UC Davis

There are many complex factors that will affect whether children with a unilateral congenital below-elbow deficiency (UCBED) will use a prosthetic limb to interact within their environment. Children face higher rates of prosthesis abandonment at 35-45%, compared to adults at 23-26%. Ultimately, for a child to wear and use their prosthesis, it must facilitate the effective performance of daily tasks and promote healthy social interactions. Although beginning to emerge, multiarticulate upper limb prostheses for children remain sparse despite the continued advancement of mechatronic technologies that have benefited adults with upper limb amputations. In contrast, pediatric devices typically provide a single open-close grasp (if a grasping function is available at all) and often offer non-anthropomorphic appearances, falling short of meeting the criteria essential to prosthesis adoption. Moreover, this population presents unique challenges, as they were born never having actuated a hand, and with forearm musculature that never fully developed–a stark departure from those with acquired limb absence. Due to the lack of investigation into how children with UCBED actuate their muscles coupled with the limited advancement in pediatric upper limb devices, the effective translation of dexterous prostheses remains a prominent issue. This dissertation builds the fundamental groundwork necessary for the effective translation of dexterous prosthetic hands for children with UCBED. It begins with an examination of how typically developing children use their hands to interact within their environment to inform dexterous device development (Chapter 3). Here we found that children, like adults, use a small subset of hand movements to perform object manipulation in home settings. Subsequently, a child-sized dexterous prosthetic hand was developed to serve as a dedicated research platform (Chapter 4). A thorough benchmark of this research platform was performed to validate its functional grasping ability and it was shown to be a robust device within a research environment. Prior to using this device, a cohort of children with UCBED were recruited, and an in-depth analysis of state-of-the-art prosthetic control, namely surface electromyography (sEMG) as a measure of affected muscle electrical activity, was conducted (Chapter 5). Upon investigation, participants exhibited a measurable degree of consistency and repeatability of their affected musculature as obtained through sEMG when they attempted missing hand and wrist movements. Furthermore, through tuning features, i.e., sEMG characteristics, and classification algorithms, we found a novel generalized feature set that provided increased classification to decode hand motor intent (Chapter 6). Moreover, we benchmarked the real-time performance of these children to execute hand movements, adding a translational dimension to our findings (Chapter 7). This forms a crucial foundation for understanding muscle actuation and use of advanced prostheses among children with UCBED. Through this work, we have laid the foundation to understand the capacity of children with UCBED to control their affected musculature. This begins to address the translational aspect of child-size dexterous upper limb devices and has the potential to remove barriers to device acceptance.