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ABSTRACT: 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.
Gait & posture 08/2012; · 2.58 Impact Factor
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ABSTRACT: A custom moulded ankle orthosis with hinged joints potentially offers a better control over the subtalar joint and the ankle joint during lateral cutting movements, due to total contact design and increase in material strength.
To test the above hypothesis by comparing it to three other available orthoses.
Repeated measures.
Eight subjects with a history of ankle sprains (Grade 2), and 11 subjects without such history performed lateral cutting movements in four test conditions: 1) non-orthotic, 2) custom-moulded ankle orthosis with hinges, 3) Sport-Stirrup, and 4) elastic ankle sleeve with plastic support. A VICON motion analysis system was used to study the motions at the ankle and subtalar joints.
The custom-moulded ankle orthosis significantly lowered the inversion angle at initial contact (p = 0.006) and the peak inversion angle (p = 0.000) during lateral cutting movements in comparison to non-orthotic condition, while the other two orthoses did not. The three orthoses did not affect the plantarflexion motions, which had been suggested by previous studies to be important in shock wave attenuation.
The custom-moulded ankle orthosis with hinges could better control inversion and thus expected to better prevent ankle sprain in lateral cutting movements.
Custom-moulded ankle orthoses are not commonly used in preventing ankle sprains. This study raises the awareness of the use of custom-moulded ankle orthoses which are expected to better prevent ankle sprains.
Prosthetics & Orthotics International 02/2012; 36(2):190-5. · 0.56 Impact Factor
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ABSTRACT: Ankle joint stiffness and its range of motion (ROM) are commonly assessed to determine the appropriate mechanical characteristics required in an effective ankle-foot orthosis (AFO) prescription. The aim of this technical note is to present the design of a manual device that enables their convenient measurement in the clinical setting and to demonstrate its reliability.
The manual device was designed with a torquemeter, a potentiometer, a steering wheel, a rotary plate, and a foot plate. The measurement of resistive torque at 0° (neutral), 5° (dorsiflexion) and 10° (dorsiflexion) ankle angular positions demonstrated the high reliability of the device with Intraclass Correlation Coefficient (ICC) (1,k) values over 0.97.
Quantitative measurement of ankle joint stiffness and ROM by this manual device would provide objective information that could potentially assist AFO prescriptions. A future study should investigate how to incorporate the measurement obtained from the device into the prescription of an AFO.
Prosthetics & Orthotics International 12/2011; 35(4):478-81. · 0.56 Impact Factor
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ABSTRACT: Ankle-foot orthoses (AFOs) designed and proposed to influence muscle tone are generally called as “tone-reducing” AFOs, “tone-inhibiting” AFOs, or “dynamic” AFOs. These orthoses were originally evolved from the use of plaster casts to influence the positive support reflex or tonic reflex, which were either triggered by pressing reflexogenous areas on the plantar surface of the foot or suppressed by offloading them. The effects of wearing AFOs to influence muscle tone have mainly been studied in patients with cerebral palsy, stroke, or head injury. Although different AFO designs exist, it seems that there is a lack of evidence to demonstrate that these AFOs can actually reduce or inhibit spastic muscle tone. This article specifically reviews the classification of patient groups recruited in previous studies, the design characteristics of AFOs, and the clinical and biomechanical effects reported. The results of this review suggested that the level of evidence for AFOs being able to influence muscle tone was very low. Therefore, further research with randomized controlled trials is required to investigate their clinical effects.
JPO Journal of Prosthetics and Orthotics 03/2011; 23(2):52-57.
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ABSTRACT: 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.
Gait & posture 03/2011; 33(4):721-3. · 2.58 Impact Factor
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ABSTRACT: To investigate the methodology using a manual ankle joint resistive torque measurement device to evaluate the contribution of the neural component of ankle joint resistive torque in patients with stroke.
Within-subject comparison to compare the ankle joint resistive torque between fast and slow stretching conditions.
Ten patients with stroke participated in this study. The incremental ratio of ankle joint resistive torque at the ankle angular position of 5degrees dorsiflexion under the fast stretching condition in comparison to the slow one was calculated in each patient.
A significant increase (p<0.01) in the ankle joint resistive torque was demonstrated under the fast stretching condition in comparison to the slow one in all patients and the mean ankle joint resistive torque was 4.6 (SD=1.7) Nm under the slow stretching condition, while it was 8.4 (SD=4.1) Nm under the fast stretching condition at the ankle angular position of 5 degrees dorsiflexion. The incremental ratio ranged from 9.4-139.3% among the patients.
The results of this study demonstrated the potential advantage of the device to evaluate the contribution of the neural component of ankle joint resistive torque.
Brain Injury 01/2011; 25(3):307-14. · 1.36 Impact Factor
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ABSTRACT: We performed this review to provide a clearer understanding of how to effectively measure ankle-foot orthosis (AFO) rigidity. This information is important to ensure appropriate orthotic intervention in the treatment of patients with pathological gait. The two main approaches to the investigation of AFO rigidity are (1) bench-testing analyses, in which an AFO is fixed or attached to a measurement device, and (2) functional analyses, in which measurements are taken while a subject is walking with an AFO in situ. This review summarizes and classifies the current state of knowledge of AFO rigidity testing methods. We analyzed the strengths and weaknesses of the methods in order to recommend the most reliable techniques to measure AFO rigidity. The information obtained from this review article would, therefore, benefit both clinicians and engineers involved in the application and design of AFOs.
The Journal of Rehabilitation Research and Development 01/2011; 48(5):565-76. · 1.78 Impact Factor
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ABSTRACT: The purpose of this study was to design a new automated stiffness measurement device which could perform a simultaneous measurement of both dorsi- and plantarflexion angles and the corresponding resistive torque around the rotational centre of an articulated ankle-foot orthosis (AAFO). This was achieved by controlling angular velocities and range of motion in the sagittal plane. The device consisted of a hydraulic servo fatigue testing machine, a torque meter, a potentiometer, a rotary plate and an upright supporter to enable an AAFO to be attached to the device via a surrogate shank. The accuracy of the device in reproducing the range of motion and angular velocity was within 4% and 1% respectively in the range of motion of 30° (15° plantarflexion to 15° dorsiflexion) at the angular velocity of 10°/s, while that in the measurement of AAFO torque was within 8% at the 0° position. The device should prove useful to assist an orthotist or a manufacturer to quantify the stiffness of an AAFO and inform its clinical use.
Prosthetics & Orthotics International 12/2010; 34(4):439-48. · 0.56 Impact Factor
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ABSTRACT: 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.
Journal of biomechanics 02/2010; 43(9):1831-4. · 2.66 Impact Factor
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ABSTRACT: Ankle-foot orthoses (AFOs) have been reported to have positive effects on the temporal-spatial parameters and kinematics and kinetics of gait in patients with stroke. The center of mass (COM) may be used to represent whole body movement and energy cost in gait, and therefore COM movement would also be positively influenced with use of an appropriate AFO.
To investigate the effect of AFOs on the sagittal plane displacement of the COM in patients with stroke hemiplegia.
Five male subjects with stroke hemiplegia participated in this pilot study. The trajectory of the COM in the sagittal plane, gait speed, bilateral step length, step width, and bilateral stance time were analyzed while participants ambulated under 2 test conditions: with an AFO or with footwear only. The height of the 2 peaks of the vertical displacement of the COM in a gait cycle was subsequently measured and normalized to body height. Statistical analyses were conducted using a nonparametric Friedman test.
Gait speed, bilateral step length, and the normalized peak height of the vertical COM trajectory during stance phase on the affected leg all revealed statistically significant increases (P < .05), and step width showed significant decreases (P < .05) under the AFO condition when compared to the footwear-only condition.
An AFO may influence the vertical displacement of the COM in patients with stroke hemiplegia. The results of this pilot study therefore suggested that vertical movement of COM could potentially serve as a useful parameter to evaluate the effect of an AFO.
Topics in Stroke Rehabilitation 19(4):338-44. · 0.95 Impact Factor
