A Lower Limb Prosthesis with Active Alignment for Reduced Limb Loading

Over the past decade, the growing field of robotics has created new possibilities in lower limb prostheses. The focus of these new prostheses has been replicating the dynamics of the lost limb in order to restore gait of individuals with lower limb amputations to healthy norms. This places demanding loads on the residual limb. Compensation by the rest of body is high, causes overloading of intact joints and can lead to deterioration of mobility and overall health. Abnormalities remain present in the person’s gait, stemming from the loading of soft tissue and the altered anatomy of the affected limb. In this dissertation, an experimental prosthesis is developed with systematic, simulation based techniques. Kinematics and kinetics of the prosthesis design are altered in order to actively realign the limb in relation to the center of pressure during stance, allowing positive power to be generated by the prosthesis while actively reducing the magnitude of the sagittal moment transferred to the residual limb. Initial findings show that during walking with the experimental device compared to a daily use prosthesis, peak pressures on the residual limb are lowered by over 10% while maintaining walking speed

How a Diverse Research Ecosystem Has Generated New Rehabilitation Technologies: Review of NIDILRR’s Rehabilitation Engineering Research Centers

Over 50 million United States citizens (1 in 6 people in the US) have a developmental, acquired, or degenerative disability. The average US citizen can expect to live 20% of his or her life with a disability. Rehabilitation technologies play a major role in improving the quality of life for people with a disability, yet widespread and highly challenging needs remain. Within the US, a major effort aimed at the creation and evaluation of rehabilitation technology has been the Rehabilitation Engineering Research Centers (RERCs) sponsored by the National Institute on Disability, Independent Living, and Rehabilitation Research. As envisioned at their conception by a panel of the National Academy of Science in 1970, these centers were intended to take a “total approach to rehabilitation”, combining medicine, engineering, and related science, to improve the quality of life of individuals with a disability. Here, we review the scope, achievements, and ongoing projects of an unbiased sample of 19 currently active or recently terminated RERCs. Specifically, for each center, we briefly explain the needs it targets, summarize key historical advances, identify emerging innovations, and consider future directions. Our assessment from this review is that the RERC program indeed involves a multidisciplinary approach, with 36 professional fields involved, although 70% of research and development staff are in engineering fields, 23% in clinical fields, and only 7% in basic science fields; significantly, 11% of the professional staff have a disability related to their research. We observe that the RERC program has substantially diversified the scope of its work since the 1970’s, addressing more types of disabilities using more technologies, and, in particular, often now focusing on information technologies. RERC work also now often views users as integrated into an interdependent society through technologies that both people with and without disabilities co-use (such as the internet, wireless communication, and architecture). In addition, RERC research has evolved to view users as able at improving outcomes through learning, exercise, and plasticity (rather than being static), which can be optimally timed. We provide examples of rehabilitation technology innovation produced by the RERCs that illustrate this increasingly diversifying scope and evolving perspective. We conclude by discussing growth opportunities and possible future directions of the RERC program

Enhancing Upper Limb Prostheses Through Neuromorphic Sensory Feedback

Upper limb prostheses are rapidly improving in terms of both control and sensory feedback, giving rise to lifelike robotic devices that aim to restore function to amputees. Recent progress in forward control has enabled prosthesis users to make complicated grip patterns with a prosthetic hand and nerve stimulation has enabled sensations of touch in the missing hand of an amputee. A brief overview of the motivation behind the work in this thesis is given in Chapter 1, which is followed by a general overview of the field and state of the art research (Chapter 2). Chapters 3 and 4 look at the use of closed loop tactile feedback for improving prosthesis grasping functionality. This entails development of two algorithms for improving object manipulation (Chapter 3) and the first real-time implementation of neuromorphic tactile signals being used as feedback to a prosthesis controller for improved grasping (Chapter 4). The second half of the thesis (Chatpers 5 - 7) details how sensory information can be conveyed back to an amputee and how the tactile sensations can be utilized for creating a more lifelike prosthesis. Noninvasive electrical nerve stimulation was shown to provide sensations in multiple regions of the phantom hand of amputees both with and without targeted sensory reinnervation surgery (Chapter 5). A multilayered electronic dermis (e-dermis) was developed to mimic the behavior of receptors in the skin to provide, for the first time, sensations of both touch and pain back to an amputee and the prosthesis (Chapter 6). Finally, the first demonstration of sensory feedback as a key component of phantom hand movement for myoelectric pattern recognition shows that enhanced perceptions of the phantom hand can lead to improved prosthesis control (Chapter 7). This work provides the first demonstration of how amputees can perceive multiple tactile sensations through a neuromorphic stimulation paradigm. Furthermore, it describes the unique role that nerve stimulation and phantom hand activation play in the sensorimotor loop of upper limb amputees

An In-Silico Assessment of Stemless Shoulder Arthroplasty: from CT to Predicted Bone Response

Despite the emergence of stemless humeral implants that utilize short fixation features to gain purchase solely in the metaphysis, the literature contains little information regardingthe morphology and mechanical properties of the humerus’ proximal trabecular-canal, and how stemless implants impact bone response. The present work employs in-silicotools, including CT-based and Finite Element (FE) methods, to define parameters that may influence stemless implant design. The density and morphology of the proximal humerus were assessed using CT-derived point clouds of the trabecular-canal. Bone density was found to diminish 15-20mm beneath the humeral head resection and was greater peripherally. The depth, path and bounding diameters of the proximal trabecular-canal were also quantified and established the spatial constraints in which implants should be designed. To address the lack of consensus regarding the FE modelling of humeral trabecular- stiffness, eight (8) FE models were constructed then duplicated six different trabecular- stiffness relationships. The deviation induced in FE outcomes by stiffness relationship selection was quantified. It was determined that inhomogeneous stiffness definition is important; however, the anatomic site from which the stiffness is defined induced minor deviations in the implant-bone contact area, the change in bone stresses and the potential bone response following stemless reconstruction. Finally, with humeral FE modelling parameters defined, a series of ten generic stemless implants were designed with fixation features that were primarily central, peripheral or boundary-crossing. A population of five (5) cadaveric humeral FE models were constructed for each implant. Tradeoffs were found, with central implants producing the least resorbing potential, and peripheral implants maintaining the most implant-bone contact. Regardless of fixation feature design, predicted bone changes were most prominent within the lateral quadrant of the humerus, directly beneath the humeral head resection. The present work advances the understanding of stemless humeral arthroplasty. The morphological parameters defined provide a spatial definition of the region in which stemless implants function. Through the development of humeral FE models, general trends in bone response following stemless reconstruction were noted; along with tradeoffs regarding the placement of stemless fixation features. These methods can be applied in the design of future stemless implants

Performance evaluation of an ensemble neural network system of estimating transtibial prosthetic socket pressures during standing, walking and condition perturbation.

Providing suitable prosthetic sockets for the restoration of function following lower-limb amputation remains a significant issue in medical device prescription. Poorly designed sockets are associated with discomfort, poor quality function and injury, with quality linked to the capability of the socket to adequately distribute the forces from ambulation. Despite this link, systems of measuring stump-socket interface pressure have not seen use in clinical practice, in part due to limitations in functional performance. A technique using neural networks to relate external socket deformation to the internal pressure distribution was recently developed: this method has several advantages over contemporary systems but had not been evaluated in detail in dynamic situations. A wireless system estimating transtibial socket pressure distribution was produced. When supplied with simulated socket loads, an estimate produced from a group of networks (an ensemble) demonstrated improved accuracy and reduced variance. Work was undertaken to identify optimal design in terms of input data conditioning and post-estimate correction. This demonstrated that these can provide significant accuracy and reliability improvements. Measurements were taken from two transtibial amputees during standing, walking, walking on slopes, walking with coronal plane misalignment and walking with an alternative socket liner. An evaluation of the contributions to variance confirmed the applicability of ensembles in this application. The system proved capable recording significant differences in socket load distribution between different prosthesis configurations. For future investigation, this demonstrates that the technique is sensitive enough to examine the changes in the application of force which are present during daily use, device set-up and common fault conditions. The results of this study support further development of the practical aspects of the system, future work in producing a realistic load training system and extrapolation of results to other sockets, structures and engineering problems