@article{AuerKurbowitschSuessetal., author = {Auer, Simon and Kurbowitsch, Simone and S{\"u}ß, Franz and Renkawitz, Tobias and Krutsch, Werner and Dendorfer, Sebastian}, title = {Mental stress reduces performance and changes musculoskeletal loading in football-related movements}, series = {Science and Medicine in Football}, volume = {5}, journal = {Science and Medicine in Football}, number = {4}, publisher = {Taylor \& Francis}, doi = {10.1080/24733938.2020.1860253}, pages = {323 -- 329}, abstract = {Purpose: Football players have a high risk of leg muscle injuries, especially when exposed to mental stress. Hence, this study investigated the musculoskeletal response of elite youth football players during highly dynamic movements under stress. The hypothesis is that mental stress reduces performance and changes the muscular forces exerted. Materials \& methods: Twelve elite youth football players were subjected to mental stress while performing sports-specific change-of-direction movements. A modified version of the d2 attention test was used as stressor. The kinetics are computed using inverse dynamics. Running times and exerted forces of injury-prone muscles were analysed. Results: The stressor runs were rated more mentally demanding by the players (p = 0.006, rs = 0.37) with unchanged physical demand (p = 0.777, rs = 0.45). This resulted in 10\% longer running times under stress (p < 0.001, d = -1.62). The musculoskeletal analysis revealed higher peak muscle forces under mental stress for some players but not for others. Discussion: The study shows that motion capture combined with musculoskeletal computation is suitable to analyse the effects of stress on athletes in highly dynamic movements. For the first time in football medicine, our data quantifies an association between mental stress with reduced football players' performance and changes in muscle force.}, language = {en} } @article{PutzerEhrlichRasmussenetal., author = {Putzer, Michael and Ehrlich, Ingo and Rasmussen, John and Gebbeken, Norbert and Dendorfer, Sebastian}, title = {Sensitivity of lumbar spine loading to anatomical parameters}, series = {Journal of Biomechanics}, volume = {49}, journal = {Journal of Biomechanics}, number = {6}, publisher = {Elsevier Science}, doi = {10.1016/j.jbiomech.2015.11.003}, pages = {953 -- 958}, abstract = {Musculoskeletal simulations of lumbar spine loading rely on a geometrical representation of the anatomy. However, this data has an inherent inaccuracy. This study evaluates the influence of defined geometrical parameters on lumbar spine loading utilising five parametrised musculoskeletal lumbar spine models for four different postures. The influence of the dimensions of vertebral body, disc, posterior parts of the vertebrae as well as the curvature of the lumbar spine was studied. Additionally, simulations with combinations of selected parameters were conducted. Changes in L4/L5 resultant joint force were used as outcome variable. Variations of the vertebral body height, disc height, transverse process width and the curvature of the lumbar spine were the most influential. These parameters can be easily acquired from X-rays and should be used to morph a musculoskeletal lumbar spine model for subject-specific approaches with respect to bone geometry. Furthermore, the model was very sensitive to uncommon configurations and therefore, it is advised that stiffness properties of discs and ligaments should be individualised.}, subject = {Wirbels{\"a}ule}, language = {en} } @article{DendorferHammerLenich, author = {Dendorfer, Sebastian and Hammer, Joachim and Lenich, Andreas}, title = {Characterisation and testing of biomaterials}, series = {Technology and Health Care}, volume = {19}, journal = {Technology and Health Care}, number = {5}, doi = {10.3233/THC-2011-0644}, pages = {357 -- 371}, subject = {Biomaterial}, language = {en} } @inproceedings{PutzerGalibarovDendorfer, author = {Putzer, Michael and Galibarov, Pavel E. and Dendorfer, Sebastian}, title = {Influence of vertebral parameters on lumbar spine loading}, series = {Pre-meeting SpineFX, Eurospine 2013, Liverpool, UK}, booktitle = {Pre-meeting SpineFX, Eurospine 2013, Liverpool, UK}, language = {en} } @inproceedings{DendorferPenzkofer, author = {Dendorfer, Sebastian and Penzkofer, Rainer}, title = {Experimentelle Untersuchung der Belastungen im Kopf beim Treten}, series = {Fachsymposium "Treten gegen den Kopf", April 2013, N{\"u}rnberg}, booktitle = {Fachsymposium "Treten gegen den Kopf", April 2013, N{\"u}rnberg}, language = {de} } @inproceedings{Dendorfer, author = {Dendorfer, Sebastian}, title = {Einf{\"u}hrung in die Mechanik}, series = {Biomechanik Workshop, Klinikum Bad Abbach, Nov. 2013}, booktitle = {Biomechanik Workshop, Klinikum Bad Abbach, Nov. 2013}, language = {de} } @inproceedings{Dendorfer, author = {Dendorfer, Sebastian}, title = {Innovationen in der Medizintechnik}, series = {Oberpfalztag Weiherhammer, Nov. 2013}, booktitle = {Oberpfalztag Weiherhammer, Nov. 2013}, language = {de} } @article{HoenickaLehleJacobsetal., author = {Hoenicka, M. and Lehle, Karla and Jacobs, V. R. and Dendorfer, Sebastian and Kostorz, A. and Schmid, F. X. and Birnbaum, D. E.}, title = {Mechanical and seeding properties of human umbilical vein - a potential scaffold for a tissue-engineered vessel graft}, series = {The Thoracic and Cardiovascular Surgeon}, volume = {55}, journal = {The Thoracic and Cardiovascular Surgeon}, number = {S 1}, publisher = {Thieme}, doi = {10.1055/s-2007-967592}, pages = {P_37}, abstract = {Objectives: The mechanical properties and seeding with endothelial cells were investigated in fresh and cryopreserved human umbilical vein. Methods: Human umbilical veins (HUV) were frozen in Euro-Collins/1M DMSO at -1°C/min and stored in liquid nitrogen. Stress-strain relationships of fresh and thawed veins were determined in an uniaxial tension-testing rig. HUV endothelial cells (HUVEC) were seeded onto denuded HUV under static conditions and grown for 3d. Luminal surfaces were analyzed by scanning electron microscopy. Calcein-stained cells were seeded hyperconfluently to determine the cell retention capacity of fresh and cryopreserved veins. Results: The stress-strain relationships of HUV followed a biphasic pattern typical for natural vessels. Neither the failure stress (2.71±0.36 vs. 3.25±0.97 N, n=3) nor the displacement required to achieve failure (9.73±0.9 vs. 7.43±2.07mm, n=3) were altered by cryopreservation. The burst pressure was estimated as approx. 1000mm Hg within the limitations of the uniaxial model. HUVEC seeded onto denuded HUV formed patches (at 9E3 cells per cm2) or an almost confluent endothelium (at 3E4 cells per cm2) within three days. The capacity to retain seeded HUVEC of denuded HUV was not altered by cryopreservation (1.15±0.08E5 vs. 1.26±0.14E5 cells per cm2, n=6). Conclusions: The burst pressure of HUV seems to be sufficiently high for the human arterial circulation and is not altered by cryopreservation. HUVEC can establish a confluent endothelium on denuded HUV. Therefore HUV appears to be a suitable storable scaffold for vascular tissue engineering.}, subject = {Nabelvene}, language = {en} } @article{EnglertAngeleFierlbecketal., author = {Englert, Carsten and Angele, Peter and Fierlbeck, J. and Dendorfer, Sebastian and Schubert, T. and M{\"u}ller, R. and Lienhard, S. and Zellner, J. and Nerlich, Michael and Neumann, Carsten}, title = {Conductive bone substitute material with variable antibiotic delivery}, series = {Der Unfallchirurg}, volume = {110}, journal = {Der Unfallchirurg}, number = {5}, publisher = {Springer}, doi = {10.1007/s00113-007-1229-3}, pages = {408 -- 413}, abstract = {A new bone substitute, consisting of hydroxylapatite and calcium sulphate, was prepared in two formulations and analysed for its mechanical strength and antibiotic elution.The bone substitute PerOssal has osteoconductive and degradable properties. The material has a built-in capillary structure, which results in an immediate fluid uptake. Antibiotics absorbed to the bone substitute resulted in a prolonged release rate. Mechanical strength was investigated by an unconfined compression test up to failure under both wet and dry conditions for both formulations of the bone substitute. Antibiotic release was analysed microbiologically for two antibiotics, vancomycin and gentamicin, over an elution period of 10 days using the agar diffusion method.The drug release analysis resulted in a prolonged release rate of both antibiotics over 10 days. In vitro the amount of gentamicin and vancomycin eluted at day 10. From one pellet still exceeded the minimal inhibitory concentration of most aetiologically important pathogens. Formulation two of the present bone substitute is significantly harder in both wet and dry conditions when compared to formulation one. Both formulations lose strength in the wet condition relative to their performance in the dry condition. However, formulation two is as hard under wet conditions as formulation one is when dry.PerOssal is a suitable new degradable osteoconductive bone substitute that can be loaded with antibiotic solutions, which are released in effective doses over 10 days. The mechanical strength of PerOssal is sufficient to support cancellous bone defects in non-weight-bearing areas or in combination with osteosynthesis.}, subject = {Knochenersatz}, language = {en} } @article{DendorferMaierHammer, author = {Dendorfer, Sebastian and Maier, Hans J{\"u}rgen and Hammer, Josef}, title = {Fatigue damage in cancellous bone: an experimental approach from continuum to micro scale}, series = {Journal of the Mechanical Behavior of Biomedical Materials}, volume = {2}, journal = {Journal of the Mechanical Behavior of Biomedical Materials}, number = {1}, doi = {10.1016/j.jmbbm.2008.03.003}, pages = {113 -- 119}, abstract = {Repeated loadings may cause fatigue fractures in bony structures. Even if these failure types are known, data for trabecular bone exposed to cyclic loading are still insufficient as the majority of fatigue analyses on bone concentrate on cortical structures. Despite its highly anisotropic and inhomogeneous structure, trabecular bone is treated with continuum approaches in fatigue analyses. The underlying deformation and damage mechanism within trabecular specimens are not yet sufficiently investigated. In the present study different types of trabecular bone were loaded in monotonic and cyclic compression. In addition to the measurement of integral specimen deformations, optical deformation analysis was employed in order to obtain strain distributions at different scale levels, from the specimens' surface to the trabeculae level. These measurements allowed for the possibility of linking the macroscopic and microscopic mechanical behaviour of cancellous bone. Deformations were found to be highly inhomogeneous across the specimen. Furthermore strains were found to already localise at very low load levels and after few load cycles. Microcracks in individual trabeculae were induced in the very early stage of cyclic testing. The results provide evidence of the capability of the method to supply essential data on the failure behaviour of individual trabeculae in future studies.}, subject = {Knochen}, language = {en} }