TY - GEN A1 - Melzner, Maximilian A1 - Pfeifer, Christian A1 - Alt, V. A1 - Süß, Franz A1 - Dendorfer, Sebastian T1 - Änderung der Gelenkreaktionskraft bei Schädigung des medialen Bandapparates im Ellenbogen T2 - Zeitschrift fur Orthopadie und Unfallchirurgie KW - Muskuloskelettale Simulation KW - Ellenbogenstabilität Y1 - 2020 U6 - https://doi.org/10.1055/s-0040-1717270 N1 - Poster VL - 158 IS - S01 PB - Thieme ER - TY - CHAP A1 - Dendorfer, Sebastian T1 - Biomechanical evaluation and optimisation of countermeasure exercises T2 - ESA/ESTEC Bedrest Strategy Workshop, Noordwijk, NL, 2009 Y1 - 2009 ER - TY - CHAP A1 - Dendorfer, Sebastian T1 - How much iron to pump? The determination of muscle forces for activities of daily living T2 - DGU, Berlin, 2008 Y1 - 2008 ER - TY - CHAP A1 - Hammer, Joachim A1 - Dendorfer, Sebastian T1 - Cyclic loading and microstructure of cancellous bone T2 - Journal of Biomechanics Y1 - 2008 U6 - https://doi.org/10.1016/S0021-9290(08)70409-3 VL - 41 IS - Suppl. 1, July 2008 SP - S410 ER - TY - CHAP A1 - Dendorfer, Sebastian A1 - Kubowitsch, Simone T1 - The interaction of mental stress and biomechanics T2 - Health Technology Triangle, Weiden, 2016 Y1 - 2016 ER - TY - JOUR A1 - Weber, Markus A1 - Merle, Christian A1 - Nawabi, Danyal H. A1 - Dendorfer, Sebastian A1 - Grifka, Joachim A1 - Renkawitz, Tobias T1 - Inaccurate offset restoration in total hip arthroplasty results in reduced range of motion JF - Scientific Reports N2 - Offset restoration in total hip arthroplasty (THA) is associated with postoperative range of motion (ROM) and gait kinematics. We aimed to research into the impact of high offset (HO) and standard stems on postoperative ROM. 121 patients received cementless THA through a minimally-invasive anterolateral approach. A 360° hip ROM analysis software calculated impingement-free hip movement based on postoperative 3D-CTs compared to ROM values necessary for activities of daily living (ADL). The same model was then run a second time after changing the stem geometry between standard and HO configuration with the implants in the same position. HO stems showed higher ROM for all directions between 4.6 and 8.9° (p < 0.001) compared with standard stems but with high interindividual variability. In the subgroup with HO stems for intraoperative offset restoration, the increase in ROM was even higher for all ROM directions with values between 6.1 and 14.4° (p < 0.001) compared to offset underrestoration with standard stems. Avoiding offset underrestoration resulted in a higher amount of patients of over 20% for each ROM direction that fulfilled the criteria for ADL (p < 0.001). In contrast, in patients with standard stems for offset restoration ROM did increase but not clinically relevant by offset overcorrection for all directions between 3.1 and 6.1° (p < 0.001). Offset overcorrection by replacing standard with HO stems improved ROM for ADL in a low number of patients below 10% (p > 0.03). Patient-individual restoration of offset is crucial for free ROM in THA. Both over and underrestoration of offset should be avoided. KW - Adaptive clinical trial KW - Bone imaging Y1 - 2020 U6 - https://doi.org/10.1038/s41598-020-70059-1 VL - 10 IS - 13208 SP - 9 PB - Nature ER - TY - JOUR A1 - Aurbach, Maximilian A1 - Špička, Jan A1 - Süß, Franz A1 - Vychytil, J. A1 - Havelková, Leonard A1 - Ryba, T. A1 - Dendorfer, Sebastian T1 - Torus obstacle method as a wrapping approach of the deltoid muscle group for humeral abduction in musculoskeletal simulation JF - Journal of Biomechanics N2 - Musculoskeletal models of the shoulder complex are valuable research aids to investigate tears of the supraspinatus and the resulting mechanical impact during abduction of the humerus. One of the major contributors to this motion is the deltoid muscle group and for this, an accurate modeling of the lines of action is indispensable. The aim of this work was to utilize a torus obstacle wrapping approach for the deltoids of an existing shoulder model and assess the feasibility of the approach during humeral abduction. The shoulder model from the AnyBody™ modeling system was used as a platform. The size of the tori is based on a magnetic resonance imaging (MRI) approach and several kinematic couplings are implemented to determine the trajectories of the tori during abduction. To assess the model behavior, the moment arms of the virtual muscle elements and the resultant glenohumeral joint reaction force (GHJF) were compared with reference data from the literature during abduction of the humerus in the range 20°–120°. The root mean square error for the anterior, lateral and posterior part between the simulated muscle elements and reference data from the literature was 3.9, 1.7 and 5.8 mm, respectively. The largest deviation occurred on the outer elements of the muscle groups, with 12.6, 10.4 and 20.5 mm, respectively. During abduction, there is no overlapping of the muscle elements and these are in continuous contact with the torus obstacles, thus enabling a continuous force transmission. This results in a rising trend of the resultant GHJF. The torus obstacle approach as a wrapping method for the deltoid muscles provides a guided muscle pathing by simultaneously approximating the curvature of the deltoid muscle. The results from the comparison of the simulated moment arms and the resultant GHJF are in accordance with those in the literature in the range 20°–120° of abduction. Although this study shows the strength of the torus obstacle as a wrapping approach, the method of fitting the tori according to MRI data was not suitable. A cadaver study is recommended to better validate and mathematically describe the torus approach. KW - Muscoloskeletal model KW - AnyBody Modeling System KW - MRI KW - Shoulder joint complex KW - Muscle trajectory KW - Torus KW - Wrapping Y1 - 2020 U6 - https://doi.org/10.1016/j.jbiomech.2020.109864 VL - 109 IS - August PB - Elsevier ER - TY - CHAP A1 - Auer, Simon A1 - Kubowitsch, Simone A1 - Krutsch, Werner A1 - Renkawitz, Tobias A1 - Süß, Franz A1 - Dendorfer, Sebastian T1 - Effect of mental demand on knee forces in professional youth soccer players T2 - ISBS Proceedings Archive N2 - Soccer is one of the most popular sports all around the world. It is an injurious type of sport with a focus on lower extremities and high psychological pressure during matches. The stressor is linked with injuries and an increased musculoskeletal loading. This study investigates the influence of cognitive stress on the load profile of the knee joint. Twelve professional youth soccer players performed highly dynamic runs with and without additional cognitive stress. The runs were analysed with a musculoskeletal simulation software. The data analysis shows no difference in knee joint reaction loading under additional mental stress compared to the baseline. Yet running times are significantly lower in the baseline. While there is no increase in the joint loads, the running times indicate an altered movement behaviour when the subjects are exposed to additional mental demand. KW - Kniegelenk KW - Körperliche Belastung KW - Stress KW - Computersimulation Y1 - 2020 UR - https://commons.nmu.edu/isbs/vol38/iss1/28 VL - 38 IS - 1, Art. 28 ER - TY - JOUR A1 - De Pieri, Enrico A1 - Atzori, Federica A1 - Ferguson, Stephen J. A1 - Dendorfer, Sebastian A1 - Leunig, Michael A1 - Aepli, Martin T1 - Contact force path in total hip arthroplasty: effect of cup medialisation in a whole-body simulation JF - HIP International N2 - Background: Cup medialisation down to the true acetabular floor in total hip arthroplasty with a compensatory femoral offset increase seems to be mechanically advantageous for the abductor muscles due to the relocation of the lever arms (body weight lever arm decreased, abductor lever arm increased). However, limited information is currently available about the effects of this reconstruction type at the head cup interface, compared to an anatomical reconstruction that maintains the natural lever arms. Through a whole-body simulation analysis, we compared medialised versus anatomical reconstruction in THA to analyse the effects on: (1) contact force magnitude at the head cup interface; (2) contact force path in the cup; and (3) abductor activity. Methods: Musculoskeletal simulations were performed to calculate the above-mentioned parameters using inverse dynamics analysis. The differences between the virtually implanted THAs were calculated to compare the medialised versus anatomical reconstruction. Results: Cup medialisation with compensatory femoral offset increase led to: (1) a reduction in contact force magnitude at the head cup interface up to 6.6%; (2) a similar contact force path in the cup in terms of sliding distance and aspect ratio; and (3) a reduction in abductor activity up to 17.2% (gluteus medius). Conclusions: In our opinion, these potential biomechanical gains do not generally justify a fully medialised reconstruction, especially in younger patients that are more likely to undergo revision surgery in their lifetime. Cup medialisation should be performed until sufficient press fit and bony coverage of a properly sized and oriented cup can be achieved. KW - Cup medialisation KW - femoral offset KW - hip contact force KW - total hip anthroplasty KW - total hip replacement KW - Hüftgelenkprothese KW - Kontaktkraft KW - Biomechanische Analyse KW - Simulation Y1 - 2020 U6 - https://doi.org/10.1177/1120700020917321 VL - 31 IS - 5 SP - 624 EP - 631 PB - Sage ER - TY - JOUR A1 - Aurbach, Maximilian A1 - Spicka, Jan A1 - Süß, Franz A1 - Dendorfer, Sebastian T1 - Evaluation of musculoskeletal modelling parameters of the shoulder complex during humeral abduction above 90° JF - Journal of Biomechanics N2 - Based on electromyographic data and force measurements within the shoulder joint, there is an indication that muscle and resulting joint reaction forces keep increasing over an abduction angle of 90°. In inverse dynamics models, no single parameter could be attributed to simulate this force behaviour accordingly. The aim of this work is to implement kinematic, kinetic and muscle model modifications to an existing model of the shoulder (AnyBody™) and assess their single and combined effects during abduction up to 140° humeral elevation. The kinematics and the EMG activity of 10 test subjects were measured during humeral abduction. Six modifications were implemented in the model: alternative wrapping of the virtual deltoid muscle elements, utilization of a three element Hill model, strength scaling, motion capture driven clavicle elevation/protraction, translation of the GH joint in dependency of the acting forces and an alteration of the scapula/clavicle rhythm. From the six modifications, 16 different combinations were considered. Parameter combinations with the Hill model changed the resultant GH joint reaction force and led to an increase in force during abduction of the humerus above 90°. Under the premise of muscle activities and forces within the GH joint rising after 90° of humeral abduction, we propose that the Hill type muscle model is a crucial parameter for accurately modelling the shoulder. Furthermore, the outcome of this study indicates that the Hill model induces the co-contraction of the muscles of the shoulder without the need of an additional stability criterion for an inverse dynamics approach. KW - Shoulder joint KW - Musculoskeletal modelling KW - EMG KW - Glenohumeral joint reaction force KW - Muscle model KW - Schultergelenk KW - Bewegungsapparat KW - Biomechanik KW - Simulation Y1 - 2020 U6 - https://doi.org/10.1016/j.jbiomech.2020.109817 VL - 106 IS - June PB - Elsevier ER - TY - CHAP A1 - Aurbach, Maximilian A1 - Wagner, Kilian A1 - Süß, Franz A1 - Dendorfer, Sebastian ED - Badnjevic, Almir T1 - Implementation and Validation of Human Kinematics Measured Using IMUs for Musculoskeletal Simulations by the Evaluation of Joint Reaction Forces T2 - CMBEBIH 2017, Proceedings of the International Conference on Medical and Biological Engineering 2017, Sarajevo, Bosnia and Herzegovina N2 - 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. KW - Inertial Measurement Units KW - Multibody Simulation KW - Musculoskeletal Simulation KW - AnyBody KW - Motion Capture KW - Bewegungsapparat KW - Biomechanik KW - Motion Capturing KW - Mehrkörpersimulation KW - Ground Reaction Force Prediction KW - Gait KW - IMU KW - Joint Reaction Forces Y1 - 2017 U6 - https://doi.org/10.1007/978-981-10-4166-2_31 VL - Vol. 62 SP - 205 EP - 211 PB - Springer CY - Singapore ER - TY - CHAP A1 - Jungtäubl, Dominik A1 - Schmitz, Paul A1 - Gross, Simon A1 - Dendorfer, Sebastian ED - Badnjevic, Almir T1 - FEA of the transiliacal internal fixator as an osteosynthesis of pelvic ring fractures T2 - CMBEBIH 2017, Proceedings of the International Conference on Medical and Biological Engineering 2017 N2 - 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. KW - Finite element analysis KW - Musculoskeletal simulation KW - Internal fixator KW - Pelvic ring fracture KW - Beckenbruch KW - Operationstechnik KW - Finite-Elemente-Methode KW - Biomechanik KW - Simulation Y1 - 2017 SN - 978-981-10-4165-5 U6 - https://doi.org/10.1007/978-981-10-4166-2_32 SP - 212 EP - 217 PB - Springer CY - Singapore ER - TY - JOUR A1 - Ignasiak, Dominika A1 - Dendorfer, Sebastian A1 - Ferguson, Stephen J. T1 - Thoracolumbar spine model with articulated ribcage for the prediction of dynamic spinal loading JF - Journal of Biomechanics N2 - Musculoskeletal modeling offers an invaluable insight into the spine biomechanics. A better understanding of thoracic spine kinetics is essential for understanding disease processes and developing new prevention and treatment methods. Current models of the thoracic region are not designed for segmental load estimation, or do not include the complex construct of the ribcage, despite its potentially important role in load transmission. In this paper, we describe a numerical musculoskeletal model of the thoracolumbar spine with articulated ribcage, modeled as a system of individual vertebral segments, elastic elements and thoracic muscles, based on a previously established lumbar spine model and data from the literature. The inverse dynamics simulations of the model allow the prediction of spinal loading as well as costal joints kinetics and kinematics. The intradiscal pressure predicted by the model correlated well (R2=0.89) with reported intradiscal pressure measurements, providing a first validation of the model. The inclusion of the ribcage did not affect segmental force predictions when the thoracic spine did not perform motion. During thoracic motion tasks, the ribcage had an important influence on the predicted compressive forces and muscle activation patterns. The compressive forces were reduced by up to 32%, or distributed more evenly between thoracic vertebrae, when compared to the predictions of the model without ribcage, for mild thoracic flexion and hyperextension tasks, respectively. The presented musculoskeletal model provides a tool for investigating thoracic spine loading and load sharing between vertebral column and ribcage during dynamic activities. Further validation for specific applications is still necessary. KW - Inverse dynamics KW - Musculoskeletal model KW - Thoracolumbar spine KW - Brustwirbelsäule KW - Brustkorb KW - Biomechanik KW - Mechanische Belastung KW - Prognose Y1 - 2016 U6 - https://doi.org/10.1016/j.jbiomech.2015.10.010 VL - vol. 49 IS - 6 SP - 959 EP - 966 PB - Elsevier Science ER - TY - JOUR A1 - Lazarev, Igor A. A1 - Ryabokon, P.V. A1 - Haller, M. A1 - Dendorfer, Sebastian T1 - Effect of the fractured calcaneus's peripheral fragment displacement on the triceps surae function JF - ЖУРНАЛ «ТРАВМА» Ukrainian Trauma Journal Y1 - 2015 VL - 2, TOM 16 ER - TY - JOUR A1 - Weber, Tim A. A1 - Dendorfer, Sebastian A1 - Grifka, Joachim A1 - Verkerke, Gijsbertus Jacob A1 - Renkawitz, Tobias ED - Takagi, Michiaki T1 - Does Computer-Assisted Femur First THR Improve Musculoskeletal Loading Conditions? JF - BioMed Research International N2 - We have developed a novel, computer-assisted operation method for minimal-invasive total hip replacement (THR) following the concept of “femur first/combined anteversion,” which incorporates various aspects of performing a functional optimization of the prosthetic stem and cup position (CAS FF). The purpose of this study is to assess whether the hip joint reaction forces and patient’s gait parameters are being improved by CAS FF in relation to conventional THR (CON). We enrolled 60 patients (28 CAS FF/32 CON) and invited them for gait analysis at three time points (preoperatively, postop six months, and postop 12 months). Data retrieved from gait analysis was processed using patient-specific musculoskeletal models. The target parameters were hip reaction force magnitude (hrf), symmetries, and orientation with respect to the cup. Hrf in the CAS FF group were closer to a young healthy normal. Phase-shift symmetry showed an increase in the CAS FF group. Hrf orientation in the CAS FF group was closer to optimum, though no edge or rim-loading occurred in the CON group as well. The CAS FF group showed an improved hrf orientation in an early stage and a trend to an improved long-term outcome. KW - Hüftgelenkprothese KW - Operationstechnik KW - Computerunterstütztes Verfahren KW - Bewegungsapparat KW - Mechanische Belastung Y1 - 2015 U6 - https://doi.org/10.1155/2015/625317 VL - 2015 SP - ID 625317 ER - TY - JOUR A1 - Weber, Tim A1 - Al-Munajjed, Amir Andreas A1 - Verkerke, Gijsbertus Jacob A1 - Dendorfer, Sebastian A1 - Renkawitz, Tobias T1 - Influence of minimally invasive total hip replacement on hip reaction forces and their orientations JF - Journal of Orthopaedic Research N2 - 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. KW - THA KW - THR KW - Biomechanics KW - Conventional surgery KW - Early recovery KW - Hüftgelenkprothese KW - Minimal-invasive Chirurgie KW - Biomechanik Y1 - 2014 U6 - https://doi.org/10.1002/jor.22710 VL - 32 IS - 12 SP - 1680 EP - 1687 ER - TY - JOUR A1 - Dendorfer, Sebastian A1 - Weber, Tim A1 - Kennedy, O. T1 - Musculoskeletal modeling for hip replacement outcome analyses and other applications JF - The Journal of the American Academy of Orthopaedic Surgeons KW - Hüftgelenkprothese KW - Bewegungsapparat KW - Simulation Y1 - 2014 U6 - https://doi.org/10.5435/JAAOS-22-04-268 VL - 22 IS - 4 SP - 268 EP - 269 ER - TY - JOUR A1 - Penzkofer, Rainer A1 - Barnsteiner, K. A1 - Dendorfer, Sebastian T1 - The influence of age, shoe type and kicking direction on the severity of head trauma JF - Journal of Forensic Biomechanics N2 - 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. KW - Head trauma KW - Biomechanics KW - Kicks KW - Kopfverletzung KW - Schädel-Hirn-Trauma KW - Einflussgröße Y1 - 2014 UR - https://www.longdom.org/open-access/the-influence-of-age-shoe-type-and-kicking-direction-on-the-severity-of-head-trauma-2090-2697-1000116.pdf U6 - https://doi.org/10.4172/2090-2697.1000116 VL - 5 IS - 1 ER - TY - JOUR A1 - Zellner, Johannes A1 - Hierl, Katja A1 - Mueller, Michael A1 - Pfeifer, Christian A1 - Berner, Arne A1 - Dienstknecht, Thomas A1 - Krutsch, Werner A1 - Geis, Sebastian A1 - Gehmert, Sebastian A1 - Kujat, Richard A1 - Dendorfer, Sebastian A1 - Prantl, Lukas A1 - Nerlich, Michael A1 - Angele, Peter ED - Gilbert, Jeremy T1 - Stem cell-based tissue-engineering for treatment of meniscal tears in the avascular zone JF - Journal of Biomedical Materials Research Part B Applied Biomaterials N2 - 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. KW - biomechanics KW - meniscus KW - scaffolds KW - stem cells KW - tissue engineering KW - Meniskusschaden KW - Tissue Engineering KW - Mesenchymzelle KW - Hyaluronsäure Y1 - 2013 U6 - https://doi.org/10.1002/jbm.b.32922 VL - 101 IS - 7 SP - 1133 EP - 1142 ER - TY - CHAP A1 - Weber, Tim A. A1 - Dendorfer, Sebastian A1 - Dullien, Silvia A1 - Grifka, Joachim A1 - Verkerke, Gijsbertus Jacob A1 - Renkawitz, Tobias T1 - Measuring functional outcome after total hip replacement with subject-specific hip joint loading T2 - Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine N2 - 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. KW - total hip replacement KW - subject-specific musculoskeletal modeling KW - functional outcome KW - force pathways KW - force angles KW - critical hip joint loading KW - rim loading KW - cup loading KW - Hüftgelenkprothese KW - Biomechanik KW - Lastverteilung KW - Ganganalyse KW - Simulation Y1 - 2012 U6 - https://doi.org/10.1177/0954411912447728 VL - 226 IS - 12 SP - 939 EP - 946 ER - TY - JOUR A1 - Renkawitz, Tobias A1 - Dendorfer, Sebastian T1 - Orthopedic navigation technology and biomechanical evaluation for total hip replacement JF - Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine KW - Hüftgelenkprothese KW - Orthopädische Chirurgie KW - Computerunterstütztes Verfahren KW - Biomechanische Analyse Y1 - 2012 U6 - https://doi.org/10.1177/0954411912458746 VL - 226 IS - 12 SP - 897 EP - 898 ER - TY - JOUR A1 - Dendorfer, Sebastian A1 - Maier, Hans Jürgen A1 - Taylor, David A1 - Hammer, Joachim T1 - Anisotropy of the fatigue behaviour of cancellous bone JF - Journal of Biomechanics N2 - The fatigue behaviour of materials is of particular interest for the failure prediction of materials and structures exposed to cyclic loading. For trabecular bone structures only a few sets of lifetime data have been reported in the literature and structural measures are commonly not considered. The influence of load contributions 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. KW - Ermüdung KW - Knochen KW - Spongiosa KW - Anisotropie Y1 - 2008 U6 - https://doi.org/10.1016/j.jbiomech.2007.09.037 VL - 41 IS - 3 SP - 636 EP - 641 ER - TY - JOUR A1 - Pfeifer, Christian A1 - Müller, Michael A1 - Prantl, Lukas A1 - Berner, Arne A1 - Dendorfer, Sebastian A1 - Englert, Carsten T1 - Cartilage labelling for mechanical testing in T-peel configuration JF - International Orthopaedics N2 - PURPOSE: The purpose of this study was to find a suitable method of labelling cartilage samples for the measurement of distraction distances in biomechanical testing. METHODS: Samples of bovine cartilage were labelled using five different methods: hydroquinone and silver nitrate (AgNO3), potassium permanganate (KMnO4) with sodium thiosulphate (Na2S2O3), India ink, heat, and laser energy. After the labelling, we analysed the cartilage samples with regard to cytotoxity by histochemical staining with ethidiumbromide homodimer (EthD-1) and calcein AM. Furthermore, we tested cartilages labelled with India ink and heat in a T-peel test configuration to analyse possible changes in the mechanical behaviour between marked and unlabelled samples. RESULTS: Only the labelling methods with Indian ink or a heated needle showed acceptable results in the cytotoxity test with regard to labelling persistence, accuracy, and the influence on consistency and viability of the chondrocytes. In the biomechanical T-peel configuration, heat-labelled samples collapsed significantly earlier than unlabelled samples. CONCLUSION: Labelling bovine cartilage samples with Indian ink in biomechanical testing is a reliable, accurate, inexpensive, and easy-to-perform method. This labelling method influenced neither the biomechanical behaviour nor the viability of the tissue compared to untreated bovine cartilage. KW - Bovine cartilage KW - Cartilage samples KW - Indian ink KW - T-peel configuration KW - Method labeling KW - Knorpel KW - Rind KW - Kennzeichnung KW - Tinte KW - Biomechanik KW - Prüfung Y1 - 2012 U6 - https://doi.org/10.1007/s00264-011-1468-3 VL - 36 IS - 7 SP - 1493 EP - 1499 PB - Springer ER - TY - JOUR A1 - Englert, Carsten A1 - Angele, Peter A1 - Fierlbeck, J. A1 - Dendorfer, Sebastian A1 - Schubert, T. A1 - Müller, R. A1 - Lienhard, S. A1 - Zellner, Johannes A1 - Nerlich, Michael A1 - Neumann, Carsten T1 - Conductive bone substitute material with variable antibiotic delivery JF - Der Unfallchirurg N2 - 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. KW - Knochenersatz KW - Leitfähgkeit KW - Antibiotika KW - Biomechanik KW - Bone substitute materials KW - Osteoconductive KW - Osteomyelitis KW - Multiresistant KW - Biomechanics Y1 - 2007 U6 - https://doi.org/10.1007/s00113-007-1229-3 VL - 110 IS - 5 SP - 408 EP - 413 PB - Springer ER - TY - JOUR A1 - Lenich, Andreas A1 - Bachmeier, S. A1 - Dendorfer, Sebastian A1 - Mayr, E. A1 - Nerlich, Michael A1 - Füchtmeier, Bernd T1 - Development of a test system to analyze different hip fracture osteosyntheses under simulated walking JF - Biomedizinische Technik. Biomedical engineering N2 - The mechanical complications of osteosyntheses after hip fractures are previously investigated by mostly static or dynamic uniaxial loading test systems. However, the physiologic loading of the hip joint during a normal gait is a multiplanar, dynamic movement. Therefore, we constructed a system to test osteosyntheses for hip fractures under physiologic multiplanar loading representative of normal gait. To evaluate the testing system, 12 femora pairs were tested under 25,000 cycles with two standard osteosyntheses (Proximal Femoral Nail Antirotation/Gamma3 Nail). For angular movement, the varus collapse to cut out (∝CO) (∝CO=4.8°±2.1° for blade and ∝CO=7.8°±3.8° for screw) was the dominant failure mode, and only slight rotational angle shifts (∝Rot) (∝Rot=1.7°±0.4° for blade and ∝Rot=2.4°±0.3° for screw) of the femoral head around the implant axis were observed. Angular displacements in varus direction and rotation were higher in specimens reinforced with screws. Hence, the cut out model and the migration directions showed a distinction between helical blade and hip screw. However, there were no significant differences between the different implants. The new setup is able to create clinical failures and allows to give evidence about the anchorage stability of different implant types under dynamic gait motion pattern. KW - biomechanical implant test KW - dynamic multiplanar loading KW - hip fractureg KW - implant migration KW - patient specific loading KW - Hüftgelenk KW - Knochenbruch KW - Osteosynthese KW - Bewegungsanalyse KW - Simulation Y1 - 2012 U6 - https://doi.org/10.1515/bmt-2011-0999 VL - 57 IS - 2 SP - 113 EP - 119 ER - TY - JOUR A1 - Dendorfer, Sebastian A1 - Maier, Hans Jürgen A1 - Hammer, Joachim T1 - Fatigue damage in cancellous bone: an experimental approach from continuum to micro scale JF - Journal of the Mechanical Behavior of Biomedical Materials N2 - 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. KW - Knochen KW - Spongiosa KW - Ermüdungsbruch KW - Fatigue KW - Cancellous bone KW - Deformation behaviour KW - Damage KW - Measurement and testing KW - Mechanical behaviour Y1 - 2009 U6 - https://doi.org/10.1016/j.jmbbm.2008.03.003 VL - 2 IS - 1 SP - 113 EP - 119 ER - TY - CHAP A1 - Dendorfer, Sebastian A1 - Maier, Hans Jürgen A1 - Hammer, Joachim T1 - How do age and anisotropy affect the fatigue behaviour of cancellous bone? T2 - Medicine Meets Engineering N2 - The fatigue behaviour of materials is of particular interest for the failure prediction of materials and structures exposed to cyclic loading. For trabecular bone structures only a few sets of lifetime data have been reported in the literature and structural measures are commonly not considered. The influence of load contributions not aligned with the main physiological axis remains unclear. Furthermore age effects on the fatigue behaviour are not well described. In the present study, different groups of human vertebral cancellous bone were exposed to cyclic compression. The inital modulus and therefore lifetimes were found to be highly dependent on age. The decrease in both with increasing age was much more pronounced in specimens which were not aligned with the main physiological axis. This implies that old bone is much more sensitive to (cyclic) failure loads in general but particularly to loads which are not coincident with the physiological main axis. KW - Knochenbruch KW - Spongiosa KW - Alter KW - Anisotropie Y1 - 2008 SP - 68 EP - 74 PB - IOS Press ER - TY - JOUR A1 - Hoenicka, Markus A1 - Lehle, Karla A1 - Jacobs, V. R. A1 - Dendorfer, Sebastian A1 - Kostorz, A. A1 - Schmid, F. X. A1 - Birnbaum, D. E. T1 - Mechanical and seeding properties of human umbilical vein – a potential scaffold for a tissue-engineered vessel graft JF - The Thoracic and Cardiovascular Surgeon N2 - 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. KW - Nabelvene KW - Tissue Engineering Y1 - 2007 U6 - https://doi.org/10.1055/s-2007-967592 VL - 55 IS - S 1 SP - P_37 PB - Thieme ER -