Development of prosthetic knee joint technologies for children and youth with above-knee amputations

Abstract

Mobility and participation in physical activity is of primary importance for children with limb absence or loss. A prosthetic knee joint is an essential facilitator of this, providing controlled articulation to enable sitting, standing, and natural, safe and efficient movements during mobility. Despite recent and notable improvements in adult above-knee prosthetic technologies, prosthetic knee joints for children and youth provide only very basic functions. As such, in this thesis, structured design processes and empirically-driven biomechanical models were used to aid the design and development of novel knee control systems intended to improve elements of prosthetic knee joint function, while quantitative gait analysis and self-report measures were employed to assess functional outcomes. In this thesis an examination of the design considerations for selecting the type of prosthetic knee joint mechanism is provided, and the important functional requirements of paediatric prosthetic knees established. From this, a basis for configuring a simple single-axis mechanism to provide the advantageous functions of more complex, multi-linkage mechanisms, and the important elements of stance-phase control function were established. Subsequently, a novel stance-phase mechanism is presented and evaluated as part of a crossover design field trial utilizing a self-report measure. The results of long-term field-testing are also reported. In this thesis, guidelines for obtaining reliable intra-session measures of impaired gait using quantitative techniques, provided the basis for the quantitative gait assessments that were used to compare the gait performance of the new stance-phase controlled prosthetic knee joint and conventional high-end paediatric knee joint technologies. The latter part of the thesis examined the other aspect of prosthetic knee joint control, namely swing-phase control. A unique technical solution is presented that circumvents some of the problems of conventional fluid-based swing-phase controllers. The performance of a prototype of the new swing-phase control mechanism is evaluated during gait, involving a sample of young individuals with above-knee amputations. The final chapter provides a discussion and summary of this work and its broader implications, including application to other patient populations.