MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'Journal of Biomechanics' source. Sat, 20 Mar 2010 16:02:51 +0100 http://www.medworm.com/index.php?rid=3341875&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929010001156%2Fabstract%3Frss%3Dyes (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341875 Mon, 08 Mar 2010 17:32:55 +0100 3341875 http://www.medworm.com/index.php?rid=3272465&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929010000205%2Fabstract%3Frss%3Dyes (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272465 Mon, 15 Feb 2010 15:56:26 +0100 3272465 http://www.medworm.com/index.php?rid=3272487&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009004291%2Fabstract%3Frss%3Dyes Abstract: Joint distraction and mobilization with a hinged external fixator preserves elbow stability and mobility. However, the alignment of both elbow and fixator hinges was the initial prerequisite of the arthrodiatasis technique. The main goal of this study was to numerically evaluate the kinematic influence of the device, surgery, and joint factors on hinge alignment. The kinetic effects of the pins placement and elbow angle on concentric distraction and mobilization were also discussed. A unilaterally hinged elbow-fixator system with a 14 links and 10 degrees-of-freedom was instrumented into a humeroulnar model. The Denavit–Hartenberg method with the homogeneous transformation matrixes was applied to perform kinematic analysis of the linkage system. The predicted results revealed t... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272487 Thu, 28 Jan 2010 00:00:00 +0100 3272487 http://www.medworm.com/index.php?rid=3204364&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929010000035%2Fabstract%3Frss%3Dyes (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204364 Mon, 25 Jan 2010 17:22:36 +0100 3204364 http://www.medworm.com/index.php?rid=3272500&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009007325%2Fabstract%3Frss%3Dyes The Publishers regret that an error occurred in of the above published paper. Moment arm coefficients on for the BIC (Primary Joint—EFE) A6 and A7; A9 and A10; and A11 and A12 were inadvertently interchanged. The published coefficients listed as A6 should be A7 and vice versa; A9 should be A10 and vice versa, and A11 should be A12 and vice versa. The correct version of is reproduced here. The Publishers would like to apologise for any inconvenience this error may have caused. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272500 Mon, 25 Jan 2010 00:00:00 +0100 3272500 http://www.medworm.com/index.php?rid=3272499&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009007313%2Fabstract%3Frss%3Dyes The authors regret that there was an error in the reference details listed for in their above published paper. The correct reference details appear below. The authors would like to apologize for any inconvenience this error may have caused. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272499 Wed, 20 Jan 2010 00:00:00 +0100 3272499 http://www.medworm.com/index.php?rid=3272468&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006265%2Fabstract%3Frss%3Dyes Abstract: A study was performed to evaluate a computational model used to characterize the influence of vastus medialis obliquus (VMO) function on the patellofemoral pressure distribution. Ten knees were tested in vitro at 40°, 60° and 80° of knee flexion with quadriceps loads applied to represent a normal VMO, and with the VMO force decreased by approximately 50% to represent a weak VMO. The tests were performed with the cartilage intact and with a full thickness cartilage lesion centered on the lateral facet of the patella. The experimental tests were replicated computationally by applying discrete element analysis to a model of each knee constructed from MRI images. Repeated measures statistical comparisons were used to compare computational to experimental data and identify signific... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272468 Mon, 11 Jan 2010 00:00:00 +0100 3272468 http://www.medworm.com/index.php?rid=3204400&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS002192900900712X%2Fabstract%3Frss%3Dyes The publishers regret that the name of the co-author Louise McMillan was spelt incorrectly as Louise McMillian in the above published paper. The publishers would like to apologize for any inconvenience this error may have caused. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204400 Mon, 11 Jan 2010 00:00:00 +0100 3204400 http://www.medworm.com/index.php?rid=3341898&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006320%2Fabstract%3Frss%3Dyes Conclusions: The study results confirm a direct correlation between sagittal offset of the CoP and the magnitude of joint torques throughout the lower extremity. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341898 Mon, 04 Jan 2010 00:00:00 +0100 3341898 http://www.medworm.com/index.php?rid=3341885&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006484%2Fabstract%3Frss%3Dyes Abstract: Barbed surgical sutures are a new type of knotless suture that are currently being used clinically in cosmetic and plastic surgery procedures for faster healing and better cosmesis. Clinical studies are also underway to evaluate their performance in other deep tissue applications. However, little is known about their intrinsic mechanical behavior and their interactions with surrounding tissues. The primary objective of the current study was to analyze the mechanical behavior of barbed sutures using a finite element analysis approach. First, the effect of applying a point-pressure load to the tip of the barb and measuring its effect on barb displacement was studied. Second, the effect of an applied displacement to a barb anchored either in skin or tendon material for both the sutu... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341885 Mon, 04 Jan 2010 00:00:00 +0100 3341885 http://www.medworm.com/index.php?rid=3341884&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006496%2Fabstract%3Frss%3Dyes This study presents a new method of assessment of three-dimensional (3D) socket–stump kinematics/slippage of strenuous activities using Biplane Dynamic Roentgen Stereogrammetric Analysis instrumentation. Ten below knee amputees participated in the study. A more holistic representation of the downward slippage trend of all proximal side skin markers with respect to the socket, and an even more characteristic and of higher magnitude downward-and anterioposterior slippage (maximum slippage: 151mm for the fast-stop task and 19mm for the step-down task) between the distal markers after impact, was possible for both tasks for all amputees. Displacement between skin-to-skin marker pairs reached maximum values of approximately 10mm for the step-down trials and up to 24mm for the fast stop trials... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341884 Mon, 04 Jan 2010 00:00:00 +0100 3341884 http://www.medworm.com/index.php?rid=3341883&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006472%2Fabstract%3Frss%3Dyes Abstract: The accumulation of a fluid property from the standpoint of a particle moving with non-steady fluid flow (i.e., platelet/blood-cell damage index in pulsating blood flow) is a challenged computational problem due to the current need for particle-tracing methods. The method we developed (dubbed VPI) enables the approximation of the Lagrangian integral in real-time for any point in space and time for the entire domain and which is easily integrated into the the lattice Boltzmann method. As an illustrative numerical example we applied our method to a blood coagulation model which was shown to accurately capture the coagulation characteristics observed in experiments, and therefore opening a door for more detailed study of systems which are currently hard to study using particle traci... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341883 Thu, 31 Dec 2009 00:00:00 +0100 3341883 http://www.medworm.com/index.php?rid=3120105&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009007039%2Fabstract%3Frss%3Dyes (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120105 Fri, 25 Dec 2009 15:43:32 +0100 3120105 http://www.medworm.com/index.php?rid=3114435&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006897%2Fabstract%3Frss%3Dyes (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3114435 Wed, 23 Dec 2009 15:50:58 +0100 3114435 http://www.medworm.com/index.php?rid=3341878&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS002192900900668X%2Fabstract%3Frss%3Dyes This study aimed at improving the understanding of the biomechanics of lower limb bones by: (i) measuring the stiffness and strain distributions of the different low limb bones; (ii) assessing the effect of viscoelasticity in whole bones within a physiological range of strain-rates; (iii) assessing the difference in the behaviour in relation to opposite directions of bending and torsion. The structural stiffness and strain distribution of paired femurs, tibias and fibulas from two donors were measured. Each region investigated of each bone was instrumented with 8–16 triaxial strain gauges (over 600 grids in total). Each bone was subjected to 6–12 different loading configurations. Tests were replicated at two different loading speeds covering the physiological range of strain-rates. Vis... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341878 Wed, 23 Dec 2009 00:00:00 +0100 3341878 http://www.medworm.com/index.php?rid=3204399&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006812%2Fabstract%3Frss%3Dyes The Publishers regret that an error occurred in the above published paper. In Appendix A, Supporting information section on p. 2526, the sentence ‘The online version of this article contains additional supplementary data. Please visit doi:10.1016/j.atmosenv.2005.03.036’ should be replaced by ‘The online version of this article contains additional supplementary data. Please visit 10.1016/j.jbiomech.2009.07.008’. The Publishers would like to apologise for any inconvenience this error may have caused. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204399 Wed, 23 Dec 2009 00:00:00 +0100 3204399 http://www.medworm.com/index.php?rid=3204398&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006800%2Fabstract%3Frss%3Dyes The authors regret that the name of the co-author Jess G. Snedeker was spelt incorrectly as Jess G. Snedecker in their above published paper. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204398 Mon, 21 Dec 2009 00:00:00 +0100 3204398 http://www.medworm.com/index.php?rid=3341889&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006411%2Fabstract%3Frss%3Dyes Abstract: Various methods have been used to quantify the kinematic variability or stability of the human spine. However, each of these methods evaluates dynamic behavior within the stable region of state space. In contrast, our goal was to determine the extent of the stable region. A 2D mathematical model was developed for a human sitting on an unstable seat apparatus (i.e., the “wobble chair”). Forward dynamic simulations were used to compute trajectories based on the initial state. From these trajectories, a scalar field of trajectory divergence was calculated, specifically a finite time Lyapunov exponent (FTLE) field. Theoretically, ridges of local maxima within this field are expected to partition the state space into regions of qualitatively different behavior. We found that ridge... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341889 Thu, 17 Dec 2009 00:00:00 +0100 3341889 http://www.medworm.com/index.php?rid=3341877&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006691%2Fabstract%3Frss%3Dyes Abstract: Wearable hip protectors represent a promising strategy for reducing risk for hip fracture from a sideways fall. However, small changes in pad positioning may influence their protective benefit. Using a mechanical hip impact simulator, we investigated how three marketed soft shell hip protectors attenuate and redistribute the impact force applied to the hip, and how this depends on displacement from their intended position by 2.5 or 5cm superiorly, posteriorly, inferiorly or anteriorly. For centrally-placed protectors, peak pressure was reduced 93% below the unpadded value by a 16mm horseshoe-shaped protector, 93% by a 14mm horseshoe protector, and 94% by a 16mm continuous protector. In unpadded trials, 83% of the total force was applied to the skin overlying the proximal femur (d... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341877 Thu, 17 Dec 2009 00:00:00 +0100 3341877 http://www.medworm.com/index.php?rid=3341887&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006447%2Fabstract%3Frss%3Dyes Abstract: Inadequate peak knee extension during the swing phase of gait is a major deficit in individuals with spastic cerebral palsy (CP). The biomechanical mechanisms responsible for knee extension have not been thoroughly examined in CP. The purpose of this study was to assess the contributions of joint moments and gravity to knee extension acceleration during swing in children with spastic hemiplegic CP. Six children with spastic hemiplegic CP were recruited (age=13.4±4.8 years). Gait data were collected using an eight-camera system. Induced acceleration analysis was performed for each limb during swing. Average joint moment and gravity contributions to swing knee extension acceleration were calculated. Total swing and stance joint moment contributions were compared between the hemipl... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341887 Wed, 16 Dec 2009 00:00:00 +0100 3341887 http://www.medworm.com/index.php?rid=3341882&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006526%2Fabstract%3Frss%3Dyes Conclusion: Based on our ex vivo findings of increased cartilage strain after labral resection when compared to labral repair, we have demonstrated the associated consequences to the mechanical environment of the cartilage following surgical treatment of the labrum. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341882 Wed, 16 Dec 2009 00:00:00 +0100 3341882 http://www.medworm.com/index.php?rid=3341904&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006459%2Fabstract%3Frss%3Dyes This study highlights a new experimental method developed to measure full-field deformation of human skin in vivo. The technique uses a small-scale Qualisys (Sweden) 3D motion capture system and an array of reflective markers placed on the forearm of five healthy volunteers. A load of up to 1.5N was applied to induce skin deformation by pulling a fine wire attached to the centre of the marker configuration. Loading and marker displacements were recorded simultaneously. 3D marker trajectory data was generated for three different load directions. Tests were repeated to investigate accuracy and repeatability. Calibration results indicate the accuracy of the motion capture system with an average residual of 0.05mm. The procedure was found to be repeatable and accurate for five repeated tests o... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341904 Mon, 14 Dec 2009 00:00:00 +0100 3341904 http://www.medworm.com/index.php?rid=3341902&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006502%2Fabstract%3Frss%3Dyes Abstract: A new technique is presented that utilizes relative velocity vectors between articulating surfaces to characterize internal/external rotation of the tibio-femoral joint during dynamic loading. Precise tibio-femoral motion was determined by tracking the movement of implanted tantalum beads in high-speed biplane X-rays. Three-dimensional, subject-specific CT reconstructions of the femur and tibia, consisting of triangular mesh elements, were positioned in each analyzed frame. The minimum distance between subchondral bone surfaces was recorded for each mesh element comprising each bone surface, and the relative velocity between these opposing closest surface elements was determined in each frame. Internal/external rotation was visualized by superimposing tangential relative velocity... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341902 Mon, 14 Dec 2009 00:00:00 +0100 3341902 http://www.medworm.com/index.php?rid=3341891&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006393%2Fabstract%3Frss%3Dyes Abstract: Articular cartilage has a poor intrinsic capacity for self-repair. The advent of autologous chondrocyte implantation has provided a feasible method to treat cartilage defects. However, the associated drawbacks with the isolation and expansion of chondrocytes from autologous tissue has prompted research into alternative cell sources such as mesenchymal stem cells (MSCs) which have been found to exist in the bone marrow as well as other joint tissues such as the infrapatellar fat pad (IFP), synovium and within the synovial fluid itself. In this work we assessed the chondrogenic potential of IFP-derived porcine cells over a 6 week period in agarose hydrogel culture in terms of mechanical properties, biochemical content and histology. It was found that IFP cells underwent robust chon... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341891 Mon, 14 Dec 2009 00:00:00 +0100 3341891 http://www.medworm.com/index.php?rid=3341888&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006435%2Fabstract%3Frss%3Dyes Abstract: Interstitial flow is an important regulator of various cell behaviors both in vitro and in vivo, yet the forces that fluid flow imposes on cells embedded in a 3D extracellular matrix (ECM), and the effects of matrix architecture on those forces, are not well understood. Here, we demonstrate how fiber alignment can affect the shear and pressure forces on the cell and ECM. Using computational fluid dynamics simulations, we show that while the solutions of the Brinkman equation accurately estimate the average fluid shear stress and the drag forces on a cell within a 3D fibrous medium, the distribution of shear stress on the cellular surface as well as the peak shear stresses remain intimately related to the pericellular fiber architecture and cannot be estimated using bulk-averaged ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341888 Mon, 14 Dec 2009 00:00:00 +0100 3341888 http://www.medworm.com/index.php?rid=3341880&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006666%2Fabstract%3Frss%3Dyes In this study, the handgrip height was optimized by a two-dimensional mechanical model to reduce muscular loads in the lower body as well as in the upper body with various road conditions during steady walking. A critical height of the handgrip existed at 48% of the body height for the user regardless of gender and body dimension. A lower handgrip relieved muscular load for stooping users with a lower standing height. The stooping user pushed the handgrip strongly in the perpendicular direction by leaning the upper body on the walker. However, upright users with a higher standing height should use a four-wheeled walker with a higher handgrip for maintaining his or her upright posture. For downhill movement, the optimal handgrip height depended on the slope angle and the friction coefficien... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341880 Mon, 14 Dec 2009 00:00:00 +0100 3341880 http://www.medworm.com/index.php?rid=3341879&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006678%2Fabstract%3Frss%3Dyes Abstract: The optical characteristics of the human cornea depends on the mechanical balance between the intra-ocular pressure and intrinsic tissue stiffness. A wide range of ophthalmic surgical procedures alter corneal biomechanics to induce local or global curvature changes for the correction of visual acuity. Due to the large number of surgical interventions performed every day, a deeper understanding of corneal biomechanics is needed to improve the safety of these procedures and medical devices. The aim of this study is to propose a biomechanical model of the human cornea, based on stromal microstructure. The constitutive mechanical law includes collagen fiber distribution based on X-ray scattering analysis, collagen cross-linking, and fiber uncrimping. Our results showed that the propo... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341879 Mon, 14 Dec 2009 00:00:00 +0100 3341879 http://www.medworm.com/index.php?rid=3272466&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006290%2Fabstract%3Frss%3Dyes We examined whether these surface strains in the mouse tibia are modified following two weeks of load-induced adaptation by comparison with contralateral controls. Results indicated non-uniform strain patterns with isolated areas of high strain (0.5%), particularly on the medial side. Strain measurements were reproducible (standard deviation of the error 0.03%), similar between specimens, and in agreement with strain gauge measurements (between 0.1 and 0.2% strain). After structural adaptation, strains were more uniform across the tibial surface, particularly on the medial side where peak strains were reduced from 0.5% to 0.3%. Because DIC determines local strains over the entire surface, it will provide a better understanding of how strain stimulus influences the bone response during adap... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272466 Mon, 14 Dec 2009 00:00:00 +0100 3272466 http://www.medworm.com/index.php?rid=3341903&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006514%2Fabstract%3Frss%3Dyes Abstract: The purpose of this study was to determine the changes that occur in tendinous tissue properties during the early phase of tetanic summation in the in vivo human tibialis anterior muscle (TA). The torque response and tendinous tissue elongation following single stimuli, two-pulse trains, and three-pulse trains were recorded in the TA during isometric contractions. The elongation, compliance, and lengthening velocity of tendinous tissue were determined by real-time ultrasonography. The contribution of the response to the second stimulation (C2) was obtained by subtracting the response to the single stimulation (C1) from the response of doublet. The third contribution (C3) was obtained by subtracting the response to the doublet from that of the triplet. C2 (7.8±0.5Nm) and C3 (7.3�... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341903 Fri, 11 Dec 2009 00:00:00 +0100 3341903 http://www.medworm.com/index.php?rid=3272479&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005971%2Fabstract%3Frss%3Dyes In conclusion, collision detection can prevent reconstructing impossible poses and it improves the position and motion estimation in the out-of-plane direction. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272479 Fri, 11 Dec 2009 00:00:00 +0100 3272479 http://www.medworm.com/index.php?rid=3204377&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005685%2Fabstract%3Frss%3Dyes Abstract: Strain shielding, a mechanical effect occurring in structures combining stiff with more flexible materials, is considered to lead to a reduction of density in bone surrounding the implant. This effect can be related to the weakness of the implant fixation, which can promote implant loosening. Several studies describe a significant decrease in postoperative bone mineral density adjacent to joint implants, which can compromise their long-term fixation. The aim of the present study was to quantify the strain shielding effect on the distal femur after patellofemoral arthroplasty. For this purpose three activities of daily living were considered: level walking, stair climbing and deep bending at different angles of knee flexion. To determine the strain shielding effect, cortical bone ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204377 Fri, 11 Dec 2009 00:00:00 +0100 3204377 http://www.medworm.com/index.php?rid=3084371&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006629%2Fabstract%3Frss%3Dyes (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3084371 Fri, 11 Dec 2009 00:00:00 +0100 3084371 http://www.medworm.com/index.php?rid=3084370&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009004680%2Fabstract%3Frss%3Dyes 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 20μm 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 machining of living tissues such as ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3084370 Fri, 11 Dec 2009 00:00:00 +0100 3084370 http://www.medworm.com/index.php?rid=3084358&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009004618%2Fabstract%3Frss%3Dyes Abstract: 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 (, 2009). They are evaluated for three different severit... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3084358 Fri, 11 Dec 2009 00:00:00 +0100 3084358 http://www.medworm.com/index.php?rid=3084350&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009004655%2Fabstract%3Frss%3Dyes This study provides data that may explain the mechanisms behind the effectiveness of eccentric exercises used in the treatment of Achilles tendinopathies. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3084350 Fri, 11 Dec 2009 00:00:00 +0100 3084350 http://www.medworm.com/index.php?rid=3084338&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS002192900900654X%2Fabstract%3Frss%3Dyes (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3084338 Fri, 11 Dec 2009 00:00:00 +0100 3084338 http://www.medworm.com/index.php?rid=3341901&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006630%2Fabstract%3Frss%3Dyes This study aims to characterize stress relaxation in the musculotendinous and ligamentous structures crossing the human ankle (ankle-only structures and the gastrocnemius muscle–tendon unit, which crosses the ankle and knee), and to determine whether stress relaxation is independent of the length of these structures. Two experiments were conducted on 8 healthy subjects. The first experiment compared stress relaxation over 10min at different gastrocnemius muscle–tendon unit lengths keeping the length of ankle-joint only structures fixed. The second experiment compared stress relaxation at different lengths of ankle-joint only structures keeping gastrocnemius muscle–tendon unit length fixed. Stress relaxation data were fitted with a two-term exponential function (T=G0+G1e−λ1t+G2e−... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341901 Thu, 10 Dec 2009 00:00:00 +0100 3341901 http://www.medworm.com/index.php?rid=3341893&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006381%2Fabstract%3Frss%3Dyes Abstract: An analytical model of the fluid/cell mechanical interaction was developed. The interfacial shear stress, due to the coupling between the fluid and the cell deformation, was characterized by a new dimensionless number Nfs. For Nfs above a critical value, the fluid/cell interaction had a damping effect on the interfacial shear stress. Conversely, for Nfs below this critical value, interfacial shear stress was amplified. As illustration, the role of the dynamic fluid/cell mechanical coupling was studied in a specific biological situation involving cells seeded in a bone scaffold. For the particular bone scaffold chosen, the dimensionless number Nfs was higher than the critical value. In this case, the dynamic shear stress at the fluid/cell interface is damped for increasing excitat... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341893 Thu, 10 Dec 2009 00:00:00 +0100 3341893 http://www.medworm.com/index.php?rid=3341896&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS002192900900637X%2Fabstract%3Frss%3Dyes Abstract: Mechanical testing has been regarded as the gold standard to investigate the effects of pathologies on the structure–function properties of the skeleton. With recent advances in computing power of personal computers, virtual alternatives to mechanical testing are gaining acceptance and use. We have previously introduced such a technique called structural rigidity analysis to assess mechanical strength of skeletal tissue with defects. The application of this technique is predicated upon the use of relationships defining the strength of bone as a function of its density for a given loading mode. We are to apply this technique in rat models to assess their compressive skeletal response subjected to a host of biological and pharmaceutical stimulations. Therefore, the aim of this st... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341896 Wed, 09 Dec 2009 00:00:00 +0100 3341896 http://www.medworm.com/index.php?rid=3341881&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006642%2Fabstract%3Frss%3Dyes In this study, a novel metal-on-metal hip implant employing a specific aspherical bearing surface, Alpharabola, as the acetabular surface was investigated for both contact mechanics and elastohydrodynamic lubrication under steady-state conditions. When compared with conventional spherical bearing surfaces, a more uniform pressure distribution and a thicker lubricant film thickness within the loaded conjunction were predicted for this novel Alpharabola hip implant. The effects of the geometric parameters of this novel acetabular surface on the pressure distribution and lubricant thickness were investigated. A significant increase in the predicted lubricant film thickness and a significant decrease in the dry contact and hydrodynamic pressures were found with appropriate combinations of thes... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341881 Wed, 09 Dec 2009 00:00:00 +0100 3341881 http://www.medworm.com/index.php?rid=3341895&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS002192900900640X%2Fabstract%3Frss%3Dyes This study evaluates a novel method for predicting muscle and contact forces simultaneously in the knee during gait. The method utilizes a 12 degree-of-freedom knee model (femur, tibia, and patella) combining muscle, articular contact, and dynamic skeletal models. Eight static optimization problems were formulated using two cost functions (one based on muscle activations and one based on contact forces) and four constraints sets (each composed of different combinations of inverse dynamic loads). The estimated muscle and contact forces were evaluated using in vivo tibial contact force data collected from a patient with a force-measuring knee implant. When the eight optimization problems were solved with added constraints to match the in vivo contact force measurements, root-mean-square erro... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341895 Mon, 07 Dec 2009 00:00:00 +0100 3341895 http://www.medworm.com/index.php?rid=3341886&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006460%2Fabstract%3Frss%3Dyes In this study, a cell based lattice free modelling framework is proposed to study cell aggregate behaviour in bone tissue engineering applications. The model encompasses cell-to-cell and cell–environment interactions such as adhesion, repulsion and drag forces. Oxygen, nutrients, waste products, growth factors and inhibitors are explicitly represented in the model influencing cellular behaviour. Furthermore, a model for cell metabolism is incorporated representing the basic enzymic reactions of glycolysis and the Krebs cycle. Various types of cell death such as necrosis, apoptosis and anoikis are implemented. Finally, an explicit model of the cell cycle controls the proliferation process, taking into account the presence or absence of various metabolites, sufficient space and mechanical ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341886 Fri, 04 Dec 2009 00:00:00 +0100 3341886 http://www.medworm.com/index.php?rid=3341876&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006654%2Fabstract%3Frss%3Dyes Abstract: Because bone marrow-derived stromal cells (BMSCs) are able to generate many cell types, they are envisioned as source of regenerative cells to repair numerous tissues, including bone, cartilage, and ligaments. Success of BMSC-based therapies, however, relies on a number of methodological improvements, among which better understanding and control of the BMSC differentiation pathways. Since many years, the biochemical environment is known to govern BMSC differentiation, but more recent evidences show that the biomechanical environment is also directing cell functions. Using in vitro systems that aim to reproduce selected components of the in vivo mechanical environment, it was demonstrated that mechanical loadings can affect BMSC proliferation and improve the osteogenic, chondrogen... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341876 Fri, 04 Dec 2009 00:00:00 +0100 3341876 http://www.medworm.com/index.php?rid=3272480&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005946%2Fabstract%3Frss%3Dyes Abstract: The development of a biomechanical model for a human finger is faced with many challenges, such as extensor mechanism complexity, statistical indeterminacy and suitability of computational processes. Motivation for this work was to develop a computer model that is able to predict the internal loading patterns of tendons and joint surfaces experienced by the human finger, while mitigating these challenges. Proposed methodology was based on a non-linear optimising mathematical technique with a criterion of boundary conditions and equality equations, maximised against unknown parameters to reduce statistical indeterminacy. Initial validation was performed via the simulation of one dynamic and two static postures case studies. Past models and experiments were used, based on published... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272480 Fri, 04 Dec 2009 00:00:00 +0100 3272480 http://www.medworm.com/index.php?rid=3341905&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006368%2Fabstract%3Frss%3Dyes This study is aimed at acquiring geometric data of cartilage surfaces and ligaments from individual wrist joints by using a cryomicrotome imaging system and the evaluation of inter- and intra-observer variability of the data.The 3D geometry of 30 cartilage surfaces and 15 ligaments in three cadaver wrists was manually detected and quantitatively reconstructed. The inter- and intra-observer variability of the cartilage surface detection was 0.14 and 0.19mm, respectively. For the position of the radius attachment of the dorsal radiocarpal ligament (DRC), the observer variations were 0.12 and 0.65mm, for intra-/inter-observer, respectively. For the DRC attachment on the triquetrum, the observer variations were 0.22 and 1.19mm.Anatomic reconstruction from 3D cryomicrotome images offer a method... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341905 Thu, 03 Dec 2009 00:00:00 +0100 3341905 http://www.medworm.com/index.php?rid=3341900&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006344%2Fabstract%3Frss%3Dyes Abstract: Nearly all soft tissues, among which the vascular tissue is included, present a certain degree of viscoelastic response. This behaviour may be attributed in part to fluid transport within the solid matrix, and to the friction between its fluid and solid constituents. After being preconditioned, the tissue displays highly repetitive behaviour, so that it can be considered pseudo-elastic, that is, elastic but behaving differently in loading and unloading. Because of this reason, very few constitutive laws accounting for the viscoelastic behaviour of the tissue have been developed. Nevertheless, the consideration of this inelastic effect is of crucial importance in surgeries—like vascular angioplasty—where the mentioned preconditioning cannot be considered since non-physiologica... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341900 Thu, 03 Dec 2009 00:00:00 +0100 3341900 http://www.medworm.com/index.php?rid=3341899&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006307%2Fabstract%3Frss%3Dyes In this study, finite element models which use the local degree of polymerisation to calculate material properties and shrinkage have been used to predict residual stresses in two models of total hip replacement cement mantles. Results indicate that the final value of cement mantle stress may not be the highest stresses that the cement is subjected to during the polymerisation process. Two models are presented, a 2-dimensional model, which was adapted from a similar model in the literature () and a 3-dimensional concentric-cylinders model. In both cases a chemical kinetics model was used to predict the progress of the polymerisation reaction and a second linear model used to predict cement mechanical properties and density, and so stress generation and volume change, over time. There was g... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341899 Thu, 03 Dec 2009 00:00:00 +0100 3341899 http://www.medworm.com/index.php?rid=3341894&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006423%2Fabstract%3Frss%3Dyes Abstract: Three-dimensional (3D) path of the body centre of mass (CM) over an entire stride was computed from ground reaction forces during walking at constant average speed on a treadmill mounted on 3D force sensors. Data were obtained from 18 healthy adults at speeds ranging from 0.30 to 1.40ms−1, in 0.1ms−1 increments. Six subsequent strides were analyzed for each subject and speed (total strides=1296). The test session lasted about 30min (10min for walking). The CM path had an upward concave figure-of-eight shape that was highly consistent within and across subjects. Vertical displacement of the CM increased monotonically as a function of walking speed. The forward and particularly lateral displacements of the CM showed a U-shaped relationship to speed. The same held for the total ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341894 Thu, 03 Dec 2009 00:00:00 +0100 3341894 http://www.medworm.com/index.php?rid=3341897&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006319%2Fabstract%3Frss%3Dyes This study demonstrates the feasibility of computational design approaches for bone tissue engineering. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341897 Wed, 02 Dec 2009 00:00:00 +0100 3341897 http://www.medworm.com/index.php?rid=3341892&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006356%2Fabstract%3Frss%3Dyes Abstract: Biological soft tissues exhibit a strongly nonlinear viscoelastic behaviour. Among parenchymous tissues, kidney and liver remain less studied than brain, and a first goal of this study is to report additional material properties of kidney and liver tissues in oscillatory shear and constant shear rate tests. Results show that the liver tissue is more compliant but more strain hardening than kidney. A wealth of multi-parameter mathematical models has been proposed for describing the mechanical behaviour of soft tissues. A second purpose of this work is to develop a new constitutive law capable of predicting our experimental data in the both linear and nonlinear viscoelastic regime with as few parameters as possible. We propose a nonlinear strain-hardening fractional derivative mode... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341892 Wed, 02 Dec 2009 00:00:00 +0100 3341892 http://www.medworm.com/index.php?rid=3341890&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006332%2Fabstract%3Frss%3Dyes Abstract: Muscle fatigue alters neuromuscular responses. This may lead to increased sensitivity to perturbations and possibly to subsequent injury risk. We studied the effects of muscle fatigue on movement stability during a repetitive upper extremity task. Twenty healthy young subjects performed a repetitive work task, similar to sawing, synchronized with a metronome before and after performing each of two fatiguing tasks. The first fatigue task (LIFT) primarily fatigued the shoulder flexor muscles, while the second fatigue task (SAW) fatigued all of the muscles of the arm. Subjects performed each task in random order on two different days at least seven days apart. Instantaneous mean EMG frequencies (IMNF) decreased over both fatiguing tasks indicating that subjects did experience signif... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341890 Mon, 30 Nov 2009 00:00:00 +0100 3341890 http://www.medworm.com/index.php?rid=3272467&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006289%2Fabstract%3Frss%3Dyes Abstract: Despite numerous reports on isometric force depression, few reports have quantified force depression during active muscle shortening (dynamic force depression). The purpose of this investigation was to determine the influence of shortening history on isometric force following active shortening, force during isokinetic shortening, and velocity during isotonic shortening. The soleus muscles of four cats were subjected to a series of isokinetic contractions at three shortening velocities and isotonic contractions under three loads. Muscle excursions initiated from three different muscle lengths but terminated at a constant length. Isometric force produced subsequent to active shortening, and force or shortening velocity produced at a specific muscle length during shortening, were co... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272467 Mon, 30 Nov 2009 00:00:00 +0100 3272467 http://www.medworm.com/index.php?rid=3204388&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005533%2Fabstract%3Frss%3Dyes Abstract: The aim of this work was to investigate the effects of age-related sarcopenia on the time and frequency domain properties of lower extremity muscles’ electromyographic and mechanomyographic activities. Healthy elderly (n=10, 64.5±4.5yr) and young (n=10, 22.6±2.8yr) were recruited as participants. Participants’ lean thigh volumes (LTV) and 1 RM (one repetition maximum) leg strength of quadriceps and maximum speed knee extension with different load levels (45%, 60% and 75% 1 RM) were recorded. The root mean square (RMS) and the mean frequency (MF) of the surface electromyography (EMGRMS, EMGMF) and mechanomyography (MMGRMS, MMGMF) signals were collected at vastus lateralis during concentric contraction with different intensity levels. Compared to the young, the elderly had si... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204388 Mon, 30 Nov 2009 00:00:00 +0100 3204388 http://www.medworm.com/index.php?rid=3341906&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006277%2Fabstract%3Frss%3Dyes Abstract: Generation of subject-specific finite element (FE) models from computed tomography (CT) datasets is of significance for application of the FE analysis to bone structures. A great challenge that remains is the automatic assignment of bone material properties from CT Hounsfield Units into finite element models. This paper proposes a new assignment approach, in which material properties are directly assigned to each integration point. Instead of modifying the dataset of FE models, the proposed approach divides the assignment procedure into two steps: generating the data file of the image intensity of a bone in a MATLAB program and reading the file into ABAQUS via user subroutines. Its accuracy has been validated by assigning the density of a bone phantom into a FE model. The propose... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3341906 Fri, 27 Nov 2009 00:00:00 +0100 3341906 http://www.medworm.com/index.php?rid=3272484&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005909%2Fabstract%3Frss%3Dyes In this study, we experimentally test the hypothesis that differences in local average of heterogeneous strains in a polymer scaffold will correlate with induced differences in the local biological response.Twenty-four poly(l-lactic acid) porous scaffolds seeded with rat bone cells were cultured first for 2 and 3 weeks under static conditions, respectively. Then for 1 week, half of the scaffolds were cyclically compressed (1.5%, 1Hz), 1h daily, with continuous perfusion (0.1ml/min). The remaining half was kept under static conditions. The pore-surface strains in the scaffolds at the start of culture were calculated with micro-finite element modelling based on micro-Computed Tomography (μCT) images. The locations of mineralized nodules were determined from μCT images and coupled to the ca... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272484 Fri, 27 Nov 2009 00:00:00 +0100 3272484 http://www.medworm.com/index.php?rid=3272481&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005934%2Fabstract%3Frss%3Dyes Abstract: Fixation failure of glenoid components is the main cause of unsuccessful total shoulder arthroplasties. The characteristics of these failures are still not well understood, hence, attempts at improving the implant fixation are somewhat blind and the failure rate remains high. This lack of understanding is largely due to the fundamental problem that direct observations of failure are impossible as the fixation is inherently embedded within the bone.Twenty custom made implants, reflecting various common fixation designs, and a specimen set-up was prepared to enable direct observation of failure when the specimens were exposed to cyclic superior loads during laboratory experiments. Finite element analyses of the laboratory tests were also carried out to explain the observed failure ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272481 Thu, 26 Nov 2009 00:00:00 +0100 3272481 http://www.medworm.com/index.php?rid=3272472&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006046%2Fabstract%3Frss%3Dyes Abstract: The aim of this study was to investigate the interactions of implant position, implant–abutment connection and loading condition influencing bone loss of an implant placed in the maxilla using finite element (FE) analysis and mathematical bone remodeling theory. The maxilla section contours were acquired using CT images to construct FE models containing RS (internal retaining-screw) and the TIS (taper integrated screwed-in) implants placed in SC (along the axis of occlusal force) and RA (along the axis of residual ridge) positions. The adaptive strain energy density (SED) algorithm was combined with FE approach to study the preliminary bone remodeling around implant systems under different load conditions. The simulated results showed that the implant position obviously influen... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272472 Thu, 26 Nov 2009 00:00:00 +0100 3272472 http://www.medworm.com/index.php?rid=3272469&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006241%2Fabstract%3Frss%3Dyes Abstract: Mesenchymal stem cell (MSC) differentiation can be influenced by biophysical stimuli imparted by the host scaffold. Yet, causal relationships linking scaffold strain magnitudes and inlet fluid velocities to specific cell responses are thus far underdeveloped. This investigation attempted to simulate cell responses in a collagen–glycosaminoglycan (CG) scaffold within a bioreactor. CG scaffold deformation was simulated using μ-computed tomography (CT) and an in-house finite element solver (FEEBE/linear). Similarly, the internal fluid velocities were simulated using the afore-mentioned μCT dataset with a computational fluid dynamics solver (ANSYS/CFX). From the ensuing cell-level mechanics, albeit octahedral shear strain or fluid velocity, the proliferation and differentiation o... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272469 Thu, 26 Nov 2009 00:00:00 +0100 3272469 http://www.medworm.com/index.php?rid=3204386&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005569%2Fabstract%3Frss%3Dyes Abstract: The purpose of this study was to determine individualized optimal release angles for elite discus throwers. Three-dimensional coordinate data were obtained for at least 10 competitive trials for each subject. Regression relationships between release speed and release angle, and between aerodynamic distance and release angle were determined for each subject. These relationships were linear with subject–specific characteristics. The subject–specific relationships between release speed and release angle may be due to subjects’ technical and physical characteristics. The subject–specific relationships between aerodynamic distance and release angle may be due to interactions between the release angle, the angle of attack, and the aerodynamic distance. Optimal release angles we... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204386 Thu, 26 Nov 2009 00:00:00 +0100 3204386 http://www.medworm.com/index.php?rid=3120119&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005375%2Fabstract%3Frss%3Dyes This study describes the development and application of a novel rat patellar tendon model of mechanical fatigue for investigating the early in vivo response to tendon subfailure injury. Patellar tendons of adult female Sprague-Dawley rats were fatigue loaded between 1–35N using a custom-designed loading apparatus. Patellar tendons were subjected to Low-, Moderate- or High-level fatigue damage, defined by grip-to-grip strain measurement. Molecular response was compared with that of a laceration-repair injury. Histological analyses showed that progression of tendon fatigue involves formation of localized kinked fiber deformations at Low damage, which increased in density with presence of fiber delaminations at Moderate damage, and fiber angulation and discontinuities at High damage levels.... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120119 Thu, 26 Nov 2009 00:00:00 +0100 3120119 http://www.medworm.com/index.php?rid=3272492&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006058%2Fabstract%3Frss%3Dyes Abstract: Due to inadequate healing, surgical repairs of torn rotator cuff tendons often fail, limiting the recovery of upper extremity function. The rat is frequently used to study rotator cuff healing; however, there are few systems capable of quantifying forelimb function necessary to interpret the clinical significance of tissue level healing. We constructed a device to capture images, ground reaction forces and torques, as animals ambulated in a confined walkway, and used it to evaluate forelimb function in uninjured control and surgically injured/repaired animals. Ambulatory data were recorded before (D–1), and 3, 7, 14, 28 and 56 days after surgery. Speed as well as step width and length were determined by analyzing ventral images, and ground reaction forces were normalized to bod... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272492 Fri, 20 Nov 2009 00:00:00 +0100 3272492 http://www.medworm.com/index.php?rid=3272490&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006083%2Fabstract%3Frss%3Dyes The objective of this study is to compare the accuracy of manual digitization and contour registration in measuring superior translation of the humeral head. Eight pairs of cadaver scapulae and humerii bones were harvested for this study. Each scapula and humerus was secured in a customized jig that allowed for control of humeral head translations and a vise that permitted rotations of the scapula about three axes. Fluoroscopy was used to take images of the shoulder bones. Scapular orientation was manipulated in different positions while the humerus was at 90° of humeral elevation in the scapular plane. Humeral head translation was measured using the two methods and was compared to the known translation. Additionally, accuracy of the contour registration method to measure 2-D scapular rot... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272490 Fri, 20 Nov 2009 00:00:00 +0100 3272490 http://www.medworm.com/index.php?rid=3272485&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005892%2Fabstract%3Frss%3Dyes In this study, accurate geometric reconstructions of in-vitro (PTFE tube) and ex-vivo (canine artery) deployed stents based on ultra-high resolution MicroCT imaging were used. The primary goal was to compare the hemodynamic effects of deployment in these two different models and to identify flow perturbations due to deployment anomalies such as stent malapposition and strut prolapse, important adverse mechanics occurring in clinical practice, but not considered in studies using idealized stent models.Ultra-high resolution MicroCT data provided detailed visualization of deployment characteristics allowing for accurate in-stent flow simulation. For stent cells that are regularly and symmetrically deployed, the near wall flow velocities and wall shear stresses were similar to previously publi... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272485 Fri, 20 Nov 2009 00:00:00 +0100 3272485 http://www.medworm.com/index.php?rid=3272475&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006010%2Fabstract%3Frss%3Dyes This study sought to define error in foot kinematic data due to violation of the rigid segment assumption. The research compared kinematic data from 17 different mid and forefoot rigid segment models to kinematic data of the individual bones comprising these segments. Kinematic data from a previous dynamic cadaver model study was used to derive individual bone as well as foot segment kinematics.Mean and maximum errors due to violation of the rigid body assumption varied greatly between models. The model with least error was the combination of navicular and cuboid (mean errors (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272475 Fri, 20 Nov 2009 00:00:00 +0100 3272475 http://www.medworm.com/index.php?rid=3204370&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005788%2Fabstract%3Frss%3Dyes This study has shown that the development of the acoustic and vibration technique provides a practical method and generates new possibilities for a better understanding of THA performance. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204370 Fri, 20 Nov 2009 00:00:00 +0100 3204370 http://www.medworm.com/index.php?rid=3120124&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009004515%2Fabstract%3Frss%3Dyes Abstract: Several spring–damper–mass models of the human body have been developed in order to reproduce the measured ground vertical reaction forces during human running (; Ferris et al., 1999; ). In particular, Liu and Nigg introduced at the lower level of their model, i.e. at the interface between the human body and the ground, a nonlinear element representing simultaneously the shoe midsoles and the ground flexibility. The ground reaction force is modelled as the force supported by this nonlinear element, whose parameters are identified from several sets of experimental data. This approach proved to be robust and quite accurate. However, it does not explicitly take into account the shoe and the ground properties. It turns out to be impossible to study the influence of shoe materials... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120124 Fri, 20 Nov 2009 00:00:00 +0100 3120124 http://www.medworm.com/index.php?rid=3272470&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006101%2Fabstract%3Frss%3Dyes The objective of this study was to quantify the load on the horse's back in these riding techniques. Kinematic data of 13 riders were collected in rising and sitting trot. The time-history of the position of the rider's centre of mass (CoM) was calculated, and differentiated twice to obtain the acceleration of the CoM. The reaction force between the rider and the horse's back was calculated from the acceleration. Forces were divided by the body weight of the rider to obtain dimensionless forces. As expected, the computed average vertical force did not differ between riding techniques and was not significantly different from the body weight of the riders. At trot, two force peaks were present during one stride cycle. Both peaks in rising trot were significantly lower compared to sitting tro... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272470 Thu, 19 Nov 2009 00:00:00 +0100 3272470 http://www.medworm.com/index.php?rid=3272491&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006071%2Fabstract%3Frss%3Dyes Abstract: Uncontrolled Manifold (UCM) analysis has been used to identify a component of joint variance leading to pointer-tip position variability and a component representing motor abundant joint combinations corresponding to an equivalent pointer-tip position. A Jacobian is required for UCM analysis, typically derived from an analytic model relating joint postures to pointer-tip position. Derivation of the Jacobian is often non-trivial, however, because of the complexity of the system being studied. In this article, we compared the effect of different methods of deriving the Jacobian on results of UCM analyses during reaching. Jacobian matrices were determined at each percentage of the reach across trials using one of three methods: (M1) partial derivatives of the geometric model relatin... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272491 Wed, 18 Nov 2009 00:00:00 +0100 3272491 http://www.medworm.com/index.php?rid=3272495&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005879%2Fabstract%3Frss%3Dyes Abstract: Callus formation occurs in the presence of secondary bone healing and has relevance to the fracture's mechanical environment. An objective image processing algorithm was developed to standardize the quantitative measurement of periosteal callus area in plain radiographs of long bone fractures. Algorithm accuracy and sensitivity were evaluated using surrogate models. For algorithm validation, callus formation on clinical radiographs was measured manually by orthopaedic surgeons and compared to non-clinicians using the algorithm. The algorithm measured the projected area of surrogate calluses with less than 5% error. However, error will increase when analyzing very small areas of callus and when using radiographs with low image resolution (i.e. 100 pixels per inch). The callus size... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272495 Mon, 16 Nov 2009 00:00:00 +0100 3272495 http://www.medworm.com/index.php?rid=3272482&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005922%2Fabstract%3Frss%3Dyes This study compares logistic regression (LR), probabilistic neural network (PNN) and support vector machine (SVM) classifiers for discriminating between normal and PD subjects in assessing the effects of DBS-STN on ground reaction force (GRF) with and without medication. Gait analysis of 45 subjects (30 normal and 15 PD subjects who underwent bilateral DBS-STN) was performed. PD subjects were assessed under four test conditions: without treatment (mof-sof), with stimulation alone (mof-son), with medication alone (mon-sof), and with medication and stimulation (mon-son). Principal component (PC) analysis was applied to the three components of GRF separately, where six PC scores from vertical, one from anterior–posterior and one from medial–lateral were chosen by the broken stick test. St... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272482 Mon, 16 Nov 2009 00:00:00 +0100 3272482 http://www.medworm.com/index.php?rid=3272477&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005995%2Fabstract%3Frss%3Dyes Abstract: The purpose of this work was the force–displacement response analysis of the masticatory process in a dried human skull by Double-Exposure Photorefractive Holographic Interferometry Technique (2E-PRHI). The load concentration and dissipation of the forces from dried human skull were analysed at applied loading stands as a Simulation of Isolated Contraction (SIC) of some mastication muscles. The 2EHI and Fringe Analysis Method were used to obtain the quantitative results of this force–displacement response. These results document quantitatively the real biomechanical response from dried human skull under applied loading and it can be used for complementary study by finite element model and others analysis type. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272477 Mon, 16 Nov 2009 00:00:00 +0100 3272477 http://www.medworm.com/index.php?rid=3114438&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009004941%2Fabstract%3Frss%3Dyes Abstract: Dynamic regulation of the filamentous actin (F-actin) cytoskeleton is critical to numerous physical cellular processes, including cell adhesion, migration and division. Each of these processes require precise regulation of cell shape and mechanical force generation which, to a large degree, is regulated by the dynamic mechanical behaviors of a diverse assortment of F-actin networks and bundles. In this review, we review the current understanding of the mechanics of F-actin networks and identify areas of further research needed to establish physical models. We first review our understanding of the mechanical behaviors of F-actin networks reconstituted in vitro, with a focus on the nonlinear mechanical response and behavior of “active” F-actin networks. We then explore the type... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3114438 Mon, 16 Nov 2009 00:00:00 +0100 3114438 http://www.medworm.com/index.php?rid=3204383&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005739%2Fabstract%3Frss%3Dyes Abstract: Primary stability of uncemented resurfacing prosthesis is provided by an interference fit between the undersized implant and the reamed bone. Dependent on the magnitude of interference, the implantation process causes high shear forces and large strains which can exceed the elastic limit of cancellous bone. Plastification of the bone causes reduced stiffness and could lead to bone damage and implant loosening. The purpose in this study was to determine press-fit conditions which allow implantation without excessive plastic bone deformation and sufficient primary stability to achieve bone ingrowth. In particular, the influence of interference, bone quality and friction on the micromotion during walking and stair-climbing was investigated. Therefore elastic and plastic finite eleme... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204383 Fri, 13 Nov 2009 00:00:00 +0100 3204383 http://www.medworm.com/index.php?rid=3272488&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006253%2Fabstract%3Frss%3Dyes Abstract: We adapt a biomechanical argument of Rashevsky, which places limits on the stress experienced by a torso supported by the legs, to deduce that body mass m of growing children should scale as the p th power of height h with . Further arguments based on stability and heat loss suggest that p should be close to . The arguments are extended to suggest that waist circumference w should scale as with q near the lower end of . Data from Hong Kong and British children are consistent with these hypotheses. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272488 Thu, 12 Nov 2009 00:00:00 +0100 3272488 http://www.medworm.com/index.php?rid=3272486&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005880%2Fabstract%3Frss%3Dyes Abstract: The purpose of this study was to determine the reliability of investigating electromyography (EMG) of selected leg muscles during walking. Tibialis posterior and peroneus longus EMG activity were recorded via intramuscular electrodes. Tibialis anterior and medial gastrocnemius EMG activity were recorded with surface electrodes. Twenty-eight young adults attended two test-sessions approximately 15 days apart. Relative and absolute measures of reliability were calculated for EMG timing and amplitude parameters during specific phases of the gait cycle. Maximum contractions and sub-maximal contractions were obtained via maximum isometric voluntary contractions and a very fast walking speed, respectively. Time of peak EMG amplitude for all muscles displayed relatively narrow limits of... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272486 Thu, 12 Nov 2009 00:00:00 +0100 3272486 http://www.medworm.com/index.php?rid=3204392&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS002192900900579X%2Fabstract%3Frss%3Dyes This study examined whether the ACL volume is significantly different between the left and right knees of uninjured subjects. ACL volumes were calculated for the left and right sides of 28 individuals using a previously validated MRI-based method. The mean ACL volume was not significantly different (p=0.2331) between the two sides in this population. Side-to-side ACL volume was also well correlated (correlation=0.91, p (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204392 Thu, 12 Nov 2009 00:00:00 +0100 3204392 http://www.medworm.com/index.php?rid=3120127&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005284%2Fabstract%3Frss%3Dyes Abstract: Clinical studies have recently documented that there is sufficient evidence to suggest that abnormal motion may be an indicator of abnormal mechanics of the spine and, therefore, may be associated with some types of low-back pain. However, designating a motion as abnormal requires knowledge of normal motions. This work hence aims to develop an accurate computational model to simulate the bio-mechanical response of the whole lumbosacral spinal unit (L1–S1) under physiological loadings and constraint conditions. In order to meet this objective, computed tomography (CT) scanning protocols, finite element (FE) analysis and accurate constitutive modelling have been integrated. Then the ranges of motion (ROM) under flexion, extension and lateral bending moment were measured and compa... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120127 Thu, 12 Nov 2009 00:00:00 +0100 3120127 http://www.medworm.com/index.php?rid=3120106&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005454%2Fabstract%3Frss%3Dyes Abstract: Vertebral arteries are two arteries whose structure and location in human body result in development of special flow conditions. For some of the arteries, one can observe a significant difference between flow rates in the left and the right arteries during ultrasonography diagnosis. Usually the reason of such a difference was connected with pathology of the artery in which a smaller flow rate was detected. Simulations of the flow through the selected type of the vertebral artery geometry for twenty five cases of artery diameters have been carried out. The main aim of the presented experiment was to visualize the flow in the region of vertebral arteries junction in the origin of the basilar artery. It is extremely difficult to examine this part of human circulation system, thus nu... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120106 Thu, 12 Nov 2009 00:00:00 +0100 3120106 http://www.medworm.com/index.php?rid=3272494&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005958%2Fabstract%3Frss%3Dyes Abstract: We have developed a technique to directly observe the micromechanics of the stem–cement and cement–bone interfaces of cemented femoral stems under physiologically relevant loading conditions. Thick transverse sections of a stem–cement–femur construct were fixed to the base of a test frame. Ante- and retro-verting torques were applied to the femoral stem by screwing the stem (via a pair of through holes) to an axle, which was turned using a lever arm actuated by the test frame cross-head. The surface of each transverse section was serially digitally imaged during loading. The displacements of the stem, cement and bone were determined using digital image correlation. These data were then used to calculate the relative displacements across the interfaces. This method provide... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272494 Wed, 11 Nov 2009 00:00:00 +0100 3272494 http://www.medworm.com/index.php?rid=3272489&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006095%2Fabstract%3Frss%3Dyes Abstract: The displacement of a calibrated horizontal bar is used as a measure for forces acting on the bar itself during dynamic performances in artistic gymnastics. The high bar is loaded with known forces and the displacement is monitored by means of a Vicon motion capturing system. The calibration results are fitted according to the Euler–Bernoulli beam theory. After calibration, forces can straightforwardly be measured by multiplication of the bar displacement with the determined fit parameter. This approach is also able to account for non-central force application (two hands on the bar) and the effect of the bar's inertia. Uncertainties in measured forces are assessed to be plus an additional 1% for the unknown weight distribution between the two hands. (Source: Journal of Biomecha... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272489 Wed, 11 Nov 2009 00:00:00 +0100 3272489 http://www.medworm.com/index.php?rid=3272471&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS002192900900606X%2Fabstract%3Frss%3Dyes Abstract: Polymeric stents can be considered as an alternative to metallic stents thanks to their lessened incidence of restenosis and controlled deployment. The purpose of this study was to investigate the feasibility of developing a temperature-responsive braided stent using shape memory polyurethane (SMPU) through finite element analysis. It was assumed that braided stents were manufactured using SMPU fibers. The mechanical behavior of SMPU fibers was modeled using a constitutive equation describing their one-dimensional thermal-induced shape memory behavior. Then, the braided stents were analyzed to investigate their mechanical behavior using finite element analysis software, in which the constitutive equation was implemented through a user material subroutine. The diameter of the SMPU... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272471 Wed, 11 Nov 2009 00:00:00 +0100 3272471 http://www.medworm.com/index.php?rid=3272483&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005910%2Fabstract%3Frss%3Dyes The objective of this study, therefore, was to evaluate the mechanical properties, fiber alignment, change in alignment with applied load, and structure–function relationships of SST in transverse testing. Samples from six SST locations were tested in uniaxial tension with samples oriented transverse to the tendon long-axis. Polarized light imaging was used to quantify collagen fiber alignment and change in alignment under applied load. The mechanical properties of samples taken near the tendon–bone insertion were much greater on the bursal surface compared to the joint surface (e.g., bursal moduli 15–30 times greater than joint; p (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272483 Mon, 09 Nov 2009 00:00:00 +0100 3272483 http://www.medworm.com/index.php?rid=3272478&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005983%2Fabstract%3Frss%3Dyes In conclusion, the interaction between the PPVI device and the patient's RVOT is likely to be the crucial factor involved with this undesired event. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272478 Mon, 09 Nov 2009 00:00:00 +0100 3272478 http://www.medworm.com/index.php?rid=3272476&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006009%2Fabstract%3Frss%3Dyes In this study, the governing equations of triphasic mixture theory for soft tissue were linearized and dramatically simplified by using a regular perturbation method and the use of two potential functions. We showed that this new formulation can be used for any axisymmetric problem, such as confined or unconfined compressions, hydraulic perfusion, and indentation. A finite difference numerical program was further developed to calculate the deformational, electrical, and flow behaviors inside the articular cartilage under indentation. The calculated tissue response was highly consistent with the data from indentation experiments (our own and those reported in the literature). It was found that the charged nature of proteoglycans can increase the apparent stiffness of the solid matrix and le... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272476 Mon, 09 Nov 2009 00:00:00 +0100 3272476 http://www.medworm.com/index.php?rid=3204393&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005661%2Fabstract%3Frss%3Dyes In this study, computational fluid dynamics was performed on 4 three-dimensional models of the cerebral ventricular system with the interthalamic adhesion modeled in different locations in the third ventricle. Cerebrospinal fluid (CSF) was modeled as incompressible Newtonian fluid and flow was assumed laminar. The periodic motion of CSF flow as a function of the cardiac cycle starting from diastole was prescribed as the inlet boundary condition at the foramen of Monroe. Results from this study show how the location of the interthalamic adhesion influences the pattern of pressure distribution in the cerebral ventricles. In addition, the highest CSF pressure in the third ventricle can vary by ∼50% depending on the location of the interthalamic adhesion. We suggest that the interthalamic ad... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204393 Mon, 09 Nov 2009 00:00:00 +0100 3204393 http://www.medworm.com/index.php?rid=3204391&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005703%2Fabstract%3Frss%3Dyes Abstract: Sustained mechanical loading of skeletal muscle may result in the development of a severe type of pressure ulcer, referred to as deep tissue injury. Recently it was shown that the diffusion of large molecules (10–150kDa) is impaired during deformation of tissue-engineered skeletal muscle, suggesting a role for impaired diffusion in the aetiology of deep tissue injury. However, the influence of deformation on diffusion of smaller molecules on its aetiology is less clear. This motivated the present study designed to investigate the influence of deformation of skeletal muscle on the diffusion of water, which can be measured with diffusion tensor magnetic resonance imaging (MRI). It could be predicted that this approach will provide valuable information on the diffusion of small mo... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204391 Mon, 09 Nov 2009 00:00:00 +0100 3204391 http://www.medworm.com/index.php?rid=3204375&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005624%2Fabstract%3Frss%3Dyes Abstract: Meniscectomies have been shown to lead to osteoarthritis and the success of meniscal replacements remains questionable. It has been suggested that the success of a meniscal replacement is dependent on several factors, one of which is the secure fixation and firm attachment of the replacement to the tibial plateau at the horn locations. To aid in the development of meniscal replacements, the objectives of the current study were to determine the time-dependent and failure properties of human meniscal attachments. In contrast to the time-dependent tests, during uniaxial failure testing a charge-coupled video camera was used to document the local strain and linear modulus distribution across the surface of the attachments. The lateral attachments were statistically smaller in cross-s... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204375 Mon, 09 Nov 2009 00:00:00 +0100 3204375 http://www.medworm.com/index.php?rid=3120115&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005351%2Fabstract%3Frss%3Dyes Abstract: Models of the adhesion of a population of cells in a plane flow are developed, considering the dilute regime. Cells considered as rigid punctual entities are virtually injected at regular times within a plane channel limited by two fixed planes. The pressure profile is supposed to be triangular (constant gradient), in accordance with the assumptions of a Poiseuille flow. The cell adherence to the channel wall is governed by the balance of forces, accounting for gravity, non-specific physical interactions, such as electrostatic effects (repulsive) and Van der Waals forces (attractive), specific adhesive forces representing the ligand–receptor interactions, and friction between cells and the fluid in the vicinity of the endothelium wall. The spatial distribution of the adhesion m... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120115 Mon, 09 Nov 2009 00:00:00 +0100 3120115 http://www.medworm.com/index.php?rid=3272496&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005867%2Fabstract%3Frss%3Dyes In this study, we report on two techniques for increasing the accuracy of tissue deformation measurements. In the first technique, deformations were tracked in a grid that was photobleached on each tissue sample (). In the second, a numerical technique was implemented that allowed for accurate differentiation of optical displacement measurements by minimizing the propagated experimental error while ensuring that truncation error associated with local averaging of the data remained small. To test their efficacy, we employed these techniques to compare the depth-dependent shear moduli of neonatal bovine and adult human articular cartilage. Using a photobleached grid and numerical optimization to gather and analyze data led to results consistent with those reported previously (; ), but with i... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272496 Fri, 06 Nov 2009 00:00:00 +0100 3272496 http://www.medworm.com/index.php?rid=3272474&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006022%2Fabstract%3Frss%3Dyes The objective of this study was to determine the in vivo tibiofemoral cartilage contact biomechanics during the stance phase of treadmill gait. Eight healthy knees were magnetic resonance (MR) scanned and imaged with a dual fluoroscopic system during gait on a treadmill. The tibia, femur and associated cartilage were constructed from the MR images and combined with the dual fluoroscopic images to determine in vivo cartilage contact deformation during the stance phase of gait. Throughout the stance phase of gait, the magnitude of peak compartmental contact deformation ranged between 7% and 23% of the resting cartilage thickness and occurred at regions with thicker cartilage. Its excursions in the anteroposterior direction were greater in the medial tibiofemoral compartment as compared to th... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272474 Fri, 06 Nov 2009 00:00:00 +0100 3272474 http://www.medworm.com/index.php?rid=3204382&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005582%2Fabstract%3Frss%3Dyes Abstract: In the present study, a probabilistic finite element tool was assessed using an uncemented total hip replacement model. Fully bonded and frictional interfaces were investigated for combinations of three proximal femurs and two implant designs, the Proxima short stem and the IPS hip stem prostheses. The Monte Carlo method was used with two performance indicators: the percentage of bone volume that exceeded specified strain limits and the maximum nodal micromotion. The six degrees of freedom of bone-implant relative position, magnitude of the hip contact force (L), and spatial direction of L were the random variables. The distal portion of the proximal femurs was completely constrained and some of the main muscle forces acting in the hip were applied. The coefficients of the linear... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204382 Fri, 06 Nov 2009 00:00:00 +0100 3204382 http://www.medworm.com/index.php?rid=3204366&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005752%2Fabstract%3Frss%3Dyes Abstract: Instability after slip onset is a key precursor leading to subsequent falls during gait. The purpose of this study was to determine the impact of reactive muscular response from individual lower limb joints on regaining stability control and impeding a novel and unannounced slip during the ensuing single-stance phase. Ten young adults’ resultant moments at three lower limb joints of both limbs, initially derived by an inverse-dynamics approach from empirical data, were optimized to accurately reproduce the original motion before being applied as input to the control variables of their individualized forward-dynamics model. Systematic alteration of the moments of each joint caused corresponding changes in the displacement and velocity of the center of mass (COM) and base of supp... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204366 Fri, 06 Nov 2009 00:00:00 +0100 3204366 http://www.medworm.com/index.php?rid=3120126&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005272%2Fabstract%3Frss%3Dyes Abstract: Micro-separation corresponds to a medial–lateral hip laxity after total hip replacement (THR). This laxity has been shown to generate higher wear rates and a specific pattern of stripe wear caused by edge loading of the head on the rim of the cup. Recently some authors have implicated edge loading as a source of noise generation and in particular squeaking. The goal of this study was to model hip kinematics under the micro-separation regime in a computational simulation of total hip prosthesis including joint laxity and to analyze the vibration frequencies and the potential for noise generation. A three-dimensional computer model of the Leeds II hip simulator was developed using ADAMS® software, simulating a controlled micro-separation during the swing phase of the walking cyc... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120126 Fri, 06 Nov 2009 00:00:00 +0100 3120126 http://www.medworm.com/index.php?rid=3272493&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS002192900900596X%2Fabstract%3Frss%3Dyes Abstract: Osmotic loading is known to modulate chondrocyte (cell) height, width and volume in articular cartilage. It is not known how cartilage architecture, especially the collagen fibril orientation, affects cell shape changes as a result of an osmotic challenge.Intact patellae of New Zealand white rabbits (n=6) were prepared for fluorescence imaging. Patellae were exposed to a hypotonic osmotic shock and cells were imaged before loading and 5–60min after the osmotic challenge. Cell volumes and aspect ratios (height/width) were analyzed. A fibril-reinforced poroelastic swelling model with realistic primary collagen fibril orientations, i.e. horizontal, random and vertical orientation in the superficial, middle and deep zones, respectively and cells in different zones was used to estim... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272493 Thu, 05 Nov 2009 00:00:00 +0100 3272493 http://www.medworm.com/index.php?rid=3272473&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006034%2Fabstract%3Frss%3Dyes Abstract: There is no published data about mask features that impact skin contact pressure during mask ventilation.To investigate the physical factors of skin contact pressure formation.We measured masks with original and reduced air cushion size and recorded contact pressure. We determined cushion contact and mask areas by planimetric measurements.Contact pressures necessary to prevent air leakage during inspiration exceed inspiratory pressure by 1.01±0.41hPa independent of cushion size.Contact area, ventilator pressure and mask area during inspiration and expiration impact contact pressure. Mask contact pressures are higher during expiration. The contact pressure increases with increase in inspiratory pressures independent of the ventilator cycle. During expiration, the contact pressure... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272473 Thu, 05 Nov 2009 00:00:00 +0100 3272473 http://www.medworm.com/index.php?rid=3204374&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS002192900900565X%2Fabstract%3Frss%3Dyes Abstract: The determination of arterial wave speed and the separation of the forward and backward waves have been established using simultaneous measurements of pressure (P) and velocity (U). In this work, we present a novel algorithm for the determination of local wave speed and the separation of waves using the simultaneous measurements of diameter (D) and U. The theoretical basis of this work is the solution of the 1D equations of flow in elastic tubes. A relationship between D and U is derived, from which, local wave speed can be determined; C=±0.5(dU±/dlnD±). When only unidirectional waves are present, this relationship describes a linear relationship between lnD and U. Therefore, constructing a lnDU-loop should result in a straight line in the early part of the cycle when it is mo... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204374 Thu, 05 Nov 2009 00:00:00 +0100 3204374 http://www.medworm.com/index.php?rid=3204372&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005806%2Fabstract%3Frss%3Dyes Abstract: One of the outward signs of the aging process of human skin is the increased appearance of wrinkles on its surface. Clinical studies show that the increased frequency of wrinkles with age may be attributed to changes in the composition of the various layers of skin, leading to a change in mechanical properties. A parameter study was performed on a previously proposed multi-layer finite element model of skin. A region of skin was subject to an in-plane compression, resulting in wrinkling. A number of physical properties of the skin model were changed and the effects these changes had on the size of the subsequent wrinkles were measured. Reducing the moisture content of the stratum corneum by 11% produces wrinkles 25–85% larger. Increasing the dermal collagen fibre density by 67%... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204372 Thu, 05 Nov 2009 00:00:00 +0100 3204372 http://www.medworm.com/index.php?rid=3120133&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005399%2Fabstract%3Frss%3Dyes Abstract: This paper presents a model for determining the path of the instantaneous helical axis (IHA) that optimally represents human planar motions with one functional degree of freedom (fDOF). A human movement is said to have one fDOF when all degrees of freedom (DOFs) are coordinated such that all the kinematic variables can be expressed, across movement repetitions, as functions of only one independent DOF, except for a small natural intercycle variability quantified as lower than a prespecified value. The concept of fDOF allows taking into account that, due to motor coordination, human movements are executed in a repeatable manner. Our method uses the measurement of several repetitions of a given movement to obtain the optimal average IHA path. The starting point is a change of varia... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120133 Thu, 05 Nov 2009 00:00:00 +0100 3120133 http://www.medworm.com/index.php?rid=3084365&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009003819%2Fabstract%3Frss%3Dyes 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, particularly 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 (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3084365 Thu, 05 Nov 2009 00:00:00 +0100 3084365 http://www.medworm.com/index.php?rid=3272498&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005855%2Fabstract%3Frss%3Dyes Thank you for the opportunity to respond to comments by Drs. Fangsen Cui and Yongwei Zhang regarding our recent study (). I appreciate their thoughtful comments and hope this response would encourage additional discussion regarding artery buckling. The following are my responses to the issues raised by Drs. Cui and Zhang (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272498 Wed, 04 Nov 2009 00:00:00 +0100 3272498 http://www.medworm.com/index.php?rid=3204376&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005740%2Fabstract%3Frss%3Dyes Abstract: The success of cell-based tissue engineering approaches in restoring biological function will be facilitated by a comprehensive fundamental knowledge of the temporal evolution of the structure and properties of the newly synthesized matrix. Here, we quantify the dynamic oscillatory mechanical behavior of the engineered matrix associated with individual chondrocytes cultured in vitro for up to 28 days in alginate scaffolds. The magnitude of the complex modulus (|E*|) and phase shift (δ) were measured in culture medium using Atomic Force Microscopy (AFM)-based nanoindentation in response to an imposed oscillatory deformation (amplitude ∼5nm) as a function of frequency (f=1–316Hz), probe tip geometry (2.5μm radius sphere and 50nm radius square pyramid), and in the absence and ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204376 Wed, 04 Nov 2009 00:00:00 +0100 3204376 http://www.medworm.com/index.php?rid=3204367&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005831%2Fabstract%3Frss%3Dyes Abstract: The aim of this work is to specify which model of turbulence is the most adapted in order to predict the drag forces that a swimmer encounters during his movement in the fluid environment. For this, a Computational Fluid Dynamics (CFD) analysis has been undertaken with a commercial CFD code (Fluent®). The problem was modelled as 3D and in steady hydrodynamic state. The 3D geometry of the swimmer was created by means of a complete laser scanning of the swimmer’s body contour. Two turbulence models were tested, namely the standard k–ε model with a specific treatment of the fluid flow area near the swimmer’s body contour, and the standard k–ω model. The comparison of numerical results with experimental measurements of drag forces shows that the standard k–ω model accur... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204367 Wed, 04 Nov 2009 00:00:00 +0100 3204367 http://www.medworm.com/index.php?rid=3204371&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005776%2Fabstract%3Frss%3Dyes Abstract: 3D finite element models of human lumbar functional spinal units (FSU) were used for numerical analysis of weightbath hydrotraction therapy (WHT) applied for treating degenerative diseases of the lumbar spine. Five grades of age-related degeneration were modeled by material properties. Tensile material parameters of discs were obtained by parameter identification based on in vivo measured elongations of lumbar segments during regular WHT, compressive material constants were obtained from the literature. It has been proved numerically that young adults of 40–45 years have the most deformable and vulnerable discs, while the stability of segments increases with further aging. The reasons were found by analyzing the separated contrasting effects of decreasing incompressibility and ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204371 Tue, 03 Nov 2009 00:00:00 +0100 3204371 http://www.medworm.com/index.php?rid=3120123&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005314%2Fabstract%3Frss%3Dyes Abstract: The focus of the current work was to study how the geometric design of a single barbed monofilament suture effects its biomechanical behavior. Different cut angles and cut depths of barbs were prepared and tested in vitro for their tensile and tissue anchoring properties by means of a novel suture/tissue pullout test. Experiments were also performed using bovine tendon and porcine skin tissues. The experimental results revealed that since tendon tissue has a higher modulus than skin it needs a more rigid barb to penetrate and anchor the surrounding tissue. A cut angle of 150° and a cut depth of 0.18mm are therefore recommended. On the other hand, for the softer skin tissue, a cut angle of 170° and a cut depth of 0.18mm provides a more flexible barb that gives superior skin tiss... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120123 Tue, 03 Nov 2009 00:00:00 +0100 3120123 http://www.medworm.com/index.php?rid=3120111&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005430%2Fabstract%3Frss%3Dyes This study examines the effects of popular clamps on vessel wall. Models of the aorta and clamp were created in Computer Assisted Design and Finite Element Analysis packages. The vessel wall was considered as a non-linear anisotropic material while the fluid was simulated as Newtonian with pulsatile flow. The clamp was applied through displacement time function. Fully coupled two-way solid–fluid interaction models were developed. It was found that the clamp design significantly affected the stresses in vessel wall. The clamp with a protrusion feature increased the overall Von Mises stress by about 60% and the compressive stress by more than 200%. Interestingly, when the protrusion clamp was applied, the Von Mises stress at the lumen (endothelium) side of artery wall was about twice that ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120111 Tue, 03 Nov 2009 00:00:00 +0100 3120111 http://www.medworm.com/index.php?rid=3120107&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005478%2Fabstract%3Frss%3Dyes Abstract: A previously developed mass-spring-damper model of the human body is improved in this paper, taking muscle activity into account. In the improved model, a nonlinear controller mimics the functionality of the Central Nervous System (CNS) in tuning the mechanical properties of the soft-tissue package. Two physiological hypotheses are used to determine the control strategies that are used by the controller. The first hypothesis (constant-force hypothesis) postulates that the CNS uses muscle tuning to keep the ground reaction force (GRF) constant regardless of shoe hardness, wherever possible. It is shown that the constant-force hypothesis can explain the existing contradiction about the effects of shoe hardness on the GRF during running. This contradiction is emerged from the differ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120107 Tue, 03 Nov 2009 00:00:00 +0100 3120107 http://www.medworm.com/index.php?rid=2950243&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009006137%2Fabstract%3Frss%3Dyes (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=2950243 Mon, 02 Nov 2009 16:11:55 +0100 2950243 http://www.medworm.com/index.php?rid=3272497&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005843%2Fabstract%3Frss%3Dyes We have read the recent article “A biomechanical model of artery buckling” () with great interest. In the paper, the buckling due to lumen pressure was studied and the critical pressure is derived for different boundary conditions based on linear material models. Unfortunately, one of the equations derived was not accurate. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3272497 Mon, 02 Nov 2009 00:00:00 +0100 3272497 http://www.medworm.com/index.php?rid=3204396&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005715%2Fabstract%3Frss%3Dyes In this study, we evaluated alternative technical markers for the motion analysis of the pelvic segment. Thirteen subjects walked eight times while tri-dimensional kinematics were recorded for one stride of each trial. Five marker sets were evaluated, and we compared the tilt, obliquity, and rotation angles of the pelvis segment: (1) standard: markers at the anterior and posterior superior iliac spines (ASIS and PSIS); (2) markers at the PSIS and at the hip joint centers, HJCs (estimated by a functional method and described with clusters of markers at the thighs); (3) markers at the PSIS and HJCs (estimated by a predictive method and described with clusters of markers at the thighs); (4) markers at the PSIS and HJCs (estimated by a predictive method and described with skin-mounted markers ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204396 Mon, 02 Nov 2009 00:00:00 +0100 3204396 http://www.medworm.com/index.php?rid=3204395&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005557%2Fabstract%3Frss%3Dyes We report on the successful customisation of a commercially available voltage transmitter hooked-up to a strain-gauge rosette, its subcutaneous implantation in rabbits, and the quality of the implant's strain-gauge recordings. Continuous wireless recordings of a completely operational strain-gauge rosette glued to the mandibular surface of a freely moving rabbit could be made up to 33h. The resolution of the system was 1.5 microstrains/bit. The noise in the signal was 4.5 microstrains. To facilitate the automatic counting of bone-strain events in the retrieved data, and to calculate their peak amplitude, a novel approach is presented. The described technique enables the quantification of the daily bone-strain history defining the architecture and composition of bone tissue, and can help to... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204395 Mon, 02 Nov 2009 00:00:00 +0100 3204395 http://www.medworm.com/index.php?rid=3204394&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005636%2Fabstract%3Frss%3Dyes Abstract: Simple video-based methods previously proposed for field research to estimate L5/S1 net moments during real-world manual materials handling rely on polynomial interpolation on the joint angles from key frames extracted from video recordings; however, polynomial interpolations may not converge as the number of interpolation points increases. Therefore, we compared L5/S1 net moments calculated from continuous kinematic measurements to those calculated from both polynomial and cubic spline interpolation on body segments angles during lifting tasks. For small number of interpolation points ( (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204394 Mon, 02 Nov 2009 00:00:00 +0100 3204394 http://www.medworm.com/index.php?rid=3204390&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005648%2Fabstract%3Frss%3Dyes Abstract: A computational model of adaptive bone remodelling is formulated as an optimization problem of instantaneous changes in microstructure that minimize a functional describing the structure quality rate. Microstructure is locally described by a set of scalar geometric parameters. Macroscopic (continuum) elastic properties are assumed orthotropic and expressed as known functions of the geometric parameters. Strain energy is considered the quality measure of bone at given load conditions. The instantaneous rate of geometric parameters is postulated to minimize the rate of the quality functional. An optimization problem is formulated in the continuum description and then it is discretized both in space and time. Numerical simulations predict bone remodelling for femur without and with ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204390 Mon, 02 Nov 2009 00:00:00 +0100 3204390 http://www.medworm.com/index.php?rid=3204385&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005545%2Fabstract%3Frss%3Dyes Abstract: Women with pregnancy-related pelvic girdle pain (PPP), or athletes with groin pain, may have trouble with the active straight leg raise (ASLR), for which a pelvic belt can be beneficial. How the problems emerge, or how the belt works, remains insufficiently understood. We assessed muscle activity during ASLR, and how it changes with a pelvic belt. Healthy nulligravidae (N=17) performed the ASLR, and walked on a treadmill at increasing speeds, without and with a belt. Fine-wire electromyography (EMG) was used to record activity of the mm. psoas, iliacus and transversus abdominis, while other hip and trunk muscles were recorded with surface EMG. In ASLR, all muscles were active. In both tasks, transverse and oblique abdominal muscles were less active with the belt. In ASLR, there w... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204385 Mon, 02 Nov 2009 00:00:00 +0100 3204385 http://www.medworm.com/index.php?rid=3204381&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005594%2Fabstract%3Frss%3Dyes Abstract: The purpose of the present study was to determine how humans adjust leg stiffness over a range of hopping frequencies. Ten male subjects performed in place hopping on two legs, at three frequencies (1.5, 2.2, and 3.0Hz). Leg stiffness, joint stiffness and touchdown joint angles were calculated from kinetic and/or kinematics data. Electromyographic activity (EMG) was recorded from six leg muscles. Leg stiffness increased with an increase in hopping frequency. Hip and knee stiffnesses were significantly greater at 3.0Hz than at 1.5Hz. There was no significant difference in ankle stiffness among the three hopping frequencies. Although there were significant differences in EMG activity among the three hopping frequencies, the largest was the 1.5Hz, followed by the 2.2Hz and then 3.0H... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204381 Mon, 02 Nov 2009 00:00:00 +0100 3204381 http://www.medworm.com/index.php?rid=3204380&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005600%2Fabstract%3Frss%3Dyes Abstract: In this paper we report a study where we use a novel optical tweezers technique to measure the local viscoelastic properties of type I collagen solutions spanning the sol-to-gel transition. We use phase contrast optical microscopy to reveal dense and sparse regions of the rigid fibril networks, and find that the spatial variations in the mechanical properties of the collagen gels closely follow the structural properties. Within the dense phase of the connected network in the gel samples, there are regions that exhibit drastically different viscoelastic properties. Within the sparse regions of the gel samples, no evidence of elasticity is found. In type I collagen gels, we find a high degree of structural inhomogeneity. The inhomogeneity in the structural properties of collagen ge... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204380 Mon, 02 Nov 2009 00:00:00 +0100 3204380 http://www.medworm.com/index.php?rid=3204378&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS002192900900551X%2Fabstract%3Frss%3Dyes Abstract: Despite recent advances in modeling of the human spine, simplifying assumptions are still required to tackle complexities. Such assumptions need to be scrutinized to assess their likely impacts on predictions. A comprehensive comparison of muscle forces and spinal loads estimated by a single-joint (L5–S1) optimisation-assisted EMG-driven (EMGAO) and a multi-joint Kinematics-driven (KD) model of the spine under symmetric (symmetric trunk flexion from neutral upright to maximum forward flexion) and asymmetric (holding a load at various heights in the right hand) activities is carried out. Regardless of the task simulated, the KD model predicted greater activities in extensor muscles as compared to the EMGAO model. Such differences in the symmetric tasks was due mainly to the dist... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204378 Mon, 02 Nov 2009 00:00:00 +0100 3204378 http://www.medworm.com/index.php?rid=3204373&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005673%2Fabstract%3Frss%3Dyes Abstract: History-dependent effects on muscle force development following active changes in length have been measured in a number of experimental studies. However, few muscle models have included these properties or examined their impact on force and power output in dynamic cyclic movements. The goal of this study was to develop and validate a modified Hill-type muscle model that includes shortening-induced force depression and assess its influence on locomotor performance. The magnitude of force depression was defined by empirical relationships based on muscle mechanical work. To validate the model, simulations incorporating force depression were developed to emulate single muscle in situ and whole muscle group leg extension experiments. There was excellent agreement between simulation an... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204373 Mon, 02 Nov 2009 00:00:00 +0100 3204373 http://www.medworm.com/index.php?rid=3204368&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS002192900900582X%2Fabstract%3Frss%3Dyes Abstract: Studies have suggested that the nervous system may adopt a control scheme in which synergistic muscle groups are controlled by common excitation patters, or modules, to simplify the coordination of movement tasks such as walking. A recent computer modeling and simulation study of human walking using experimentally derived modules as the control inputs provided evidence that individual modules are associated with specific biomechanical subtasks, such as generating body support and forward propulsion. The present study tests whether the modules identified during normal walking could produce simulations of walking when the mechanical demands were substantially altered. Walking simulations were generated that emulated human subjects who had their body weight and/or body mass increase... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204368 Mon, 02 Nov 2009 00:00:00 +0100 3204368 http://www.medworm.com/index.php?rid=3204365&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005697%2Fabstract%3Frss%3Dyes Abstract: While there are a growing number of increasingly complex methodologies available to model geometry and material properties of bones, these models still cannot accurately describe physical behaviour of the skeletal system unless the boundary conditions, especially muscular loading, are correct. Available in vivo measurements of muscle forces are mostly highly invasive and offer no practical way to validate the outcome of any computational model that predicts muscle forces. However, muscle forces can be verified indirectly using the fundamental property of living tissue to functional adaptation and finite element (FE) analysis. Even though the mechanisms of the functional adaptation are not fully understood, its result is clearly seen in the shape and inner structure of bones. The ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204365 Mon, 02 Nov 2009 00:00:00 +0100 3204365 http://www.medworm.com/index.php?rid=3120135&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005405%2Fabstract%3Frss%3Dyes It is with great interest that we read the recently published article (June 19th, 2009) ‘Effects of excessive body weight on postural control’ in volume 42, issue 9, pages 1295–1300 of the Journal of Biomechanics. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120135 Mon, 02 Nov 2009 00:00:00 +0100 3120135 http://www.medworm.com/index.php?rid=3120118&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005326%2Fabstract%3Frss%3Dyes Abstract: We investigated the effects of including kinematic constraints in the analysis of knee kinematics from skin markers and compared the result to simultaneously recorded trajectories of bone pin markers during gait of six healthy subjects. The constraint equations that were considered for the knee were spherical and revolute joints, which have been frequently used in musculoskeletal modelling. In the models, the joint centres and joint axes of rotations were optimised from the skin marker trajectories over the trial. It was found that the introduction of kinematic constraints did not reduce the error associated with soft tissue artefacts. The inclusion of a revolute joint constraint showed a statistically significant increase in the mean flexion/extension joint angle error and no st... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120118 Mon, 02 Nov 2009 00:00:00 +0100 3120118 http://www.medworm.com/index.php?rid=3084339&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005296%2Fabstract%3Frss%3Dyes Abstract: Epidemiological data at one time was taken to suggest that chronic vibrations—for example operating vehicles with low-quality seats—contributed to intervertebral disc degeneration and lower back pain. More recent discussions, based in part upon extended twin studies, have cast doubt upon this interpretation, and question how much of the vibration is actually transmitted to the spine during loading. This review summarizes our recent survey of the current state of knowledge. In particular, we note that current studies are lacking a detailed factorial exploration of frequency, amplitude, and duration; this may be the primary cause for inconclusive and/or contradictory studies. It is our conclusion that vibrations are still an important consideration in discogenic back pain, and ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3084339 Mon, 02 Nov 2009 00:00:00 +0100 3084339 http://www.medworm.com/index.php?rid=3204389&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005727%2Fabstract%3Frss%3Dyes In this study, an inverse problem methodology is used which takes into account both features and yields material property estimates that can analyze the healing changes. Six stabilized fractured mouse tibias are obtained at two time points during the most active phase of the healing process, respectively 10 days (n=3), and 14 days (n=3) after fracture. Under the same displacement conditions, the inverse procedure estimations of the callus material properties are generated and compared to other fracture healing metrics. The FEA estimated property is the only metric shown to be statistically significant (p=0.0194) in detecting the changes in the stiffness that occur during the healing time points. In addition, simulation studies regarding sensitivity to initial guess and noise are presented;... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204389 Fri, 30 Oct 2009 00:00:00 +0100 3204389 http://www.medworm.com/index.php?rid=3204387&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005508%2Fabstract%3Frss%3Dyes Abstract: Red blood cell (RBC) aggregation is becoming an important hemorheological parameter, which exhibits a unique temperature dependence. However, further investigation is still required for understanding the temperature-dependent characteristics of hemorheology that includes RBC aggregation. In the present study, blood samples were examined at 3, 10, 20, 30, and 37°C. When the temperature decreases, the whole-blood and plasma viscosities increase, whereas the aggregation indices (AI, M, and b) yield contrary results. Since these contradictory results are known to arise from an increase in the plasma viscosity as the temperature decreases, aggregation indices that were corrected for plasma viscosity were examined. The corrected indices showed mixed results with the variation of the t... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204387 Fri, 30 Oct 2009 00:00:00 +0100 3204387 http://www.medworm.com/index.php?rid=3204384&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005570%2Fabstract%3Frss%3Dyes Abstract: To facilitate the assessment of hip injury risk in frontal motor-vehicle crashes, an injury risk curve that relates peak force transmitted to the hip to the probability of hip fracture was developed by using survival analysis to fit a lognormal distribution to a recently published dataset of hip fracture forces. This distribution was parameterized to account for the effect of subject stature, which was the only subject characteristic found to significantly affect hip fracture force (X2(1)=6.03, p=0.014). The distribution was further parameterized to account for the effects of hip flexion and abduction from a standard driving posture on hip fracture force using relationships between mean hip fracture force and hip flexion/abduction reported in the literature. The resulting paramet... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204384 Fri, 30 Oct 2009 00:00:00 +0100 3204384 http://www.medworm.com/index.php?rid=3204379&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005612%2Fabstract%3Frss%3Dyes Abstract: A thorough understanding of age-related phenomena on the trabecular architecture in the human lumbar spine can help the diagnosis and prognosis of age-related architectural changes, and provide an insight into the corresponding clinical assessments. In this paper we considered the different loading conditions of the young and old lumbar spines mainly caused by disc degeneration and studied the effect of loading alteration on trabecular architecture in lumbar spines. A two-dimensional μFE models with a 40μm pixel resolution were built to represent the full trabecular architecture in the human lumbar spine, and a topology optimization with the aid of finite element method was conducted to numerically investigate the trabecular morphological changes. Topology optimization iterativ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204379 Fri, 30 Oct 2009 00:00:00 +0100 3204379 http://www.medworm.com/index.php?rid=3120136&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005417%2Fabstract%3Frss%3Dyes Given this opportunity, I would like to clarify a couple of points that may be attributed to disagreements between statements in our paper and statements in the letter by Dr. Handrigan and colleagues. First of all, I think we differ in understanding postural balance concept. According to my knowledge, the postural stability defines ability of the upright-stance control to persist and to remain qualitatively unchanged in response to a disturbances that attempt or temporarily displace the equilibrium. Generally, the upright posture is stable if, when perturbed, it returns to its original state; the more quickly it returns, the more stable it is (). The both aforementioned features of stable posture: resistance to perturbations and efficient equilibrium recovery, are dependent on numerous mor... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120136 Fri, 30 Oct 2009 00:00:00 +0100 3120136 http://www.medworm.com/index.php?rid=3120132&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS002192900900548X%2Fabstract%3Frss%3Dyes This study showed that there are significant differences between the five functional methods. The smallest distance between the estimated joint centre and the centre of the humeral head was obtained with the method of . (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120132 Fri, 30 Oct 2009 00:00:00 +0100 3120132 http://www.medworm.com/index.php?rid=3120117&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005338%2Fabstract%3Frss%3Dyes Abstract: Large-conductance Ca2+-activated K+ (BKCa) channels play a critical role in regulating the cellular excitability in response to change in blood flow. It has been demonstrated that vascular BKCa channel currents in both humans and rats are increased after exercise training. This up-regulation of the BKCa channel activity in arterial myocytes may represent a cellular compensatory mechanism of limiting vascular reactivity to exercise training. However, the underlying mechanisms are not fully understood. In the present study, we examined the single channel activities and kinetics of the BKCa channels in rat thoracic aorta smooth muscle cells. We showed that exercise training significantly increased the open probability (Po), decreased the mean closed time and increased the mean open ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120117 Fri, 30 Oct 2009 00:00:00 +0100 3120117 http://www.medworm.com/index.php?rid=3120116&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS002192900900534X%2Fabstract%3Frss%3Dyes Abstract: Shape plays an important role in determining the biomechanical response of a structure. Specimen-specific finite element (FE) models have been developed to capture the details of the shape of biological structures and predict their biomechanics. Shape, however, can vary considerably across individuals or change due to aging or disease, and analysis of the sensitivity of specimen-specific models to these variations has proven challenging. An alternative to specimen-specific representation has been to develop generic models with simplified geometries whose shape is relatively easy to parameterize, and can therefore be readily used in sensitivity studies. Despite many successful applications, generic models are limited in that they cannot make predictions for individual specimens.We... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120116 Fri, 30 Oct 2009 00:00:00 +0100 3120116 http://www.medworm.com/index.php?rid=3120113&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005442%2Fabstract%3Frss%3Dyes Abstract: Patellofemoral pain is a common knee disorder with a multi-factorial etiology related to abnormal patellar tracking. Our hypothesis was that the pattern of three-dimensional rotation and translation of the patella induced by selective activation of individual quadriceps components would differ between subjects with patellofemoral pain and healthy subjects. Nine female subjects with patellofemoral pain and seven healthy female subjects underwent electrical stimulation to selectively activate individual quadriceps components (vastus medialis obliquus, VMO; vastus medialis lateralis, VML; vastus lateralis, VL) with the knee at 0° and 20° flexion, while three-dimensional patellar tracking was recorded. Normalized direction of rotation and direction of translation characterized the ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120113 Fri, 30 Oct 2009 00:00:00 +0100 3120113 http://www.medworm.com/index.php?rid=3120112&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005387%2Fabstract%3Frss%3Dyes Abstract: The purpose of this study was to investigate whether using a finite-element (FE) mesh composed entirely of hexahedral elements to model cortical and trabecular bone (all-hex model) would provide more accurate simulations than those with variable thickness shell elements for cortical bone and hexahedral elements for trabecular bone (hex–shell model) in the modeling human ribs. First, quasi-static non-injurious and dynamic injurious experiments were performed using the second, fourth, and tenth human thoracic ribs to record the structural behavior and fracture tolerance of individual ribs under anterior–posterior bending loads. Then, all-hex and hex–shell FE models for the three ribs were developed using an octree-based and multi-block hex meshing approach, respectively. Mate... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120112 Fri, 30 Oct 2009 00:00:00 +0100 3120112 http://www.medworm.com/index.php?rid=3120110&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005429%2Fabstract%3Frss%3Dyes Abstract: In animal cells, blebs are smooth, quasi-hemispherical protrusions of the plasma membrane that form when a section of the membrane detaches from the underlying actin cytoskeleton and is inflated by flowing cytosol. The mechanics behind this common cellular activity are not yet clear. As a first step in the development of a full computational framework, we present a numerical model of overall cell behavior based upon the interaction between a background Newtonian-fluid cytosol and elastic structures modeling the membrane and filaments. The detailed micromechanics of the cytoskeletal network are the subject of future work. Here, the myosin-driven contraction of the actin network is modeled through stressed elastic filaments. Quantitative models of cytoskeletal micromechanics and bi... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120110 Fri, 30 Oct 2009 00:00:00 +0100 3120110 http://www.medworm.com/index.php?rid=3120109&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005491%2Fabstract%3Frss%3Dyes Abstract: To guide development of robotic lower limb exoskeletons, it is necessary to understand how humans adapt to powered assistance. The purposes of this study were to quantify joint moments while healthy subjects adapted to a robotic ankle exoskeleton and to determine if the period of motor adaptation is dependent on the magnitude of robotic assistance. The pneumatically powered ankle exoskeleton provided plantar flexor torque controlled by the wearer's soleus electromyography (EMG). Eleven naïve individuals completed two 30-min sessions walking on a split-belt instrumented treadmill at 1.25m/s while wearing the ankle exoskeleton. After two sessions of practice, subjects reduced their soleus EMG activation by ∼36% and walked with total ankle moment patterns similar to their unassis... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120109 Fri, 30 Oct 2009 00:00:00 +0100 3120109 http://www.medworm.com/index.php?rid=3120108&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005466%2Fabstract%3Frss%3Dyes The objective of this paper is to develop an analytical framework to representing the ankle–foot kinematics by modelling the foot as a rollover rocker, which cannot only be used as a generic tool for general gait simulation but also allows for case-specific modelling if required. Previously, the rollover models used in gait simulation have often been based on specific functions that have usually been of a simple form. In contrast, the analytical model described here is in a general form that the effective foot rollover shape can be represented by any polar function ρ=ρ(φ). Furthermore, a normalized generic foot rollover model has been established based on a normative foot rollover shape dataset of 12 normal healthy subjects. To evaluate model accuracy, the predicted ankle motions and ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120108 Fri, 30 Oct 2009 00:00:00 +0100 3120108 http://www.medworm.com/index.php?rid=3204369&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005818%2Fabstract%3Frss%3Dyes Abstract: Gelatin is a popular tissue simulant used in biomedical applications. The uniaxial compressive stress–strain response of gelatin was determined at a range of strain rates. In the quasistatic regime, gelatin strength remained relatively constant. With increase in loading rate, the compressive strength increased from 3kPa at a strain rate of around 0.0013/s to 6MPa at a strain rate of around 3200/s. This dramatic increase in strength of gelatin at high rates is attributed to its shear-thickening behavior and is argued on the basis of hydrocluster formation mechanism and differences in internal energy dissipation mechanism under static and dynamic loading. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204369 Wed, 28 Oct 2009 00:00:00 +0100 3204369 http://www.medworm.com/index.php?rid=3120128&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005260%2Fabstract%3Frss%3Dyes Abstract: Rapid accelerations during running are crucial for the performance in a lot of sports. While high propulsive forces are beneficial to forward acceleration, vertical forces have to be small to attain high stride frequencies. However, propulsive and vertical force components cannot be altered independently, because the resultant force vector affects the angular momentum of the body. Therefore we hypothesized that propulsive forces in accelerated running mainly depend on body position regardless of performance level. In our cross-sectional study 28 male and 13 female physical education students performed submaximal and maximal accelerations. Ground reaction forces and whole body kinematics were recorded. Higher accelerations were generated by lower, but more forward oriented forces.... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120128 Wed, 28 Oct 2009 00:00:00 +0100 3120128 http://www.medworm.com/index.php?rid=3120114&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005363%2Fabstract%3Frss%3Dyes Abstract: Anterior tibial loading is a major factor involved in the anterior cruciate ligament (ACL) injury mechanism during ski impact landing. We sought to investigate the direct contribution of axial impact compressive load to anterior tibial load during simulated ski landing impact of intact knee joints without quadriceps activation. Twelve porcine knee specimens were procured. Four specimens were used as non-impact control while the remaining eight were mounted onto a material-testing system at 70° flexion and subjected to simulated landing impact, which was successively repeated with incremental actuator displacement. Four specimens from the impacted group underwent pre-impact MRI for tibial plateau angle measurements while the other four were subjected to histology and microCT for ... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120114 Wed, 28 Oct 2009 00:00:00 +0100 3120114 http://www.medworm.com/index.php?rid=3204397&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005521%2Fabstract%3Frss%3Dyes The authors regret that the work of was unwittingly ignored and not mentioned in the text. The stiffness estimation method described in this previous paper and method D of our article differ only in minor details, as the first calculation relies on the horizontal velocity and the second on the angle of attack. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3204397 Mon, 26 Oct 2009 00:00:00 +0100 3204397 http://www.medworm.com/index.php?rid=3120125&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005302%2Fabstract%3Frss%3Dyes Abstract: The goal of this study was to characterize the passive elastic behaviour of muscle and tendon tissues of rat tibialis anterior. For that purpose, tissue samples from 3 month old female Wistar rats were mechanically tested in vitro. Moreover, an in vivo device was developed to measure the muscle–tendon unit response to increasing load.Mechanical tests, consisting of uniaxial loading along the longitudinal axis of tendon and muscle strips, revealed the nonlinear mechanical behaviour of these tissues.A material model was formulated and its parameters fit to the experimental data using the Levenberg–Marquardt optimization algorithm. The fit goodness was assessed and values close to 1 and very low values were obtained.The passive behaviour of a future finite element model of a mus... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120125 Mon, 26 Oct 2009 00:00:00 +0100 3120125 http://www.medworm.com/index.php?rid=3120131&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005259%2Fabstract%3Frss%3Dyes This study investigated the extent to which co-contraction is beneficial or necessary in drop landings, using both experimental data and computer simulations. High speed video and force recordings were made of an elite martial artist performing drop landings onto a force plate from heights of 1.2, 1.5 and 1.8m. Matching simulations of these landings were produced using a planar 8-segment torque-driven subject-specific computer simulation model. It was found that there was substantial co-activation of joint flexor and extensor torques at touchdown in all three landings. Optimisations were carried out to determine whether landings could be effected without any co-contraction at touchdown. The model was not capable of landing from higher than 1.05m with no initial flexor or extensor activatio... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120131 Mon, 19 Oct 2009 00:00:00 +0100 3120131 http://www.medworm.com/index.php?rid=3120130&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005247%2Fabstract%3Frss%3Dyes Abstract: In this paper the mechanical response of soft collagenous tissues with regular fiber arrangement (RSCTs) is described by means of a nanoscale model and a two-step micro–macro homogenization technique. The non-linear collagen constitutive behavior is modeled at the nanoscale by a novel approach accounting for entropic mechanisms as well as stretching effects occurring in collagen molecules. Crimped fibers are reduced to equivalent straight ones at the microscale and the constitutive response of RSCTs at the macroscale is formulated by homogenizing a fiber reinforced material. This approach has been applied to different RSCTs (tendon, periodontal ligament and aortic media), resulting effective and accurate as proved by the excellent agreement with available experimental data. The... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3120130 Mon, 19 Oct 2009 00:00:00 +0100 3120130 http://www.medworm.com/index.php?rid=3084351&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009004588%2Fabstract%3Frss%3Dyes Abstract: Titanium cermet was successfully synthesized and formed a thin gradient titanium carbide coating on the surface of Ti6Al4V alloy by using a novel sequential carburization under high temperature, while the titanium cermet femoral head was produced. The titanium cermet phase and surface topography were characterized with X-ray diffraction (XRD) and backscattered electron imaging (BSE). And then the wear behavior of titanium cermet femoral head was investigated by using CUMT II artificial joint hip simulator. The surface characterization indicates that carbon effectively diffused into the titanium alloys and formed a hard TiC layer on the Ti6Al4V alloys surface with a micro-porous structure. The artificial hip joint experimental results show that titanium cermet femoral head could n... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3084351 Mon, 19 Oct 2009 00:00:00 +0100 3084351 http://www.medworm.com/index.php?rid=3114454&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005107%2Fabstract%3Frss%3Dyes Discussion centers around the continually evolving cellular and microstructural anatomy of the nucleus pulposus (NP) and the annulus fibrosus (AF) in response to complex stresses generated in support of axial load and spinal motion. Particular attention has been given to cells from the immature NP and the interlamellar AF, and assessment of their potential mechanobiologic contributions to the health and function of the IVD. In addition, several innovative approaches that have been brought to bear on studying the interplay between disc cells and their micromechanical environment are discussed. Techniques for “engineering” cellular function and technologies for fabricating more structurally defined biomaterial scaffolds have recently been employed in disc research. Such tools can be used... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3114454 Thu, 15 Oct 2009 00:00:00 +0100 3114454 http://www.medworm.com/index.php?rid=3114453&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005090%2Fabstract%3Frss%3Dyes Abstract: In this review, we outline seminal and recent work highlighting the potential of mesenchymal stem cells (MSCs) in producing cartilage-like tissue equivalents. Specific focus is placed on the mechanical properties of engineered MSC-based cartilage and how these properties relate to that of engineered cartilage based on primary chondrocytes and to native tissue properties. We discuss current limitations and/or concerns that must be addressed for the clinical realization of MSC-based cartilage therapeutics, and provide some insight into potential underpinnings for the observed deviations from chondrocyte-based engineered constructs. We posit that these differences reveal specific deficits in terms of our description of chondrogenesis, and suggest that new benchmarks must be develope... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3114453 Thu, 15 Oct 2009 00:00:00 +0100 3114453 http://www.medworm.com/index.php?rid=3114457&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005132%2Fabstract%3Frss%3Dyes Abstract: Collagen is the main load bearing protein in many soft tissues, and in cardiovascular tissues in particular. In many tissues collagen has a specific architecture that is crucial for the biomechanical function of the tissue. Typical examples are the hammock-shaped collagen architecture in heart valves and a helical pattern in arteries. One of the objectives in cardiovascular tissue engineering is the reconstitution of this architecture. It is hypothesized that the architecture is mediated by mechanical stimulation. Computational models were developed to predict the mechanoregulation of the collagen architecture. This review recapitulates the key modeling assumptions and results achieved to date. (Source: Journal of Biomechanics) Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3114457 Mon, 12 Oct 2009 00:00:00 +0100 3114457 http://www.medworm.com/index.php?rid=3114449&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005053%2Fabstract%3Frss%3Dyes Abstract: Cardiac cells are under constant, self-generated mechanical stress which can affect the differentiation of stem cells into cardiac myocytes, the development of differentiated cells and the maturation of cells in neonatal mammals. In this article, the effects of direct stretch, electrically induced beating and substrate elasticity on the behavior and development of cardiomyocytes are reviewed, with particular emphasis on the effects of substrate stiffness on cardiomyocyte maturation. In order to relate these observations to in vivo mechanical conditions, we isolated the left ventricle of Black Swiss mice from embryonic day 13.5 through post-natal day 14 and measured the elastic modulus of the epicardium using atomic force microscope indentation. We found that the elastic modulus o... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3114449 Mon, 12 Oct 2009 00:00:00 +0100 3114449 http://www.medworm.com/index.php?rid=3114443&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009004990%2Fabstract%3Frss%3Dyes Abstract: Mechanical force modulates a wide array of cell physiological processes. Cells sense and respond to mechanical stimuli using a hierarchy of structural complexes spanning multiple length scales, including force-sensitive molecules and cytoskeletal networks. Understanding mechanotransduction, i.e., the process by which cells convert mechanical inputs into biochemical signals, has required the development of novel biophysical tools that allow for probing of cellular and subcellular components at requisite time, length, and force scales and technologies that track the spatio-temporal dynamics of relevant biomolecules. In this review, we begin by discussing the underlying principles and recent applications of atomic force microscopy, magnetic twisting cytometry, and traction force mic... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3114443 Mon, 12 Oct 2009 00:00:00 +0100 3114443 http://www.medworm.com/index.php?rid=3114452&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005089%2Fabstract%3Frss%3Dyes Abstract: Mechanobiology aims to discover how the mechanical environment affects the biological activity of cells and how cells’ ability to sense these mechanical cues is converted into elicited cellular responses. Musculoskeletal mechanobiology is of particular interest given the high mechanical loads that musculoskeletal tissues experience on a daily basis. How do cells within these mechanically active tissues interpret external loads imposed on their extracellular environment, and, how are cell–substrate interactions converted into biochemical signals? This review outlines many of the main mechanotransduction mechanisms known to date, and describes recent literature examining effects of both external forces and cell–substrate interactions on musculoskeletal cells. Whether via appl... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3114452 Fri, 09 Oct 2009 00:00:00 +0100 3114452 http://www.medworm.com/index.php?rid=3114451&cid=s_38490_61_f&fid=38490&url=http%3A%2F%2Fwww.jbiomech.com%2Farticle%2FPIIS0021929009005077%2Fabstract%3Frss%3Dyes Abstract: Bone tissue forms and is remodeled in response to the mechanical forces that it experiences, a phenomenon described by Wolff's Law. Mechanically induced formation and adaptation of bone tissue is mediated by bone cells that sense and respond to local mechanical cues. In this review, the forces experienced by bone cells, the mechanotransduction pathways involved, and the responses elicited are considered. Particular attention is given to two cell types that have emerged as key players in bone mechanobiology: osteocytes, the putative primary mechanosensors in intact bone; and osteoprogenitors, the cells responsible for bone formation and recently implicated in ectopic calcification of cardiovascular tissues. Mechanoregulation of bone involves a complex interplay between these cells... Journal of Biomechanics journals http://www.medworm.com/rss/comments.php?id=3114451 Fri, 09 Oct 2009 00:00:00 +0100 3114451