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N Berme

Publications and source records attributed to N Berme.

13 recordsLinked to original sources
PubMed1989

Quantitative assessment of gait determinants during single stance via a three-dimensional model--Part 1. Normal gait.

In this two-part paper, a variety of three-dimensional, dynamical models are constructed for simulating the single support phases of normal and pathological human gait. A major objective of this work is to quantify the influence of individual gait determinants on the ground reaction forces generated during normal, level walking. To this end, Part 1 presents a three-dimensional, seven degree-of-freedom model incorporating five of the six fundamental determinants of gait. On the basis of crude muscle-force and/or joint-moment trajectories, body-segmental motions and ground reaction forces are synthesized open loop. Through a quantitative comparison with experimental gait data, the model's predictions are evaluated. Our simulation results suggest that pelvic list is not as dominant a dynamical determinant as either stance knee flexion-extension or foot and knee interaction. Transverse pelvic rotation, however, makes an important contribution by limiting the magnitude of the horizontal ground reaction prior to opposite heel-strike.

Adult↗
PubMed1989

Quantitative assessment of gait determinants during single stance via a three-dimensional model--Part 2. Pathological gait.

A three-dimensional model for normal gait formulated in Part 1 is now altered to simulate the dynamics of pathological walking. Mechanisms fundamental to the production of a normal gait pattern are systematically removed, in order to assess contributions from individual gait determinants. Four separate pathological cases are studied: a model neglecting ankle plantarflexor activity; absence of stance knee flexion-extension and foot and knee interaction; both pelvic list and transverse pelvic rotation removed; and finally, a model with all major gait determinants missing. These are used collectively to show that stance knee flexion-extension and foot and knee interaction successively dominate lower-extremity dynamical response during the single support phase of normal gait. The hip abductor muscles, while effecting pelvic list, serve to stabilize this limb, rather than actively determine whole-body vertical acceleration. Mechanisms compensating for a loss in joint motion are also explored. Complete ankle loss may be successfully compensated with increased hip abductor muscle activity; the loss of both ankle and knee, however, demand unacceptable levels of vertical pelvic displacement.

Adult↗
PubMed1988

On the construction, circuitry and properties of liquid metal strain gages.

A quick and easy method by which reliable and accurate liquid metal strain gages (LMSG) can be manufactured for use in measuring large strains within biological tissues has been developed. The circuitry used to power the gages is also simple and allows gage voltages to be recorded without the need for instrumentation amplifiers. An added advantage is that the gage output indicates absolute gage length rather than change in gage length. Lastly, evaluation of these gages error sensitivity has shown them to be acceptable for measurement of strains of magnitudes occurring within many soft tissues.

Biomechanical Phenomena↗
PubMed1988

A numerical method for simulating the dynamics of human walking.

This paper presents a general method for simulating the movement of the lower extremity during human walking. It is based upon two separate algorithms: one for single support (an open kinematic chain), and the other for the double support phase (a closed-loop linkage). Central to each of these is the recursive Newton-Euler inverse dynamics algorithm, applicable, as given, to any serial, spatial linkage. For the unconstrained single support model, the Newton-Euler scheme is applied directly to numerically generate the equations of motion. In the case of double support, however, the kinematic constraint equations are used to first eliminate the redundant degrees of freedom, and then solve for the unknown ground reactions under the constrained limb. The attractiveness of the method is that it offers a compact alternative to manually deriving the equations defining a mathematical model for human gait.

Algorithms↗
PubMed1988

Synthesis of human walking: a planar model for single support.

A mathematical model for the single support phase of normal, level, human walking is formulated. The motion of the lower extremity is synthesized using a preprogrammed set of inputs, recognized by the model as a simple collection of applied joint moments. Two mechanisms are forwarded as candidates for producing the observed peaks in the vertical ground reaction. The first, stance knee flexion-extension, generates the necessary level of whole-body vertical acceleration during the initial region of single support (opposite toe-off to heel-off). A model accounting for the determinants of foot and knee interaction then predicts the second peak to be the result of an increasing ankle moment in the region from heel-off to opposite heel-strike.

Acceleration↗
PubMed1988

An experimental and analytical study of impact forces during human jumping.

Impact forces during landing in dismounts from the horizontal bar onto regulation gymnastic mats and in jumping from a height of 0.45 m onto a hard surface were measured. A two degree-of-freedom dynamic model was developed to predict the forces in landing on the hard surface. The periods of the two peaks that can be identified from experimental data were used in the determination of the system parameters. The peak forces recorded in gymnasts' landing ranged from 8.2 to 11.6 times the body weight. Maximum forces in jumping from 0.45 m, which ranged from 5.0 to 7.0 times the body weight, were accurately predicted by the model.

Biomechanical Phenomena↗
PubMed1988

The dynamics of quadrupedal locomotion.

This paper presents a dynamical analysis of quadrupedal locomotion, with specific reference to an adult Nubian goat. Measurements of ground reaction forces and limb motion are used to assess variations in intersegmental forces, joint moments, and instantaneous power for three discernible gaits: walking, running, and jumping. In each case, inertial effects of the torso are shown to dominate to the extent that lower-extremity contributions may be considered negligible. Footforces generated by the forelimbs exceed those exerted by the hindlimbs; and, in general, ground reactions increase with speed. The shoulder and hip dominate mechanical energy production during walking, while the knee plays a more significant role in running. In both cases, however, the elbow absorbs energy, and by so doing functions primarily as a damping (control) element. As opposed to either walking or running, jumping requires total horizontal retardation of the body's center of mass. In this instance, generating the necessary vertical thrust amounts to energy absorption at all joints of the lower extremities.

Animals↗
PubMed1987

Femoral cement removal in revision total hip arthroplasty. A biomechanical analysis.

A technique of femoral cement removal in revision total hip arthroplasty is described and biomechanically evaluated. Two 9-mm holes are drilled anteriorly through the proximal femoral cortex before cement is removed. These holes permit direct visualization of the medullary canal and help to prevent eccentric reaming or inadvertent perforation with the power drill. They also provide portals for enhanced irrigation, illumination, and cement removal. For assessment of the effect of cortical perforations on bone strength, 12 cadaveric femurs containing cemented prosthetic stems were analyzed. The femurs were stressed at various loads on the Instron Materials Testing Machine (Instro Engineering Corporation, Kenton, MA) under conditions simulating single-limb stance. The stress concentrations were significantly higher about laterally drilled holes than about those located anteriorly. When loaded to failure, all fractures occurred at or below the prosthetic stem tip. No fractures occurred in the proximally placed drill holes. A finite element model showed that two holes kept at least two hole diameters apart did not cause cumulative stress concentration.

Biomechanical Phenomena↗
PubMed1979

Load actions transmitted by implants.

The authors consider the mechanics of load transmission between a "conventional" femoral head replacement prosthesis and the shaft of the femur. The three dimensional loading pattern is now well known and the changes of interface stressing through a load cycle is considered. The actual stress situation depends on features of the implantation technique, the mechanical properties of all the materials involved in the relevant friction coefficient. From analysis of systems at the extreames of these limits, the authors suggest probable service conditions.

Femur↗
PubMed1978

Measurement of prosthetic alignment.

An essential part of alignment description is the position and orientation of the socket relative to the rest of the limb. Repeatable measurements of these parameters is hindered by the non-geometrical shape of the socket. A unique axis system has already been defined to enable such measurements to be carried out. The method however, employs an iterative technique and is time consuming. A simple device to facilitate these measurements has been developed and is reported.

Amputation Stumps↗