Assessment of the Shank-to-Vertical Angle While Changing Heel Heights Using a Single Inertial Measurement Unit in Individuals with Incomplete Spinal Cord Injury Wearing an Ankle-Foot-Orthosis

Sensors, 2021 · DOI: https://doi.org/10.3390/s21030985 · Published: February 2, 2021

Assistive Technology Rehabilitation Biomechanics

Simple Explanation

This study focuses on using a sensor, specifically an Inertial Measurement Unit (IMU), to measure the angle between the shin and the vertical (Shank-to-Vertical Angle or SVA) in people with incomplete spinal cord injury (iSCI) who wear an ankle-foot orthosis (AFO). The goal was to see if the IMU could accurately measure the SVA and detect changes when the heel height of the AFO-footwear combination is adjusted. This is important because proper alignment of the AFO can improve walking ability. The study also looked at how changes in heel height affect the knee joint angle and moment, providing additional insights into the impact of AFO adjustments on lower limb biomechanics.

Study Duration

Between June and December 2019

Participants

12 persons with an iSCI

Evidence Level

Not specified

Key Findings

1
The study found that the SVA measured by the IMU is valid, meaning it accurately reflects the SVA when compared to the gold standard 3D gait analysis.
2
The IMU was also responsive to changes in heel height, indicating that it can detect differences in SVA when the heel height of the AFO is adjusted.
3
Changes in heel height also led to concomitant changes in the knee joint moment, suggesting that adjusting the heel height of an AFO can affect knee biomechanics.

Research Summary

This study investigated the validity and responsiveness of using a single IMU to measure the Shank-to-Vertical Angle (SVA) in individuals with incomplete spinal cord injury (iSCI) wearing an ankle-foot orthosis (AFO) while changing heel heights. The results showed good validity and responsiveness of the IMU-measured SVA compared to 3D gait analysis, with significant differences observed between reference and high heel height conditions. The study also found that changes in heel height led to concomitant changes in knee joint moment, suggesting that the IMU can effectively reflect changes in AFO alignment and their impact on lower limb biomechanics.

Practical Implications

AFO Tuning Guidance

IMUs can be used as a valid and responsive tool to guide AFO tuning by measuring the SVA, offering a low-cost alternative to expensive gait labs.

Clinical Practice

The findings support the use of IMUs in clinical practice to assess and adjust AFOs for individuals with iSCI, potentially improving walking ability.

Knee Biomechanics Impact

Adjusting heel height in AFOs can affect knee biomechanics, as evidenced by changes in knee joint moment, which should be considered during AFO tuning.

Study Limitations

1
The study had a relatively small sample size (n=12).
2
The inability to measure subtle changes, especially between the low and high heel height condition, could be explained by the great variability in response on increasing heel heights.
3
Participants may have counteracted the increase to prevent larger knee angles and moments in order to retain stability during stance and an efficient walking pattern.

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