A Sensor Array for the Measurement of Relative Motion in Lower Limb Prosthetic Sockets

3D Motion Analysis for the Assessment of Dynamic Coupling in Transtibial Prosthetics: A Proof of Concept

Assessment of coupling between transtibial sockets and users is historically based on clinicians' observations and experience, but can be inaccurate and unreliable. Therefore, we present a proof of concept, for five out of six possible degrees of freedom coupling metric system for a socket, using motion analysis calibrated on a 3D printed limb substitute. The method is compatible with any socket suspension method and does not require prior modifications to the socket. Calibration trials were used to locate the axis of rotation of the knee joint referenced against a marker cluster on the thigh; this allowed for the identification of the limb during test trials despite the entire residuum being obscured from view by the socket. The error in the technique was found to be within 0.7 mm in displacement and 0.7 degrees in rotation, based on the control data. Dynamic testing showed the Inter Quartile Range (IQR) of inter time step variance was <0.5 mm/deg for all metrics. The method can form a basis for objective socket evaluation, improve clinical practice and the quality of life for amputees.

A case study on the value of in-socket force measurements in gait monitoring of lower-limb prosthesis users

Wearable sensors have the potential to drastically improve gait rehabilitation and assessments. This is especially the case for lower limb prosthesis users as small wearables can provide useful information about in-socket conditions. Through a simple case study, we investigated the value of measuring in-socket forces in addition to gait parameters in gauging the effectiveness of a training intervention. The results showed that the additional objective information obtained through in-socket measurements can enhance our understanding of how a particular intervention affects both gait and socket comfort.

Development of a Wearable Human-Machine Interface to Track Forearm Rotation via an Optical Sensor

The goal of this research was to develop an intuitive wearable human-machine interface (HMI), utilizing an optical sensor. The proposed system quantifies wrist pronation and supination using an optical displacement sensor. Compared with existing systems, this HMI ensures intuitiveness by relying on direct measurement of forearm position, minimizes involved sensors, and is expected to be long-lasting. To test for feasibility, the developed HMI was implemented to control a prosthetic wrist based on forearm rotation of able-bodied subjects. Performance of optical sensor system (OSS) prosthesis control was compared to electromyography (EMG) based direct control, for six able-bodied individuals, using a clothespin relocation task. Results showed that the performance of OSS control was comparable to direct control, therefore validating the feasibility of the OSS HMI.

Lower limb prosthetic interfaces: Clinical and technological advancement and potential future direction

The human-prosthesis interface is one of the most complicated challenges facing the field of prosthetics, despite substantive investments in research and development by researchers and clinicians around the world. The journal of the International Society for Prosthetics and Orthotics, Prosthetics and Orthotics International, has contributed substantively to the growing body of knowledge on this topic. In celebrating the 50th anniversary of the International Society for Prosthetics and Orthotics, this narrative review aims to explore how human-prosthesis interfaces have changed over the last five decades; how research has contributed to an understanding of interface mechanics; how clinical practice has been informed as a result; and what might be potential future directions. Studies reporting on comparison, design, manufacturing and evaluation of lower limb prosthetic sockets, and osseointegration were considered. This review demonstrates that, over the last 50 years, clinical research has improved our understanding of socket designs and their effects; however, high-quality research is still needed. In particular, there have been advances in the development of volume and thermal control mechanisms with a few designs having the potential for clinical application. Similarly, advances in sensing technology, soft tissue quantification techniques, computing technology, and additive manufacturing are moving towards enabling automated, data-driven manufacturing of sockets. In people who are unable to use a prosthetic socket, osseointegration provides a functional solution not available 50 years ago. Furthermore, osseointegration has the potential to facilitate neuromuscular integration. Despite these advances, further improvement in mechanical features of implants, and infection control and prevention are needed.