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Detection of knee unlock during stance by accelerometry
1Institute for Biomedical Technology (BMTI), Faculty of Electrical Engineering, University of Twente, Enschede, The Netherlands.
IEEE Transactions on Rehabilitation Engineering : a Publication of the IEEE Engineering in Medicine and Biology Society
|December 1, 1996
Summary
This study explored accelerometer setups for detecting knee unlocks in functional neuromuscular stimulation (FNS) for paraplegic standing. Specific differential accelerometer configurations showed promise for early and reliable knee unlock detection.
Area of Science:
- Biomedical Engineering
- Rehabilitation Technology
- Biomechanics
Background:
- Accurate knee unlock detection is vital for artificial reflex control in paraplegic standing using functional neuromuscular stimulation (FNS).
- Existing methods require comparison with novel sensor configurations for improved performance.
Purpose of the Study:
- To investigate and compare various uniaxial accelerometer configurations for detecting knee unlocks.
- To evaluate accelerometer performance against goniometer-based detection for both fast and slow knee movements.
Main Methods:
- Four single and two differential accelerometer configurations were mounted on the thigh and shank of healthy subjects.
- Sensitive axes were aligned in the sagittal plane, perpendicular to body segment long axes.
- Detection thresholds were optimized to prevent false positives from body sway; experiments included fast/slow knee flexions and body sways.
Main Results:
- A thigh-mounted differential accelerometer configuration and a single proximal knee accelerometer detected fast knee unlocks earlier than goniometers.
- A thigh-shank differential accelerometer configuration detected slow knee unlocks comparably to goniometers.
- Single accelerometers detected slow unlocks only at larger knee flexion angles, while rejecting whole-body movements.
Conclusions:
- Specific differential accelerometer configurations offer efficient and early detection of knee unlocks for FNS applications.
- Accelerometer-based knee unlock detection shows potential for enhancing control systems in paraplegic standing.