UE prosthetics

Description
Mechanomyographic (MMG) signals or "muscle sounds" originate from the summation of propagated active muscle fibre twitches during muscle contraction. MMG signals are proportional to contraction force over a range of force levels. Compared to conventional electromyographic (EMG) signal-based control, MMG presents several unique advantages. For example, MMG need not be situated directly over the muscle bulk and therefore sensor placement is relatively non-specific. As a result, soft silicon sockets can be used, offering greater comfort and distributed suspension. Furthermore, unlike EMG sensors, MMG measurement is not compromised by perspiration or other conductivity degradations at the electrode-skin interface. Lastly, some deep muscle activity is measurable by superficial MMG sensors whereas surface EMG is confined to superficial muscles. This potentially enables the use of more complex, multifunction control schemes.

Our MMG research has focused on the:

• Development of a novel coupled sensor for harnessing MMG signals and filtering contaminant contributions from motion artifact, a challenge which has precluded practical usage of MMG for over 20 years;
• Investigation of both static and dynamic pattern recognition methods of exploiting multiple signal channels for prosthesis control, and
• Development of hybrid systems that combine the merits of MMG and EMG for multifunction classification.

Novel actuation mechanisms
Current DC motors offer limited functionality and are not easily scalable to multi-articulate prosthetic hands. In response, we have explored alternative methods of actuations. In the past, we have experimented with nickel-titanium alloy in the design of a prosthetic finger prototype. Recently, we have explored the potential of active materials, particularly, the feasibility of dielectric elastomers. As developments in conventional and novel actuators materialize, we will continue to investigate possible technologies to realize the user's desire for lighter-weight prostheses, more life-like in both form and function.

International survey
The current state of knowledge in upper extremity prosthetic utilization is laden with contradictory evidence and unanswered questions stemming from a number of study shortfalls, including, but not limited to small and geographically constrained samples, a lack of standardized measurement tools and incomplete documentation. The overall goal of the international online survey is to further elucidate the motivations for prosthesis abandonment by adopting a holistic approach that addresses personal, contextual and technological factors. The results of this study will be pertinent to health professionals, researchers, and administrators involved in the care of individuals with upper limb deficiency, the design of improved prosthetics, and the assessment and optimization of clinical strategies. Based on the survey data, we may also formulate predictive models of client behaviors and ultimately better tailor clinical practice to meet user needs.