Evaluating the Effects of Powered Prostheses on Walking Biomechanics In and Out of the Lab

Abstract

Powered ankle prostheses aim to replicate the biological ankle function for individuals with transtibial amputation. The effects of powered prostheses on gait have been experimentally quantified in several studies. The findings are non-universal and potentially dependent on user characteristics. Disparate responses to the powered prosthesis among users point to unanswered questions regarding the fundamental biomechanical effects of the device. Additionally, it is unknown how powered prostheses impact daily function. To address these gaps in knowledge, I investigated various biomechanical and clinical outcomes of the powered prosthesis in the laboratory and in the users’ everyday lives. My research can be broken down into two approaches: experimental analyses of functional capacity and examinations of functional performance in everyday life.

To assess functional capacity in the lab, I first explored users’ neuromuscular adaptations to the powered prosthesis (Chapter 2). Specifically, I quantified changes in lower-limb muscle activations and their relationships with changes in metabolic cost. This aim revealed the potential importance of effective residual limb stabilization as a contributor to metabolic reductions. Second, I sought to quantify fatigue-related compensations in walking with the powered prosthesis (Chapter 3). While the powered prosthesis did not improve the user’s endurance, there were differences in hip joint compensation strategies when wearing unpowered and powered prostheses.

I then developed methods to bring gait analysis out of the lab, to assess functional performance in daily life. I first explored the use of portable GPS and IMU sensors to quantify functional mobility in everyday walking (Chapter 4). Through this work I demonstrated the clinical viability of estimating cadence and walking speeds in different real-world environments. I then applied these techniques to assess changes to the volume and characteristics of walking with a powered prosthesis in daily life (Chapter 5). Further, I examined the relationships between capacity in the lab, performance in daily life, and the users’ perceptions of mobility. Lastly, I examined potential implications of the powered prosthesis on trips and falls in daily life (Chapter 6). In this study, I applied a novel method for using IMU signals to estimate minimum toe clearance in daily life. Findings from Chapters 5 and 6 suggest there were no universal powered prosthesis-related changes to gait in daily life.

Together, these works add to the existing body of literature and reinforces the notion that the benefits of the powered prosthesis are non-universal and subject-specific. Chapters 4 through 6 specifically represent a meaningful first step toward an evidence-based approach in the prescription, design, and assessment of powered prostheses.