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- J Biomech 42(16):IFC (2009)
- Fluid–structure interaction analysis of turbulent pulsatile flow within a layered aortic wall as related to aortic dissection
Khanafer K Berguer R - J Biomech 42(16):2642-2648 (2009)
Turbulent pulsatile flow and wall mechanics were studied numerically in an axisymmetric three-layered wall model of a descending aorta. The transport equations were solved using the finite element formulation based on the Galerkin method of weighted residuals. A fully-coupled fluid–structure interaction (FSI) analysis was utilized in this investigation. We calculated Von Mises wall stress, streamlines and fluid pressure contours. The findings of this study show that peak wall stress and maximum shear stress are highest in the media layer. The difference in the elastic properties of contiguous layers of the wall of the aorta probably determines the occurrence of dissection in the media layer. Moreover, the presence of aortic intramural hematoma is found to have a significant effect on the peak wall stress acting on the inner layer. - Computation of the 3D kinematics in a global frame over a 40 m-long pathway using a rolling motion analysis system
Begon M Colloud F Fohanno V Bahuaud P Monnet T - J Biomech 42(16):2649-2653 (2009)
A rolling motion analysis system has been purpose-built to acquire an accurate three-dimensional kinematics of human motion with large displacement. Using this device, the kinematics is collected in a local frame associated with the rolling motion analysis system. The purpose of this paper is to express the local kinematics of a subject walking on a 40 m-long pathway in a global system of co-ordinates. One participant performed five trials of walking while he was followed by a rolling eight camera optoelectronic motion analysis system. The kinematics of the trials were reconstructed in the global frame using two different algorithms and 82 markers placed on the floor organized in two parallel and horizontal lines. The maximal error ranged from 0.033 to 0.187 m (<0.5% of the volume diagonal). As a result, this device is accurate enough for acquiring the kinematics of cyclic activities with large displacements in ecological environment. - Determining effective subject-specific strength levels for forward dives using computer simulations of recorded performances
King MA Kong PW Yeadon MR - J Biomech 42(16):2672-2677 (2009)
This study used optimisation procedures in conjunction with an 8-segment torque-driven computer simulation model of the takeoff phase in springboard diving to determine appropriate subject-specific strength parameters for use in the simulation of forward dives. Kinematic data were obtained using high-speed video recordings of performances of a forward dive pike (101B) and a forward somersault pike dive (105B) by an elite diver. Nine parameters for each torque generator were taken from dynamometer measurements on an elite gymnast. The isometric torque parameter for each torque generator was then varied together with torque activation timings until the root mean squared (RMS) percentage difference between simulation and performance in terms of joint angles, orientation, linear momentum, angular momentum, and duration of springboard contact was minimised for each of the two dives. The two sets of isometric torque parameters were combined into a single set by choosing the! larger value from the two sets for each parameter. Simulations using the combined set of isometric torque parameters matched the two performances closely with RMS percentage differences of 2.6% for 101B and 3.7% for 105B. Maximising the height reached by the mass centre during the flight phase for 101B using the combined set of isometric parameters and by varying torque generator activation timings during takeoff resulted in a credible height increase of 38 mm compared to the matching simulation. It is concluded that the procedure is able to determine appropriate effective strength levels suitable for use in the optimisation of simulated forward rotating dive performances. - Inertial sensor-based knee flexion/extension angle estimation
Cooper G Sheret I McMillian L Siliverdis K Sha N Hodgins D Kenney L Howard D - J Biomech 42(16):2678-2685 (2009)
A new method for estimating knee joint flexion/extension angles from segment acceleration and angular velocity data is described. The approach uses a combination of Kalman filters and biomechanical constraints based on anatomical knowledge. In contrast to many recently published methods, the proposed approach does not make use of the earth's magnetic field and hence is insensitive to the complex field distortions commonly found in modern buildings. The method was validated experimentally by calculating knee angle from measurements taken from two IMUs placed on adjacent body segments. In contrast to many previous studies which have validated their approach during relatively slow activities or over short durations, the performance of the algorithm was evaluated during both walking and running over 5 minute periods. Seven healthy subjects were tested at various speeds from 1 to 5 mile/h. Errors were estimated by comparing the results against data obtained simultaneously f! rom a 10 camera motion tracking system (Qualysis). The average measurement error ranged from 0.7 degrees for slow walking (1 mph) to 3.4 degrees for running (5 mph). The joint constraint used in the IMU analysis was derived from the Qualysis data. Limitations of the method, its clinical application and its possible extension are discussed. - Regional stiffening of the mitral valve anterior leaflet in the beating ovine heart
Krishnamurthy G Itoh A Swanson JC Bothe W Karlsson M Kuhl E Craig Miller D Ingels NB - J Biomech 42(16):2697-2701 (2009)
Left atrial muscle extends into the proximal third of the mitral valve (MV) anterior leaflet and transient tensing of this muscle has been proposed as a mechanism aiding valve closure. If such tensing occurs, regional stiffness in the proximal anterior mitral leaflet will be greater during isovolumic contraction (IVC) than isovolumic relaxation (IVR) and this regional stiffness difference will be selectively abolished by β-receptor blockade. We tested this hypothesis in the beating ovine heart. Radiopaque markers were sewn around the MV annulus and on the anterior MV leaflet in 10 sheep hearts. Four-dimensional marker coordinates were obtained from biplane videofluoroscopy before (CRTL) and after administration of esmolol (ESML). Heterogeneous finite element models of each anterior leaflet were developed using marker coordinates over matched pressures during IVC and IVR for CRTL and ESML. Leaflet displacements were simulated using measured left ventricular and atrial ! pressures and a response function was computed as the difference between simulated and measured displacements. Circumferential and radial elastic moduli for ANNULAR, BELLY and EDGE leaflet regions were iteratively varied until the response function reached a minimum. The stiffness values at this minimum were interpreted as the in vivo regional material properties of the anterior leaflet. For all regions and all CTRL beats IVC stiffness was 40–58% greater than IVR stiffness. ESML reduced ANNULAR IVC stiffness to ANNULAR IVR stiffness values. These results strongly implicate transient tensing of leaflet atrial muscle during IVC as the basis of the ANNULAR IVC–IVR stiffness difference. - Biomechanical characteristics of the eccentric Achilles tendon exercise
Henriksen M Aaboe J Bliddal H Langberg H - J Biomech 42(16):2702-2707 (2009)
Background Eccentric exercise has been shown to provide good short-term clinical results in the treatment of painful mid-portion chronic Achilles tendinopathies. However, the mechanisms behind the positive effects of eccentric rehabilitation regimes are not known, and research into the biomechanics of the exercise may improve our understanding. Methods Sixteen healthy subjects performed one-legged full weight bearing ankle plantar and dorsiflexion exercises during which three-dimensional ground reaction forces (GRF), ankle joint kinematics and surface electromyography (EMG) of the lower leg muscles were recorded. Joint kinematics, GRF frequency contents, average EMG amplitudes, and Achilles tendon loads were calculated. Findings The eccentric movement phase was characterized by a higher GRF frequency content in the 8–12 Hz range, and reduced EMG activity in the lower leg muscles. No differences in Achilles tendon loads were found. Interpretation This descriptive study demonstrates differences in the movement biomechanics between the eccentric and concentric phases of one-legged full weight bearing ankle dorsal and plantar flexion exercises. In particular, the findings imply that although the tendon loads are similar, the tendon is vibrated at higher frequencies during the eccentric phase than during the concentric phases. This study provides data that may explain the mechanisms behind the effectiveness of eccentric exercises used in the treatment of Achilles tendinopathies. - Synergistic action of static stretching and BMP-2 stimulation in the osteoblast differentiation of C2C12 myoblasts
Kim IS Song YM Cho TH Kim JY Weber FE Hwang SJ - J Biomech 42(16):2721-2727 (2009)
Static stretching is a major type of mechanical stimuli utilized during distraction osteogenesis (DO), a general surgical method for the lengthening of bone. The molecular signals that drive the regenerative process in DO include a variety of cytokines. Among these, bone morphogenic protein (BMP, -2 and -4) has been reported to exhibit strongly enhanced expression following the application of mechanical strain during the distraction phase. We hypothesize that mechanical stretching enhances osteoblast differentiation in DO by means of interaction with BMP-2 induced cytokine stimulation. C2C12 pluripotential myoblasts were exposed to stretching load and the resulting cell proliferation and osteoblast differentiation were then examined. The application of static stretching force resulted in significant cell proliferation at day 3, although with variable intensity according to the magnitude of stretching. A combined treatment of stretching load with BMP-2 stimulation signi! ficantly increased alkaline phosphatase (ALP) activity and up-regulated the gene expression of osteogenic markers (ALP, type I collagen, osteopontin, osteocalcin, cbfa1, osterix and dlx5). Results obtained with the combined treatment yielded more activity than just the BMP-2 treatment or stretching alone. These results reveal that specific levels of static stretching force increase cell proliferation and effectively stimulate the osteoblast differentiation of C2C12 cells in conjunction with BMP-2 stimulation, thus indicating a synergistic interaction between mechanical strain and cytokine signaling. - Post-yield relaxation behavior of bovine cancellous bone
Burgers TA Lakes RS García-Rodríguez S Piller GR Ploeg HL - J Biomech 42(16):2728-2733 (2009)
Relaxation studies were conducted on specimens of bovine cancellous bone at post-yield strains. Stress and strain were measured for 1000 s and the relaxation modulus was determined. Fifteen cylindrical, cancellous bone specimens were removed from one bovine femur in the anterior–posterior direction. The relaxation modulus was found to be a function of strain. Therefore cancellous bone is non-linearly viscoelastic/viscoplastic in the plastic region. A power law regression was fit to the relaxation modulus data. The multiplicative constant was found to be statistically related through a power law relationship to both strain (p<0.0005) and apparent density (p<0.0005) while the power coefficient was found to be related through a power law relationship, E(t, ε)=A(ε)t−n(ε), to strain (p<0.0005), but not apparent density. - Novel approach to ambulatory assessment of human segmental orientation on a wearable sensor system
Liu K Liu T Shibata K Inoue Y Zheng R - J Biomech 42(16):2747-2752 (2009)
A new method using a double-sensor difference based algorithm for analyzing human segment rotational angles in two directions for segmental orientation analysis in the three-dimensional (3D) space was presented. A wearable sensor system based only on triaxial accelerometers was developed to obtain the pitch and yaw angles of thigh segment with an accelerometer approximating translational acceleration of the hip joint and two accelerometers measuring the actual accelerations on the thigh. To evaluate the method, the system was first tested on a 2° of freedom mechanical arm assembled out of rigid segments and encoders. Then, to estimate the human segmental orientation, the wearable sensor system was tested on the thighs of eight volunteer subjects, who walked in a straight forward line in the work space of an optical motion analysis system at three self-selected speeds: slow, normal and fast. In the experiment, the subject was assumed to walk in a straight forward way w! ith very little trunk sway, skin artifacts and no significant internal/external rotation of the leg. The root mean square (RMS) errors of the thigh segment orientation measurement were between 2.4° and 4.9° during normal gait that had a 45° flexion/extension range of motion. Measurement error was observed to increase with increasing walking speed probably because of the result of increased trunk sway, axial rotation and skin artifacts. The results show that, without integration and switching between different sensors, using only one kind of sensor, the wearable sensor system is suitable for ambulatory analysis of normal gait orientation of thigh and shank in two directions of the segment-fixed local coordinate system in 3D space. It can then be applied to assess spatio-temporal gait parameters and monitoring the gait function of patients in clinical settings. - Influence of coronary collateral flow on coronary diagnostic parameters: An in vitro study
Peelukhana SV Back LH Banerjee RK - J Biomech 42(16):2753-2759 (2009)
Functional severity of coronary stenosis is often assessed using diagnostic parameters. These parameters are evaluated from the combined pressure and/or flow measurements taken at the site of the stenosis. However, when there are functional collaterals operating downstream to the stenosis, the coronary flow-rate increases, and the pressure in the stenosed artery is altered. This effect of downstream collaterals on different diagnostic parameters is studied using a physiological representative in vitro coronary flow-loop. The three diagnostic parameters tested are fractional flow reserve (FFR), lesion flow coefficient (LFC), and pressure drop coefficient (CDP). The latter two were discussed in recent publications by our group ([Banerjee et al., 2008] and [Banerjee et al., 2007], 2009). They are evaluated for three different severities of stenosis and tested for possible misinterpretation in the presence of variable collateral flows. Pressure and flow are measured with and without downstream collaterals. The diagnostic parameters are then calculated from these readings. In the case of intermediate stenosis (80% area blockage), FFR and LFC increased from 0.74 to 0.77 and 0.58 to 0.62, respectively, for no collateral to fully developed collateral flow. Also, CDP decreased from 47 to 42 for no collateral to fully developed collateral flow. These changes in diagnostic parameters might lead to erroneous postponement of coronary intervention. Thus, variability in diagnostic parameters for the same stenosis might lead to misinterpretation of stenosis severity in the presence of operating downstream collaterals. - Ryanodine receptor 1 mediates Ca2+ transport and influences the biomechanical properties in RBCs
Wang X Chen X Tang Z Yao W Liu X Wei R Wang X Ka W Sun D He D Wen Z Chien S - J Biomech 42(16):2774-2779 (2009)
Ryanodine receptors (RyRs) are a family of Ca2+ channel proteins that mediate the massive release of Ca2+ from the endoplasmic reticulum into the cytoplasma. In the present study, we manipulated the incorporation of RyR1 into RBC membrane and investigated its influences on the intracellular Ca2+ ([Ca2+]in) level and the biomechanical properties in RBCs. The incorporation of RyR1 into RBC membranes was demonstrated by both immunofluorescent staining and the change of [Ca2+]in of RBCs. In the presence of RyR1, [Ca2+]in showed biphasic changes, i.e., it increased with the extracellular Ca2+ ([Ca2+]ex) up to 5 μM and then decreased with the further increase of [Ca2+]ex. However, [Ca2+]in remained constant in the absence of the RyR1. The results of biomechanical measurements on RBCs, including deformability, osmotic fragility, and membrane microviscosity, reflected similar biphasic changes of [Ca2+]in mediated by RyR1 with the increases of [Ca2+]ex. Therefore, it is believ! ed that RyR1 can incorporate into RBC membrane in vitro, and mediate Ca2+ influx, and then regulate RBC biomechanical properties. This information suggests that RBCs may serve as a model to study the function of RyR1 as a Ca2+ release channel. - Statistical factorial analysis on the poroelastic material properties sensitivity of the lumbar intervertebral disc under compression, flexion and axial rotation
Malandrino A Planell JA Lacroix D - J Biomech 42(16):2780-2788 (2009)
A statistical factorial analysis approach was conducted on a poroelastic finite element model of a lumbar intervertebral disc to analyse the influence of six material parameters (permeabilities of annulus, nucleus, trabecular vertebral bone, cartilage endplate and Young's moduli of annulus and nucleus) on the displacement, fluid pore pressure and velocity fields. Three different loading modes were investigated: compression, flexion and axial rotation. Parameters were varied considering low and high levels in agreement with values found in the literature for both healthy and degenerated lumbar discs. Results indicated that annulus stiffness and cartilage endplate permeability have a strong effect on the overall fluid- and solid-phase responses in all loading conditions studied. Nucleus stiffness showed its main relevance in compression while annulus permeability influenced mainly the annular pressure field. This study confirms the permeability's central role in biphasic! modelling and highlights for the lumbar disc which experiments of material property characterization should be performed. Moreover, such sensitivity study gives important guidelines in poroelastic material modelling and finite element disc validation. - Differences in patellofemoral contact mechanics associated with patellofemoral pain syndrome
Connolly KD Ronsky JL Westover LM Küpper JC Frayne R - J Biomech 42(16):2802-2807 (2009)
Patellofemoral pain syndrome (PFPS) is a disorder of the patellofemoral (PF) joint in which abnormal tracking is often cited as a factor in pain development. PF tracking is partially dependent on passive stabilizers (ex: PF geometry). Relations amongst PFPS, PF tracking, and contact mechanics are poorly understood. In-vivo investigation of passive PF joint stabilizers including PF tracking, contact mechanics, cartilage thickness, and patellar shape will allow structural characterization of the PF joint and may highlight differences associated with PFPS. This study examined the role that passive stabilizers play in PFPS (n=10) versus healthy subjects (n=10). PF tracking (contact area centroid migration), cartilage thickness, shape, congruence, and contact patterns were quantified using magnetic resonance imaging during isometric loading at 15°, 30°, and 45° of knee flexion. Distinct relationships were identified between patellar shape and tracking and contact, partic! ularly at low flexion (15–30°). Healthy subjects exhibited distinct PF tracking and contact patterns related to Type I patella shape (80%) with increasing total contact area (p<0.001) and proximal centroid migration (15–30° p=0.012; 30–45° p<0.001) for increasing knee angles. PFPS subjects deviated from these patterns at low flexion, demonstrating higher total contact area than healthy subjects (p=0.046 at 15°), lack of proximal centroid migration (15–30°), and more Type II (30%) and III (20%) patella shapes. This study highlights a new finding that patellar shape combined with low degrees of flexion (15–30°) may be important to consider, as this is where PFPS tracking and contact patterns deviate from healthy. - Sarcomere dynamics in skeletal muscle myofibrils during isometric contractions
Pavlov I Novinger R Rassier DE - J Biomech 42(16):2808-2812 (2009)
The main goal of this study was to evaluate the dynamics of sarcomeres during isometric activation of skeletal muscle myofibrils. Rabbit psoas myofibrils (n=14) were attached between a pair of cantilevers for force measurements at one side and a rigid glass needle at the other side, and their images were used for measurements of individual sarcomere lengths (SL) during contractions. Myofibrils were set at average SL between 2.13 and 3.06 μm, and were activated and held isometric for 20–35 s during which SL and force were continuously measured. SL dispersion increased from the rest state to activation, but it remained mostly constant during the activation period. Even with the length non-uniformity developed during myofibril activation, most sarcomeres stabilized their length changes during the isometric contraction. As a result, sarcomeres contracted at different degrees of filament overlap while producing similar forces. When the myofibrils were separated in two gr! oups that produced force at averaged short (≤2.5 μm) or long (≥2.5 μm) SL, the initial non-uniformity was greater in long lengths, but changes observed in sarcomeres during the activation period were similar, suggesting that sarcomere stability is not length-dependent. - Novel approach for a precise determination of short-time intervals in ankle sprain experiments
Schmitt S Melnyk M Alt W Gollhofer A - J Biomech 42(16):2823-2825 (2009)
The etiology of ankle sprain injury is still under debate. Therefore, diagnoses of ankle inversion experiments play an important role. Recent studies stress the importance of exact time measurements due to the short inversion period of around 70 ms. This paper presents a novel approach using the vertical ground reaction force (vGRF) to determine the short-time intervals in ankle sprain experiments, which are present in the form of short periods from the beginning of the movement to its end and short latencies to following signals, e.g. EMG onset of peroneal muscles. We compare our method to electrogoniometry at the ankle which is considered as the gold standard. During the inversion movement the kinematic action at the ankle can be measured with electrogoniometry, whereas the vGRF quantifies the vertical dynamic reaction of the tested subject entirely. We observe a difference of between the first observable vGRF response and the first observable electrogoniometer resp! onse following platform release. The end of the ankle inversion measured with electrogoniometry is later than the maximal vGRF peak. The potential supplementary (mechanical) information of this novel approach compared to electrogoniometry and its ease of use, may be not only interesting for researchers when studying ankle sprain simulations but also for clinicians when testing functional ankle stability. - Specifications for machining the bovine cortical bone in relation to its microstructure
Sugita N Mitsuishi M - J Biomech 42(16):2826-2829 (2009)
Until date, many devices have been developed for cutting human bones during orthopedic surgeries. However, bones are anisotropic material, and their machining characteristics depend on the tool feed direction. In this study, microcutting of the bovine cortical bone is performed and its structure observed under a microscope. Furthermore, the formation of cutting chips and measurement of the cutting force during bone machining are dynamically observed while considering the anisotropy of bone tissue. In particular, the fracture of secondary osteons and crack propagation in bones are observed and analyzed. The results indicate that when the cut depth exceeds 20 μm and is greater than the interval of concentric lamellae, cracks are formed together with chips. A new method for bone machining is proposed. This method is based on the characteristics of crack propagation in bones and is expected to produce low mechanical stress and realize highly efficient and precise machinin! g of living tissues such as bones.
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