External Joint Research Articles

Kinematic analysis of functional lower body perturbations

Background Sudden changes in direction on a single weight-bearing-limb are commonly associated with injury to the lower extremity. The purposes of this study were to assess the between day reliability of hip, knee, and ankle kinematic displacements achieved with internal and external femur-on-weight-bearing-tibia rotation perturbations and to determine the effect of these perturbations on three dimensional hip, knee and ankle kinematics. Methods Twenty recreationally active, healthy college students with no history of significant orthopedic injury (10 male, 10 female) were subjected to a forward and either internal or external rotary perturbation of the trunk and thigh on the weight-bearing-tibia while three dimensional kinematics were simultaneously collected. The protocol was repeated 24–48 h later to assess reliability. Findings External perturbations resulted in significant internal rotation (IR) of the tibia on the femur (mean 7.3 (SD 3.9°)) and IR of the femur on the pelvis (mean 6.8 (SD 5.4°)) ( P < 0.05). Internal perturbations resulted in significant external rotation (ER) of the tibia on the femur (mean 6.8 (5.9°)) and ER of the femur on the pelvis (mean 10.7 (SD 96.1°)) ( P < 0.05). Additionally the external perturbation results in a significantly greater knee valgus (mean 3.6 (SD 2.2°)) position while the internal perturbation results in a significantly greater knee varus position (mean 2.3 (SD 3.5°)) ( P < 0.05). External perturbation hip and knee total joint displacements revealed moderate to strong reliability (Intraclass Correlation Coefficient 2, k = 0.67–0.94) while internal perturbations revealed slightly higher Intraclass Correlation Coefficients 2, k (0.80–0.96). Interpretation The lower extremity perturbation device provides a consistent external and internal perturbation of the femur on the weight-bearing-tibia. The observed transverse and frontal plane kinematics are similar to motions observed during cross-over and side-stepping tasks.

Safety upgrade of the Arlberg Base Tunnel and Tunnel Perjen

The 13.9 km long Arlberg road tunnel and the 2.9 km long Perjen Tunnel, both single tube, were reconstructed. Fully adjustable and remote controlled smoke extraction openings of approximately 9 m2 cross-section were installed. This required reconstruction of the highly utilised false ceiling. For this purpose doweled, corrosion-resistant steel structures and externally applied carbon-fibre reinforcement and external joint taping were applied. An emergency air supply system to feed the emergency call niches was installed. The electro-mechanical installations were modernised. The level of tunnel safety might be considered to be a function of (a) the structural safety level (e.g. ventilation ducts of a certain fire resistance will allow the maintenance of the ventilation for a defined time) and (b) the safety level given by tunnel installations and operation (e.g. the reaction time of the ventilation system or the smoke extraction capacity of the ventilation system). It was found that the safety upgrade of existing tunnels would tend to focus on measures to improve level (b). Normally there is little existing data and no time given to perform systematic structural check-ups of the tunnel elements that should be reconstructed. The consequence is a compromise between estimates based on experience and engineering judgement on the one hand and the postponement of some of these checks into the construction period to prove the design assumptions done on the other hand. This may result in work change orders. The paper concludes, that: (1) Tunnel safety upgrades will focus on the improvements to the tunnel operating systems, because it is only possible with extraordinary financial investment to change the structural safety of existing tunnels. (2) It may be necessary to exceed in such projects the requirements of modern tunnel standards for tunnel operating systems. (3) It is characteristic for projects discussed above that only a minor part of the structure is reconstructed (single fields of a false ceiling). Accordingly, it is necessarily not useful to fully consider any latest requirements of standards (e.g. requirements of corrosion resistance of steel suspensions or fire resistance). This relative approach to measures would save money without negative effect on safety. (4) Detailed as-built drawings should be produced for newly built tunnels to give a sound basis for later reconstruction. (5) The alternative for existing tunnels is the performance of a status inspection of the relevant structures. Since this is time consuming, it should be considered well ahead of the time the owner intends to commence design. The effort will result in better contractual quality. (6) Especially reconstruction comprises works that can not be quantified or specified prior to tender. The standard unit price contract is not flexible for such a situation. (A). Reprinted with permission from Elsevier. For the covering abstract see ITRD E124500.

Landing Differences in High School Female Soccer Players Grouped by Age

2036 PURPOSE: The purpose of the current study was to compare drop vertical jump (DVJ) landings in high school soccer players based on their chronological age. The American Academy of Orthopaedic Surgery has reported that ACL reconstructive surgeries in females peak at approximately 16 yrs of age. The hypothesis tested was that biomechanical loading of the knee would peak at 16 yrs of age in the female athletes. METHODS: Eight high school soccer teams were recruited to participate in this study. 88 female athletes were tested prior to the start of their season. The subjects were grouped according to their chronological age of 14 (n = 24), 15 (n = 25), 16 (n = 19) and 17 (n = 20). 25 retroreflective markers were placed on each subject. Each athlete performed the DVJ as described previously (Ford 2003). Vertical ground reaction force (GRF) and external knee ab/adduction moment were recorded for the dominant leg. The values were normalized to body weight (GRF) and body weight × height (moments). An ANOVA test with a Fischer's LSD post-hoc analysis was used to identify differences between groups. RESULTS: Significant age differences were found between the peak external knee abduction moments (ABD) during landing (p<0.05). ABD was greater in 14, 15 and 16 yr. olds(−0.02 ± 0.01, −0.02 ± 0.02, and −.03 ± 0.02 Nm/kg*m respectively) compared to the 17 yr olds (−.01 ± 0.01 Nm/kg*m). Differences in peak GRF was also found between the 16 (2.1 ± 0.5 N/kg) and 17 yr olds (1.7 ± 0.4 N/kg, p<0.05). No differences in knee flexion/extension angles were found between groups (p = 0.59). CONCLUSIONS: This study found differences among high school soccer players based on their age in external knee joint loads and vertical GRF during an athletic maneuver. External abduction knee joint loads peak at age 16 in high school soccer players. This may reflect a difference in neuromuscular performance in the age group. Neuromuscular training may be initiated in younger athletes with the goal to decrease potentially harmful forces and moments during landing or cutting movements. Although the peak in ACL surgeries may be related to high overall participation rates, biomechanical differences during an athletic movement may also be partially responsible.

Board Level Reliability Enhancement for A Double-bump Wafer Level Chip Scale Package

This paper presents a nonlinear finite element analysis on board level solder joint reliability enhancement of a double-bump wafer level chip scale package (CSP). A viscoplastic constitutive relation is adopted for the solders to account for its time and temperature dependence in thermal cycling. The fatigue life of solder joint is estimated by the modified Coffin-Manson equation, which has been verified by experimental results using one of the double-bump wafer level CSP packages as the test vehicle. A series of parametric studies were performed by changing the Sn/Ag inner bump size (UBM pad size and standoff height), the eutectic Sn/Pb external solder joint size (pad size and standoff height), pitch, die thickness, and the encapsulant thickness. The results obtained from the modeling are useful to form design guidelines for board level reliability enhancement of the wafer level CSP packages.

Seismic performance of external reinforced concrete beam-column joints

Four external beam-column sub-assemblies were tested to investigate the influence of different details on the performance of the Joint zone. All the details conformed to the current New Zealand structural concrete standard (NZS3101-1995). It is shown that anchoring beam reinforcement in external beam- column joints short of the outer column bars results in a reduction in the flexural strength of the column. In tests premature yielding of the longitudinal bars on the inside of the column occurred when bars were anchored at a distance of 1⁄4 of the column depth from the outside face of the column, as permitted by the structural concrete Standard. This yielding had an adverse effect on the performance of the joint zone. A way of detailing external joint zones to compensate for this loss in strength is described. Elongation of plastic hinges in the beams of ductile frames induces unidirectional plastic hinges in the external columns at the first floor level. While this has a strong influence on the distribution of moments and shears in the columns tests indicated that it does not adversely affect the structural performance of the joint zone. The use of continuous bars bent in the form of a U provides a simple detail that worked very effectively. There was little difference in joint behaviour between beams with main bars uniformly distributed over the beam depth to conventionally reinforced beams with their main bars positioned near the top and bottom edges.

Dynamic loads are determinants of peak bone mass

This study investigated the association between non-invasive measurements of bone mass and markers of dynamic and static hip joint loads in subjects expected to be at peak bone mass. The bone mineral density (BMD) and bone mineral content (BMC) of three proximal femoral sites (neck, greater trochanter, and total) were measured by dual energy X-ray absorptiometry, and the peak external joint moments at the hip during walking and jogging were calculated from gait analyses of 31 normal human subjects ranging in age from 30 to 49 years (18 females, 13 males). Various multiple regression analyses were performed to determine how much of the variance in BMD and BMC was explained by height, body mass, and the peak hip joint moments. In total, the models explained up to 40% of the variance in BMD and 58% of the variance in BMC. Inclusion of height or body mass did not increase the explanatory power of the models for BMD and explained no more than 8% of the total variance in BMC once the joint moments from walking were allowed to enter the models. These data support the hypothesis that variance in peak bone mass is associated with variance in dynamic hip loads largely independent of the effect of static factors such as height and body mass.

Dynamics of Semi-Free Systems

Free systems permit a decoupling of the equations of the internalmovement from the external parameters thanks to a particularparametrisation. The present paper extends this property to thesemi-free systems which have a friction free joint with the ground.First, a planar case (model of a skier) is completely treated. Then acase in which a friction free external planar joint is dealt with. Asfor the free systems the necessary parametrisation becomesnon-holonomic. Consequently Hamel–Boltzmann's method is used, and, forexpressing all the useful quantities for this method the Global InertiaTensor are used.

上腕骨‐肩複合体系による座位‐立位補助運動の筋駆動多体動力学解析

A multibody dynamics model of the humerus-shoulder complex system, driven by a musculoskeletal system, has been formulated based on an updated Lagrange approach, using the continuum mechanics of muscle with the evolutional constitutive law of Hatze’s model. Japan’s population is rapidly aging; within the next 10 years, the elderly are expected to reach 25 percent of the total population. Assistive technology for recovery from disease and increasing medical expenses require more rational approaches to the bone-muscle system in limb-trunk motions, such as interactions between the thoracolumbar-spine system and the upper and lower limb system, which had been insufficiently analyzed.This paper focuses on a theoretical model of a multiple bones-joints system, driven by muscle activations. First we formulated the continuum mechanics of skeletal muscle with the evolutional constitutive law of Hatze (1977). A joint muscle activation generates kinematics and dynamics. For example, activation includes (1) generating angular motion of linked systems, for a multibone and multijoint system; (2) constraint of muscle contraction due to neuro-activation generating a counter force applied to equilibrate the external joint torque; (3) a paired contraction of counter muscles in a joint, giving rise to increased joint stiffness; and others. We therefore formulated the evolutional constitutive law of a muscle model so that it includes independent variables for both motion and constraint forces, the sum of which determine the activation level. The muscle constitutive equations were first formulated using the link coordinate system of each muscle strip. Then they were assembled by coordinate transformations from those for each strip to a common global system.A multi-body dynamics approach for a multiple bone-joint system driven by muscle activation was then formulated. The link element coordinates were defined for each bone, and positional vectors for the center of gravity of each bone, distance between adjacent joints, and muscle positional vector were formulated and transformed to the global coordinate system. Using the positional vectors, translational and rotational motions of individual elements, we formulated the kinetic energies of the elements and the potential energies stored in individual muscles and joint elements, expressed in incremental forms. The governing equations of motion for each link, and the dynamic equilibrium equation for each joint, based on the updated Lagrange method, were formulated and solved by prescribed constraint and applied load conditions, using the developed computer simulation system.As an actual application to assistive technology problems, an elderly person’s stand-up motion, aided by humerus-shoulder forces for lifting one’s upper body weight was analyzed. The calculated results for activation dynamics were compared with those, obtained from an EMG measurement experiment. Satisfactory agreement between these was confirmed, verifying that the developed computer system can satisfactorily estimate activation dynamics of muscle, replacing the traditional EMG measurement approach.

Mirror manipulator with independent adjustability using an external spherical joint

A new type of modular mirror manipulator with independent adjustability was developed for the EPU6 (Elliptically Polarizing Undulator) beamline under construction at the Pohang Accelerator Laboratory. The mirror manipulator was designed so that the angular displacements of roll and pitch rotations do not introduce translational displacements and are independent of each other by positioning the mirror center to the center of a newly devised spherical joint. While the designed angular resolution was 3.937 μrad, the angular resolutions for roll and pitch rotations were measured to be 3.94 μrad and 3.85 μrad, respectively. The independent adjustability of roll and pitch rotations was tested and confirmed to be within an acceptable performance range.

Design of a 6 DOF HFM manipulator using an external spherical joint

A new type of 5 Degrees of Freedom (DOF) modular mirror manipulator with independent adjustability had been developed at the Pohang Accelerator Laboratory. The design of the mirror manipulator was extended to a 6 DOF mirror manipulator by adding yaw adjustability. It also became applicable to mirrors that are set up laterally by replacing its mirror holder with a new L-shaped mirror holder. The moment necessary for yaw adjustment was calculated and the independent adjustability of yaw rotation was examined.

SEISMIC REHABILITATION OF BEAM-COLUMN JOINTS USING FRP LAMINATES

An innovative and practical technique for the seismic rehabilitation of beam-column joints using fiber reinforced polymers (FRP) is presented. The procedure is to upgrade the shear capacity of the joint and thus allow the ductile ftexural hinge to form in the beam. An experimental study is conducted in order to evaluate the performance of a full-scale reinforced concrete external beam-column joint from a moment resisting frame designed to earlier code then repaired using the proposed technique. The beam-column joint is tested under cyclic loading applied at the free end of the beam and axial column load. The suggested repair procedure was applied to the tested specimen. The composite laminate system proved to be effective in upgrading the shear capacity of the nonductile beam-column joint. Comparison between the behaviour of the specimen before and after the repair is presented. A design methodology for fibre jacketing to upgrade the shear capacity of existing beam-column joints in reinforced concrete moment resisting frames is proposed.

パワーグラスプの不静定把持力計算法

This paper analyzes the indeterminate grasp force in power grasps or enveloping grasps and shows that its region is a bounded hyper-polyhedron. In power grasps a hand grasps an object at multiple points on the surface of the hand. If the hand and the object are modeled as rigid bodies, then it is known that the grasp force is in general not determined uniquely even if joint torques are given. We have already shown that the sliding directions of the contact points are restricted in power grasps to be consistent with rigid body motion. Static friction force acts only in the opposite direction of sliding. This characteristic of friction leads to our previous conclusion that the grasp force is also restricted. This paper shows that the region of the indeterminate grasp force is a bounded hyper-polyhedron that is not necessarily convex. The force that requires maximum friction exists at the vertices of the polyhedron. We present a simple algorithm for computing the vertices of the hyper-polyhedron. It can efficiently compute the coefficient of friction sufficient to maintain static equilibrium given an external disturbance and joint torques taking the indeterminacy of the grasp force into account.

Tramatic brain injury decrease the amount of oligomerized β-amyloid peptide in cerebrospinal fluid

To investigate the effects of training induced fatigue on shoulder strength, ROM, joint position sense, and stroke length in elite competitive swimmers.Seventeen national level swimmers performed maximum isometric strength (internal and external rotation), ROM, and joint position sense tests before and after a fatiguing 8 × 100 m training set. Stroke length, heart rate, blood lactate and blood glucose levels were recorded throughout.Peak blood lactate, blood glucose levels, and heart rate increased significantly (P < 0.001) post-training confirming fatigue. Reductions were observed in stroke length of both arms (P < 0.001), external rotation range of motion (P < 0.001, −5.29°, Right shoulder; P = 0.04, −3.18°, Left shoulder) and joint position sense in their dominant (breathing side) arm (P = 0.03).This investigation revealed a reduction in stroke length across both arms and also an arm bias in swimming whereby a greater reduction in both external rotation range and joint position sense was observed in the dominant arm when fatigued. This has highlighted a relationship between fatigue and potential mechanism of shoulder pathology in swimmers.

Elbow and wrist joint contact forces during occupational pick and place activities

A three-dimensional, mathematical model of the elbow and wrist joints, including 15 muscle units, 3 ligaments and 4 joint forces, has been developed. A new strain gauge transducer has been developed to measure functional grip forces. The device measures radial forces divided into six components and forces of up to 250 N per segment can be measured with an accuracy of ±1%. Ten normal volunteers were asked to complete four tasks representing occupational activities, during which time their grip force was monitored. Together with kinematic information from the six-camera Vicon data, the moment effect of these loads at the joints was calculated. These external moments are assumed to be balanced by the internal moments, generated by the muscles, passive soft tissue and bone contact. The effectiveness of the body's internal structures in generating joint moments was assessed by studying the geometry of a simplified model of the structures, where information about the lines of action and moment arms of muscles, tendons and ligaments is contained. The assumption of equilibrium between these external and internal joint moments allows formulation of a set of equations from which muscle and joint forces can be calculated. A two stage, linear optimisation routine minimising the overall muscle stress and the sum of the joint forces has been used to overcome the force-sharing problem. Humero-ulnar forces of up to 1600 N, humero-radial forces of up to 800 N and wrist joint forces of up to 2800 N were found for moderate level activity. The model was validated by comparison with other studies.

Belt effects on lumbar sagittal angles

Objective. The study examined the belt effects on the change of lumbar sagittal angles. Design. The effects of pelvic and lumbar belts on lumbar sagittal angles were examined both radiographically and videographically in standing, erect sitting, and slump sitting. Background. The resulting changes of lumbar angles when wearing belts with different mechanical characteristics should be different. Methods. Eighteen healthy male subjects participated in this study. L1/L3, L3/L5, L5/S1 and L1/S1 were measured with the aid of lateral radiographs. The external joint angles were also measured via the motion analysis system. Results. Radiographic data revealed an interactive effect between working posture and the use of a belt ( P < 0.046) on the change of L1/S1. In standing, both belts increased L1/S1 by increasing almost all the lumbar vertebral angles. In erect sitting, wearing lumbar belt had no effect but the pelvic belt decreased L1/S1 mainly through a decrease in L1/L3. In sitting slump with trunk flexion of 15°, both belts increased L1/S1 and restricting the movement of the pelvis. Conclusions. Belt effect to the change of lumbar sagittal angles in posture which involve knee flexing and/or trunk flexing seems not as the same as in standing posture. Relevance This study related internal vertebral angles and externally measured trunk angles with lumbar and pelvic belt usage.

Variability in humeral dimensions in a sample of modern human females: Implications for measuring cortical bone loss.

Using data from a skeletal collection of early 20(th) century humans, this study explores characteristics of humeral measurements regarding assessment of gross cortical bone loss. The sample consists of 22 probable females, with estimated ages ranging from young to older adult and concentrated in middle adulthood. Multiple direct measurements reflecting bone quantity, including internal cortical bone and medullary cavity thickness and area, as well as external shaft and joint surface dimensions, are analyzed in an attempt to ascertain which measurement types, sites, and axes are most and least variable. Variability is specifically assessed through coefficients of variation and F-ratios. External dimensions are generally lower in dispersion than internal measures. Among cortical dimensions, percentage cortical area exhibits the least variability. The midshaft and distal sites appear substantially comparable in variability. Similar overall dispersion is also shown for the anteroposterior and mediolateral orientations. Recommendations concerning consistency of measurement and effectiveness in revealing cortical bone loss among living subjects and archaeological specimens are offered. Am. J. Hum. Biol. 12:118-127, 2000. Copyright 2000 Wiley-Liss, Inc.

Some Mechanical Considerations on Muscle Coordination

This commentary emphasizes three points of discussion. (a) The terminology: The terms multifunctional, synergisic, antagonistic muscles, and synergistic and antagonistic coactivations are discussed and the conclusion is drawn that they could not be used without mentioning the particular joint motion. (b) The importance of the external joint moments for activation of the muscles is confirmed on the basis of logical and mechanical considerations. Not all-experimental results, however, could be explained by this means. (c) The optimization criterion: Prilutsky's conclusion concerning the predicted muscle force proportionality to the muscle moment arm and PCSA is confirmed using a simple analytical solution of the optimization problem. It is shown, however, that the proportionality to the PCSA is a consequence of the chosen optimization criterion.

Statistical multiplexing using MPEG-2 video encoders

This paper presents a system for statistical multiplexing of several compressed video programs using MPEG-2-compatible video encoders. We propose a new external joint rate control algorithm to dynamically distribute the channel bandwidth among the program encoders such that the video quality is approximately equal in all programs. In our algorithm, the bit rate of each encoder is updated on the basis of the relative complexities of the programs measured at boundaries of groups of pictures (GOPs) and whenever scene changes are detected. The proposed algorithm requires no external preprocessing of the input video sources. Furthermore, as compared with previous work in this area, our algorithm is not restricted to operate only with encoders having the same GOP structure. Thus, the GOP boundaries at the different encoders need not be synchronized. Bit rate changes take place only at GOP boundaries, allowing the encoders to operate at a constant bit rate within GOPs. Overall, this results in a piecewise variable bit rate compression for each of the encoders. We also describe a strategy for decreasing the reaction delay of the system for scene changes. Experimental results show that the proposed multiprogram video compression system results in good picture quality with no external preprocessing, despite its relative simplicity.

About weight factors in the non-linear objective functions used for solving indeterminate problems in biomechanics

A lot of non-linear objective criteria are applied for solving the indeterminate problems formulated for different biomechanical models — most of them can be covered by the expression ∑c i| F → i| n . It might be noted, however, that most of the suggested criteria are not applicable if considerable antagonistic co-contractions exist. This could be an effect of treating the agonistic muscles and their respective antagonists in one and the same manner in the objective function. Using a completely inverse approach (the muscle forces are supposed to be known quantities) and a simple 1DOF model (actuated by three agonistic muscles and one corresponding antagonist) it has been shown which values of the weight factors c i may predict different levels of muscle forces from the two antagonistic groups. Three hypothetical border variants for magnitudes of the muscle forces are considered (flexor muscles are only active, extensor muscles are only active, considerable co-contraction of flexors and extensors exists). The main conclusions are: the signs of c i at agonistic muscles have to be opposite to the c i signs at their antagonists; the signs of the weight factors depend on the direction of the net external joint moment; the closer c i to zero, the bigger force will be predicted in the ith muscle.

Vertical jumping in Galago senegalensis: the quest for an obligate mechanical power amplifier

Bushbabies (Galago senegalensis) are renowned for their phenomenal jumping capacity. It was postulated that mechanical power amplification must be involved. Dynamic analysis of the vertical jumps performed by two bushbabies confirms the need for a power amplifier. Inverse dynamics coupled to a geometric musculo–skeletal model were used to elucidate the precise nature of the mechanism powering maximal vertical jumps. Most of the power required for jumping is delivered by the vastus muscle–tendon systems (knee extensor). Comparison with the external joint–powers revealed, however, an important power transport from this extensor (about 65%) to the ankle and the midfoot via the bi–articular calf muscles. Peak power output likely implies elastic recoil of the complex aponeurotic system of the vastus muscle. Patterns of changes in length and tension of the muscle–tendon complex during different phases of the jump were found which provide strong evidence for substantial power amplification (times 15). It is argued here that the multiple internal connective tissue sheets and attachment structures of the well–developed bundles of the vastus muscle become increasingly stretched during preparatory crouching and throughout the extension phase, except for the last 13 ms of the push–off (i.e. when power requirements peak). Then, tension in the knee extensors abruptly falls from its maximum, allowing the necessary fast recoil of the tensed tendon structures to occur.