Reduction of genu recurvatum through adjustment of plantarflexion resistance of an articulated ankle-foot orthosis in individuals post-stroke

Abstract

Background: Genu recurvatum (knee hyperextension) is a common issue for individuals post-stroke. Ankle-foot orthoses are used to improve genu recurvatum, but evidence is limited concerning their effectiveness. Therefore, the aim of this study was to investigate the effect of changing the plantarflexion resistance of an articulated ankle-foot orthosis on genu recurvatum in patients post-stroke.

Methods: Gait analysis was performed on 6 individuals post-stroke with genu recurvatum using an articulated ankle-foot orthosis whose plantarflexion resistance was adjustable at four levels. Gait data were collected using a Bertec split-belt instrumented treadmill in a 3-dimensional motion analysis laboratory. Gait parameters were extracted and plotted for each subject under the four plantarflexion resistance conditions of the ankle-foot orthosis. Gait parameters included: a) peak ankle plantarflexion angle, b) peak ankle dorsiflexion moment, c) peak knee extension angle and d) peak knee flexion moment. A non-parametric Friedman test was performed followed by a post-hoc Wilcoxon Signed-Rank test for statistical analyses.

Findings: All the gait parameters demonstrated statistically significant differences among the four resistance conditions of the AFO. Increasing the amount of plantarflexion resistance of the ankle-foot orthosis generally reduced genu recurvatum in all subjects. However, individual analyses showed that the responses to the changes in the plantarflexion resistance of the AFO were not necessarily linear, and appear unique to each subject.

Interpretations: The plantarflexion resistance of an articulated AFO should be adjusted to improve genu recurvatum in patients post-stroke. Future studies should investigate what clinical factors would influence the individual differences.

Keywords: AFO; Gait; Hemiplegia; Hyperextension; Orthotics; Stiffness.

Conflict of interest statement

Conflict of interest statement

Kobayashi T, Orendurff MS and Daly WK are/were employees of Orthocare Innovations and designed the articulated AFO used in this study.

Copyright © 2016 Elsevier Ltd. All rights reserved.

Figures

Figure 1

(A) The articulated ankle-foot orthosis (AFO) used in this study, (B) Plantarflexion resistance characteristics of the AFO under 4 spring conditions (S1, S2, S3 and S4) (Kobayashi et al., 2015).

Figure 2

The effect of plantarflexion resistance of the articulated ankle-foot orthosis under spring condition S1 and S4 on the (A) mean ankle joint angles, (B) mean ankle joint moments, (C) mean knee angles and (D) mean knee moment. Normal gait data were adopted from Winter. 1991. The results from spring conditions S2 and S3 fell within the range of S1and S4; therefore, only the results from S1 and S4 are presented in the graphs for clarity. Actual data of ankle and knee angle and moment parameters under each spring condition can be found in Table 3. Dorsiflexion angles and plantarflexion moments were defined as positive for the ankle joint, while knee flexion angles and knee extension moments were defined as positive for the knee joint.

Figure 2

The effect of plantarflexion resistance of the articulated ankle-foot orthosis under spring condition S1 and S4 on the (A) mean ankle joint angles, (B) mean ankle joint moments, (C) mean knee angles and (D) mean knee moment. Normal gait data were adopted from Winter. 1991. The results from spring conditions S2 and S3 fell within the range of S1and S4; therefore, only the results from S1 and S4 are presented in the graphs for clarity. Actual data of ankle and knee angle and moment parameters under each spring condition can be found in Table 3. Dorsiflexion angles and plantarflexion moments were defined as positive for the ankle joint, while knee flexion angles and knee extension moments were defined as positive for the knee joint.

Figure 2

The effect of plantarflexion resistance of the articulated ankle-foot orthosis under spring condition S1 and S4 on the (A) mean ankle joint angles, (B) mean ankle joint moments, (C) mean knee angles and (D) mean knee moment. Normal gait data were adopted from Winter. 1991. The results from spring conditions S2 and S3 fell within the range of S1and S4; therefore, only the results from S1 and S4 are presented in the graphs for clarity. Actual data of ankle and knee angle and moment parameters under each spring condition can be found in Table 3. Dorsiflexion angles and plantarflexion moments were defined as positive for the ankle joint, while knee flexion angles and knee extension moments were defined as positive for the knee joint.

Figure 2

The effect of plantarflexion resistance of the articulated ankle-foot orthosis under spring condition S1 and S4 on the (A) mean ankle joint angles, (B) mean ankle joint moments, (C) mean knee angles and (D) mean knee moment. Normal gait data were adopted from Winter. 1991. The results from spring conditions S2 and S3 fell within the range of S1and S4; therefore, only the results from S1 and S4 are presented in the graphs for clarity. Actual data of ankle and knee angle and moment parameters under each spring condition can be found in Table 3. Dorsiflexion angles and plantarflexion moments were defined as positive for the ankle joint, while knee flexion angles and knee extension moments were defined as positive for the knee joint.

Figure 3

Individual responses to the changes of the plantarflexion resistance of the AFO from spring condition S1 to S4 in (A) peak plantarflexion angle, (B) peak dorsiflexion moment, (C) peak knee extension angle, and (D) peak knee flexion moment. Dorsiflexion angles and plantarflexion moments were defined as positive for the ankle joint, while knee flexion angles and knee extension moments were defined as positive for the knee joint.

Figure 3

Individual responses to the changes of the plantarflexion resistance of the AFO from spring condition S1 to S4 in (A) peak plantarflexion angle, (B) peak dorsiflexion moment, (C) peak knee extension angle, and (D) peak knee flexion moment. Dorsiflexion angles and plantarflexion moments were defined as positive for the ankle joint, while knee flexion angles and knee extension moments were defined as positive for the knee joint.

Figure 3

Individual responses to the changes of the plantarflexion resistance of the AFO from spring condition S1 to S4 in (A) peak plantarflexion angle, (B) peak dorsiflexion moment, (C) peak knee extension angle, and (D) peak knee flexion moment. Dorsiflexion angles and plantarflexion moments were defined as positive for the ankle joint, while knee flexion angles and knee extension moments were defined as positive for the knee joint.

Figure 3

Individual responses to the changes of the plantarflexion resistance of the AFO from spring condition S1 to S4 in (A) peak plantarflexion angle, (B) peak dorsiflexion moment, (C) peak knee extension angle, and (D) peak knee flexion moment. Dorsiflexion angles and plantarflexion moments were defined as positive for the ankle joint, while knee flexion angles and knee extension moments were defined as positive for the knee joint.