The physiological cost index of walking with a powered knee-ankle-foot orthosis in subjects with poliomyelitis: A pilot study

Background: A powered knee-ankle-foot orthosis was developed to provide restriction of knee flexion during stance phase and active flexion and extension of the knee during swing phase of gait. Objective: The purpose of this study was to determine its effect on the physiological cost index, walking speed and the distance walked in people with poliomyelitis compared to when walking with a knee-ankle-foot orthosis with drop lock knee joints. Study design: Quasi experimental study. Methods: Seven subjects with poliomyelitis volunteered for the study and undertook gait analysis with both types of knee-ankle-foot orthosis. Results: Walking with the powered knee-ankle-foot orthosis significantly reduced walking speed (p=0.015) and the distance walked (p=0.004), and also, it did not improve physiological cost index values (p=0.009) compared to walking with the locked knee-ankle-foot orthosis. Conclusion: Using a powered knee-ankle-foot orthosis did not significantly improve any of the primary outcome measures during walking for poliomyelitis subjects. Clinical relevance This powered knee-ankle-foot orthosis design did not improve the physiological cost index of walking for people with poliomyelitis when compared to walking with a knee-ankle-foot orthosis with drop lock knee joints. This may have been due to the short training period used or the bulky design and additional weight of the powered orthosis. Further research is therefore warranted.