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  • 1.
    Fuchs, Gabriel
    et al.
    Karolinska Inst, Dept Physiol & Pharmacol, Stockholm, Sweden.;Sundsvall Reg Hosp, Dept Cardiol, Sundsvall, Sweden..
    Berg, Niclas
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Centres, BioMEx. KTH, School of Engineering Sciences (SCI), Mechanics.
    Broman, L. Mikael
    Karolinska Inst, Dept Physiol & Pharmacol, Stockholm, Sweden.;Karolinska Univ Hosp, ECMO Ctr Karolinska, Pediat Perioperat Med & Intens Care, Stockholm, Sweden..
    Wittberg, Lisa Prahl
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Centres, BioMEx.
    Flow-induced platelet activation in components of the extracorporeal membrane oxygenation circuit2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 13985Article in journal (Refereed)
    Abstract [en]

    Extracorporeal membrane oxygenation (ECMO) is used for rescue in severe respiratory and/or circulatory failure. The patient's blood is pumped over artificial surfaces in the ECMO circuit. A platelet activation model was applied to study the potential thrombogenicity of ECMO circuit components: the centrifugal blood pump, cannulae, and tubing connectors. Based on the accumulated effect of the scalar form of the stress acting on the platelet over time, the activation model enables assessment of platelet activation and pinpoints regions of elevated activation risk in a component. Numerical simulations of the flow in different components of the ECMO circuit was carried out where the activation level is a function of the impact of local stress and its history along the path that the platelets follow. The results showed that the pump carried the largest risk for platelet activation followed by the reinfusion cannula and lastly the connectors. Pump thrombogenicity was mainly due to long residence time and high shear-rate while the connector showed a high level of non-stationary shear-rate that in turn may contribute to the formation of aggregates through direct platelet activation or through high shear-rate modulation of the vWF multimers.

  • 2.
    Krishnan, Rakesh
    et al.
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL. KTH, School of Engineering Sciences (SCI), Centres, BioMEx. Univ Gavle, Dept Elect Math & Nat Sci, Gavle, Sweden..
    Bjorsell, Niclas
    Univ Gavle, Dept Elect Math & Nat Sci, Gavle, Sweden..
    Smith, Christian
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL. KTH, School of Engineering Sciences (SCI), Centres, BioMEx.
    Segmenting Humeral Submovements using Invariant Geometric Signatures2017In: 2017 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS (IROS) / [ed] Bicchi, A Okamura, A, IEEE , 2017, p. 6951-6958Conference paper (Refereed)
    Abstract [en]

    Discrete submovements are the building blocks of any complex movement. When robots collaborate with humans, extraction of such submovements can be very helpful in applications such as robot-assisted rehabilitation. Our work aims to segment these submovements based on the invariant geometric information embedded in segment kinematics. Moreover, this segmentation is achieved without any explicit kinematic representation. Our work demonstrates the usefulness of this invariant framework in segmenting a variety of humeral movements, which are performed at different speeds across different subjects. Our results indicate that this invariant framework has high computational reliability despite the inherent variability in human motion.

  • 3. Naili, J. E.
    et al.
    Broström, E. W.
    Gutierrez-Farewik, Elena M.
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics. KTH, School of Engineering Sciences (SCI), Centres, BioMEx.
    Schwartz, M. H.
    The Centre Of Mass Trajectory Is A Sensitive And Responsive Measure Of Compensations For Pain And Weakness Among Individuals With Knee Osteoarthritis Performing A Sit-To-Stand Test2017In: Osteoarthritis and Cartilage, ISSN 1063-4584, E-ISSN 1522-9653, Vol. 25, p. S125-S126Article in journal (Other academic)
  • 4. Naili, J. E.
    et al.
    Broström, E. W.
    Gutierrez-Farewik, Elena M.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, BioMEx.
    Schwartz, M. H.
    The centre of mass trajectory is a sensitive and responsive measure of functional compensations in individuals with knee osteoarthritis performing the five times sit-to-stand test2018In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 62, p. 140-145Article in journal (Refereed)
    Abstract [en]

    This study aimed to evaluate whether the trajectory of the body's Centre of Mass (CoM) is a sensitive and responsive measure of functional compensations in individuals with knee osteoarthritis (OA) performing the Five Times Sit-to-Stand test (5STS). This prospective study included 21 individuals with OA and 21 age- and gender-matched controls. Motion analysis data was collected while participants performed the 5STS, one month prior and one year after total knee arthroplasty (TKA). Pain was evaluated using a visual analogue scale. Repeated measures ANOVAs were used to evaluate (1) differences in the area under the curve (AUC) of CoM trajectories, and (2) the effect of number of sit-to-stand cycles on the AUC. Preoperatively, individuals with OA displayed a larger contralateral shift (p = 0.009) and forward displacement of the CoM (p < 0.004) than controls. Postoperatively, CoM trajectories of OA individuals were not statistically different from controls. However, upon comparison of specific cycles, OA individuals displayed a larger forward displacement during the final cycle. Pain was significantly reduced postoperatively (p = 0.001). The CoM trajectory appears to be a sensitive and responsive measure of functional compensations. The increased contralateral shift of the CoM represents a strategy to reduce pain by unloading the affected knee. Postoperatively, when pain was substantially reduced, OA individuals were comparable to controls. The increased forward CoM displacement characterises a strategy to reduce muscular effort by reducing the required knee extension moment. Postoperatively, OA individuals were comparable to controls in all cycles but the last, possibly suggesting residual muscle weakness.

  • 5.
    Naili, J. E.
    et al.
    Karolinska Inst, Dept Womens & Childrens Hlth, Stockholm, Sweden..
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, BioMEx.
    Stalman, A.
    Karolinska Inst, Dept Mol Med & Surg, Stockholm Sports Trauma Res Ctr, Stockholm, Sweden.;Sophiahemmet, Capio Artro Clin, Stockholm, Sweden..
    Valentin, A.
    Karolinska Inst, Dept Mol Med & Surg, Stockholm Sports Trauma Res Ctr, Stockholm, Sweden.;Elisabethsjukhuset, Uppsala, Sweden..
    Skorpil, M.
    Karolinska Inst, Dept Mol Med & Surg, Stockholm, Sweden..
    Weidenhielm, L.
    Karolinska Inst, Dept Mol Med & Surg, Stockholm, Sweden..
    Improving Diagnostics of Femoroacetabular Impingement - A Feasibility Study2018In: Osteoarthritis and Cartilage, ISSN 1063-4584, E-ISSN 1522-9653, Vol. 26, p. S461-S462Article in journal (Other academic)
  • 6.
    Rakesh, Krishnan
    et al.
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL. KTH, School of Engineering Sciences (SCI), Centres, BioMEx.
    Björsell, N.
    Smith, Christian
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL. KTH, School of Engineering Sciences (SCI), Centres, BioMEx.
    Segmenting humeral submovements using invariant geometric signatures2017In: 2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 6951-6958, article id 8206619Conference paper (Refereed)
    Abstract [en]

    Discrete submovements are the building blocks of any complex movement. When robots collaborate with humans, extraction of such submovements can be very helpful in applications such as robot-assisted rehabilitation. Our work aims to segment these submovements based on the invariant geometric information embedded in segment kinematics. Moreover, this segmentation is achieved without any explicit kinematic representation. Our work demonstrates the usefulness of this invariant framework in segmenting a variety of humeral movements, which are performed at different speeds across different subjects. Our results indicate that this invariant framework has high computational reliability despite the inherent variability in human motion.

  • 7.
    Wang, Ruoli
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, BioMEx. Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden.
    Gäverth, J.
    Herman, Pawel
    KTH, School of Electrical Engineering and Computer Science (EECS), Computational Science and Technology (CST).
    Changes in the neural and non-neural related properties of the spastic wrist flexors after treatment with botulinum toxin a in post-stroke subjects: An optimization study2018In: Frontiers in Bioengineering and Biotechnology, E-ISSN 2296-4185, Vol. 9, no June, article id 73Article in journal (Refereed)
    Abstract [en]

    Quantifying neural and non-neural contributions to the joint resistance in spasticity is essential for a better evaluation of different intervention strategies such as botulinum toxin A (BoTN-A). However, direct measurement of muscle mechanical properties and spasticity-related parameters in humans is extremely challenging. The aim of this study was to use a previously developed musculoskeletal model and optimization scheme to evaluate the changes of neural and non-neural related properties of the spastic wrist flexors during passive wrist extension after BoTN-A injection. Data of joint angle and resistant torque were collected from 21 chronic stroke patients before, and 4 and 12 weeks post BoTN-A injection using NeuroFlexor, which is a motorized force measurement device to passively stretch wrist flexors. The model was optimized by tuning the passive and stretch-related parameters to fit the measured torque in each participant. It was found that stroke survivors exhibited decreased neural components at 4 weeks post BoNT-A injection, which returned to baseline levels after 12 weeks. The decreased neural component was mainly due to the increased motoneuron pool threshold, which is interpreted as a net excitatory and inhibitory inputs to the motoneuron pool. Though the linear stiffness and viscosity properties of wrist flexors were similar before and after treatment, increased exponential stiffness was observed over time which may indicate a decreased range of motion of the wrist joint. Using a combination of modeling and experimental measurement, valuable insights into the treatment responses, i.e., transmission of motoneurons, are provided by investigating potential parameter changes along the stretch reflex pathway in persons with chronic stroke.

  • 8.
    Wang, Ruoli
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics. KTH, School of Engineering Sciences (SCI), Centres, BioMEx. Karolinska Institutet, Sweden.
    Herman, Pawel
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Ekeberg, Örjan
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Gäverth, Johan
    Dept Women's and Children's Health, Karolinska Institutet.
    Fagergren, Anders
    AggeroMedTech AB, Stockholm.
    Forssberg, Hans
    Dept Women's and Children's Health, Karolinska Institutet.
    Neural and non-neural related properties in the spastic wrist flexors: An optimization study2017In: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 47, p. 198-209Article in journal (Refereed)
    Abstract [en]

    Quantifying neural and non-neural contributions to increased joint resistance in spasticity is essential for a better understanding of its pathophysiological mechanisms and evaluating different intervention strategies. However, direct measurement of spasticity-related manifestations, e.g., motoneuron and biophysical properties in humans, is extremely challenging. In this vein, we developed a forward neuromusculoskeletal model that accounts for dynamics of muscle spindles, motoneuron pools, muscle activation and musculotendon of wrist flexors and relies on the joint angle and resistant torque as the only input measurement variables. By modeling the stretch reflex pathway, neural and non-neural related properties of the spastic wrist flexors were estimated during the wrist extension test. Joint angle and resistant torque were collected from 17 persons with chronic stroke and healthy controls using NeuroFlexor, a motorized force measurement device during the passive wrist extension test. The model was optimized by tuning the passive and stretch reflex-related parameters to fit the measured torque in each participant. We found that persons with moderate and severe spasticity had significantly higher stiffness than controls. Among subgroups of stroke survivors, the increased neural component was mainly due to a lower muscle spindle rate at 50% of the motoneuron recruitment. The motoneuron pool threshold was highly correlated to the motoneuron pool gain in all subgroups. The model can describe the overall resistant behavior of the wrist joint during the test. Compared to controls, increased resistance was predominantly due to higher elasticity and neural components. We concluded that in combination with the NeuroFlexor measurement, the proposed neuromusculoskeletal model and optimization scheme served as suitable tools for investigating potential parameter changes along the stretch-reflex pathway in persons with spasticity.

  • 9.
    Yadav, Priti
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics. KTH, School of Engineering Sciences (SCI), Centres, BioMEx.
    Multiscale Modelling of Proximal Femur Growth: Importance of Geometry and Influence of Load2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Longitudinal growth of long bone occurs at growth plates by a process called endochondral ossification. Endochondral ossification is affected by both biological and mechanical factors. This thesis focuses on the mechanical modulation of femoral bone growth occurring at the proximal growth plate, using mechanobiological theories reported in the literature. Finite element analysis was used to simulate bone growth.

    The first study analyzed the effect of subject-specific growth plate geometry over simplified growth plate geometry in numerical prediction of bone growth tendency. Subject-specific femur finite element model was constructed from magnetic resonance images of one able- bodied child. Gait kinematics and kinetics were acquired from motion analysis and analyzed further in musculoskeletal modelling to determine muscle and joint contact forces. These were used to determine loading on the femur in finite element analysis. The growth rate was computed based on a mechanobiological theory proposed by Carter and Wong, and a growth model in the principal stress direction was introduced. Our findings support the use of subject- specific geometry and of the principal stress growth direction in prediction of bone growth.

    The second study aimed to illustrate how different muscle groups’ activation during gait affects proximal femoral growth tendency in able-bodied children. Subject-specific femur models were used. Gait kinematics and kinetics were acquired for 3 able-bodied children, and muscle and joint contact forces were determined, similar to the first study. The contribution of different muscle groups to hip contact force was also determined. Finite element analysis was performed to compute the specific growth rate and growth direction due to individual muscle groups. The simulated growth model indicated that gait loading tends to reduce neck shaft angle and femoral anteversion during growth. The muscle groups that contributes most and least to growth rate were hip abductors and hip adductors, respectively. All muscle groups’ activation tended to reduce the neck shaft and femoral anteversion angles, except hip extensors and adductors which showed a tendency to increase the femoral anteversion.

    The third study’s aim was to understand the influence of different physical activities on proximal femoral growth tendency. Hip contact force orientation was varied to represent reported forces from a number of physical activities. The findings of this study showed that all studied physical activities tend to reduce the neck shaft angle and anteversion, which corresponds to the femur’s natural course during normal growth.

    The aim of the fourth study was to study the hypothesis that loading in the absence of physical activity, i.e. static loading, can have an adverse effect on bone growth. A subject-specific model was used and growth plate was modeled as a poroelastic material in finite element analysis. Prendergast’s indicators for bone growth was used to analyse the bone growth behavior. The results showed that tendency of bone growth rate decreases over a long duration of static loading. The study also showed that static sitting is less detrimental than static standing for predicted cartilage-to-bone differentiation likelihood, due to the lower magnitude of hip contact force.

    The prediction of growth using finite element analysis on experimental gait data and person- specific femur geometry, based on mechanobiological theories of bone growth, offers a biomechanical foundation for better understanding and prediction of bone growth-related deformity problems in growing children. It can ultimately help in treatment planning or physical activity guidelines in children at risk at developing a femur or hip deformity. 

  • 10.
    Yadav, Priti
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, BioMEx.
    Shefelbine, Sandra J.
    Ponten, Eva
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, BioMEx. Department of Women’s and Children’s Health, Pediatric Orthopaedic Surgery Karolinska Institutet Stockholm Sweden.
    Influence of muscle groups' activation on proximal femoral growth tendency2017In: Biomechanics and Modeling in Mechanobiology, ISSN 1617-7959, E-ISSN 1617-7940, Vol. 16, no 6, p. 1869-1883Article in journal (Refereed)
    Abstract [en]

    Muscle and joint contact force influence stresses at the proximal growth plate of the femur and thus bone growth, affecting the neck shaft angle (NSA) and femoral anteversion (FA). This study aims to illustrate how different muscle groups' activation during gait affects NSA and FA development in able-bodied children. Subject-specific femur models were developed for three able-bodied children (ages 6, 7, and 11 years) using magnetic resonance images. Contributions of different muscle groups-hip flexors, hip extensors, hip adductors, hip abductors, and knee extensors-to overall hip contact force were computed. Specific growth rate for the growth plate was computed, and the growth was simulated in the principal stress direction at each element in the growth front. The predicted growth indicated decreased NSA and FA (of about over a four-month period) for able-bodied children. Hip abductors contributed the most, and hip adductors, the least, to growth rate. All muscles groups contributed to a decrease in predicted NSA (similar to 0.01 degrees-0.04 degrees and FA (similar to 0.004 degrees-0.2 degrees), except hip extensors and hip adductors, which showed a tendency to increase the FA (similar to 0.004 degrees-0.2 degrees). Understanding influences of different muscle groups on long bone growth tendency can help in treatment planning for growing children with affected gait.

  • 11.
    Zhou, Guang-Quan
    et al.
    Southeast Univ, Sch Biol Sci & Med Engn, Nanjing, Jiangsu, Peoples R China.;Southeast Univ, Natl Demonstrat Ctr Expt Biomed Engn Educ, Nanjing, Jiangsu, Peoples R China..
    Zhang, Yi
    Southeast Univ, Sch Biol Sci & Med Engn, Nanjing, Jiangsu, Peoples R China.;Southeast Univ, Natl Demonstrat Ctr Expt Biomed Engn Educ, Nanjing, Jiangsu, Peoples R China..
    Wang, Ruo-Li
    KTH, School of Engineering Sciences (SCI), Centres, BioMEx. KTH, School of Engineering Sciences (SCI), Mechanics. Karolinska Inst, Dept Womens & Childrens Hlth, Stockholm, Sweden..
    Zhou, Ping
    Southeast Univ, Sch Biol Sci & Med Engn, Nanjing, Jiangsu, Peoples R China.;Southeast Univ, Natl Demonstrat Ctr Expt Biomed Engn Educ, Nanjing, Jiangsu, Peoples R China..
    Zheng, Yong-Ping
    Hong Kong Polytech Univ, Dept Biomed Engn, Hong Kong, Hong Kong, Peoples R China..
    Tarassova, Olga
    Swedish Sch Sport & Hlth Sci, Stockholm, Sweden..
    Arndt, Anton
    Swedish Sch Sport & Hlth Sci, Stockholm, Sweden.;Karolinska Inst, Dept Clin Intervent & Technol, Stockholm, Sweden..
    Chen, Qiang
    Southeast Univ, Sch Biol Sci & Med Engn, Nanjing, Jiangsu, Peoples R China.;Southeast Univ, Natl Demonstrat Ctr Expt Biomed Engn Educ, Nanjing, Jiangsu, Peoples R China..
    Automatic Myotendinous Junction Tracking in Ultrasound Images with Phase-Based Segmentation2018In: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141, article id 3697835Article in journal (Refereed)
    Abstract [en]

    Displacement of the myotendinous junction (MTJ) obtained by ultrasound imaging is crucial to quantify the interactive length changes of muscles and tendons for understanding the mechanics and pathological conditions of the muscle-tendon unit during motion. However, the lack of a reliable automatic measurement method restricts its application in human motion analysis. This paper presents an automated measurement of MTJ displacement using prior knowledge on tendinous tissues and MTJ, precluding the influence of nontendinous components on the estimation of MTJ displacement. It is based on the perception of tendinous features from musculoskeletal ultrasound images using Radon transform and thresholding methods, with information about the symmetric measures obtained from phase congruency. The displacement of MTJ is achieved by tracking manually marked points on tendinous tissues with the Lucas-Kanade optical flow algorithm applied over the segmented MTJ region. The performance of this method was evaluated on ultrasound images of the gastrocnemius obtained from 10 healthy subjects (26.0 +/- 2.9 years of age). Waveform similarity between the manual and automatic measurements was assessed by calculating the overall similarity with the coefficient ofmultiple correlation (CMC). In vivo experiments demonstrated that MTJ tracking with the proposedmethod (CMC = 0.97 +/- 0.02) was more consistent with the manual measurements than existing optical flow tracking methods (CMC = 0.79 +/- 0.11). This study demonstrated that the proposed method was robust to the interference of nontendinous components, resulting in a more reliable measurement of MTJ displacement, whichmay facilitate further research and applications related to the architectural change of muscles and tendons.

1 - 11 of 11
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