Preliminary Evaluation of a Powered Lower Limb Orthosis to Aid Walking in Paraplegic Individuals

IEEE Trans Neural Syst Rehabil Eng., 2011 · DOI: 10.1109/TNSRE.2011.2163083 · Published: December 1, 2011

Spinal Cord Injury Assistive Technology Biomedical

Simple Explanation

This paper describes a powered lower-limb orthosis that is intended to provide gait assistance to spinal cord injured (SCI) individuals by providing assistive torques at both hip and knee joints. The orthosis has a mass of 12 kg and is capable of providing maximum joint torques of 40 Nm with hip and knee joint ranges of motion from 105° flexion to 30° extension and 105° flexion to 10° hyperextension, respectively. A custom distributed embedded system controls the orthosis with power being provided by a lithium polymer battery which provides power for one hour of continuous walking.

Study Duration

Not specified

Participants

One 35-year-old male with T10 complete injury

Evidence Level

Not specified

Key Findings

1
Data collected during walking indicates a high degree of step-to-step repeatability of hip and knee trajectories (as enforced by the orthosis) and an average walking speed of 0.8 km/hr.
2
The electrical power required at each hip and knee joint during gait was approximately 25 and 27 W, respectively, contributing to the 117 W overall electrical power required by the device during walking.
3
The average sound level, as measured one meter away from the orthosis, was approximately 55±2 dBA (with an ambient noise level of 38 dBA).

Research Summary

This paper describes a powered lower limb orthosis developed to assist gait in spinal cord injured individuals. Experimental results from walking trials with a T10 complete paraplegic indicate that the orthosis is capable of providing a repeatable gait with knee and hip joint amplitudes that are similar to those observed during non-SCI walking. Electrical power measurements with the current battery pack and control algorithms indicate a battery life of approximately an hour and a corresponding walking range of approximately 0.8 km.

Practical Implications

Restoration of Mobility

The orthosis can potentially restore some degree of legged mobility to individuals with paraplegia, addressing a significant impairment and improving their quality of life.

Physiological Benefits

The ability to stand and walk with assistance can mitigate the severe physiological effects of paraplegia, such as muscular atrophy, bone mineral loss, and impaired circulation.

Compact Design

The low mass and minimal body coverage of the orthosis, along with its ease of separation into modular components, enhance user acceptance and portability.

Study Limitations

1
One tradeoff associated with the design of the orthosis is the need for custom fitting relative to users of different sizes.
2
Of particular importance is that the sagittal plane centers of rotation of the orthosis joints be concentric with the approximate corresponding centers of rotation of the user’s physiological hip and knee joints, and the width of the hip piece correspond to the width of the user’s hips.
3
In the absence of shoulder straps or structure under the shoes, the orthosis must fit the wearer well in order to effectively support the weight of the orthosis and provide the desired functionality.

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