@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{DendorferFeldottoWalchetal., author = {Dendorfer, Sebastian and Feldotto, Benedikt and Walch, Blasius and Koch, Patrick and Knoll, Alois}, title = {Co-Development of an Infant Prototype in Hardware and Simulation based on CT Imaging Data}, series = {IEEE International Conference on Cyborg and Bionic Systems (CBS), 2019, Munich}, booktitle = {IEEE International Conference on Cyborg and Bionic Systems (CBS), 2019, Munich}, pages = {6}, abstract = {The development of biomimetic robots has gained research interest in the last years as it may both help under-standing processes of motion execution in biological systems as well as developping a novel generation of intelligent and energy efficient robots. However, exact model generation that builds up on observations and robot design is very time intensive. In this paper we present a novel pipeline for co-development of biomimetic hardware and simulation models based on biological Computer Tomography (CT) data. For this purpose we exploit State of the Art rapid prototyping technologies such as 3D Printing and the Neurorobotics Platform for musculoskeletal simulations in virtual environments. The co-development integrates both advantages of virtual and physical experimental models and is expected to increase development speed of controllers that can be tested on the simulated counterpart before application to a printed robot model. We demonstrate the pipeline by generating a one year old infant model as a musculoskeletal simulation model and a print-in-place 3D printed skeleton as a single movable part. Even though we hereonly introduce the initial body generation and only a first testsetup for a modular sensory and control framework, we can clearly spot advantages in terms of rapid model generation and highly biological related models. Engineering costs are reducedand models can be provided to a wide research community for controller testing in an early development phase.}, subject = {Biomechanische Analyse}, language = {en} } @article{WeberDendorferBulstraetal., author = {Weber, Tim A. and Dendorfer, Sebastian and Bulstra, Sjoerd K. and Grifka, Joachim and Verkerke, Gijsbertus Jacob and Renkawitz, Tobias}, title = {Gait six month and one-year after computer assisted Femur First THR vs. conventional THR. Results of a patient- and observer- blinded randomized controlled trial}, series = {Gait \& Posture}, volume = {vol. 49}, journal = {Gait \& Posture}, doi = {10.1016/j.gaitpost.2016.06.035}, pages = {418 -- 425}, abstract = {A prospective randomized controlled trial is presented that is used to compare gait performance between the computer assisted Femur First (CAS FF) operation method and conventional THR (CON). 60 patients underwent a 3D gait analysis of the lower extremity at pre-operative, 6 months post-operative and twelve months post-operative. Detailed verification experiments were facilitated to ensure the quality of data as well as to avoid over-interpreting of the data. The results confirm a similar data-quality as reported in the literature. Walking speed, range of motion and symmetry thereof improved over the follow-up period, without significant differences between the groups. While all parameters do significantly increase over the follow-up period for both groups, there were no significant differences between them at any given time-point. Patients undergoing CAS FF showed a trend to improved hip flexion angle indicating a possible long-term benefit.}, language = {en} } @article{RenkawitzWeberDullienetal., author = {Renkawitz, Tobias and Weber, Tim A. and Dullien, Silvia and Woerner, Michael and Dendorfer, Sebastian and Grifka, Joachim and Weber, Markus}, title = {Leg length and offset differences above 5 mm after total hip arthroplasty are associated with altered gait kinematics}, series = {Gait \& Posture}, volume = {vol. 49}, journal = {Gait \& Posture}, doi = {10.1016/j.gaitpost.2016.07.011}, pages = {196 -- 201}, abstract = {We aimed to investigate the relationship between postoperative leg length/offset (LL/OS) reconstruction and gait performance after total hip arthroplasty (THA). In the course of a prospective randomized controlled trial, 60 patients with unilateral hip arthrosis received cementless THA through a minimally-invasive anterolateral surgical approach. One year post-operatively, LL and global OS restoration were analyzed and compared to the contralateral hip on AP pelvic radiographs. The combined postoperative limb length/OS reconstruction of the operated hip was categorized as restored (within 5 mm) or non-restored (more than 5 mm reduction or more than 5 mm increment). The acetabular component inclination, anteversion and femoral component anteversion were evaluated using CT scans of the pelvis and the femur. 3D gait analysis of the lower extremity and patient related outcome measures (HHS, HOOS, EQ-5D) were obtained pre-operatively, six months and twelve months post-operatively by an observer blinded to radiographic results. Component position of cup and stem was comparable between the restored and non-restored group. Combined LL and OS restoration within 5 mm resulted in higher Froude number (p < 0.001), normalized walking speed (p < 0.001) and hip range-of-motion (ROM) (p = 0.004) during gait twelve months postoperatively, whereas gait symmetry was comparable regardless of LL and OS reconstruction at both examinations. Clinical scores did not show any relevant association between the accuracy of LL or OS reconstruction and gait six/twelve months after THA. In summary, postoperative LL/OS discrepancies larger than 5 mm relate to unphysiological gait kinematics within the first year after THA. DRKS00000739, German Clinical Trials Register.}, language = {en} } @article{IgnasiakDendorferFerguson, author = {Ignasiak, Dominika and Dendorfer, Sebastian and Ferguson, Stephen J.}, title = {Thoracolumbar spine model with articulated ribcage for the prediction of dynamic spinal loading}, series = {Journal of Biomechanics}, volume = {vol. 49}, journal = {Journal of Biomechanics}, number = {6}, publisher = {Elsevier Science}, doi = {10.1016/j.jbiomech.2015.10.010}, pages = {959 -- 966}, abstract = {Musculoskeletal modeling offers an invaluable insight into the spine biomechanics. A better understanding of thoracic spine kinetics is essential for understanding disease processes and developing new prevention and treatment methods. Current models of the thoracic region are not designed for segmental load estimation, or do not include the complex construct of the ribcage, despite its potentially important role in load transmission. In this paper, we describe a numerical musculoskeletal model of the thoracolumbar spine with articulated ribcage, modeled as a system of individual vertebral segments, elastic elements and thoracic muscles, based on a previously established lumbar spine model and data from the literature. The inverse dynamics simulations of the model allow the prediction of spinal loading as well as costal joints kinetics and kinematics. The intradiscal pressure predicted by the model correlated well (R2=0.89) with reported intradiscal pressure measurements, providing a first validation of the model. The inclusion of the ribcage did not affect segmental force predictions when the thoracic spine did not perform motion. During thoracic motion tasks, the ribcage had an important influence on the predicted compressive forces and muscle activation patterns. The compressive forces were reduced by up to 32\%, or distributed more evenly between thoracic vertebrae, when compared to the predictions of the model without ribcage, for mild thoracic flexion and hyperextension tasks, respectively. The presented musculoskeletal model provides a tool for investigating thoracic spine loading and load sharing between vertebral column and ribcage during dynamic activities. Further validation for specific applications is still necessary.}, subject = {Brustwirbels{\"a}ule}, language = {en} } @article{HoelscherWeberLazarevetal., author = {H{\"o}lscher, Thomas and Weber, Tim A. and Lazarev, Igor and Englert, Carsten and Dendorfer, Sebastian}, title = {The influence of rotator cuff tears on glenohumeral stability during abduction tasks}, series = {Journal of Orthopaedic Research}, volume = {34}, journal = {Journal of Orthopaedic Research}, number = {9}, doi = {10.1002/jor.23161}, pages = {1628 -- 1635}, abstract = {One of the main goals in reconstructing rotator cuff tears is the restoration of glenohumeral joint stability, which is subsequently of utmost importance in order to prevent degenerative damage such as superior labral anterior posterior (SLAP) lesion, arthrosis, and malfunction. The goal of the current study was to facilitate musculoskeletal models in order to estimate glenohumeral instability introduced by muscle weakness due to cuff lesions. Inverse dynamics simulations were used to compute joint reaction forces for several static abduction tasks with different muscle weakness. Results were compared with the existing literature in order to ensure the model validity. Further arm positions taken from activities of daily living, requiring the rotator cuff muscles were modeled and their contribution to joint kinetics computed. Weakness of the superior rotator cuff muscles (supraspinatus; infraspinatus) leads to a deviation of the joint reaction force to the cranial dorsal rim of the glenoid. Massive rotator cuff defects showed higher potential for glenohumeral instability in contrast to single muscle ruptures. The teres minor muscle seems to substitute lost joint torque during several simulated muscle tears to maintain joint stability. Joint instability increases with cuff tear size. Weakness of the upper part of the rotator cuff leads to a joint reaction force closer to the upper glenoid rim. This indicates the comorbidity of cuff tears with SLAP lesions. The teres minor is crucial for maintaining joint stability in case of massive cuff defects and should be uprated in clinical decision-making.}, subject = {Rotatorenmanschettenriss}, language = {en} } @inproceedings{AuerKubowitschKrutschetal., author = {Auer, Simon and Kubowitsch, Simone and Krutsch, Werner and Renkawitz, Tobias and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Effect of mental demand on knee forces in professional youth soccer players}, series = {ISBS Proceedings Archive}, volume = {38}, booktitle = {ISBS Proceedings Archive}, number = {1, Art. 28}, abstract = {Soccer is one of the most popular sports all around the world. It is an injurious type of sport with a focus on lower extremities and high psychological pressure during matches. The stressor is linked with injuries and an increased musculoskeletal loading. This study investigates the influence of cognitive stress on the load profile of the knee joint. Twelve professional youth soccer players performed highly dynamic runs with and without additional cognitive stress. The runs were analysed with a musculoskeletal simulation software. The data analysis shows no difference in knee joint reaction loading under additional mental stress compared to the baseline. Yet running times are significantly lower in the baseline. While there is no increase in the joint loads, the running times indicate an altered movement behaviour when the subjects are exposed to additional mental demand.}, subject = {Kniegelenk}, language = {en} } @article{PutzerAuerMalpicaetal., author = {Putzer, Michael and Auer, Stefan and Malpica, William and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {A numerical study to determine the effect of ligament stiffness on kinematics of the lumbar spine during flexion}, series = {BMC Musculoskeletal Disorders}, volume = {17}, journal = {BMC Musculoskeletal Disorders}, number = {95}, doi = {10.1186/s12891-016-0942-x}, abstract = {Background There is a wide range of mechanical properties of spinal ligaments documented in literature. Due to the fact that ligaments contribute in stabilizing the spine by limiting excessive intersegmental motion, those properties are of particular interest for the implementation in musculoskeletal models. The aim of this study was to investigate the effect of varying ligament stiffness on the kinematic behaviour of the lumbar spine. Methods A musculoskeletal model with a detailed lumbar spine was modified according to fluoroscopic recordings and corresponding data files of three different subjects. For flexion, inverse dynamics analysis with a variation of the ligament stiffness matrix were conducted. The influence of several degrees of ligament stiffness on the lumbar spine model were investigated by tracking ligament forces, disc forces and resulting moments generated by the ligaments. Additionally, the kinematics of the motion segments were evaluated. Results An increase of ligament stiffness resulted in an increase of ligament and disc forces, whereas the relative change of disc force increased at a higher rate at the L4/L5 level (19 \%) than at the L3/L4 (10 \%) level in a fully flexed posture. The same behaviour applied to measured moments with 67 \% and 45 \%. As a consequence, the motion deflected to the lower levels of the lumbar spine and the lower discs had to resist an increase in loading. Conclusions Higher values of ligament stiffness over all lumbar levels could lead to a shift of the loading and the motion between segments to the lower lumbar levels. This could lead to an increased risk for the lower lumbar parts.}, language = {en} } @article{AurbachŠpičkaSuessetal., author = {Aurbach, Maximilian and Špička, Jan and S{\"u}ß, Franz and Vychytil, J. and Havelkov{\´a}, Leonard and Ryba, T. and Dendorfer, Sebastian}, title = {Torus obstacle method as a wrapping approach of the deltoid muscle group for humeral abduction in musculoskeletal simulation}, series = {Journal of Biomechanics}, volume = {109}, journal = {Journal of Biomechanics}, number = {August}, publisher = {Elsevier}, doi = {10.1016/j.jbiomech.2020.109864}, abstract = {Musculoskeletal models of the shoulder complex are valuable research aids to investigate tears of the supraspinatus and the resulting mechanical impact during abduction of the humerus. One of the major contributors to this motion is the deltoid muscle group and for this, an accurate modeling of the lines of action is indispensable. The aim of this work was to utilize a torus obstacle wrapping approach for the deltoids of an existing shoulder model and assess the feasibility of the approach during humeral abduction. The shoulder model from the AnyBody™ modeling system was used as a platform. The size of the tori is based on a magnetic resonance imaging (MRI) approach and several kinematic couplings are implemented to determine the trajectories of the tori during abduction. To assess the model behavior, the moment arms of the virtual muscle elements and the resultant glenohumeral joint reaction force (GHJF) were compared with reference data from the literature during abduction of the humerus in the range 20°-120°. The root mean square error for the anterior, lateral and posterior part between the simulated muscle elements and reference data from the literature was 3.9, 1.7 and 5.8 mm, respectively. The largest deviation occurred on the outer elements of the muscle groups, with 12.6, 10.4 and 20.5 mm, respectively. During abduction, there is no overlapping of the muscle elements and these are in continuous contact with the torus obstacles, thus enabling a continuous force transmission. This results in a rising trend of the resultant GHJF. The torus obstacle approach as a wrapping method for the deltoid muscles provides a guided muscle pathing by simultaneously approximating the curvature of the deltoid muscle. The results from the comparison of the simulated moment arms and the resultant GHJF are in accordance with those in the literature in the range 20°-120° of abduction. Although this study shows the strength of the torus obstacle as a wrapping approach, the method of fitting the tori according to MRI data was not suitable. A cadaver study is recommended to better validate and mathematically describe the torus approach.}, language = {en} } @article{AurbachSpickaSuessetal., author = {Aurbach, Maximilian and Spicka, Jan and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Evaluation of musculoskeletal modelling parameters of the shoulder complex during humeral abduction above 90°}, series = {Journal of Biomechanics}, volume = {106}, journal = {Journal of Biomechanics}, number = {June}, publisher = {Elsevier}, doi = {10.1016/j.jbiomech.2020.109817}, abstract = {Based on electromyographic data and force measurements within the shoulder joint, there is an indication that muscle and resulting joint reaction forces keep increasing over an abduction angle of 90°. In inverse dynamics models, no single parameter could be attributed to simulate this force behaviour accordingly. The aim of this work is to implement kinematic, kinetic and muscle model modifications to an existing model of the shoulder (AnyBody™) and assess their single and combined effects during abduction up to 140° humeral elevation. The kinematics and the EMG activity of 10 test subjects were measured during humeral abduction. Six modifications were implemented in the model: alternative wrapping of the virtual deltoid muscle elements, utilization of a three element Hill model, strength scaling, motion capture driven clavicle elevation/protraction, translation of the GH joint in dependency of the acting forces and an alteration of the scapula/clavicle rhythm. From the six modifications, 16 different combinations were considered. Parameter combinations with the Hill model changed the resultant GH joint reaction force and led to an increase in force during abduction of the humerus above 90°. Under the premise of muscle activities and forces within the GH joint rising after 90° of humeral abduction, we propose that the Hill type muscle model is a crucial parameter for accurately modelling the shoulder. Furthermore, the outcome of this study indicates that the Hill model induces the co-contraction of the muscles of the shoulder without the need of an additional stability criterion for an inverse dynamics approach.}, subject = {Schultergelenk}, language = {en} } @article{SchmitzNeumannNeumannetal., author = {Schmitz, Paul and Neumann, Christoph Cornelius and Neumann, Carsten and Nerlich, Michael and Dendorfer, Sebastian}, title = {Biomechanical analysis of iliac crest loading following cortico-cancellous bone harvesting}, series = {Journal of Orthopaedic Surgery and Research}, volume = {13}, journal = {Journal of Orthopaedic Surgery and Research}, number = {108}, publisher = {Springer Nature}, doi = {10.1186/s13018-018-0822-1}, pages = {1 -- 8}, abstract = {Background Iliac crest bone harvesting is a frequently performed surgical procedure widely used to treat bone defects. The objective of this study is to assess the biomechanical quantities related to risk for pelvic fracture after harvesting an autologous bone graft at the anterior iliac crest. Methods Finite element models with a simulated harvest site (sized 15 × 20 mm, 15 × 35 mm, 30 × 20 mm and 30 × 35 mm) in the iliac wing are created. The relevant loading case is when the ipsilateral leg is lifted off the ground. Musculoskeletal analysis is utilized to compute the muscle and joint forces involved in this motion. These forces are used as boundary conditions for the finite element analyses. Bone tissue stress is analyzed. Results Critical stress peaks are located between the anterior superior iliac spine (ASIS) and the anterior edge of the harvest site. Irrespective of the graft size, the iliac wing does not show any significant stress peaks with the harvest site being 20 to 25 mm posterior to the ASIS. The harvest area itself inhibits the distribution of the forces applied on the ASIS to extend to the posterior iliac wing. This leads to a lack of stress posterior to the harvest site. A balanced stress distribution with no stress peaks appears when the bone graft is taken below the iliac crest. Conclusion A harvest site located at least 20 to 25 mm posterior to the ASIS should be preferred to minimize the risk of iliac fatigue fracture.}, subject = {Beckenkammknochen}, language = {en} } @inproceedings{HornerDendorferKiisetal., author = {Horner, Marc and Dendorfer, Sebastian and Kiis, Arne and Lawrenchuk, Mike and Verma, Gunjan}, title = {A Patient based simulation workflow for orthopedic device design and analysis}, series = {SBC Ortho Workshop, June 2011}, booktitle = {SBC Ortho Workshop, June 2011}, language = {en} } @inproceedings{Dendorfer, author = {Dendorfer, Sebastian}, title = {The effect of multifidus muscles atrophy following disc herniation on disc loading}, series = {Deutsche Gesellschaft f{\"u}r Biomechanik, Murnau, 2011}, booktitle = {Deutsche Gesellschaft f{\"u}r Biomechanik, Murnau, 2011}, language = {en} } @misc{MelznerIsmailRušavyetal., author = {Melzner, Maximilian and Ismail, Khaled and Rušav{\´y}, Zdeněk and Kališ, Vladim{\´i}r and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Musculoskeletal Lower Back Load of Accoucheurs During Delivery}, series = {26th Congress of the European Society of Biomechanics, July 11-14, 2021, Milan, Italy}, journal = {26th Congress of the European Society of Biomechanics, July 11-14, 2021, Milan, Italy}, address = {Milan}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-20208}, abstract = {With the progress in modern medicine, it was possible to significantly reduce the risks of birth for mother and child. One aspect that has received less attention so far is the risk of injury to the accoucheurs (obstetricians and midwives) during the birth process. Indeed, studies indicate that 92\% of midwives suffer from musculoskeletal disorders, with the lower back being the main cause of complaints (72\%). The aim of this study was to investigate two commonly used postural techniques used by accoucheurs during childbirth and to analyze the resulting load on the lower back using the AnyBodyTM musculoskeletal simulation software.}, language = {en} } @inproceedings{AurbachJungtaeublSpickaetal., author = {Aurbach, Maximilian and Jungt{\"a}ubl, Dominik and Spicka, Jan and Dendorfer, Sebastian}, title = {EMG-based validation of musculoskeletal models considering crosstalk}, series = {World Congress Biomechanics, 28-30 June 2018, Dublin}, booktitle = {World Congress Biomechanics, 28-30 June 2018, Dublin}, doi = {10.1109/BIOMDLORE.2018.8467211}, abstract = {BACKGROUND: Validation and verification of multibody musculoskeletal models sEMG is a difficult process because of the reliability of sEMG data and the complex relationship of muscle force and sEMG. OBJECTIVE: This work aims at comparing experimentally recorded and simulated muscle activities considering a numerical model for crosstalk. METHODS: For providing an experimentally derived reference data set, subjects were performing elevations of the arm, where the activities of the contemplated muscle groups were measured by sEMG sensors. Computed muscle activities were further processed and transformed into an artificial electromyographical signal, which includes a numerical crosstalk model. In order to determine whether the crosstalk model provides a better agreement with the measured muscle activities, the Pearson correlation coefficient has been computed as a qualitative way of assessing the curve progression of the data sets. RESULTS: The results show an improvement in the correlation coefficient between the experimental data and the simulated muscle activities when taking crosstalk into account. CONCLUSIONS: Although the correlation coefficient increased when the crosstalk model was utilized, it is questionable if the discretization of both, the crosstalk and the musculoskeletal model, is accurate enough.}, language = {en} } @misc{AuerReinkerSuessetal., author = {Auer, Simon and Reinker, Lukas and S{\"u}ß, Franz and Kubowitsch, Simone and Krutsch, Werner and Weber, Markus and Renkawitz, Tobias and Dendorfer, Sebastian}, title = {Webcast: Effect of mental demand on leg loading in highly dynamic motion}, abstract = {Football players have a high risk of leg muscle injuries, especially when exposed to mental stress. Injuries to muscles of the thigh are common in amateur and professional football, representing almost a third of all injuries. These injuries occur primarily in non-contact situations and from overuse. They can lead to a range of costs, including financial costs associated with treatment as well as those associated with long-term recovery, and absence from training and/or competition. Further, there is a high risk of injury recurrence and subsequent injury.}, language = {en} } @misc{Dendorfer, author = {Dendorfer, Sebastian}, title = {The influence of modeling parameters in the AnyBody Modeling System on muscle and joint loading in the shoulder}, series = {International Shoulder Group Meeting}, volume = {05}, journal = {International Shoulder Group Meeting}, language = {en} } @misc{EgerBergstraesserDendorferetal., author = {Eger, Maximilian and Bergstraesser, Marcel and Dendorfer, Sebastian and Lenich, Andreas and Pfeifer, Christian}, title = {Influence of radial head prosthetic design on humeroradial stability: Validation of a test rig therefore}, series = {DOKU2022, Deutscher Kongress f{\"u}r Orthop{\"a}die und Unfallchirurgie, 25.-28. 10.2022, Berlin}, journal = {DOKU2022, Deutscher Kongress f{\"u}r Orthop{\"a}die und Unfallchirurgie, 25.-28. 10.2022, Berlin}, publisher = {German Medical Science GMS Publishing House}, address = {D{\"u}sseldorf}, doi = {10.3205/22dkou611}, url = {http://nbn-resolving.de/urn:nbn:de:0183-22dkou6115}, language = {en} } @article{WeberMerleNawabietal., author = {Weber, Markus and Merle, Christian and Nawabi, Danyal H. and Dendorfer, Sebastian and Grifka, Joachim and Renkawitz, Tobias}, title = {Inaccurate offset restoration in total hip arthroplasty results in reduced range of motion}, series = {Scientific Reports}, volume = {10}, journal = {Scientific Reports}, number = {13208}, publisher = {Nature}, doi = {10.1038/s41598-020-70059-1}, pages = {9}, abstract = {Offset restoration in total hip arthroplasty (THA) is associated with postoperative range of motion (ROM) and gait kinematics. We aimed to research into the impact of high offset (HO) and standard stems on postoperative ROM. 121 patients received cementless THA through a minimally-invasive anterolateral approach. A 360° hip ROM analysis software calculated impingement-free hip movement based on postoperative 3D-CTs compared to ROM values necessary for activities of daily living (ADL). The same model was then run a second time after changing the stem geometry between standard and HO configuration with the implants in the same position. HO stems showed higher ROM for all directions between 4.6 and 8.9° (p < 0.001) compared with standard stems but with high interindividual variability. In the subgroup with HO stems for intraoperative offset restoration, the increase in ROM was even higher for all ROM directions with values between 6.1 and 14.4° (p < 0.001) compared to offset underrestoration with standard stems. Avoiding offset underrestoration resulted in a higher amount of patients of over 20\% for each ROM direction that fulfilled the criteria for ADL (p < 0.001). In contrast, in patients with standard stems for offset restoration ROM did increase but not clinically relevant by offset overcorrection for all directions between 3.1 and 6.1° (p < 0.001). Offset overcorrection by replacing standard with HO stems improved ROM for ADL in a low number of patients below 10\% (p > 0.03). Patient-individual restoration of offset is crucial for free ROM in THA. Both over and underrestoration of offset should be avoided.}, language = {en} } @misc{MelznerPfeiferSuessetal., author = {Melzner, Maximilian and Pfeifer, Christian and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Muskuloskeletal analysis of elbow stability for common injury patterns}, series = {27th Congress of the European Society of Biomechanics, 26 - 29 June 2022, Porto, Portugal}, journal = {27th Congress of the European Society of Biomechanics, 26 - 29 June 2022, Porto, Portugal}, pages = {654}, language = {en} } @inproceedings{GalibarovAlMunajjedDendorferetal., author = {Galibarov, Pavel E. and Al-Munajjed, Amir Andreas and Dendorfer, Sebastian and Christensen, Soeren Toerholm and Rasmussen, John}, title = {The effect of varying the stiffness of spinal fusion devices on the adjacent levels using multibody dynamics simulation}, series = {Orthopaedic Proceedings}, volume = {94-B}, booktitle = {Orthopaedic Proceedings}, number = {SUPP_XL01 Sep 2012}, pages = {2}, abstract = {INTRODUCTION Several clinical studies demonstrated long-term adjacent-level effects after implantation of spinal fusion devices[1]. These effects have been reported as adjacent joint degeneration and the development of new symptoms correlating with adjacent segment degeneration[2] and the trend has therefore gone to motion preservation devices; however, these effects have not been understood very well and have not been investigated thoroughly[3]. The aim of this study is to investigate the effect of varying the stiffness of spinal fusion devices on the adjacent vertebral levels. Disc forces, moments and facet joint forces were analyzed. METHODS The AnyBody Modeling System was used to compute the in-vivo muscle and joint reaction forces of a musculoskeletal model. The full body model used in this study consists of 188 muscle fascicles in the lumbar spine and more than 1000 individual muscle branches in total. The model has been proposed by de Zee et al.[3], validated by Rasmussen et al.[4] and by Galibarov et al.[5]. The new model[5] determines the individual motions between vertebrae based on the equilibrium between forces acting on the vertebrae from muscles and joints and the passive stiffness in disks and ligaments, figure 1a. An adult of 1.75 m and 75 kg with a spinal implant in L4L5 was modeled. This model was subjected to a flexion-extension motion using different elastic moduli to analyze and compare to a non-implanted scenario. The analyzed variables were vertebral motion, the disc reaction forces and moments, as well as facet joint forces in the treated and the adjacent levels: L2L3, L3L4, L4L5 and L5-Sacrum. RESULTS When introducing a spinal fusion device in the L4L5 joint the reaction forces and moments decreased in this joint with stiffer devices leading to lower joint loads. However, in the adjacent joints, L3L4 and L5Sacrum, an increase was observed when implanting stiffer devices. Similar trends could be found for the L2L3 joint. The loads in the facet joints showed the same trends. While introducing a spinal fusion device reduced the facet joint forces in the treated joint, the loads in the adjacent facet joints were increased according to the stiffness of the implanted device, figure 1b. DISCUSSION While the treated disc joint showed reduced motion and loads, the adjacent levels demonstrated a significant increase. In particular, the increased facet joint forces in the adjacent levels can lead to adjacent level facet pain or accelerated facet joint degeneration. Introducing a device resulted in preventing facet contact and therefore facet joint loads, even using the device with the lowest stiffness. CONCLUSION The presented model shows that clinical complications such as facet joint degeneration in adjacent levels after implantation of spinal fusion device are consistent with the change in the mechanical-stimulus distribution in the system.}, language = {en} } @inproceedings{GalibarovDendorferChristensen, author = {Galibarov, Pavel E. and Dendorfer, Sebastian and Christensen, Soeren Toerholm}, title = {On modelling spine curvature dependent on muscular and external forces in multibody dynamics system}, series = {International Society of Biomechanics (ISB), 13th congress, 2011, Brussels, Belgium}, booktitle = {International Society of Biomechanics (ISB), 13th congress, 2011, Brussels, Belgium}, pages = {2}, abstract = {This paper presents a computational approach for investigating effect of muscular and external forces on curvature of the lumbar spine. Multibody dynamics system is used to compute the lumbar spine curvature using a force-dependent kinematics facility, e.g. this method allows releasing some degrees of freedom in order to be computed based on the current load configuration.}, language = {en} } @inproceedings{RasmussenBichlerChristensenetal., author = {Rasmussen, John and Bichler, R. and Christensen, Soeren Toerholm and Wirix-Speetjens, Roel and Dendorfer, Sebastian and Renkawitz, Tobias}, title = {Subject-specific Musculoskeletal Simulation of Hip Dislocation Risk in Activities of Daily Living}, series = {Proceedings of the 2011 ORS Annual Meeting, Long Beach, CA.}, booktitle = {Proceedings of the 2011 ORS Annual Meeting, Long Beach, CA.}, number = {Paper No. 306}, language = {en} } @inproceedings{RobieDendorferRasmussenetal., author = {Robie, Bruce and Dendorfer, Sebastian and Rasmussen, John and Christensen, Soeren Toerholm}, title = {Axial Rotation Requires Greatest Load in Multifidus Muscle - Potential Association with Low Back Pain?}, series = {Annual Meeting of the AANS/CNS Section on Disorders of the Spine and Peripheral Nerves, 2011, Phoenix, Arizona}, booktitle = {Annual Meeting of the AANS/CNS Section on Disorders of the Spine and Peripheral Nerves, 2011, Phoenix, Arizona}, language = {en} } @inproceedings{GalibarovDendorferRasmussen, author = {Galibarov, Pavel E. and Dendorfer, Sebastian and Rasmussen, John}, title = {Two Computational Models of the Lumbar Spine:}, series = {Proceedings of the 2011 ORS Annual Meeting, Long Beach, CA, vol. Marie Curie Initial Training Network "SpineFX"}, booktitle = {Proceedings of the 2011 ORS Annual Meeting, Long Beach, CA, vol. Marie Curie Initial Training Network "SpineFX"}, language = {en} } @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{BenditzAuerSpoerreretal., author = {Benditz, Achim and Auer, Simon and Sp{\"o}rrer, J.F. and Wolkerstorfer, S. and Grifka, Joachim and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Regarding loads after spinal fusion, every level should be seen separately: a musculoskeletal analysis}, series = {European Spine Journal}, volume = {27}, journal = {European Spine Journal}, number = {8}, publisher = {Springer-Verlag}, doi = {10.1007/s00586-018-5476-5}, pages = {1905 -- 1910}, abstract = {The number of spinal fusion surgeries is steadily increasing and biomechanical consequences are still in debate. The aim of this study is to provide biomechanical insights into the sagittal balance of the spine and to compare spinal load before and after spinal fusion. METHOD: The joint reaction forces of 52 patients were analyzed in proximo-distal and antero-posterior direction from the levels T12-L1 to L5-S1 using musculoskeletal simulations. RESULTS: In 104 simulations, pre-surgical forces were equal to post-surgical. The levels L4-L5 and T12-L1, however, showed increased spinal forces compression forces with higher sagittal displacement. Improved restauration of sagittal balance was accompanied by lower spinal load. AP shear stress, interestingly decreased with sagittal imbalance. CONCLUSION: Imbalanced spines have a risk of increased compression forces at Th12-L1. L4-L5 always has increased spinal loads. These slides can be retrieved under Electronic Supplementary Material.}, subject = {Biomechanische Analyse}, language = {en} } @article{ScheerKubowitschDendorferetal., author = {Scheer, Clara and Kubowitsch, Simone and Dendorfer, Sebastian and Jansen, Petra}, title = {Happy Enough to Relax? How Positive and Negative Emotions Activate Different Muscular Regions in the Back - an Explorative Study}, series = {Frontiers in Psychology}, volume = {Volume 12}, journal = {Frontiers in Psychology}, number = {May 2021}, publisher = {Frontiers Media}, issn = {1664-1078}, doi = {10.3389/fpsyg.2021.511746}, abstract = {Embodiment theories have proposed a reciprocal relationship between emotional state and bodily reactions. Besides large body postures, recent studies have found emotions to affect rather subtle bodily expressions, such as slumped or upright sitting posture. This study investigated back muscle activity as an indication of an effect of positive and negative emotions on the sitting position. The electromyography (EMG) activity of six back muscles was recorded in 31 healthy subjects during exposure to positive and negative affective pictures. A resting period was used as a control condition. Increased muscle activity patterns in the back were found during the exposure to negative emotional stimuli, which was mainly measured in the lumbar and thorax regions. The positive emotion condition caused no elevated activity. The findings show that negative emotions lead to increased differential muscle activity in the back and thus corroborate those of previous research that emotion affects subtle bodily expressions.}, language = {en} } @inproceedings{DendorferKubowitschSuess, author = {Dendorfer, Sebastian and Kubowitsch, Simone and S{\"u}ß, Franz}, title = {How to determine the effect of working conditions on the human body}, series = {11th International Scientific Conference on Production Engineering DEVELOPMENT AND MODERNIZATION OF PRODUCTION (RIM 2017), Sarajevo, Bosnia and Herzegovina}, booktitle = {11th International Scientific Conference on Production Engineering DEVELOPMENT AND MODERNIZATION OF PRODUCTION (RIM 2017), Sarajevo, Bosnia and Herzegovina}, abstract = {Work places and conditions strains the human body, both psychologically and biomechanically. In order to analyse working conditions and in the following to improve them, detailed knowledge about the effect of the different stressors on the body is needed. This manuscript discusses methods on how to evaluate biomechanical and mental loading and its effect on the musculoskeletal system. A possible workflow for the analysis is presented.}, subject = {Arbeitsbedingungen}, 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{WeberAlMunajjedVerkerkeetal., author = {Weber, Tim and Al-Munajjed, Amir Andreas and Verkerke, Gijsbertus Jacob and Dendorfer, Sebastian and Renkawitz, Tobias}, title = {Influence of minimally invasive total hip replacement on hip reaction forces and their orientations}, series = {Journal of Orthopaedic Research}, volume = {32}, journal = {Journal of Orthopaedic Research}, number = {12}, doi = {10.1002/jor.22710}, pages = {1680 -- 1687}, abstract = {Minimally invasive surgery (MIS) is becoming increasingly popular. Supporters claim that the main advantages of MIS total hip replacement (THR) are less pain and a faster rehabilitation and recovery. Critics claim that safety and efficacy of MIS are yet to be determined. We focused on a biomechanical comparison between surgical standard and MIS approaches for THR during the early recovery of patients. A validated, parameterized musculoskeletal model was set to perform a squat of a 50th percentile healthy European male. A bilateral motion was chosen to investigate effects on the contralateral side. Surgical approaches were simulated by excluding the incised muscles from the computations. Resulting hip reaction forces and their symmetry and orientation were analyzed. MIS THR seemed less influential on the symmetry index of hip reaction forces between the operated and nonoperated leg when compared to the standard lateral approach. Hip reaction forces at peak loads of the standard transgluteal approach were 24\% higher on the contralateral side when compared to MIS approaches. Our results suggest that MIS THR contributes to a greater symmetry of hip reaction forces in absolute value as well as force-orientation following THR.}, subject = {H{\"u}ftgelenkprothese}, language = {en} } @article{PenzkoferBarnsteinerDendorfer, author = {Penzkofer, Rainer and Barnsteiner, K. and Dendorfer, Sebastian}, title = {The influence of age, shoe type and kicking direction on the severity of head trauma}, series = {Journal of Forensic Biomechanics}, volume = {5}, journal = {Journal of Forensic Biomechanics}, number = {1}, doi = {10.4172/2090-2697.1000116}, abstract = {In the last few years, increasingly kicks to the head were observed as a criminal offense. This study examined the influence of age, shoe type and kicking direction on the severity of head trauma. Male test persons were divided into two groups "Old" and "Young". Both groups were equipped with light sneakers and combat boots. A standard laboratory crash dummy was used to simulate the victim's body. First, the dummy's head, free floating above the ground, was kicked vertically. Second, the dummy's head was kicked horizontally. Established injury criteria were used to quantify the injury risk. No influence concerning the type of foot wear and no difference between the groups "Old" and "Young" could be found. For all analyses, kicking vertically generally lead to a higher risk for the subject compared to kicking horizontally. In this study, only the integral effect of the kicks could be analyzed. A detailed injury pattern cannot directly be derived from the data. Nevertheless, the presented data show the massive potential of injuries associated with head kicks.}, subject = {Kopfverletzung}, language = {en} } @article{DendorferWeberKennedy, author = {Dendorfer, Sebastian and Weber, Tim and Kennedy, O.}, title = {Musculoskeletal modeling for hip replacement outcome analyses and other applications}, series = {The Journal of the American Academy of Orthopaedic Surgeons}, volume = {22}, journal = {The Journal of the American Academy of Orthopaedic Surgeons}, number = {4}, doi = {10.5435/JAAOS-22-04-268}, pages = {268 -- 269}, subject = {H{\"u}ftgelenkprothese}, language = {en} } @article{LazarevRyabokonHalleretal., author = {Lazarev, I.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} } @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} } @article{DePieriAtzoriFergusonetal., author = {De Pieri, Enrico and Atzori, Federica and Ferguson, Stephen J. and Dendorfer, Sebastian and Leunig, Michael and Aepli, Martin}, title = {Contact force path in total hip arthroplasty: effect of cup medialisation in a whole-body simulation}, series = {HIP International}, volume = {31}, journal = {HIP International}, number = {5}, publisher = {Sage}, doi = {10.1177/1120700020917321}, pages = {624 -- 631}, abstract = {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.}, 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} } @inproceedings{WeberDendorferRenkawitzetal., author = {Weber, Tim and Dendorfer, Sebastian and Renkawitz, Tobias and Dullien, Silvia and Grifka, Joachim}, title = {Clinical gait analysis combined with musculoskeletal modelling - coding a new generation of evaluation instruments}, series = {Deutsche Gesellschaft f{\"u}r Biomechanik, Murnau, 2011}, booktitle = {Deutsche Gesellschaft f{\"u}r Biomechanik, Murnau, 2011}, language = {en} } @inproceedings{PillingSuessKubowitschetal., author = {Pilling, A. and S{\"u}ß, Franz and Kubowitsch, Simone and Dendorfer, Sebastian}, title = {Experimental workflow for determining psychological stress from physiological biosignals}, series = {Jahrestagung der BIOMEDIZINISCHEN TECHNIK und Dreil{\"a}ndertagung der MEDIZINISCHEN PHYSIK, Dresden, Germany, 2017}, booktitle = {Jahrestagung der BIOMEDIZINISCHEN TECHNIK und Dreil{\"a}ndertagung der MEDIZINISCHEN PHYSIK, Dresden, Germany, 2017}, language = {en} } @inproceedings{WeberRenkawitzGrifkaetal., author = {Weber, Tim and Renkawitz, Tobias and Grifka, Joachim and Bulstra, Sjoerd K. and Verkerke, Gijsbertus Jacob and Dendorfer, Sebastian}, title = {The musculoskeletal load scenario of computer-assisted Femur-First THR up to one year after surgery}, series = {VI International Conference on Computational Bioengineering, Barcelona, Sept. 2015}, booktitle = {VI International Conference on Computational Bioengineering, Barcelona, Sept. 2015}, language = {en} } @inproceedings{GrossSuessVerkerkeetal., author = {Gross, Simon and S{\"u}ß, Franz and Verkerke, Gijsbertus Jacob and Dendorfer, Sebastian}, title = {Simulating fatigue in musculoskeletal models using surface electromyography, ECCOMAS Congress, Crete, Greece, 201}, series = {ECCOMAS Congress, Crete, Greece, 2016}, booktitle = {ECCOMAS Congress, Crete, Greece, 2016}, language = {en} } @inproceedings{SuessKubowitschVerkerkeetal., author = {S{\"u}ß, Franz and Kubowitsch, Simone and Verkerke, Gijsbertus Jacob and Dendorfer, Sebastian}, title = {The influence of stress on spinal loading}, series = {ESEM webconference, Dez. 2017}, booktitle = {ESEM webconference, Dez. 2017}, language = {en} } @inproceedings{DendorferKubowitsch, author = {Dendorfer, Sebastian and Kubowitsch, Simone}, title = {The interaction of mental stress and biomechanics}, series = {Health Technology Triangle, Weiden, 2016}, booktitle = {Health Technology Triangle, Weiden, 2016}, language = {en} } @inproceedings{AlMunajjedNolteRasmussenetal., author = {Al-Munajjed, Amir Andreas and Nolte, Daniel and Rasmussen, John and Dendorfer, Sebastian}, title = {Force distribution in the foot during braking - a musculoskeletal approach}, series = {Human Modeling Symposium 2014, Munich, Germany}, booktitle = {Human Modeling Symposium 2014, Munich, Germany}, abstract = {High loads can appear in the individual joints of the human foot while the driver uses the pedals, in particular, during breaking. Measuring these internal forces is very difficult or almost impossible; therefore, advanced models are necessary to perform musculoskeletal simulations. The objective of this investigation was to see what loads are acting in the individual foot joints from the phalanges to calcaneus and talus during different brake scenarios. The Glasgow-Maastricht AnyBody Foot Model with 26 separate segments, connected by joints, ligaments and muscles was used inside the AnyBody Modeling System to compute individual mid foot joint loads. The amount, the direction of the force and additionally also the load insertion point was varied for several simulations. Figure 1: Seated musculoskeletal body model with applied brake force and forces for the lateral, intermediate and medial cuneiform-navicular joint for two different brake forces. The simulation showed that for the different brake scenarios, different muscles will be activated in the human and therefore different loads are apply in the fore-and mid-foot, respectively. The torso of the subject was assumed to be fixed in the seat. Further studies are ongoing to simulate the seat as an elastic element that allows different H-point locations according to the different loadings in the foot from the brake pedal using a new inverse dynamics analysis method called force-dependent kinematics.}, language = {en} } @article{VoellnerWeberWeberetal., author = {V{\"o}llner, Florian and Weber, Tim A. and Weber, Markus and Renkawitz, Tobias and Dendorfer, Sebastian and Grifka, Joachim and Craiovan, Benjamin}, title = {A simple method for determining ligament stiffness during total knee arthroplasty in vivo}, series = {Scientific Reports}, volume = {9}, journal = {Scientific Reports}, publisher = {Nature}, doi = {10.1038/s41598-019-41732-x}, pages = {1 -- 8}, abstract = {A key requirement in both native knee joints and total knee arthroplasty is a stable capsular ligament complex. However, knee stability is highly individual and ranges from clinically loose to tight. So far, hardly any in vivo data on the intrinsic mechanical of the knee are available. This study investigated if stiffness of the native ligament complex may be determined in vivo using a standard knee balancer. Measurements were obtained with a commercially available knee balancer, which was initially calibrated in vitro. 5 patients underwent reconstruction of the force-displacement curves of the ligament complex. Stiffness of the medial and lateral compartments were calculated to measure the stability of the capsular ligament complex. All force-displacement curves consisted of a non-linear section at the beginning and of a linear section from about 80 N onwards. The medial compartment showed values of 28.4 ± 1.2 N/mm for minimum stiffness and of 39.9 ± 1.1 N/mm for maximum stiffness; the respective values for the lateral compartment were 19.9 ± 0.9 N/mm and 46.6 ± 0.8 N/mm. A commercially available knee balancer may be calibrated for measuring stiffness of knee ligament complex in vivo, which may contribute to a better understanding of the intrinsic mechanical behaviour of knee joints.}, subject = {Biomechanische Analyse}, language = {en} } @inproceedings{WeberDendorferBulstraetal., author = {Weber, Tim and Dendorfer, Sebastian and Bulstra, Sjoerd K. and Verkerke, Gijsbertus Jacob and Renkawitz, Tobias}, title = {Biomechanical Outcome after computer-assisted vs. Conventional THR}, series = {ANSYS Conference \& 32th CADFEM Users' Meeting 2014, 04.-06. Juni, N{\"u}rnberg}, booktitle = {ANSYS Conference \& 32th CADFEM Users' Meeting 2014, 04.-06. Juni, N{\"u}rnberg}, language = {en} } @inproceedings{GrossVerkerkeDendorfer, author = {Gross, Simon and Verkerke, Gijsbertus Jacob and Dendorfer, Sebastian}, title = {Combined Experimental and Numerical Approach to Investigate Changes in Muscle Recruitment Pattern of the Back Muscles during Exhausting Exercise}, series = {World Congress Biomechanics Dublin, 2018}, booktitle = {World Congress Biomechanics Dublin, 2018}, abstract = {In recent years, musculoskeletal computation has become a widely used tool to investigate joint and muscle forces within the human body. However, the issue of muscle fatigue is not considered adequately in most models and is a challenging task. One aspect that needs to be examined is the interaction of muscles during an exhausting task. Therefore, an experimental study was designed to analyze the changes of back muscle recruitment pattern during such exercises. In this study 38 subjects (27 male, 11 female, height = 177±8.5 cm, weight = 74.0±13.6 kg) participated. Each subject had to perform three static and three dynamic exhausting exercises where the back muscles were loaded with subject specific forces using a dynamometer adapter especially designed for the trunk muscles. To collect the muscle activity, twelve surface electromyography sensors were applied on the back, and four on the abdominal muscles. Muscle activity and fatigue were analyzed by calculating the maximum voluntary contraction normalized signal and the median frequency. At first the fatigue of m. erector spinae and m. multifidi was analyzed, since these muscles carry the main load during the exercises. Subsequently the activity of the m. trapezius, m. rectus abdominis and m. obliquus externus were investigated to determine recruitment patterns. To gain more detailed information of these patterns a numerical model was built using the AnyBody Modeling System™. Analyzing the measurements, we can observe an increasing muscle activity during isokinetic exercises while the force is constant. Since the activity in the simulation is defined as the current force output divided by the strength of the muscle, the strength parameter was scaled down based on the measured data, assuming a linear force - activity correlation, and using a numerical algorithm considering the influence of cross talk. The results show, that changes in recruitment pattern can be divided into three major subgroups. Prior to total exhaustion, some of the subjects show additional activation of muscles in the trapezius region, while other subjects show an additional activation of abdominal muscles, increasing the intra-abdominal pressure which supports the spine. In the third group an activation in both regions can be observed. The numerical simulations show an increasing activity of abdominal muscles as well as muscles in the upper back. Especially the m. latissimus dorsi shows a significantly higher activity. The results lead to the conclusion that prior to total exhaustion, additional muscles are recruited to support the main muscles. It was shown that abdominal muscles are activated to support back muscles by pressurizing the trunk cavity to delay total exhaustion as long as possible. In conclusion, the results show that changes in muscle recruitment pattern need to be considered when introducing muscle fatigue to musculoskeletal models.}, language = {en} } @article{AuerKurbowitschSuessetal., author = {Auer, Simon and Kurbowitsch, Simone and S{\"u}ß, Franz and Renkawitz, Tobias and Krutsch, Werner and Dendorfer, Sebastian}, title = {Mental stress reduces performance and changes musculoskeletal loading in football-related movements}, series = {Science and Medicine in Football}, volume = {5}, journal = {Science and Medicine in Football}, number = {4}, publisher = {Taylor \& Francis}, doi = {10.1080/24733938.2020.1860253}, pages = {323 -- 329}, abstract = {Purpose: Football players have a high risk of leg muscle injuries, especially when exposed to mental stress. Hence, this study investigated the musculoskeletal response of elite youth football players during highly dynamic movements under stress. The hypothesis is that mental stress reduces performance and changes the muscular forces exerted. Materials \& methods: Twelve elite youth football players were subjected to mental stress while performing sports-specific change-of-direction movements. A modified version of the d2 attention test was used as stressor. The kinetics are computed using inverse dynamics. Running times and exerted forces of injury-prone muscles were analysed. Results: The stressor runs were rated more mentally demanding by the players (p = 0.006, rs = 0.37) with unchanged physical demand (p = 0.777, rs = 0.45). This resulted in 10\% longer running times under stress (p < 0.001, d = -1.62). The musculoskeletal analysis revealed higher peak muscle forces under mental stress for some players but not for others. Discussion: The study shows that motion capture combined with musculoskeletal computation is suitable to analyse the effects of stress on athletes in highly dynamic movements. For the first time in football medicine, our data quantifies an association between mental stress with reduced football players' performance and changes in muscle force.}, language = {en} } @article{PutzerEhrlichRasmussenetal., author = {Putzer, Michael and Ehrlich, Ingo and Rasmussen, John and Gebbeken, Norbert and Dendorfer, Sebastian}, title = {Sensitivity of lumbar spine loading to anatomical parameters}, series = {Journal of Biomechanics}, volume = {49}, journal = {Journal of Biomechanics}, number = {6}, publisher = {Elsevier Science}, doi = {10.1016/j.jbiomech.2015.11.003}, pages = {953 -- 958}, abstract = {Musculoskeletal simulations of lumbar spine loading rely on a geometrical representation of the anatomy. However, this data has an inherent inaccuracy. This study evaluates the influence of defined geometrical parameters on lumbar spine loading utilising five parametrised musculoskeletal lumbar spine models for four different postures. The influence of the dimensions of vertebral body, disc, posterior parts of the vertebrae as well as the curvature of the lumbar spine was studied. Additionally, simulations with combinations of selected parameters were conducted. Changes in L4/L5 resultant joint force were used as outcome variable. Variations of the vertebral body height, disc height, transverse process width and the curvature of the lumbar spine were the most influential. These parameters can be easily acquired from X-rays and should be used to morph a musculoskeletal lumbar spine model for subject-specific approaches with respect to bone geometry. Furthermore, the model was very sensitive to uncommon configurations and therefore, it is advised that stiffness properties of discs and ligaments should be individualised.}, subject = {Wirbels{\"a}ule}, language = {en} } @article{DendorferHammerLenich, author = {Dendorfer, Sebastian and Hammer, Joachim and Lenich, Andreas}, title = {Characterisation and testing of biomaterials}, series = {Technology and Health Care}, volume = {19}, journal = {Technology and Health Care}, number = {5}, doi = {10.3233/THC-2011-0644}, pages = {357 -- 371}, subject = {Biomaterial}, language = {en} }