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Muskuloskeletal analysis of elbow stability for common injury patterns (2022)
Melzner, Maximilian ; Pfeifer, Christian ; Süß, Franz ; Dendorfer, Sebastian
Biomechanik und muskuloskeletale Simulation (2022)
Melzner, Maximlian ; Dendorfer, Sebastian
Comparing calculated and measured muscle activity of thigh muscles in dynamic motion. (2022)
Auer, Simon ; Reinker, Lukas ; Süß, Franz ; Dendorfer, Sebastian
Biomechanische Aspekte bei Sportverletzungen (2022)
Dendorfer, Sebastian
Einfluss der Rotatorenmanschette auf die glenohumerale Stabilität (2022)
Englert, Carsten ; Dendorfer, Sebastian
Towards ergonomic working - machine learning algorithms and musculoskeletal modeling (2021)
Suess, Franz ; Melzner, Maximilian ; Dendorfer, Sebastian
Ergonomic workplaces lead to fewer work-related musculoskeletal disorders and thus fewer sick days. There are various guidelines to help avoid harmful situations. However, these recommendations are often rather crude and often neglect the complex interaction of biomechanical loading and psychological stress. This study investigates whether machine learning algorithms can be used to predict mechanical and stress-related muscle activity for a standardized motion. For this purpose, experimental data were collected for trunk movement with and without additional psychological stress. Two different algorithms (XGBoost and TensorFlow) were used to model the experimental data. XGBoost in particular predicted the results very well. By combining it with musculoskeletal models, the method shown here can be used for workplace analysis but also for the development of real-time feedback systems in real workplace environments.
Biomechanical analysis of the right elevated glenohumeral joint in violinists during legato-playing (2022)
Saffert, Anne-Sophie ; Melzner, Maximilian ; Dendorfer, Sebastian
BACKGROUND: Many statistics reveal that violin players suffer most often from musculoskeletal disorders compared to musicians of other instrument groups. A common phenomenon, especially observed in violin beginners, is the tendency to elevate the right shoulder during playing the violin. This can probably lead to serious disorders in long-term practice with repetitive movements. OBJECTIVE: For this reason, this study investigated the relationship between the right shoulder elevation and the force in the right glenohumeral joint during violin playing. It was hypothesized that the forces in the right glenohumeral joint are higher during playing with the right shoulder raised compared to playing in normal posture. METHODS: Motion capture data from four experienced violinists was recorded and processed by means of musculoskeletal simulation to get the force and elevation angle while playing with raised shoulder and in normal position. RESULTS: The results indicate that the absolute values of the resulting force, as well as the forces in the mediolateral, inferosuperior, and anteroposterior directions, are higher in playing the violin with the shoulder raised than in a normal posture. CONCLUSIONS: Elevating the right shoulder while playing the violin may pose a potential problem.
Biomechanical Analysis of the Right Elevated Glenohumeral Joint in Violinists during Legato-Playing (2021)
Saffert, Anne-Sophia ; Melzner, Maximilian ; Dendorfer, Sebastian
BACKGROUND: Many statistics reveal that violin players suffer most often from musculoskeletal disorders compared to musicians of other instrument groups. A common phenomenon, especially observed in violin beginners, is the tendency to elevate the right shoulder during playing the violin. This can probably lead to serious disorders in long-term practice with repetitive movements. OBJECTIVE: For this reason, this study investigated the relationship between the right shoulder elevation and the force in the right glenohumeral joint during violin playing. It was hypothesized that the forces in the right glenohumeral joint are higher during playing with the right shoulder raised compared to playing in normal posture. METHODS: Motion capture data from four experienced violinists was recorded and processed by means of musculoskeletal simulation to get the force and elevation angle while playing with raised shoulder and in normal position. RESULTS: The results indicate that the absolute values of the resulting force, as well as the forces in the mediolateral, inferosuperior, and anteroposterior directions, are higher in playing the violin with the shoulder raised than in a normal posture. CONCLUSIONS: Elevating the right shoulder while playing the violin may pose a potential problem.
Towards Ergonomic working - machine learning algorithms and muscloskeletal modeling (2021)
Suess, Franz ; Melzner, Maximilian ; Dendorfer, Sebastian
Electromyography-Based Validation of a Musculoskeletal Hand Model (2021)
Melzner, Maximilian ; Engelhardt, Lucas ; Simon, Ulrich ; Dendorfer, Sebastian
Regarding the prevention of injuries and rehabilitation of the human hand, musculoskeletal simulations using an inverse dynamics approach allow for insights of the muscle recruitment and thus acting forces on the hand. Currently, several hand models from various research groups are in use, which are mainly validated by the comparison of numerical and anatomical moment arms. In contrast to this validation and model-building technique by cadaver studies, the aim of this study is to further validate a recently published hand model [1] by analyzing numerically calculated muscle activities in comparison to experimentally measured electromyographical signals of the muscles. Therefore, the electromyographical signals of 10 hand muscles of five test subjects performing seven different hand movements were measured. The kinematics of these tasks were used as input for the hand model, and the numerical muscle activities were computed. To analyze the relationship between simulated and measured activities, the time difference of the muscle on- and off-set points was calculated, which resulted in a mean on- and off-set time difference of 0.58 s between the experimental data and the model. The largest differences were detected for movements that mainly addressed the wrist. One major issue comparing simulated and measured muscle activities of the hand is cross-talk. Nevertheless, the results show that the hand model fits the experiment quite accurately despite some limitations and is a further step toward patient-specific modeling of the upper extremity.
Musculoskeletal lower back load of accoucheurs during childbirth – A pilot and feasibility study (2021)
Melzner, Maximilian ; Ismail, Khaled ; Rušavy, Zdenek ; Kališ, Vladimír ; Süß, Franz ; Dendorfer, Sebastian
Introduction: Back problems represent one of the leading causes of accouchers' work-related musculoskeletal morbidities. The correct execution of birth-related maneuvers including manual perineal protection is crucial not only for the mother and child but also for obstetricians and midwives to reduce any strain on their musculoskeletal system. Therefore, the overall aim of this study was to test the feasibility of determining the effect of different accouchers' postures (standing and kneeling) on their musculoskeletal system. Methods: The biomechanical analysis is based on musculoskeletal simulations that included motion recordings of real deliveries as well as deliveries conducted on a birthing simulator. These simulations were then used to determine individual joints' loads. Results: In the kneeling posture, both a low intra-operator variability and a lower average maximum load of the lower back was observed. For the standing position the spine load was reduced by pivoting the elbow on the accouchers' thigh, which in turn was associated with a significantly greater load on the shoulder joint. Conclusion: The study demonstrated the feasibility of our technique to assess joints loads. It also provided initial data indicating that a posture that reduces spinal flexion and tilt, achieved in this study by the kneeling, can significantly reduce the strain on the practitioner's musculoskeletal system.
Webcast: Effect of mental demand on leg loading in highly dynamic motion (2020)
Auer, Simon ; Reinker, Lukas ; Süß, Franz ; Kubowitsch, Simone ; Krutsch, Werner ; Weber, Markus ; Renkawitz, Tobias ; Dendorfer, Sebastian
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.
AnyBody Webcast - A new musculoskeletal AnyBody™ detailed hand model (2020)
Melzner, Maximilian ; Engelhardt, Lucas
Musculoskeletal Lower Back Load of Accoucheurs During Delivery (2021)
Melzner, Maximilian ; Ismail, Khaled ; Rušavý, Zdeněk ; Kališ, Vladimír ; Süß, Franz ; Dendorfer, Sebastian
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.
Evaluation of muscle recruitment and muscle models in musculoskeletal simulation of dynamic motion (2021)
Auer, Simon ; Reinker, Lukas ; Dendorfer, Sebastian
Musculoskeletal simulation plays an increasingly important role in sports biomechanics. In the last years, the field of application widened from orthopaedics and ergonomics to sports [1]. A muscle recruitment algorithm with a quadratic objective function is usually used to calculate muscle activity in dynamic movements. The agreement of calculated and measured thigh muscle activity has already been investigated [2]. They found a strong agreement for sprinting and running, while the correlation decreased for side-cutting manoeuvres. Nevertheless, the influence of different muscle recruitment criteria on muscle activity in dynamic musculoskeletal simulations is currently unknown. Hence, this study aimed to analyse the effect of different muscle recruitment criteria and muscle models on the correlation of numerical and measured muscle activity in highly dynamic movements.
The impact of anatomical uncertainties on the predictions of a musculoskeletal hand model – a sensitivity study (2021)
Melzner, Maximilian ; Suess, Franz ; Dendorfer, Sebastian
Outputs of musculoskeletal models should be considered probabilistic rather than deterministic as they are affected by inaccuracies and estimations associated with the development of the model. One of these uncertainties being critical for modeling arises from the determination of the muscles' line of action and the physiological cross-sectional area. Therefore, the aim of this study was to evaluate the outcome sensitivity of model predictions from a musculoskeletal hand model in comparison to the uncertainty of these input parameters. For this purpose, the kinematics and muscle activities of different hand movements (abduction of the fingers, abduction of the thumb, and flexion of the thumb) were recorded. One thousand simulations were calculated for each movement using the Latin hypercube sampling method with a corresponding variation of the muscle origin/insertion points and the cross-sectional area. Comparing the standard hand to simulations incorporating uncertainties of input parameters shows no major deviations in on- and off-set time point of muscle activities. About 60% of simulations are located within a ± 30% interval around the standard model concerning joint reaction forces. The comparison with the variation of the input data leads to the conclusion that the standard hand model is able to provide not over-scattered outcomes and, therefore, can be considered relatively stable. These results are of practical importance to the personalization of a musculoskeletal model with subject-specific bone geometries and hence changed muscle line of action.
Kinematic pelvic tilt during gait alters functional cup position in total hip arthroplasty (2021)
Weber, Markus ; Suess, Franz ; Jerabek, Seth ; Meyer, Matthias ; Grifka, Joachim ; Renkawitz, Tobias ; Dendorfer, Sebastian
Static pelvic tilt impacts functional cup position in total hip arthroplasty (THA). In the current study we investigated the effect of kinematic pelvic changes on cup position. In the course of a prospective controlled trial postoperative 3D-computed tomography (CT) and gait analysis before and 6 and 12 months after THA were obtained in 60 patients. Kinematic pelvic motion during gait was measured using Anybody Modeling System. By fusion with 3D-CT, the impact of kinematic pelvic tilt alterations on cup anteversion and inclination was calculated. Furthermore, risk factors correlating with high pelvic mobility were evaluated. During gait a high pelvic range of motion up to 15.6° exceeding 5° in 61.7% (37/60) of patients before THA was found. After surgery, the pelvis tilted posteriorly by a mean of 4.0 ± 6.6° (p < .001). The pelvic anteflexion led to a mean decrease of −1.9 ± 2.2° (p < .001) for cup inclination and −15.1 ± 6.1° (p < .001) for anteversion in relation to the anterior pelvic plane (APP). Kinematic pelvic changes resulted in a further change up to 2.3° for inclination and up to 12.3° for anteversion. In relation to the preoperative situation differences in postoperative cup position ranged from −4.4 to 4.6° for inclination and from −7.8 to 17.9° for anteversion, respectively. Female sex (p < .001) and normal body weight (p < .001) correlated with high alterations in pelvic tilt. Kinematic pelvic changes highly impact cup anteversion in THA. Surgeons using the APP as reference should aim for a higher anteversion of about 15° due to the functional anteflexion of the pelvis during gait.
Happy Enough to Relax? How Positive and Negative Emotions Activate Different Muscular Regions in the Back - an Explorative Study (2021)
Scheer, Clara ; Kubowitsch, Simone ; Dendorfer, Sebastian ; Jansen, Petra
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.
The influence of modeling parameters in the AnyBody Modeling System on muscle and joint loading in the shoulder (2021)
Dendorfer, Sebastian
Influence of TAL-TATS surgery on energy production of Tricepts Surae - A musculoskeletal modeling evaluation (2020)
Visscher, Rosa ; Wyss, C. ; Singh, Navrag B. ; Taylor, William R. ; Dendorfer, Sebastian ; Rutz, E. ; Brunner, Reinald
EMG-based validation of musculoskeletal models considering crosstalk (2018)
Aurbach, Maximilian ; Jungtäubl, Dominik ; Spicka, Jan ; Dendorfer, Sebastian
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.
A new musculoskeletal AnyBody™ detailed hand model (2020)
Engelhardt, Lucas ; Melzner, Maximilian ; Havelkova, Linda ; Fiala, Pavel ; Christen, Patrik ; Dendorfer, Sebastian ; Simon, Ulrich
Musculoskeletal research questions regarding the prevention or rehabilitation of the hand can be addressed using inverse dynamics simulations when experiments are not possible. To date, no complete human hand model implemented in a holistic human body model has been fully developed. The aim of this work was to develop, implement, and validate a fully detailed hand model using the AnyBody Modelling System (AMS) (AnyBody, Aalborg, Denmark). To achieve this, a consistent multiple cadaver dataset, including all extrinsic and intrinsic muscles, served as a basis. Various obstacle methods were implemented to obtain with the correct alignment of the muscle paths together with the full range of motion of the fingers. These included tori, cylinders, and spherical ellipsoids. The origin points of the lumbrical muscles within the tendon of the flexor digitorum profundus added a unique feature to the model. Furthermore, the possibility of an entire patient-specific scaling based on the hand length and width were implemented in the model. For model validation, experimental datasets from the literature were used, which included the comparison of numerically calculated moment arms of the wrist, thumb, and index finger muscles. In general, the results displayed good comparability of the model and experimental data. However, the extrinsic muscles showed higher accordance than the intrinsic ones. Nevertheless, the results showed, that the proposed developed inverse dynamics hand model offers opportunities in a broad field of applications, where the muscles and joint forces of the forearm play a crucial role.
Mental stress reduces performance and changes musculoskeletal loading in football-related movements (2020)
Auer, Simon ; Kurbowitsch, Simone ; Süß, Franz ; Renkawitz, Tobias ; Krutsch, Werner ; Dendorfer, Sebastian
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.
Validation of a detailed lower extremity model based on the Klein Horsman data set (2009)
Andersen, Michael Skipper ; de Zee, Mark ; Dendorfer, Sebastian ; MacWilliams, Bruce ; Rasmussen, John
The influence of in-vivo muscle forces on the stress distribution in a vertebral body during activities of daily living (2009)
Dendorfer, Sebastian ; Rasmussen, John
Forces on a clavicles midshaft fracture and influence of fracture type (2009)
Dendorfer, Sebastian ; Englert, Carsten
The influence of muscle forces on biomechanical fracture fixation simulations – from in-vivo forces to tissue strains (2009)
Dendorfer, Sebastian ; Carbes, S. ; Rasmussen, John
Herniation Induces 55% Increase in Load of Key Stabilizing Muscle – Impact on Herniation Treatment Devices? (2010)
Robie, Bruce ; Rasmussen, John ; Christensen, Soeren Toerholm ; Dendorfer, Sebastian
The Effect of Spinal Disc Herniation on Multifidus Muscles (2010)
Dendorfer, Sebastian ; Rasmussen, John ; Christensen, Soeren Toerholm ; Robie, Bruce
Einfluss der Muskelkräfte, des Bewegungsausmaßes und der Bruchform auf die Kraftübertragung des Implantat-Knochenverbundes am Beispiel der Claviculafraktur im mittleren Drittel (2010)
Englert, Carsten ; Müller, F. ; Dendorfer, Sebastian
Fragestellung Es soll in dieser Computersimulationsstudie untersucht werden, wie der Osteosyntheseverbund Platte mit Schrauben im Verbund mit einer im mittleren Drittel gebrochenen Clavicula durch das Bewegungsausmaß in vivo belastet ist. Was sind die grundlegenden Kräfte die auf Clavicula und Implantat wirken und welchen Einfl uss hat die Bruchform. Methodik Die Muskel- und Gelenkkräfte sowie die Belastung des Implantatverbundes wurden mit einer muskuloskelletalen Simulationssoftware (AnyBody Technology, V.4) berechnet. Hierfür wurden mit einem komplexen Model des menschlichen Körpers folgende Bewegungen analysiert: eine Flexion von 160° und Abduktion 160° mit einem Gewicht von 2 kg in der Hand. Aus CT-Patientendaten wurden zwei dreidimensionale Modelle des Clavicula-Implantat Verbundes gebildet, die sich in der Frakturform unterscheiden (Querfraktur und vertikale Fraktur). In beiden Modellen wurde eine Claviculaosteosynthese in superiorer Position mit einer 6 Loch LCP mit 2 Schrauben pro Hauptfragment verwendet. Die Materialeigenschaften wurden aus der Dichte des Materials sowie aus Literaturdaten verwendet. Die Muskel- und Gelenkkräfte aus der muskuloskelletalen Berechnung wurden auf das Finite Elemente Modell übertragen und die Spannungen und Dehnungen des Implantat-Knochenverbundes wurden berechnet. Ergebnisse Es zeigte sich, dass die simulierte in vivo Belastung stark abhängig vom Flexionswinkel ist. Das Implantat ist in der superioren Lage auf Biegung belastet, welche maximale Werte im Überschulterniveau erreicht. Die Bruchform mit anatomischer Reposition und Kontakt der Hauptfragmente zueinander führt zu einer deutlichen Entlastung des Osteosyntheseverbundes im Vergleich zu einer Bruchform mit vertikaler Fraktur. Schlussfolgerung Aus den Analysen ist eine Positionierung der Plattenosteosynthese für die im mittleren Drittel frakturierte Clavicula in anterior-superiorer Lage wünschenswert. Die anatomische Reposition entlastet den Osteosyntheseverbund und sollte möglichst erreicht werden. Die Nachbehandlung sollte ein Bewegungsausmaß für den Arm für 4 Wochen für einfache Bruchformen auf 70° Flexion und Abduktion limitieren und für komplexe Bruchformen diese Limitierung ausgedehnt werden.
A Patient based simulation workflow for orthopedic device design and analysis (2011)
Horner, Marc ; Dendorfer, Sebastian ; Kiis, Arne ; Lawrenchuk, Mike ; Verma, Gunjan
Axial Rotation Requires Greatest Load in Multifidus Muscle – Potential Association with Low Back Pain? (2011)
Robie, Bruce ; Dendorfer, Sebastian ; Rasmussen, John ; Christensen, Soeren Toerholm
Subject-specific Musculoskeletal Simulation of Hip Dislocation Risk in Activities of Daily Living (2011)
Rasmussen, John ; Bichler, R. ; Christensen, Soeren Toerholm ; Wirix-Speetjens, Roel ; Dendorfer, Sebastian ; Renkawitz, Tobias
On modelling spine curvature dependent on muscular and external forces in multibody dynamics system (2011)
Galibarov, Pavel E. ; Dendorfer, Sebastian ; Christensen, Soeren Toerholm
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.
The effect of varying the stiffness of spinal fusion devices on the adjacent levels using multibody dynamics simulation (2011)
Galibarov, Pavel E. ; Al-Munajjed, Amir Andreas ; Dendorfer, Sebastian ; Christensen, Soeren Toerholm ; Rasmussen, John
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.
Two Computational Models of the Lumbar Spine: (2011)
Galibarov, Pavel E. ; Dendorfer, Sebastian ; Rasmussen, John
Design studies on hip prosthesis using patient specific data (2011)
Putzer, Michael ; Weber, Tim ; Dendorfer, Sebastian
Clinical gait analysis combined with musculoskeletal modelling – coding a new generation of evaluation instruments (2011)
Weber, Tim ; Dendorfer, Sebastian ; Renkawitz, Tobias ; Dullien, Silvia ; Grifka, Joachim
The effect of multifidus muscles atrophy following disc herniation on disc loading (2011)
Dendorfer, Sebastian
Influence of kyphosis on spinal loading (2012)
Spreiter, G. ; Galibarov, Pavel E. ; Dendorfer, Sebastian ; Ferguson, Stephen J.
Eine biomechanische Bewertung verschiedener Belastungsszenarios nach der Implantierung einer Hüft-Totalendoprothese (2012)
Weber, Tim ; Stezowski, P. ; Dullien, Silvia ; Dendorfer, Sebastian
Validation of a Motion Capture Laboratory and a new marker-placement protcol for clinical applications (2013)
Weber, Tim ; Dullien, Silvia ; Grifka, Joachim ; Renkawitz, Tobias ; Dendorfer, Sebastian
Eine biomechanische Bewertung verschiedener Belastungsszenarien nach Implantierung einer Hüft-Totalendoprothese (2012)
Weber, Tim ; Stezowski, P. ; Dullien, Silvia ; Putzer, Michael ; Dendorfer, Sebastian
Biomechanical outcome after computer-assisted vs. conventional THR – study concept and preliminary gait analysis results (2012)
Weber, Tim ; Dullien, Silvia ; Putzer, Michael ; Dendorfer, Sebastian ; Renkawitz, Tobias
Influence of vertebral parameters on lumbar spine loading (2013)
Putzer, Michael ; Galibarov, Pavel E. ; Dendorfer, Sebastian
Einführung in die Mechanik (2013)
Dendorfer, Sebastian
Experimentelle Untersuchung der Belastungen im Kopf beim Treten (2013)
Dendorfer, Sebastian ; Penzkofer, Rainer
Innovationen in der Medizintechnik (2013)
Dendorfer, Sebastian
Musculoskeletal simulations to investigate the influence of vertebral geometrical parameters on lumbar spine loading (2014)
Putzer, Michael ; Penzkofer, Rainer ; Ehrlich, Ingo ; Rasmussen, John ; Gebbeken, Norbert ; Dendorfer, Sebastian
Biomechanical Outcome after computer-assisted vs. Conventional THR (2014)
Weber, Tim ; Dendorfer, Sebastian ; Bulstra, Sjoerd K. ; Verkerke, Gijsbertus Jacob ; Renkawitz, Tobias
Force distribution in the foot during braking – a musculoskeletal approach (2014)
Al-Munajjed, Amir Andreas ; Nolte, Daniel ; Rasmussen, John ; Dendorfer, Sebastian
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.
Mechanobiology – Impact on regeneration and degradation (2015)
Dendorfer, Sebastian
Musculoskeletal modeling for orthopedic surgery – Applications and chances (2015)
Weber, Tim ; Dendorfer, Sebastian ; Bulstra, Sjoerd K. ; Verkerke, Gijsbertus Jacob ; Renkawitz, Tobias
Navigated Femur First Total Hip Arthroplasty leads to improved Biomechanical Outcome after surgery (2015)
Weber, Tim ; Dendorfer, Sebastian ; Bulstra, Sjoerd K. ; Grifka, Joachim ; Verkerke, Gijsbertus Jacob ; Renkawitz, Tim
Numerische und experimentelle Untersuchungen an der Wirbelsäule (2015)
Süß, Franz ; Putzer, Michael ; Dendorfer, Sebastian
Positionsanalyse von winkelstabilen Plattenosteosynthesesystemen zur Versorgung von Metatarsalfrakturen mit Hilfe von patientenspezifischen biomechanischen Modellen (2015)
Billing, A. ; Götz, J. ; Weber, Tim ; Dendorfer, Sebastian
Sensitivity of lumbar spine loading to anatomical parameters (2015)
Putzer, Michael ; Dendorfer, Sebastian
Thoracolumbar spine model with articulated rigcage for the prediction of dynamic spinal loading (2015)
Ignasiak, Dominika ; Dendorfer, Sebastian ; Ferguson, Stephen J.
Biomechanics of computer-assisted vs. conventional THR after one year follow up (2015)
Weber, Tim ; Renkawitz, Tobias ; Bulstra, Sjoerd K. ; Grifka, Joachim ; Verkerke, Gijsbertus Jacob ; Dendorfer, Sebastian
Biomechanical comparison of the dorsal femur condyles and the iliac crest in terms of failure behavior (2015)
Penzkofer, Rainer ; Grechenig, S. ; Kujat, Richard ; Angele, Peter ; Dendorfer, Sebastian
The musculoskeletal load scenario of computer-assisted Femur-First THR up to one year after surgery (2015)
Weber, Tim ; Renkawitz, Tobias ; Grifka, Joachim ; Bulstra, Sjoerd K. ; Verkerke, Gijsbertus Jacob ; Dendorfer, Sebastian
Verbessert die computerassistierte Femur First Operationstechnik für die Hüftendoprothetik den muskuloskelettalen Lastfall auf das Hüftgelenk? (2015)
Weber, Tim ; Dendorfer, Sebastian ; Grifka, Joachim ; Weber, Markus ; Wörner, Michael ; Dullien, Silvia ; Verkerke, Gijsbertus Jacob ; Renkawitz, Tobias
Biomechanik des Alterns (2016)
Dendorfer, Sebastian
Virtuelle Menschmodelle – von der Bewegung zur Belastung (2016)
Dendorfer, Sebastian
Simulating fatigue in musculoskeletal models using surface electromyography, ECCOMAS Congress, Crete, Greece, 201 (2016)
Gross, Simon ; Süß, Franz ; Verkerke, Gijsbertus Jacob ; Dendorfer, Sebastian
Älterwerden muss auch mal wehtun! (2016)
Dendorfer, Sebastian
The influence of stress on spinal loading (2016)
Süß, Franz ; Kubowitsch, Simone ; Verkerke, Gijsbertus Jacob ; Dendorfer, Sebastian
Influence of biceps tenotomy and tenodesis on post-operative shoulder strength (2017)
Muehling, M. ; Englert, Carsten ; Dendorfer, Sebastian
Muscular imbalances during experimentally induced stress (2017)
Kubowitsch, Simone ; Süß, Franz ; Jansen, Petra ; Dendorfer, Sebastian
The influence of mental stress on spinal disc loading and muscle activity (2017)
Süß, Franz ; Kubowitsch, Simone ; Verkerke, Gijsbertus Jacob ; Dendorfer, Sebastian
Investigation of external load dependent static and dynamic muscle fatigue (2017)
Gross, Simon ; Verkerke, Gijsbertus Jacob ; Dendorfer, Sebastian
Experimental workflow for determining psychological stress from physiological biosignals (2017)
Pilling, A. ; Süß, Franz ; Kubowitsch, Simone ; Dendorfer, Sebastian
EMG-Based Validation of Musculoskeletal Models Considering Crosstalk (2018)
Jungtäubl, Dominik ; Aurbach, Maximilian ; Melzner, Maximilian ; Spicka, Jan ; Süß, Franz ; Dendorfer, Sebastian
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.
Comparison of dynamic muscular imbalances in back pain patients and healthy controls (2018)
Kubowitsch, Simone ; Süß, Franz ; Jansen, Petra ; Dendorfer, Sebastian
Combined Experimental and Numerical Approach to Investigate Changes in Muscle Recruitment Pattern of the Back Muscles during Exhausting Exercise (2018)
Gross, Simon ; Verkerke, Gijsbertus Jacob ; Dendorfer, Sebastian
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.
Achilles tendon lengthening alters stresses in the growth plate (2018)
Seefried, C. ; Aurbach, Maximilian ; Wyss, C. ; Dendorfer, Sebastian
Investigation of cognitive stress induced changes in spinal disc forces due to altered kinematics and muscle activity (2018)
Süß, Franz ; Kubowitsch, Simone ; Verkerke, Gijsbertus Jacob ; Dendorfer, Sebastian
Psychologie und Biomechanik – Integrierte Betrachtung von Muskelrekrutierung (2018)
Kubowitsch, Simone ; Dendorfer, Sebastian
Musculoskeletal modelling of the shoulder – effects on muscle recruitment and joint reaction force (2019)
Aurbach, Maximilian ; Spicka, Jan ; Süß, Franz ; Dendorfer, Sebastian
Effect of dual tasking on muscular imbalances (2019)
Kubowitsch, Simone ; Süß, Franz ; Jansen, Petra ; Dendorfer, Sebastian
A new musculoskeletal AnyBody detailed hand model (2019)
Engelhardt, Lucas ; Melzner, Maximilian ; Havelkova, Linda ; Fiala, Pavel ; Rybarova, Martina ; Christen, Patrik ; Dendorfer, Sebastian ; Simon, Ulrich
The AnyBody™ Modeling System (AMS) [1], is an universally used musculoskeletal simulation software using inverse dynamics. Until now, no complete human hand model is known in the AMS. Also considering other musculoskeletal software platforms, just one detailed entire hand model is recently published [2] but is only based on one subject. The aim of this work is to implement a full detailed hand model for the AMS including all extrinsic and intrinsic muscles using data by the UWB gained through an anatomical study of ten cadaver hands.
The influence of cognitive stress on muscle activation and spinal disc load (2019)
Süß, Franz ; Kubowitsch, Simone ; Rasmussen, John ; Verkerke, Gijsbertus Jacob ; Dendorfer, Sebastian
Cognitive stress increases muscle forces in dynamic football specific movements (2019)
Auer, Simon ; Niebler, Michael ; Eiglsperger, Josef ; Kubowitsch, Simone ; Renkawitz, Tobias ; Achenbach, Leonard ; Krutsch, Werner ; Dendorfer, Sebastian
A new musculoskeletal AnyBody detailed hand model validated by electromyography (2019)
Melzner, Maximilian ; Engelhardt, Lucas ; Havelkova, Leonard ; Simon, Ulrich ; Dendorfer, Sebastian
The AnyBody™ Modeling System (AMS) [1], is an universally used musculoskeletal simulation software using inverse dynamics. Until now, no complete human hand model is known in the AMS. Also considering other musculoskeletal software platforms, just one detailed entire hand model is recently published [2] but is only based on one subject. The aim of this work is to implement a full detailed hand model for the AMS including all extrinsic and intrinsic muscles using data by the UWB gained through an anatomical study of ten cadaver hands.
The impact of the hill type muscle model on the glenohumeral joint reaction force (2019)
Aurbach, Maximilian ; Süß, Franz ; Dendorfer, Sebastian
Virtuelle Modelle der oberen Extremität (2019)
Dendorfer, Sebastian
The influence of mental stress on the musculoskeletal system (2020)
Dendorfer, Sebastian
Sensitivity evaluation of a musculoskeletal hand model using Latin hypercube sampling (2020)
Melzner, Maximilian ; Engelhardt, Leonard ; Süß, Friedrich ; Dendorfer, Sebastian
Kognitiver Stress führt zu unphysiologisch erhöhten Kniebelastungen im Profifußball (2020)
Auer, Simon ; Krutsch, Werner ; Renkawitz, Tobias ; Kubowitsch, Simone ; Süß, Franz ; Dendorfer, Sebastian
Effect of mental demand on leg loading in highly dynamic motion (2020)
Auer, Simon ; Krutsch, Werner ; Renkawitz, Tobias ; Kubowitsch, Simone ; Süß, Franz ; Dendorfer, Sebastian
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.
Änderung der Gelenkreaktionskraft bei Schädigung des medialen Bandapparates im Ellenbogen (2020)
Melzner, Maximilian ; Pfeifer, Christian ; Alt, V. ; Süß, Franz ; Dendorfer, Sebastian
Biomechanical evaluation and optimisation of countermeasure exercises (2009)
Dendorfer, Sebastian
How much iron to pump? The determination of muscle forces for activities of daily living (2008)
Dendorfer, Sebastian
Cyclic loading and microstructure of cancellous bone (2008)
Hammer, Joachim ; Dendorfer, Sebastian
The interaction of mental stress and biomechanics (2016)
Dendorfer, Sebastian ; Kubowitsch, Simone
Inaccurate offset restoration in total hip arthroplasty results in reduced range of motion (2020)
Weber, Markus ; Merle, Christian ; Nawabi, Danyal H. ; Dendorfer, Sebastian ; Grifka, Joachim ; Renkawitz, Tobias
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.
Torus obstacle method as a wrapping approach of the deltoid muscle group for humeral abduction in musculoskeletal simulation (2020)
Aurbach, Maximilian ; Špička, Jan ; Süß, Franz ; Vychytil, J. ; Havelková, Leonard ; Ryba, T. ; Dendorfer, Sebastian
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.
Effect of mental demand on knee forces in professional youth soccer players (2020)
Auer, Simon ; Kubowitsch, Simone ; Krutsch, Werner ; Renkawitz, Tobias ; Süß, Franz ; Dendorfer, Sebastian
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.
Contact force path in total hip arthroplasty: effect of cup medialisation in a whole-body simulation (2020)
De Pieri, Enrico ; Atzori, Federica ; Ferguson, Stephen J. ; Dendorfer, Sebastian ; Leunig, Michael ; Aepli, Martin
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.
Evaluation of musculoskeletal modelling parameters of the shoulder complex during humeral abduction above 90° (2020)
Aurbach, Maximilian ; Spicka, Jan ; Süß, Franz ; Dendorfer, Sebastian
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.
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