Assessment of gait using components of the ground reaction force vector

The design of a functional assessment and gait analysis facility for rehabilitation studies

A general functional assessment and gait facility has been designed for use in all aspects of measurement of handicap. The functional assessment course contains various features to assess the ability of subjects with different handicaps to sit, take off and apply orthotic or prosthetic devices, climb ramps and steps, negotiate corners, and doors with different locking and opening mechanisms. Incorporated in the middle of the walking section of the course is a force plate to assess the mechanical function of orthoses or prostheses by a force vector visualization system. A visual analogue scoring system of the quality of performance of the various tasks encountered on the functional assessment course as well as the freely selected speed and fastest walking in a straight line has been adopted. This visual analogue score is marked after analysing the video record obtained from a mobile colour camera. The doors, ramps and walking area are wide enough to assess wheelchair use. We have adopted a 'gait graph' for the gait analyses using a 10m straight walkway and measuring the temporal parameters at free speed walking and the fastest walking speed. Energy cost is measured using heart rate monitoring by telemetry on the functional assessment course and during gait analysis.

It is proposed to use this facility for the assessment and management of lower limb bracing in children, patients undergoing corrective surgery on the lower limb and for wheelchair users.

Time-domain analysis of foot-ground reaction forces in negotiating obstacles

In recent years there has been increasing interest in the kinetic and kinematic characteristics of adaptations to obstacles and the contribution of these measures to understanding processes of gait control. This study investigated the lead and trail foot kinetic characteristics of unobstructed walking and stepping over obstacles for unimpaired, healthy adult males (n=6) and females (n=6). Two strain-gauged force platforms were employed during free-speed ambulation and stepping over obstacles adjusted to 10, 20 and 30% of leg length. In stepping over obstacles subjects increased obstacle-crossing step lengths and reduced obstacle-crossing speed as a function of obstacle height. The force-time data revealed that, compared with the lead foot, the trail foot generated greater vertical and anterior-posterior force during the push-off/propulsive phase across all obstacle conditions, had lower vertical peak force during mid-stance and produced greater vertical and anterior posterior impulses. While maximum propulsive force increased with obstacle height, its timing in the normalized step cycle was uninfluenced by height. Collectively, the results showed that the constraints of stepping over obstacles imposed different kinetic demands on the lead and trail foot; this is reflected in a complex interaction of braking and propulsive forces. Regulation of the step in this task was not mediated by a single parameter, such as vertical impulse. Copyright 1997 Elsevier Science B.V.

A microcomputer-based video vector system for clinical gait analysis

A microcomputer-based video vector system has been developed to display the resultant ground reaction force vector on a television image of the subject in real-time. For each television field the force platform signals are acquired and processed and the resultant force vector superimposed on the video image of the walking subject. The force platform results are stored on disc and the composite video signals recorded on video tape for further analysis. The system is easy to set up and use and the results can be readily interpreted. The external moments produced at the joint centers by the ground reaction forces can be observed visually and, if required, quantification of the external moments can be achieved following data collection. The spatial resolution of the system is 0.342% vertically and 0.156% horizontally. The force vector visualization technique has routine applications in orthotics and prosthetics. It is also a useful technique for the teaching of biomechanics.

Instrumentation used in clinical gait studies: a review

This paper reviews the currently available instrumentation used for gait studies and discusses the clinical suitability of the various methods of recording gait parameters. Most of the presently available motion analysis systems appear to be more suited to research than to the routine clinical situation. However the video vector visualization technique appears to be the most useful clinically since it produces a real time display, is simple to operate and interpretation of the data is easier than other systems available. Some further development of the video vector visualization system is necessary to improve its accuracy and to produce quantitative information.

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.

Evaluation of equine locomotion during different degrees of experimentally induced lameness. II: Distribution of ground reaction force patterns of the concurrently loaded limbs

Force plate and high-speed film data from a group of six walking horses were used to study the distribution of the ground reaction forces (GRF) of the concurrently loaded limbs. Three different degrees of supporting lameness were induced in a forelimb or a hindlimb using modified horse shoes. In all experiments the alterations in the distribution in the transverse horizontal GRF (Fx) were small. During unilateral forelimb lameness, the decreased longitudinal horizontal GRF (Fy) was compensated by an increase of the Fy forces of the contralateral forelimb and the ipsilateral hindlimb. The decreased vertical GRF (Fz) of the lame limb was compensated by an increase of the Fz amplitudes of the contralateral forelimb during the swing phase of the lame limb and increased Fz forces of both the diagonal and the ipsilateral hindlimbs during the stance phase of the lame limb. During unilateral hindlimb lameness the decreases in the deceleration Fy forces of the lame hindlimb were mainly compensated by increased propulsion forces in the contralateral hindlimb and small increases of the Fy forces of both forelimbs. The decreased Fz forces of the lame hindlimb were mainly compensated by increased Fz forces of the diagonal forelimb and smaller increases in Fz forces in the ipsilateral forelimb during the stance phase. During the swing phase of the lame hindlimb small compensatory increases were found in the contralateral hindlimb. Decreased peak amplitudes and impulses in the lame limb, and compensatory increases in the two or three concurrently loaded limbs, resulted in significant decreases in left-to-right symmetry percentages between forelimbs as well as hindlimbs during the different degrees of one limb lameness.

Quantification of equine ground reaction force patterns

A method was developed to quantify the ground reaction force pattern of the horse. A number of selected force amplitudes and peak-time positions in the normalized stance phase of left and right contralateral limbs were used to calculate symmetry indices. Data from each limb were compared with those of a 'standard horse' resulting in limb indices. The combination of amplitude and peak-time symmetry and limb indices yielded one H(orse)INDEX. These indices were useful for comparison of different horses and for the evaluation of lameness and treatment.