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Over the past decade, veno-venous extracorporeal membrane oxygenation (vvECMO) has been increasingly utilized in respiratory failure in patients. This study presents our institution´s experience focusing on the life span of ECMO systems reflecting the performance of a particular system. A retrospective review of our ECMO database identified 461 adult patients undergoing vvECMO (2010-2017). Patients that required more than one system and survived the first exchange >24 hours (n = 139) were included. Life span until the first exchange and exchange criteria were analyzed for all systems (PLS, Cardiohelp HLS-set, both Maquet Cardiopulmonary, Rastatt, Germany; Deltastream/Hilite7000LT, iLA-activve, Xenios/NovaLung, Heilbronn, Germany; ECC.O5, LivaNova, Mirandola, Italy). At our ECMO center, the frequency of a system exchange was 30%. The median (IQR) life span was 9 (6-12) days. There was no difference regarding the different systems (p = 0.145 and p = 0.108, respectively). However, the Deltastream systems were exchanged more frequently due to elective technical complications (e. g. worsened gas transfer, development of coagulation disorder, increased bleedings complications) compared to the other exchanged systems (p = 0.013). In summary, the used ECMO systems are safe and effective for acute respiratory failure. There is no evidence for the usage of a specific system. Only the increased predictability of an imminent exchange preferred the usage of a Deltastream system. However, the decision to use a particular system should not depend solely on the possible criteria for an exchange.
Degradation and release of tannic acid from an injectable tissue regeneration bead matrix in vivo
(2021)
The development of multifunctional biomaterials as both tissue regeneration and drug delivery devices is currently a major focus in biomedical research. Tannic Acid (TA), a naturally occurring plant polyphenol, displays unique medicinal abilities as an antioxidant, an antibiotic, and as an anticancer agent. TA has applications in biomaterials acting as a crosslinker in polymer hydrogels improving thermal stability and mechanical properties. We have developed injectable cell seeded collagen beads crosslinked with TA for breast reconstruction and anticancer activity following lumpectomy. This study determined the longevity of the bead implants by establishing a degradation time line and TA release profile in vivo. Beads crosslinked with 0.1% TA and 1% TA were compared to observe the differences in TA concentration on degradation and release. We found collagen/TA beads degrade at similar rates in vivo, yet are resistant to complete degradation after 16 weeks. TA is released over time in vivo through diffusion and cellular activity. Changes in mechanical properties in collagen/TA beads before implantation to after 8 weeks in vivo also indicate loss of TA over a longer period of time. Elastic moduli decreased uniformly in both 0.1% and 1% TA beads. This study establishes that collagen/TA materials can act as a drug delivery system, rapidly releasing TA within the first week following implantation. However, the beads retain TA long term allowing them to resist degradation and remain in situ acting as a cell scaffold and tissue filler. This confirms its potential use as an anticancer and minimally invasive breast reconstructive device following lumpectomy.
Ein interdisziplinäres Forschungsprojekt der Ostbayerischen Hochschule Regensburg untersucht, inwiefern Telemedizin und digitale Anwendungen die Therapie und Pflege von Menschen mit Schlaganfall in ihrem häuslichen Umfeld unterstützen, ihre Lebensqualität beeinflussen und die intersektorale Versorgung verbessern kann.
Blood flow in channels of varying diameters <500μm exhibits strong non-linear effects. Multiphase finite volume approaches are feasible, but still computationally costly. Here, the feasibility of applying convolutional neural networks for blood flow prediction in artificial lungs is investigated. Training targets are precomputed using an Eulerian two-phase approach. To match with experimental data, the interphase drag and lift, as well as intraphase shear-thinning are adapted. A recursively branching regression network and convolution/deconvolution networks with plain skip connections and densely connected skips are investigated. A priori knowledge is incorporated in the loss functional to prevent the network from learning non-physical solutions. Inference from neural networks is approximately six orders of magnitude faster than the classical finite volume approach. Even if resulting in comparably coarse flow fields, the neural network predictions can be used as close to convergence initial solutions greatly accelerating classical flow computations.
"Topographic Shift": a new digital approach to evaluating topographic changes of the female breast
(2021)
Purpose
To assess precise topographic changes of the breast, objective documentation and evaluation of pre- and postoperative results are crucial. New technologies for mapping the body using digital, three-dimensional surface measurements have offered novel ways to numerically assess the female breast. Due to the lack of clear demarcation points of the breast contour, the selection of landmarks on the breast is highly dependent on the examiner, and, therefore, is prone to error when conducting before-after comparisons of the same breast. This study describes an alternative to volumetric measurements, focusing on topographic changes of the female breast, based on three-dimensional scans.
Method
The study was designed as an interventional prospective study of 10 female volunteers who had planned on having aesthetic breast augmentation with anatomical, textured implants. Three dimensional scans of the breasts were performed intraoperatively, first without and then with breast implants. The topographic change was determined as the mean distance between two three-dimensional layers before and after augmentation. This mean distance is defined as the Topographic Shift. Results The mean implant volume was 283 cc (SD = 68.6 cc, range = 210-395 cc). The mean Topographic Shift was 7.4 mm (SD = 1.9 mm, range = 4.8-10.7 mm). The mean Topographic Shifts per quadrant were: I: 8.0 mm (SD = 3.3 mm); II: 9.2 mm (SD = 3.1 mm); III: 6.9 mm (SD = 3.5 mm); IV: 1.9 mm (SD = 4.3 mm).
Conclusion
The Topographic Shift, describing the mean distance between two three-dimensional layers (for example before and after a volume changing therapy), is a new approach that can be used for assessing topographic changes of a body area. It was found that anatomical, textured breast implants cause a topographic change, particularly on the upper breast, in quadrant II, the decollete.
One of the fundamental challenges in L-PBF of filigree geometries, such as aortic stents used in biomedical applications, is the requirement for a robust yet easily removable support structure that allows each component to be successfully fabricated without distortion. To solve this challenge, an integrative experimental approach was attempted in the present study by identifying an optimal support structure design and an optimized support removal strategy for this design. The specimens were manufactured using four different support structure designs based on the geometry exposed to the laser beam during the L-PBF. Support removal procedures included sand blasting (SB), glass bead blasting (GB), and electrochemical polishing (ECP). The two best-performing designs (line and cross) were chosen due to shorter lead times and lower material consumption. As an additional factor that indicates a stable design, the breaking load requirement to remove the support structures was determined. A modified line support with a 145° included angle was shown to be the best support structure design in terms of breaking load, material consumption, and manufacturing time. All three procedures were used to ensure residue-free support removal for this modified line support design, with ECP proving to be the most effective.
Vitamin C is an essential nutrient for humans and is involved in a plethora of health-related functions. Several studies have shown a connection between vitamin C intake and an improved resistance to infections that involves the immune system. However, the body cannot store vitamin C and both the elevated oral intake, and the intravenous application have certain disadvantages. In this study, we wanted to show a new formulation for the liposomal packaging of vitamin C. Using freeze etching electron microscopy, we show the formed liposomes. With a novel approach of post-processing procedures of real-time sonography that combines enhancement effects by contrast-like ultrasound with a transducer, we wanted to demonstrate the elevated intestinal vitamin C resorption on four participants. With the method presented in this study, it is possible to make use of the liposomal packaging of vitamin C with simple household materials and equipment for intake elevation. For the first time, we show the enhanced resorption of ingested liposomes using microbubble enhanced ultrasound imaging.
Resting motor threshold and magnetic field output of the figure-of-8 and the double-cone coil
(2020)
The use of the double-cone (DC) coil in transcranial magnetic stimulation (TMS) is promoted with the notion that the DC coil enables stimulation of deeper brain areas in contrast to conventional figure-of-8 (Fo8) coils. However, systematic comparisons of these two coil types with respect to the spatial distribution of the magnetic field output and also to the induced activity in superficial and deeper brain areas are limited. Resting motor thresholds of the left and right first dorsal interosseous (FDI) and tibialis anterior (TA) were determined with the DC and the Fo8 coil in 17 healthy subjects. Coils were orientated over the corresponding motor area in an angle of 45 degrees for the hand area with the handle pointing in posterior direction and in medio-lateral direction for the leg area. Physical measurements were done with an automatic gantry table using a Gaussmeter. Resting motor threshold was higher for the leg area in contrast to the hand area and for the Fo8 in contrast to the DC coil. Muscle by coil interaction was also significant providing higher differences between leg and hand area for the Fo8 (about 27%) in contrast to the DC coil (about 15%). Magnetic field strength was higher for the DC coil in contrast to the Fo8 coil. The DC coil produces a higher magnetic field with higher depth of penetration than the figure of eight coil.
BACKGROUND:
Due to their corrugated profile, dragonfly wings have special aerodynamic characteristics during flying and gliding. OBJECTIVE: The aim of this study was to create a realistic 3D model of a dragonfly wing captured with a high-resolution micro-CT. To represent geometry changes in span and chord length and their aerodynamic effects, numerical investigations are carried out at different wing positions. METHODS:
The forewing of a Camacinia gigantea was captured using a micro-CT. After the wing was adapted an error-free 3D model resulted. The wing was cut every 5 mm and 2D numerical analyses were conducted in Fluent® 2020 R2 (ANSYS, Inc., Canonsburg, PA, USA). RESULTS: The highest lift coefficient, as well as the highest lift-to-drag ratio, resulted at 0 mm and an angle of attack (AOA) of 5∘. At AOAs of 10∘ or 15∘, the flow around the wing stalled and a Kármán vortex street behind the wing becomes
CONCLUSIONS:
The velocity is higher on the upper side of the wing compared to the lower side. The pressure acts vice versa. Due to the recirculation zones that are formed in valleys of the corrugation pattern the wing resembles the form of an airfoil.
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)
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.
Objective
The risk of in-stent restenosis can be considerably reduced by stents eluting cytostatic compounds. We created a novel drug-eluting stent system that includes several new features in the rapidly evolving field of stent-based drug delivery.
Methods and Results
The aim of the present study was the preclinical evaluation of a stent-coating system permitting individual, on-site coating of stents with a unique microporous surface allowing for individualizable, dose-adjustable, and multiple coatings with identical or various compounds, designated ISAR (individualizable drug-eluting stent system to abrogate restenosis). Stents were coated with 0.75% rapamycin solution, and high-performance liquid chromatography (HPLC)-based determination of drug release profile indicated drug release for >21 days. Rapamycin-eluting microporous (REMP) stents implanted in porcine coronary arteries were safe. To determine the efficacy of REMP stents, this novel drug-eluting stent platform was compared with the standard sirolimus-eluting stent. At 30 days, in-stent neointima formation in porcine coronary arteries was similar in both groups, yielding a significant decrease of neointimal area and injury-dependent neointimal thickness compared with bare-metal stents.
Conclusion
The ISAR drug-eluting stent platform as a novel concept for stent coating allows for a safe, effective, on-site stent coating process, thus justifying further clinical evaluation to decrease in-stent restenosis in humans.
In-stent neointima formation can be successfully attenuated by drug-eluting stents. We introduce a novel conceptual approach for stent-coating that allows for dose-adjustable, on-site stent coating process if desired with multiple compounds. Microporous stents coated with rapamycin proved safe and effective for the limitation of neointima formation in a porcine coronary stent model.
Aims
Drug-eluting stents (DES) represent a major advance in interventional cardiology. Along with the success shown, current DES also present limitations related to the presence of polymer-coating, fixed drug, and dose used. With the ISAR (Individualized Drug-Eluting Stent System to Abrogate Restenosis) project, a DES system has been developed that permits individualized choice of the drug and dose to use for the given patient. The objective of this prospective dose finding study was to assess the feasibility, safety, and efficacy of a polymer-free on-site stent coating with increasing rapamycin doses.
Methods and results
In this dose finding study, 602 patients were sequentially enrolled in four groups: microporous bare metal stent (BMS), DES stents coated with a 0.5, 1.0, and 2.0% rapamycin solution. The angiographic in-segment restenosis rate at follow-up angiography was the primary study endpoint. In-segment restenosis was significantly reduced from 25.9% with BMS to 18.9, 17.2, and 14.7% with 0.5, 1.0, and 2.0% rapamycin-eluting stents, respectively (P=0.024). Similarly, the need for target lesion revascularization at 1 year follow-up was reduced from 21.5% with BMS to 16.4, 12.6, and 8.8% with 0.5, 1.0, and 2.0% rapamycin-eluting stents, respectively (P=0.006).
Conclusion
The placement of polymer-free stents coated on-site with rapamycin is feasible and safe. Furthermore, a dose-dependent efficacy in restenosis prevention is achievable with this new DES concept.
Vascular damage develops with diverging severity during and after percutaneous coronary intervention with stent placement and is the prevailing stimulus for in-stent restenosis. Previous work has failed to link mechanical data obtained in a realistic in vivo or in vitro environment with data collected during imaging processes. We investigated whether specimens of porcine right coronary arteries soften when indented with a stent strut shaped structure, and if the softening results from damage mechanisms inside the fibrillar collagen structure. To simulate the multiaxial loading scenario of a stented coronary artery, we developed the testing device ‘LAESIO’ that can measure differences in the stress-stretch behavior of the arterial wall before and after the indentation of a strut-like stamp. The testing protocol was optimized according to preliminary experiments, more specifically equilibrium and relaxation tests. After chemical fixation of the specimens and subsequent tissue clearing, we performed three-dimensional surface and second-harmonic generation scans on the deformed specimens. We analyzed and correlated the mechanical response with structural parameters of high-affected tissue located next to the stamp indentation and low-affected tissue beyond the injured area. The results reveal that damage mechanisms, like tissue compression as well as softening, fiber dispersion, and the lesion extent, are direction-dependent, and the severity of them is linked to the strut orientation, indentation pressure, and position. The findings highlight the need for further investigations by applying the proposed methods to human coronary arteries. Additional data and insights might help to incorporate the observed damage mechanisms into material models for finite element analyses to perform more accurate simulations of stent-implantations.
Experimental and mathematical characterization of coronary polyamide-12 balloon catheter membranes
(2020)
The experimental quantification and modeling of the multiaxial mechanical response of polymer membranes of coronary balloon catheters have not yet been carried out. Due to the lack of insights, it is not shown whether isotropic material models can describe the material response of balloon catheter membranes expanded with nominal or higher, supra-nominal pressures. Therefore, for the first time, specimens of commercial polyamide-12 balloon catheters membranes were investigated during uniaxial and biaxial loading scenarios. Furthermore, the influence of kinematic effects on the material response was observed by comparing results from quasi-static and dynamic biaxial extension tests. Novel clamping techniques are described, which allow to test even tiny specimens taken from the balloon membranes. The results of this study reveal the semi-compliant, nonlinear, and viscoelastic character of polyamide-12 balloon catheter membranes. Above nominal pressure, the membranes show a pronounced anisotropic mechanical behavior with a stiffer response in the circumferential direction. The anisotropic feature intensifies with an increasing strain-rate. A modified polynomial model was applied to represent the realistic mechanical response of the balloon catheter membranes during dynamic biaxial extension tests. This study also includes a compact set of constitutive model parameters for the use of the proposed model in future finite element analyses to perform more accurate simulations of expanding balloon catheters.
Background:
Lipofilling is one of the most often performed surgical procedures in plastic and reconstructive surgery. Lipoaspirates provide a ready source of stem cells and secreted factors that contribute to neoangiogenesis and fat graft survival. However, the regulations about the enrichment of these beneficial cells and factors are ambiguous. In this study, the authors tested whether a combination of centrifugation and homogenization allowed the enrichment of viable stem cells in lipoaspirates through the selective removal of tumescent solution, blood, and released lipids without significantly affecting the cell secretome.
Methods:
Human lipoaspirate was harvested from six different patients using water jet–assisted liposuction. Lipoaspirate was homogenized by first centrifugation (3584 rpm for 2 minutes), shear strain (10 times intersyringe processing), and second centrifugation (3584 rpm for 2 minutes). Stem cell enrichment was shown by cell counting after stem cell isolation. Lipoaspirate from different processing steps (unprocessed, after first centrifugation, after homogenization, after second centrifugation) was incubated in serum-free cell culture medium for mass spectrometric analysis of secreted proteins.
Results:
Lipoaspirate homogenization leads to a significant 2.6 ± 1.75-fold enrichment attributable to volume reduction without reducing the viability of the stem cells. Protein composition of the secretome did not change significantly after tissue homogenization. Considering the enrichment effects, there were no significant differences in the protein concentration of the 83 proteins found in all processing steps.
Conclusions:
Stem cells can be enriched mechanically without significantly affecting the composition of secreted proteins. Shear-assisted enrichment of lipoaspirate constitutes no substantial manipulation of the cells’ secretome.
Results of WICOVIR Gargle Pool PCR Testing in German Schools Based on the First 100,000 Tests
(2021)
Background:
Opening schools and keeping children safe from SARS-CoV-2 infections at the same time is urgently needed to protect children from direct and indirect consequences of the COVID-19 pandemic. To achieve this goal, a safe, efficient, and cost-effective SARS-CoV-2 testing system for schools in addition to standard hygiene measures is necessary.
Methods:
We implemented the screening WICOVIR concept for schools in the southeast of Germany, which is based on gargling at home, pooling of samples in schools, and assessment of SARS-CoV-2 by pool rRT-PCR, performed decentralized in numerous participating laboratories. Depooling was performed if pools were positive, and results were transmitted with software specifically developed for the project within a day. Here, we report the results after the first 13 weeks in the project.
Findings:
We developed and implemented the proof-of-concept test system within a pilot phase of 7 weeks based on almost 17,000 participants. After 6 weeks in the main phase of the project, we performed >100,000 tests in total, analyzed in 7,896 pools, identifying 19 cases in >100 participating schools. On average, positive children showed an individual CT value of 31 when identified in the pools. Up to 30 samples were pooled (mean 13) in general, based on school classes and attached school staff. All three participating laboratories detected positive samples reliably with their previously established rRT-PCR standard protocols. When self-administered antigen tests were performed concomitantly in positive cases, only one of these eight tests was positive, and when antigen tests performed after positive pool rRT-PCR results were already known were included, 3 out of 11 truly positive tests were also identified by antigen testing. After 3 weeks of repetitive WICOVIR testing twice weekly, the detection rate of positive children in that cohort decreased significantly from 0.042 to 0.012 (p = 0.008).
Interpretation:
Repeated gargle pool rRT-PCR testing can be implemented quickly in schools. It is an effective, valid, and well-received test system for schools, superior to antigen tests in sensitivity, acceptance, and costs.
Advances in additive manufacturing enable the production of tailored lattice structures and thus, in principle, coronary stents. This study investigates the effects of process-related irregularities, heat and surface treatment on the morphology, mechanical response, and expansion behavior of 316L stainless steel stents produced by laser powder bed fusion and provides a methodological approach for their numerical evaluation. A combined experimental and computational framework is used, based on both actual and computationally reconstructed laser powder bed fused stents. Process-related morphological deviations between the as-designed and actual laser powder bed fused stents were observed, resulting in a diameter increase by a factor of 2-2.6 for the stents without surface treatment and 1.3-2 for the electropolished stent compared to the as-designed stent. Thus, due to the increased geometrically induced stiffness, the laser powder bed fused stents in the as-built (7.11 ± 0.63 N) or the heat treated condition (5.87 ± 0.49 N) showed increased radial forces when compressed between two plates. After electropolishing, the heat treated stents exhibited radial forces (2.38 ± 0.23 N) comparable to conventional metallic stents. The laser powder bed fused stents were further affected by the size effect, resulting in a reduced yield strength by 41% in the as-built and by 59% in the heat treated condition compared to the bulk material obtained from tensile tests. The presented numerical approach was successful in predicting the macroscopic mechanical response of the stents under compression. During deformation, increased stiffness and local stress concentration were observed within the laser powder bed fused stents. Subsequent numerical expansion analysis of the derived stent models within a previously verified numerical model of stent expansion showed that electropolished and heat treated laser powder bed fused stents can exhibit comparable expansion behavior to conventional stents. The findings from this work motivate future experimental/numerical studies to quantify threshold values of critical geometric irregularities, which could be used to establish design guidelines for laser powder bed fused stents/lattice structures.
Biomechanical Analysis of the Right Elevated Glenohumeral Joint in Violinists during Legato-Playing
(2021)
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.
Customized additively manufactured (laser powder bed fused (L-PBF)) stents could improve the treatment of complex lesions by enhancing stent-artery conformity. However, geometric irregularities inherent for L-PBF stents are expected to influence not only their mechanical behavior but also their interaction with the artery. In this study, the influence of geometrical irregularities on stent-artery interaction is evaluated within a numerical framework. Thus, computed arterial stresses induced by a reconstructed L-PBF stent model are compared to those induced by the intended stent model (also representing a stent geometry obtained from conventional manufacturing processes) and a modified CAD stent model that accounts for the increased strut thickness inherent for L-PBF stents. It was found that, similar to conventionally manufactured stents, arterial stresses are initially related to the basic stent design/topology, with the highest stresses occurring at the indentations of the stent struts. Compared to the stent CAD model, the L-PBF stent induces distinctly higher and more maximum volume stresses within the plaque and the arterial wall. In return, the modified CAD model overestimates the arterial stresses induced by the L-PBF stent due to its homogeneously increased strut thickness and thus its homogeneously increased geometric stiffness compared with the L-PBF stent. Therefore, the L-PBF-induced geometric irregularities must be explicitly considered when evaluating the L-PBF stent-induced stresses because the intended stent CAD model underestimates the arterial stresses, whereas the modified CAD model overestimates them. The arterial stresses induced by the L-PBF stent were still within the range of values reported for conventional stents in literature, suggesting that the use of L-PBF stents is conceivable in principle. However, because geometric irregularities, such as protruding features from the stent surface, could potentially damage the artery or lead to premature stent failure, further improvement of L-PBF stents is essential.
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)
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.
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.
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)
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.
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.
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.
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.
Anatomical differences between individuals are often neglected in musculoskeletal models, but they are necessary in case of subject-specific questions regarding the lumbar spine. A modification of models to each subject is complex and the effects on lumbar loading are difficult to assess. The objective of this thesis is to create a validated musculoskeletal model of the human body, which facilitates a subject-specific modification of the geometry of the lumbar spine. Furthermore, important parameters are identified in sensitivity studies and a case study regarding multifidus muscle atrophy after a disc herniation is conducted. Therefore, a generic model is heavily modified and a semi-automatic process is implemented. This procedure remodels the geometry of the lumbar spine to a subject-specific one on basis of segmented medical images. The resulting five models are validated with regard to the lumbar loading at the L4/L5 level. The influence of lumbar ligament stiffness is determined by changing the stiffness values of all lumbar ligaments in eleven steps during a flexion motion. Sensitivities of lumbar loading to an altered geometry of the lumbar spine are identified by varying ten lumbar parameters in simulations with each model in four postures. The case study includes an analysis of the loading of the multifidus muscle and of the lumbar discs throughout various stages of disc herniation. This time each model performs four motions with two different motion rhythms. The results indicate that lumbar motion and loading is dependent on lumbar ligament stiffness. Furthermore, subject-specific modelling of the lumbar spine should include at least the vertebral height, disc height and lumbar lordosis. The results of the case study suggest that an overloading of the multifidus muscle could follow disc herniation. Additionally, a subsequent atrophy of the muscles could expose adjacent levels to an increased loading, but these findings are highly dependent on the individual.
This article presents first results of artificial aging experi-ments by ultraviolet (UV) irradiation on thermoplasticmaterials conducted as an intent of the research project Thermoplastic Composite Structures (TheCoS) in colla-boration of the Ostbayerische Technische Hochschule(OTH) Regensburg and the University of West Bohemia(UWB) in Pilsen as part of a cross-border cooperation. In technical applications, thermoplastic materials are oftenaffected by aging and a related deterioration of the mechanical properties. Therefore, it is necessary to identifythe aging behavior of thermoplastic materials. For this,experiments were performed for three thermoplasticmaterials, namely polypropylene (PP), ultra high mole -cular weight polyethylene (UHMWPE) and high impactstrength polystyrene (HIPS). For these experiments, a UV chamber was constructed according to the internationalstandard EN ISO 4892-3 for simulation of exposurebehind window glass. The results are evaluated by testing the flexural strength and the dynamic mechanicalresponse after a selected period of time under UV lightand then compared to untreated test specimens.
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.
Mental stress reduces performance and changes musculoskeletal loading in football-related movements
(2020)
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.
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.