Zaino CA
Westcott SL, Miller F, Alexander M, Thorpe D.
Medical College of Pennsylvania and Hahnemann University,
Philadelphia, PA 19102
INTRODUCTION: Children with cerebral palsy often present with problems in maintaining postural stability during functional activities. Physical and occupational therapists focus many treatment hours on modifying the ability to maintain and recover balance. If these treatments could be better focussed on the individual child's specific problems with balance, the treatments might have greater efficacy. One approach to evaluation of postural stability is to adopt a systems theory of motor control when defining the construct. This implies that there are many systems involved in maintenance of postural stability. Problems with balance may occur in any system, therefore each systems must be evaluated to isolate where deficits exist. There are at least three primary systems involved with postural stability: 1) biomechanical system, 2) sensory system, and 3) motor system. Several assessments exist for the biomechanical components and tests are in development to examine sensory components related to standing balance. In terms of the motor system, researchers have suggested that there are synergies of muscle activations that are used to maintain or recover balance. These synergies have been documented after specific perturbations in standing. Clinical methods of evaluating motor coordination during maintenance of postural stability has primarily consisted of non-standardized observations of reactions to tilt perturbations. In an effort to develop a standardized assessment of motor coordination of balance responses during standing and to examine these responses during a functional task rather than after an external perturbation in both children with and without cerebral palsy, the following research is being undertaken.
MATERIALS AND METHODS: First to examine interrater and test-retest reliability of the electromyographic motor coordination measurement, a sample of convenience of 30 children with and without cerebral palsy is currently being recruited from families involved in the Orthopedic Clinics of the A.I. duPont Institutes and families living in the Delaware valley. The subjects are asked to stand and reach forward from four different surfaces conditions and to step to reach from two surface conditions for a toy placed on a shelf. Preamplifier surface electrodes are placed over five leg muscle groups (the anterior tibialis bilaterally, the quadriceps, hamstrings, and gastrocnemius unilaterally, and the deltoid of the reaching arm) to record the prime mover and the postural component muscle groups. The muscle activity is recorded for 10 seconds starting from an auditory cue to reach. Data is collected on a computer for reduction and analyses. Three raters, (the computer, and two different people) examine the traces of the six muscle groups to determine the onset latency for each muscle group. To examine test-retest reliability, three trials are recorded of each condition each test session, and the subjects are recorded one session, then again one week later. The subjects are also asked to complete three tests involving functional mobility; 1) the Bruininks-Oseretsky Test of Motor Proficiency, 2) the Timed Up and Go, and 3) the Pediatric Evaluation of Disability Index.
RESULTS: To date, the data from 2 adults (age 33 & 41 years), 3 children (age 7-12 years) without cerebral palsy, and 2 children (age 10 years) with cerebral palsy have been analyzed for interrater reliability. The three trials from two conditions, stand and reach on the floor, and step to reach on the floor at the test and retest times for all six muscle groups combine to make 90 cases. Interrater reliability of all three raters determined from Intraclass correlation coefficients (3,1), by muscle group, were .48, .51, .58, .63, .64, and .80. When the two people raters are compared, the coefficients were .88, .50, .74, .77, .79, and .90 for the same respective muscle groups.
DISCUSSION: The lowest coefficients of the people raters with the computer were on the deltoid muscle. For the people raters, this muscle had one of the highest reliability coefficients. Because the arm is relatively quiet prior to the reach, the computer appears to pick minor increases in activity with earlier onset times then what appears to be the muscle activity associated with reaching. Comparisons of the two people raters scores were lowest on the quadriceps muscle group. This muscle group has the most constant low level activity which makes it difficult to determine an onset time.
CONCLUSION: The computer program does not adequately determine appropriate onset latencies, however two people raters do have adequate reliability. In order to obtain reliable and accurate measurements, a person will need to scan and adjust the computer scores prior to further analyses. Future analyses include test-retest reliability within a session, i.e. between three trials, and between the two sessions. Following this, if the onset latencies of postural muscles during stand and reach appear to have some consistency, the responses from a larger group of children with and without cerebral palsy will be described and contrasted. This information should provide insight into the motor coordination related to standing balance during reaching and spark the development of new treatment techniques for improvement of postural stability in children with cerebral palsy.
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