Susan A. Riedel

Standing postural stability assessment and signal stationarity in children with cerebral palsy

Standing postural stability signals of 60 children and adolescents were examined. The ages ranged from 5 to 14 years with both males and females participating in the study. Twenty subjects were previously diagnosed with cerebral palsy (CP); the remaining 40 were categorized as normal. Seven sway parameters were computed and analyzed for sensitivity. The frequency content of the sway signals was examined including statistical assessment of signal stationarity. The seven sway parameters adequately discriminated between the normal and CP populations under eyes-open and eyes-closed test conditions. In the frequency analyses the 20 s test epochs were generally the most stationary, although sufficient nonstationarity was demonstrated in all test epochs to warrant the application of nonstationarity analysis methods. >

Combined sagittal and coronal plane postural stability model.

We present a preliminary study of combined anterior posterior (AP) and medial lateral (ML) sway assuming a classic inverted pendulum with included subtalar movement. Based on a feedback control posture model in the sagittal plane, we have investigated parameters needed to model ML sway components. Center of pressure (COP) data was collected from a population of 8 normal adults (age 18 to 30 years) using a dual AMTI force plate system. Fourteen different sway metrics were calculated. The collected data was successfully compared to numerous simulations of the model where model parameters were varied and the goal was to reproduce both AP and ML components

An investigation of seated postural stability

Results of tests undertaken to identify which measures of seated posture control are most effective in two areas, distinguishing differences in the x and y direction control strategies for a given task and distinguishing differences in overall control strategies for pairs of different tasks, are presented. The test platform, calibration tests, test protocol, and data analysis method are described. The results of statistical analyses performed on the data are summarized.<<ETX>>

Force magnitude and spectral frequency content of heel strike during gait

A method of measuring and analyzing the magnitude and frequency content of reaction forces at six discrete points under the foot is described. A detailed analysis of the heel reaction force and frequency content characteristics during normal gait is provided. The study is part of a larger effort designed to investigate human bone remodeling under normal gravity (1G) conditions and while exposed to the hypogravic environment of manned spaceflight.<<ETX>>

Application of a bi-planar postural stability model in children with cerebral palsy

This study presents initial results from a bi-planar model used to investigate the neurological factors affecting balance deficits in children with diplegic cerebral palsy (CP). The model uses an inverted pendulum to describe sway in both the anteroposterior (AP) and mediolateral (ML) planes. The study presents Center of Pressure (COP) data from 17 children diagnosed with spastic diplegic CP using two standard AMTI force plates. Sway metrics in the time and frequency domains in the AP and ML planes were calculated and compared to simulations produced by the model. The proposed bi-planar model successfully reproduced sway signals acquired from experimental (clinical) data.

Using a bi-planar postural stability model to assess children with scoliosis

This study examines the postural stability of children with idiopathic scoliosis, using experimental data and a model of sway that includes mediolateral (ML) and anterioposterial (AP) components. The experimental data includes center of pressure (COP) measurements calculated from data acquired using two Advanced Medical Technology, Inc. (AMTI) force plates. Sway metrics are computed and compared with the model simulation, which successfully reproduced the clinical data from 16 children with scoliosis and 20 typically-developing children. This study is part of the first phase of a multi-year study designed to systematically assess whether fusing the spine to L4 in children with scoliosis has a significant impact on physical function and quality of life.

Signal stationarity in postural stability assessment of children

Research conducted to quantitatively evaluate the signal stationarity of the anterior-posterior (AP) and medial-lateral (ML) sway signal components so that the frequency content of those signals could be accurately assessed is summarized. The study focused on children and adolescents ranging in age from five to 14 years. The run test, which is used to identify an underlying time-varying trend in data that causes the probability of an event to change as time proceeds, and the reverse arrangements test, which is used to detect monotonic trends in data that contain significant frequency content below the run test cutoff, were used for data analysis. Results of the two tests are presented.<<ETX>>

Bi-planar postural stability model: Fitting model parameters to patient data automatically

Postural control can be a challenging task for many people, including those with cerebral palsy or idiopathic scoliosis. Assessment of postural stability can be used as one element of a comprehensive strategy to identify more efficient treatments and can provide a better understanding of postural control deficits. Several models and techniques have been developed to assess and understand postural imbalance. This study presents an improvement for an existing model that incorporates two algorithms designed to minimize a cost function.

Evaluation of upper extremity movement characteristics during standardized pediatric functional assessment with a Kinect®-based markerless motion analysis system.

A recently developed and evaluated upper extremity (UE) markerless motion analysis system based on the Microsoft® Kinect® has potential for improving functional assessment of patients with hemiplegic cerebral palsy. 12 typically-developing adolescents ages 12-17 were evaluated using both the Kinect-based system and the Shriners Hospitals for Children Upper Extremity Evaluation (SHUEE), a validated measure of UE motion. The study established population means of UE kinematic parameters for each activity. Statistical correlation analysis was used to identify key kinematic metrics used to develop automatic scoring algorithms. The Kinect motion analysis platform is technically sound and can be applied to standardized task-based UE evaluation while providing enhanced sensitivity in clinical analysis and automation through scoring algorithms.

Instrumentation for investigating seating stability in young children with lower limb spasticity

Instrumentation that will provide data to assist in the quantitative assessment of changes in seating stability after surgical intervention to relieve lower limb spasticity has been designed, constructed, and tested. Of particular interest in this study are measures of center of pressure while seated and standing, measures of upper extremity and lower limb forces exerted in a pull-to-stand task, and measures of upper extremity speed and range of motion attained in a tray-mounted switch-activation task. Data collected from the tests of seating stability, pull-to-stand, and supported standing are analyzed in both the time and frequency domains. In the time domain, two or three 30-s epochs are selected from each test to maximize the likelihood of attaining a stationary epoch.<<ETX>>