<p>Background: Custom foot orthoses (CFOs) are effective in the prevention and treatment of lower extremity injuries (LEIs) and deformities by providing bony support, pressure/load redistribution and subjective comfort.&nbsp; However, the current design methodologies of CFOs are not efficient due to some problems: (1) the limited consideration of soft tissue deformation during geometrical measurement, (2) the limited choices of orthotic stiffness for patients (rigid or soft), and (3) subjective comfort is not considered during the measurement, which results in multiple design-to-deliver iterations.&nbsp; A new prescription methodology is required to determine the desired orthotic properties including geometry and impedance, which satisfy pressure/load distribution, subjective comfort and reduce iterations.&nbsp; Methods: A measurement device which provides an Interface with Tunable Ergonomic properties using a Reconfigurable Framework with Adjustable Compliant Elements (INTERFACE system) is developed.&nbsp; The geometry of the Medial Longitudinal Arch (MLA) support provided by the INTERFACE system can be adjusted to provide geometrical fitting for the plantar surface.&nbsp; Tunable stiffness mechanisms (TSMs) are integrated to provide local variation of stiffness.&nbsp; The Rapid Evaluate and Adjust Device (READ) Methodology, a human-in-the-loop approach, can therefore be implemented by adjusting the interface properties based on the pressure/load and subjective evaluation.&nbsp; The prototype of the INTERFACE system was fabricated to conduct the validation tests on 10 subjects, which recorded the interface pressure/load distribution and subjective feedback in different combinations of geometrical height levels (G1-G4) and stiffness levels (K1-K4).&nbsp; Results: The mean peak pressure (MPP) and interface force (IF) in the mid arch region increased with stiffness and geometrical height, whose significance has been demonstrated by the correlation analysis.&nbsp; Subjective comfort can be achieved with different combinations of geometry and stiffness; neither rigid nor soft were optimal outcomes.&nbsp; The geometrical height in the range of G2-G3 combined with stiffness level in the range of K2-K3 received high average subjective ratings among the subjects, which may be a preferred choice for majority of the population.&nbsp; The combinations G1&amp;K1 and G4&amp;K4 were scored less due to the inadequate support and excessive support they provide. &nbsp;The integration of adjustable geometry and stiffness makes it possible to fine tune the interface pressure/load and provides more stiffness options for physicians and patients to choose based on their needs or preference.&nbsp; Conclusion: The proposed INTERFACE system can be employed to (1) conduct the plantar measurement to obtain the desired orthotic properties which satisfy objective and subject requirements while reducing the design-to-deliver iterations, and (2) improve the communication between physicians, subjects and fabricators on CFO specification through the READ methodology.</p>

Design and Development of a Reconfigurable and Adjustable Compliance System for the Measurement of Orthotic Properties

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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