Showing papers by "David Howard published in 2016"

The effects of prosthetic ankle stiffness on stability of gait in people with transtibial amputation.

Abstract: The ability to control balance during walking is a critical precondition for minimizing fall risk, but this ability is compromised in persons with lower-limb absence because of reduced sensory feedback mechanisms and inability to actively modulate prosthesis mechanical function. Consequently, these individuals are at increased fall risk compared with nondisabled individuals. A number of gait parameters, including symmetry and temporal variability in step/stride characteristics, have been used as estimates of gait stability and fall risk. This study investigated the effect of prosthetic ankle rotational stiffness on gait parameters related to walking stability of transtibial prosthesis users. Five men walked with an experimental prosthesis that allowed for independent modulation of plantar flexion and dorsiflexion stiffness. Two levels of plantar flexion and dorsiflexion stiffness were tested during level, uphill, and downhill walking. The results demonstrate that low plantar flexion stiffness reduced time to foot-flat, and this was associated with increased perceived stability, while low dorsiflexion stiffness demonstrated trends in temporal-spatial parameters that are associated with improved gait stability (reduced variability and asymmetry). Prosthesis design and prescription for low rotational stiffness may enhance gait safety for transtibial prosthesis users at risk of unsteadiness and falls.

Transtibial amputee gait efficiency : energy storage and return versus solid ankle cushioned heel prosthetic feet

Abstract: Energy storage and return (ESR) feet have long been assumed to promote metabolically efficient amputee gait. However, despite being prescribed for approximately 30 yr, there is limited evidence that they achieve this desired function. Here, we report a meta-analysis of data from 10 studies that met our selection criteria to determine whether amputee walking with ESR feet is more efficient than with conventional solid ankle cushioned heel (SACH) feet. Additionally, the data were tested for a relationship with walking speed since it has been suggested ESR feet might perform better at higher speeds. The raw data are highly variable because of differences in study protocols; therefore, we normalized the data and found a statistically significant difference (p < 0.001) between ESR and SACH feet. However, the magnitude of this difference is small, with the cost of transport (COT) with ESR feet being 97.3% of the cost with SACH feet. No relationship between ESR COT and speed was found (p = 0.19). We hypothesize that the small but statistically significant difference between ESR and SACH feet may not constitute a functionally significant improvement in COT, possibly related to the limited push-off power provided by ESR feed compared with nondisabled ankles.

The use of an adjustable electrode housing unit to compare electrode alignment and contact variation with myoelectric prosthesis functionality: A pilot study.

Abstract: Background: Usable myoelectric control relies on secure and intimate contact at all times between the electrode, the socket and the residual limb. At present, there is little post-fitting socket adjustment available to prosthetists with respect to electrode contact security or alignment. Failure to provide secure electrode contact could result in the development of motion artefacts, poor prehensor response and subsequent prosthesis non-usage. Objectives: To establish the effect of alteration to electrode contract security and alignment on prosthesis functionality using a bespoke electrode housing unit. Study design: This study investigated the effect of electrode contact security and alignment on upper limb myoelectric prosthesis functionality. Methods: Four different electrode housing arrangements were assessed within prosthetic sockets fitted to six transradial prosthesis subjects using the Southampton Hand Assessment Procedure, which is a reliable and validated prosthesis functionality assessment tool. Results: Significantly higher functionality scores were achieved with the bespoke housing unit compared to when using conventional electrode housings. Conclusion: Myoelectric prosthesis functionality is closely linked to electrode contact security and to electrode alignment with respect to the residual limb. Both these factors can be improved locally using an adjustable electrode housing unit.

Crowd-Sourced Amputee Gait Data: A Feasibility Study Using YouTube Videos of Unilateral Trans-Femoral Gait.

Abstract: Collecting large datasets of amputee gait data is notoriously difficult. Additionally, collecting data on less prevalent amputations or on gait activities other than level walking and running on hard surfaces is rarely attempted. However, with the wealth of user-generated content on the Internet, the scope for collecting amputee gait data from alternative sources other than traditional gait labs is intriguing. Here we investigate the potential of YouTube videos to provide gait data on amputee walking. We use an example dataset of trans-femoral amputees level walking at self-selected speeds to collect temporal gait parameters and calculate gait asymmetry. We compare our YouTube data with typical literature values, and show that our methodology produces results that are highly comparable to data collected in a traditional manner. The similarity between the results of our novel methodology and literature values lends confidence to our technique. Nevertheless, clear challenges with the collection and interpretation of crowd-sourced gait data remain, including long term access to datasets, and a lack of validity and reliability studies in this area.

A fast inverse dynamics model of walking for use in optimisation studies

Abstract: Computer simulation of human gait, based on measured motion data, is a well-established technique in biomechanics. However, optimisation studies requiring many iterative gait cycle simulations have not yet found widespread application because of their high computational cost. Therefore, a computationally efficient inverse dynamics model of 3D human gait has been designed and compared with an equivalent model, created using a commercial multi-body dynamics package. The fast inverse dynamics model described in this paper led to an eight fold increase in execution speed. Sufficient detail is provided to allow readers to implement the model themselves.

A flexible finite state controller for upper limb functional electrical stimulation

Abstract: This paper reports on a flexible finite stage machine (FSM) controller for the real-time control of functional electrical stimulation (FES) during upper limb rehabilitation, and an associated setup Graphical User Interface (GUI) guides clinical users through the process of setting up new FSM controllers for practicing user-defined functional tasks across a range of patients. The FSM control has been demonstrated using the “drink from a cup” example task. The test results illustrate the functionality of the controller and also demonstrate the success of implementation.

A flexible control system of functional electrical stimulation (FES) for upper limb rehabilitation

Abstract: Background. Highly intensive FES-supported practice of functional tasks, under voluntary control, is showing promise to promote recovery of upper limb function following stroke [2, 3]. However, the ability to deliver this type of therapy in clinical settings is limited by available tools [1, 4]. Development of flexible systems, which support the user in the creation of task and patient-specific FES controllers has received relatively limited attention [8]. In this study, a flexible FES controller and associated graphical user interface is described, which allow therapists to set up FES controllers specific to both task and patient-specific impairment patterns. The graphical user interface (GUI) has been designed to be used by therapists with little or no programming skills.