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Locomotor adaptation to a powered ankle-foot orthosis depends on control method
Stephen M Cain, Keith E Gordon, Daniel P Ferris
Journal of NeuroEngineering and Rehabilitation , 2007, DOI: 10.1186/1743-0003-4-48
Abstract: Subjects walked on a treadmill for two thirty-minute sessions spaced three days apart under either footswitch control (n = 6) or myoelectric control (n = 6). We recorded lower limb electromyography (EMG), joint kinematics, and orthosis kinetics. We compared stance phase EMG amplitudes, correlation of joint angle patterns, and mechanical work performed by the powered orthosis between the two controllers over time.During steady state at the end of the second session, subjects using proportional myoelectric control had much lower soleus and gastrocnemius activation than the subjects using footswitch control. The substantial decrease in triceps surae recruitment allowed the proportional myoelectric control subjects to walk with ankle kinematics close to normal and reduce negative work performed by the orthosis. The footswitch control subjects walked with substantially perturbed ankle kinematics and performed more negative work with the orthosis.These results provide evidence that the choice of orthosis control method can greatly alter how humans adapt to powered orthosis assistance during walking. Specifically, proportional myoelectric control results in larger reductions in muscle activation and gait kinematics more similar to normal compared to footswitch control.Advancements in robotic technology have enabled several research groups around the world to build working robotic exoskeletons for assisting human locomotion [1-8]. The exoskeletons have a range of intended uses including enhancing human performance in healthy individuals, replacing motor capabilities in disabled individuals, and aiding in neurological rehabilitation. In each case, improvements in computer processing, energy efficiency, and sensors and actuators are allowing devices to far surpass previous expectations.In order for robotic exoskeletons to better assist humans, it is imperative to determine how humans respond to mechanical assistance given by exoskeletons. Most of the published research has fo
A pneumatically powered knee-ankle-foot orthosis (KAFO) with myoelectric activation and inhibition
Gregory S Sawicki, Daniel P Ferris
Journal of NeuroEngineering and Rehabilitation , 2009, DOI: 10.1186/1743-0003-6-23
Abstract: Three healthy males were fitted with custom KAFOs equipped with artificial pneumatic muscles to power ankle plantar flexion/dorsiflexion and knee extension/flexion. Subjects walked over ground at 1.25 m/s under four conditions without extensive practice: 1) without wearing the orthosis, 2) wearing the orthosis with artificial muscles turned off, 3) wearing the orthosis activated under direct proportional myoelectric control, and 4) wearing the orthosis activated under proportional myoelectric control with flexor inhibition produced by leg extensor muscle activation. We collected joint kinematics, ground reaction forces, electromyography, and orthosis kinetics.The KAFO produced ~22%–33% of the peak knee flexor moment, ~15%–33% of the peak extensor moment, ~42%–46% of the peak plantar flexor moment, and ~83%–129% of the peak dorsiflexor moment during normal walking. With flexor inhibition produced by leg extensor muscle activation, ankle (Pearson r-value = 0.74 ± 0.04) and knee ( r = 0.95 ± 0.04) joint kinematic profiles were more similar to the without orthosis condition compared to when there was no flexor inhibition (r = 0.49 ± 0.13 for ankle, p = 0.05, and r = 0.90 ± 0.03 for knee, p = 0.17).The proportional myoelectric control with flexor inhibition allowed for a more normal gait than direct proportional myoelectric control. The current orthosis design provided knee torques smaller than the ankle torques due to the trade-off in torque and range of motion that occurs with artificial pneumatic muscles. Future KAFO designs could incorporate cams, gears, or different actuators to transmit greater torque to the knee.Powered lower-limb orthoses (i.e. robotic exoskeletons) can be useful tools for assisting gait rehabilitation therapy and studying the neuromechanics and energetics of human locomotion [1-3]. A primary goal of these devices is to replace or restore a portion of the torque and/or mechanical work performed by the biological muscle-tendons acting at the joint
3DIMENSIONAL MODELING OF AN ANKLE FOOT ORTHOSIS FOR CLUBFOOT DEFORMITY  [cached]
Ranjitha Rebecca Jeevana,Vijayaragavanb E.,Angeline Kirubac
International Journal of Biomedical Research , 2013, DOI: 10.7439/ijbr.v2i3.90
Abstract: Clubfoot deformity is a congenital deformity which is also called as congenital talipes equino varus (CTEV). This foot deformity is well established from birth. The causes for this deformity are numerous, but the major cause happens to be abnormal intra-uterine fetal positing. The clinical presentation is a child walking on the lateral border of the foot. The foot appears to be club shaped. This primary skeletal deformity in turn leads to muscular deformities like, tightening of the muscles that are constitute the medial border of the foot. Treatment is initiated from birth; severe bone and muscular deformity require surgical correction. But non surgical management is the most preferred way of treatment. Serial casting and braces are the management in practice. But these methods tend to be very uncomfortable; in turn the child gets irritated. Ankle foot orthosis have been used to treat a variety of foot deformity, but its application in clubfoot is yet to be understood. This study concentrates on designing an ankle foot orthosis as an alternate option for the treatment of clubfoot. The orthosis is virtually modeled, instead of the traditional fabricating procedure. This study concludes by showing that virtual modeling can be a better advancement in the field of orthosis designing.
3DIMENSIONAL MODELING OF AN ANKLE FOOT ORTHOSIS FOR CLUBFOOT DEFORMITY  [cached]
Ranjitha Rebecca Jeevana,Vijayaragavanb E.,Angeline Kirubac
International Journal of Biomedical Research , 2011, DOI: 10.7439/ijbr.v2i3.90
Abstract: Clubfoot deformity is a congenital deformity which is also called as congenital talipes equino varus (CTEV). This foot deformity is well established from birth. The causes for this deformity are numerous, but the major cause happens to be abnormal intra-uterine fetal positing. The clinical presentation is a child walking on the lateral border of the foot. The foot appears to be club shaped. This primary skeletal deformity in turn leads to muscular deformities like, tightening of the muscles that are constitute the medial border of the foot. Treatment is initiated from birth; severe bone and muscular deformity require surgical correction. But non surgical management is the most preferred way of treatment. Serial casting and braces are the management in practice. But these methods tend to be very uncomfortable; in turn the child gets irritated. Ankle foot orthosis have been used to treat a variety of foot deformity, but its application in clubfoot is yet to be understood. This study concentrates on designing an ankle foot orthosis as an alternate option for the treatment of clubfoot. The orthosis is virtually modeled, instead of the traditional fabricating procedure. This study concludes by showing that virtual modeling can be a better advancement in the field of orthosis designing.
Embracing additive manufacture: implications for foot and ankle orthosis design
Scott Telfer, Jari Pallari, Javier Munguia, Kenny Dalgarno, Martin McGeough, Jim Woodburn
BMC Musculoskeletal Disorders , 2012, DOI: 10.1186/1471-2474-13-84
Abstract: Two novel devices, a foot orthosis (FO) designed to include adjustable elements to relieve pressure at the metatarsal heads, and an ankle foot orthosis (AFO) designed to have adjustable stiffness levels in the sagittal plane, were developed and fabricated using AM. The devices were then tested on a healthy participant to determine if the intended biomechanical modes of action were achieved.The adjustable, pressure relieving FO was found to be able to significantly reduce pressure under the targeted metatarsal heads. The AFO was shown to have distinct effects on ankle kinematics which could be varied by adjusting the stiffness level of the device.The results presented here demonstrate the potential design freedom made available by AM, and suggest that it may allow novel personalised orthotic devices to be produced which are beyond the current state of the art.
A pneumatic power harvesting ankle-foot orthosis to prevent foot-drop
Robin Chin, Elizabeth T Hsiao-Wecksler, Eric Loth, Géza Kogler, Scott D Manwaring, Serena N Tyson, K Alex Shorter, Joel N Gilmer
Journal of NeuroEngineering and Rehabilitation , 2009, DOI: 10.1186/1743-0003-6-19
Abstract: The PhAFO was constructed from a two-part (tibia and foot) carbon composite structure with an articulating ankle joint. Ankle motion control was accomplished through a cam-follower locking mechanism actuated via a pneumatic circuit connected to the bellow pump and embedded in the foam sole. Biomechanical performance of the prototype orthosis was assessed during multiple trials of treadmill walking of an able-bodied control subject (n = 1). Motion capture and pressure measurements were used to investigate the effect of the PhAFO on lower limb joint behavior and the capacity of the bellow pump to repeatedly generate the required pneumatic pressure for toe clearance.Toe clearance during swing was successfully achieved during all trials; average clearance 44 ± 5 mm. Free ankle motion was observed during stance and plantarflexion was blocked during swing. In addition, the bellow component repeatedly generated an average of 169 kPa per step of pressure during ten minutes of walking.This study demonstrated that fluid power could be harvested with a pneumatic circuit built into an AFO, and used to operate an actuated cam-lock mechanism that controls ankle-foot motion at specific periods of the gait cycle.Foot-drop is a condition where the foot does not effectively clear the ground due to weak or absent ankle dorsiflexors which results in a steppage-type gait pattern. Steppage gait is a compensatory walking pattern for foot-drop that is characterized by increased knee and hip flexion during the swing phase to insure that the toe clears the ground during walking. The cause of foot-drop can be neurological and/or muscular in origin due to a multitude of pathologies [1]. A common treatment intervention is the use of an ankle-foot orthosis (AFO) that supports the ankle and foot to preclude foot-drop. This study presents a novel self-contained power harvesting ankle-foot orthosis that controls the unwanted plantarflexion movements associated with foot-drop and permits free ankle
Techniques to measure rigidity of ankle-foot orthosis: A review  [PDF]
Toshiki Kobayashi, PhD,Aaron K. L. Leung, PhD,Stephen W. Hutchins, PhD
Journal of Rehabilitation Research and Development , 2011,
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.
Changes in joint kinematics in children with cerebral palsy while walking with and without a floor reaction ankle-foot orthosis
Lucareli, Paulo Roberto Garcia;Lima, Mário de Oliveira;Lucarelli, Juliane Gomes de Almeida;Lima, Fernanda Púpio Silva;
Clinics , 2007, DOI: 10.1590/S1807-59322007000100010
Abstract: introduction: the floor reaction ankle-foot orthosis is commonly prescribed in the attempt to decrease knee flexion during the stance phase in the cerebral palsy (cp) gait. reported information about this type of orthosis is insufficient. purpose: the purpose of this study was to determine the effect of clinically prescribed floor reaction ankle-foot orthosis on kinematic parameters of the hip, knee and ankle in the stance phase of the gait cycle, compared to barefoot walking on children with cerebral palsy. methods: a retrospective chart review of 2200 patients revealed that 71 patients (142 limbs) had a diagnosis of diplegia, with no contractures in hip, knee or ankle flexion. their average age was 12.2 ± 3.9. all of them were wearing clinically prescribed hinged floor reaction ankle-foot orthosis undergoing a three dimensional gait analysis. we divided the patients in three groups: group i, with limited extension (maximum knee extension less than 15o); group ii, with moderate limited extension (maximum knee extension between 15o and 30o) and group iii crouch (maximum knee extension in stance more than 30o). results: results indicate the parameters maximum knee extension and ankle dorsiflexion were significant in group ii e iii; no change was observed in group i. the maximum hip extension was not significant in all three groups. conclusion: when indicated to improve the extension of the knees and ankle in the stance of the cp patients floor reaction ankle-foot orthosis was effective.
A Study of Design and Implementation Techniques of Active Soft Orthotic Ankle Foot  [PDF]
Ganesh K. Yenurkar, Swapnili P. Karmore
International Journal of Advanced Computer Research , 2012,
Abstract: This paper reports on the mechanical design of anactive soft orthotic implementation for AFP,which is powered by the pneumatic artificialmuscles. Ankle foot orthosis makes aneuromuscular patient’s having gait pattern morerehabilitate like that of an unaffected person, butthe devices can also be associated withcompensations of their own. And some patientswith a normal gate pattern are not necessary forits functionality. In this paper our study focuseson the rehabilitation performance based on theankle foot orthotic device.
Role of three side support ankle–foot orthosis in improving the balance in children with spastic diplegic cerebral palsy
KA Olama, SMN El-Din, MB Ibrahem
Egyptian Journal of Medical Human Genetics , 2013,
Abstract: Cerebral palsy (CP) is a heterogeneous group of permanent, non-progressive motor disorders of movement and posture. Ankle–foot orthoses (AFOs) are frequently prescribed to correct skeletal misalignments in spastic CP. The present study aims to evaluate the effect of the three side support ankle–foot orthosis on standing balance of the spastic diplegic CP children. Thirty spastic diplegic CP children participated in this study from both sexes. They were divided randomly into two age and sex matched groups: (Group I: study group and Group II: control group). The degree of spasticity was evaluated by passive movement for both limbs, while the child was completely relaxed. The Biodex stability system, was used for the assessment of the dynamic postural control of all diplegic children. Also the system measures the subject’s ability to control the platform’s angle of tilt. The patient’s performance is noted as stability index which represents the variance of the platform displacement in degrees. Every patient in the study group was exercised on three side support ankle–foot orthosis for 30 min, three times weekly, for 6 months, also they received the same therapeutic exercise program which was given to the control group. The results revealed no significant difference as regards the pre-treatment mean values of all stability indices in both the control and the study groups (P< 0.05). However comparison between post-treatment mean values of all stability indices in both groups showed significant improvement in favor of the study group (p<0.05). In conclusion: Uses of the three side support ankle–foot orthosis in addition to physical exercise program is highly useful in rehabilitation of spastic diplegic cerebral palsy children as they enabled them to gain more balance control and postural reactions .
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