Brian A. Knarr, Ph.D. - US grants

Abstract The impact of assistive device use (handrails, canes, etc.) on patient outcomes and rehabilitation is unknown. Consequently, clinicians must make a decision whether to encourage or discourage use during training without understanding the implications for patient outcomes. The objective of our research is to determine the impact of assistive device use during treadmill and overground walking post-stroke. As an initial step, this project will determine the effects on an individuals paretic-side propulsion, a commonly targeted variable in post-stroke gait rehabilitation. The aims of this study are to identify changes in propulsion with (1) handrail use during treadmill walking and (2) cane use during overground walking. We hypothesize that assistive device use will modify propulsion but that changes in propulsion, and how individuals achieve these changes, will depend on how the device is used (i.e. light or self-selected support). Furthermore, we hypothesize that the impact of assistive device use will vary as a function a subjects level of movement impairment. To assess our aims, subjects post-stroke will undergo gait analysis sessions with three-dimensional motion capture during treadmill (Aim 1) and overground (Aim 2) walking with different assistive device use conditions (no use, light support, and self-selected support) for a total of six walking conditions. Paretic-side propulsion (primary outcome) as well as key contributors to propulsion (secondary outcomes: paretic ankle moment, trailing limb angle, muscle activation and plantar flexor muscle function) will be analyzed across walking conditions to explore the kinematic and kinetic changes in gait dynamics as a result of assistive device use. Finally, we will determine the relationship between clinical assessments of function known to be related to assistive device use (self-selected walking speed, SIS Mobility) and changes in the primary and secondary measures of propulsion. By understanding the specific impact of assistive devices on propulsive force, a key variable in increasing walking function, clinicians can make informed decisions regarding assistive device use during rehabilitation for both patients that use assistive devices in their daily lives and those who do not.

MAPRO Project Summary For the Phase II COBRE, we are strategically positioned to propose the development of research cores that will extend, enhance, and strengthen our COBRE infrastructure and research efforts. Therefore, we propose to establish the Machining and Prototyping Research Core (MAPRO). MAPRO will provide access to state of the art manufacturing equipment and highly skilled personnel for the design, fabrication, and maintenance of cutting-edge research devices to support human movement related research. Additionally, MAPRO will provide mentorship and device design consulting to all investigators, especially for investigators who do not have specific expertise in physical manufacturing or software development for custom devices used in human subject research. This training is crucial for the progression of human subject research, as an understanding of new technology is fundamental for a technology?s adoption. By definition, performing innovative and impactful research requires tools and devices that do not already exist. Recognizing the high reliance on multidisciplinary skills to create modern devices that involve complex hardware, electronics, and software solutions, MAPRO offers expertise across the spectrum of modern device design for investigators. The MAPRO Core has three aims: (1) To provide centralized resources for the design and fabrication of custom research devices and instrumentation. (2) To provide mentorship and training on cutting-edge manufacturing equipment, techniques and software that can be used to create new and innovative research devices and clinically translatable products. (3) To establish MAPRO as a leading resource for the University of Nebraska at Omaha, Nebraska, the Great Plains, and beyond for the development of new and innovative devices to treat and prevent movement related disorders.

By the year 2050, it is expected that 3.6 million people will have upper limb amputations. Despite the increase in functionality provided by prostheses, a recent study found that 45% of children with upper limb deficiencies reject their prosthetic device. There is a critical need to determine quantitative parameters to assess prosthesis usage and movement variability to provide the fundamental information required to objectively quantify prosthesis usage and associated benefits. Additionally, the literature which describes training paradigms and behavioral interventions for children with congenital upper limb deficiencies is sparse. Training paradigms for acquired amputees and stroke survivors focus on inter-limb transfer paradigms to transfer motor repertoires from the non-affected limb to the affected limb. This dynamic approach provides useful tools for the assessment of limb coordination and associated variability especially when examining inter-limb coordination and gross manual dexterity. Thus, the purpose of this project is to assess temporal synchrony of hand movement and gross manual dexterity after completing an 8-week home intervention. We hypothesized that bimanual coordination will significantly increase temporal synchrony of hand movement and there will be an increase in unilateral gross manual dexterity after the completion of an 8-week home intervention. Specific aim #1: Determine the differences temporal synchrony of hand movement and gross manual dexterity in children with unilateral congenital partial limb loss and a control group. We will analyze a subgroup of 10 research participants already enrolled in the parent grant. Specifically, two groups of children between 7 and 12 years of age.; children with unilateral congenital upper-limb reductions (n=5) and an age-and sex-matched control group of typically developing children (n=5). Specific aim #2: Determine changes in temporal synchrony of hand movement and gross manual dexterity after an 8-week home intervention. Research participants will be asked to attend a total of 3 sessions (one measurement session, and two testing sessions) following the protocol of the parent grant. Children will attend an initial measurement session to take a 3D scan of the affected and non-affected upper limbs as well as several anthropometric measurements. During this session, three pictures of the upper limbs will be taken which will also be used to verify the fit the prostheses in a process previously validated by our research team.

The use of novel tools such as prostheses involves the neural processes of embodiment and ownership of the tool, allowing the brain to incorporate the device into its internal model. Currently, a gap exists in the literature that describes how these processes effect the rejection or acceptance of upper limb prostheses. Prosthetic simulators are tools used within rehabilitative settings that aid amputees with becoming more familiar with their prosthetic device with the unaffected limb or have been used to investigate learning paradigms. However, it is unknown if these simulators truly emulate the neural and muscular responses of using an actual prosthesis. Neural imaging through functional near-infrared spectroscopy (fNIRS) in parallel with muscle activity readings with the use of electromyography (EMG) from the effector muscles during the use of a prosthetic simulator in typically developing population would allow for a physiological description of novel tool use, both within the brain and end effector. This data would aid in elucidating the effects of using a novel tool on brain activation, as well as differences between simulator use and prosthesis use. The objective of the study is to determine differences in lateralization of brain function during a gross manual dexterity assessment using prosthetic simulators and 3D printed prostheses. Our hypothesis is that ipsilateral hemispheric activity and end-effector co-contraction will be significantly increased during the use of the simulator in the non-preferred hand of the typically developing participants. Secondly, that prosthesis users will show significantly more ipsilateral dominance and co- contraction compared to the simulator users and typically developing controls. Should our hypotheses prove correct, we may use the knowledge gained to better inform rehabilitative programs for children receiving prostheses and create more effective simulators. To test our hypotheses, we formulated two specific aims: Specific Aim 1: Determine the differences in primary motor cortex hemispheric activity during the performance of motor tasks using upper-limb prosthetic simulators in typically developing children, compared to children using upper limb prostheses. We will analyze a sub-group of 20 participants already enrolled in the parent grant (10 typically developing and 10 prosthesis users) from 7 to 12 years of age and monitor their primary motor cortex activation during a gross manual dexterity test. Specific Aim 2: Determine the changes in co-activation index, as measured by the co-contraction of the extensor digitorum and flexor carpi ulnaris, during a maximal voluntary isometric contraction.

In the United States, more than 541,000 individuals live with congenital upper-limb reductions or amputations. Worldwide estimates for upper-limb congenital reductions range from 4-5/10,000 to 1/100 live births. The use of body-powered upper-limb prostheses helps children with upper-limb reductions to engage in functional activities that are fundamental to normal growth and motor development. However, the development of prostheses for children is complex due to their rapid and continuous growth. Up to 58% of children with upper-limb reductions reject or abandon their prosthesis due to excessive weight, lack of visual appeal, limited function and complexity of control. 3D printed prostheses provide a cost-effective solution to the development of light-weight, customized and visually appealing prostheses for children, potentially encouraging use. Theoretically, the use of a prosthesis may lead to an enlargement of the primary neuronal networks located in the cortical area involved with motor control of the affected limb. Ultimately, this might lead to a larger repertoire of motor strategies and integration of the prosthesis into the motor control of the child facilitating prosthesis acceptance. However, there is little or no evidence supporting this hypothesis. The neural basis underlying motor performance in children using a prosthesis has been severely understudied resulting in minimal empirical evidence. This is largely due to i) the high prosthesis rejection rate and abandonment observed in this pediatric population making it difficult to properly monitor behavioral or neural changes before and after using a prosthesis, and ii) technological constraints of traditional neuroimaging techniques, such as functional magnetic resonance imaging (fMRI) and electroencephalography (EEG), in the assessment of brain function of pediatric populations. Functional near- infrared spectroscopy (fNIRS) has emerged as a practical neuroimaging technique that is less sensitive to noise and movement artifacts than EEG and fMRI, making it easier for children to tolerate testing. The use of fNIRS in conjunction with customized and visually appealing 3D printed prostheses would provide the unique opportunity to quantitatively assess the influence of upper-limb prostheses in the neural activation patterns of the primary motor cortex and motor performance of children. Our pilot work has shown a reduction of cortical activation, a more efficient motor response, and increased coordination after prolonged use of a 3D printed upper-limb prosthesis. This study will determine the influence of using a prosthesis on the neural activation patterns of the primary motor cortex in children with unilateral congenital partial hand reductions. The central hypothesis is that prolonged prosthesis use will result in a reduced primary cortex activation indicating that wearing a prosthesis may assist the primary motor cortex to produce a more refined, specialized, and efficient motor cortex response improving motor performance and the functional use of the prosthesis.