Date of Award

Fall 2015

Document Type


Degree Name

Master of Science (MS)


Biomedical Engineering

First Advisor

Wang, Mei

Second Advisor

Jeutter, Dean C.

Third Advisor

Voglewede, Philip A.


The needs of an increasingly young and active orthotic patient population has led to advancements in ankle foot orthosis (AFO) design and materials to enable higher function. The Intrepid Dynamic Exoskeletal Orthosis (IDEO) is a custom energy-storing carbon fiber AFO that has demonstrated improved clinical function, allowing patients to return to high-intensity activities such as sports and military service. An improved understanding of AFO mechanical function will aid prescription and fitting, as well as assist in design modifications for different patient populations. This study investigated the mechanical properties of AFOs, specifically structural stiffness, rotational motion, and strut deflection, to discern design characteristics contributing to increased functional outcomes. Seven AFOs of different designs and materials were tested under cyclical loading to characterize their mechanical properties. These AFOs were fitted about a surrogate limb and underwent pseudo-static compressive testing using a materials testing system and motion analysis. Acquired data included: compressive force, vertical displacement, kinematic data, and ankle rotation. Testing was conducted at discrete orientations and loads corresponding to the latter sub-phases of stance: midstance, terminal stance, and pre-swing. The compressive stiffness, posterior strut deflection, and rotational motion of the various AFOs, as well as the ankle range of motion (ROM) of the surrogate limb, were characterized. The deformation of the various AFO designs during loading differed greatly, influencing the observed mechanical behavior. Traditional thermoplastic and carbon fiber designs deformed at the malleolar flares or rotationally at the ankle, demonstrating low proximal rotational motion of the AFO and large surrogate ankle ROM. The mechanical response of the IDEO was unique, with large deflection observed along the posterior strut, minimal footplate deformation, greater proximal rotational motion, and minimal ankle ROM. This design incorporates stiffer materials for fabrication, increasing the potential for energy storage, while restricting ankle motion. Enhanced knowledge of the mechanical behavior and energy storage/release mechanism may improve prescription, custom design and fitting of the IDEO.