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Kobayashi T.,Hong Kong Polytechnic University | Leung A.K.L.,Hong Kong Polytechnic University | Akazawa Y.,The Hyogo Institute of Assistive Technology | Hutchins S.W.,University of Salford
Gait and Posture | Year: 2011

Ankle-foot orthoses (AFOs) are commonly prescribed to improve gait. The stiffness of an AFO is central for successful prescription; however, the recommended level of stiffness is currently based on the experience of clinicians. Therefore, the aim of this study was to design an experimental AFO (EAFO) whose stiffness was adjustable using commercially available oil-damper joints, and to demonstrate its potential capability in investigating the effects of altering AFO stiffness on gait. The influence of the EAFO stiffness on ankle joint kinematics in sagittal plane was evaluated in 10 patients with stroke by altering the stiffness of its oil-damper- type orthotic ankle joints using the four levels pre-set and defined by the manufacturer in dorsi- and plantarflexion directions independently. The mean peak plantarflexion angle was reduced by 105%, showing a change from 8.18 (3.14) degrees of plantarflexion to 0.38 (4.17) degrees of dorsiflexion, whilst the mean peak dorsiflexion angle was reduced by 44%, showing a change from 11.46 (5.57) degrees of dorsiflexion to 6.47 (5.23) degrees of dorsiflexion by altering the EAFO stiffness. The EAFO would therefore serve as a convenient tool when investigating the influence of AFO stiffness on gait in both clinical and research settings. © 2011 Elsevier B.V. Source


Kobayashi T.,Hong Kong Polytechnic University | Leung A.K.L.,Hong Kong Polytechnic University | Akazawa Y.,The Hyogo Institute of Assistive Technology | Hutchins S.W.,University of Salford
Gait and Posture | Year: 2013

Ankle-foot orthoses (AFOs) can improve gait in patients with hemiplegia. However, it is anecdotally known that excessive plantarflexion resistance of an AFO could induce undesired knee flexion at early stance. The aim of this study was to systematically investigate the effect of varying the degrees of plantarflexion resistance of an AFO on knee flexion angles at early stance in five subjects with chronic stroke who demonstrated two clear knee flexion peaks at early stance and swing. Each subject wore an experimental AFO constructed with an oil-damper type ankle joint and was instructed to walk at their self-selected walking speed under five plantarflexion resistance conditions. The sagittal plane ankle and knee joint kinematics and gait speed were analyzed using a 3-D Motion Analysis System. A number of significant differences (P<0.005) in maximum knee flexion angles at early stance amongst different plantarflexion resistance conditions were revealed. The knee flexion angle was 23.80 (3.25) degrees under the free hinge joint condition (condition 1), while that was 26.09 (3.79) degrees under the largest resistance condition (condition 5). It was therefore demonstrated that increasing the plantarflexion resistance of an AFO would induce more knee flexion at early stance phase in patients with stroke. © 2012 Elsevier B.V. Source


Kobayashi T.,Hong Kong Polytechnic University | Leung A.K.L.,Hong Kong Polytechnic University | Akazawa Y.,The Hyogo Institute of Assistive Technology | Tanaka M.,Osaka University | Hutchins S.W.,University of Salford
Journal of Biomechanics | Year: 2010

Quantitative measurement of ankle joint stiffness following stroke could prove useful in monitoring the progress of a rehabilitation programme. The objective of this study was to design a manual device for use in the clinical setting. Manual measurement of spastic ankle joint stiffness has historically been conducted using hand-held dynamometers or alternative devices, but some difficulties have been reported in controlling the velocity applied to the ankle during the measurement. In this study, a manually operated device was constructed with a footplate, a torquemeter and a potentiometer. It was mechanically designed to rotate around an approximated axis of the ankle joint and to measure ankle joint angular position and its corresponding resistive torque. Two stroke hemiplegic subjects pariticapted in a pilot study. The results suggested that difficulty in controlling the applied velocity might be complemented by presenting torque data as a function of peak angular velocity in each stretching cycle. Moreover, the results demonstrated that the device could potentially apply a wide range of angular velocities and provide potentially useful clinical information. Quantitative data successfully acquired using this method included the approximate ankle angular position, where the velocity-dependent characteristics of stiffness was notably initiated and its corresponding torque and velocity. © 2010 Elsevier Ltd. Source


Naito H.,Osaka University | Akazawa Y.,Osaka University | Akazawa Y.,The Hyogo Institute of Assistive Technology | Miura A.,Osaka University | And 2 more authors.
Journal of Biomechanical Science and Engineering | Year: 2012

In this study, we proposed a method for estimating muscle length parameters on an individual basis from measured data based on a musculo-skeletal structure with a Hill-type muscle model. Passive joint moments of the ankle were measured for 4 healthy subjects in two different knee positions, i.e., in knee flexion and extension, using manual measurement apparatus. Estimation of muscle length parameters based on measurement data from each subject was performed using a two-dimensional musculo-skeletal model of the lower limb with a Hill-type muscle model. Predicted passive joint moment properties using the estimated parameters were consistent with measured data. The estimated length parameters of muscles differed between subjects depending on their passive joint moment properties. These observations suggest that the proposed estimation method is available to identify muscle length parameters required for a quantification of ankle joint function and the musclo-skeletal model analyses on an individual basis. © 2012 by JSME. Source

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