Joseph M. Mansour

Peak dynamic force in human gait

Abstract Studies were made of the forces generated at heel stroke in human gait using both force plates having a high resonant frequencies (capable of picking up high frequency components in the contact force) as well as a force transducer inserted into the heel of the shoe of the subjects. The output traces were analyzed for the existence of high frequency impulsive loads during a normal walking cycle. The effect of the complicance of the foot and floor was studied with the force transducers. The results showed that during normal human gait the lower limb is subjected to a high frequency impulsive load at heel strike. The severity of this impulse varied with the individual, the velocity and angle with which the limb aproached the ground and the compliance of the two materials coming in contact at heel strike. The magnitude of this peak force varied from 0.5 to 1.25 times body weight and its frequency components from 10 to 75 Hz.

Analysis and synthesis of human swing leg motion during gait and its clinical applications

Abstract A mathematical representation of the human leg during the swing phase of gait was developed. The modelling procedure employed variables which were known to be clinically significant physical, anatomical and physiological features influencing the gait pattern. These included: limitations in joint range of motion, alterations in the initial conditions of swing, changes in joint trajectories and changes in the inertial properties of the limb segments. The model implemented was such that these parameters could be independently varied to assess their relative importance in either normal gait, or in pathological gait and its correction. Using this approach, quantitative clinical data was incorporated into the mathematical description so that a better understanding of normal and pathological gait could be achieved.

The passive elastic moment at the hip

The passive elastic moment at the hip was measured in normal male subjects in situ. The influence of two joint muscles crossing the hip was evaluated by performing hip moment measurements over a continuous range of hip angles and at prescribed knee angles. The experimentally acquired data was fitted by exponential functions which separately modeled the moment contribution of tissues deformed by hip flexion and extension. The results of the investigation are discussed with regard to the possible role of the passive joint moments as an energy storage and release mechanism during human walking.

The nonlinear interaction between cartilage deformation and interstitial fluid flow

Abstract The movement of interstitial fluid through articular cartilage and its influence on the creep behavior of the tissue due to a unit step load function has been investigated. Experimental results are presented to show that the hydraulic permeability of articular cartilage depends on both the axial compressive strain on the tissue sample, as well as the driving pressure difference maintained across the specimen. These experimental results have been utilized in a known theory of a deformable and permeable material used to describe the behavior of articular cartilage. The creep-like behavior of the cartilage in compression has been analytically treated. It has been determined that the nonlinear interaction between the hydraulic permeability of the tissue and the compressive strain on the tissue retards the progress of the consolidation of the cartilage during uniaxial compression. However, the equilibrium displacement of the articular surface as t → ∞ depends only on the elastic constant of the parallel spring and dashpot viscoelastic behavior of the solid component of the tissue.

On the Natural Lubrication of Synovial Joints: Normal and Degenerate

Fluid flow and mass transport mechanisms associated with articular cartilage function are important biomechanical processes of normal and pathological synovial joints. A three-layer permeable, two-phase medium of an incompressible fluid and a linear elastic solid are used to model the flow and deformational behavior of articular cartilage. The frictional resistance of the relative motion of the fluid phase with respect to the solid phase is given by a linear diffusive dissipation term. The subchondral bony substrate is represented by an elastic solid. The three-layer model of articular cartilage is chosen because of the known histological, ultrastructural, and biomechanical variations of the tissue properties. The calculated flow field shows that for material properties of normal healthy articular cartilage the tissue creates a naturally lubricated surface. The movement of the interstitial fluid at the surface is circulatory in manner, being exuded in front and near the leading half of the moving surface load and imbibed behind and near the trailing half of the moving load. The flow fields of healthy tissues are capable of sustaining a film of fluid at the articular surface whereas pathological tissues cannot.

A three dimensional multi-segmental analysis of the energetics of normal and pathological human gait

Segmental mechanical energy changes were studied in normal adults as a function of walking speed and in a group of subjects with pathologically impaired gait walking at their normal speed to determine the usefulness of this parameter in evaluating locomotor dysfunction. Of particular significance, the degree of exchange between potential and kinetic energy within and between limb segments was quantitatively evaluated. Due to the nature of most pathological gaits, no assumptions were made to impose symmetry between the right and left extremities and the translational as well as rotational kinetic energy of each of the limb segments was computed in three dimensions. Additionally, the torso was modeled as a group of segments with distributed mass in contrast to the commonly employed concentrated point mass model. In toto, a three dimensional twelve segment energetic analysis of the human body was developed and employed. In normal subjects, this analysis suggests a greater exchange between potential and kinetic energy near individually preferred walking speeds. Patterns of energy change noted in those subjects with locomotor dysfunction varied with the type of pathological disorder.

A THREE DIMENSIONAL ENERGETIC ANALYSIS OF NORMAL AND PATHOLOGICAL GAIT

Publisher Summary This chapter presents a three-dimensional energetic analysis of normal and pathological gait. The study of the energetics of human motion from a mechanical point of view has been used by many investigators for the elucidation of the mechanisms of both normal and amputee gait. An assumption common to most of these studies has been that of motion restricted to the sagittal plane. In a study described in the chapter, the energetics of pathological gait was of particular interest. As subjects with neurologically based disorders such as cerebral palsy mylomeningocele and stroke whose gait pattern would differ greatly from the norm were to be included in the population to be studied, it was felt that a complete three dimensional analysis of gait energetics would be necessary. The source of kinematic data for this study was motion picture film taken at fifty frames per second. Three cameras were employed. With a computer-aided digitization scheme, the true three-dimensional coordinates of the anatomical points delimiting limb segments were obtained. The coordinates obtained in this way were relative to a fixed laboratory coordinate system whose positive x direction was perpendicular to the direction of walking, positive y direction is parallel to the direction of walking, and positive z direction is vertically upward. The chapter presents some of the results of an energetic analysis for a subject with myelomeningocele. A clinical evaluation of this subject has demonstrated weakness in the gluteus medius, hip flexor, and ankle plantarflexor muscles on the left side.