Yamamoto M1, Shimatani K2, Hasegawa M2, Kurita Y1
1Hiroshima University, Graduate School of Engineering, Higashi-Hiroshima City, Japan, 2Prefectural University of Hiroshima, Faculty of Health and Welfare, Mihara City, Japan
Background: An ankle-foot orthosis (AFO) is recommended for rehabilitation of post-stroke gait. In particular, an AFO with plantarflexion resistive function (PFR) is effective for improving drop foot and first rocker function. However, excessive PFR restricts joint movement during gait and may cause excessive knee loading.
Purpose: This study aimed to determine whether excessive PFR affects knee loading, and investigated the relationship of knee loading with kinematics and muscle force during gait according to magnitude of PFR.
Methods: This study included 10 healthy adult males (21.0 ± 1.1 years) and 1 adult male with a history of stroke (77 years, left side hemiplegia). PFR of the AFO used in this study was adjustable. Participants walked at self-selected comfortable speed under 3 conditions: no-AFO, AFO with weak PFR (w-PFR), and AFO with strong PFR (s-PFR). Knee joint reaction force (JRF, 1st peak vertical knee JRF and anterior peak knee JRF) and peak muscle force (quadriceps, hamstrings, and gastrocnemius) were estimated in the post-stroke participant in the early stance phase (0% to 50%) using musculoskeletal and AFO models.
We investigated the relationship of knee joint loading with kinematics and muscle force during gait according to magnitude of PFR in healthy adult males. Multiple linear regression analysis was used to predict knee JRF based on muscle force and kinematics (joint angle, angle velocity, and center of mass [COM] position displacement and velocity). Statistical significance was set at p 0.05.
Results: The results under no-AFO/w-PFR/s-PFR conditions are shown for the post-stroke patient. Knee JRF tended to change according to magnitude of PFR. Vertical knee JRF vales were 4.8/4.4/5.0 times body weight (×BW). Anterior peak knee JRF values were 1.5/1.5/1.4 ×BW. Peak quadriceps muscle force in early stance phase was 20.2/21.5/20.1 N/kg. Peak hamstring forces in early stance phase were 11.7/9.5/10.9 N/kg. Peak gastrocnemius muscle forces in early stance phase were 13.8/8.8/15.0 N/kg.
A significant regression equation for vertical and anterior knee JRF was defined, with an R2 of 0.74 and 0.49, respectively (F=29.0 and 14.837, both p 0.05). Healthy participants showed predicted 1st vertical peak knee JRF of -0.54 + 0.10 (quadriceps muscle force) + 0.20 (hamstring muscle force) + 3.03 (vertical COM velocity). In healthy participants, the predicted anterior peak knee JRF was 0.71 + 0.04 (quadriceps muscle force) - 0.01 (knee extension angle velocity).
Conclusion(s): The results suggest the need to carefully adjust PFR for each patient when using an AFO. Moreover, excessive assist of AFO may cause knee pain and deformity. Knee joint loading may be able to evaluate with a little information.
Implications: Our study findings can make a significant contribution when used as selection criteria for AFO function and for use in development of new orthoses.
Keywords: Ankle-foot orthosis, joint loading, musculoskeletal model
Funding acknowledgements: This research was based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization(NEDO).
Purpose: This study aimed to determine whether excessive PFR affects knee loading, and investigated the relationship of knee loading with kinematics and muscle force during gait according to magnitude of PFR.
Methods: This study included 10 healthy adult males (21.0 ± 1.1 years) and 1 adult male with a history of stroke (77 years, left side hemiplegia). PFR of the AFO used in this study was adjustable. Participants walked at self-selected comfortable speed under 3 conditions: no-AFO, AFO with weak PFR (w-PFR), and AFO with strong PFR (s-PFR). Knee joint reaction force (JRF, 1st peak vertical knee JRF and anterior peak knee JRF) and peak muscle force (quadriceps, hamstrings, and gastrocnemius) were estimated in the post-stroke participant in the early stance phase (0% to 50%) using musculoskeletal and AFO models.
We investigated the relationship of knee joint loading with kinematics and muscle force during gait according to magnitude of PFR in healthy adult males. Multiple linear regression analysis was used to predict knee JRF based on muscle force and kinematics (joint angle, angle velocity, and center of mass [COM] position displacement and velocity). Statistical significance was set at p 0.05.
Results: The results under no-AFO/w-PFR/s-PFR conditions are shown for the post-stroke patient. Knee JRF tended to change according to magnitude of PFR. Vertical knee JRF vales were 4.8/4.4/5.0 times body weight (×BW). Anterior peak knee JRF values were 1.5/1.5/1.4 ×BW. Peak quadriceps muscle force in early stance phase was 20.2/21.5/20.1 N/kg. Peak hamstring forces in early stance phase were 11.7/9.5/10.9 N/kg. Peak gastrocnemius muscle forces in early stance phase were 13.8/8.8/15.0 N/kg.
A significant regression equation for vertical and anterior knee JRF was defined, with an R2 of 0.74 and 0.49, respectively (F=29.0 and 14.837, both p 0.05). Healthy participants showed predicted 1st vertical peak knee JRF of -0.54 + 0.10 (quadriceps muscle force) + 0.20 (hamstring muscle force) + 3.03 (vertical COM velocity). In healthy participants, the predicted anterior peak knee JRF was 0.71 + 0.04 (quadriceps muscle force) - 0.01 (knee extension angle velocity).
Conclusion(s): The results suggest the need to carefully adjust PFR for each patient when using an AFO. Moreover, excessive assist of AFO may cause knee pain and deformity. Knee joint loading may be able to evaluate with a little information.
Implications: Our study findings can make a significant contribution when used as selection criteria for AFO function and for use in development of new orthoses.
Keywords: Ankle-foot orthosis, joint loading, musculoskeletal model
Funding acknowledgements: This research was based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization(NEDO).
Topic: Neurology: stroke; Musculoskeletal: lower limb; Human movement analysis
Ethics approval required: Yes
Institution: Prefectural University of Hiroshima
Ethics committee: the ethics committee of the Faculty of Health and Welfare
Ethics number: 15MH036
All authors, affiliations and abstracts have been published as submitted.
