Lpj Kenney

Healthy Aims: Developing New Medical Implants and Diagnostic Equipment

Healthy Aims is a 23- million, four-year project, funded under the EUs information society technology sixth framework program to develop intelligent medical implants and diagnostic systems (www.healthyaims.org). The project has 25 partners from 10 countries, including commercial, clinical, and research groups. This consortium represents a combination of disciplines to design and fabricate new medical devices and components as well as to test them in laboratories and subsequent clinical trials. The project focuses on medical implants for nerve stimulation and diagnostic equipment based on strain-gauge technology.

A dual-task approach to the evaluation of the myokinemetric signal as an alternative to EMG

EMG is the signal widely used in neuromuscular control, biofeedback and measurement applications. Alternative physiological signals are available, but are used relatively infrequently. In the development of assistive devices, such as functional electrical stimulators, it is important to make the device as straightforward to use as possible. This is particularly relevant for patients with neurological and often associated cognitive impairments. Different physiological signals may require different degrees of attention to control, and advantage could be gained from selection of a signal that requires the least attention to control. However, relatively little work has been carried out on how to assess the demands of different physiological signals. This paper reports on the development of a novel experimental set up designed to address this problem and, in particular, to compare two different physiological signals, the EMG and the so-called MK signal. The paper presents the hardware design, including mechanical, electronic and software design, which involves data acquisition, parallel tasks and user-friendly interface. The system described could be adapted for evaluation of other physiological signals.

A generalisable methodology for stability assessment of walking aid users

To assist balance and mobility, older adults are often prescribed walking aids. Nevertheless, surprisingly their use has been associated with increased falls-risk. To address this finding we first need to characterise a persons stability while using a walking aid. Therefore, we present a generalisable method for the assessment of stability of walking frame (WF) users. Our method, for the first time, considers user and device as a combined system. We define the combined centre of pressure (CoPsystem) of user and WF to be the point through which the resultant ground reaction force for all feet of both the WF and user acts if theresultant moment acts only around an axisperpendicular tothe ground plane. We also define the combined base of support (BoSsystem) to be the convex polygon formed by the boundaries of the anatomical and WF feet in contact with the ground and interconnecting lines between them. To measure these parameters we have developed an instrumented WF with a load cell in each foot which we use together with pressure-sensing insoles and a camera system, the latter providing the relative position of the WF and anatomical feet. Software uses the resulting data to calculate the stability margin of the combined system, defined as the distance between CoPsystem and the nearest edge of BoSsystem. Our software also calculates the weight supported through the frame and when each foot (of user and/or frame) is on the floor. Finally, we present experimental work demonstrating the value of our approach.

Software tools for accelerometer-based systems

This paper describes work within the Healthy Aims project in which information from accelerometers is used to infer intent or identify activity. In particular, it reports on the development of software tools for an accelerometer-based system to assist grasp function and briefly discusses the development of activity monitoring software.

Does transverse plane mechanical compliance affect amputee gait and in-socket forces?

Transverse plane rotation in an amputees residual-limb appears to be less than in non-amputees [1,2]. However, it remains unclear firstly, to what extent this is driven by the properties of the prosthesis, and secondly, whether this has detrimental effects on the residual-limb. In trans-tibial prostheses, the socket and foot are commonly connected via a rigid adapter, which restricts the residual-limbs transverse rotation while inside the socket and can increase the forces exerted onto the residual-limb. This can subsequently trigger tissue damage. Instead of a rigid connection, an adapter with a compliant element can be fitted to prostheses to allow some transverse rotation. This novel study quantified in-socket forces and amputated side kinetics and kinematics to investigate the mechanisms by which the adapter reduces in-socket forces. Gait tests were conducted with ten unilateral trans-tibial amputees who walked on a prosthesis that had an adapter with (A) and without (B) a compliant element. Comparing (A) with (B) showed that, at early stance, whilst the socket rotated internally due to adapter compliance, the pelvis was therefore likely to internally rotate and move forward more relative to the prosthesis. This forward motion is associated with greater elevation of the centre of mass, which can be compensated for by increasing and delaying the peak in knee flexion during stance. Peak knee flexion magnitude was not significantly increased with the adapter (approximately 0.6 °, p = 0.976). However, peak knee flexion was significantly delayed with the adapter (approximately 3.28% of stance, p=0.010). Knee flexion is a common shock absorption mechanism, which significantly reduced the peak vertical ground reaction force (approximately 0.2N/kg, p=0.050) and delayed it, although not significantly (approximately 1.41% of stance, p=0.141), thus overall reducing the vertical loading rate. Reduced in-socket forces supported these findings. In conclusion, adapter compliance has therefore beneficial effects on residual-limb forces.