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At least 415 records · Page 23Linked to original sources
PubMed2000

Ligament mechanics during three degree-of-freedom motion at the acromioclavicular joint.

The development of effective treatment and reconstruction procedures for injuries to the soft tissues around the acromioclavicular (AC) joint relies on a comprehensive understanding of overall joint function. The objective of this study was to determine the magnitude and direction of the in situ forces in the AC capsular and coracoclavicular ligaments as well as the resulting joint kinematics during application of three external loading conditions while allowing three degree-of-freedom joint motion. A robotic/universal force-moment sensor testing system was utilized to determine the in situ forces in the soft tissue structures and the resulting joint kinematics. The clavicle translated 5.1+/-2.0, 5.6+/-2.2, and 4.2+/-1.9 mm during application of a 70 N load in the anterior, posterior, and superior directions, respectively, representing almost a 50% increase over previous studies using similar load magnitudes. In response to an anterior load, the magnitude of in situ force in the superior AC ligament (35+/-18 N) was found to be greater (p<0.05) than the force in the trapezoid and conoid ligaments. In contrast, the magnitude of in situ force in the conoid (49+/-22 N) was significantly greater (p<0.05) than all other ligaments in response to a superior load. Additionally, the directions of the force vector representing the conoid and trapezoid were different, being located in opposing quadrants of the posterior axis of the scapula with this loading condition. Our data suggest that the kinematic constraints placed on the AC joint during loading affect the resulting joint motion and that the magnitude and direction of force in each ligament are affected by the coupled motions that occur. Based on the differences in magnitude and direction of the in situ force in the coracoclavicular ligaments with each loading condition, surgical procedures should reconstruct these ligaments in a more anatomical manner or treat them separately to prevent joint degeneration.

Acromioclavicular Joint↗
PubMed1995

A six-degree-of-freedom test system for the study of joint mechanics and ligament forces.

A joint testing system was designed to transmit a specified motion or force to a joint in all six degrees of freedom (d.o.f.) using a spatial linkage system for position feedback. The precise reproducibility of position provided by this method of position feedback allows determination of in situ ligament forces for external joint loadings. Load on the structure of interest is calculated from six d.o.f. load cell output after the loaded position is reproduced with all other structures removed. In a test of this system, measured loads showed good agreement with applied loads.

Algorithms↗
PubMed1996

Normal six-degree-of-freedom motions of knee joint during level walking.

The purpose of this study was to find an effective way for in vivo measurement of joint motion and give the normal knee motion according to this method. The joint model proposed by Grood and Suntay (1983) was chosen; the origin of the tibia was modified for the convenience of in vivo test. A computerized 6 degree-of-freedom electrogoniometer (EGM) was used in the measurement. Repeated tests on one subject were performed to establish the reliability of the method. Knee motions obtained from 42 males during level walking were expressed as flexion-extension, abduction-adduction, external-internal rotation, lateral-medial translation, anterior-posterior translation, and superior-inferior translation. The results showed that, with the proper choice of the origin of the tibia, the EGM could depend much less on external landmarks and be more effective for the joint measurement.

Adult↗
PubMed1997

Predicting the impact response of a nonlinear single-degree-of-freedom shock-absorbing system from the measured step response.

We measured the step response of a surrogate human pelvis/impact pendulum system at force levels between 50 and 350 N. We then fit measured response curves with four different single-degree-of-freedom models, each possessing a single mass, and supports of the following types: standard linear solid, Voigt, Maxwell, and spring. We then compared model predictions of impact force during high-energy collisions (pendulum impact velocity ranging from 1.16 to 2.58 m/s) to force traces from actual impacts to the surrogate pelvis. We found that measured peak impact forces, which ranged from 1700 to 5600 N, were best predicted by the mass-spring, Maxwell, and standard linear solid models, each of which had average errors less than 3 percent. Reduced accuracy was observed for the commonly used Voigt model, which exhibited an average error of 10 percent. Considering that the surrogate pelvis system used in this study exhibited nonlinear stiffness and damping similar to that observed in simulated fall impact experiments with human volunteers, our results suggest that these simple models allow-impact forces in potentially traumatic falls to be predicted to within reasonable accuracy from the measured response of the body in safe, simulated collisions.

Accidental Falls↗
PubMed1990

Implementation of a five degree of freedom automated system to determine knee flexibility in vitro.

This article describes an automated system designed to study the complete flexibility functions of the knee in vitro. The system allows five degrees of freedom with flexion angle being fixed, though adjustable from 0 to 45 deg. Loads corresponding to each of the five motions can be applied independently and in any combination. The effect of weight bearing on knee flexibility can also be studied by including axial force as one of the five loads. The relative motions are measured with LVDT's and RVDT's, and the loads are measured with strain gage transducers. The system is digitally controlled with a closed feedback loop, allowing for any combination of programmed loads. A control algorithm on an IBM PC/AT monitors the loads on each axis and continuously adjusts stepping motors to correctly follow programmed loads. The machine coordinate system corresponds to clinically accepted definitions of motion yet retains sequence independence for rotations. Results are presented demonstrating the repeatability of using a functional definition of axis placement to align the leg within the machine. Results are also presented demonstrating the utility of the full flexibility functions of the knee, notably in the determination of significant load interactions between anterior/posterior force and internal/external torque, and varus/valgus torque and internal/external torque.

Algorithms↗
PubMed1994

A multi-degree of freedom system for biomechanical testing.

A system is described that allows axial, torsional, and bending testing of biomechanical specimens. The system uses electric motors under closed loop control in its grips allowing application of pure bending moments. These grips attach to an axial/torsional testing system. Thus, it provides simultaneous closed loop control of all three degrees of freedom (D.O.F), so that under any given test condition either the loads or the displacements for each D.O.F. can be maintained at zero, selected constant values, or simultaneously controlled. This enables the expedient evaluation of the mechanical behavior of biological structures under complex loadings or simple loadings (one D.O.F.) with no artificially induced constraints in the other two D.O.F.'s due to specimen mounting.

Biomechanical Phenomena↗
PubMed1996

Measurements of magnetism-related forces and torque moments affecting medical instruments, implants, and foreign objects during magnetic resonance imaging at all degrees of freedom.

We designed a novel force/torque moment transducer with six degrees of freedom. This new sensor is used for measuring the forces and torque moments exerted by static magnetic resonance imaging (MRI) fields on various medical implants, instruments, and ballistic shell fragments. To determine the location of strongest effect the inhomogeneity of the magnetic field between the entrance of the MRI-tube (portal), and the imaging section was measured. Force and torque moments of a sample of 45 objects were measured at two positions, at the portal, and in the center of the imaging section. We classified the objects regarding to the magnetism-related forces measured in the homogeneous part of the MRI tube. About one-third of the objects was non- or weakly magnetic, one-third moderately, and the last third was strongly magnetic. Forces within the inhomogeneous area of the magnetic field at the entrance part of the tube were up to half a magnitude larger than forces inside the homogeneous imaging section. Here the greatest potential risks to patients might occur.

Biophysical Phenomena↗
PubMed2005

Muscle synergies at the elbow in static and oscillating isometric torque tasks with dual degrees of freedom.

This study's aim was to identify the effect of oscillation of torques in isometric tasks under identical mechanical conditions on the muscle synergies used. It was hypothesized that bi-functional muscles would play a lesser role in torque oscillation, because they would also generate an undesired oscillation. Thus, changes in muscle synergies were expected as a consequence of oscillation in torque generation. The effect of the trajectory of torque generation was investigated in dual-degrees-of-freedom submaximal isometric oscillation torque tasks at the elbow. The torques were flexion-extension and supination-pronation. Oscillation torques were compared with static torque generations at four torque positions during oscillation. Muscle activity was determined with surface electromyography. Compared with the static torque tasks, the oscillation tasks showed an overall increased muscle activity. The oscillation tasks, however, showed similar activity patterns and muscle synergies compared to the static composite tasks. It was found that the motor system is well able to control different orthogonal combinations of slow torque oscillations and constant torques by employing a single oscillating muscle synergy.

Adolescent↗
PubMed2005

Freedom and rules: the acquisition and reprogramming of a bird's learned song.

Canary song is hierarchically structured: Short stereotyped syllables are repeated to form phrases, which in turn are arranged to form songs. This structure occurs even in the songs of young isolates, which suggests that innate rules govern canary song development. However, juveniles that had never heard normal song imitated abnormal synthetic songs with great accuracy, even when the tutor songs lacked phrasing. As the birds matured, imitated songs were reprogrammed to form typical canary phrasing. Thus, imitation and innate song constraints are separate processes that can be segregated in time: freedom in youth, rules in adulthood.

Aging↗
PubMed2003

Effect of the RSPCA Freedom Food Scheme on the welfare of dairy cattle.

To evaluate the effect of the Royal Society for the Prevention of Cruelty to Animals Freedom Food (FF) scheme on the welfare of dairy cattle in England, 28 FF and 25 non-FF farms were assessed during the winter of 2000 to 2001. The assessments were based on a protocol which included the examination of the farms' records, the farmers' estimates of the incidence of disease, and independent observations of the behaviour and physical condition of the cows. The data were analysed to identify which measures of welfare were affected by FF membership and to assess the number of farms on which intervention would be required, as defined by a panel of 50 experts. The FF farms had better results for 12 of the welfare indicators, including those for mastitis, non-hock injuries, cow cleanliness and body condition, and poorer welfare indicators for eight of the measures, including hock injuries, lameness and restrictions in rising behaviour. Except for the prevalence of dull coats (which was lower on the FF farms) there were no significant differences in the proportions of FF and non-FF farms on which intervention was required according to the experts' assessment.

Animal Feed↗
PubMed2005

The bubble cloud as an N-degree of freedom harmonic oscillator.

The dynamics of a two-dimensional N-bubble static cloud is investigated and shown to be well described by an N-degree of freedom harmonic oscillator model, at least at low enough frequencies. Eigenmodes and eigenfrequencies are calculated and compared with experimental results obtained with an assembly of bubbles caught up under a net in a water tank. Accordance is found to be excellent in the frequency range of validity of the model, the limits of which are discussed. An interpretation of the low-frequency branch of Foldy's dispersion relation in bubbly liquids is suggested in terms of "bubble waves" in a quasi-incompressible medium.

Journal Article↗
PubMed2005

Neuromuscular adaptation during skill acquisition on a two degree-of-freedom target-acquisition task: dynamic movement.

In this experiment, we examined the extent to which the spatiotemporal reorganization of muscle synergies mediates skill acquisition on a two degree-of-freedom (df) target-acquisition task. Eight participants completed five practice sessions on consecutive days. During each session they practiced movements to eight target positions presented by a visual display. The movements required combinations of flexion/extension and pronation/supination of the elbow joint complex. During practice sessions, eight targets displaced 5.4 cm from the start position (representing joint excursions of 54 degrees) were presented 16 times. During pre- and posttests, participants acquired the targets at two distances (3.6 cm [36 degrees] and 7.2 cm [72 degrees]). EMG data were recorded from eight muscles contributing to the movements during the pre- and posttests. Most targets were acquired more rapidly after the practice period. Performance improvements were, in most target directions, accompanied by increases in the smoothness of the movement trajectories. When target acquisition required movement in both dfs, there were also practice-related decreases in the extent to which the trajectories deviated from a direct path to the target. The contribution of monofunctional muscles (those producing torque in a single df) increased with practice during movements in which they acted as agonists. The activity in bifunctional muscles (those contributing torque in both dfs) remained at pretest levels in most movements. The results suggest that performance gains were mediated primarily by changes in the spatial organization of muscles synergies. These changes were expressed most prominently in terms of the magnitude of activation of the monofunctional muscles.

Adaptation, Physiological↗
PubMed1977

Period of freedom from relapse as an indication of cure in minimal change nephrotic syndrome in adults.

17 adult-onset nephrotic patients with minimal-change glomerular lesions experienced 39 relapses in all. The relationship between the remission period t (expressed in months) preceding each relapse and the rate of relapse (relapse rate) F (t) was proven to correspond closely to Weibull's distribution function as follows (chi 2 = 1.72, 0.5 less than p less than 0.75): In In (formula - see text) From the equation, the time when 99% of relapsing patients have relapsed is 39.3 months. This means that adult-relapsing nephrotic patients with minimal-change lesions will experience a relapse within 39.3 months of remission. They should be free from relapse and considered cured with a 99% reliability when remission has continued longer than 39.3 months, i.e. beyond the 'period of freedom from relapse'.

Adolescent↗
PubMed1977

Freedom of inquiry and subjects' rights: historical perspective.

The author presents an historical overview of the various attitudes toward animal and human experimentation. He cites advocates (Bacon, Welch) and opponents (Johnson, Shaw) and traces the debate from the Graeco-Roman era, through the rise of the scientific establishment, to the present. Controversy over the fundamental rights of individual research subjects versus a future-oriented freedom of inquiry has been and continues to be a dilemma for clinicians and research scientists.

Animals↗
PubMed1977

Subjects' rights, freedom of inquiry, and the future of research in the addictions.

Since the recent passage of regulations concerning subjects' rights and freedom on inquiry, opposition by the public and others to some areas of research in the addictions has prevented its implementation or continuation. Research investigators in the biomedical and behavioral sciences have been placed in the position of defending their work in an adversary climate. The author points out the importance of transmitting to the public, the scientific community, and legislators the investigators' concern that "subjects' rights" not be viewed only in a legalistic context, but also in the context of not harming the patient.

Advisory Committees↗
PubMed2005

Increasing the degrees of freedom in existing group randomized trials: the df* approach.

This study describes a method for incorporating external estimates of intraclass correlation to improve the precision for the analysis of an existing group-randomized trial. The authors use a random-effects meta-analytic approach to pool the information across studies, which takes into account any interstudy heterogeneity that may exist. This approach can be used in several different situations to estimate the degrees of freedom available for an adjusted test of the intervention effect in a study where the challenges of group-randomized trials were not fully considered when the study was planned. The authors discuss the limitations of this approach and the circumstances in which it is likely to be helpful.

Humans↗
PubMed2006

Continuous suture technique for freedom stentless valve: reduced crossclamp time.

The Pericarbon Freedom stentless valve has shown excellent hemodynamics. A continuous suture technique at the inflow site may reduce cardiopulmonary bypass and crossclamp times and affect postoperative hemodynamics. In a prospective case-matched study, interrupted and continuous suture line techniques were used in 68 and 71 patients, respectively. Isolated valve replacement was performed in 70.4% of the continuous suture group and 67.6% of the interrupted suture group. Hemodynamic data were obtained by echocardiography (mean and peak gradients, regurgitation) at discharge and after 1 year. Overall mortality was 5.0% and due to non-valve-related causes. Bypass and crossclamp times were shorter by 22.4 and 20.6 min, respectively, in the continuous suture group. The suture technique at the inflow site did not result in significant differences in the mean (11.8 +/- 6.3 vs. 12.5 +/- 6.2 mm Hg) or peak gradients (21.0 +/- 9.6 vs. 22.0 +/- 10.9 mm Hg), or degree of regurgitation. Follow-up showed a further decrease in the gradients.

Aged↗
PubMedDate not supplied

Personal freedom and genetic overdetermination.

We do not intend to specify definite proposals as regards the scientific responsibility of genetic practice. This field of predicting the development of a pathology in an individual and family history requires reflection on the perception of personal risk, of the importance and reassurance deriving from a personal history, and of the benefits sharing knowledge and care with the clinical and scientific world. We evaluate the possibility to expand a reflection on sign-possibility and sign-expression of disease that could develop a wider comparison with personal freedom when confronted by genetic, philosophical and historical determinations. A parallel and preliminary consideration is made of guidelines for diagnostic and therapeutic behavior.

Genetic Diseases, Inborn↗