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- J Biomech 43(3):IFC (2010)
- Principles of determination and verification of muscle forces in the human musculoskeletal system: Muscle forces to minimise bending stress
Sverdlova NS Witzel U - J Biomech 43(3):387-396 (2010)
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 FE method provides a precise tool for analysis of the stress/strain distribution in the bone under given loading conditions. The present work sets principles for the determination of the muscle! forces on the basis of the widely accepted view that biological systems are optimized light-weight structures with minimised amount of unloaded/underloaded material and hence evenly distributed loading throughout the structure. Bending loading of bones is avoided/compensated in bones under physiological loading. Thus, bending minimisation provides the basis for the determination of the musculoskeletal system loading. As a result of our approach, the muscle forces for a human femur during normal gait and sitting down (peak hip joint force) are obtained such that the bone is loaded predominantly in compression and the stress distribution in proximal and diaphyseal femur corresponds to the material distribution in bone. - Role of individual lower limb joints in reactive stability control following a novel slip in gait
Yang F Pai YC - J Biomech 43(3):397-404 (2010)
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 support (BOS) (i.e. their state variables, xCOM, , xBOS, ), and in the COM stability. The model simulation revealed that these joints had little influence on but had substantial impact on reducti! on, leading to improve the COM stability, mostly from knee flexors, followed by hip extensors, of the slipping limb. Per unit reactive increase in normalized knee flexor or hip extensor moments and per unit reactive reduction in commonly observed plantar–flexor moments could lead to as much as 57.72±10.46 or 22.33±5.55 and 13.09±2.27 units of reduction in normalized , respectively. In contrast, such influence was negligible from the swing limb during this period, irrespective of individual variability. - Turbulence model choice for the calculation of drag forces when using the CFD method
Zaïdi H Fohanno S Taïar R Polidori G - J Biomech 43(3):405-411 (2010)
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 accurately predicts the drag forces while the standard k–ε model underestimates their values. The standard k–ω model also enabled to capture the vortex structures developing at the swimmer's! back and buttocks in underwater swimming; the same vortices had been visualized by flow visualization experiments carried out at the INSEP (National Institute for Sport and Physical Education in Paris) with the French national swimming team. - Modular control of human walking: Adaptations to altered mechanical demands
McGowan CP Neptune RR Clark DJ Kautz SA - J Biomech 43(3):412-419 (2010)
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 increased and decreased by 25%. By scaling the magnitude of five module patterns, the simulations could emulate the subjects' response to each condition by simply scaling the mechanical output from m! odules associated with specific biomechanical subtasks. Specifically, the modules associated with providing body support increased (decreased) their contribution to the vertical ground reaction force when body weight was increased (decreased) and the module associated with providing forward propulsion increased its contribution to the positive anterior–posterior ground reaction force and positive trunk power when the body mass was increased. The modules that contribute to controlling leg swing were unaffected by the perturbations. These results support the idea that the nervous system may use a modular control strategy and that flexible modulation of module recruitment intensity may be sufficient to meet large changes in mechanical demand. - Compressive strain rate sensitivity of ballistic gelatin
Kwon J Subhash G - J Biomech 43(3):420-425 (2010)
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 3 kPa at a strain rate of around 0.0013/s to 6 MPa 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. - A non-invasive acoustic and vibration analysis technique for evaluation of hip joint conditions
Glaser D Komistek RD Cates HE Mahfouz MR - J Biomech 43(3):426-432 (2010)
The performance evaluation of THA outcome is difficult and surgeons often use invasive methods to investigate effectiveness. A non-invasive acoustic and vibration analysis technique has recently been developed for more-in-depth evaluation of in vivo hip conditions. Gait kinematics, corresponding vibration and sound measurement of five THA subjects were analyzed post-operatively using video-fluoroscopy, sound and accelerometer measurements while walking on a treadmill. The sound sensor and a pair of tri-axial accelerometers, externally attached to the pelvic and femoral bone prominences, detected frequencies that are propagated through the femoral head and acetabular cup interactions. A data acquisition system was used to amplify the signal and filter out noise generated by undesired frequencies. In vivo kinematics and femoral head sliding quantified using video fluoroscopy were correlated to the sound and acceleration measurements. Distinct variations between the different subjects were identified. A correlation of sound and acceleration impulses with separation has been achieved. Although, in vivo sounds are quite variable in nature and all correlated well with the visual images. This is the first study to document and correlate visual and audible effects of THA under in-vivo conditions. 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. - Finite element analysis of weightbath hydrotraction treatment of degenerated lumbar spine segments in elastic phase
Kurutz M Oroszváry L - J Biomech 43(3):433-441 (2010)
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 increasing hardening of nucleus, yielding non-monotonous functions of stresses and deformations in terms of aging and degeneration. WHT consists of indirect and direct traction phases. Discs sh! ow a bilinear material behaviour with higher resistance in indirect and smaller in direct traction phase. Consequently, although the direct traction load is only 6% of the indirect one, direct traction deformations are 15–90% of the indirect ones, depending on the grade of degeneration. Moreover, the ratio of direct stress relaxation remains equally about 6–8% only. Consequently, direct traction controlled by extra lead weights influences mostly the deformations being responsible for the nerve release; while the stress relaxation is influenced mainly by the indirect traction load coming from the removal of the compressive body weight and muscle forces in the water. A mildly degenerated disc in WHT shows 0.15 mm direct, 0.45 mm indirect and 0.6 mm total extension; 0.2 mm direct, 0.6 mm indirect and 0.8 mm total posterior contraction. A severely degenerated disc exhibits 0.05 mm direct, 0.05 mm indirect and 0.1 mm total extension; 0.05 mm direct, 0.25 mm indirect and 0.3 ! mm total posterior contraction. These deformations are related! to the instant elastic phase of WHT that are doubled during the creep period of the treatment. The beneficial clinical impacts of WHT are still evident even 3 months later. - Simulating the wrinkling and aging of skin with a multi-layer finite element model
Flynn C McCormack BA - J Biomech 43(3):442-448 (2010)
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%, results in wrinkles, which are 25–50% larger. A reduction and change in the pre-stress distribution in the skin model, which represents the natural tension and relaxed skin tension lines in! real skin, also influences the wrinkle height in a similar manner to real aging skin. Typically, there can be up to a 100% increase in the height of wrinkles as skin ages. This model would be of benefit in the development of cosmetic moisturisers and plastic-surgery techniques to reduce the appearance of aging. - A phenomenological model and validation of shortening-induced force depression during muscle contractions
McGowan CP Neptune RR Herzog W - J Biomech 43(3):449-454 (2010)
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 and experimental values, with in situ force patterns closely matching the experimental data (average RMS error <1.5 N) and force depression in the simulated leg extension exercise being similar i! n magnitude to experimental values (6.0% vs. 6.5%, respectively). To examine the influence of force depression on locomotor performance, simulations of maximum power pedaling with and without force depression were generated. Force depression decreased maximum crank power by 20–40%, depending on the relationship between force depression and muscle work used. These results indicate that force depression has the potential to substantially influence muscle power output in dynamic cyclic movements. However, to fully understand the impact of this phenomenon on human movement, more research is needed to characterize the relationship between force depression and mechanical work in large muscles with different morphologies. - Determination of wave speed and wave separation in the arteries using diameter and velocity
Feng J Khir AW - J Biomech 43(3):455-462 (2010)
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±/d ln D±). When only unidirectional waves are present, this relationship describes a linear relationship between ln D and U. Therefore, constructing a ln DU-loop should result in a straight line in the early part of the cycle when it is most probable that waves are running in the forward direction. Using this knowledge of wave speed, it is also possible to derive a set of equations to separate the forward and backward waves ! from the measured D and U waveforms. Once the forward and backward waveforms of D and U are established, we can calculate the energy carried by the forward and backward waves, in a similar way to that of wave intensity analysis. In this paper, we test the new algorithm in vitro and present results from data measured in the carotid artery of human and the ascending aorta of canine. We conclude that the new technique can be reproduced in vitro, and in different vessels of different species, in vivo. The new algorithm is easy to use to determine wave speed and separate D and U waveforms into their forward and backward directions. Using this technique has the merits of utilising noninvasive measurements, which would be useful in the clinical setting. - Geometry, time-dependent and failure properties of human meniscal attachments
Hauch KN Villegas DF Haut Donahue TL - J Biomech 43(3):463-468 (2010)
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-sectional area and longer than the medial attachments. The anterior attachments were statistically longer and had a smaller cross-sectional area than the posterior attachments. From the stress r! elaxation tests, the load and stress relaxation rates of the medial anterior attachment were statistically greater than the medial posterior attachment. There were no significant differences in the creep, structural properties or the ultimate stress between the different attachments. Ultimate strain varied between attachments, as well as along the length of the attachment. Ultimate strain in the meniscus region (10.4±6.9%) and mid-substance region (12.7±16.4%) was smaller than the bony insertion region (32.2±21.5%). The lateral and anterior attachments were also found to have statistically greater strain than the medial and posterior attachments, respectively. The linear modulus was statistically weaker in the bony insertion region (69.7±33.7 MPa) compared to the meniscus region (153±123 MPa) and mid-substance region (195±121 MPa). Overall the anterior attachments (169±130 MPa) were also found to be statistically stronger than the posterior attachments (90.8±64.9 MP! a). These results can be used to help design tissue-engineered! replacement menisci and their insertions and show the differences in material properties between attachments, as well as within an attachment. - Dynamic mechanical properties of the tissue-engineered matrix associated with individual chondrocytes
Lee B Han L Frank EH Chubinskaya S Ortiz C Grodzinsky AJ - J Biomech 43(3):469-476 (2010)
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 5 nm) as a function of frequency (f=1–316 Hz), probe tip geometry (2.5 μm radius sphere and 50 nm radius square pyramid), and in the absence and presence of growth factors (GF, insulin growth factor-1, IGF-1, and osteogenic protein-1, OP-1). |E*| for all conditions increased nonlinearly with frequency dependence approximately f1/2 and ! ranged between 1 and 25 kPa. This result, along with theoretical calculations of the characteristic poroelastic relaxation frequency, fp, (50–90 Hz) suggested that this time-dependent behavior was governed primarily by fluid flow-dependent poroelasticity, rather than flow-independent viscoelastic processes associated with the solid matrix. |E*(f)| increased, (f) decreased, and the hydraulic permeability, k, decreased with time in culture and with growth factor treatment. This trend of a more elastic-like response was thought to be associated with increased macromolecular biosynthesis, density, and a more mature matrix structure/organization. - Strain shielding in distal femur after patellofemoral arthroplasty under different activity conditions
Meireles S Completo A António Simões J Flores P - J Biomech 43(3):477-484 (2010)
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 strains were measured experimentally with triaxial strain gauges in synthetic femurs before and after patellofemoral arthroplasty for each of the different daily activities. The results showed ! that the patellofemoral arthroplasty in general reduced the strains in the medial and distal regions of the femur when deep bending activity occurred, consequently, strain shielding in these regions, with strain decreases of −72.0% and −67.5% were measured. On the other side, higher values of strain were found in the anterior region after patellofemoral replacement for this activity with an increase of +182.0%. The occurrence of strain shielding seems to be more significant when the angle of knee flexion and applied load increases. Strain shielding and over-loading may have relevant effects on bone remodeling surrounding the patellofemoral implant, suggesting a potential effect of later bone resorption in the medial and distal femur regions in case of regular deep bending activity. - A comparative study of two trunk biomechanical models under symmetric and asymmetric loadings
Arjmand N Gagnon D Plamondon A Shirazi-Adl A Larivière C - J Biomech 43(3):485-491 (2010)
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 distinct approaches to resolve the redundancy while in the asymmetric tasks they were due also to the different methods used to estimate joint moments. Shear and compression forces were generally h! igher in the KD model. Differences in predictions between these modeling approaches varied depending on the task simulated and the joint considered in the single-joint EMGAO model. The EMGAO model should incorporate a multi-joint strategy to satisfy equilibrium at different levels while the KD model should benefit from recorded EMG activities of the antagonistic muscles to supplement input measured kinematics. - Computational study on the effect of loading alteration caused by disc degeneration on the trabecular architecture in human lumbar spine
Jang IG Kim IY - J Biomech 43(3):492-499 (2010)
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 40 μm 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 iteratively distributes material in a design domain producing optimal layout or configuration, and it has been widely and successfully used for the study of bone remodeling. As a result of adaptive re! sponse of bone remodeling due to different loading conditions, we obtained two distinctively different trabecular architectures for the young and old lumbar spines, and we observed a strong correlation between our numerical results and the actual trabecular architecture in the literature. The proposed numerical framework and results demonstrated the potential use of the topology optimization-based numerical tool for putative treatments in advance of actual clinical procedures for the patients. - Structural and micromechanical characterization of type I collagen gels
Latinovic O Hough LA Daniel Ou-Yang H - J Biomech 43(3):500-505 (2010)
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 gels and the corresponding viscoelastic properties provide benchmark measurements for the behavior of desirable biological materials, or tissue equivalents. - Leg stiffness adjustment for a range of hopping frequencies in humans
Hobara H Inoue K Muraoka T Omuro K Sakamoto M Kanosue K - J Biomech 43(3):506-511 (2010)
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 3.0 Hz). 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 3.0 Hz than at 1.5 Hz. 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 1.5 Hz, followed by the 2.2 Hz and then 3.0 Hz. The subjects landed with a straighter leg (both hip and knee were extended more) with increased hopping frequency. These results suggest that over the range of hopping frequencies we e! valuated, humans adjust leg stiffness by altering hip and knee stiffness. This is accomplished by extending the touchdown joint angles rather than by altering neural activity. - Probabilistic finite element analysis of the uncemented hip replacement—effect of femur characteristics and implant design geometry
Dopico-González C New AM Browne M - J Biomech 43(3):512-520 (2010)
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 approximation between the random variables and the output were used as the sensitivity values. In all cases, bone-implant position related parameters were the most sensitive parameters. The re! sults varied depending on the femur, the implant design and the interface conditions. Values of maximum nodal micromotion agreed with results from previous studies, confirming the robustness of the implemented computational tool. It was demonstrated that results from a single model study should not be generalised to the entire population of femurs and that bone variability is an important factor that should be investigated in such analyses. - Primary stability of uncemented femoral resurfacing implants for varying interface parameters and material formulations during walking and stair climbing
Rothstock S Uhlenbrock A Bishop N Morlock M - J Biomech 43(3):521-526 (2010)
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 element (FE) models of the proximal femur were developed. Implantation was realized by displacing the prosthesis onto the femur while monitoring the contact pressure, plastic bone deformation as wel! l as implantation forces. Subsequently a physiologic gait and stair-climbing cycle was simulated calculating the micromotion at the bone-implant interface. Results indicate that plastic deformation starts at an interference of 30 μm and the amount of plastified bone at the interface increases up to 90% at 150 μm interference. This effect did not reduce the contact pressure if interference was below 80 μm. The micromotion during walking was similar for the elastic and plastic FE models. A stable situation allowing bony ingrowth was achieved for both constitutive laws (elastic, plastic) for walking and stair climbing with at least 60 μm press-fit, which is feasible with clinically used implantation forces of 4 kN. - An injury risk curve for the hip for use in frontal impact crash testing
Rupp JD Flannagan CA Kuppa SM - J Biomech 43(3):527-531 (2010)
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 parametric distribution was used to define relationships between force applied to the hip and the risk of hip fracture for the statures associated with the small female, midsize male, and large male c! rash-test dummies, thus allowing these dummies to assess hip fracture/dislocation risk in frontal crashes, provided that such dummies are sufficiently biofidelic. For the midsize male crash test dummy, a 50% risk of hip fracture was associated with a force of 6.00 kN. For the small female and large male dummies, a 50% risk of hip fracture was associated with forces of 4.46 and 6.73 kN, respectively. - Muscle activity during the active straight leg raise (ASLR), and the effects of a pelvic belt on the ASLR and on treadmill walking
Hu H Meijer OG van Dieën JH Hodges PW Bruijn SM Strijers RL Nanayakkara PW van Royen BJ Wu W Xia C - J Biomech 43(3):532-539 (2010)
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 was more activity of the contralateral m. biceps femoris, and in treadmill walking of the m. gluteus maximus in conditions with a belt. For our interpretation, we take our starting point in the ! fact that hip flexors exert a forward rotating torque on the ilium. Apparently, the abdominal wall was active to prevent such forward rotation. If transverse and oblique abdominal muscles press the ilia against the sacrum (Snijders' "force closure"), the pelvis may move as one unit in the sagittal plane, and also contralateral hip extensor activity will stabilize the ipsilateral ilium. The fact that transverse and oblique abdominal muscles were less active in conditions with a pelvic belt suggests that the belt provides such "force closure", thus confirming Snijders' theory. - Individualized optimal release angles in discus throwing
Leigh S Liu H Hubbard M Yu B - J Biomech 43(3):540-545 (2010)
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 were estimated for each subject using the regression relationships and equations of projectile motion. The estimated optimal release angle was different for different subjects, and ranged from 35! ° to 44°. The results of this study demonstrate that the optimal release angle for discus throwing is thrower-specific. The release angles used by elite discus throwers in competition are not necessarily optimal for all discus throwers, or even themselves. The results of this study provide significant information for understanding the biomechanics of discus throwing techniques. - Temperature-dependent threshold shear stress of red blood cell aggregation
Lim HJ Lee YJ Nam JH Chung S Shin S - J Biomech 43(3):546-550 (2010)
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 temperature. However, the threshold shear rate and the threshold shear stress increased as the temperature decreased, which is a trend that agrees with that of the blood viscosity. As the tempe! rature decreases, RBC aggregates become more resistant to hydrodynamic dispersion and the corresponding threshold shear stress increases as does the blood viscosity. Therefore, the threshold shear stress may help to better clarify the mechanics of RBC aggregation under both physiological and pathological conditions. - Mechanomyography is more sensitive than EMG in detecting age-related sarcopenia
Tian SL Liu Y Li L Fu WJ Peng CH - J Biomech 43(3):551-556 (2010)
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±4.5 yr) and young (n=10, 22.6±2.8 yr) 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 significantly less LTV, absolute and relative maximal force, as well as absolute and relative maximal power (p<.05). EMGMF of the elderly and the young increased monotonically from 45% to 75% 1! RM testing conditions. While the MMGRMS of the young increased with testing intensities, the MMGRMS of the elderly increased only from 45% to 60% but leveled off from 60% to 75% 1 RM testing conditions. The results indicate the declines of muscle mass, force and power production capacity with aging. The observations could be explained by neuromuscular performance and change of MU activation patterns may result from age-related sarcopenia. Aging affected muscle power more than muscle strength, which could be due to fast fiber reduction. This is supported by our observations that the MMGRMS differences between the young and the elderly across all three intensity level where EMGRMS was only different at the greatest intensity. We suggest that MMG could be used as an important measurement in studying muscle contraction in age-related sarcopenia. - A finite element inverse analysis to assess functional improvement during the fracture healing process
Weis JA Miga MI Granero-Moltó F Spagnoli A - J Biomech 43(3):557-562 (2010)
Assessment of the restoration of load-bearing function is the central goal in the study of fracture healing process. During the fracture healing, two critical aspects affect its analysis: (1) material properties of the callus components, and (2) the spatio-temporal architecture of the callus with respect to cartilage and new bone formation. 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 cha! nges in the stiffness that occur during the healing time points. In addition, simulation studies regarding sensitivity to initial guess and noise are presented; as well as the influence of callus architecture on the FEA estimated material property metric. The finite element model inverse analysis developed can be used to determine the effects of genetics or therapeutic manipulations on fracture healing in rodents. - Simulation of orthotropic microstructure remodelling of cancellous bone
Kowalczyk P - J Biomech 43(3):563-569 (2010)
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 a hip endoprosthesis. - Diffusion of water in skeletal muscle tissue is not influenced by compression in a rat model of deep tissue injury
van Nierop BJ Stekelenburg A Loerakker S Oomens CW Bader D Strijkers GJ Nicolay K - J Biomech 43(3):570-575 (2010)
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 (10–150 kDa) 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 molecules. Additionally the relationship between muscle temperature and diffusion was investigated. During deformation of the tibialis anterior a decrease of the apparent diffusion coefficient (! ADC) was observed (7.2±3.9%). The use of a finite element model showed that no correlation existed between the maximum shear strain and the decrease of the ADC. The ADC in the uncompressed gastrocnemius muscle decreased with 5.9±3.7%. In an additional experiment a clear correlation was obtained between the decrease of the ADC and the relative temperature change of skeletal muscle tissue as measured by MRI. Taken together, it was concluded that (1) the decreased diffusion of water was not a direct effect of tissue deformation and (2) that it is likely that the observed decreased ADC during deformation was a result of a decreased muscle temperature. The present study therefore provides evidence that diffusion of small molecules, particularly oxygen and carbon dioxide, is not impaired during deformation of skeletal muscle tissue. - Side-to-side differences in anterior cruciate ligament volume in healthy control subjects
Jamison ST Flanigan DC Nagaraja HN Chaudhari AM - J Biomech 43(3):576-578 (2010)
Examination of anterior cruciate ligament (ACL) anatomy is of great interest both in studying injury mechanisms and surgical reconstruction. However, after a typical acute ACL rupture it is not possible to measure the dimensions of the ACL itself due to concomitant or subsequent degeneration of the remaining ligamentous tissue. The contralateral ACL may be an appropriate surrogate for measuring anatomical dimensions, but it remains unknown whether side-to-side differences preclude using the contralateral as a valid surrogate for the ruptured ACL. 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<0.0001)! . The results of this study show that the volume of the contralateral ACL is a valid surrogate measure for a missing ACL on the injured side. This non-invasive, in vivo technique for measuring ACL volume may prove useful in future large-scale comprehensive studies of potential risk factors for ACL rupture, in quantifying potential loading effects on ACL size as a prophylactic measure against ACL rupture, and in the use of ACL volume as a screening tool for assessing risk of injury. - The effects of the interthalamic adhesion position on cerebrospinal fluid dynamics in the cerebral ventricles
Cheng S Tan K Bilston LE - J Biomech 43(3):579-582 (2010)
The interthalamic adhesion is a unique feature of the third ventricle in the brain. It differs in shape and size and its location varies between individuals. 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 adhesion may have functional i! mplications on the development of hydrocephalus and it is important to model this anatomical feature in future studies. - Comparing polynomial and cubic spline interpolation of segment angles for estimating L5/S1 net moment during symmetric lifting tasks
Xu X Chang CC Faber GS Kingma I Dennerlein JT - J Biomech 43(3):583-586 (2010)
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 (<6) the error in the predicted moment from both the spline and polynomial fits decreased with the increase in the number of interpolation points; however, above 6 interpolation points error for the polynomial fits started to increase while the error from the spline fit continued to decrease. These results suggest that cubic spline interpolation on body segments angles provides a more ro! bust basis for calculating L5/S1 net moment from a few key video frames. - A fully implantable telemetry system for the long-term measurement of habitual bone strain
de Jong WC Koolstra JH van Ruijven LJ Korfage JA Langenbach GE - J Biomech 43(3):587-591 (2010)
Long-term in-vivo recordings of habitual bone strain in freely moving animals are needed to better understand the everyday mechanical loading environment responsible for bone-tissue maintenance. However, wireless methods to make such recordings are scarce. 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 33 h. 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 histor! y defining the architecture and composition of bone tissue, and can help to further elucidate the strain parameters which influence bone tissue. - Evaluation of alternative technical markers for the pelvic coordinate system
Kisho Fukuchi R Arakaki C Veras Orselli MI Duarte M - J Biomech 43(3):592-594 (2010)
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 at the thighs based on the Helen-Hayes marker set); (5) markers at the PSIS and at the iliac spines. Concerning the pelvic angles, evaluation of the alternative technical marker sets ! evinced that all marker sets demonstrated similar precision across trials (about 1°) but different accuracies (ranging from 1° to 3°) in comparison to the standard marker set. We suggest that all the investigated marker sets are reliable alternatives to the standard pelvic marker set. - Corrigendum to "Effective leg stiffness in running"
- J Biomech 43(3):595 (2010)
- Corrigendum to "Static and dynamic human flexor tendon–pulley interaction" [J. Biomech. 42 (2009) 1856–1861]
- J Biomech 43(3):596 (2010)
- Erratum to "A holistic numerical model to predict strain hardening and damage of UHMWPE under multiple total knee replacement kinematics and experimental validation" [J. Biomech. 42 (2009) 2520–2527]
- J Biomech 43(3):597 (2010)
- Erratum to "Inertial sensor-based knee flexion/extension angle estimation" [J. Biomech. 42 (2009) 2678–2685]
- J Biomech 43(3):598 (2010)
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