the EU MDR: Timelines, Compliance and Requirements ; Post Market Surveillance \& Vigilance}, series = {MedTech summit 2020: EU MDR \& IVDR: the end ist in sight, 22.-26.06.2020, Dublin/virtual}, journal = {MedTech summit 2020: EU MDR \& IVDR: the end ist in sight, 22.-26.06.2020, Dublin/virtual}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {Quality in Medical Device Innovation for Start-ups, SME, and large enterprises through the new Medical Device Regulation}, series = {3rd European QA Conference, Dublin, 06. - 08.11.2019}, journal = {3rd European QA Conference, Dublin, 06. - 08.11.2019}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {Technical Documentation MDR / IVDR, including the Declaration of Conformity}, series = {MDR Training: Person Responsible for Regulatory Compliance, 24.-25.02.2020, Tel Aviv, Obelis Academy}, journal = {MDR Training: Person Responsible for Regulatory Compliance, 24.-25.02.2020, Tel Aviv, Obelis Academy}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {Notified Body Viewpoint : Preparing for MDR/IVDR}, series = {MDR/IVDR - Status Report from Stakeholders. Where are we now in November 2018? - Bern, 22.11.2018 - [Veranstalter: RAPS : Regulatory Affairs Professionals Society]}, journal = {MDR/IVDR - Status Report from Stakeholders. Where are we now in November 2018? - Bern, 22.11.2018 - [Veranstalter: RAPS : Regulatory Affairs Professionals Society]}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {Reclassification of Orthopedic Devices per the Medical Device Regulation}, series = {OSMA Winter Educational Program, St. Petersburg/USA, 2019. - [Veranstalter: Orthopedic Surgical Manufacturers Association (OSMA)]}, journal = {OSMA Winter Educational Program, St. Petersburg/USA, 2019. - [Veranstalter: Orthopedic Surgical Manufacturers Association (OSMA)]}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {Strategies to Navigate to the EU MDR and Clinical Requirements}, series = {Regulatory Affairs Professionals Society (RAPS): Session 1 - Tampa, Florida 2019}, journal = {Regulatory Affairs Professionals Society (RAPS): Session 1 - Tampa, Florida 2019}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {Herausforderungen der Medizinprodukteindustrie bei der Internationalisierung}, series = {Studienwoche an der HNU (Hochschule Neu-Ulm) 2020}, journal = {Studienwoche an der HNU (Hochschule Neu-Ulm) 2020}, language = {de} } @misc{Singh, author = {Singh, Max Diamond}, title = {Technical Aspects for Navigated Sinus Surgery}, series = {4th Workshop on Endoscopic Surgery of the Maxillary Sinus and Navigation, T{\"u}bingen University Hospital, 2009}, journal = {4th Workshop on Endoscopic Surgery of the Maxillary Sinus and Navigation, T{\"u}bingen University Hospital, 2009}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {Overview of the Medical Device Regulation (MDR)}, language = {en} } @article{Singh, author = {Singh, Max Diamond}, title = {Orthopedic Medical Devices Under The Scope of The EU MDR}, series = {MedTech Outlook}, journal = {MedTech Outlook}, language = {en} } @misc{SinghSchlagintweitReischle2020, author = {Singh, Max Diamond and Schlagintweit, S. and Reischle, G.}, title = {Additive-Manufactured Orthopedic Implants Under MDR}, number = {08.11.20}, year = {2020}, language = {en} } @misc{Singh, author = {Singh, Max Diamond}, title = {Joint NB-Position Paper on Spinal Classification per the MDR}, language = {en} } @phdthesis{Singh, author = {Singh, Max Diamond}, title = {Aspects of the Dynamics of Spine Surgery Technologies: Assessing the Reality of Innovation and Entrepreneurship in the U.S. Medical Device Industry}, publisher = {Karlsruhe Institute of Technology}, address = {Karlsruhe}, pages = {xix, 254 S.}, language = {en} } @article{OttRosengarthDoenitzetal., author = {Ott, Christian and Rosengarth, Katharina and Doenitz, Christian and Hoehne, Julius and Wendl, Christina and Dodoo-Schittko, Frank and Lang, Elmar Wolfgang and Schmidt, Nils Ole and Goldhacker, Markus}, title = {Preoperative Assessment of Language Dominance through Combined Resting-State and Task-Based Functional Magnetic Resonance Imaging}, series = {Journal of personalized medicine}, volume = {11}, journal = {Journal of personalized medicine}, number = {12}, publisher = {MDPI}, doi = {10.3390/jpm11121342}, abstract = {Brain lesions in language-related cortical areas remain a challenge in the clinical routine. In recent years, the resting-state fMRI (RS-fMRI) was shown to be a feasible method for preoperative language assessment. The aim of this study was to examine whether language-related resting-state components, which have been obtained using a data-driven independent-component-based identification algorithm, can be supportive in determining language dominance in the left or right hemisphere. Twenty patients suffering from brain lesions close to supposed language-relevant cortical areas were included. RS-fMRI and task-based (TB-fMRI) were performed for the purpose of preoperative language assessment. TB-fMRI included a verb generation task with an appropriate control condition (a syllable switching task) to decompose language-critical and language-supportive processes. Subsequently, the best fitting ICA component for the resting-state language network (RSLN) referential to general linear models (GLMs) of the TB-fMRI (including models with and without linguistic control conditions) was identified using an algorithm based on the Dice index. Thereby, the RSLNs associated with GLMs using a linguistic control condition led to significantly higher laterality indices than GLM baseline contrasts. LIs derived from GLM contrasts with and without control conditions alone did not differ significantly. In general, the results suggest that determining language dominance in the human brain is feasible both with TB-fMRI and RS-fMRI, and in particular, the combination of both approaches yields a higher specificity in preoperative language assessment. Moreover, we can conclude that the choice of the language mapping paradigm is crucial for the mentioned benefits.}, language = {en} } @misc{GreenleeAnstisRosengarthetal., author = {Greenlee, Mark W. and Anstis, Stuart and Rosengarth, Katharina and Goldhacker, Markus and Brandl-R{\"u}hle, Sabine and Plank, Tina}, title = {Neural correlates of perceptual filling-in: fMRI evidence in the foveal projection zone of patients with central scotoma}, series = {Journal of Vision / Vision Sciences Society Annual Meeting Abstract}, volume = {12}, journal = {Journal of Vision / Vision Sciences Society Annual Meeting Abstract}, number = {9}, publisher = {ARVO}, issn = {1534-7362}, doi = {10.1167/12.9.1303}, abstract = {Patients with juvenile retinal dystrophy often report that they are unaware of their central scotoma, suggesting the presence of perceptual filling-in. We used functional Magnetic Resonance Imaging (fMRI) to determine possible neural correlates of perceptual filling-in in patients with retinal distrophy and clinically established central scotoma in both eyes. The data of 5 patients (Stargardt disease, cone-rod dystrophy; mean age 45 yrs; scotoma diameter 10-20°) and of 5 normally sighted controls were analyzed. Fixation behaviour and perimetry were measured with a Nidek microperimeter. Magnetic resonance imaging was performed using a Siemens 3T Allegra scanner. We stimulated the central visual field (30 deg) with a vertically oriented, low spatial frequency (1 c/deg) high-contrast sinewave grating that was either a) continuous, or b) was interrupted by a central grey disk. The disk was either slightly larger than the scotoma (detectable on 75\% of trials) or slightly smaller (detectable on 25\% of trials). To control for attention, an eccentric fixation task was performed during scanning. Data were analyzed using SPM8 (GLM with ROI analysis to obtain percent signal change for foveal projection zone). Results: for all patients, the BOLD signal in the foveal projection area was significantly higher for the small disk (i.e., condition leading to complete filling-in) than for the large disk (i.e., no filling-in). This effect was absent in the control subjects. Our findings support the existence of an active neural process that leads to filling-in in patients with central visual field scotomata.}, language = {en} } @article{GoldhackerRosengarthPlanketal., author = {Goldhacker, Markus and Rosengarth, Katharina and Plank, Tina and Greenlee, Mark W.}, title = {The effect of feedback on performance and brain activation during perceptual learning}, series = {Vision research}, volume = {99}, journal = {Vision research}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1878-5646}, doi = {10.1016/j.visres.2013.11.010}, pages = {99 -- 110}, abstract = {We investigated the role of informative feedback on the neural correlates of perceptual learning in a coherent-motion detection paradigm. Stimulus displays consisted of four patches of moving dots briefly (500 ms) presented simultaneously, one patch in each visual quadrant. The coherence level was varied in the target patch from near threshold to high, while the other three patches contained only noise. The participants judged whether coherent motion was present or absent in the target patch. To guarantee central fixation, a secondary RSVP digit-detection task was performed at fixation. Over six training sessions subjects learned to detect coherent motion in a predefined quadrant (i.e., the learned location). Half of our subjects were randomly assigned to the feedback group, where they received informative feedback after each response during training, whereas the other group received non-informative feedback during training that a response button was pressed. We investigated whether the presence of informative feedback during training had an influence on the learning success and on the resulting BOLD response. Behavioral data of 24 subjects showed improved performance with increasing practice. Informative feedback promoted learning for motion displays with high coherence levels, whereas it had little effect on learning for displays with near-threshold coherence levels. Learning enhanced fMRI responses in early visual cortex and motion-sensitive area MT+ and these changes were most pronounced for high coherence levels. Activation in the insular and cingulate cortex was mainly influenced by coherence level and trained location. We conclude that feedback modulates behavioral performance and, to a lesser extent, brain activation in areas responsible for monitoring perceptual learning.}, language = {en} } @article{GreenleeRosengarthSchmalhoferetal., author = {Greenlee, Mark W. and Rosengarth, Katharina and Schmalhofer, Carolin and Goldhacker, Markus and Brandl-R{\"u}hle, Sabine and Plank, Tina}, title = {Perceptual learning in patients with central scotomata due to hereditary and age-related macular dystrophy}, series = {Journal of Vision}, volume = {14}, journal = {Journal of Vision}, number = {10}, publisher = {ARVO}, doi = {10.1167/14.10.666}, pages = {666}, abstract = {Hereditary and age-related forms of macular dystrophy (MD) are characterized by loss of cone function in the fovea, leading to central scotomata and eccentric fixation at the so-called preferred retinal locus (PRL). We investigated whether perceptual learning enhances visual abilities at the PRL. We also determined the neural correlates (3-Tesla fMRI) of learning success. Twelve MD patients (eight with age-related macular dystrophy, four with hereditary macular dystrophies) were trained on a texture discrimination task (TDT) over six days. Patients underwent three fMRI sessions (before, during and after training) while performing the TDT (target at PRL or opposite PRL). Reading speed, visual acuity (Vernier task) and contrast sensitivity were also assessed before and after training. With one exception, all patients showed improved performance (i.e. significant decrease in stimulus onset asynchronies and reaction times, significant increase in hit rates) on the TDT. Eight patients also showed moderate increases in reading speed, six patients showed improved thresholds in contrast sensitivity and nine patients showed improved thresholds in a vernier visual acuity task after TDT training. We found an increase in BOLD response in the projections zone of the PRL in the primary visual cortex in nine of twelve patients after training. The change in fMRI signal correlated (r = .8; p = .02) with the patients{\^a}€™ performance enhancements when the target was in the PRL. The results suggest that perceptual learning can enhance eccentric vision and cortical processing in MD patients.}, language = {en} } @article{GoldhackerRosengarthAnstisetal., author = {Goldhacker, Markus and Rosengarth, Katharina and Anstis, Stuart and Wirth, Anna and Plank, Tina and Greenlee, Mark W.}, title = {FMRI evidence for perceptual filling-in in patients with macular dystrophy}, series = {Perception}, volume = {42}, journal = {Perception}, issn = {1468-4233}, pages = {72 -- 73}, language = {en} } @article{PlankRosengarthSchmalhoferetal., author = {Plank, Tina and Rosengarth, Katharina and Schmalhofer, Carolin and Goldhacker, Markus and Brandl-R{\"u}hle, Sabine and Greenlee, Mark W.}, title = {Perceptual learning in patients with macular degeneration}, series = {Frontiers in psychology}, volume = {5}, journal = {Frontiers in psychology}, publisher = {Frontiers Research Foundation}, address = {Lausanne}, issn = {1664-1078}, doi = {10.3389/fpsyg.2014.01189}, pages = {1 -- 14}, abstract = {Patients with age-related macular degeneration (AMD) or hereditary macular dystrophies (JMD) rely on an efficient use of their peripheral visual field. We trained eight AMD and five JMD patients to perform a texture-discrimination task (TDT) at their preferred retinal locus (PRL) used for fixation. Six training sessions of approximately one hour duration were conducted over a period of approximately 3 weeks. Before, during and after training twelve patients and twelve age-matched controls (the data from two controls had to be discarded later) took part in three functional magnetic resonance imaging (fMRI) sessions to assess training-related changes in the BOLD response in early visual cortex. Patients benefited from the training measurements as indexed by significant decrease (p = 0.001) in the stimulus onset asynchrony (SOA) between the presentation of the texture target on background and the visual mask, and in a significant location specific effect of the PRL with respect to hit rate (p = 0.014). The following trends were observed: (i) improvement in Vernier acuity for an eccentric line-bisection task; (ii) positive correlation between the development of BOLD signals in early visual cortex and initial fixation stability (r = 0.531); (iii) positive correlation between the increase in task performance and initial fixation stability (r = 0.730). The first two trends were non-significant, whereas the third trend was significant at p = 0.014, Bonferroni corrected. Consequently, our exploratory study suggests that training on the TDT can enhance eccentric vision in patients with central vision loss. This enhancement is accompanied by a modest alteration in the BOLD response in early visual cortex.}, language = {en} } @article{GreenleeRosengarthSchmalhoferetal., author = {Greenlee, Mark W. and Rosengarth, Katharina and Schmalhofer, Caroline and Goldhacker, Markus and Brandl-R{\"u}hle, Sabine and Plank, Tina}, title = {Perceptual learning in patients with central scotomata due to hereditary and age-related macular dystrophy}, series = {Journal of Vision}, volume = {14}, journal = {Journal of Vision}, number = {10}, publisher = {ARVO}, issn = {1468-4233}, doi = {10.1167/14.10.666}, abstract = {Hereditary and age-related forms of macular dystrophy (MD) are characterized by loss of cone function in the fovea, leading to central scotomata and eccentric fixation at the so-called preferred retinal locus (PRL). We investigated whether perceptual learning enhances visual abilities at the PRL. We also determined the neural correlates (3-Tesla fMRI) of learning success. Twelve MD patients (eight with age-related macular dystrophy, four with hereditary macular dystrophies) were trained on a texture discrimination task (TDT) over six days. Patients underwent three fMRI sessions (before, during and after training) while performing the TDT (target at PRL or opposite PRL). Reading speed, visual acuity (Vernier task) and contrast sensitivity were also assessed before and after training. With one exception, all patients showed improved performance (i.e. significant decrease in stimulus onset asynchronies and reaction times, significant increase in hit rates) on the TDT. Eight patients also showed moderate increases in reading speed, six patients showed improved thresholds in contrast sensitivity and nine patients showed improved thresholds in a vernier visual acuity task after TDT training. We found an increase in BOLD response in the projections zone of the PRL in the primary visual cortex in nine of twelve patients after training. The change in fMRI signal correlated (r = .8; p = .02) with the patients{\^a}€™ performance enhancements when the target was in the PRL. The results suggest that perceptual learning can enhance eccentric vision and cortical processing in MD patients.}, language = {en} } @article{ReichHornberger, author = {Reich, Sven and Hornberger, Helga}, title = {The effect of multicolored machinable ceramics on the esthetics of all-ceramic crowns}, series = {Journal of Prosthetic Dentistry}, volume = {88}, journal = {Journal of Prosthetic Dentistry}, number = {1}, pages = {44 -- 49}, abstract = {Statement of problems: Computer-aided design/computer-assisted machining systems offer the possibility of fabricating restorations from one machinable ceramic block. Whether multishaded blocks improve esthetic results and are a viable alternative to individually stained ceramics has not been fully determined. Purpose: The aim of this investigation was to examine the effect of multishaded blocks on the esthetic appearance of all-ceramic CEREC crowns and compare these crowns with single-shade and stained restorations. Material and methods: Ten subjects were included in this study. For each subject, 6 different crowns were milled with the use of a CEREC machine. One crown was milled from each of the following machinable ceramic materials: CEREC Vitablocs Mark II in classic colors; Vitablocs Mark II in 3D-Master colors; Vitablocs Mark II in either classic or 3D-Master colors, with additional staining; Megadenta Bloxx multishaded; Mark II experimental multilayer; and an experimental multilayer leucite ceramic. Three independent examiners assessed the esthetic appearance of crowns fabricated to match each subject's anterior tooth shade. A scale of 1 to 6 was used to score the shade match and esthetic adaptation of each crown, with 1 representing excellent characteristics and 3.5 serving as the threshold for clinical acceptability. The examiners' scores were averaged, and the mean values were analyzed with the Wilcoxon signed rank test (P 87\% in both groups. There was a significant difference between the navigated and the conventional groups' Harris hip scores six weeks after surgery (p = 0.010). There were no significant differences with respect to any clinical outcome at six months and one year of follow-up. The navigated 'femur-first' technique improves the potential ROM for ADL without prosthetic impingement, although there was no observed clinical difference between the two treatment groups.}, subject = {H{\"u}ftgelenkprothese}, language = {en} } @article{WeberWeberWoerneretal., author = {Weber, Markus and Weber, Tim A. and Woerner, Michael and Craiovan, Benjamin and Worlicek, Michael and Winkler, Sebastian and Grifka, Joachim and Renkawitz, Tobias}, title = {The impact of standard combined anteversion definitions on gait and clinical outcome within one year after total hip arthroplasty}, series = {International Orthopaedics}, volume = {39}, journal = {International Orthopaedics}, number = {12}, doi = {10.1007/s00264-015-2777-8}, pages = {2323 -- 2333}, abstract = {Different target areas within the concept of combined cup and stem anteversion have been published for total hip arthroplasty (THA). We asked whether component positioning according to eight standard combined anteversion rules is associated with (1) more physiological gait patterns, (2) higher improvement of gait variables and (3) better clinical outcome after THA.In a prospective clinical study, 60 patients received cementless THA through an anterolateral MIS approach in a lateral decubitus position. Six weeks postoperatively, implant position was analysed using 3D-CT by an independent external institute. Preoperatively, six and 12 months postoperatively range of motion, normalized walking speed and hip flexion symmetry index were measured using 3D motion-capture gait analysis. Patient-related outcome measures (HHS, HOOS, EQ-5D) were obtained by an observer blinded to 3D-CT results. Eight combined anteversion definitions and Lewinnek's "safe zone" were evaluated regarding their impact on gait patterns and clinical outcome.Combined cup and stem anteversion according to standard combined anteversion definitions as well as cup placement within Lewinnek's "safe zone" did not influence range of motion, normalized walking speed and/or hip flexion symmetry index six and 12 months after THA. Similarly, increase of gait parameters within the first year after THA was comparable between all eight combined anteversion rules. Clinical outcome measures like HHS, HOOS and EQ-5D did not show any benefit for either of the combined anteversion definitions.Standard combined cup and stem anteversion rules do not improve postoperative outcome as measured by gait analysis and clinical scores within one year after THA.}, subject = {H{\"u}ftgelenkprothese}, language = {en} } @article{WeberAlMunajjedVerkerkeetal., author = {Weber, Tim and Al-Munajjed, Amir Andreas and Verkerke, Gijsbertus Jacob and Dendorfer, Sebastian and Renkawitz, Tobias}, title = {Influence of minimally invasive total hip replacement on hip reaction forces and their orientations}, series = {Journal of Orthopaedic Research}, volume = {32}, journal = {Journal of Orthopaedic Research}, number = {12}, doi = {10.1002/jor.22710}, pages = {1680 -- 1687}, abstract = {Minimally invasive surgery (MIS) is becoming increasingly popular. Supporters claim that the main advantages of MIS total hip replacement (THR) are less pain and a faster rehabilitation and recovery. Critics claim that safety and efficacy of MIS are yet to be determined. We focused on a biomechanical comparison between surgical standard and MIS approaches for THR during the early recovery of patients. A validated, parameterized musculoskeletal model was set to perform a squat of a 50th percentile healthy European male. A bilateral motion was chosen to investigate effects on the contralateral side. Surgical approaches were simulated by excluding the incised muscles from the computations. Resulting hip reaction forces and their symmetry and orientation were analyzed. MIS THR seemed less influential on the symmetry index of hip reaction forces between the operated and nonoperated leg when compared to the standard lateral approach. Hip reaction forces at peak loads of the standard transgluteal approach were 24\% higher on the contralateral side when compared to MIS approaches. Our results suggest that MIS THR contributes to a greater symmetry of hip reaction forces in absolute value as well as force-orientation following THR.}, subject = {H{\"u}ftgelenkprothese}, language = {en} } @article{PenzkoferBarnsteinerDendorfer, author = {Penzkofer, Rainer and Barnsteiner, K. and Dendorfer, Sebastian}, title = {The influence of age, shoe type and kicking direction on the severity of head trauma}, series = {Journal of Forensic Biomechanics}, volume = {5}, journal = {Journal of Forensic Biomechanics}, number = {1}, doi = {10.4172/2090-2697.1000116}, abstract = {In the last few years, increasingly kicks to the head were observed as a criminal offense. This study examined the influence of age, shoe type and kicking direction on the severity of head trauma. Male test persons were divided into two groups "Old" and "Young". Both groups were equipped with light sneakers and combat boots. A standard laboratory crash dummy was used to simulate the victim's body. First, the dummy's head, free floating above the ground, was kicked vertically. Second, the dummy's head was kicked horizontally. Established injury criteria were used to quantify the injury risk. No influence concerning the type of foot wear and no difference between the groups "Old" and "Young" could be found. For all analyses, kicking vertically generally lead to a higher risk for the subject compared to kicking horizontally. In this study, only the integral effect of the kicks could be analyzed. A detailed injury pattern cannot directly be derived from the data. Nevertheless, the presented data show the massive potential of injuries associated with head kicks.}, subject = {Kopfverletzung}, language = {en} } @article{DendorferWeberKennedy, author = {Dendorfer, Sebastian and Weber, Tim and Kennedy, O.}, title = {Musculoskeletal modeling for hip replacement outcome analyses and other applications}, series = {The Journal of the American Academy of Orthopaedic Surgeons}, volume = {22}, journal = {The Journal of the American Academy of Orthopaedic Surgeons}, number = {4}, doi = {10.5435/JAAOS-22-04-268}, pages = {268 -- 269}, subject = {H{\"u}ftgelenkprothese}, language = {en} }