Biomedical subjects

P A Costigan

Publications and source records attributed to P A Costigan.

8 recordsLinked to original sources

PubMed1999

The effect of segment parameter error on gait analysis results.

The extent to which errors in predicting body segment parameters (SP) influence biomechanical analysis of human motion is unclear. Therefore, the current study quantitatively evaluated the differences in SP estimates using literature predictive functions and computed the effect of SP variation on the kinetic output of walking. For a group of 15 young males, significant differences (P<0. 05) were observed between SP estimates for the leg and thigh using the literature predictive functions, with mass and moment of inertial values differing by more than 40%. Using kinematic and ground reaction force data collected for each subject while walking, inverse dynamic analysis was performed iteratively to compute hip forces and moments while simultaneously varying SP values over nine intervals within +/-40% of a baseline value. SP variations were found to significantly affect (P<0.05) most of the kinetic estimates produced, particularly those taken during the swing phase. However, the magnitude of these effects was generally less than 1% of body weight. The data from the current study allows researchers to estimate the errors in kinetic measures due to SP variation. The results also indicate that the accuracy of SP prediction should be of concern in biomechanical research particularly for open chain and high acceleration activities. Further study is necessary to identify the importance of SP variation on other motion skills.

Biomechanical Phenomena↗

PubMed1993

A procedure to validate three-dimensional motion assessment systems.

The automation provided by computer-assisted motion-tracking systems allows for three-dimensional motion and force analysis. These systems combined with mathematical modelling are able to analyse quickly the intricate dynamics of human movement. Understanding the limitations of human motion analysis as performed by the present measurement techniques is essential for proper application of the results. It is necessary to validate the analysis system prior to subject testing. This paper provides a validation of an optoelectric motion-tracking system used in a dynamic knee assessment study. While the validation is shown with one particular system only, it is suggested that all systems used in two- or three-dimensional motion analysis should be tested similarly in the actual configuration used. Three simple mechanical representations of the human knee have been used in this validation. The first model provided an understanding of the source and behaviour of the error introduced to the accuracy of defining a vector between the recorded coordinates of two markers. The other two models investigated the effect of processing methods specific to the knee analysis project. Separating the markers by at least 180 mm is recommended to produce stable vectors. Relative joint angles could be calculated in all three planes of rotation. The error in calculating flexion and longitudinal rotation was less than 2.0 degrees, while calculating adduction introduced errors of 4.0 degrees. Force calculations were found to be within 8%. The system behaviour was found to be consistent within the calibrated volume about the force platform. Simple mechanical models combined with straightforward procedures can provide validation in terms of clinically relevant parameters.

Algorithms↗

PubMed1993

An integrated procedure to assess knee-joint kinematics and kinetics during gait using an optoelectric system and standardized X-rays.

This paper describes a 3-D gait analysis system, which combines optoelectric motion tracking and a standardized X-ray procedure, to calculate the net knee-joint forces and moments of a normal subject group during walking. The optoelectric system collects kinematic data from infra-red LED markers placed at selected skin surface locations and projecting probes attached to the lower limb. A standardized X-ray procedure is used to move surface markers into their designated bony landmarks based on individual bone structure, which reduces the error caused by uncertainty of skin-surface marker locations. Based on moved-in marker information, different joint coordinate systems are proposed for kinematic and kinetic analysis of the knee joint. Normalized data of knee angles, net reaction forces and net moments from 35 young, normal subjects are presented.

Adult↗

PubMed1992

Semiautomatic three-dimensional knee motion assessment system.

A semiautomatic three-dimensional knee motion assessment system has been developed based on an optoelectric motion tracking system connected to an IBM-compatible computer. Critical decisions made in implementing the software component of the system include the modelling of the thigh and lower leg segments, calculating the knee angles, reaction forces, and moments; the file structure used and the format of the programs used to process the data are outlined. Once the subject-specific data have been collected, the system of programs requires no other user-intervention during processing. Also, selected curve parameters are automatically extracted from the output and combined with the subject-specific data that include precision X-ray and anthropometric data, which are all added to a knee motion assessment database. The automated portion of the system frees the experimenter from data processing and allows concentration on data analysis.

Biomechanical Phenomena↗

PubMed1987

Mechanical energy patterns in gait of cerebral palsied children with hemiplegia.

The mechanical energy costs of walking were studied in 10 cerebral palsied children with hemiplegia to determine whether their values were substantially different from normal and, if so, to discover the movements that were responsible. A two-dimensional, sagittal-plane cinematographic analysis of the subjects' normal walking was undertaken. This technique provided continuous information about the mechanical energy costs of the whole body and each of its parts, the energy types involved, and the amounts of energy conserved. In most cases, the energy costs were above normal and were attributable to poor patterns of exchange between the potential and kinetic energy types of the head, arms, and trunk segment; to very low levels of kinetic energy that precluded exchange; or to both. We concluded that attention should be directed to restoring the sinusoidal pattern of motion and to the fluctuating speeds during each gait cycle when energy costs are a therapeutic consideration.

Adolescent↗

PubMed1987

Prediction of trunk muscle areas and moment arms by use of anthropometric measures.

The prediction of five internal muscle variables extracted from computed tomography scans was attempted using 27 anthropometric variables. Stable regression equations are presented for the prediction of the cross-sectional area of the rectus abdominis, psoas, and erector spinae, as well as for the moment arm of the erector spinae. No stable regression equation was found for the prediction of the moment arm of the rectus abdominis, and the results indicated that the method was group dependent. These findings have implications for human modeling studies that use estimated parameters for the internal muscle variables.

Abdominal Muscles↗

PubMed1987

Trunk muscle balance and muscular force.

An investigation of the absolute strength of the human muscle was carried out on the in vivo erector spinae muscle using magnetic resonance tomography coupled with dynamic muscular testing. The absolute strength of the erector spinae was calculated to be 48 N/cm2. The area of the rectus abdominis was 15.1 cm2, and the area of the erector spinae was 54.5 cm2. The internal moment arm for the rectus abdominis and erector spinae muscles was 7.04 and 5.64 cm, respectively. The static force measures showed the trunk extensor moment to be only 30% greater than the flexor moment. The difference is discussed in terms of the absolute strength of muscle, and other anatomic factors.

Abdominal Muscles↗

PubMed1986

Mechanical energy of walking of stroke patients.

The mechanical energy costs of walking have been studied in ten stroke patients with hemiplegia. A two-dimensional sagittal plane cinematographic analysis of two strides of the subjects' normal walking was undertaken, yielding continuous information about the mechanical energy costs of the whole body and each of its parts, about the energy types involved, and the amounts of energy conservation. The large head, arms, and trunk (HAT) were found to dominate the total pattern. Three major disturbances were seen. In contrast to normal subjects who show energy-conserving negatively correlated potential and kinetic energy curves for the HAT, the subjects who demonstrated the first disturbance showed gross irregularity of the curves, with almost no opportunity for exchange between energy types. In a second disturbance the curves of the HAT showed some energy-conserving portions, but levels of kinetic energy curves were low, resulting in little energy exchange. In the third disturbance, some exchange was evident, but the pattern was dominated by potential energy changes in the form of a single large rise and fall, coinciding with swing phase of the affected leg. Each of these disturbances would require a different approach to treatment. Although mechanical energy analyses do not reflect certain energy costs, such as the effort required to hold the body up against the pull of gravity and that used in contracting antagonist muscles, they could be of considerable assistance in pinpointing costly variations in energy patterns during walking and in determining appropriate treatment procedures.

Adult↗