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Dissertation
Intersegmental dynamics analysis of the effect of an ankle foot brace on walking
Doctor of Philosophy (Ph.D.), Drexel University
May 2002
DOI:
https://doi.org/10.17918/00009681
Abstract
Mechanisms of molded ankle foot orthosis (MAFO) function are unclear. A MAFO has a direct effect upon the pathologic structure of interest and an indirect effect on the remainder of the kinetic chain. Neither effect is objectively discernable with conventional inverse dynamics. The primary purpose of this research was to develop and apply analytical techniques to objectively assess the effects of a MAFO on the pelvis, ipsilateral hip and knee during gait. The correlated and compensatory postures and movements selected by subjects in response to the brace were investigated. Intersegmental dynamic analysis (IDA) was employed to calculate stance phase hip and knee flexion and forward progression acceleration components due to the hip, knee, ankle, and brace moments. IDA was robust for the following foot-floor interaction models: no translation (1) but rotation about the center of pressure under the foot, (2) but rotation about the foot center of mass, and (3) and no rotation of the entire foot. The center of pressure constraint was used for subsequent analyses. Walking data were collected from free and locked brace conditions from three healthy subjects. A model was used to separate the ankle moment into brace and physiological components. Comparison of IDA calculated acceleration components between brace conditions was sensitive to joint kinetic variability and stance phase timing determination. Criteria for consistent stance phase selection and ensemble averaging of the output accelerations accounted for some of this variability. Brace effects occasionally contradicted conventional clinical wisdom. During weight acceptance the locked brace accelerated the knee and hip into flexion (instability). Small changes in body positioning significantly modulated the effects of the brace and those of compensatory changes in joint moments nearly 40% of the time. Accelerations produced by the ankle moment were most sensitive to modulation by body position. A synergy index was proposed to quantify movement inefficiency. The index was sensitive to minor brace-related changes. Results clarify mechanisms by which a MAFO can control remote segments and joint moment roles in compensation. The techniques and analyses developed and used in this work can clarify the clinical effects of brace function on individuals with pathology.
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Details
- Title
- Intersegmental dynamics analysis of the effect of an ankle foot brace on walking
- Creators
- Mukul C. Talaty
- Contributors
- Rahamim Seliktar (Advisor) - Drexel University, Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xii, 150 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- School of Biomedical Engineering, Science, and Health Systems (1997-2026); Drexel University
- Other Identifier
- 991021888965504721