@misc{Raptis, author = {Raptis, Georgios}, title = {HPCs als Basis f{\"u}r den elektronischen Arztausweis}, series = {Smartcard-Workshops, Fraunhofer SIT, 07.02.2006}, journal = {Smartcard-Workshops, Fraunhofer SIT, 07.02.2006}, subject = {Arzt}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Ist die Sicherheit der medizinischen Daten in der Telematik-Infrastruktur zu gew{\"a}hrleisten?}, series = {Kolloquium Wissenschaftlichkeit in der Medizin, Universit{\"a}t Heidelberg, 10.05.2007}, journal = {Kolloquium Wissenschaftlichkeit in der Medizin, Universit{\"a}t Heidelberg, 10.05.2007}, subject = {Telemedizin}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Datenschutz und IT-Sicherheit: Empfehlungen von B{\"A}K und KBV f{\"u}r {\"A}rzte}, series = {AK-Sicherheit des eco-Verband der deutschen Internetwirtschaft e.V., K{\"o}ln, 06.05.2009}, journal = {AK-Sicherheit des eco-Verband der deutschen Internetwirtschaft e.V., K{\"o}ln, 06.05.2009}, subject = {Arztpraxis}, language = {de} } @masterthesis{Raptis, type = {Bachelor Thesis}, author = {Raptis, Georgios}, title = {Klassifikation, Anwendungen und Sicherheitskonzept von Trustcentern}, subject = {Trust Center}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Mechanismen und Einsatzkonzepte von Heilberufsausweis und elektronischer Gesundheitskarte}, series = {Oberseminar im Fachbereich Informatik, Kryptographie und Computeralgebra der TU-Darmstadt, 28.11.2006}, journal = {Oberseminar im Fachbereich Informatik, Kryptographie und Computeralgebra der TU-Darmstadt, 28.11.2006}, subject = {Elektronische Gesundheitskarte}, language = {de} } @article{SchenkelAlbertRaptisetal., author = {Schenkel, Johannes and Albert, J{\"u}rgen and Raptis, Georgios and Butz, Norbert}, title = {Notfalldatenmanagement auf der elektronischen Gesundheitskarte}, series = {e-Health}, journal = {e-Health}, editor = {Duesberg, Felix}, publisher = {medical future verlag}, address = {Solingen}, pages = {64 -- 67}, subject = {Elektronische Gesundheitskarte}, language = {de} } @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} } @misc{Raptis, author = {Raptis, Georgios}, title = {Einsatzm{\"o}glichkeiten des elektronischen Heilberufsausweises}, series = {CAST-Forums, Fraunhofer IGD, 14.09.2006}, journal = {CAST-Forums, Fraunhofer IGD, 14.09.2006}, subject = {Heilberuf}, language = {de} } @article{Raptis, author = {Raptis, Georgios}, title = {App statt Arzt ist kein gutes Motto}, series = {medizin \& technik}, journal = {medizin \& technik}, number = {2}, language = {de} } @inproceedings{Raptis, author = {Raptis, Georgios}, title = {Notfalldaten und Datenerhalt mit der elektronischen Gesundheitskarte.}, series = {Tagungsband 22. Smartcard-Workshop 2012}, booktitle = {Tagungsband 22. Smartcard-Workshop 2012}, publisher = {Fraunhofer-Verlag}, pages = {166}, subject = {Elektronische Gesundheitskarte}, language = {de} } @article{FischerRaptisHorn, author = {Fischer, Uta and Raptis, Georgios and Horn, Lars-Christian}, title = {Bedeutung der Familienanamnese bei Zervixkarzinom}, series = {Zentralblatt f{\"u}r Gyn{\"a}kologie}, volume = {123}, journal = {Zentralblatt f{\"u}r Gyn{\"a}kologie}, doi = {10.1055/s-2001-14791}, pages = {302 -- 307}, abstract = {Fragestellung: Molekulare Analysen haben deutlich gemacht, dass maligne Tumoren durch Ver{\"a}nderungen des Genoms hervorgerufen werden. Im Gegensatz zu den erblich bedingten Tumorerkrankungen sind die Kenntnisse zur Bedeutung famili{\"a}rer Faktoren bei den sog. sporadischen Tumoren, insbesondere beim Zervixkarzinom (CX) begrenzt. Material und Methode: Patientinnen des CX-Registers der Universit{\"a}ts-Frauenklinik wurden retrospektiv bez{\"u}glich der Familienanamnese (FA) analysiert. Als positive FA wurde eine maligne Tumorerkrankung bei einem oder mehreren Verwandten ersten Grades definiert. Es wurde unterschieden, ob es sich um Zervixkarzinome, andere gyn{\"a}kologische Malignome (außer Mammakarzinom) oder eine extragenitale Lokalisation handelte. Diese Daten wurden zum Erkrankungsalter und zum Nachweis pelviner Lymphknotenmetastasen in Beziehung gesetzt. Ergebnisse: 159/737 Frauen (21,6 \%) wiesen eine positive FA auf. In 10,7 \% der F{\"a}lle war mehr als ein Verwandter ersten Grades erkrankt; bei 6,9 \% Angeh{\"o}rige ersten und zweiten Grades. Weibliche Verwandte ersten Grades von 42 Frauen wiesen Malignome des weiblichen Genitaltraktes (außer CX) auf. In 6,9 \% waren die Mutter und/oder die Schwester an einem Zervixkarzinom erkrankt. Das Durchschnittsalter der Patientinnen mit positiver Familienanamnese (FA) unterschied sich nicht von dem derjenigen mit leerer FA, wohl aber bei getrennter Betrachtung nach der Tumorlokalisation. Bez{\"u}glich des Tumorstadiums (pTNM) und der Zahl der Patientinnen mit histologisch nachgewiesenen pelvinen Lymphknotenmetastasen bestand kein Unterschied. Schlussfolgerungen: Die bisherigen Ergebnisse deuten auch beim Zervixkarzinom auf eine famili{\"a}re Belastung hin. Dabei existieren offenbar Familien, in denen mit HPV-assoziierte Pr{\"a}kanzerosen bzw. Tumoren vermehrt auftreten. Besonders gef{\"a}hrdet sind Patientinnen, deren weibliche Anverwandte ersten Grades bereits an einer zervikalen Pr{\"a}kanzerose (besonders CIN III) oder einem invasiven CX erkrankt sind. Diese Frauen sollten einem engmaschigen Screening unterzogen werden.}, subject = {Geb{\"a}rmutterhalskrebs}, language = {de} } @misc{HornRaptisFischer, author = {Horn, Lars-Christian and Raptis, Georgios and Fischer, Uta}, title = {Famili{\"a}res Zervixkarzinom - Erste Ergebnisse}, series = {54. Kongress der Deutschen Gesellschaft f{\"u}r Gyn{\"a}kologie und Geburtshilfe}, journal = {54. Kongress der Deutschen Gesellschaft f{\"u}r Gyn{\"a}kologie und Geburtshilfe}, subject = {Geb{\"a}rmutterhalskrebs}, language = {de} } @inproceedings{Raptis, author = {Raptis, Georgios}, title = {Ein Verfahren zur L{\"o}sung des Problems der kryptographischen Langzeitsicherheit medizinischer Daten, die in einer Infrastruktur gespeichert werden}, series = {BIOSIG-Konferenz 2007, Darmstadt}, booktitle = {BIOSIG-Konferenz 2007, Darmstadt}, abstract = {Medizinische Daten, die - wie derzeit f{\"u}r die Telematik-Infrastruktur nach \S291a SGB V spe-zifiziert - auch außerhalb der physischen Kontrolle der Eigent{\"u}mer oder Ersteller (also z.B. außerhalb von Arztpraxen oder Klinken) auf Servern kryptographisch verschl{\"u}sselt gespeichert werden, m{\"u}ssen sehr lange vertraulich bleiben. Insbesondere darf der technische Betreiber des Servers, der die Daten speichert, keinen Zugriff erlangen. Es kann jedoch keine verl{\"a}ssliche Aussage dahingehend getroffen werden, ob die heute eingesetzten kryp-tographischen Algorithmen in 30 oder 40 Jahren die Vertraulichkeit der medizinischen Daten weiterhin gew{\"a}hrleisten. Es wird ein Verfahren vorgestellt, welches das Problem der langfristigen Sicherheit von verschl{\"u}sselt gespeicherten medizinischen Daten aus kryptographischer Sicht l{\"o}st. Die Anwendung des Verfahrens wird am Beispiel einer nach den derzeit bekannten gematik-Spezifikationen definierten Infrastruktur veranschaulicht. Es wird von einer getrennten Speicherung von verschl{\"u}sselten medizinischen Daten und Schl{\"u}sselmaterial ausgegangen. Die Daten werden an der Datenquelle (Konnektor, z.B. eines Arztes) mit einem Einmalblock (One Time Pad, OTP) verschl{\"u}sselt. Sie sind damit beweisbar sicher verschl{\"u}sselt, weil das One-Time-Pad-Verschl{\"u}sselungsverfahren beweisbar „perfekt geheim" ist. Der OTP-Schl{\"u}ssel wird mit einem symmetrischen Schl{\"u}ssel verschl{\"u}sselt, der wiederum mit den asymmetrischen Schl{\"u}sseln aller Zugriffsberechtigten verschl{\"u}sselt wird. Die kryptographische, technische und organisatorische Sicherheit des Verfahrens sowie seine Voraussetzungen und Kosten werden analysiert.}, subject = {Gesundheitsinformationssystem}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Papierlose Praxis \& Digitalisierung}, series = {6. BMVZ-Praktikerkongress des Bundesverbands Medizinische Versorgungszentren - Gesundheitszentren - Integrierte Versorgung e.V, 12.09.2012 Berlin, zertifiziert von der {\"A}rztekammer Berlin}, journal = {6. BMVZ-Praktikerkongress des Bundesverbands Medizinische Versorgungszentren - Gesundheitszentren - Integrierte Versorgung e.V, 12.09.2012 Berlin, zertifiziert von der {\"A}rztekammer Berlin}, subject = {Arztpraxis}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Sichere Gesundheitsdaten in der Cloud? Technische Voraussetzungen und Regelungen}, series = {8. Rhein-Main Zukunftskongress Krankenhaus \& Partner 2014, Offenbach, 21.2.2014}, journal = {8. Rhein-Main Zukunftskongress Krankenhaus \& Partner 2014, Offenbach, 21.2.2014}, subject = {Cloud Computing}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Vernetzung und ubiquit{\"a}re Informationsverarbeitung - technisch-organisatorischer Datenschutz in der Arztpraxis}, series = {2. Fachtagung der Gesellschaft f{\"u}r Datenschutz und Datensicherheit e.V. (GDD), Berlin, 13.05.2014, zertifiziert von der {\"A}rztekammer Berlin}, journal = {2. Fachtagung der Gesellschaft f{\"u}r Datenschutz und Datensicherheit e.V. (GDD), Berlin, 13.05.2014, zertifiziert von der {\"A}rztekammer Berlin}, subject = {Arztpraxis}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Mobile Szenarien f{\"u}r Anwendungen der eGK}, series = {CAST-Workshop Smartcards, Darmstadt, 25.09.2014}, journal = {CAST-Workshop Smartcards, Darmstadt, 25.09.2014}, subject = {Elektronische Gesundheitskarte}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Die elektronische Gesundheitskarte}, series = {7. Kommunikationsforum "Industry meets Medicine", Olpe, 5.11.2014}, journal = {7. Kommunikationsforum "Industry meets Medicine", Olpe, 5.11.2014}, subject = {Elektronische Gesundheitskarte}, language = {de} } @article{Raptis, author = {Raptis, Georgios}, title = {Computer k{\"o}nnen {\"A}rzte nicht ersetzen}, series = {Technology Review}, volume = {11}, journal = {Technology Review}, pages = {82}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Datenschutzfragen zur Telemedizin}, series = {Fachtagung Datenschutz in der Medizin - Update 2015 I, Hamburg 03.02.2015}, journal = {Fachtagung Datenschutz in der Medizin - Update 2015 I, Hamburg 03.02.2015}, subject = {Telemedizin}, language = {de} } @book{SauerWolfBuchetal., author = {Sauer, S. and Wolf, Th. and Buch, M. and Raptis, Georgios}, title = {Sichere Client-Server-Architekturen f{\"u}r E-Government}, pages = {192}, subject = {Client-Server-Konzept}, language = {de} } @article{Raptis, author = {Raptis, Georgios}, title = {Kryptographischer Langzeitschutz}, series = {KES - The Information Security Journal}, volume = {1}, journal = {KES - The Information Security Journal}, pages = {55 -- 62}, subject = {Kryptologie}, language = {de} } @article{BuschDaumRaptis, author = {Busch, Ch. and Daum, H. and Raptis, Georgios}, title = {Merkmal Iris. K{\"o}nnen diese Augen l{\"u}gen?}, series = {Spektrum der Wissenschaft}, journal = {Spektrum der Wissenschaft}, number = {7}, pages = {81 -- 82}, subject = {Biometrie}, language = {de} } @phdthesis{Raptis, author = {Raptis, Georgios}, title = {Vertraulichkeit von medizinischen Daten in der Telematik-Infrastruktur - Sicherheitsanalyse unter Ber{\"u}cksichtigung von Aspekten der langfristigen Sicherheit}, address = {Heidelberg}, subject = {Medizinische Dokumentation}, language = {de} } @techreport{SchenkelAlbertRaptis, type = {Working Paper}, author = {Schenkel, Johannes and Albert, J{\"u}rgen and Raptis, Georgios}, title = {Arbeitskonzept Notfalldatenmanagement}, subject = {Elektronische Gesundheitskarte}, language = {de} } @article{SchenkelAlbertRaptisetal., author = {Schenkel, Johannes and Albert, J{\"u}rgen and Raptis, Georgios and Butz, Norbert}, title = {Notfalldatensatz: Bessere Unterst{\"u}tzung f{\"u}r den Arzt}, series = {Deutsches {\"A}rzteblatt}, volume = {108}, journal = {Deutsches {\"A}rzteblatt}, number = {19}, pages = {A-1046, B-864, C-864}, subject = {Elektronische Gesundheitskarte}, language = {de} } @inproceedings{MetzlerAachPalmetal., author = {Metzler, V. and Aach, T. and Palm, Christoph and Lehmann, Thomas M.}, title = {Texture Classification of Graylevel Images by Multiscale Cross-Co-Occurrence Matrices}, series = {Proceedings 15th International Conference on Pattern Recognition (ICPR-2000)}, booktitle = {Proceedings 15th International Conference on Pattern Recognition (ICPR-2000)}, doi = {10.1109/ICPR.2000.906133}, pages = {549 -- 552}, abstract = {Local gray level dependencies of natural images can be modelled by means of co-occurrence matrices containing joint probabilities of gray-level pairs. Texture, however, is a resolution-dependent phenomenon and hence, classification depends on the chosen scale. Since there is no optimal scale for all textures we employ a multiscale approach that acquires textural features at several scales. Thus linear and nonlinear scale-spaces are analyzed by multiscale co-occurrence matrices that describe the statistical behavior of a texture in scale-space. Classification is then performed on the basis of texture features taken from the individual scale with the highest discriminatory power. By considering cross-scale occurrences of gray level pairs, the impact of filters on the feature is described and used for classification of natural textures. This novel method was found to improve classification rates of the common co-occurrence matrix approach on standard textures significantly.}, language = {en} } @inproceedings{PalmLehmannSpitzer, author = {Palm, Christoph and Lehmann, Thomas M. and Spitzer, Klaus}, title = {Color Texture Analysis of Moving Vocal Cords Using Approaches from Statistics and Signal Theory}, series = {Advances in Quantitative Laryngoscopy, Voice and Speech Research, Procs. 4th International Workshop, Friedrich Schiller University, Jena}, booktitle = {Advances in Quantitative Laryngoscopy, Voice and Speech Research, Procs. 4th International Workshop, Friedrich Schiller University, Jena}, pages = {49 -- 56}, abstract = {Textural features are applied for detection of morphological pathologies of vocal cords. Cooccurrence matrices as statistical features are presented as well as filter bank analysis by Gabor filters. Both methods are extended to handle color images. Their robustness against camera movement and vibration of vocal cords is evaluated. Classification results due to three in vivo sequences are in between 94.4 \% and 98.9\%. The classification errors decrease if color features are used instead of grayscale features for both statistical and Fourier features}, language = {en} } @inproceedings{PalmFischerLehmannetal., author = {Palm, Christoph and Fischer, B. and Lehmann, Thomas M. and Spitzer, Klaus}, title = {Hierarchische Wasserscheiden-Transformation zur Lippensegmentierung in Farbbildern}, series = {Bildverarbeitung f{\"u}r die Medizin 2000}, booktitle = {Bildverarbeitung f{\"u}r die Medizin 2000}, publisher = {Springer}, address = {Berlin}, doi = {10.1007/978-3-642-59757-2_20}, pages = {106 -- 110}, abstract = {Zur L{\"o}sung komplexer Segmentierungsprobleme wird eine hierarchische und farbbasierte Wasserscheidentransformation vorgestellt. Geringe Modifikationen bez{\"u}glich Startpunktwahl und Flutungsprozess resultieren in signifikanten Verbesserungen der Segmentierung. Das Verfahren wurde zur Lippendetektion in Farbbildsequenzen eingesetzt, die zur quantitativen Beschreibung von Sprechbewegungsabl{\"a}ufen automatisch ausgewertet werden. Die Experimente mit 245 Bildern aus 6 Sequenzen zeigten eine Fehlerrate von 13\%.}, language = {de} } @inproceedings{AurbachWagnerSuessetal., author = {Aurbach, Maximilian and Wagner, Kilian and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Implementation and Validation of Human Kinematics Measured Using IMUs for Musculoskeletal Simulations by the Evaluation of Joint Reaction Forces}, series = {CMBEBIH 2017, Proceedings of the International Conference on Medical and Biological Engineering 2017, Sarajevo, Bosnia and Herzegovina}, volume = {Vol. 62}, booktitle = {CMBEBIH 2017, Proceedings of the International Conference on Medical and Biological Engineering 2017, Sarajevo, Bosnia and Herzegovina}, editor = {Badnjevic, Almir}, publisher = {Springer}, address = {Singapore}, doi = {10.1007/978-981-10-4166-2_31}, pages = {205 -- 211}, abstract = {The gold standard for the analysis of human kinematics and kinetics is a camera-based motion capture system in combination with force measurement platforms. Alternatively, inertial measurement units can be utilized to obtain human kinematics, while ground reaction forces are computed from full body dynamics. This setup represents a system independent from the spatial confinement of a gait laboratory. The aim of this study is the comparison of the two methods by the investigation of lower limb kinematics and the resulting joint reaction forces within the ankle-, knee- and hip joints. For this purpose, human motion during gait was captured simultaneously by both measurement techniques. 13 trials from 8 different test subjects were evaluated in total. IMU data was processed with a quaternion based Kalman Filter. The data sets were implemented into a musculoskeletal simulation program in order to drive a virtual human body model. Each sensor was aligned to the gravitational and magnetic field vectors of the earth. The angles of flexions, extensions and rotations were analyzed to determine kinematic differences. Joint reaction forces defined kinetic dissimilarities. The overall kinematic differences of both models yielded root mean square errors of 7.62°, 6.02°, 4.95°, 2.79°, 2.38° and 3.56° for ankle flexion, subtalar eversion, knee flexion, hip external rotation, hip abduction and hip flexion, respectively. The proximo-distal differences in force peaks between the models yielded overall for the ankle, 57.33 \%Bodyweight(BW) ± 46.86 \%BW (16.66 \%(Maximum peak to peak) ± 13.62 \%) for the knee 37.09 \%BW ± 29.33 \%BW (17.65 \% ± 15.44 \%) and 32.03 \%BW ± 24.33 \%BW (15.6 \% ± 12.54 \%) for the hip. The overall outcome of this work investigated an approach independent of the common setup of the gait laboratory, thus enabling a cheaper and more flexible technology as an alternative. However, kinematic and thus kinetic differences remain rather large. Future work aims to improve the contact criterion for the calculation of the ground reaction forces and the implementation of a full-body calibration algorithm for the IMU system in order to counteract magnetic field disturbances.}, subject = {Bewegungsapparat}, language = {en} } @inproceedings{JungtaeublSchmitzGrossetal., author = {Jungt{\"a}ubl, Dominik and Schmitz, Paul and Gross, Simon and Dendorfer, Sebastian}, title = {FEA of the transiliacal internal fixator as an osteosynthesis of pelvic ring fractures}, series = {CMBEBIH 2017, Proceedings of the International Conference on Medical and Biological Engineering 2017}, booktitle = {CMBEBIH 2017, Proceedings of the International Conference on Medical and Biological Engineering 2017}, editor = {Badnjevic, Almir}, publisher = {Springer}, address = {Singapore}, isbn = {978-981-10-4165-5}, doi = {10.1007/978-981-10-4166-2_32}, pages = {212 -- 217}, abstract = {Common Schanz screw systems can be used to stabilize pelvic ring fractures. In order to accommodate for different patient's requirements, implants can be placed in cranio-caudal direction into the os ilium (T1), or into the supraacetabular bone canal, and thus, in dorso-ventral direction (T2). Whereas both techniques are currently used, no data of the biomechanical behavior is available up to this date. The aim of this study is to analyze, whether T2 shows biomechanical advantages with respect to tissue and implant stresses due to the enlarged bone-implant interface. Forces acting on the pelvis were analyzed using motion capture data of a gait cycle obtained by the utilization of a musculoskeletal simulation program. A three dimensional finite element (FE) model of the pelvis with grayscale-based material properties was generated. The muscle and joint reaction forces at toe-off were applied to the FE model and instable pelvis fractures were implemented. The osteosynthesis systems were positioned within the model in order to enable the comparison between the two different surgical techniques. Stresses and displacements were analyzed for bone tissue, fracture zone and implant. T2 lead to approx. 30\% larger displacements in the fracture zone. Von-Mises stresses were larger for T2 in the implant (80 MPa vs. 227 MPa), whereas T1 leads to larger stresses in the bone tissue (200 MPa vs. 140 MPa). Both implantation techniques showed a good biomechanical behavior. Differences could be found with respect to tissue strains and deformations in the fracture zone. If bone quality or fracture healing are of concern, T2 or T1 should be used, respectively. However, both techniques seem to be applicable for cases with no special requirements. Further analyses aim to investigate the behavior under cyclic loading.}, subject = {Beckenbruch}, 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{LazarevRyabokonHalleretal., author = {Lazarev, Igor A. and Ryabokon, P.V. and Haller, M. and Dendorfer, Sebastian}, title = {Effect of the fractured calcaneus's peripheral fragment displacement on the triceps surae function}, series = {ЖУРНАЛ «ТРАВМА» Ukrainian Trauma Journal}, volume = {2, TOM 16}, journal = {ЖУРНАЛ «ТРАВМА» Ukrainian Trauma Journal}, language = {en} } @article{WeberDendorferGrifkaetal., author = {Weber, Tim A. and Dendorfer, Sebastian and Grifka, Joachim and Verkerke, Gijsbertus Jacob and Renkawitz, Tobias}, title = {Does Computer-Assisted Femur First THR Improve Musculoskeletal Loading Conditions?}, series = {BioMed Research International}, volume = {2015}, journal = {BioMed Research International}, editor = {Takagi, Michiaki}, doi = {10.1155/2015/625317}, pages = {ID 625317}, abstract = {We have developed a novel, computer-assisted operation method for minimal-invasive total hip replacement (THR) following the concept of "femur first/combined anteversion," which incorporates various aspects of performing a functional optimization of the prosthetic stem and cup position (CAS FF). The purpose of this study is to assess whether the hip joint reaction forces and patient's gait parameters are being improved by CAS FF in relation to conventional THR (CON). We enrolled 60 patients (28 CAS FF/32 CON) and invited them for gait analysis at three time points (preoperatively, postop six months, and postop 12 months). Data retrieved from gait analysis was processed using patient-specific musculoskeletal models. The target parameters were hip reaction force magnitude (hrf), symmetries, and orientation with respect to the cup. Hrf in the CAS FF group were closer to a young healthy normal. Phase-shift symmetry showed an increase in the CAS FF group. Hrf orientation in the CAS FF group was closer to optimum, though no edge or rim-loading occurred in the CON group as well. The CAS FF group showed an improved hrf orientation in an early stage and a trend to an improved long-term outcome.}, 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{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} } @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{ZellnerHierlMuelleretal., author = {Zellner, Johannes and Hierl, Katja and Mueller, Michael and Pfeifer, Christian and Berner, Arne and Dienstknecht, Thomas and Krutsch, Werner and Geis, Sebastian and Gehmert, Sebastian and Kujat, Richard and Dendorfer, Sebastian and Prantl, Lukas and Nerlich, Michael and Angele, Peter}, title = {Stem cell-based tissue-engineering for treatment of meniscal tears in the avascular zone}, series = {Journal of Biomedical Materials Research Part B Applied Biomaterials}, volume = {101}, journal = {Journal of Biomedical Materials Research Part B Applied Biomaterials}, number = {7}, editor = {Gilbert, Jeremy}, doi = {10.1002/jbm.b.32922}, pages = {1133 -- 1142}, abstract = {Meniscal tears in the avascular zone have a poor self-healing potential, however partial meniscectomy predisposes the knee for early osteoarthritis. Tissue engineering with mesenchymal stem cells and a hyaluronan collagen based scaffold is a promising approach to repair meniscal tears in the avascular zone. 4 mm longitudinal meniscal tears in the avascular zone of lateral menisci of New Zealand White Rabbits were performed. The defect was left empty, sutured with a 5-0 suture or filled with a hyaluronan/collagen composite matrix without cells, with platelet rich plasma or with autologous mesenchymal stem cells. Matrices with stem cells were in part precultured in chondrogenic medium for 14 days prior to the implantation. Menisci were harvested at 6 and 12 weeks. The developed repair tissue was analyzed macroscopically, histologically and biomechanically. Untreated defects, defects treated with suture alone, with cell-free or with platelet rich plasma seeded implants showed a muted fibrous healing response. The implantation of stem cell-matrix constructs initiated fibrocartilage-like repair tissue, with better integration and biomechanical properties in the precultured stem cell-matrix group. A hyaluronan-collagen based composite scaffold seeded with mesenchymal stem cells is more effective in the repair avascular meniscal tear with stable meniscus-like tissue and to restore the native meniscus.}, subject = {Meniskusschaden}, language = {en} } @inproceedings{WeberDendorferDullienetal., author = {Weber, Tim A. and Dendorfer, Sebastian and Dullien, Silvia and Grifka, Joachim and Verkerke, Gijsbertus Jacob and Renkawitz, Tobias}, title = {Measuring functional outcome after total hip replacement with subject-specific hip joint loading}, series = {Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine}, volume = {226}, booktitle = {Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine}, number = {12}, doi = {10.1177/0954411912447728}, pages = {939 -- 946}, abstract = {Total hip replacement is an often-performed orthopedic surgical procedure; the amount of procedures undertaken will increase since our life expectancy is growing. In order to optimize function, hip biomechanics should be restored to as near normal as possible. The goal of this pilot study was to determine whether or not it is feasible to compute the vectorial hip reaction force pathways on the head of the prosthesis and the force angles relative to the cup of the prosthesis that occur during gait in total hip replacement patients, serving as an objective measurement of the functional outcome following hip replacement. A three-dimensional gait analysis, measuring ground reaction forces and kinematics, was performed. The data retrieved from the gait analysis was used as the input for the musculoskeletal model to compute vectorial joint reaction forces for data processing. To evaluate the position and orientation of the joint reaction forces, the force path, as well as the force angles for the operated and non-operated joint, has been calculated during the stance phase of the specific leg. The force path for subject 2 on the non-operated side is only located in the posterior-lateral quarter, as is the force path for subject 1. In contrast to this subject, the force path for subject 2 at the operated hip joint can be found only within the anterior quarter of the head of the implant, where it is nearly equally distributed in the medio-lateral half of the prosthesis head. The force-inclination angles on the cup of subject 1, with respect to the plane of the socket face, indicates that the force vector is mainly positioned in the same quadrant when compared with subject 2 (in a cup-fixed coordinate system). The force-anteversion angle behaves similarly to the force-inclination angle, even when the effects are not as pronounced. The proposed methods in this article are aiming to define two functional outcomes of total hip replacement that are related to wear and rim loading. It is accepted that wear is not only a function of time, but a function of use. Owing to the methods listed in this article, we are able to determine a) the applied force and b) the sliding distance (force pathway) in a subject-specific manner. The computed hip-reaction force angles and the distance to the rim cup are a measurement for cup or rim loading, and occurs in the so-called safe-zones. This method may well give us insight into the biomechanical situation during gait, after receiving total hip replacement, that we need to fully understand the mechanisms acting on a hip joint and to prove a possible increase of functional outcome after receiving total hip replacement.}, subject = {H{\"u}ftgelenkprothese}, language = {en} } @article{RenkawitzDendorfer, author = {Renkawitz, Tobias and Dendorfer, Sebastian}, title = {Orthopedic navigation technology and biomechanical evaluation for total hip replacement}, series = {Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine}, volume = {226}, journal = {Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine}, number = {12}, doi = {10.1177/0954411912458746}, pages = {897 -- 898}, subject = {H{\"u}ftgelenkprothese}, language = {en} } @article{NeuschaeferRubeLehmannPalmetal., author = {Neuschaefer-Rube, C. and Lehmann, Thomas M. and Palm, Christoph and Bredno, J. and Klajman, S. and Spitzer, Klaus}, title = {3D-Visualisierung glottaler Abduktionsbewegungen}, series = {Aktuelle phoniatrisch-p{\"a}daudiologische Aspekte}, volume = {2001/2002}, journal = {Aktuelle phoniatrisch-p{\"a}daudiologische Aspekte}, number = {9}, publisher = {Median}, isbn = {3-922766-76-5}, pages = {58 -- 61}, language = {de} } @article{IlgnerPalmSchuetzetal., author = {Ilgner, Justus F. R. and Palm, Christoph and Sch{\"u}tz, Andreas G. and Spitzer, Klaus and Westhofen, Martin and Lehmann, Thomas M.}, title = {Colour Texture Analysis for Quantitative Laryngoscopy}, series = {Acta Otolaryngologica}, volume = {123}, journal = {Acta Otolaryngologica}, doi = {10.1080/00016480310000412}, pages = {730 -- 734}, abstract = {Whilst considerable progress has been made in enhancing the quality of indirect laryngoscopy and image processing, the evaluation of clinical findings is still based on the clinician's judgement. The aim of this paper was to examine the feasibility of an objective computer-based method for evaluating laryngeal disease. Digitally recorded images obtained by 90 degree- and 70 degree-angled indirect rod laryngoscopy using standardized white balance values were made of 16 patients and 19 healthy subjects. The digital images were evaluated manually by the clinician based on a standardized questionnaire, and suspect lesions were marked and classified on the image. Following colour separation, normal vocal cord areas as well as suspect lesions were analyzed automatically using co-occurrence matrices, which compare colour differences between neighbouring pixels over a predefined distance. Whilst colour histograms did not provide sufficient information for distinguishing between healthy and diseased tissues, consideration of the blue content of neighbouring pixels enabled a correct classification in 81.4\% of cases. If all colour channels (red, green and blue) were regarded simultaneously, the best classification correctness obtained was 77.1\%. Although only a very basic classification differentiating between healthy and diseased tissue was attempted, the results showed progress compared to grey-scale histograms, which have been evaluated before. The results document a first step towards an objective, machine-based classification of laryngeal images, which could provide the basis for further development of an expert system for use in indirect laryngoscopy.}, language = {en} } @inproceedings{PalmLehmannBrednoetal., author = {Palm, Christoph and Lehmann, Thomas M. and Bredno, J. and Neuschaefer-Rube, C. and Klajman, S. and Spitzer, Klaus}, title = {Automated Analysis of Stroboscopic Image Sequences by Vibration Profiles}, series = {Advances in Quantitative Laryngoscopy, Voice and Speech Research, Procs. 5th International Workshop}, booktitle = {Advances in Quantitative Laryngoscopy, Voice and Speech Research, Procs. 5th International Workshop}, abstract = {A method for automated segmentation of vocal cords in stroboscopic video sequences is presented. In contrast to earlier approaches, the inner and outer contours of the vocal cords are independently delineated. Automatic segmentation of the low contrasted images is carried out by connecting the shape constraint of a point distribution model to a multi-channel regionbased balloon model. This enables us to robustly compute a vibration profile that is used as a new diagnostic tool to visualize several vibration parameters in only one graphic. The vibration profiles are studied in two cases: one physiological vibration and one functional pathology.}, language = {en} } @inproceedings{PietrzykPalmBeyer, author = {Pietrzyk, Uwe and Palm, Christoph and Beyer, Thomas}, title = {Investigation of fusion strategies of multi-modality images}, series = {IEEE Nuclear Science Symposium Conference Record}, volume = {4}, booktitle = {IEEE Nuclear Science Symposium Conference Record}, doi = {10.1109/NSSMIC.2004.1462740}, pages = {2399 -- 2401}, abstract = {Presenting images from different modalities seems to be a trivial task considering the challenges to obtain registered images as a pre-requisite for image fusion. In combined tomographs like PET/CT, image registration is intrinsic. However, informative image fusion mandates careful preparation owing to the large amount of information that is presented to the observer. In complex imaging situations it is required to provide tools that are easy to handle and still powerful enough to help the observer discriminating important details from background patterns. We investigated several options for color tables applied to brain and non-brain images obtained with PET, MRI and CT.}, language = {en} } @inproceedings{PietrzykBauerVietenetal., author = {Pietrzyk, Uwe and Bauer, Dagmar and Vieten, Andrea and Bauer, Andreas and Langen, Karl-Josef and Zilles, Karl and Palm, Christoph}, title = {Creating consistent 3D multi-modality data sets from autoradiographic and histological images of the rat brain}, series = {IEEE Nuclear Science Symposium Conference Record}, volume = {6}, booktitle = {IEEE Nuclear Science Symposium Conference Record}, doi = {10.1109/NSSMIC.2004.1466754}, pages = {4001 -- 4003}, abstract = {Volumetric representations of autoradiographic and histological images gain ever more interest as a base to interpret data obtained with /spl mu/-imaging devices like microPET. Beyond supporting spatial orientation within rat brains especially autoradiographic images may serve as a base to quantitatively evaluate the complex uptake patterns of microPET studies with receptor ligands or tumor tracers. They may also serve for the development of rat brain atlases or data models, which can be explored during further image analysis or simulation studies. In all cases a consistent spatial representation of the rat brain, i.e. its anatomy and the corresponding quantitative uptake pattern, is required. This includes both, a restacking of the individual two-dimensional images and the exact registration of the respective volumes. We propose strategies how these volumes can be created in a consistent way and trying to limit the requirements on the circumstances during data acquisition, i.e. being independent from other sources like video imaging of the block face prior to cutting or high resolution micro-X-ray CT or micro MRI.}, language = {en} } @article{Palm, author = {Palm, Christoph}, title = {Color Texture Classification by Integrative Co-Occurrence Matrices}, series = {Pattern Recognition}, volume = {37}, journal = {Pattern Recognition}, number = {5}, doi = {10.1016/j.patcog.2003.09.010}, pages = {965 -- 976}, abstract = {Integrative Co-occurrence matrices are introduced as novel features for color texture classification. The extended Co-occurrence notation allows the comparison between integrative and parallel color texture concepts. The information profit of the new matrices is shown quantitatively using the Kolmogorov distance and by extensive classification experiments on two datasets. Applying them to the RGB and the LUV color space the combined color and intensity textures are studied and the existence of intensity independent pure color patterns is demonstrated. The results are compared with two baselines: gray-scale texture analysis and color histogram analysis. The novel features improve the classification results up to 20\% and 32\% for the first and second baseline, respectively.}, language = {en} } @inproceedings{PietrzykPalmBeyer, author = {Pietrzyk, Uwe and Palm, Christoph and Beyer, Thomas}, title = {Fusion strategies in multi-modality imaging}, series = {Medical Physics, Vol 2. Proceedings of the jointly held Congresses: ICMP 2005, 14th International Conference of Medical Physics of the International Organization for Medical Physics (IOMP), the European Federation of Organizations in Medical Physics (EFOMP) and the German Society of Medical Physics (DGMP) ; BMT 2005, 39th Annual Congress of the German Society for Biomedical Engineering (DGBMT) within VDE ; 14th - 17th September 2005, Nuremberg, Germany}, booktitle = {Medical Physics, Vol 2. Proceedings of the jointly held Congresses: ICMP 2005, 14th International Conference of Medical Physics of the International Organization for Medical Physics (IOMP), the European Federation of Organizations in Medical Physics (EFOMP) and the German Society of Medical Physics (DGMP) ; BMT 2005, 39th Annual Congress of the German Society for Biomedical Engineering (DGBMT) within VDE ; 14th - 17th September 2005, Nuremberg, Germany}, pages = {1446 -- 1447}, subject = {Bildgebendes Verfahren}, language = {en} } @inproceedings{PalmDehnhardtVietenetal., author = {Palm, Christoph and Dehnhardt, Markus and Vieten, Andrea and Pietrzyk, Uwe}, title = {3D rat brain tumor reconstruction}, series = {Biomedizinische Technik}, volume = {50}, booktitle = {Biomedizinische Technik}, number = {Suppl. 1, Part 1}, pages = {597 -- 598}, subject = {Dreidimensionale Rekonstruktion}, language = {en} } @article{WiesentSchultheissSchmidetal., author = {Wiesent, Lisa and Schultheiss, Ulrich and Schmid, Christof and Schratzenstaller, Thomas and Nonn, Aida}, title = {Experimentally validated simulation of coronary stents considering different dogboning ratios and asymmetric stent positioning}, series = {PlOS One}, volume = {14}, journal = {PlOS One}, number = {10}, publisher = {PLOS}, doi = {10.1371/journal.pone.0224026}, pages = {1 -- 25}, abstract = {In-stent restenosis remains a major problem of arteriosclerosis treatment by stenting. Expansion-optimized stents could reduce this problem. With numerical simulations, stent designs/ expansion behaviours can be effectively analyzed. For reasons of efficiency, simplified models of balloon-expandable stents are often used, but their accuracy must be challenged due to insufficient experimental validation. In this work, a realistic stent life-cycle simulation has been performed including balloon folding, stent crimping and free expansion of the balloon-stent-system. The successful simulation and validation of two stent designs with homogenous and heterogeneous stent stiffness and an asymmetrically positioned stent on the balloon catheter confirm the universal applicability of the simulation approach. Dogboning ratio, as well as the final dimensions of the folded balloon, the crimped and expanded stent, correspond well to the experimental dimensions with only slight deviations. In contrast to the detailed stent life-cycle simulation, a displacement-controlled simulation can not predict the transient stent expansion, but is suitable to reproduce the final expanded stent shape and the associated stress states. The detailed stent life-cycle simulation is thus essential for stent expansion analysis/optimization, whereas for reasons of computational efficiency, the displacement-controlled approach can be considered in the context of pure stress analysis.}, subject = {Stent}, language = {en} } @article{GeithSommerSchratzenstalleretal., author = {Geith, Markus A. and Sommer, Gerhard and Schratzenstaller, Thomas and Holzapfel, Gerhard A.}, title = {Biomechanical and structural quantification of vascular damage: A unique investigation of stent implantation}, series = {Artery Research}, volume = {20}, journal = {Artery Research}, number = {Issue C}, doi = {10.1016/j.artres.2017.10.025}, pages = {50}, language = {en} } @article{DendorferMaierTayloretal., author = {Dendorfer, Sebastian and Maier, Hans J{\"u}rgen and Taylor, David and Hammer, Joachim}, title = {Anisotropy of the fatigue behaviour of cancellous bone}, series = {Journal of Biomechanics}, volume = {41}, journal = {Journal of Biomechanics}, number = {3}, doi = {10.1016/j.jbiomech.2007.09.037}, pages = {636 -- 641}, abstract = {The fatigue behaviour of materials is of particular interest for the failure prediction of materials and structures exposed to cyclic loading. For trabecular bone structures only a few sets of lifetime data have been reported in the literature and structural measures are commonly not considered. The influence of load contributions which are not aligned with the main physiological axis remains unclear. Furthermore site and species dependent relationships are not well described. In this study five different groups of trabecular bone, defined in terms of orientation, species and site were exposed to cyclic compression. In total, 108 fatigue tests were analysed. The lifetimes were found to decrease drastically when off-axis loads were applied. Additionally, species and site strongly affect fatigue lifetimes. Strains at failure were also found to be a function of orientation.}, subject = {Erm{\"u}dung}, language = {en} } @article{PfeiferMuellerPrantletal., author = {Pfeifer, Christian and M{\"u}ller, Michael and Prantl, Lukas and Berner, Arne and Dendorfer, Sebastian and Englert, Carsten}, title = {Cartilage labelling for mechanical testing in T-peel configuration}, series = {International Orthopaedics}, volume = {36}, journal = {International Orthopaedics}, number = {7}, publisher = {Springer}, doi = {10.1007/s00264-011-1468-3}, pages = {1493 -- 1499}, abstract = {PURPOSE: The purpose of this study was to find a suitable method of labelling cartilage samples for the measurement of distraction distances in biomechanical testing. METHODS: Samples of bovine cartilage were labelled using five different methods: hydroquinone and silver nitrate (AgNO3), potassium permanganate (KMnO4) with sodium thiosulphate (Na2S2O3), India ink, heat, and laser energy. After the labelling, we analysed the cartilage samples with regard to cytotoxity by histochemical staining with ethidiumbromide homodimer (EthD-1) and calcein AM. Furthermore, we tested cartilages labelled with India ink and heat in a T-peel test configuration to analyse possible changes in the mechanical behaviour between marked and unlabelled samples. RESULTS: Only the labelling methods with Indian ink or a heated needle showed acceptable results in the cytotoxity test with regard to labelling persistence, accuracy, and the influence on consistency and viability of the chondrocytes. In the biomechanical T-peel configuration, heat-labelled samples collapsed significantly earlier than unlabelled samples. CONCLUSION: Labelling bovine cartilage samples with Indian ink in biomechanical testing is a reliable, accurate, inexpensive, and easy-to-perform method. This labelling method influenced neither the biomechanical behaviour nor the viability of the tissue compared to untreated bovine cartilage.}, subject = {Knorpel}, 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{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, Johannes 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{LenichBachmeierDendorferetal., author = {Lenich, Andreas and Bachmeier, S. and Dendorfer, Sebastian and Mayr, E. and Nerlich, Michael and F{\"u}chtmeier, Bernd}, title = {Development of a test system to analyze different hip fracture osteosyntheses under simulated walking}, series = {Biomedizinische Technik. Biomedical engineering}, volume = {57}, journal = {Biomedizinische Technik. Biomedical engineering}, number = {2}, doi = {10.1515/bmt-2011-0999}, pages = {113 -- 119}, abstract = {The mechanical complications of osteosyntheses after hip fractures are previously investigated by mostly static or dynamic uniaxial loading test systems. However, the physiologic loading of the hip joint during a normal gait is a multiplanar, dynamic movement. Therefore, we constructed a system to test osteosyntheses for hip fractures under physiologic multiplanar loading representative of normal gait. To evaluate the testing system, 12 femora pairs were tested under 25,000 cycles with two standard osteosyntheses (Proximal Femoral Nail Antirotation/Gamma3 Nail). For angular movement, the varus collapse to cut out (∝CO) (∝CO=4.8°±2.1° for blade and ∝CO=7.8°±3.8° for screw) was the dominant failure mode, and only slight rotational angle shifts (∝Rot) (∝Rot=1.7°±0.4° for blade and ∝Rot=2.4°±0.3° for screw) of the femoral head around the implant axis were observed. Angular displacements in varus direction and rotation were higher in specimens reinforced with screws. Hence, the cut out model and the migration directions showed a distinction between helical blade and hip screw. However, there were no significant differences between the different implants. The new setup is able to create clinical failures and allows to give evidence about the anchorage stability of different implant types under dynamic gait motion pattern.}, subject = {H{\"u}ftgelenk}, language = {en} }