Validity and Reliability of Inertial Measurement Unit (IMU)-Derived 3D Joint Kinematics in Persons Wearing Transtibial Prosthesis.

BACKGROUND: A validity and reliability assessment of inertial measurement unit (IMU)-derived joint angular kinematics during walking is a necessary step for motion analysis in the lower extremity prosthesis user population. This study aimed to assess the accuracy and reliability of an inertial measurement unit (IMU) system compared to an optical motion capture (OMC) system in transtibial prosthesis (TTP) users. METHODS: Thirty TTP users were recruited and underwent simultaneous motion capture from IMU and OMC systems during walking. Reliability and validity were assessed using intra- and inter-subject variability with standard deviation (S.D.), average S.D., and intraclass correlation coefficient (ICC). RESULTS: The intra-subject S.D. for all rotations of the lower limb joints were less than 1° for both systems. The IMU system had a lower mean S.D. (o), as seen in inter-subject variability. The ICC revealed good to excellent agreement between the two systems for all sagittal kinematic parameters. CONCLUSION: All joint angular kinematic comparisons supported the IMU system's results as comparable to OMC. The IMU was capable of precise sagittal plane motion data and demonstrated validity and reliability to OMC. These findings evidence that when compared to OMC, an IMU system may serve well in evaluating the gait of lower limb prosthesis users.

A Comparison of the Conventional PiG Marker Method Versus a Cluster-Based Model when recording Gait Kinematics in Trans-Tibial Prosthesis Users and the Implications for Future IMU Gait Analysis.

Validation testing is a necessary step for inertial measurement unit (IMU) motion analysis for research and clinical use. Optical tracking systems utilize marker models which must be precise in measurement and mitigate skin artifacts. Prosthesis wearers present challenges to optical tracking marker model choice. Seven participants were recruited and underwent simultaneous motion capture from two marker sets; Plug in Gait (PiG) and the Strathclyde Cluster Model (SCM). Variability of joint kinematics within and between subjects was evaluated. Variability was higher for PiG than SCM for all parameters. The within-subjects variability as reported by the average standard deviation (SD), was below 5.6° for all rotations of the hip on the prosthesis side for all participants for both methods, with an average of 2.1° for PiG and 2.5° for SCM. Statistically significant differences in joint parameters caused by a change in the protocol were evident in the sagittal plane (p < 0.05) on the amputated side. Trans-tibial gait analysis was best achieved by use of the SCM. The SCM protocol appeared to provide kinematic measurements with a smaller variability than that of the PiG. Validation studies for prosthesis wearer populations must reconsider the marker protocol for gold standard comparisons with IMUs.

Sustainable, affordable and functional: reimagining prosthetic liners in resource limited environments.

PURPOSE: The purpose of this study was to evaluate function and performance of unilateral trans-tibial prosthesis users wearing an affordable liner in three types of socket designs. METHODS: Five unilateral trans-tibial amputees participated, were provided an Affordable Ethyl-Vinyl-Acetate Roll-On liner (AERO) roll-on liner with patella tendon bearing (PTB) prosthesis, PE-Lite liner with PTB prosthesis, and an (AERO) liner with total-surface bearing (TSB) prosthesis. A battery of outcome measures; step-counts, socket comfort score (SCS), orthotics prosthetics user survey (OPUS) and socket pressure measurement during walking were administered. RESULTS: Comparisons of step-counts indicated that PTB-AERO (3604 ± 815) was not significantly different than PTB-PE-Lite (3386 ± 942). Mean SCS was 9.2 ± .83 and 7.2 ± 2.1 for PTB-AERO and PTB-PE-Lite. A 6.6% decrease in mean peak pressure was observed between PTB-PE-Lite and TSB-AERO, and 3.2% difference between PTB-PE-Lite and PTB-AERO. CONCLUSION: An affordable ($20 USD) and sustainably fabricated prosthesis liner was created and evaluated in trans-tibial prosthesis users. These initial results garner preliminary support for use of the AERO prosthetic liner and continued research.Implications for rehabilitationLower limb prosthetics in less-resourced settings can leverage locally sourced and affordable materials to fabricate roll-on liners for use in modern prosthetic sockets.The cost of the AERO liner is markedly lower than current standard of care gel liners, yet still facilitates use of current prosthetic sockets.

The development and testing of a modified natural rubber CR solid ankle-cushion heel prosthetic foot for developing countries.

BACKGROUND: Durable and locally fabricated prosthetic feet are important for developing countries. Modifications to the current CR solid ankle-cushion heel prosthetic foot could enhance current foot characteristics and reduce costs. The goal of this project was to modify the keel and rubber outer foot shell to enhance features and reduce costs of the current CR solid ankle-cushion heel offering. METHODS: The prosthetic foot was designed, fabricated and then tested mechanically for strain and displacement in a cyclic testing machine according to a component of the ISO-10328 testing protocol. Dynamic cyclic testing of both forefoot and heel portions of the foot was conducted. FINDINGS: Dynamic mechanical cyclic testing of the forefoot and heel at 1.28 kN for two million cycles at a rate of 1 Hz was successfully achieved. The final cost of producing the foot was roughly $16 USD. Limitations include the inability to perform the full battery of ISO-10328 foot testing, UV testing and a limitation to laboratory testing. Clinical studies examining practical application of the modified foot should be conducted.