Computer Aided Engineering in the Foot Orthosis Development Process

• Main Author: Lochner, Samuel Jewell
• Language: en
• Published: 2013
• Subjects: Finite Element Analysis; Computer Aided Design; Foot Orthosis; Parametric Design; Morphing; Additive Manufacturing
• Online Access: http://hdl.handle.net/10012/7776

An orthosis, or orthotic device is used to straighten or correct the posture of part of the body. A foot orthosis (FO) is the subject of study for this dissertation. A FO is situated between the foot and the midsole of the shoe and replaces the insole. Foot orthoses (FOs) are intended to prevent or aid in the recovery of injury by acting to redistribute pressure experienced by the plantar surface of the foot as well as cause adjustments to the relative positions of the foot's bones during standing and gait. Traditional methods for developing a FO require extensive skilled manual labour and are highly dependent on subjective input. Modern FO development methods have sought to address these issues through the use of computer driven technological advancements. Foot scanners record geometry, computer aided design (CAD) software is used to develop the FO geometry, and automated manufacturing tools are used to either fabricate the FO or fabricate a mould about which the FO can be formed. A variety of modern solutions have successfully automated the process, however, it remains highly subjective. Skilled manual labour has merely been replaced with equally subjective skilled computer labour. In particular, adjustments to the foot are made with basic deformation functions to the static surface foot models generated by modern digitizers. To improve upon this, a model that describes the mechanics and properties of the various tissues of the foot is required. Such a model will also be useful for validating and optimizing FO designs prior to fabrication through simulation of weight-bearing conditions. Given the deformable characteristics of the tissues of the foot, the finite element (FE) modeling method is appropriate. The FE foot model has become a common medical and engineering tool in recent years. Its application, however, has primarily been limited to research as few clinical applications warrant the development cost. High cost stems from the MRI or CT scan and the skilled labour required to assemble the model for FE analysis. Consequently, the FE modeling approach has previously been out of reach for the application of FO development. The solution proposed and implemented was to map a detailed generic FE foot model to an inexpensive surface scan obtained from a modern digitizer. The mapping accurately predicted anatomical geometry and resulted in simulation models that can be used in the FO development process first to carry out postural adjustments prescribed by a practitioner and second in a validation step where a FO design can be tested prior to fabrication. In addition to simulation tools, novel complementary tools were developed for designing and fabricating FOs. The simulation, design, and fabrication tools were incorporated into a novel, seven step FO development process. The proposed process is beneficial to FO development as it reduces the required subjective input from practitioners and lab technicians and allows for the validation of potential FO designs prior to fabrication. Future work is required to improve computational efficiency of the FE foot models and to fully automate the process to make it commercially viable. In addition to FOs, the proposed approach also presents opportunities for improving other orthoses and prostheses for the human body.